\input texinfo @c -*- Texinfo -*- @setfilename gpgme.info @settitle The `GnuPG Made Easy' Reference Manual @dircategory GNU Libraries @direntry * @acronym{GPGME}: (gpgme). Adding support for cryptography to your program. @end direntry @include version.texi @c Unify some of the indices. @syncodeindex tp fn @syncodeindex pg fn @ifinfo This file documents the @acronym{GPGME} library. This is Edition @value{EDITION}, last updated @value{UPDATED}, of @cite{The `GnuPG Made Easy' Reference Manual}, for Version @value{VERSION}. Copyright @copyright{} 2002 g10 Code GmbH. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being ``Free Software Needs Free Documentation'' and ``GNU Lesser General Public License'', the Front-Cover texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the section entitled ``GNU Free Documentation License''. @end ifinfo @iftex @shorttitlepage The `GnuPG Made Easy' Reference Manual @end iftex @titlepage @center @titlefont{The `GnuPG Made Easy'} @sp 1 @center @titlefont{Reference Manual} @sp 6 @center Edition @value{EDITION} @sp 1 @center last updated @value{UPDATED} @sp 1 @center for version @value{VERSION} @page @vskip 0pt plus 1filll Copyright @copyright{} 2002 g10 Code GmbH. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being ``Free Software Needs Free Documentation'' and ``GNU Lesser General Public License'', the Front-Cover texts being (a) (see below), and with the Back-Cover Texts being (b) (see below). A copy of the license is included in the section entitled ``GNU Free Documentation License''. @end titlepage @page @ifnottex @node Top @top Main Menu This is Edition @value{EDITION}, last updated @value{UPDATED}, of @cite{The `GnuPG Made Easy' Reference Manual}, for Version @value{VERSION} of the @acronym{GPGME} library. @end ifnottex @menu * Introduction:: How to use this manual. * Preparation:: What you should do before using the library. * Protocols and Engines:: Supported crypto protocols. * Algorithms:: Supported algorithms. * Error Handling:: Error numbers and their meanings. * Exchanging Data:: Passing data to and from @acronym{GPGME}. * Contexts:: Handling @acronym{GPGME} contexts. Appendices * Copying:: The GNU General Public License says how you can copy and share `GnuPG Made Easy'. * Free Documentation License:: This manual is under the GNU Free Documentation License. Indices * Concept Index:: Index of concepts and programs. * Function and Data Index:: Index of functions, variables and data types. @detailmenu --- The Detailed Node Listing --- Introduction * Getting Started:: Purpose of the manual, and how to use it. * Features:: Reasons to install and use @acronym{GPGME}. * Overview:: Basic architecture of the @acronym{GPGME} library. Preparation * Header:: What header file you need to include. * Building the Source:: Compiler options to be used. * Using Automake:: Compiler options to be used the easy way. * Library Version Check:: Getting and verifying the library version. * Multi Threading:: How @acronym{GPGME} can be used in an MT environment. Protocols and Engines * Engine Version Check:: Verifying the engine version. * Engine Information:: Obtaining more information about the engines. * OpenPGP:: Support for the OpenPGP protocol. * Cryptographic Message Syntax:: Support for the CMS. Algorithms * Public Key Algorithms:: A list of all public key algorithms. * Hash Algorithms:: A list of all hash algorithms. Error Handling * Error Values:: A list of all error values used. * Error Strings:: How to get a descriptive string from a value. Exchanging Data * Creating Data Buffers:: Creating new data buffers. * Destroying Data Buffers:: Releasing data buffers. * Manipulating Data Buffers:: Operations on data buffers. Creating Data Buffers * Memory Based Data Buffers:: Creating memory based data buffers. * File Based Data Buffers:: Creating file based data buffers. * Callback Based Data Buffers:: Creating callback based data buffers. Contexts * Creating Contexts:: Creating new @acronym{GPGME} contexts. * Destroying Contexts:: Releasing @acronym{GPGME} contexts. * Context Attributes:: Setting properties of a context. * Key Management:: Managing keys with @acronym{GPGME}. * Trust Item Management:: Managing trust items with @acronym{GPGME}. * Crypto Operations:: Using a context for cryptography. * Run Control:: Controlling how operations are run. Context Attributes * Protocol Selection:: Selecting the protocol used by a context. * ASCII Armor:: Requesting @acronym{ASCII} armored output. * Text Mode:: Choosing canonical text mode. * Included Certificates:: Including a number of certificates. * Key Listing Mode:: Selecting key listing mode. * Passphrase Callback:: Getting the passphrase from the user. * Progress Meter Callback:: Being informed about the progress. Key Management * Listing Keys:: Browsing the list of available keys. * Information About Keys:: Requesting detailed information about keys. * Key Signatures:: Listing the signatures on a key. * Manipulating Keys:: Operations on keys. * Generating Keys:: Creating new key pairs. * Exporting Keys:: Retrieving key data from the key ring. * Importing Keys:: Adding keys to the key ring. * Deleting Keys:: Removing keys from the key ring. Trust Item Management * Listing Trust Items:: Browsing the list of available trust items. * Information About Trust Items:: Requesting information about trust items. * Manipulating Trust Items:: Operations on trust items. Crypto Operations * Decrypt:: Decrypting a ciphertext. * Verify:: Verifying a signature. * Decrypt and Verify:: Decrypting a signed ciphertext. * Sign:: Creating a signature. * Encrypt:: Encrypting a plaintext. Sign * Selecting Signers:: How to choose the keys to sign with. * Creating a Signature:: How to create a signature. Encrypt * Encrypting a Plaintext:: How to encrypt a plaintext. Run Control * Waiting For Completion:: Waiting until an operation is completed. * Using External Event Loops:: Advanced control over what happens when. Using External Event Loops * I/O Callback Interface:: How I/O callbacks are registered. * Registering I/O Callbacks:: How to use I/O callbacks for a context. * I/O Callback Example:: An example how to use I/O callbacks. * I/O Callback Example GTK+:: How to integrate @acronym{GPGME} in GTK+. * I/O Callback Example GDK:: How to integrate @acronym{GPGME} in GDK. @end detailmenu @end menu @node Introduction @chapter Introduction `GnuPG Made Easy' (@acronym{GPGME}) is a C language library that allows to add support for cryptography to a program. It is designed to make access to crypto engines like GnuPG or GpgSM easier for applications. @acronym{GPGME} provides a high-level crypto API for encryption, decryption, signing, signature verification and key management. @acronym{GPGME} uses GnuPG and GpgSM as its backends to support OpenPGP and the Cryptographic Message Syntax (CMS). @menu * Getting Started:: Purpose of the manual, and how to use it. * Features:: Reasons to install and use @acronym{GPGME}. * Overview:: Basic architecture of the @acronym{GPGME} library. @end menu @node Getting Started @section Getting Started This manual documents the @acronym{GPGME} library programming interface. All functions and data types provided by the library are explained. The reader is assumed to possess basic knowledge about cryptography in general, and public key cryptography in particular. The underlying cryptographic engines that are used by the library are not explained, but where necessary, special features or requirements by an engine are mentioned as far as they are relevant to @acronym{GPGME} or its users. This manual can be used in several ways. If read from the beginning to the end, it gives a good introduction into the library and how it can be used in an application. Forward references are included where necessary. Later on, the manual can be used as a reference manual to get just the information needed about any particular interface of the library. Experienced programmers might want to start looking at the examples at the end of the manual, and then only read up those parts of the interface which are unclear. @node Features @section Features @acronym{GPGME} has a couple of advantages over other libraries doing a similar job, and over implementing support for GnuPG or other crypto engines into your application directly. @table @asis @item it's free software Anybody can use, modify, and redistribute it under the terms of the GNU General Public License (@pxref{Copying}). @item it's flexible @acronym{GPGME} provides transparent support for several cryptographic protocols by different engines. Currently, @acronym{GPGME} supports the OpenPGP protocol using GnuPG as the backend, and the Cryptographic Message Syntax using GpgSM as the backend. @item it's easy @acronym{GPGME} hides the differences between the protocols and engines from the programmer behind an easy-to-use interface. This way the programmer can focus on the other parts of the program, and still integrate strong cryptography in his application. Once support for @acronym{GPGME} has been added to a program, it is easy to add support for other crypto protocols once @acronym{GPGME} backends provide them. @end table @node Overview @section Overview @acronym{GPGME} provides a data abstraction that is used to pass data to the crypto engine, and receive returned data from it. Data can be read from memory or from files, but it can also be provided by a callback function. The actual cryptographic operations are always set within a context. A context provides configuration parameters that define the behaviour of all operations performed within it. Only one operation per context is allowed at any time, but when one operation is finished, you can run the next operation in the same context. There can be more than one context, and all can run different operations at the same time. Furthermore, @acronym{GPGME} has rich key management facilities including listing keys, querying their attributes, generating, importing, exporting and deleting keys, and acquiring information about the trust path. With some precautions, @acronym{GPGME} can be used in a multi-threaded environment, although it is not completely thread safe and thus needs the support of the application. @node Preparation @chapter Preparation To use @acronym{GPGME}, you have to perform some changes to your sources and the build system. The necessary changes are small and explained in the following sections. At the end of this chapter, it is described how the library is initialized, and how the requirements of the library are verified. @menu * Header:: What header file you need to include. * Building the Source:: Compiler options to be used. * Using Automake:: Compiler options to be used the easy way. * Library Version Check:: Getting and verifying the library version. * Multi Threading:: How @acronym{GPGME} can be used in an MT environment. @end menu @node Header @section Header @cindex header file @cindex include file All interfaces (data types and functions) of the library are defined in the header file `gpgme.h'. You must include this in all programs using the library, either directly or through some other header file, like this: @example #include @end example The name space of @acronym{GPGME} is @code{gpgme_*} for function names and data types and @code{GPGME_*} for other symbols. Symbols internal to @acronym{GPGME} take the form @code{_gpgme_*} and @code{_GPGME_*}. Because @acronym{GPGME} links to the Assuan library, linking to @acronym{GPGME} will also use the @code{assuan_*} and @code{_assuan_*} name space indirectly. @node Building the Source @section Building the Source @cindex compiler options @cindex compiler flags If you want to compile a source file including the `gpgme.h' header file, you must make sure that the compiler can find it in the directory hierarchy. This is accomplished by adding the path to the directory in which the header file is located to the compilers include file search path (via the @option{-I} option). However, the path to the include file is determined at the time the source is configured. To solve this problem, gpgme ships with a small helper program @command{gpgme-config} that knows about the path to the include file and other configuration options. The options that need to be added to the compiler invocation at compile time are output by the @option{--cflags} option to @command{gpgme-config}. The following example shows how it can be used at the command line: @example gcc -c foo.c `gpgme-config --cflags` @end example Adding the output of @samp{gpgme-config --cflags} to the compilers command line will ensure that the compiler can find the @acronym{GPGME} header file. A similar problem occurs when linking the program with the library. Again, the compiler has to find the library files. For this to work, the path to the library files has to be added to the library search path (via the @option{-L} option). For this, the option @option{--libs} to @command{gpgme-config} can be used. For convenience, this option also outputs all other options that are required to link the program with @acronym{GPGME} (in particular, the @samp{-lgpgme} option). The example shows how to link @file{foo.o} with the @acronym{GPGME} library to a program @command{foo}. @example gcc -o foo foo.o `gpgme-config --libs` @end example Of course you can also combine both examples to a single command by specifying both options to @command{gpgme-config}: @example gcc -o foo foo.c `gpgme-config --cflags --libs` @end example @node Using Automake @section Using Automake @cindex automake @cindex autoconf It is much easier if you use GNU Automake instead writing your own Makefiles. If you do that you don't have to worry about finding and invoking the @command{gpgme-config} script at all. @acronym{GPGME} provides an extension to Automake that does all the work for you. @c A simple macro for optional variables. @macro ovar{varname} @r{[}@var{\varname\}@r{]} @end macro @defmac AM_PATH_GPGME (@ovar{minimum-version}, @ovar{action-if-found}, @ovar{action-if-not-found}) Check whether @acronym{GPGME} (at least version @var{minimum-version}, if given) exists on the host system. If it is found, execute @var{action-if-found}, otherwise do @var{action-if-not-found}, if given. Additionally, the function defines @code{GPGME_CFLAGS} to the flags needed for compilation of the program to find the @file{gpgme.h} header file, and @code{GPGME_LIBS} to the linker flags needed to link the program to the @acronym{GPGME} library. @end defmac You can use the defined Autoconf variables like this in your @file{Makefile.am}: @example AM_CPPFLAGS = $(GPGME_CFLAGS) LDADD = $(GPGME_LIBS) @end example @node Library Version Check @section Library Version Check @cindex version check, of the library @deftypefun {const char *} gpgme_check_version (@w{const char *@var{required_version}}) The function @code{gpgme_check_version} has three purposes. It can be used to retrieve the version number of the library. In addition it can verify that the version number is higher than a certain required version number. In either case, the function initializes some sub-systems, and for this reason alone it must be invoked early in your program, before you make use of the other functions in @acronym{GPGME}. If @var{required_version} is @code{NULL}, the function returns a pointer to a statically allocated string containing the version number of the library. If @var{required_version} is not @code{NULL}, it should point to a string containing a version number, and the function checks that the version of the library is at least as high as the version number provided. In this case, the function returns a pointer to a statically allocated string containing the version number of the library. If @var{REQUIRED_VERSION} is not a valid version number, or if the version requirement is not met, the function returns @code{NULL}. If you use a version of a library that is backwards compatible with older releases, but contains additional interfaces which your program uses, this function provides a run-time check if the necessary features are provided by the installed version of the library. @end deftypefun @node Multi Threading @section Multi Threading @cindex thread-safeness @cindex multi-threading The @acronym{GPGME} library is not entirely thread-safe, but it can still be used in a multi-threaded environment if some care is taken. If the following requirements are met, there should be no race conditions to worry about: @itemize @bullet @item @acronym{GPGME} supports the thread libraries pthread and GNU Pth. The support for this has to be enabled at compile time. @acronym{GPGME} will automatically detect the location in which the thread libraries are installed and activate the support for them. Support for other thread libraries is very easy to add. Please contact us if you have the need. @item If you link your program dynamically to @acronym{GPGME} and your supported thread library, @acronym{GPGME} will automatically detect the presence of this library and activate its use. You must link to the thread library before linking to @acronym{GPGME}. If you link to both pthread and GNU Pth, @acronym{GPGME} will use the pthread support. This feature requires weak symbol support. @item If you link your program statically to @acronym{GPGME}, there is currently no easy way to make sure that @acronym{GPGME} detects the presence of the thread library. This will be solved in a future version. @item The function @code{gpgme_check_version} must be called before any other function in the library, because it initializes the thread support subsystem in @acronym{GPGME}. To achieve this in all generality, it is necessary to synchronize the call to this function with all other calls to functions in the library, using the synchronization mechanisms available in your thread library. Otherwise, specific compiler or CPU memory cache optimizations could lead to the situation where a thread is started and uses @acronym{GPGME} before the effects of the initialization are visible for this thread. It doesn't even suffice to call @code{gpgme_check_version} before creating this other thread@footnote{In SMP systems the new thread could be started on another CPU before the effects of the initialization are seen by that CPU's memory cache. Not doing proper synchronization here leads to the same problems the double-checked locking idiom has. You might find that if you don't do proper synchronization, it still works in most configurations. Don't let this fool you. Someday it might lead to subtle bugs when someone tries it on a DEC Alpha or an SMP machine.}. For example, if you are using POSIX threads, each thread that wants to call functions in @acronym{GPGME} could call the following function before any function in the library: @example #include void initialize_gpgme (void) @{ static int gpgme_init; static pthread_mutext_t gpgme_init_lock = PTHREAD_MUTEX_INITIALIZER; pthread_mutex_lock (&gpgme_init_lock); if (!gpgme_init) @{ gpgme_check_version (); gpgme_init = 1; @} pthread_mutex_unlock (&gpgme_init_lock); @} @end example @item Any @code{gpgme_data_t}, @code{gpgme_ctx_t} and @code{gpgme_recipients_t} object must only be accessed by one thread at a time. If multiple threads want to deal with the same object, the caller has to make sure that operations on that object are fully synchronized. @item Only one thread at any time is allowed to call @code{gpgme_wait}. If multiple threads call this function, the caller must make sure that all invocations are fully synchronized. It is safe to start asynchronous operations while a thread is running in gpgme_wait. @end itemize @node Protocols and Engines @chapter Protocols and Engines @cindex protocol @cindex engine @cindex crypto engine @cindex backend @cindex crypto backend @acronym{GPGME} supports several cryptographic protocols, however, it does not implement them. Rather it uses backends (also called engines) which implement the protocol. @acronym{GPGME} uses inter-process communication to pass data back and forth between the application and the backend, but the details of the communication protocol and invocation of the backends is completely hidden by the interface. All complexity is handled by @acronym{GPGME}. Where an exchange of information between the application and the backend is necessary, @acronym{GPGME} provides the necessary callback function hooks and further interfaces. @deftp {Data type} {enum gpgme_protocol_t} @tindex gpgme_protocol_t The @code{gpgme_protocol_t} type specifies the set of possible protocol values that are supported by @acronym{GPGME}. The following protocols are supported: @table @code @item GPGME_PROTOCOL_OpenPGP This specifies the OpenPGP protocol. @item GPGME_PROTOCOL_CMS This specifies the Cryptographic Message Syntax. @end table @end deftp @deftypefun const char *gpgme_get_protocol_name (@w{gpgme_protocol_t @var{protocol}}) The function @code{gpgme_get_protocol_name} returns a statically allocated string describing the protocol @var{protocol}, or @code{NULL} if the protocol number is not valid. @end deftypefun @menu * Engine Version Check:: Verifying the engine version. * Engine Information:: Obtaining more information about the engines. * OpenPGP:: Support for the OpenPGP protocol. * Cryptographic Message Syntax:: Support for the CMS. @end menu @node Engine Version Check @section Engine Version Check @cindex version check, of the engines @deftypefun gpgme_error_t gpgme_engine_check_version (@w{gpgme_protocol_t @var{protocol}}) The function @code{gpgme_engine_check_version} verifies that the engine implementing the protocol @var{PROTOCOL} is installed in the expected path and meets the version requirement of @acronym{GPGME}. This function returns @code{GPGME_No_Error} if the engine is available and @code{GPGME_Invalid_Engine} if it is not. @end deftypefun @node Engine Information @section Engine Information @cindex engine, information about @deftp {Data type} {gpgme_engine_info_t} @tindex gpgme_protocol_t The @code{gpgme_engine_info_t} type specifies a pointer to a structure describing a crypto backend engine. The structure contains the following elements: @table @code @item gpgme_engine_info_t next This is a pointer to the next engine info structure in the linked list, or @code{NULL} if this is the last element. @item gpgme_protocol_t protocol This is the protocol for which the crypo engine is used. You can convert this to a string with @code{gpgme_get_protocol_name} for printing. @item const char *file_name This is a string holding the file name of the executable of the crypto engine. Currently, it is never @code{NULL}, but using @code{NULL} is reserved for future use, so always check before you use it. @item const char *version This is a string containing the version number of the crypto engine. It might be @code{NULL} if the version number can not be determined, for example because the executable doesn't exist or is invalid. @item const char *req_version This is a string containing the minimum required version number of the crypto engine for @acronym{GPGME} to work correctly. This is the version number that @code{gpgme_engine_check_version} verifies against. Currently, it is never @code{NULL}, but using @code{NULL} is reserved for future use, so always check before you use it. @end table @end deftp @deftypefun gpgme_error_t gpgme_get_engine_info (gpgme_engine_info_t *info) The function @code{gpgme_get_engine_info} returns a linked list of engine info structures in @var{info}. Each info structure describes one configured crypto backend engine. The memory for the info structures is allocated the first time this function is invoked, and must not be freed by the caller. This function returns @code{GPGME_No_Error} if successful, and @code{GPGME_Out_Of_Core} if not enough memory is available for the operation. @end deftypefun Here is the example how you can provide more diagnostics if you receive an error message which indicates that the crypto engine is invalid. @example gpgme_ctx_t ctx; gpgme_error_t err; [...] if (err == GPGME_Invalid_Engine) @{ gpgme_engine_info_t info; err = gpgme_get_engine_info (&info); if (!err) @{ while (info && info->protocol != gpgme_get_protocol (ctx)) info = info->next; if (!info) fprintf (stderr, "GPGME compiled without support for protocol %s", gpgme_get_protocol_name (info->protocol)); else if (info->path && !info->version) fprintf (stderr, "Engine %s not installed properly", info->path); else if (info->path && info->version && info->req_version) fprintf (stderr, "Engine %s version %s installed, " "but at least version %s required", info->path, info->version, info->req_version); else fprintf (stderr, "Unknown problem with engine for protocol %s", gpgme_get_protocol_name (info->protocol)); @} @} @end example @node OpenPGP @section OpenPGP @cindex OpenPGP @cindex GnuPG @cindex protocol, GnuPG @cindex engine, GnuPG OpenPGP is implemented by GnuPG, the @acronym{GNU} Privacy Guard. This is the first protocol that was supported by @acronym{GPGME}. The OpenPGP protocol is specified by @code{GPGME_PROTOCOL_OpenPGP}. @node Cryptographic Message Syntax @section Cryptographic Message Syntax @cindex CMS @cindex cryptographic message syntax @cindex GpgSM @cindex protocol, CMS @cindex engine, GpgSM @cindex S/MIME @cindex protocol, S/MIME @acronym{CMS} is implemented by GpgSM, the S/MIME implementation for GnuPG. The @acronym{CMS} protocol is specified by @code{GPGME_PROTOCOL_CMS}. @node Algorithms @chapter Algorithms @cindex algorithms The crypto backends support a variety of algorithms used in public key cryptography. The following sections list the identifiers used to denote such an algorithm. @menu * Public Key Algorithms:: A list of all public key algorithms. * Hash Algorithms:: A list of all hash algorithms. @end menu @node Public Key Algorithms @section Public Key Algorithms @cindex algorithms, public key @cindex public key algorithms Public key algorithms are used for encryption, decryption, signing and verification of signatures. @deftp {Data type} {enum gpgme_pubkey_algo_t} @tindex gpgme_pubkey_algo_t The @code{gpgme_pubkey_algo_t} type specifies the set of all public key algorithms that are supported by @acronym{GPGME}. Possible values are: @table @code @item GPGME_PK_RSA This value indicates the RSA (Rivest, Shamir, Adleman) algorithm. @item GPGME_PK_RSA_E Deprecated. This value indicates the RSA (Rivest, Shamir, Adleman) algorithm for encryption and decryption only. @item GPGME_PK_RSA_S Deprecated. This value indicates the RSA (Rivest, Shamir, Adleman) algorithm for signing and verification only. @item GPGME_PK_DSA This value indicates DSA, the Digital Signature Algorithm. @item GPGME_PK_ELG This value indicates ElGamal. @item GPGME_PK_ELG_E This value also indicates ElGamal and is used specifically in GnuPG. @end table @end deftp @deftypefun {const char *} gpgme_pubkey_algo_name (@w{gpgme_pubkey_algo_t @var{algo}}) The function @code{gpgme_pubkey_algo_name} returns a pointer to a statically allocated string containing a description of the public key algorithm @var{algo}. This string can be used to output the name of the public key algorithm to the user. If @var{algo} is not a valid public key algorithm, @code{NULL} is returned. @end deftypefun @node Hash Algorithms @section Hash Algorithms @cindex algorithms, hash @cindex algorithms, message digest @cindex hash algorithms @cindex message digest algorithms Hash (message digest) algorithms are used to compress a long message to make it suitable for public key cryptography. @deftp {Data type} {enum gpgme_hash_algo_t} @tindex gpgme_hash_algo_t The @code{gpgme_hash_algo_t} type specifies the set of all hash algorithms that are supported by @acronym{GPGME}. Possible values are: @table @code @item GPGME_MD_MD5 @item GPGME_MD_SHA1 @item GPGME_MD_RMD160 @item GPGME_MD_MD2 @item GPGME_MD_TIGER @item GPGME_MD_HAVAL @item GPGME_MD_SHA256 @item GPGME_MD_SHA384 @item GPGME_MD_SHA512 @item GPGME_MD_MD4 @item GPGME_MD_CRC32 @item GPGME_MD_CRC32_RFC1510 @item GPGME_MD_CRC24_RFC2440 @end table @end deftp @deftypefun {const char *} gpgme_hash_algo_name (@w{gpgme_hash_algo_t @var{algo}}) The function @code{gpgme_hash_algo_name} returns a pointer to a statically allocated string containing a description of the hash algorithm @var{algo}. This string can be used to output the name of the hash algorithm to the user. If @var{algo} is not a valid hash algorithm, @code{NULL} is returned. @end deftypefun @node Error Handling @chapter Error Handling @cindex error handling Many functions in @acronym{GPGME} can return an error if they fail. For this reason, the application should always catch the error condition and take appropriate measures, for example by releasing the resources and passing the error up to the caller, or by displaying a descriptive message to the user and cancelling the operation. Some error values do not indicate a system error or an error in the operation, but the result of an operation that failed properly. For example, if you try to decrypt a tempered message, the decryption will fail. Another error value actually means that the end of a data buffer or list has been reached. The following descriptions explain what each error message means in general. Some error values have specific meanings if returned by a specific function. Such cases are described in the documentation of those functions. @menu * Error Values:: A list of all error values used. * Error Strings:: How to get a descriptive string from a value. @end menu @node Error Values @section Error Values @cindex error values, list of @deftp {Data type} {enum gpgme_error_t} @tindex gpgme_error_t The @code{gpgme_error_t} type specifies the set of all error values that are used by @acronym{GPGME}. Possible values are: @table @code @item GPGME_EOF This value indicates the end of a list, buffer or file. @item GPGME_No_Error This value indicates success. The value of this error is @code{0}. @item GPGME_General_Error This value means that something went wrong, but either there is not enough information about the problem to return a more useful error value, or there is no separate error value for this type of problem. @item GPGME_Out_Of_Core This value means that an out-of-memory condition occurred. @item GPGME_Invalid_Value This value means that some user provided data was out of range. This can also refer to objects. For example, if an empty @code{gpgme_data_t} object was expected, but one containing data was provided, this error value is returned. @item GPGME_Exec_Error This value means that an error occurred when trying to spawn a child process. @item GPGME_Too_Many_Procs This value means that there are too many active backend processes. @item GPGME_Pipe_Error This value means that the creation of a pipe failed. @item GPGME_No_UserID This value means that no valid recipients for a message have been set. @item GPGME_Invalid_UserID This value means that some, but not all, recipients for a message have been invalid. @item GPGME_No_Data This value means that a @code{gpgme_data_t} object which was expected to have content was found empty. @item GPGME_Conflict This value means that a conflict of some sort occurred. @item GPGME_Not_Implemented This value indicates that the specific function (or operation) is not implemented. This error should never happen. It can only occur if you use certain values or configuration options which do not work, but for which we think that they should work at some later time. @item GPGME_Read_Error This value means that an I/O read operation failed. @item GPGME_Write_Error This value means that an I/O write operation failed. @item GPGME_File_Error This value means that a file I/O operation failed. The value of @var{errno} contains the system error value. @item GPGME_Decryption_Failed This value indicates that a decryption operation was unsuccessful. @item GPGME_Bad_Passphrase This value means that the user did not provide a correct passphrase when requested. @item GPGME_Canceled This value means that the operation was canceled. @item GPGME_Invalid_Key This value means that a key was invalid. @item GPGME_Invalid_Engine This value means that the engine that implements the desired protocol is currently not available. This can either be because the sources were configured to exclude support for this engine, or because the engine is not installed properly. @item GPGME_Unknown_Reason This value indicates that a user ID was invalid but the exact reason is not specified. @item GPGME_Not_Found This value indicates that a user ID was not found. @item GPGME_Ambiguous_Specification This value indicates that a user ID did not specify a unique key. @item GPGME_Wrong_Key_Usage This value indicates that a key is not used appropriately. @item GPGME_Key_Revoked This value indicates that a key was revoced. @item GPGME_Key_Expired This value indicates that a key was expired. @item GPGME_No_CRL_Known This value indicates that no certificate revocation list is known for the certificate. @item GPGME_Policy_Mismatch This value indicates that a policy issue occured. @item GPGME_No_Secret_Key This value indicates that no secret key for the user ID is available. @item GPGME_Key_Not_Trusted This value indicates that the key with the user ID is not trusted. @item GPGME_Issuer_Missing This value indicates that a key could not be imported because there is no issuer @item GPGME_Chain_Too_Long This value indicates that a key could not be imported because its certificate chain is too long. @item GPGME_Unsupported_Algorithm This value means a verification failed because the cryptographic algorithm is not supported by the crypto backend. @item GPGME_Sig_Expired This value means a verification failed because the signature expired. @item GPGME_Bad_Signature This value means a verification failed because the signature is bad. @item GPGME_No_Public_Key This value means a verification failed because the public key is not available. @end table @end deftp @node Error Strings @section Error Strings @cindex error values, printing of @cindex error strings @deftypefun {const char *} gpgme_strerror (@w{gpgme_error_t @var{err}}) The function @code{gpgme_strerror} returns a pointer to a statically allocated string containing a description of the error with the error value @var{err}. This string can be used to output a diagnostic message to the user. The following example illustrates the use of @code{gpgme_strerror}: @example gpgme_ctx_t ctx; gpgme_error_t err = gpgme_new (&ctx); if (err) @{ fprintf (stderr, "%s: creating GpgME context failed: %s\n", argv[0], gpgme_strerror (err)); exit (1); @} @end example @end deftypefun @node Exchanging Data @chapter Exchanging Data @cindex data, exchanging A lot of data has to be exchanged between the user and the crypto engine, like plaintext messages, ciphertext, signatures and information about the keys. The technical details about exchanging the data information are completely abstracted by @acronym{GPGME}. The user provides and receives the data via @code{gpgme_data_t} objects, regardless of the communication protocol between @acronym{GPGME} and the crypto engine in use. @deftp {Data type} {gpgme_data_t} The @code{gpgme_data_t} type is a handle for a container for generic data, which is used by @acronym{GPGME} to exchange data with the user. @end deftp @menu * Creating Data Buffers:: Creating new data buffers. * Destroying Data Buffers:: Releasing data buffers. * Manipulating Data Buffers:: Operations on data buffers. @end menu @node Creating Data Buffers @section Creating Data Buffers @cindex data buffer, creation Data objects can be based on memory, files, or callback functions provided by the user. Not all operations are supported by all objects. @menu * Memory Based Data Buffers:: Creating memory based data buffers. * File Based Data Buffers:: Creating file based data buffers. * Callback Based Data Buffers:: Creating callback based data buffers. @end menu @node Memory Based Data Buffers @subsection Memory Based Data Buffers Memory based data objects store all data in allocated memory. This is convenient, but only practical for an amount of data that is a fraction of the available physical memory. The data has to be copied from its source and to its destination, which can often be avoided by using one of the other data object @deftypefun gpgme_error_t gpgme_data_new (@w{gpgme_data_t *@var{dh}}) The function @code{gpgme_data_new} creates a new @code{gpgme_data_t} object and returns a handle for it in @var{dh}. The data object is memory based and initially empty. The function returns @code{GPGME_No_Error} if the data object was successfully created, @code{GPGME_Invalid_Value} if @var{dh} is not a valid pointer, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @deftypefun gpgme_error_t gpgme_data_new_from_mem (@w{gpgme_data_t *@var{dh}}, @w{const char *@var{buffer}}, @w{size_t @var{size}}, @w{int @var{copy}}) The function @code{gpgme_data_new_from_mem} creates a new @code{gpgme_data_t} object and fills it with @var{size} bytes starting from @var{buffer}. If @var{copy} is not zero, a private copy of the data is made. If @var{copy} is zero, the data is taken from the specified buffer as needed, and the user has to ensure that the buffer remains valid for the whole life span of the data object. The function returns @code{GPGME_No_Error} if the data object was successfully created, @code{GPGME_Invalid_Value} if @var{dh} or @var{buffer} is not a valid pointer, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @deftypefun gpgme_error_t gpgme_data_new_from_file (@w{gpgme_data_t *@var{dh}}, @w{const char *@var{filename}}, @w{int @var{copy}}) The function @code{gpgme_data_new_from_file} creates a new @code{gpgme_data_t} object and fills it with the content of the file @var{filename}. If @var{copy} is not zero, the whole file is read in at initialization time and the file is not used anymore after that. This is the only mode supported currently. Later, a value of zero for @var{copy} might cause all reads to be delayed until the data is needed, but this is not yet implemented. The function returns @code{GPGME_No_Error} if the data object was successfully created, @code{GPGME_Invalid_Value} if @var{dh} or @var{filename} is not a valid pointer, @code{GPGME_File_Error} if an I/O operation fails, @code{GPGME_Not_Implemented} if @var{code} is zero, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @deftypefun gpgme_error_t gpgme_data_new_from_filepart (@w{gpgme_data_t *@var{dh}}, @w{const char *@var{filename}}, @w{FILE *@var{fp}}, @w{off_t @var{offset}}, @w{size_t @var{length}}) The function @code{gpgme_data_new_from_filepart} creates a new @code{gpgme_data_t} object and fills it with a part of the file specified by @var{filename} or @var{fp}. Exactly one of @var{filename} and @var{fp} must be non-zero, the other must be zero. The argument that is not zero specifies the file from which @var{length} bytes are read into the data object, starting from @var{offset}. The function returns @code{GPGME_No_Error} if the data object was successfully created, @code{GPGME_Invalid_Value} if @var{dh} and exactly one of @var{filename} and @var{fp} is not a valid pointer, @code{GPGME_File_Error} if an I/O operation fails, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @node File Based Data Buffers @subsection File Based Data Buffers File based data objects operate directly on file descriptors or streams. Only a small amount of data is stored in core at any time, so the size of the data objects is not limited by @acronym{GPGME}. @deftypefun gpgme_error_t gpgme_data_new_from_fd (@w{gpgme_data_t *@var{dh}}, @w{int @var{fd}}) The function @code{gpgme_data_new_from_fd} creates a new @code{gpgme_data_t} object and uses the file descriptor @var{fd} to read from (if used as an input data object) and write to (if used as an output data object). When using the data object as an input buffer, the function might read a bit more from the file descriptor than is actually needed by the crypto engine in the desired operation because of internal buffering. The function returns @code{GPGME_No_Error} if the data object was successfully created, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @deftypefun gpgme_error_t gpgme_data_new_from_stream (@w{gpgme_data_t *@var{dh}}, @w{FILE *@var{stream}}) The function @code{gpgme_data_new_from_stream} creates a new @code{gpgme_data_t} object and uses the I/O stream @var{stream} to read from (if used as an input data object) and write to (if used as an output data object). When using the data object as an input buffer, the function might read a bit more from the stream than is actually needed by the crypto engine in the desired operation because of internal buffering. The function returns @code{GPGME_No_Error} if the data object was successfully created, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @node Callback Based Data Buffers @subsection Callback Based Data Buffers If neither memory nor file based data objects are a good fit for your application, you can implement the functions a data object provides yourself and create a data object from these callback functions. @deftp {Data type} {ssize_t (*gpgme_data_read_cb_t) (@w{void *@var{handle}}, @w{void @var{*buffer}}, @w{size_t @var{size}})} @tindex gpgme_data_read_cb_t The @code{gpgme_data_read_cb_t} type is the type of functions which @acronym{GPGME} calls if it wants to read data from a user-implemented data object. The function should read up to @var{size} bytes from the current read position into the space starting at @var{buffer}. The @var{handle} is provided by the user at data object creation time. The function should return the number of bytes read, 0 on EOF, and -1 on error. If an error occurs, @var{errno} should be set to describe the type of the error. @end deftp @deftp {Data type} {ssize_t (*gpgme_data_write_cb_t) (@w{void *@var{handle}}, @w{const void @var{*buffer}}, @w{size_t @var{size}})} @tindex gpgme_data_write_cb_t The @code{gpgme_data_write_cb_t} type is the type of functions which @acronym{GPGME} calls if it wants to write data to a user-implemented data object. The function should write up to @var{size} bytes to the current write position from the space starting at @var{buffer}. The @var{handle} is provided by the user at data object creation time. The function should return the number of bytes written, and -1 on error. If an error occurs, @var{errno} should be set to describe the type of the error. @end deftp @deftp {Data type} {off_t (*gpgme_data_seek_cb_t) (@w{void *@var{handle}}, @w{off_t @var{offset}}, @w{int @var{whence}})} @tindex gpgme_data_seek_cb_t The @code{gpgme_data_seek_cb_t} type is the type of functions which @acronym{GPGME} calls if it wants to change the current read/write position in a user-implemented data object, just like the @code{lseek} function. The function should return the new read/write position, and -1 on error. If an error occurs, @var{errno} should be set to describe the type of the error. @end deftp @deftp {Data type} {void (*gpgme_data_release_cb_t) (@w{void *@var{handle}})} @tindex gpgme_data_release_cb_t The @code{gpgme_data_release_cb_t} type is the type of functions which @acronym{GPGME} calls if it wants to destroy a user-implemented data object. The @var{handle} is provided by the user at data object creation time. @end deftp @deftp {Data type} {struct gpgme_data_cbs} This structure is used to store the data callback interface functions described above. It has the following members: @table @code @item gpgme_data_read_cb_t read This is the function called by @acronym{GPGME} to read data from the data object. It is only required for input data object. @item gpgme_data_write_cb_t write This is the function called by @acronym{GPGME} to write data to the data object. It is only required for output data object. @item gpgme_data_seek_cb_t seek This is the function called by @acronym{GPGME} to change the current read/write pointer in the data object (if available). It is optional. @item gpgme_data_release_cb_t release This is the function called by @acronym{GPGME} to release a data object. It is optional. @end table @end deftp @deftypefun gpgme_error_t gpgme_data_new_from_cbs (@w{gpgme_data_t *@var{dh}}, @w{gpgme_data_cbs_t @var{cbs}}, @w{void *@var{handle}}) The function @code{gpgme_data_new_from_cbs} creates a new @code{gpgme_data_t} object and uses the user-provided callback functions to operate on the data object. The handle @var{handle} is passed as first argument to the callback functions. This can be used to identify this data object. The function returns @code{GPGME_No_Error} if the data object was successfully created, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun The following interface is deprecated and only provided for backward compatibility. Don't use it. It will be removed in a future version of @acronym{GPGME}. @deftypefun gpgme_error_t gpgme_data_new_with_read_cb (@w{gpgme_data_t *@var{dh}}, @w{int (*@var{readfunc})} (@w{void *@var{hook}}, @w{char *@var{buffer}}, @w{size_t @var{count}}, @w{size_t *@var{nread}}), @w{void *@var{hook_value}}) The function @code{gpgme_data_new_with_read_cb} creates a new @code{gpgme_data_t} object and uses the callback function @var{readfunc} to retrieve the data on demand. As the callback function can supply the data in any way it wants, this is the most flexible data type @acronym{GPGME} provides. However, it can not be used to write data. The callback function receives @var{hook_value} as its first argument whenever it is invoked. It should return up to @var{count} bytes in @var{buffer}, and return the number of bytes actually read in @var{nread}. It may return @code{0} in @var{nread} if no data is currently available. To indicate @code{EOF} the function should return with an error code of @code{-1} and set @var{nread} to @code{0}. The callback function may support to reset its internal read pointer if it is invoked with @var{buffer} and @var{nread} being @code{NULL} and @var{count} being @code{0}. The function returns @code{GPGME_No_Error} if the data object was successfully created, @code{GPGME_Invalid_Value} if @var{dh} or @var{readfunc} is not a valid pointer, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @node Destroying Data Buffers @section Destroying Data Buffers @cindex data buffer, destruction @deftypefun void gpgme_data_release (@w{gpgme_data_t @var{dh}}) The function @code{gpgme_data_release} destroys the data object with the handle @var{dh}. It releases all associated resources that were not provided by the user in the first place. @end deftypefun @deftypefun {char *} gpgme_data_release_and_get_mem (@w{gpgme_data_t @var{dh}}, @w{size_t *@var{length}}) The function @code{gpgme_data_release_and_get_mem} is like @code{gpgme_data_release}, except that it returns the data buffer and its length that was provided by the object. The user has to release the buffer with @code{free}. In case the user provided the data buffer in non-copy mode, a copy will be made for this purpose. In case an error returns, or there is no suitable data buffer that can be returned to the user, the function will return @code{NULL}. @end deftypefun @node Manipulating Data Buffers @section Manipulating Data Buffers @cindex data buffere, manipulation @deftypefun ssize_t gpgme_data_read (@w{gpgme_data_t @var{dh}}, @w{void *@var{buffer}}, @w{size_t @var{length}}) The function @code{gpgme_data_read} reads up to @var{length} bytes from the data object with the handle @var{dh} into the space starting at @var{buffer}. If no error occurs, the actual amount read is returned. If the end of the data object is reached, the function returns @code{GPGME_EOF} and sets @var{nread} to zero. In all other cases, the function returns -1 and sets @var{errno}. @end deftypefun @deftypefun ssize_t gpgme_data_write (@w{gpgme_data_t @var{dh}}, @w{const void *@var{buffer}}, @w{size_t @var{size}}) The function @code{gpgme_data_write} writes up to @var{size} bytes starting from @var{buffer} into the data object with the handle @var{dh} at the current write position. The function returns the number of bytes actually written, or -1 if an error occurs. If an error occurs, @var{errno} is set. @end deftypefun /* Set the current position from where the next read or write starts in the data object with the handle DH to OFFSET, relativ to WHENCE. */ off_t gpgme_data_seek (gpgme_data_t dh, off_t offset, int whence); @deftypefun off_t gpgme_data_seek (@w{gpgme_data_t @var{dh}}, @w{off_t *@var{offset}}, @w{int @var{whence}}) The function @code{gpgme_data_seek} changes the current read/write position. The @var{whence} argument specifies how the @var{offset} should be interpreted. It must be one of the following symbolic constants: @table @code @item SEEK_SET Specifies that @var{whence} is a count of characters from the beginning of the data object. @item SEEK_CUR Specifies that @var{whence} is a count of characters from the current file position. This count may be positive or negative. @item SEEK_END Specifies that @var{whence} is a count of characters from the end of the data object. A negative count specifies a position within the current extent of the data object; a positive count specifies a position past the current end. If you set the position past the current end, and actually write data, you will extend the data object with zeros up to that position. @end table If successful, the function returns the resulting file position, measured in bytes from the beginning of the data object. You can use this feature together with @code{SEEK_CUR} to read the current read/write position. If the function fails, -1 is returned and @var{errno} is set. @end deftypefun The following function is deprecated and should not be used. It will be removed in a future version of @acronym{GPGME}. @deftypefun gpgme_error_t gpgme_data_rewind (@w{gpgme_data_t @var{dh}}) The function @code{gpgme_data_rewind} is equivalent to: @example return (gpgme_data_seek (dh, 0, SEEK_SET) == -1) ? mk_error (File_Error) : 0; @end example @end deftypefun @c @c gpgme_data_encoding_t @c @deftp {Data type} {enum gpgme_data_encoding_t} @tindex gpgme_data_encoding_t The @code{gpgme_data_encoding_t} type specifies the encoding of a @code{gpgme_data_t} object. This encoding is useful to give the backend a hint on the type of data. The following data types are available: @table @code @item GPGME_DATA_ENCODING_NONE This specifies that the encoding is not known. This is the default for a new data object. The backend will try its best to detect the encoding automatically. @item GPGME_DATA_ENCODING_BINARY This specifies that the data is encoding in binary form; i.e. there is no special encoding. @item GPGME_DATA_ENCODING_BASE64 This specifies that the data is encoded using the Base-64 encoding scheme as used by @acronym{MIME} and other protocols. @item GPGME_DATA_ENCODING_ARMOR This specifies that the data is encoded in an armored form as used by OpenPGP and PEM. @end table @end deftp @deftypefun gpgme_data_encoding_t gpgme_data_get_encoding (@w{gpgme_data_t @var{dh}}) The function @code{gpgme_data_get_encoding} returns the encoding of the data object with the handle @var{dh}. If @var{dh} is not a valid pointer (e.g. @code{NULL}) @code{GPGME_DATA_ENCODING_NONE} is returned. @end deftypefun @deftypefun gpgme_error_t gpgme_data_set_encoding (@w{gpgme_data_t @var{dh}, gpgme_data_encoding_t @var{enc}}) The function @code{gpgme_data_set_encoding} changes the encoding of the data object with the handle @var{dh} to @var{enc}. @end deftypefun @c @c Chapter Contexts @c @node Contexts @chapter Contexts @cindex context All cryptographic operations in @acronym{GPGME} are performed within a context, which contains the internal state of the operation as well as configuration parameters. By using several contexts you can run several cryptographic operations in parallel, with different configuration. @deftp {Data type} {gpgme_ctx_t} The @code{gpgme_ctx_t} type is a handle for a @acronym{GPGME} context, which is used to hold the configuration, status and result of cryptographic operations. @end deftp @menu * Creating Contexts:: Creating new @acronym{GPGME} contexts. * Destroying Contexts:: Releasing @acronym{GPGME} contexts. * Context Attributes:: Setting properties of a context. * Key Management:: Managing keys with @acronym{GPGME}. * Trust Item Management:: Managing trust items with @acronym{GPGME}. * Crypto Operations:: Using a context for cryptography. * Run Control:: Controlling how operations are run. @end menu @node Creating Contexts @section Creating Contexts @cindex context, creation @deftypefun gpgme_error_t gpgme_new (@w{gpgme_ctx_t *@var{ctx}}) The function @code{gpgme_data_new} creates a new @code{gpgme_ctx_t} object and returns a handle for it in @var{ctx}. The function returns @code{GPGME_No_Error} if the context was successfully created, @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer, and @code{GPGME_Out_Of_Core} if not enough memory is available. @end deftypefun @node Destroying Contexts @section Destroying Contexts @cindex context, destruction @deftypefun void gpgme_release (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_release} destroys the context with the handle @var{ctx} and releases all associated resources. @end deftypefun @node Context Attributes @section Context Attributes @cindex context, attributes @menu * Protocol Selection:: Selecting the protocol used by a context. * ASCII Armor:: Requesting @acronym{ASCII} armored output. * Text Mode:: Choosing canonical text mode. * Included Certificates:: Including a number of certificates. * Key Listing Mode:: Selecting key listing mode. * Passphrase Callback:: Getting the passphrase from the user. * Progress Meter Callback:: Being informed about the progress. @end menu @node Protocol Selection @subsection Protocol Selection @cindex context, selecting protocol @cindex protocol, selecting @deftypefun gpgme_error_t gpgme_set_protocol (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_protocol_t @var{proto}}) The function @code{gpgme_set_protocol} sets the protocol used within the context @var{ctx} to @var{proto}. All crypto operations will be performed by the crypto engine configured for that protocol. @xref{Protocols and Engines}. Setting the protocol with @code{gpgme_set_protocol} does not check if the crypto engine for that protocol is available and installed correctly. @xref{Engine Version Check}. The function returns @code{GPGME_No_Error} if the protocol could be set successfully, and @code{GPGME_Invalid_Value} if @var{protocol} is not a valid protocol. @end deftypefun @deftypefun gpgme_protocol_t gpgme_get_protocol (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_get_protocol} retrieves the protocol currently use with the context @var{ctx}. @end deftypefun @c FIXME: Unfortunately, using @acronym here breaks texi2dvi. @node ASCII Armor @subsection @acronym{ASCII} Armor @cindex context, armor mode @cindex @acronym{ASCII} armor @cindex armor mode @deftypefun void gpgme_set_armor (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{yes}}) The function @code{gpgme_set_armor} specifies if the output should be @acronym{ASCII} armored. By default, output is not @acronym{ASCII} armored. @acronym{ASCII} armored output is disabled if @var{yes} is zero, and enabled otherwise. @end deftypefun @deftypefun int gpgme_get_armor (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_get_armor} returns 1 if the output is @acronym{ASCII} armored, and @code{0} if it is not, or if @var{ctx} is not a valid pointer. @end deftypefun @node Text Mode @subsection Text Mode @cindex context, text mode @cindex text mode @cindex canonical text mode @deftypefun void gpgme_set_textmode (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{yes}}) The function @code{gpgme_set_textmode} specifies if canonical text mode should be used. By default, text mode is not used. Text mode is for example used for the RFC2015 signatures; note that the updated RFC 3156 mandates that the mail user agent does some preparations so that text mode is not needed anymore. This option is only relevant to the OpenPGP crypto engine, and ignored by all other engines. Canonical text mode is disabled if @var{yes} is zero, and enabled otherwise. @end deftypefun @deftypefun int gpgme_get_textmode (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_get_textmode} returns 1 if canonical text mode is enabled, and @code{0} if it is not, or if @var{ctx} is not a valid pointer. @end deftypefun @node Included Certificates @subsection Included Certificates @cindex certificates, included @deftypefun void gpgme_set_include_certs (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{nr_of_certs}}) The function @code{gpgme_set_include_certs} specifies how many certificates should be included in an S/MIME signed message. By default, only the sender's certificate is included. The possible values of @var{nr_of_certs} are: @table @code @item -2 Include all certificates except the root certificate. @item -1 Include all certificates. @item 0 Include no certificates. @item 1 Include the sender's certificate only. @item n Include the first n certificates of the certificates path, starting from the sender's certificate. The number @code{n} must be positive. @end table Values of @var{nr_of_certs} smaller than -2 are undefined. This option is only relevant to the CMS crypto engine, and ignored by all other engines. @end deftypefun @deftypefun int gpgme_get_include_certs (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_get_include_certs} returns the number of certificates to include into an S/MIME signed message. @end deftypefun @node Key Listing Mode @subsection Key Listing Mode @cindex key listing mode @cindex key listing, mode of @deftypefun void gpgme_set_keylist_mode (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_keylist_mode_t @var{mode}}) The function @code{gpgme_set_keylist_mode} changes the default behaviour of the key listing functions. The value in @var{mode} is a bitwise-or combination of one or multiple of the following bit values: @table @code @item GPGME_KEYLIST_MODE_LOCAL The @code{GPGME_KEYLIST_MODE_LOCAL} symbol specifies that the local keyring should be searched for keys in the keylisting operation. This is the default. @item GPGME_KEYLIST_MODE_EXTERN The @code{GPGME_KEYLIST_MODE_EXTERN} symbol specifies that an external source should be should be searched for keys in the keylisting operation. The type of external source is dependant on the crypto engine used. For example, it can be a remote keyserver or LDAP certificate server. @item GPGME_KEYLIST_MODE_SIGS The @code{GPGME_KEYLIST_MODE_SIGS} symbol specifies that the key signatures should be included in the listed keys. @end table At least one of @code{GPGME_KEYLIST_MODE_LOCAL} and @code{GPGME_KEYLIST_MODE_EXTERN} must be specified. For future binary compatibility, you should get the current mode with @code{gpgme_get_keylist_mode} and modify it by setting or clearing the appropriate bits, and then using that calulcated value in the @code{gpgme_set_keylisting_mode} operation. This will leave all other bits in the mode value intact (in particular those that are not used in the current version of the library). The function returns @code{GPGME_No_Error} if the mode could be set correctly, and @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer or @var{mode} is not a valid mode. @end deftypefun @deftypefun gpgme_keylist_mode_t gpgme_get_keylist_mode (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_get_keylist_mode} returns the current key listing mode of the context @var{ctx}. This value can then be modified and used in a subsequent @code{gpgme_set_keylist_mode} operation to only affect the desired bits (and leave all others intact). The function returns 0 if @var{ctx} is not a valid pointer, and the current mode otherwise. Note that 0 is not a valid mode value. @end deftypefun @node Passphrase Callback @subsection Passphrase Callback @cindex callback, passphrase @cindex passphrase callback @deftp {Data type} {gpgme_error_t (*gpgme_passphrase_cb_t)(void *@var{hook}, const char *@var{uid_hint}, const char *@var{passphrase_info}, @w{int @var{prev_was_bad}}, @w{int @var{fd}})} @tindex gpgme_passphrase_cb_t The @code{gpgme_passphrase_cb_t} type is the type of functions usable as passphrase callback function. The argument @var{uid_hint} might contain a string that gives an indication for which user ID the passphrase is required. If this is not available, or not applicable (in the case of symmetric encryption, for example), @var{uid_hint} will be @code{NULL}. The argument @var{passphrase_info}, if not @code{NULL}, will give further information about the context in which the passphrase is required. This information is engine and operation specific. If this is the repeated attempt to get the passphrase, because previous attempts failed, then @var{prev_was_bad} is 1, otherwise it will be 0. The user must write the passphrase, followed by a newline character, to the file descriptor @var{fd}. If the user does not return 0 indicating success, the user must at least write a newline character before returning from the callback. If an error occurs, return the corresponding @code{gpgme_error_t} value. You can use @code{GPGME_Canceled} to abort the operation. Otherwise, return @code{0}. @end deftp @deftypefun void gpgme_set_passphrase_cb (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_passphrase_cb_t @var{passfunc}}, @w{void *@var{hook_value}}) The function @code{gpgme_set_passphrase_cb} sets the function that is used when a passphrase needs to be provided by the user to @var{passfunc}. The function @var{passfunc} needs to implemented by the user, and whenever it is called, it is called with its first argument being @var{hook_value}. By default, no passphrase callback function is set. Not all crypto engines require this callback to retrieve the passphrase. It is better if the engine retrieves the passphrase from a trusted agent (a daemon process), rather than having each user to implement their own passphrase query. The user can disable the use of a passphrase callback function by calling @code{gpgme_set_passphrase_cb} with @var{passfunc} being @code{NULL}. @end deftypefun @deftypefun void gpgme_get_passphrase_cb (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_passphrase_cb_t *@var{passfunc}}, @w{void **@var{hook_value}}) The function @code{gpgme_get_passphrase_cb} returns the function that is used when a passphrase needs to be provided by the user in @var{*passfunc}, and the first argument for this function in @var{*hook_value}. If no passphrase callback is set, or @var{ctx} is not a valid pointer, @code{NULL} is returned in both variables. @var{passfunc} or @var{hook_value} can be @code{NULL}. In this case, the corresponding value will not be returned. @end deftypefun @node Progress Meter Callback @subsection Progress Meter Callback @cindex callback, progress meter @cindex progress meter callback @deftp {Data type} {const char *(*gpgme_progress_cb_t)(void *@var{hook}, const char *@var{what}, int @var{type}, int @var{current}, int @var{total})} @tindex gpgme_progress_cb_t The @code{gpgme_progress_cb_t} type is the type of functions usable as progress callback function. The arguments are specific to the crypto engine. More information about the progress information returned from the GnuPG engine can be found in the GnuPG source code in the file @file{doc/DETAILS} in the section PROGRESS. @end deftp @deftypefun void gpgme_set_progress_cb (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_progress_cb_t @var{progfunc}}, @w{void *@var{hook_value}}) The function @code{gpgme_set_progress_cb} sets the function that is used when progress information about a cryptographic operation is available. The function @var{progfunc} needs to implemented by the user, and whenever it is called, it is called with its first argument being @var{hook_value}. By default, no progress callback function is set. Setting a callback function allows an interactive program to display progress information about a long operation to the user. The user can disable the use of a progress callback function by calling @code{gpgme_set_progress_cb} with @var{progfunc} being @code{NULL}. @end deftypefun @deftypefun void gpgme_get_progress_cb (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_progress_cb_t *@var{progfunc}}, @w{void **@var{hook_value}}) The function @code{gpgme_get_progress_cb} returns the function that is used to inform the user about the progress made in @var{*progfunc}, and the first argument for this function in @var{*hook_value}. If no progress callback is set, or @var{ctx} is not a valid pointer, @code{NULL} is returned in both variables. @var{progfunc} or @var{hook_value} can be @code{NULL}. In this case, the corresponding value will not be returned. @end deftypefun @node Key Management @section Key Management @cindex key management Some of the cryptographic operations require that recipients or signers are specified. This is always done by specifying the respective keys that should be used for the operation. The following section describes how such keys can be selected and manipulated. @deftp {Data type} gpgme_sub_key_t The @code{gpgme_sub_key_t} type is a pointer to a subkey structure. Sub keys are one component of a @code{gpgme_key_t} object. In fact, subkeys are those parts that contains the real information about the individual cryptographic keys that belong to the same key object. One @code{gpgme_key_t} can contain several subkeys. The first subkey in the linked list is also called the primary key. The subkey structure has the following members: @table @code @item gpgme_sub_key_t next This is a pointer to the next subkey structure in the linked list, or @code{NULL} if this is the last element. @item unsigned int revoked : 1 This is true if the subkey is revoked. @item unsigned int expired : 1 This is true if the subkey is expired. @item unsigned int disabled : 1 This is true if the subkey is disabled. @item unsigned int invalid : 1 This is true if the subkey is invalid. @item unsigned int can_encrypt : 1 This is true if the subkey can be used for encryption. @item unsigned int can_sign : 1 This is true if the subkey can be used for signing. @item unsigned int can_certify : 1 This is true if the subkey can be used for certification. @item unsigned int secret : 1 This is true if the subkey is a secret key. @item gpgme_pubkey_algo_t pubkey_algo This is the public key algorithm supported by this subkey. @item unsigned int length This is the length of the subkey (in bits). @item char *keyid This is the key ID of the subkey in hexadecimal digits. @item char *fpr This is the fingerprint of the subkey in hexadecimal digits, if available. This is usually only available for the primary key. @item long int timestamp This is the creation timestamp of the subkey. This is -1 if the timestamp is invalid, and 0 if it is not available. @item long int expires This is the expiration timestamp of the subkey, or 0 if the subkey does not expire. @end table @end deftp @deftp {Data type} gpgme_key_sig_t The @code{gpgme_key_sig_t} type is a pointer to a key signature structure. Key signatures are one component of a @code{gpgme_key_t} object, and validate user IDs on the key. The signatures on a key are only available if the key was retrieved via a listing operation with the @code{GPGME_KEYLIST_MODE_SIGS} mode enabled, because it is expensive to retrieve all signatures of a key. The key signature structure has the following members: @table @code @item gpgme_key_sig_t next This is a pointer to the next key signature structure in the linked list, or @code{NULL} if this is the last element. @item unsigned int revoked : 1 This is true if the key signature is a revocation signature. @item unsigned int expired : 1 This is true if the key signature is expired. @item unsigned int invalid : 1 This is true if the key signature is invalid. @item unsigned int disabled : 1 This is true if the key signature is exportable. @item gpgme_pubkey_algo_t pubkey_algo This is the public key algorithm used to create the signature. @item char *keyid This is the key ID of the key (in hexadecimal digits) used to create the signature. @item long int timestamp This is the creation timestamp of the key signature. This is -1 if the timestamp is invalid, and 0 if it is not available. @item long int expires This is the expiration timestamp of the key signature, or 0 if the key signature does not expire. @item gpgme_error_t status This is the status of the signature and has the same meaning as the member of the same name in a @code{gpgme_signature_t} object. @item unsigned int class This specifies the signature class of the key signature. The meaning is specific to the crypto engine. @item char *uid This is the main user ID of the key used to create the signature. @item char *name This is the name component of @code{uid}, if available. @item char *comment This is the comment component of @code{uid}, if available. @item char *email This is the email component of @code{uid}, if available. @end table @end deftp @deftp {Data type} gpgme_user_id_t A user ID is a component of a @code{gpgme_key_t} object. One key can have many user IDs. The first one in the list is the main (or primary) user ID. The user ID structure has the following members. @table @code @item gpgme_user_id_t next This is a pointer to the next user ID structure in the linked list, or @code{NULL} if this is the last element. @item unsigned int revoked : 1 This is true if the user ID is revoked. @item unsigned int invalid : 1 This is true if the user ID is invalid. @item gpgme_validity_t validity This specifies the validity of the user ID. @item char *uid This is the user ID string. @item char *name This is the name component of @code{uid}, if available. @item char *comment This is the comment component of @code{uid}, if available. @item char *email This is the email component of @code{uid}, if available. @item gpgme_key_sig_t signatures This is a linked list with the signatures on this user ID. @end table @end deftp @deftp {Data type} gpgme_key_t The @code{gpgme_key_t} type is a pointer to a key object. It has the following members: @table @code @item unsigned int revoked : 1 This is true if the key is revoked. @item unsigned int expired : 1 This is true if the key is expired. @item unsigned int disabled : 1 This is true if the key is disabled. @item unsigned int invalid : 1 This is true if the key is invalid. @item unsigned int can_encrypt : 1 This is true if the key (ie one of its subkeys) can be used for encryption. @item unsigned int can_sign : 1 This is true if the key (ie one of its subkeys) can be used for signing. @item unsigned int can_certify : 1 This is true if the key (ie one of its subkeys) can be used for certification. @item unsigned int secret : 1 This is true if the key is a secret key. @item gpgme_protocol_t protocol This is the protocol supported by this key. @item char *issuer_serial If @code{protocol} is @code{GPGME_PROTOCOL_CMS}, then this is the issuer serial. @item char *issuer_name If @code{protocol} is @code{GPGME_PROTOCOL_CMS}, then this is the issuer name. @item char *chain_id If @code{protocol} is @code{GPGME_PROTOCOL_CMS}, then this is the chain ID, which can be used to built the certificate chain. @item gpgme_validity_t owner_trust If @code{protocol} is @code{GPGME_PROTOCOL_OpenPGP}, then this is the owner trust. @item gpgme_sub_key_t subkeys This is a linked list with the subkeys of the key. The first subkey in the list is the primary key and usually available. @item gpgme_user_id_t uids This is a linked list with the user IDs of the key. The first user ID in the list is the main (or primary) user ID. @end table @end deftp @menu * Listing Keys:: Browsing the list of available keys. * Information About Keys:: Requesting detailed information about keys. * Key Signatures:: Listing the signatures on a key. * Manipulating Keys:: Operations on keys. * Generating Keys:: Creating new key pairs. * Exporting Keys:: Retrieving key data from the key ring. * Importing Keys:: Adding keys to the key ring. * Deleting Keys:: Removing keys from the key ring. @end menu @node Listing Keys @subsection Listing Keys @cindex listing keys @cindex key listing @cindex key listing, start @cindex key ring, list @cindex key ring, search @deftypefun gpgme_error_t gpgme_op_keylist_start (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}}, @w{int @var{secret_only}}) The function @code{gpgme_op_keylist_start} initiates a key listing operation inside the context @var{ctx}. It sets everything up so that subsequent invocations of @code{gpgme_op_keylist_next} return the keys in the list. If @var{pattern} is @code{NULL}, all available keys are returned. Otherwise, @var{pattern} contains an engine specific expression that is used to limit the list to all keys matching the pattern. If @var{secret_only} is not @code{0}, the list is restricted to secret keys only. The context will be busy until either all keys are received (and @code{gpgme_op_keylist_next} returns @code{GPGME_EOF}), or @code{gpgme_op_keylist_end} is called to finish the operation. The function returns @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_keylist_ext_start (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}[]}, @w{int @var{secret_only}}, @w{int @var{reserved}}) The function @code{gpgme_op_keylist_ext_start} initiates an extended key listing operation inside the context @var{ctx}. It sets everything up so that subsequent invocations of @code{gpgme_op_keylist_next} return the keys in the list. If @var{pattern} or @var{*pattern} is @code{NULL}, all available keys are returned. Otherwise, @var{pattern} is a @code{NULL} terminated array of strings that are used to limit the list to all keys matching at least one of the patterns verbatim. If @var{secret_only} is not @code{0}, the list is restricted to secret keys only. The value of @var{reserved} must be @code{0}. The context will be busy until either all keys are received (and @code{gpgme_op_keylist_next} returns @code{GPGME_EOF}), or @code{gpgme_op_keylist_end} is called to finish the operation. The function returns @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_keylist_next (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_key_t *@var{r_key}}) The function @code{gpgme_op_keylist_next} returns the next key in the list created by a previous @code{gpgme_op_keylist_start} operation in the context @var{ctx}. The key will have one reference for the user. @xref{Manipulating Keys}. This is the only way to get at @code{gpgme_key_t} objects in @acronym{GPGME}. If the last key in the list has already been returned, @code{gpgme_op_keylist_next} returns @code{GPGME_EOF}. The function returns @code{GPGME_Invalid_Value} if @var{ctx} or @var{r_key} is not a valid pointer, and @code{GPGME_Out_Of_Core} if there is not enough memory for the operation. @end deftypefun @deftypefun gpgme_error_t gpgme_op_keylist_end (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_keylist_next} ends a pending key list operation in the context @var{ctx}. After the operation completed successfully, the result of the key listing operation can be retrieved with @code{gpgme_op_keylist_result}. The function returns @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer, and @code{GPGME_Out_Of_Core} if at some time during the operation there was not enough memory available. @end deftypefun The following example illustrates how all keys containing a certain string (@code{g10code}) can be listed with their key ID and the name and e-mail address of the main user ID: @example gpgme_ctx_t ctx; gpgme_error_t err = gpgme_new (&ctx); if (!err) @{ err = gpgme_op_keylist_start (ctx, "g10code", 0); while (!err && (err = gpgme_op_keylist_next (ctx, &key)) != GPGME_EOF) @{ printf ("%s: %s <%s>\n", gpgme_key_get_string_attr (key, GPGME_ATTR_KEYID, 0, 0), gpgme_key_get_string_attr (key, GPGME_ATTR_NAME, 0, 0), gpgme_key_get_string_attr (key, GPGME_ATTR_EMAIL, 0, 0)); gpgme_key_release (key); @} gpgme_release (ctx); @} if (err) @{ fprintf (stderr, "%s: can not list keys: %s\n", argv[0], gpgme_strerror (err)); exit (1); @} @end example @deftp {Data type} {gpgme_keylist_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_keylist_*} operation. After successfully ending a key listing operation, you can retrieve the pointer to the result with @code{gpgme_op_keylist_result}. The structure contains the following member: @table @code @item unsigned int truncated : 1 This is true if the crypto backend had to truncate the result, and less than the desired keys could be listed. @end table @end deftp @deftypefun gpgme_keylist_result_t gpgme_op_keylist_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_keylist_result} returns a @code{gpgme_keylist_result_t} pointer to a structure holding the result of a @code{gpgme_op_keylist_*} operation. The pointer is only valid if the last operation on the context was a key listing operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun In a simple program, for which a blocking operation is acceptable, the following function can be used to retrieve a single key. @deftypefun gpgme_error_t gpgme_get_key (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{fpr}}, @w{gpgme_key_t *@var{r_key}}, @w{int @var{secret}}) The function @code{gpgme_get_key} gets the key with the fingerprint (or key ID) @var{fpr} from the crypto backend and return it in @var{r_key}. If @var{force_update} is true, force a refresh of the key from the crypto backend and replace the key in the cache, if any. If @var{secret} is true, get the secret key. The currently active keylist mode is used to retrieve the key. If the key is not found in the keyring, @code{gpgme_get_key} returns @code{GPGME_No_Error} and *@var{r_key} will be set to @code{NULL}. The function returns @code{GPGME_Invalid_Value} if @var{ctx} or @var{r_key} is not a valid pointer, @code{GPGME_Invalid_Key} if @var{fpr} is not a fingerprint or key ID, @code{GPGME_Out_Of_Core} if at some time during the operation there was not enough memory available. @end deftypefun @node Information About Keys @subsection Information About Keys @cindex key, information about @cindex key, attributes @cindex attributes, of a key Please see the beginning of this section for more information about @code{gpgme_key_t} objects. @deftp {Data type} gpgme_validity_t The @code{gpgme_validity_t} type is used to specify the validity of a user ID in a key. The following validities are defined: @table @code @item GPGME_VALIDITY_UNKNOWN The user ID is of unknown validity. The string representation of this validity is ``?''. @item GPGME_VALIDITY_UNDEFINED The validity of the user ID is undefined. The string representation of this validity is ``q''. @item GPGME_VALIDITY_NEVER The user ID is never valid. The string representation of this validity is ``n''. @item GPGME_VALIDITY_MARGINAL The user ID is marginally valid. The string representation of this validity is ``m''. @item GPGME_VALIDITY_FULL The user ID is fully valid. The string representation of this validity is ``f''. @item GPGME_VALIDITY_ULTIMATE The user ID is ultimately valid. The string representation of this validity is ``u''. @end table @end deftp The following interfaces are deprecated and only provided for backward compatibility. Don't use them. They will be removed in a future version of @acronym{GPGME}. @deftp {Data type} gpgme_attr_t The @code{gpgme_attr_t} type is used to specify a key or trust item attribute. The following attributes are defined: @table @code @item GPGME_ATTR_KEYID This is the key ID of a sub key. It is representable as a string. For trust items, the trust item refers to the key with this ID. @item GPGME_ATTR_FPR This is the fingerprint of a sub key. It is representable as a string. @item GPGME_ATTR_ALGO This is the crypto algorithm for which the sub key can be used. It is representable as a string and as a number. The numbers correspond to the @code{enum gcry_pk_algos} values in the gcrypt library. @item GPGME_ATTR_LEN This is the key length of a sub key. It is representable as a number. @item GPGME_ATTR_CREATED This is the timestamp at creation time of a sub key. It is representable as a number. @item GPGME_ATTR_EXPIRE This is the expiration time of a sub key. It is representable as a number. @item GPGME_ATTR_OTRUST XXX FIXME (also for trust items) @item GPGME_ATTR_USERID This is a user ID. There can be more than one user IDs in a @var{gpgme_key_t} object. The first one (with index 0) is the primary user ID. The user ID is representable as a number. For trust items, this is the user ID associated with this trust item. @item GPGME_ATTR_NAME This is the name belonging to a user ID. It is representable as a string. @item GPGME_ATTR_EMAIL This is the email address belonging to a user ID. It is representable as a string. @item GPGME_ATTR_COMMENT This is the comment belonging to a user ID. It is representable as a string. @item GPGME_ATTR_VALIDITY This is the validity belonging to a user ID. It is representable as a string and as a number. See below for a list of available validities. For trust items, this is the validity that is associated with this trust item. @item GPGME_ATTR_UID_REVOKED This specifies if a user ID is revoked. It is representable as a number, and is @code{1} if the user ID is revoked, and @code{0} otherwise. @item GPGME_ATTR_UID_INVALID This specifies if a user ID is invalid. It is representable as a number, and is @code{1} if the user ID is invalid, and @code{0} otherwise. @item GPGME_ATTR_LEVEL This is the trust level of a trust item. @item GPGME_ATTR_TYPE This returns information about the type of key. For the string function this will eother be "PGP" or "X.509". The integer function returns 0 for PGP and 1 for X.509. It is also used for the type of a trust item. @item GPGME_ATTR_IS_SECRET This specifies if the key is a secret key. It is representable as a number, and is @code{1} if the key is revoked, and @code{0} otherwise. @item GPGME_ATTR_KEY_REVOKED This specifies if a sub key is revoked. It is representable as a number, and is @code{1} if the key is revoked, and @code{0} otherwise. @item GPGME_ATTR_KEY_INVALID This specifies if a sub key is invalid. It is representable as a number, and is @code{1} if the key is invalid, and @code{0} otherwise. @item GPGME_ATTR_KEY_EXPIRED This specifies if a sub key is expired. It is representable as a number, and is @code{1} if the key is expired, and @code{0} otherwise. @item GPGME_ATTR_KEY_DISABLED This specifies if a sub key is disabled. It is representable as a number, and is @code{1} if the key is disabled, and @code{0} otherwise. @item GPGME_ATTR_KEY_CAPS This is a description of the capabilities of a sub key. It is representable as a string. The string contains the letter ``e'' if the key can be used for encryption, ``s'' if the key can be used for signatures, and ``c'' if the key can be used for certifications. @item GPGME_ATTR_CAN_ENCRYPT This specifies if a sub key can be used for encryption. It is representable as a number, and is @code{1} if the sub key can be used for encryption, and @code{0} otherwise. @item GPGME_ATTR_CAN_SIGN This specifies if a sub key can be used for signatures. It is representable as a number, and is @code{1} if the sub key can be used for signatures, and @code{0} otherwise. @item GPGME_ATTR_CAN_CERTIFY This specifies if a sub key can be used for certifications. It is representable as a number, and is @code{1} if the sub key can be used for certifications, and @code{0} otherwise. @item GPGME_ATTR_SERIAL The X.509 issuer serial attribute of the key. It is representable as a string. @item GPGME_ATTR_ISSUE The X.509 issuer name attribute of the key. It is representable as a string. @item GPGME_ATTR_CHAINID The X.509 chain ID can be used to build the certification chain. It is representable as a string. @end table @end deftp @deftypefun {const char *} gpgme_key_get_string_attr (@w{gpgme_key_t @var{key}}, @w{gpgme_attr_t @var{what}}, @w{const void *@var{reserved}}, @w{int @var{idx}}) The function @code{gpgme_key_get_string_attr} returns the value of the string-representable attribute @var{what} of key @var{key}. If the attribute is an attribute of a sub key or an user ID, @var{idx} specifies the sub key or user ID of which the attribute value is returned. The argument @var{reserved} is reserved for later use and should be @code{NULL}. The string returned is only valid as long as the key is valid. The function returns @code{0} if an attribute can't be returned as a string, @var{key} is not a valid pointer, @var{idx} out of range, or @var{reserved} not @code{NULL}. @end deftypefun @deftypefun {unsigned long} gpgme_key_get_ulong_attr (@w{gpgme_key_t @var{key}}, @w{gpgme_attr_t @var{what}}, @w{const void *@var{reserved}}, @w{int @var{idx}}) The function @code{gpgme_key_get_ulong_attr} returns the value of the number-representable attribute @var{what} of key @var{key}. If the attribute is an attribute of a sub key or an user ID, @var{idx} specifies the sub key or user ID of which the attribute value is returned. The argument @var{reserved} is reserved for later use and should be @code{NULL}. The function returns @code{0} if the attribute can't be returned as a number, @var{key} is not a valid pointer, @var{idx} out of range, or @var{reserved} not @code{NULL}. @end deftypefun @node Key Signatures @subsection Key Signatures @cindex key, signatures @cindex signatures, on a key The following interfaces are deprecated and only provided for backward compatibility. Don't use them. They will be removed in a future version of @acronym{GPGME}. The signatures on a key are only available if the key was retrieved via a listing operation with the @code{GPGME_KEYLIST_MODE_SIGS} mode enabled, because it is expensive to retrieve all signatures of a key. So, before using the below interfaces to retrieve the signatures on a key, you have to make sure that the key was listed with signatures enabled. One convenient, but blocking, way to do this is to use the function @code{gpgme_get_key}. @deftp {Data type} gpgme_attr_t The @code{gpgme_attr_t} type is used to specify a key signature attribute. The following attributes are defined: @table @code @item GPGME_ATTR_KEYID This is the key ID of the key which was used for the signature. It is representable as a string. @item GPGME_ATTR_ALGO This is the crypto algorithm used to create the signature. It is representable as a string and as a number. The numbers correspond to the @code{enum gcry_pk_algos} values in the gcrypt library. @item GPGME_ATTR_CREATED This is the timestamp at creation time of the signature. It is representable as a number. @item GPGME_ATTR_EXPIRE This is the expiration time of the signature. It is representable as a number. @item GPGME_ATTR_USERID This is the user ID associated with the signing key. The user ID is representable as a number. @item GPGME_ATTR_NAME This is the name belonging to a user ID. It is representable as a string. @item GPGME_ATTR_EMAIL This is the email address belonging to a user ID. It is representable as a string. @item GPGME_ATTR_COMMENT This is the comment belonging to a user ID. It is representable as a string. @item GPGME_ATTR_KEY_REVOKED This specifies if a key signature is a revocation signature. It is representable as a number, and is @code{1} if the key is revoked, and @code{0} otherwise. @c @item GPGME_ATTR_KEY_EXPIRED @c This specifies if a key signature is expired. It is representable as @c a number, and is @code{1} if the key is revoked, and @code{0} @c otherwise. @c @item GPGME_ATTR_SIG_CLASS This specifies the signature class of a key signature. It is representable as a number. The meaning is specific to the crypto engine. @item GPGME_ATTR_SIG_CLASS This specifies the signature class of a key signature. It is representable as a number. The meaning is specific to the crypto engine. @item GPGME_ATTR_SIG_STATUS This is the same value as returned by @code{gpgme_get_sig_status}. @end table @end deftp @deftypefun {const char *} gpgme_key_sig_get_string_attr (@w{gpgme_key_t @var{key}}, @w{int @var{uid_idx}}, @w{gpgme_attr_t @var{what}}, @w{const void *@var{reserved}}, @w{int @var{idx}}) The function @code{gpgme_key_sig_get_string_attr} returns the value of the string-representable attribute @var{what} of the signature @var{idx} on the user ID @var{uid_idx} in the key @var{key}. The argument @var{reserved} is reserved for later use and should be @code{NULL}. The string returned is only valid as long as the key is valid. The function returns @code{0} if an attribute can't be returned as a string, @var{key} is not a valid pointer, @var{uid_idx} or @var{idx} out of range, or @var{reserved} not @code{NULL}. @end deftypefun @deftypefun {unsigned long} gpgme_key_sig_get_ulong_attr (@w{gpgme_key_t @var{key}}, @w{int @var{uid_idx}}, @w{gpgme_attr_t @var{what}}, @w{const void *@var{reserved}}, @w{int @var{idx}}) The function @code{gpgme_key_sig_get_ulong_attr} returns the value of the number-representable attribute @var{what} of the signature @var{idx} on the user ID @var{uid_idx} in the key @var{key}. The argument @var{reserved} is reserved for later use and should be @code{NULL}. The function returns @code{0} if an attribute can't be returned as a string, @var{key} is not a valid pointer, @var{uid_idx} or @var{idx} out of range, or @var{reserved} not @code{NULL}. @end deftypefun @node Manipulating Keys @subsection Manipulating Keys @cindex key, manipulation @deftypefun void gpgme_key_ref (@w{gpgme_key_t @var{key}}) The function @code{gpgme_key_ref} acquires an additional reference for the key @var{key}. @end deftypefun @deftypefun void gpgme_key_unref (@w{gpgme_key_t @var{key}}) The function @code{gpgme_key_unref} releases a reference for the key @var{key}. If this was the last reference, the key will be destroyed and all resources associated to it will be released. @end deftypefun The following interface is deprecated and only provided for backward compatibility. Don't use it. It will be removed in a future version of @acronym{GPGME}. @deftypefun void gpgme_key_release (@w{gpgme_key_t @var{key}}) The function @code{gpgme_key_release} is equivalent to @code{gpgme_key_unref}. @end deftypefun @node Generating Keys @subsection Generating Keys @cindex key, creation @cindex key ring, add @deftypefun gpgme_error_t gpgme_op_genkey (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{parms}}, @w{gpgme_data_t @var{public}}, @w{gpgme_data_t @var{secret}}) The function @code{gpgme_op_genkey} generates a new key pair in the context @var{ctx}. The meaning of @var{public} and @var{secret} depends on the crypto backend. GnuPG does not support @var{public} and @var{secret}, they should be @code{NULL}. GnuPG will generate a key pair and add it to the standard key ring. The fingerprint of the generated key is available with @code{gpgme_op_genkey_result}. GpgSM requires @var{public} to be a writable data object. GpgSM will generate a secret key (which will be stored by @command{gpg-agent}, and return a certificate request in @var{public}, which then needs to be signed by the certification authority and imported before it can be used. GpgSM does not make the fingerprint available. The argument @var{parms} specifies parameters for the key in an XML string. The details about the format of @var{parms} are specific to the crypto engine used by @var{ctx}. Here is an example for GnuPG as the crypto engine: @example Key-Type: DSA Key-Length: 1024 Subkey-Type: ELG-E Subkey-Length: 1024 Name-Real: Joe Tester Name-Comment: with stupid passphrase Name-Email: joe@@foo.bar Expire-Date: 0 Passphrase: abc @end example Here is an example for GpgSM as the crypto engine: @example Key-Type: RSA Key-Length: 1024 Name-DN: C=de,O=g10 code,OU=Testlab,CN=Joe 2 Tester Name-Email: joe@@foo.bar @end example Strings should be given in UTF-8 encoding. The only format supported for now is ``internal''. The content of the @code{GnupgKeyParms} container is passed verbatim to the crypto backend. Control statements are not allowed. After the operation completed successfully, the result can be retrieved with @code{gpgme_op_genkey_result}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, @code{GPGME_Invalid_Value} if @var{parms} is not a valid XML string, @code{GPGME_Not_Supported} if @var{public} or @var{secret} is not valid, and @code{GPGME_General_Error} if no key was created by the backend. @end deftypefun @deftypefun gpgme_error_t gpgme_op_genkey_start (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{parms}}, @w{gpgme_data_t @var{public}}, @w{gpgme_data_t @var{secret}}) The function @code{gpgme_op_genkey_start} initiates a @code{gpgme_op_genkey} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, @code{GPGME_Invalid_Value} if @var{parms} is not a valid XML string, and @code{GPGME_Not_Supported} if @var{public} or @var{secret} is not @code{NULL}. @end deftypefun @deftp {Data type} {gpgme_genkey_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_genkey} operation. After successfully generating a key, you can retrieve the pointer to the result with @code{gpgme_op_genkey_result}. The structure contains the following members: @table @code @item unsigned int primary : 1 This is a flag that is set to 1 if a primary key was created and to 0 if not. @item unsigned int sub : 1 This is a flag that is set to 1 if a subkey was created and to 0 if not. @item char *fpr This is the fingerprint of the key that was created. If both a primary and a sub key were generated, the fingerprint of the primary key will be returned. If the crypto engine does not provide the fingerprint, @code{fpr} will be a null pointer. @end table @end deftp @deftypefun gpgme_genkey_result_t gpgme_op_genkey_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_genkey_result} returns a @code{gpgme_genkey_result_t} pointer to a structure holding the result of a @code{gpgme_op_genkey} operation. The pointer is only valid if the last operation on the context was a @code{gpgme_op_genkey} or @code{gpgme_op_genkey_start} operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun @node Exporting Keys @subsection Exporting Keys @cindex key, export @cindex key ring, export from @deftypefun gpgme_error_t gpgme_op_export (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}}, @w{unsigned int @var{reserved}}, @w{gpgme_data_t @var{keydata}}) The function @code{gpgme_op_export} extracts public keys and returns them in the data buffer @var{keydata}. The output format of the key data returned is determined by the @acronym{ASCII} armor attribute set for the context @var{ctx}. If @var{pattern} is @code{NULL}, all available keys are returned. Otherwise, @var{pattern} contains an engine specific expression that is used to limit the list to all keys matching the pattern. @var{reserved} is reserved for future use and must be @code{0}. The function returns @code{GPGME_No_Error} if the operation completed successfully, @code{GPGME_Invalid_Value} if @var{keydata} is not a valid empty data buffer, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_export_start (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}}, @w{unsigned int @var{reserved}}, @w{gpgme_data_t @var{keydata}}) The function @code{gpgme_op_export_start} initiates a @code{gpgme_op_export} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, and @code{GPGME_Invalid_Value} if @var{keydata} is not a valid empty data buffer. @end deftypefun @deftypefun gpgme_error_t gpgme_op_export_ext (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}[]}, @w{unsigned int @var{reserved}}, @w{gpgme_data_t @var{keydata}}) The function @code{gpgme_op_export} extracts public keys and returns them in the data buffer @var{keydata}. The output format of the key data returned is determined by the @acronym{ASCII} armor attribute set for the context @var{ctx}. If @var{pattern} or @var{*pattern} is @code{NULL}, all available keys are returned. Otherwise, @var{pattern} is a @code{NULL} terminated array of strings that are used to limit the list to all keys matching at least one of the patterns verbatim. @var{reserved} is reserved for future use and must be @code{0}. The function returns @code{GPGME_No_Error} if the operation completed successfully, @code{GPGME_Invalid_Value} if @var{keydata} is not a valid empty data buffer, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_export_ext_start (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}[]}, @w{unsigned int @var{reserved}}, @w{gpgme_data_t @var{keydata}}) The function @code{gpgme_op_export_ext_start} initiates a @code{gpgme_op_export_ext} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, and @code{GPGME_Invalid_Value} if @var{keydata} is not a valid empty data buffer. @end deftypefun @node Importing Keys @subsection Importing Keys @cindex key, import @cindex key ring, import to @deftypefun gpgme_error_t gpgme_op_import (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{keydata}}) The function @code{gpgme_op_import} adds the keys in the data buffer @var{keydata} to the key ring of the crypto engine used by @var{ctx}. The format of @var{keydata} can be @acronym{ASCII} armored, for example, but the details are specific to the crypto engine. After the operation completed successfully, the result can be retrieved with @code{gpgme_op_import_result}. The function returns @code{GPGME_No_Error} if the import was completed successfully, @code{GPGME_Invalid_Value} if @var{keydata} if @var{ctx} or @var{keydata} is not a valid pointer, and @code{GPGME_No_Data} if @var{keydata} is an empty data buffer. @end deftypefun @deftypefun gpgme_error_t gpgme_op_import_start (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{keydata}}) The function @code{gpgme_op_import_start} initiates a @code{gpgme_op_import} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the import could be started successfully, @code{GPGME_Invalid_Value} if @var{keydata} if @var{ctx} or @var{keydata} is not a valid pointer, and @code{GPGME_No_Data} if @var{keydata} is an empty data buffer. @end deftypefun @deftp {Data type} {gpgme_import_status_t} This is a pointer to a structure used to store a part of the result of a @code{gpgme_op_import} operation. For each considered key one status is added that contains information about the result of the import. The structure contains the following members: @table @code @item gpgme_import_status_t next This is a pointer to the next status structure in the linked list, or @code{NULL} if this is the last element. @item char *fpr This is the fingerprint of the key that was considered. @item gpgme_error_t result If the import was not successful, this is the error value that caused the import to fail. Otherwise it is @code{GPGME_No_Error}. @item unsigned int status This is a bit-wise OR of the following flags that give more information about what part of the key was imported. If the key was already known, this might be 0. @table @code @item GPGME_IMPORT_NEW The key was new. @item GPGME_IMPORT_UID The key contained new user IDs. @item GPGME_IMPORT_SIG The key contained new signatures. @item GPGME_IMPORT_SUBKEY The key contained new sub keys. @item GPGME_IMPORT_SECRET The key contained a secret key. @end table @end table @end deftp @deftp {Data type} {gpgme_import_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_import} operation. After a successful import operation, you can retrieve the pointer to the result with @code{gpgme_op_import_result}. The structure contains the following members: @table @code @item int considered The total number of considered keys. @item int no_user_id The number of keys without user ID. @item int imported The total number of imported keys. @item imported_rsa The number of imported RSA keys. @item unchanged The number of unchanged keys. @item new_user_ids The number of new user IDs. @item new_sub_keys The number of new sub keys. @item new_signatures The number of new signatures. @item new_revocations The number of new revocations. @item secret_read The total number of secret keys read. @item secret_imported The number of imported secret keys. @item secret_unchanged The number of unchanged secret keys. @item not_imported The number of keys not imported. @item gpgme_import_status_t imports A list of gpgme_import_status_t objects which contain more information about the keys for which an import was attempted. @end table @end deftp @deftypefun gpgme_import_result_t gpgme_op_import_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_import_result} returns a @code{gpgme_import_result_t} pointer to a structure holding the result of a @code{gpgme_op_import} operation. The pointer is only valid if the last operation on the context was a @code{gpgme_op_import} or @code{gpgme_op_import_start} operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun The following interface is deprecated and only provided for backward compatibility. Don't use it. It will be removed in a future version of @acronym{GPGME}. @deftypefun gpgme_error_t gpgme_op_import_ext (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{keydata}}, @w{int *@var{nr}}) The function @code{gpgme_op_import_ext} is equivalent to: @example gpgme_error_t err = gpgme_op_import (ctx, keydata); if (!err) @{ gpgme_import_result_t result = gpgme_op_import_result (ctx); *nr = result->considered; @} @end example @end deftypefun @node Deleting Keys @subsection Deleting Keys @cindex key, delete @cindex key ring, delete from @deftypefun gpgme_error_t gpgme_op_delete (@w{gpgme_ctx_t @var{ctx}}, @w{const gpgme_key_t @var{key}}, @w{int @var{allow_secret}}) The function @code{gpgme_op_delete} deletes the key @var{key} from the key ring of the crypto engine used by @var{ctx}. If @var{allow_secret} is @code{0}, only public keys are deleted, otherwise secret keys are deleted as well, if that is supported. The function returns @code{GPGME_No_Error} if the key was deleted successfully, @code{GPGME_Invalid_Value} if @var{ctx} or @var{key} is not a valid pointer, @code{GPGME_Invalid_Key} if @var{key} could not be found in the keyring, @code{GPGME_Ambiguous_Specification} if the key was not specified unambiguously, and @code{GPGME_Conflict} if the secret key for @var{key} is available, but @var{allow_secret} is zero. @end deftypefun @deftypefun gpgme_error_t gpgme_op_delete_start (@w{gpgme_ctx_t @var{ctx}}, @w{const gpgme_key_t @var{key}}, @w{int @var{allow_secret}}) The function @code{gpgme_op_delete_start} initiates a @code{gpgme_op_delete} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation was started successfully, and @code{GPGME_Invalid_Value} if @var{ctx} or @var{key} is not a valid pointer. @end deftypefun @node Trust Item Management @section Trust Item Management @cindex trust item @strong{Caution:} The trust items interface is experimental. @deftp {Data type} gpgme_trust_item_t The @code{gpgme_trust_item_t} type is a pointer to a trust item object. It has the following members: @table @code @item char *keyid This is a string describing the key to which this trust items belongs. @item int type This is the type of the trust item. A value of 1 refers to a key, a value of 2 refers to a user ID. @item int level This is the trust level. @item char *owner_trust The owner trust if @code{type} is 1. @item char *validity The calculated validity. @item char *name The user name if @code{type} is 2. @end table @end deftp @menu * Listing Trust Items:: Browsing the list of available trust items. * Information About Trust Items:: Requesting information about trust items. * Manipulating Trust Items:: Operations on trust items. @end menu @node Listing Trust Items @subsection Listing Trust Items @cindex trust item list @deftypefun gpgme_error_t gpgme_op_trustlist_start (@w{gpgme_ctx_t @var{ctx}}, @w{const char *@var{pattern}}, @w{int @var{max_level}}) The function @code{gpgme_op_trustlist_start} initiates a trust item listing operation inside the context @var{ctx}. It sets everything up so that subsequent invocations of @code{gpgme_op_trustlist_next} return the trust items in the list. The string @var{pattern} contains an engine specific expression that is used to limit the list to all trust items matching the pattern. It can not be the empty string. The argument @var{max_level} is currently ignored. The context will be busy until either all trust items are received (and @code{gpgme_op_trustlist_next} returns @code{GPGME_EOF}), or @code{gpgme_op_trustlist_end} is called to finish the operation. The function returns @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_trustlist_next (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_trust_item_t *@var{r_item}}) The function @code{gpgme_op_trustlist_next} returns the next trust item in the list created by a previous @code{gpgme_op_trustlist_start} operation in the context @var{ctx}. The trust item can be destroyed with @code{gpgme_trust_item_release}. @xref{Manipulating Trust Items}. This is the only way to get at @code{gpgme_trust_item_t} objects in @acronym{GPGME}. If the last trust item in the list has already been returned, @code{gpgme_op_trustlist_next} returns @code{GPGME_EOF}. The function returns @code{GPGME_Invalid_Value} if @var{ctx} or @var{r_item} is not a valid pointer, and @code{GPGME_Out_Of_Core} if there is not enough memory for the operation. @end deftypefun @deftypefun gpgme_error_t gpgme_op_trustlist_end (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_trustlist_next} ends a pending key list operation in the context @var{ctx}. The function returns @code{GPGME_Invalid_Value} if @var{ctx} is not a valid pointer, and @code{GPGME_Out_Of_Core} if at some time during the operation there was not enough memory available. @end deftypefun @node Information About Trust Items @subsection Information About Trust Items @cindex trust item, information about @cindex trust item, attributes @cindex attributes, of a trust item The following interfaces are deprecated and only provided for backward compatibility. Don't use them. They will be removed in a future version of @acronym{GPGME}. Trust items have attributes which can be queried using the interfaces below. The attribute identifiers are shared with those for key attributes. @xref{Information About Keys}. @deftypefun {const char *} gpgme_trust_item_get_string_attr (@w{gpgme_trust_item_t @var{item}}, @w{gpgme_attr_t @var{what}}, @w{const void *@var{reserved}}, @w{int @var{idx}}) The function @code{gpgme_trust_item_get_string_attr} returns the value of the string-representable attribute @var{what} of trust item @var{item}. The arguments @var{idx} and @var{reserved} are reserved for later use and should be @code{0} and @code{NULL} respectively. The string returned is only valid as long as the key is valid. The function returns @code{0} if an attribute can't be returned as a string, @var{key} is not a valid pointer, @var{idx} out of range, or @var{reserved} not @code{NULL}. @end deftypefun @deftypefun int gpgme_trust_item_get_int_attr (@w{gpgme_trust_item_t @var{item}}, @w{gpgme_attr_t @var{what}}, @w{const void *@var{reserved}}, @w{int @var{idx}}) The function @code{gpgme_trust_item_get_int_attr} returns the value of the number-representable attribute @var{what} of trust item @var{item}. If the attribute occurs more than once in the trust item, the index is specified by @var{idx}. However, currently no such attribute exists, so @var{idx} should be @code{0}. The argument @var{reserved} is reserved for later use and should be @code{NULL}. The function returns @code{0} if the attribute can't be returned as a number, @var{key} is not a valid pointer, @var{idx} out of range, or @var{reserved} not @code{NULL}. @end deftypefun @node Manipulating Trust Items @subsection Manipulating Trust Items @cindex trust item, manipulation @deftypefun void gpgme_trust_item_ref (@w{gpgme_trust_item_t @var{item}}) The function @code{gpgme_trust_item_ref} acquires an additional reference for the trust item @var{item}. @end deftypefun @deftypefun void gpgme_trust_item_unref (@w{gpgme_trust_item_t @var{item}}) The function @code{gpgme_trust_item_unref} releases a reference for the trust item @var{item}. If this was the last reference, the trust item will be destroyed and all resources associated to it will be released. @end deftypefun The following interface is deprecated and only provided for backward compatibility. Don't use it. It will be removed in a future version of @acronym{GPGME}. @deftypefun void gpgme_trust_item_release (@w{gpgme_trust_item_t @var{item}}) The function @code{gpgme_trust_item_release} is an alias for @code{gpgme_trust_item_unref}. @end deftypefun @node Crypto Operations @section Crypto Operations @cindex cryptographic operation Sometimes, the result of a crypto operation returns a list of invalid user IDs encountered in processing the request. The following structure is used to hold information about such an user ID. @deftp {Data type} {gpgme_invalid_user_id_t} This is a pointer to a structure used to store a part of the result of a crypto operation which takes user IDs as one input parameter. The structure contains the following members: @table @code @item gpgme_invalid_user_id_t next This is a pointer to the next invalid user ID structure in the linked list, or @code{NULL} if this is the last element. @item char *id The invalid user ID encountered. @item gpgme_error_t reason An error code describing the reason why the user ID was found invalid. @end table @end deftp @menu * Decrypt:: Decrypting a ciphertext. * Verify:: Verifying a signature. * Decrypt and Verify:: Decrypting a signed ciphertext. * Sign:: Creating a signature. * Encrypt:: Encrypting a plaintext. @end menu @node Decrypt @subsection Decrypt @cindex decryption @cindex cryptographic operation, decryption @deftypefun gpgme_error_t gpgme_op_decrypt (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{cipher}}, @w{gpgme_data_t @var{plain}}) The function @code{gpgme_op_decrypt} decrypts the ciphertext in the data object @var{cipher} and stores it into the data object @var{plain}. The function returns @code{GPGME_No_Error} if the ciphertext could be decrypted successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{cipher} or @var{plain} is not a valid pointer, @code{GPGME_No_Data} if @var{cipher} does not contain any data to decrypt, @code{GPGME_Decryption_Failed} if @var{cipher} is not a valid cipher text, @code{GPGME_Bad_Passphrase} if the passphrase for the secret key could not be retrieved, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_decrypt_start (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{cipher}}, @w{gpgme_data_t @var{plain}}) The function @code{gpgme_op_decrypt_start} initiates a @code{gpgme_op_decrypt} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, and @code{GPGME_Invalid_Value} if @var{cipher} or @var{plain} is not a valid pointer. @end deftypefun @deftp {Data type} {gpgme_decrypt_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_decrypt} operation. After successfully encrypting data, you can retrieve the pointer to the result with @code{gpgme_op_decrypt_result}. The structure contains the following members: @table @code @item char *unsupported_algorithm If an unsupported algorithm was encountered, this string describes the algorithm that is not supported. @end table @end deftp @deftypefun gpgme_decrypt_result_t gpgme_op_decrypt_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_decrypt_result} returns a @code{gpgme_decrypt_result_t} pointer to a structure holding the result of a @code{gpgme_op_decrypt} operation. The pointer is only valid if the last operation on the context was a @code{gpgme_op_decrypt} or @code{gpgme_op_decrypt_start} operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun @node Verify @subsection Verify @cindex verification @cindex signature, verification @cindex cryptographic operation, verification @cindex cryptographic operation, signature check @deftypefun gpgme_error_t gpgme_op_verify (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{sig}}, @w{gpgme_data_t @var{signed_text}}, @w{gpgme_data_t @var{plain}}) The function @code{gpgme_op_verify} verifies that the signature in the data object @var{sig} is a valid signature. If @var{sig} is a detached signature, then the signed text should be provided in @var{signed_text} and @var{plain} should be a null pointer. Otherwise, if @var{sig} is a normal (or cleartext) signature, @var{signed_text} should be a null pointer and @var{plain} should be a writable data object that will contain the plaintext after successful verification. The results of the individual signature verifications can be retrieved with @code{gpgme_op_verify_result}. The function returns @code{GPGME_No_Error} if the operation could be completed successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{sig}, @var{plain} or @var{r_stat} is not a valid pointer, @code{GPGME_No_Data} if @var{sig} does not contain any data to verify, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_verify_start (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{sig}}, @w{gpgme_data_t @var{signed_text}}, @w{gpgme_data_t @var{plain}}) The function @code{gpgme_op_verify_start} initiates a @code{gpgme_op_verify} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{sig}, @var{plain} or @var{r_stat} is not a valid pointer, and @code{GPGME_No_Data} if @var{sig} or @var{plain} does not contain any data to verify. @end deftypefun @deftp {Data type} {gpgme_sig_notation_t} This is a pointer to a structure used to store a part of the result of a @code{gpgme_op_verify} operation. The structure contains the following members: @table @code @item gpgme_sig_notation_t next This is a pointer to the next new signature notation structure in the linked list, or @code{NULL} if this is the last element. @item char *name The name of the notation field. If this is @code{NULL}, then the member @code{value} will contain a policy URL. @item char *value The value of the notation field. If @code{name} is @code{NULL}, then this is a policy URL. @end table @end deftp @deftp {Data type} {gpgme_signature_t} This is a pointer to a structure used to store a part of the result of a @code{gpgme_op_verify} operation. The structure contains the following members: @table @code @item gpgme_signature_t next This is a pointer to the next new signature structure in the linked list, or @code{NULL} if this is the last element. @item gpgme_sigsum_t summary; This is a bit vector giving a summary of the signature status. It provides an easy interface to a defined semantic of the signature status. Checking just one bit is sufficient to see whether a signature is valid without any restrictions. The defined bits are: @table @code @item GPGME_SIGSUM_VALID The signature is fully valid. @item GPGME_SIGSUM_GREEN The signature is good but one might want to display some extra information. Check the other bits. @item GPGME_SIGSUM_RED The signature is bad. It might be useful to checkother bits and display moe information, i.e. a revoked certificate might not render a signature invalid when the message was received prior to the cause for the revocation. @item GPGME_SIGSUM_KEY_REVOKED The key or at least one certificate has been revoked. @item GPGME_SIGSUM_KEY_EXPIRED The key or one of the certificates has expired. It is probably a good idea to display the date of the expiration. @item GPGME_SIGSUM_SIG_EXPIRED The signature has expired. @item GPGME_SIGSUM_KEY_MISSING Can't verifydue to a missing key o certificate. @item GPGME_SIGSUM_CRL_MISSING The CRL (or an equivalent mechanism) is not available. @item GPGME_SIGSUM_CRL_TOO_OLD Available CRL is too old. @item GPGME_SIGSUM_BAD_POLICY A policy requirement was not met. @item GPGME_SIGSUM_SYS_ERROR A system error occured. @end table @item char *fpr This is the fingerprint or key ID of the signature. @item gpgme_error_t status This is the status of the signature. In particular, the following status codes are of interest: @table @code @item GPGME_No_Error This status indicates that the signature is valid. For the combined result this status means that all signatures are valid. @item GPGME_Sig_Expired This status indicates that the signature is valid but expired. For the combined result this status means that all signatures are valid and expired. @item GPGME_Key_Expired This status indicates that the signature is valid but the key used to verify the signature has expired. For the combined result this status means that all signatures are valid and all keys are expired. @item GPGME_Bad_Signature This status indicates that the signature is invalid. For the combined result this status means that all signatures are invalid. @item GPGME_No_Public_Key This status indicates that the signature could not be verified due to a missing key. For the combined result this status means that all signatures could not be checked due to missing keys. @item GPGME_General_Error This status indicates that there was some other error which prevented the signature verification. @end table @item gpgme_sig_notation_t notations This is a linked list with the notation data and policy URLs. @item unsigned long timestamp The creation timestamp of this signature. @item unsigned long exp_timestamp The expiration timestamp of this signature, or 0 if the signature does not expire. @item int wrong_key_usage : 1; @item gpgme_validity_t validity @item gpgme_error_t validity_reason @end table @end deftp @deftp {Data type} {gpgme_verify_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_verify} operation. After successfully verifying a signature, you can retrieve the pointer to the result with @code{gpgme_op_verify_result}. The structure contains the following member: @table @code @item gpgme_signature_t signatures A linked list with information about all signatures for which a verification was attempted. @end table @end deftp @deftypefun gpgme_sign_result_t gpgme_op_verify_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_verify_result} returns a @code{gpgme_verify_result_t} pointer to a structure holding the result of a @code{gpgme_op_verify} operation. The pointer is only valid if the last operation on the context was a @code{gpgme_op_verify} or @code{gpgme_op_verify_start} operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun The following interfaces are deprecated and only provided for backward compatibility. Don't use them. They will be removed in a future version of @acronym{GPGME}. @deftp {Data type} {enum gpgme_sig_stat_t} @tindex gpgme_sig_stat_t The @code{gpgme_sig_stat_t} type holds the result of a signature check, or the combined result of all signatures. The following results are possible: @table @code @item GPGME_SIG_STAT_NONE This status should not occur in normal operation. @item GPGME_SIG_STAT_GOOD This status indicates that the signature is valid. For the combined result this status means that all signatures are valid. @item GPGME_SIG_STAT_GOOD_EXP This status indicates that the signature is valid but expired. For the combined result this status means that all signatures are valid and expired. @item GPGME_SIG_STAT_GOOD_EXPKEY This status indicates that the signature is valid but the key used to verify the signature has expired. For the combined result this status means that all signatures are valid and all keys are expired. @item GPGME_SIG_STAT_BAD This status indicates that the signature is invalid. For the combined result this status means that all signatures are invalid. @item GPGME_SIG_STAT_NOKEY This status indicates that the signature could not be verified due to a missing key. For the combined result this status means that all signatures could not be checked due to missing keys. @item GPGME_SIG_STAT_NOSIG This status indicates that the signature data provided was not a real signature. @item GPGME_SIG_STAT_ERROR This status indicates that there was some other error which prevented the signature verification. @item GPGME_SIG_STAT_DIFF For the combined result this status means that at least two signatures have a different status. You can get each key's status with @code{gpgme_get_sig_status}. @end table @end deftp @deftypefun {const char *} gpgme_get_sig_status (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{idx}}, @w{gpgme_sig_stat_t *@var{r_stat}}, @w{time_t *@var{r_created}}) The function @code{gpgme_get_sig_status} is equivalent to: @example gpgme_verify_result_t result; gpgme_signature_t sig; result = gpgme_op_verify_result (ctx); sig = result->signatures; while (sig && idx) @{ sig = sig->next; idx--; @} if (!sig || idx) return NULL; if (r_stat) @{ switch (sig->status) @{ case GPGME_No_Error: *r_stat = GPGME_SIG_STAT_GOOD; break; case GPGME_Bad_Signature: *r_stat = GPGME_SIG_STAT_BAD; break; case GPGME_No_Public_Key: *r_stat = GPGME_SIG_STAT_NOKEY; break; case GPGME_No_Data: *r_stat = GPGME_SIG_STAT_NOSIG; break; case GPGME_Sig_Expired: *r_stat = GPGME_SIG_STAT_GOOD_EXP; break; case GPGME_Key_Expired: *r_stat = GPGME_SIG_STAT_GOOD_EXPKEY; break; default: *r_stat = GPGME_SIG_STAT_ERROR; break; @} @} if (r_created) *r_created = sig->timestamp; return sig->fpr; @end example @end deftypefun @deftypefun {const char *} gpgme_get_sig_string_attr (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{idx}}, @w{gpgme_attr_t @var{what}}, @w{int @var{whatidx}}) The function @code{gpgme_get_sig_string_attr} is equivalent to: @example gpgme_verify_result_t result; gpgme_signature_t sig; result = gpgme_op_verify_result (ctx); sig = result->signatures; while (sig && idx) @{ sig = sig->next; idx--; @} if (!sig || idx) return NULL; switch (what) @{ case GPGME_ATTR_FPR: return sig->fpr; case GPGME_ATTR_ERRTOK: if (whatidx == 1) return sig->wrong_key_usage ? "Wrong_Key_Usage" : ""; else return ""; default: break; @} return NULL; @end example @end deftypefun @deftypefun {const char *} gpgme_get_sig_ulong_attr (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{idx}}, @w{gpgme_attr_t @var{waht}}, @w{int @var{whatidx}}) The function @code{gpgme_get_sig_ulong_attr} is equivalent to: @example gpgme_verify_result_t result; gpgme_signature_t sig; result = gpgme_op_verify_result (ctx); sig = result->signatures; while (sig && idx) @{ sig = sig->next; idx--; @} if (!sig || idx) return 0; switch (what) @{ case GPGME_ATTR_CREATED: return sig->timestamp; case GPGME_ATTR_EXPIRE: return sig->exp_timestamp; case GPGME_ATTR_VALIDITY: return (unsigned long) sig->validity; case GPGME_ATTR_SIG_STATUS: switch (sig->status) @{ case GPGME_No_Error: return GPGME_SIG_STAT_GOOD; case GPGME_Bad_Signature: return GPGME_SIG_STAT_BAD; case GPGME_No_Public_Key: return GPGME_SIG_STAT_NOKEY; case GPGME_No_Data: return GPGME_SIG_STAT_NOSIG; case GPGME_Sig_Expired: return GPGME_SIG_STAT_GOOD_EXP; case GPGME_Key_Expired: return GPGME_SIG_STAT_GOOD_EXPKEY; default: return GPGME_SIG_STAT_ERROR; @} case GPGME_ATTR_SIG_SUMMARY: return sig->summary; default: break; @} return 0; @end example @end deftypefun @deftypefun {const char *} gpgme_get_sig_key (@w{gpgme_ctx_t @var{ctx}}, @w{int @var{idx}}, @w{gpgme_key_t *@var{r_key}}) The function @code{gpgme_get_sig_key} is equivalent to: @example gpgme_verify_result_t result; gpgme_signature_t sig; result = gpgme_op_verify_result (ctx); sig = result->signatures; while (sig && idx) @{ sig = sig->next; idx--; @} if (!sig || idx) return GPGME_EOF; return gpgme_get_key (ctx, sig->fpr, r_key, 0, 0); @end example @end deftypefun @node Decrypt and Verify @subsection Decrypt and Verify @cindex decryption and verification @cindex verification and decryption @cindex signature check @cindex cryptographic operation, decryption and verification @deftypefun gpgme_error_t gpgme_op_decrypt_verify (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{cipher}}, @w{gpgme_data_t @var{plain}}) The function @code{gpgme_op_decrypt_verify} decrypts the ciphertext in the data object @var{cipher} and stores it into the data object @var{plain}. If @var{cipher} contains signatures, they will be verified. After the operation completed, @code{gpgme_op_get_sig_status} and @code{gpgme_op_get_sig_key} can be used to retrieve more information about the signatures. The function returns @code{GPGME_No_Error} if the ciphertext could be decrypted successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{cipher}, @var{plain} or @var{r_stat} is not a valid pointer, @code{GPGME_No_Data} if @var{cipher} does not contain any data to decrypt, @code{GPGME_Decryption_Failed} if @var{cipher} is not a valid cipher text, @code{GPGME_Bad_Passphrase} if the passphrase for the secret key could not be retrieved, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_decrypt_verify (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{cipher}}, @w{gpgme_data_t @var{plain}}) The function @code{gpgme_op_decrypt_verify_start} initiates a @code{gpgme_op_decrypt_verify} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{cipher}, @var{plain} or @var{r_stat} is not a valid pointer, and @code{GPGME_No_Data} if @var{cipher} does not contain any data to decrypt. @end deftypefun @node Sign @subsection Sign @cindex signature, creation @cindex sign @cindex cryptographic operation, signing A signature can contain signatures by one or more keys. The set of keys used to create a signatures is contained in a context, and is applied to all following signing operations in this context (until the set is changed). @menu * Selecting Signers:: How to choose the keys to sign with. * Creating a Signature:: How to create a signature. @end menu @node Selecting Signers @subsubsection Selecting Signers @cindex signature, selecting signers @cindex signers, selecting @deftypefun void gpgme_signers_clear (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_signers_clear} releases a reference for each key on the signers list and removes the list of signers from the context @var{ctx}. Every context starts with an empty list. @end deftypefun @deftypefun gpgme_error_t gpgme_signers_add (@w{gpgme_ctx_t @var{ctx}}, @w{const gpgme_key_t @var{key}}) The function @code{gpgme_signers_add} adds the key @var{key} to the list of signers in the context @var{ctx}. Calling this function acquires an additional reference for the key. @end deftypefun @deftypefun gpgme_key_t gpgme_signers_enum (@w{const gpgme_ctx_t @var{ctx}}, @w{int @var{seq}}) The function @code{gpgme_signers_enum} returns the @var{seq}th key in the list of signers in the context @var{ctx}. An additional reference is acquired for the user. If @var{seq} is out of range, @code{NULL} is returned. @end deftypefun @node Creating a Signature @subsubsection Creating a Signature @deftp {Data type} {enum gpgme_sig_mode_t} @tindex gpgme_sig_mode_t The @code{gpgme_sig_mode_t} type is used to specify the desired type of a signature. The following modes are available: @table @code @item GPGME_SIG_MODE_NORMAL A normal signature is made, the output includes the plaintext and the signature. @item GPGME_SIG_MODE_DETACH A detached signature is made. @item GPGME_SIG_MODE_CLEAR A clear text signature is made. The @acronym{ASCII} armor and text mode settings of the context are ignored. @end table @end deftp @deftypefun gpgme_error_t gpgme_op_sign (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{sig}}, @w{gpgme_sig_mode_t @var{mode}}) The function @code{gpgme_op_sign} creates a signature for the text in the data object @var{plain} and returns it in the data object @var{sig}. The type of the signature created is determined by the @acronym{ASCII} armor and text mode attributes set for the context @var{ctx} and the requested signature mode @var{mode}. After the operation completed successfully, the result can be retrieved with @code{gpgme_op_sign_result}. If an S/MIME signed message is created using the CMS crypto engine, the number of certificates to include in the message can be specified with @code{gpgme_set_include_certs}. @xref{Included Certificates}. The function returns @code{GPGME_No_Error} if the signature could be created successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{plain} or @var{sig} is not a valid pointer, @code{GPGME_No_Data} if the signature could not be created, @code{GPGME_Bad_Passphrase} if the passphrase for the secret key could not be retrieved, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_sign_start (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{sig}}, @w{gpgme_sig_mode_t @var{mode}}) The function @code{gpgme_op_sign_start} initiates a @code{gpgme_op_sign} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, and @code{GPGME_Invalid_Value} if @var{ctx}, @var{plain} or @var{sig} is not a valid pointer. @end deftypefun @deftp {Data type} {gpgme_new_signature_t} This is a pointer to a structure used to store a part of the result of a @code{gpgme_op_sign} operation. The structure contains the following members: @table @code @item gpgme_new_signature_t next This is a pointer to the next new signature structure in the linked list, or @code{NULL} if this is the last element. @item gpgme_sig_mode_t type The type of this signature. @item gpgme_pubkey_algo_t The public key algorithm used to create this signature. @item gpgme_hash_algo_t The hash algorithm used to create this signature. @item unsigned long class The signature class of this signature. @item long int timestamp The creation timestamp of this signature. @item char *fpr The fingerprint of the key which was used to create this signature. @end table @end deftp @deftp {Data type} {gpgme_sign_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_sign} operation. After successfully generating a signature, you can retrieve the pointer to the result with @code{gpgme_op_sign_result}. The structure contains the following members: @table @code @item gpgme_invalid_user_id_t invalid_signers A linked list with information about all invalid user IDs for which a signature could not be created. @item gpgme_new_signature_t signatures A linked list with information about all signatures created. @end table @end deftp @deftypefun gpgme_sign_result_t gpgme_op_sign_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_sign_result} returns a @code{gpgme_sign_result_t} pointer to a structure holding the result of a @code{gpgme_op_sign} operation. The pointer is only valid if the last operation on the context was a @code{gpgme_op_sign} or @code{gpgme_op_sign_start} operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun @node Encrypt @subsection Encrypt @cindex encryption @cindex cryptographic operation, encryption One plaintext can be encrypted for several recipients at the same time. The list of recipients is created independently of any context, and then passed to the encryption operation. @menu * Encrypting a Plaintext:: How to encrypt a plaintext. @end menu @node Encrypting a Plaintext @subsubsection Encrypting a Plaintext @deftypefun gpgme_error_t gpgme_op_encrypt (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_key_t @var{recp}[]}, @w{gpgme_encrypt_flags_t @var{flags}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{cipher}}) The function @code{gpgme_op_encrypt} encrypts the plaintext in the data object @var{plain} for the recipients @var{recp} and stores the ciphertext in the data object @var{cipher}. The type of the ciphertext created is determined by the @acronym{ASCII} armor and text mode attributes set for the context @var{ctx}. @var{key} must be a @code{NULL}-terminated array of keys. The user must keep references for all keys during the whole duration of the call (but see @code{gpgme_op_encrypt_start} for the requirements with the asynchronous variant). The value in @var{flags} is a bitwise-or combination of one or multiple of the following bit values: @table @code @item GPGME_ENCRYPT_ALWAYS_TRUST The @code{GPGME_ENCRYPT_ALWAYS_TRUST} symbol specifies that all the recipients in @var{recp} should be trusted, even if the keys do not have a high enough validity in the keyring. This flag should be used with care; in general it is not a good idea to use any untrusted keys. @end table If @code{GPGME_Invalid_Key} is returned, some recipients in @var{recp} are invalid, but not all. In this case the plaintext might be encrypted for all valid recipients and returned in @var{cipher} (if this happens depends on the crypto engine). More information about the invalid recipients is available with @code{gpgme_op_encrypt_result}. If @var{recp} is @code{NULL}, symmetric rather than public key encryption is performed. Symmetrically encrypted cipher text can be deciphered with @code{gpgme_op_decrypt}. Note that in this case the crypto backend needs to retrieve a passphrase from the user. Symmetric encryption is currently only supported for the OpenPGP crypto backend. The function returns @code{GPGME_No_Error} if the ciphertext could be created successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{recp}, @var{plain} or @var{cipher} is not a valid pointer, @code{GPGME_Invalid_Key} if @var{recp} contains some invalid recipients, @code{GPGME_Bad_Passphrase} if the passphrase for the secret key could not be retrieved, and passes through any errors that are reported by the crypto engine support routines. @end deftypefun @deftypefun gpgme_error_t gpgme_op_encrypt_start (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_key_t @var{recp}[]}, @w{gpgme_encrypt_flags_t @var{flags}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{cipher}}) The function @code{gpgme_op_encrypt_start} initiates a @code{gpgme_op_encrypt} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. References to the keys only need to be held for the duration of this call. The user can release its references to the keys after this function returns, even if the operation is not yet finished. The function returns @code{GPGME_No_Error} if the operation could be started successfully, @code{GPGME_Invalid_Value} if @var{ctx}, @var{rset}, @var{plain} or @var{cipher} is not a valid pointer, and @code{GPGME_No_UserID} if @var{rset} does not contain any valid recipients. @end deftypefun @deftp {Data type} {gpgme_encrypt_result_t} This is a pointer to a structure used to store the result of a @code{gpgme_op_encrypt} operation. After successfully encrypting data, you can retrieve the pointer to the result with @code{gpgme_op_encrypt_result}. The structure contains the following members: @table @code @item gpgme_invalid_user_id_t invalid_recipients A linked list with information about all invalid user IDs for which the data could not be encrypted. @end table @end deftp @deftypefun gpgme_encrypt_result_t gpgme_op_encrypt_result (@w{gpgme_ctx_t @var{ctx}}) The function @code{gpgme_op_encrypt_result} returns a @code{gpgme_encrypt_result_t} pointer to a structure holding the result of a @code{gpgme_op_encrypt} operation. The pointer is only valid if the last operation on the context was a @code{gpgme_op_encrypt} or @code{gpgme_op_encrypt_start} operation, and if this operation finished successfully. The returned pointer is only valid until the next operation is started on the context. @end deftypefun @deftypefun gpgme_error_t gpgme_op_encrypt_sign (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_key_t @var{recp}[]}, @w{gpgme_encrypt_flags_t @var{flags}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{cipher}}) The function @code{gpgme_op_encrypt_sign} does a combined encrypt and sign operation. It is used like @code{gpgme_op_encrypt}, but the ciphertext also contains signatures for the signers listed in @var{ctx}. The combined encrypt and sign operation is currently only available for the OpenPGP crypto engine. @end deftypefun @deftypefun gpgme_error_t gpgme_op_encrypt_sign_start (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_key_t @var{recp}}, @w{gpgme_encrypt_flags_t @var{flags}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{cipher}}) The function @code{gpgme_op_encrypt_sign_start} initiates a @code{gpgme_op_encrypt_sign} operation. It can be completed by calling @code{gpgme_wait} on the context. @xref{Waiting For Completion}. The function returns @code{GPGME_No_Error} if the operation could be started successfully, and @code{GPGME_Invalid_Value} if @var{ctx}, @var{rset}, @var{plain} or @var{cipher} is not a valid pointer. @end deftypefun @node Run Control @section Run Control @cindex run control @cindex cryptographic operation, running @acronym{GPGME} supports running operations synchronously and asynchronously. You can use asynchronous operation to set up a context up to initiating the desired operation, but delay performing it to a later point. Furthermore, you can use an external event loop to control exactly when @acronym{GPGME} runs. This ensures that @acronym{GPGME} only runs when necessary and also prevents it from blocking for a long time. @menu * Waiting For Completion:: Waiting until an operation is completed. * Using External Event Loops:: Advanced control over what happens when. @end menu @node Waiting For Completion @subsection Waiting For Completion @cindex cryptographic operation, wait for @cindex wait for completion @deftypefun gpgme_ctx_t gpgme_wait (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_error_t *@var{status}}, @w{int @var{hang}}) The function @code{gpgme_wait} continues the pending operation within the context @var{ctx}. In particular, it ensures the data exchange between @acronym{GPGME} and the crypto backend and watches over the run time status of the backend process. If @var{hang} is true, the function does not return until the operation is completed or cancelled. Otherwise the function will not block for a long time. The error status of the finished operation is returned in @var{status} if @code{gpgme_wait} does not return @code{NULL}. The @var{ctx} argument can be @code{NULL}. In that case, @code{gpgme_wait} waits for any context to complete its operation. @code{gpgme_wait} can be used only in conjunction with any context that has a pending operation initiated with one of the @code{gpgme_op_*_start} functions except @code{gpgme_op_keylist_start} and @code{gpgme_op_trustlist_start} (for which you should use the corresponding @code{gpgme_op_*_next} functions). If @var{ctx} is @code{NULL}, all of such contexts are waited upon and possibly returned. Synchronous operations running in parallel, as well as key and trust item list operations, do not affect @code{gpgme_wait}. In a multi-threaded environment, only one thread should ever call @code{gpgme_wait} at any time, irregardless if @var{ctx} is specified or not. This means that all calls to this function should be fully synchronized by locking primitives. It is safe to start asynchronous operations while a thread is running in @code{gpgme_wait}. The function returns the @var{ctx} of the context which has finished the operation. If @var{hang} is false, and the timeout expires, @code{NULL} is returned and @code{*status} will be set to 0. If an error occurs, @code{NULL} is returned and the error is returned in @code{*status}. @end deftypefun @node Using External Event Loops @subsection Using External Event Loops @cindex event loop, external @acronym{GPGME} hides the complexity of the communication between the library and the crypto engine. The price of this convenience is that the calling thread can block arbitrary long waiting for the data returned by the crypto engine. In single-threaded programs, in particular if they are interactive, this is an unwanted side-effect. OTOH, if @code{gpgme_wait} is used without the @var{hang} option being enabled, it might be called unnecessarily often, wasting CPU time that could be used otherwise. The I/O callback interface described in this section lets the user take control over what happens when. @acronym{GPGME} will provide the user with the file descriptors that should be monitored, and the callback functions that should be invoked when a file descriptor is ready for reading or writing. It is then the user's responsibility to decide when to check the file descriptors and when to invoke the callback functions. Usually this is done in an event loop, that also checks for events in other parts of the program. If the callback functions are only called when the file descriptors are ready, @acronym{GPGME} will never block. This gives the user mroe control over the program flow, and allows to perform other tasks when @acronym{GPGME} would block otherwise. By using this advanced mechanism, @acronym{GPGME} can be integrated smoothly into GUI toolkits like GTK+ even for single-threaded programs. @menu * I/O Callback Interface:: How I/O callbacks are registered. * Registering I/O Callbacks:: How to use I/O callbacks for a context. * I/O Callback Example:: An example how to use I/O callbacks. * I/O Callback Example GTK+:: How to use @acronym{GPGME} with GTK+. * I/O Callback Example GDK:: How to use @acronym{GPGME} with GDK. @end menu @node I/O Callback Interface @subsubsection I/O Callback Interface @deftp {Data type} {gpgme_error_t (*gpgme_io_cb_t) (@w{void *@var{data}}, @w{int @var{fd}})} @tindex gpgme_io_cb_t The @code{gpgme_io_cb_t} type is the type of functions which @acronym{GPGME} wants to register as I/O callback handlers using the @code{gpgme_register_io_cb_t} functions provided by the user. @var{data} and @var{fd} are provided by @acronym{GPGME} when the I/O callback handler is registered, and should be passed through to the handler when it is invoked by the user because it noticed activity on the file descriptor @var{fd}. The callback handler always returns @code{0}, but you should consider the return value to be reserved for later use. @end deftp @deftp {Data type} {gpgme_error_t (*gpgme_register_io_cb_t) (@w{void *@var{data}}, @w{int @var{fd}}, @w{int @var{dir}}, @w{gpgme_io_cb_t @var{fnc}}, @w{void *@var{fnc_data}}, @w{void **@var{tag}})} @tindex gpgme_register_io_cb_t The @code{gpgme_register_io_cb_t} type is the type of functions which can be called by @acronym{GPGME} to register an I/O callback funtion @var{fnc} for the file descriptor @var{fd} with the user. @var{fnc_data} should be passed as the first argument to @var{fnc} when the handler is invoked (the second argument should be @var{fd}). If @var{dir} is 0, @var{fnc} should be called by the user when @var{fd} is ready for writing. If @var{dir} is 1, @var{fnc} should be called when @var{fd} is ready for reading. @var{data} was provided by the user when registering the @code{gpgme_register_io_cb_t} function with @acronym{GPGME} and will always be passed as the first argument when registering a callback function. For example, the user can use this to determine the event loop to which the file descriptor should be added. @acronym{GPGME} will call this function when a crypto operation is initiated in a context for which the user has registered I/O callback handler functions with @code{gpgme_set_io_cbs}. It can also call this function when it is in an I/O callback handler for a file descriptor associated to this context. The user should return a unique handle in @var{tag} identifying this I/O callback registration, which will be passed to the @code{gpgme_register_io_cb_t} function without interpretation when the file descriptor should not be monitored anymore. @end deftp @deftp {Data type} {void (*gpgme_remove_io_cb_t) (@w{void *@var{tag}})} The @code{gpgme_remove_io_cb_t} type is the type of functions which can be called by @acronym{GPGME} to remove an I/O callback handler that was registered before. @var{tag} is the handle that was returned by the @code{gpgme_register_io_cb_t} for this I/O callback. @acronym{GPGME} can call this function when a crypto operation is in an I/O callback. It will also call this function when the context is destroyed while an operation is pending. @end deftp @deftp {Data type} {enum gpgme_event_io_t} @tindex gpgme_event_io_t The @code{gpgme_event_io_t} type specifies the type of an event that is reported to the user by @acronym{GPGME} as a consequence of an I/O operation. The following events are defined: @table @code @item GPGME_EVENT_START The operation is fully initialized now, and you can start to run the registered I/O callback handlers now. Note that registered I/O callback handlers must not be run before this event is signalled. @var{type_data} is @code{NULL} and reserved for later use. @item GPGME_EVENT_DONE The operation is finished, the last I/O callback for this operation was removed. The accompanying @var{type_data} points to a @code{gpgme_error_t} variable that contains the status of the operation that finished. This event is signalled after the last I/O callback has been removed. @item GPGME_EVENT_NEXT_KEY In a @code{gpgme_op_keylist_start} operation, the next key was received from the crypto engine. The accompanying @var{type_data} is a @code{gpgme_key_t} variable that contains the key with one reference for the user. @item GPGME_EVENT_NEXT_TRUSTITEM In a @code{gpgme_op_trustlist_start} operation, the next trust item was received from the crypto engine. The accompanying @var{type_data} is a @code{gpgme_trust_item_t} variable that contains the trust item with one reference for the user. @end table @end deftp @deftp {Data type} {void (*gpgme_event_io_cb_t) (@w{void *@var{data}}, @w{gpgme_event_io_t @var{type}}, @w{void *@var{type_data}})} The @code{gpgme_event_io_cb_t} type is the type of functions which can be called by @acronym{GPGME} to signal an event for an operation running in a context which has I/O callback functions registered by the user. @var{data} was provided by the user when registering the @code{gpgme_event_io_cb_t} function with @acronym{GPGME} and will always be passed as the first argument when registering a callback function. For example, the user can use this to determine the context in which this event has occured. @var{type} will specify the type of event that has occured. @var{type_data} specifies the event further, as described in the above list of possible @code{gpgme_event_io_t} types. @acronym{GPGME} can call this function in an I/O callback handler. @end deftp @node Registering I/O Callbacks @subsubsection Registering I/O Callbacks @deftp {Data type} {struct gpgme_io_cb_ts} @tindex gpgme_event_io_t This structure is used to store the I/O callback interface functions described in the previous section. It has the following members: @table @code @item gpgme_register_io_cb_t add This is the function called by @acronym{GPGME} to register an I/O callback handler. It must be specified. @item void *add_data This is passed as the first argument to the @code{add} function when it is called by @acronym{GPGME}. For example, it can be used to determine the event loop to which the file descriptor should be added. @item gpgme_remove_io_cb_t remove This is the function called by @acronym{GPGME} to remove an I/O callback handler. It must be specified. @item gpgme_event_io_cb_t event This is the function called by @acronym{GPGME} to signal an event for an operation. It is optional, but if you don't specify it, you can not retrieve the return value of the operation. @item void *event_data This is passed as the first argument to the @code{event} function when it is called by @acronym{GPGME}. For example, it can be used to determine the context in which the event has occured. @end table @end deftp @deftypefun void gpgme_set_io_cbs (@w{gpgme_ctx_t @var{ctx}}, @w{struct gpgme_io_cb_ts *@var{io_cbs}}) The function @code{gpgme_set_io_cbs} enables the I/O callback interface for the context @var{ctx}. The I/O callback functions are specified by @var{io_cbs}. If @var{io_cbs}->@code{add} is @code{NULL}, the I/O callback interface is disabled for the context, and normal operation is restored. @end deftypefun @deftypefun void gpgme_get_io_cbs (@w{gpgme_ctx_t @var{ctx}}, @w{struct gpgme_io_cb_ts *@var{io_cbs}}) The function @code{gpgme_get_io_cbs} returns the I/O callback functions set with @code{gpgme_set_io_cbs} in @var{io_cbs}. @end deftypefun @node I/O Callback Example @subsubsection I/O Callback Example To actually use an external event loop, you have to implement the I/O callback functions that are used by @acronym{GPGME} to register and unregister file descriptors. Furthermore, you have to actually monitor these file descriptors for activity and call the appropriate I/O callbacks. The following example illustrates how to do that. The example uses locking to show in which way the the callbacks and the event loop can run concurrently. For the event loop, we use a fixed array. For a real-world implementation, you should use a dynamically sized structure because the number of file descriptors needed for a crypto operation in @acronym{GPGME} is not predictable. @example #include #include #include /* The following structure holds the result of a crypto operation. */ struct op_result @{ int done; gpgme_error_t err; @}; /* The following structure holds the data associated with one I/O callback. */ struct one_fd @{ int fd; int dir; gpgme_io_cb_t fnc; void *fnc_data; @}; struct event_loop @{ pthread_mutex_t lock; #define MAX_FDS 32 /* Unused slots are marked with FD being -1. */ struct one_fd fds[MAX_FDS]; @}; @end example The following functions implement the I/O callback interface. @example gpgme_error_t add_io_cb (void *data, int fd, int dir, gpgme_io_cb_t fnc, void *fnc_data, void **r_tag) @{ struct event_loop *loop = data; struct one_fd *fds = loop->fds; int i; pthread_mutex_lock (&loop->lock); for (i = 0; i < MAX_FDS; i++) @{ if (fds[i].fd == -1) @{ fds[i].fd = fd; fds[i].dir = dir; fds[i].fnc = fnc; fds[i].fnc_data = fnc_data; break; @} @} pthread_mutex_unlock (&loop->lock); if (i == MAX_FDS) return GPGME_General_Error; *r_tag = &fds[i]; return 0; @} void remove_io_cb (void *tag) @{ struct one_fd *fd = tag; pthread_mutex_lock (&loop->lock); fd->fd = -1; pthread_mutex_unlock (&loop->lock); @} void event_io_cb (void *data, gpgme_event_io_t type, void *type_data) @{ struct op_result *result = data; gpgme_error_t *err = data; /* We don't support list operations here. */ if (type == GPGME_EVENT_DONE) @{ result->done = 1; result->err = *data; @} @} @end example The final missing piece is the event loop, which will be presented next. We only support waiting for the success of a single operation. @example int do_select (struct event_loop *loop) @{ fd_set rfds; fd_set wfds; int i, n; int any = 0; pthread_mutex_lock (&loop->lock); FD_ZERO (&rfds); FD_ZERO (&wfds); for (i = 0; i < FDLIST_MAX; i++) if (fdlist[i].fd != -1) FD_SET (fdlist[i].fd, fdlist[i].dir ? &rfds : &wfds); pthread_mutex_unlock (&loop->unlock); do @{ n = select (FD_SETSIZE, &rfds, &wfds, NULL, 0); @} while (n < 0 && errno == EINTR); if (n < 0) return n; /* Error or timeout. */ pthread_mutex_lock (&loop->lock); for (i = 0; i < FDLIST_MAX && n; i++) @{ if (fdlist[i].fd != -1) @{ if (FD_ISSET (fdlist[i].fd, fdlist[i].dir ? &rfds : &wfds)) @{ assert (n); n--; any = 1; /* The I/O callback handler can register/remove callbacks, so we have to unlock the file descriptor list. */ pthread_mutex_unlock (&loop->lock); (*fdlist[i].fnc) (fdlist[i].fnc_data, fdlist[i].fd); pthread_mutex_lock (&loop->lock); @} @} @} pthread_mutex_unlock (&loop->lock); return any; @} void wait_for_op (struct event_loop *loop, struct op_result *result) @{ int ret; do @{ ret = do_select (loop); @} while (ret >= 0 && !result->done); return ret; @} @end example The main function shows how to put it all together. @example int main (int argc, char *argv[]) @{ struct event_loop loop; struct op_result result; gpgme_ctx_t ctx; gpgme_error_t err; gpgme_data_t sig, text; gpgme_sig_stat_t status; int i; struct gpgme_io_cb_ts io_cbs = @{ add_io_cb, &loop, remove_io_cb, event_io_cb, &result @}; /* Initialize the loop structure. */ loop.lock = PTHREAD_MUTEX_INITIALIZER; for (i = 0; i < MAX_FDS; i++) loop->fds[i].fd = -1; /* Initialize the result structure. */ result.done = 0; err = gpgme_data_new_from_file (&sig, "signature", 1); if (!err) err = gpgme_data_new_from_file (&text, "text", 1); if (!err) err = gpgme_new (&ctx); if (!err) @{ gpgme_set_io_cbs (ctx, &io_cbs); err = gpgme_op_verify_start (ctx, sig, text, &status); @} if (err) @{ fprintf (stderr, "gpgme error: %s\n", gpgme_strerror (err)); exit (1); @} wait_for_op (&loop, &result); if (!result.done) @{ fprintf (stderr, "select error\n"); exit (1); @} if (!result.err) @{ fprintf (stderr, "verification failed: %s\n", gpgme_strerror (result.err)); exit (1); @} /* Evaluate STATUS. */ @dots{} return 0; @} @end example @node I/O Callback Example GTK+ @subsubsection I/O Callback Example GTK+ @cindex GTK+, using @acronym{GPGME} with The I/O callback interface can be used to integrate @acronym{GPGME} with the GTK+ event loop. The following code snippets shows how this can be done using the appropriate register and remove I/O callback functions. In this example, the private data of the register I/O callback function is unused. The event notifications is missing because it does not require any GTK+ specific setup. @example #include struct my_gpgme_io_cb @{ gpgme_io_cb_t fnc; void *fnc_data; guint input_handler_id @}; void my_gpgme_io_cb (gpointer data, gint source, GdkInputCondition condition) @{ struct my_gpgme_io_cb *iocb = data; (*(iocb->fnc)) (iocb->data, source); @} void my_gpgme_remove_io_cb (void *data) @{ struct my_gpgme_io_cb *iocb = data; gtk_input_remove (data->input_handler_id); @} void my_gpgme_register_io_callback (void *data, int fd, int dir, gpgme_io_cb_t fnc, void *fnc_data, void **tag) @{ struct my_gpgme_io_cb *iocb = g_malloc (sizeof (struct my_gpgme_io_cb)); iocb->fnc = fnc; iocb->data = fnc_data; iocb->input_handler_id = gtk_input_add_full (fd, dir ? GDK_INPUT_READ : GDK_INPUT_WRITE, my_gpgme_io_callback, 0, iocb, NULL); *tag = iocb; return 0; @} @end example @node I/O Callback Example GDK @subsubsection I/O Callback Example GDK @cindex GDK, using @acronym{GPGME} with The I/O callback interface can also be used to integrate @acronym{GPGME} with the GDK event loop. The following code snippets shows how this can be done using the appropriate register and remove I/O callback functions. In this example, the private data of the register I/O callback function is unused. The event notifications is missing because it does not require any GDK specific setup. It is very similar to the GTK+ example in the previous section. @example #include struct my_gpgme_io_cb @{ gpgme_io_cb_t fnc; void *fnc_data; gint tag; @}; void my_gpgme_io_cb (gpointer data, gint source, GdkInputCondition condition) @{ struct my_gpgme_io_cb *iocb = data; (*(iocb->fnc)) (iocb->data, source); @} void my_gpgme_remove_io_cb (void *data) @{ struct my_gpgme_io_cb *iocb = data; gdk_input_remove (data->tag); @} void my_gpgme_register_io_callback (void *data, int fd, int dir, gpgme_io_cb_t fnc, void *fnc_data, void **tag) @{ struct my_gpgme_io_cb *iocb = g_malloc (sizeof (struct my_gpgme_io_cb)); iocb->fnc = fnc; iocb->data = fnc_data; iocb->tag = gtk_input_add_full (fd, dir ? GDK_INPUT_READ : GDK_INPUT_WRITE, my_gpgme_io_callback, iocb, NULL); *tag = iocb; return 0; @} @end example @include gpl.texi @include fdl.texi @node Concept Index @unnumbered Concept Index @printindex cp @node Function and Data Index @unnumbered Function and Data Index @printindex fn @summarycontents @contents @bye