core: Support direct encryption of file with gpg

* src/gpgme.h.in (GPGME_ENCRYPT_FILE): New encryption flag.
* src/engine-gpg.c (gpg_encrypt, gpg_encrypt_sign): Check for
incompatible flags. Pass filename instead of fd to gpg when new flag is
set.
* src/engine-gpgsm.c (gpgsm_encrypt): Return error if new flag is set.
* src/engine-uiserver.c (uiserver_encrypt): Ditto.

* tests/run-encrypt.c (show_usage): New option --direct-file-io.
(main): Parse new option. Make gpg read the input file itself if the
option is given.
--

With this change the gpgme_op_encrypt* and gpgme_op_encrypt_sign*
functions gain the possibility to make gpg read the data to (sign and)
encrypt directly from a file instead of from an input FD to which it is
written by gpgme.

GnuPG-bug-id: 6550

1 files changed, 17 insertions, 1 deletions

diff --git a/doc/gpgme.texi b/doc/gpgme.texi
index 11f90133..0ec70a55 100644
--- a/doc/gpgme.texi
+++ b/doc/gpgme.texi
@@ -6557,7 +6557,14 @@ file set with @code{gpgme_data_set_file_name} for the data object
 @var{cipher}.  The type of the ciphertext created is determined by the
 @acronym{ASCII} armor (or, if that is not set, by the encoding specified
 for @var{cipher}) and the text mode attributes set for the context
-@var{ctx}.
+@var{ctx}.  If a filename has been set with @code{gpgme_data_set_file_name}
+for the data object @var{plain} then this filename is stored in the
+ciphertext.
+
+If the flag @code{GPGME_ENCRYPT_FILE} is set and a filename has been set
+with @code{gpgme_data_set_file_name} for the data object @var{plain},
+then this filename is passed to gpg, so that gpg reads the plaintext
+directly from this file instead of from the data object @var{plain}.
 
 If the flag @code{GPGME_ENCRYPT_ARCHIVE} is set, then an encrypted
 archive is created from the files and directories given as NUL-separated
@@ -6653,6 +6660,15 @@ NUL-separated list of file paths and directory paths that shall be
 encrypted into an archive.  This feature is currently only supported
 for the OpenPGP crypto engine and requires GnuPG 2.4.1.
 
+@item GPGME_ENCRYPT_FILE
+@since{1.24.0}
+
+The @code{GPGME_ENCRYPT_FILE} symbol specifies that the filename set
+with @code{gpgme_data_set_file_name} for the data object @var{plain}
+is passed to gpg, so that gpg reads the plaintext directly from this
+file instead of from the data object @var{plain}.  This feature is
+currently only supported for the OpenPGP crypto engine.
+
 @end table
 
 If @code{GPG_ERR_UNUSABLE_PUBKEY} is returned, some recipients in