d7c5366d58
* Another retrofitting of the HOWTO Python example code, this time following adjustments to python-mode configuration and having trawled through the org-mode mailing lists for clues.
1768 lines
52 KiB
Org Mode
1768 lines
52 KiB
Org Mode
#+TITLE: GNU Privacy Guard (GnuPG) Made Easy Python Bindings HOWTO (English)
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#+AUTHOR: Ben McGinnes
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#+LATEX_COMPILER: xelatex
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#+LATEX_CLASS: article
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#+LATEX_CLASS_OPTIONS: [12pt]
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#+LATEX_HEADER: \usepackage{xltxtra}
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#+LATEX_HEADER: \usepackage[margin=1in]{geometry}
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#+LATEX_HEADER: \setmainfont[Ligatures={Common}]{Times New Roman}
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#+LATEX_HEADER: \author{Ben McGinnes <ben@gnupg.org>}
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#+HTML_HEAD_EXTRA: <link type="application/rss+xml" href="https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gpgme.git;a=rss;f=lang/python/docs/GPGMEpythonHOWTOen.org"/>
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* Introduction
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:PROPERTIES:
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:CUSTOM_ID: intro
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:END:
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| Version: | 0.1.3 |
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| Author: | Ben McGinnes <ben@gnupg.org> |
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| Author GPG Key: | DB4724E6FA4286C92B4E55C4321E4E2373590E5D |
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| Language: | Australian English, British English |
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| xml:lang: | en-AU, en-GB, en |
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This document provides basic instruction in how to use the GPGME
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Python bindings to programmatically leverage the GPGME library.
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** Python 2 versus Python 3
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:PROPERTIES:
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:CUSTOM_ID: py2-vs-py3
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:END:
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Though the GPGME Python bindings themselves provide support for both
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Python 2 and 3, the focus is unequivocally on Python 3 and
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specifically from Python 3.4 and above. As a consequence all the
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examples and instructions in this guide use Python 3 code.
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Much of it will work with Python 2, but much of it also deals with
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Python 3 byte literals, particularly when reading and writing data.
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Developers concentrating on Python 2.7, and possibly even 2.6, will
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need to make the appropriate modifications to support the older string
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and unicode types as opposed to bytes.
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There are multiple reasons for concentrating on Python 3; some of
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which relate to the immediate integration of these bindings, some of
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which relate to longer term plans for both GPGME and the python
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bindings and some of which relate to the impending EOL period for
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Python 2.7. Essentially, though, there is little value in tying the
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bindings to a version of the language which is a dead end and the
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advantages offered by Python 3 over Python 2 make handling the data
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types with which GPGME deals considerably easier.
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** Examples
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:PROPERTIES:
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:CUSTOM_ID: howto-python3-examples
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:END:
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All of the examples found in this document can be found as Python 3
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scripts in the =lang/python/examples/howto= directory.
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* GPGME Concepts
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:PROPERTIES:
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:CUSTOM_ID: gpgme-concepts
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:END:
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** A C API
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:PROPERTIES:
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:CUSTOM_ID: gpgme-c-api
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:END:
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Unlike many modern APIs with which programmers will be more familiar
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with these days, the GPGME API is a C API. The API is intended for
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use by C coders who would be able to access its features by including
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the =gpgme.h= header file with their own C source code and then access
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its functions just as they would any other C headers.
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This is a very effective method of gaining complete access to the API
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and in the most efficient manner possible. It does, however, have the
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drawback that it cannot be directly used by other languages without
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some means of providing an interface to those languages. This is
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where the need for bindings in various languages stems.
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** Python bindings
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:PROPERTIES:
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:CUSTOM_ID: gpgme-python-bindings
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:END:
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The Python bindings for GPGME provide a higher level means of
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accessing the complete feature set of GPGME itself. It also provides
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a more pythonic means of calling these API functions.
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The bindings are generated dynamically with SWIG and the copy of
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=gpgme.h= generated when GPGME is compiled.
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This means that a version of the Python bindings is fundamentally tied
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to the exact same version of GPGME used to generate that copy of
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=gpgme.h=.
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** Difference between the Python bindings and other GnuPG Python packages
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:PROPERTIES:
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:CUSTOM_ID: gpgme-python-bindings-diffs
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:END:
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There have been numerous attempts to add GnuPG support to Python over
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the years. Some of the most well known are listed here, along with
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what differentiates them.
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*** The python-gnupg package maintained by Vinay Sajip
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:PROPERTIES:
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:CUSTOM_ID: diffs-python-gnupg
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:END:
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This is arguably the most popular means of integrating GPG with
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Python. The package utilises the =subprocess= module to implement
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wrappers for the =gpg= and =gpg2= executables normally invoked on the
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command line (=gpg.exe= and =gpg2.exe= on Windows).
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The popularity of this package stemmed from its ease of use and
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capability in providing the most commonly required features.
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Unfortunately it has been beset by a number of security issues in the
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past; most of which stemmed from using unsafe methods of accessing the
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command line via the =subprocess= calls. While some effort has been
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made over the last two to three years (as of 2018) to mitigate this,
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particularly by no longer providing shell access through those
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subprocess calls, the wrapper is still somewhat limited in the scope
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of its GnuPG features coverage.
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The python-gnupg package is available under the MIT license.
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*** The gnupg package created and maintained by Isis Lovecruft
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:PROPERTIES:
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:CUSTOM_ID: diffs-isis-gnupg
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:END:
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In 2015 Isis Lovecruft from the Tor Project forked and then
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re-implemented the python-gnupg package as just gnupg. This new
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package also relied on subprocess to call the =gpg= or =gpg2=
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binaries, but did so somewhat more securely.
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The naming and version numbering selected for this package, however,
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resulted in conflicts with the original python-gnupg and since its
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functions were called in a different manner to python-gnupg, the
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release of this package also resulted in a great deal of consternation
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when people installed what they thought was an upgrade that
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subsequently broke the code relying on it.
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The gnupg package is available under the GNU General Public License
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version 3.0 (or any later version).
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*** The PyME package maintained by Martin Albrecht
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:PROPERTIES:
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:CUSTOM_ID: diffs-pyme
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:END:
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This package is the origin of these bindings, though they are somewhat
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different now. For details of when and how the PyME package was
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folded back into GPGME itself see the /Short History/ document[fn:1]
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in the Python bindings =docs= directory.[fn:2]
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The PyME package was first released in 2002 and was also the first
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attempt to implement a low level binding to GPGME. In doing so it
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provided access to considerably more functionality than either the
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=python-gnupg= or =gnupg= packages.
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The PyME package is only available for Python 2.6 and 2.7.
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Porting the PyME package to Python 3.4 in 2015 is what resulted in it
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being folded into the GPGME project and the current bindings are the
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end result of that effort.
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The PyME package is available under the same dual licensing as GPGME
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itself: the GNU General Public License version 2.0 (or any later
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version) and the GNU Lesser General Public License version 2.1 (or any
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later version).
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* GPGME Python bindings installation
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:PROPERTIES:
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:CUSTOM_ID: gpgme-python-install
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:END:
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** No PyPI
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:PROPERTIES:
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:CUSTOM_ID: do-not-use-pypi
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:END:
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Most third-party Python packages and modules are available and
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distributed through the Python Package Installer, known as PyPI.
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Due to the nature of what these bindings are and how they work, it is
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infeasible to install the GPGME Python bindings in the same way.
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This is because the bindings use SWIG to dynamically generate C
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bindings against =gpgme.h= and =gpgme.h= is generated from
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=gpgme.h.in= at compile time when GPGME is built from source. Thus to
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include a package in PyPI which actually built correctly would require
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either statically built libraries for every architecture bundled with
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it or a full implementation of C for each architecture.
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** Requirements
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:PROPERTIES:
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:CUSTOM_ID: gpgme-python-requirements
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:END:
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The GPGME Python bindings only have three requirements:
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1. A suitable version of Python 2 or Python 3. With Python 2 that
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means Python 2.7 and with Python 3 that means Python 3.4 or higher.
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2. SWIG.
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3. GPGME itself. Which also means that all of GPGME's dependencies
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must be installed too.
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** Installation
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:PROPERTIES:
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:CUSTOM_ID: installation
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:END:
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Installing the Python bindings is effectively achieved by compiling
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and installing GPGME itself.
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Once SWIG is installed with Python and all the dependencies for GPGME
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are installed you only need to confirm that the version(s) of Python
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you want the bindings installed for are in your =$PATH=.
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By default GPGME will attempt to install the bindings for the most
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recent or highest version number of Python 2 and Python 3 it detects
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in =$PATH=. It specifically checks for the =python= and =python3=
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executables first and then checks for specific version numbers.
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For Python 2 it checks for these executables in this order: =python=,
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=python2= and =python2.7=.
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For Python 3 it checks for these executables in this order: =python3=,
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=python3.6=, =python3.5=, =python3.4= and =python3.7=.[fn:4]
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*** Installing GPGME
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:PROPERTIES:
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:CUSTOM_ID: install-gpgme
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:END:
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See the GPGME =README= file for details of how to install GPGME from
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source.
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* Fundamentals
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:PROPERTIES:
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:CUSTOM_ID: howto-fund-a-mental
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:END:
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Before we can get to the fun stuff, there are a few matters regarding
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GPGME's design which hold true whether you're dealing with the C code
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directly or these Python bindings.
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** No REST
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:PROPERTIES:
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:CUSTOM_ID: no-rest-for-the-wicked
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:END:
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The first part of which is or will be fairly blatantly obvious upon
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viewing the first example, but it's worth reiterating anyway. That
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being that this API is /*not*/ a REST API. Nor indeed could it ever
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be one.
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Most, if not all, Python programmers (and not just Python programmers)
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know how easy it is to work with a RESTful API. In fact they've
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become so popular that many other APIs attempt to emulate REST-like
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behaviour as much as they are able. Right down to the use of JSON
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formatted output to facilitate the use of their API without having to
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retrain developers.
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This API does not do that. It would not be able to do that and also
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provide access to the entire C API on which it's built. It does,
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however, provide a very pythonic interface on top of the direct
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bindings and it's this pythonic layer with which this HOWTO deals
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with.
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** Context
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:PROPERTIES:
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:CUSTOM_ID: howto-get-context
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:END:
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One of the reasons which prevents this API from being RESTful is that
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most operations require more than one instruction to the API to
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perform the task. Sure, there are certain functions which can be
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performed simultaneously, particularly if the result known or strongly
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anticipated (e.g. selecting and encrypting to a key known to be in the
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public keybox).
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There are many more, however, which cannot be manipulated so readily:
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they must be performed in a specific sequence and the result of one
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operation has a direct bearing on the outcome of subsequent
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operations. Not merely by generating an error either.
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When dealing with this type of persistent state on the web, full of
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both the RESTful and REST-like, it's most commonly referred to as a
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session. In GPGME, however, it is called a context and every
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operation type has one.
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* Working with keys
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:PROPERTIES:
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:CUSTOM_ID: howto-keys
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:END:
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** Key selection
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:PROPERTIES:
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:CUSTOM_ID: howto-keys-selection
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:END:
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Selecting keys to encrypt to or to sign with will be a common
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occurrence when working with GPGMe and the means available for doing
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so are quite simple.
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They do depend on utilising a Context; however once the data is
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recorded in another variable, that Context does not need to be the
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same one which subsequent operations are performed.
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The easiest way to select a specific key is by searching for that
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key's key ID or fingerprint, preferably the full fingerprint without
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any spaces in it. A long key ID will probably be okay, but is not
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advised and short key IDs are already a problem with some being
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generated to match specific patterns. It does not matter whether the
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pattern is upper or lower case.
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So this is the best method:
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#+begin_src python -i
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import gpg
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k = gpg.Context().keylist(pattern="258E88DCBD3CD44D8E7AB43F6ECB6AF0DEADBEEF")
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keys = list(k)
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#+end_src
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This is passable and very likely to be common:
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#+begin_src python -i
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import gpg
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k = gpg.Context().keylist(pattern="0x6ECB6AF0DEADBEEF")
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keys = list(k)
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#+end_src
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And this is a really bad idea:
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#+begin_src python -i
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import gpg
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k = gpg.Context().keylist(pattern="0xDEADBEEF")
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keys = list(k)
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#+end_src
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Alternatively it may be that the intention is to create a list of keys
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which all match a particular search string. For instance all the
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addresses at a particular domain, like this:
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#+begin_src python -i
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import gpg
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ncsc = gpg.Context().keylist(pattern="ncsc.mil")
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nsa = list(ncsc)
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#+end_src
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*** Counting keys
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:PROPERTIES:
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:CUSTOM_ID: howto-keys-counting
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:END:
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Counting the number of keys in your public keybox (=pubring.kbx=), the
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format which has superseded the old keyring format (=pubring.gpg= and
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=secring.gpg=), or the number of secret keys is a very simple task.
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#+begin_src python -i
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import gpg
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c = gpg.Context()
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seckeys = c.keylist(pattern=None, secret=True)
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pubkeys = c.keylist(pattern=None, secret=False)
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seclist = list(seckeys)
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secnum = len(seclist)
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publist = list(pubkeys)
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pubnum = len(publist)
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print("""
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Number of secret keys: {0}
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Number of public keys: {1}
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""".format(secnum, pubnum))
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#+end_src
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** Get key
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:PROPERTIES:
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:CUSTOM_ID: howto-get-key
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:END:
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An alternative method of getting a single key via its fingerprint is
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available directly within a Context with =Context().get_key=. This is
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the preferred method of selecting a key in order to modify it, sign or
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certify it and for obtaining relevant data about a single key as a
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part of other functions; when verifying a signature made by that key,
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for instance.
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By default this method will select public keys, but it can select
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secret keys as well.
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This first example demonstrates selecting the current key of Werner
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Koch, which is due to expire at the end of 2018:
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#+begin_src python -i
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import gpg
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fingerprint = "80615870F5BAD690333686D0F2AD85AC1E42B367"
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key = gpg.Context().get_key(fingerprint)
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#+end_src
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Whereas this example demonstrates selecting the author's current key
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with the =secret= key word argument set to =True=:
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#+begin_src python -i
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import gpg
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fingerprint = "DB4724E6FA4286C92B4E55C4321E4E2373590E5D"
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key = gpg.Context().get_key(fingerprint, secret=True)
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#+end_src
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It is, of course, quite possible to select expired, disabled and
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revoked keys with this function, but only to effectively display
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information about those keys.
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It is also possible to use both unicode or string literals and byte
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literals with the fingerprint when getting a key in this way.
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** Importing keys
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:PROPERTIES:
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:CUSTOM_ID: howto-import-key
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:END:
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Importing keys is possible with the =key_import()= method and takes
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one argument which is a bytes literal object containing either the
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binary or ASCII armoured key data for one or more keys.
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The following example retrieves one or more keys from the SKS
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keyservers via the web using the requests module. Since requests
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returns the content as a bytes literal object, we can then use that
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directly to import the resulting data into our keybox.
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#+begin_src python -i
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import gpg
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import os.path
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import requests
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c = gpg.Context()
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url = "https://sks-keyservers.net/pks/lookup"
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pattern = input("Enter the pattern to search for key or user IDs: ")
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payload = { "op": "get", "search": pattern }
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r = requests.get(url, verify=True, params=payload)
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result = c.key_import(r.content)
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if result is not None and hasattr(result, "considered") is False:
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print(result)
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elif result is not None and hasattr(result, "considered") is True:
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num_keys = len(result.imports)
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new_revs = result.new_revocations
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new_sigs = result.new_signatures
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new_subs = result.new_sub_keys
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new_uids = result.new_user_ids
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new_scrt = result.secret_imported
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nochange = result.unchanged
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print("""
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The total number of keys considered for import was: {0}
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Number of keys revoked: {1}
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Number of new signatures: {2}
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Number of new subkeys: {3}
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Number of new user IDs: {4}
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Number of new secret keys: {5}
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Number of unchanged keys: {6}
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The key IDs for all considered keys were:
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""".format(num_keys, new_revs, new_sigs, new_subs, new_uids, new_scrt,
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nochange))
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for i in range(num_keys):
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print(result.imports[i].fpr)
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print("")
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else:
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pass
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#+end_src
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*NOTE:* When searching for a key ID of any length or a fingerprint
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(without spaces), the SKS servers require the the leading =0x=
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|
indicative of hexadecimal be included. Also note that the old short
|
|
key IDs (e.g. =0xDEADBEEF=) should no longer be used due to the
|
|
relative ease by which such key IDs can be reproduced, as demonstrated
|
|
by the Evil32 Project in 2014 (which was subsequently exploited in
|
|
2016).
|
|
|
|
|
|
** Exporting keys
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-export-key
|
|
:END:
|
|
|
|
Exporting keys remains a reasonably simple task, but has been
|
|
separated into three different functions for the OpenPGP cryptographic
|
|
engine. Two of those functions are for exporting public keys and the
|
|
third is for exporting secret keys.
|
|
|
|
|
|
*** Exporting public keys
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-export-public-key
|
|
:END:
|
|
|
|
There are two methods of exporting public keys, both of which are very
|
|
similar to the other. The default method, =key_export()=, will export
|
|
a public key or keys matching a specified pattern as normal. The
|
|
alternative, the =key_export_minimal()= method, will do the same thing
|
|
except producing a minimised output with extra signatures and third
|
|
party signatures or certifications removed.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import os.path
|
|
import sys
|
|
|
|
print("""
|
|
This script exports one or more public keys.
|
|
""")
|
|
|
|
c = gpg.Context(armor=True)
|
|
|
|
if len(sys.argv) >= 4:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = sys.argv[3]
|
|
elif len(sys.argv) == 3:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
elif len(sys.argv) == 2:
|
|
keyfile = sys.argv[1]
|
|
logrus = input("Enter the UID matching the key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
else:
|
|
keyfile = input("Enter the path and filename to save the secret key to: ")
|
|
logrus = input("Enter the UID matching the key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
|
|
if homedir.startswith("~"):
|
|
if os.path.exists(os.path.expanduser(homedir)) is True:
|
|
c.home_dir = os.path.expanduser(homedir)
|
|
else:
|
|
pass
|
|
elif os.path.exists(homedir) is True:
|
|
c.home_dir = homedir
|
|
else:
|
|
pass
|
|
|
|
try:
|
|
result = c.key_export(pattern=logrus)
|
|
except:
|
|
result = c.key_export(pattern=None)
|
|
|
|
if result is not None:
|
|
with open(keyfile, "wb") as f:
|
|
f.write(result)
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
It is important to note that the result will only return =None= when a
|
|
pattern has been entered for =logrus=, but it has not matched any
|
|
keys. When the search pattern itself is set to =None= this triggers
|
|
the exporting of the entire public keybox.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import os.path
|
|
import sys
|
|
|
|
print("""
|
|
This script exports one or more public keys in minimised form.
|
|
""")
|
|
|
|
c = gpg.Context(armor=True)
|
|
|
|
if len(sys.argv) >= 4:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = sys.argv[3]
|
|
elif len(sys.argv) == 3:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
elif len(sys.argv) == 2:
|
|
keyfile = sys.argv[1]
|
|
logrus = input("Enter the UID matching the key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
else:
|
|
keyfile = input("Enter the path and filename to save the secret key to: ")
|
|
logrus = input("Enter the UID matching the key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
|
|
if homedir.startswith("~"):
|
|
if os.path.exists(os.path.expanduser(homedir)) is True:
|
|
c.home_dir = os.path.expanduser(homedir)
|
|
else:
|
|
pass
|
|
elif os.path.exists(homedir) is True:
|
|
c.home_dir = homedir
|
|
else:
|
|
pass
|
|
|
|
try:
|
|
result = c.key_export_minimal(pattern=logrus)
|
|
except:
|
|
result = c.key_export_minimal(pattern=None)
|
|
|
|
if result is not None:
|
|
with open(keyfile, "wb") as f:
|
|
f.write(result)
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
|
|
*** Exporting secret keys
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-export-secret-key
|
|
:END:
|
|
|
|
Exporting secret keys is, functionally, very similar to exporting
|
|
public keys; save for the invocation of =pinentry= via =gpg-agent= in
|
|
order to securely enter the key's passphrase and authorise the export.
|
|
|
|
The following example exports the secret key to a file which is then
|
|
set with the same permissions as the output files created by the
|
|
command line secret key export options.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import os
|
|
import os.path
|
|
import sys
|
|
|
|
print("""
|
|
This script exports one or more secret keys.
|
|
|
|
The gpg-agent and pinentry are invoked to authorise the export.
|
|
""")
|
|
|
|
c = gpg.Context(armor=True)
|
|
|
|
if len(sys.argv) >= 4:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = sys.argv[3]
|
|
elif len(sys.argv) == 3:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
elif len(sys.argv) == 2:
|
|
keyfile = sys.argv[1]
|
|
logrus = input("Enter the UID matching the secret key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
else:
|
|
keyfile = input("Enter the path and filename to save the secret key to: ")
|
|
logrus = input("Enter the UID matching the secret key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
|
|
if homedir.startswith("~"):
|
|
if os.path.exists(os.path.expanduser(homedir)) is True:
|
|
c.home_dir = os.path.expanduser(homedir)
|
|
else:
|
|
pass
|
|
elif os.path.exists(homedir) is True:
|
|
c.home_dir = homedir
|
|
else:
|
|
pass
|
|
|
|
try:
|
|
result = c.key_export_secret(pattern=logrus)
|
|
except:
|
|
result = c.key_export_secret(pattern=None)
|
|
|
|
if result is not None:
|
|
with open(keyfile, "wb") as f:
|
|
f.write(result)
|
|
os.chmod(keyfile, 0o600)
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
Alternatively the approach of the following script can be used. This
|
|
longer example saves the exported secret key(s) in files in the GnuPG
|
|
home directory, in addition to setting the file permissions as only
|
|
readable and writable by the user. It also exports the secret key(s)
|
|
twice in order to output both GPG binary (=.gpg=) and ASCII armoured
|
|
(=.asc=) files.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import os
|
|
import os.path
|
|
import subprocess
|
|
import sys
|
|
|
|
print("""
|
|
This script exports one or more secret keys as both ASCII armored and binary
|
|
file formats, saved in files within the user's GPG home directory.
|
|
|
|
The gpg-agent and pinentry are invoked to authorise the export.
|
|
""")
|
|
|
|
if sys.platform == "win32":
|
|
gpgconfcmd = "gpgconf.exe --list-dirs homedir"
|
|
else:
|
|
gpgconfcmd = "gpgconf --list-dirs homedir"
|
|
|
|
a = gpg.Context(armor=True)
|
|
b = gpg.Context()
|
|
c = gpg.Context()
|
|
|
|
if len(sys.argv) >= 4:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = sys.argv[3]
|
|
elif len(sys.argv) == 3:
|
|
keyfile = sys.argv[1]
|
|
logrus = sys.argv[2]
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
elif len(sys.argv) == 2:
|
|
keyfile = sys.argv[1]
|
|
logrus = input("Enter the UID matching the secret key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
else:
|
|
keyfile = input("Enter the filename to save the secret key to: ")
|
|
logrus = input("Enter the UID matching the secret key(s) to export: ")
|
|
homedir = input("Enter the GPG configuration directory path (optional): ")
|
|
|
|
if homedir.startswith("~"):
|
|
if os.path.exists(os.path.expanduser(homedir)) is True:
|
|
c.home_dir = os.path.expanduser(homedir)
|
|
else:
|
|
pass
|
|
elif os.path.exists(homedir) is True:
|
|
c.home_dir = homedir
|
|
else:
|
|
pass
|
|
|
|
if c.home_dir is not None:
|
|
if c.home_dir.endswith("/"):
|
|
gpgfile = "{0}{1}.gpg".format(c.home_dir, keyfile)
|
|
ascfile = "{0}{1}.asc".format(c.home_dir, keyfile)
|
|
else:
|
|
gpgfile = "{0}/{1}.gpg".format(c.home_dir, keyfile)
|
|
ascfile = "{0}/{1}.asc".format(c.home_dir, keyfile)
|
|
else:
|
|
if os.path.exists(os.environ["GNUPGHOME"]) is True:
|
|
hd = os.environ["GNUPGHOME"]
|
|
else:
|
|
hd = subprocess.getoutput(gpgconfcmd)
|
|
gpgfile = "{0}/{1}.gpg".format(hd, keyfile)
|
|
ascfile = "{0}/{1}.asc".format(hd, keyfile)
|
|
|
|
try:
|
|
a_result = a.key_export_secret(pattern=logrus)
|
|
b_result = b.key_export_secret(pattern=logrus)
|
|
except:
|
|
a_result = a.key_export_secret(pattern=None)
|
|
b_result = b.key_export_secret(pattern=None)
|
|
|
|
if a_result is not None:
|
|
with open(ascfile, "wb") as f:
|
|
f.write(a_result)
|
|
os.chmod(ascfile, 0o600)
|
|
else:
|
|
pass
|
|
|
|
if b_result is not None:
|
|
with open(gpgfile, "wb") as f:
|
|
f.write(b_result)
|
|
os.chmod(gpgfile, 0o600)
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
|
|
* Basic Functions
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-the-basics
|
|
:END:
|
|
|
|
The most frequently called features of any cryptographic library will
|
|
be the most fundamental tasks for encryption software. In this
|
|
section we will look at how to programmatically encrypt data, decrypt
|
|
it, sign it and verify signatures.
|
|
|
|
|
|
** Encryption
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-encryption
|
|
:END:
|
|
|
|
Encrypting is very straight forward. In the first example below the
|
|
message, =text=, is encrypted to a single recipient's key. In the
|
|
second example the message will be encrypted to multiple recipients.
|
|
|
|
|
|
*** Encrypting to one key
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-encryption-single
|
|
:END:
|
|
|
|
Once the the Context is set the main issues with encrypting data is
|
|
essentially reduced to key selection and the keyword arguments
|
|
specified in the =gpg.Context().encrypt()= method.
|
|
|
|
Those keyword arguments are: =recipients=, a list of keys encrypted to
|
|
(covered in greater detail in the following section); =sign=, whether
|
|
or not to sign the plaintext data, see subsequent sections on signing
|
|
and verifying signatures below (defaults to =True=); =sink=, to write
|
|
results or partial results to a secure sink instead of returning it
|
|
(defaults to =None=); =passphrase=, only used when utilising symmetric
|
|
encryption (defaults to =None=); =always_trust=, used to override the
|
|
trust model settings for recipient keys (defaults to =False=);
|
|
=add_encrypt_to=, utilises any preconfigured =encrypt-to= or
|
|
=default-key= settings in the user's =gpg.conf= file (defaults to
|
|
=False=); =prepare=, prepare for encryption (defaults to =False=);
|
|
=expect_sign=, prepare for signing (defaults to =False=); =compress=,
|
|
compresses the plaintext prior to encryption (defaults to =True=).
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
a_key = "0x12345678DEADBEEF"
|
|
text = b"""Some text to test with.
|
|
|
|
Since the text in this case must be bytes, it is most likely that
|
|
the input form will be a separate file which is opened with "rb"
|
|
as this is the simplest method of obtaining the correct data format.
|
|
"""
|
|
|
|
c = gpg.Context(armor=True)
|
|
rkey = list(c.keylist(pattern=a_key, secret=False))
|
|
ciphertext, result, sign_result = c.encrypt(text, recipients=rkey, sign=False)
|
|
|
|
with open("secret_plans.txt.asc", "wb") as afile:
|
|
afile.write(ciphertext)
|
|
#+end_src
|
|
|
|
Though this is even more likely to be used like this; with the
|
|
plaintext input read from a file, the recipient keys used for
|
|
encryption regardless of key trust status and the encrypted output
|
|
also encrypted to any preconfigured keys set in the =gpg.conf= file:
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
a_key = "0x12345678DEADBEEF"
|
|
|
|
with open("secret_plans.txt", "rb") as afile:
|
|
text = afile.read()
|
|
|
|
c = gpg.Context(armor=True)
|
|
rkey = list(c.keylist(pattern=a_key, secret=False))
|
|
ciphertext, result, sign_result = c.encrypt(text, recipients=rkey, sign=True,
|
|
always_trust=True,
|
|
add_encrypt_to=True)
|
|
|
|
with open("secret_plans.txt.asc", "wb") as afile:
|
|
afile.write(ciphertext)
|
|
#+end_src
|
|
|
|
If the =recipients= paramater is empty then the plaintext is encrypted
|
|
symmetrically. If no =passphrase= is supplied as a parameter or via a
|
|
callback registered with the =Context()= then an out-of-band prompt
|
|
for the passphrase via pinentry will be invoked.
|
|
|
|
|
|
*** Encrypting to multiple keys
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-encryption-multiple
|
|
:END:
|
|
|
|
Encrypting to multiple keys essentially just expands upon the key
|
|
selection process and the recipients from the previous examples.
|
|
|
|
The following example encrypts a message (=text=) to everyone with an
|
|
email address on the =gnupg.org= domain,[fn:3] but does /not/ encrypt
|
|
to a default key or other key which is configured to normally encrypt
|
|
to.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
text = b"""Oh look, another test message.
|
|
|
|
The same rules apply as with the previous example and more likely
|
|
than not, the message will actually be drawn from reading the
|
|
contents of a file or, maybe, from entering data at an input()
|
|
prompt.
|
|
|
|
Since the text in this case must be bytes, it is most likely that
|
|
the input form will be a separate file which is opened with "rb"
|
|
as this is the simplest method of obtaining the correct data
|
|
format.
|
|
"""
|
|
|
|
c = gpg.Context(armor=True)
|
|
rpattern = list(c.keylist(pattern="@gnupg.org", secret=False))
|
|
logrus = []
|
|
|
|
for i in range(len(rpattern)):
|
|
if rpattern[i].can_encrypt == 1:
|
|
logrus.append(rpattern[i])
|
|
|
|
ciphertext, result, sign_result = c.encrypt(text, recipients=logrus,
|
|
sign=False, always_trust=True)
|
|
|
|
with open("secret_plans.txt.asc", "wb") as afile:
|
|
afile.write(ciphertext)
|
|
#+end_src
|
|
|
|
All it would take to change the above example to sign the message
|
|
and also encrypt the message to any configured default keys would
|
|
be to change the =c.encrypt= line to this:
|
|
|
|
#+begin_src python -i
|
|
ciphertext, result, sign_result = c.encrypt(text, recipients=logrus,
|
|
always_trust=True,
|
|
add_encrypt_to=True)
|
|
#+end_src
|
|
|
|
The only keyword arguments requiring modification are those for which
|
|
the default values are changing. The default value of =sign= is
|
|
=True=, the default of =always_trust= is =False=, the default of
|
|
=add_encrypt_to= is =False=.
|
|
|
|
If =always_trust= is not set to =True= and any of the recipient keys
|
|
are not trusted (e.g. not signed or locally signed) then the
|
|
encryption will raise an error. It is possible to mitigate this
|
|
somewhat with something more like this:
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
with open("secret_plans.txt.asc", "rb") as afile:
|
|
text = afile.read()
|
|
|
|
c = gpg.Context(armor=True)
|
|
rpattern = list(c.keylist(pattern="@gnupg.org", secret=False))
|
|
logrus = []
|
|
|
|
for i in range(len(rpattern)):
|
|
if rpattern[i].can_encrypt == 1:
|
|
logrus.append(rpattern[i])
|
|
|
|
try:
|
|
ciphertext, result, sign_result = c.encrypt(text, recipients=logrus,
|
|
add_encrypt_to=True)
|
|
except gpg.errors.InvalidRecipients as e:
|
|
for i in range(len(e.recipients)):
|
|
for n in range(len(logrus)):
|
|
if logrus[n].fpr == e.recipients[i].fpr:
|
|
logrus.remove(logrus[n])
|
|
else:
|
|
pass
|
|
try:
|
|
ciphertext, result, sign_result = c.encrypt(text,
|
|
recipients=logrus,
|
|
add_encrypt_to=True)
|
|
with open("secret_plans.txt.asc", "wb") as afile:
|
|
afile.write(ciphertext)
|
|
except:
|
|
pass
|
|
#+end_src
|
|
|
|
This will attempt to encrypt to all the keys searched for, then remove
|
|
invalid recipients if it fails and try again.
|
|
|
|
|
|
** Decryption
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-decryption
|
|
:END:
|
|
|
|
Decrypting something encrypted to a key in one's secret keyring is
|
|
fairly straight forward.
|
|
|
|
In this example code, however, preconfiguring either =gpg.Context()=
|
|
or =gpg.core.Context()= as =c= is unnecessary because there is no need
|
|
to modify the Context prior to conducting the decryption and since the
|
|
Context is only used once, setting it to =c= simply adds lines for no
|
|
gain.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
ciphertext = input("Enter path and filename of encrypted file: ")
|
|
newfile = input("Enter path and filename of file to save decrypted data to: ")
|
|
|
|
with open(ciphertext, "rb") as cfile:
|
|
try:
|
|
plaintext, result, verify_result = gpg.Context().decrypt(cfile)
|
|
except gpg.errors.GPGMEError as e:
|
|
plaintext = None
|
|
print(e)
|
|
|
|
if plaintext is not None:
|
|
with open(newfile, "wb") as nfile:
|
|
nfile.write(plaintext)
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
The data available in =plaintext= in this example is the decrypted
|
|
content as a byte object, the recipient key IDs and algorithms in
|
|
=result= and the results of verifying any signatures of the data in
|
|
=verify_result=.
|
|
|
|
|
|
** Signing text and files
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-signing
|
|
:END:
|
|
|
|
The following sections demonstrate how to specify keys to sign with.
|
|
|
|
|
|
*** Signing key selection
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-signing-signers
|
|
:END:
|
|
|
|
By default GPGME and the Python bindings will use the default key
|
|
configured for the user invoking the GPGME API. If there is no
|
|
default key specified and there is more than one secret key available
|
|
it may be necessary to specify the key or keys with which to sign
|
|
messages and files.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
logrus = input("Enter the email address or string to match signing keys to: ")
|
|
hancock = gpg.Context().keylist(pattern=logrus, secret=True)
|
|
sig_src = list(hancock)
|
|
#+end_src
|
|
|
|
The signing examples in the following sections include the explicitly
|
|
designated =signers= parameter in two of the five examples; once where
|
|
the resulting signature would be ASCII armoured and once where it
|
|
would not be armoured.
|
|
|
|
While it would be possible to enter a key ID or fingerprint here to
|
|
match a specific key, it is not possible to enter two fingerprints and
|
|
match two keys since the patten expects a string, bytes or None and
|
|
not a list. A string with two fingerprints won't match any single
|
|
key.
|
|
|
|
|
|
*** Normal or default signing messages or files
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-signing-normal
|
|
:END:
|
|
|
|
The normal or default signing process is essentially the same as is
|
|
most often invoked when also encrypting a message or file. So when
|
|
the encryption component is not utilised, the result is to produce an
|
|
encoded and signed output which may or may not be ASCII armoured and
|
|
which may or may not also be compressed.
|
|
|
|
By default compression will be used unless GnuPG detects that the
|
|
plaintext is already compressed. ASCII armouring will be determined
|
|
according to the value of =gpg.Context().armor=.
|
|
|
|
The compression algorithm is selected in much the same way as the
|
|
symmetric encryption algorithm or the hash digest algorithm is when
|
|
multiple keys are involved; from the preferences saved into the key
|
|
itself or by comparison with the preferences with all other keys
|
|
involved.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
text0 = """Declaration of ... something.
|
|
|
|
"""
|
|
text = text0.encode()
|
|
|
|
c = gpg.Context(armor=True, signers=sig_src)
|
|
signed_data, result = c.sign(text, mode=gpg.constants.sig.mode.NORMAL)
|
|
|
|
with open("/path/to/statement.txt.asc", "w") as afile:
|
|
afile.write(signed_data.decode())
|
|
#+end_src
|
|
|
|
Though everything in this example is accurate, it is more likely that
|
|
reading the input data from another file and writing the result to a
|
|
new file will be performed more like the way it is done in the next
|
|
example. Even if the output format is ASCII armoured.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
with open("/path/to/statement.txt", "rb") as tfile:
|
|
text = tfile.read()
|
|
|
|
c = gpg.Context()
|
|
signed_data, result = c.sign(text, mode=gpg.constants.sig.mode.NORMAL)
|
|
|
|
with open("/path/to/statement.txt.sig", "wb") as afile:
|
|
afile.write(signed_data)
|
|
#+end_src
|
|
|
|
|
|
*** Detached signing messages and files
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-signing-detached
|
|
:END:
|
|
|
|
Detached signatures will often be needed in programmatic uses of
|
|
GPGME, either for signing files (e.g. tarballs of code releases) or as
|
|
a component of message signing (e.g. PGP/MIME encoded email).
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
text0 = """Declaration of ... something.
|
|
|
|
"""
|
|
text = text0.encode()
|
|
|
|
c = gpg.Context(armor=True)
|
|
signed_data, result = c.sign(text, mode=gpg.constants.sig.mode.DETACH)
|
|
|
|
with open("/path/to/statement.txt.asc", "w") as afile:
|
|
afile.write(signed_data.decode())
|
|
#+end_src
|
|
|
|
As with normal signatures, detached signatures are best handled as
|
|
byte literals, even when the output is ASCII armoured.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
with open("/path/to/statement.txt", "rb") as tfile:
|
|
text = tfile.read()
|
|
|
|
c = gpg.Context(signers=sig_src)
|
|
signed_data, result = c.sign(text, mode=gpg.constants.sig.mode.DETACH)
|
|
|
|
with open("/path/to/statement.txt.sig", "wb") as afile:
|
|
afile.write(signed_data)
|
|
#+end_src
|
|
|
|
|
|
*** Clearsigning messages or text
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-signing-clear
|
|
:END:
|
|
|
|
Though PGP/in-line messages are no longer encouraged in favour of
|
|
PGP/MIME, there is still sometimes value in utilising in-line
|
|
signatures. This is where clear-signed messages or text is of value.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
text0 = """Declaration of ... something.
|
|
|
|
"""
|
|
text = text0.encode()
|
|
|
|
c = gpg.Context()
|
|
signed_data, result = c.sign(text, mode=gpg.constants.sig.mode.CLEAR)
|
|
|
|
with open("/path/to/statement.txt.asc", "w") as afile:
|
|
afile.write(signed_data.decode())
|
|
#+end_src
|
|
|
|
In spite of the appearance of a clear-signed message, the data handled
|
|
by GPGME in signing it must still be byte literals.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
with open("/path/to/statement.txt", "rb") as tfile:
|
|
text = tfile.read()
|
|
|
|
c = gpg.Context()
|
|
signed_data, result = c.sign(text, mode=gpg.constants.sig.mode.CLEAR)
|
|
|
|
with open("/path/to/statement.txt.asc", "wb") as afile:
|
|
afile.write(signed_data)
|
|
#+end_src
|
|
|
|
|
|
** Signature verification
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: howto-basic-verification
|
|
:END:
|
|
|
|
Essentially there are two principal methods of verification of a
|
|
signature. The first of these is for use with the normal or default
|
|
signing method and for clear-signed messages. The second is for use
|
|
with files and data with detached signatures.
|
|
|
|
The following example is intended for use with the default signing
|
|
method where the file was not ASCII armoured:
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import time
|
|
|
|
filename = "statement.txt"
|
|
gpg_file = "statement.txt.gpg"
|
|
|
|
c = gpg.Context()
|
|
|
|
try:
|
|
data, result = c.verify(open(gpg_file))
|
|
verified = True
|
|
except gpg.errors.BadSignatures as e:
|
|
verified = False
|
|
print(e)
|
|
|
|
if verified is True:
|
|
for i in range(len(result.signatures)):
|
|
sign = result.signatures[i]
|
|
print("""Good signature from:
|
|
{0}
|
|
with key {1}
|
|
made at {2}
|
|
""".format(c.get_key(sign.fpr).uids[0].uid, sign.fpr,
|
|
time.ctime(sign.timestamp)))
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
Whereas this next example, which is almost identical would work with
|
|
normal ASCII armoured files and with clear-signed files:
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import time
|
|
|
|
filename = "statement.txt"
|
|
asc_file = "statement.txt.asc"
|
|
|
|
c = gpg.Context()
|
|
|
|
try:
|
|
data, result = c.verify(open(asc_file))
|
|
verified = True
|
|
except gpg.errors.BadSignatures as e:
|
|
verified = False
|
|
print(e)
|
|
|
|
if verified is True:
|
|
for i in range(len(result.signatures)):
|
|
sign = result.signatures[i]
|
|
print("""Good signature from:
|
|
{0}
|
|
with key {1}
|
|
made at {2}
|
|
""".format(c.get_key(sign.fpr).uids[0].uid, sign.fpr,
|
|
time.ctime(sign.timestamp)))
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
In both of the previous examples it is also possible to compare the
|
|
original data that was signed against the signed data in =data= to see
|
|
if it matches with something like this:
|
|
|
|
#+begin_src python -i
|
|
with open(filename, "rb") as afile:
|
|
text = afile.read()
|
|
|
|
if text == data:
|
|
print("Good signature.")
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
The following two examples, however, deal with detached signatures.
|
|
With his method of verification the data that was signed does not get
|
|
returned since it is already being explicitly referenced in the first
|
|
argument of =c.verify=. So =data= is =None= and only the information
|
|
in =result= is available.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import time
|
|
|
|
filename = "statement.txt"
|
|
sig_file = "statement.txt.sig"
|
|
|
|
c = gpg.Context()
|
|
|
|
try:
|
|
data, result = c.verify(open(filename), open(sig_file))
|
|
verified = True
|
|
except gpg.errors.BadSignatures as e:
|
|
verified = False
|
|
print(e)
|
|
|
|
if verified is True:
|
|
for i in range(len(result.signatures)):
|
|
sign = result.signatures[i]
|
|
print("""Good signature from:
|
|
{0}
|
|
with key {1}
|
|
made at {2}
|
|
""".format(c.get_key(sign.fpr).uids[0].uid, sign.fpr,
|
|
time.ctime(sign.timestamp)))
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
import time
|
|
|
|
filename = "statement.txt"
|
|
asc_file = "statement.txt.asc"
|
|
|
|
c = gpg.Context()
|
|
|
|
try:
|
|
data, result = c.verify(open(filename), open(asc_file))
|
|
verified = True
|
|
except gpg.errors.BadSignatures as e:
|
|
verified = False
|
|
print(e)
|
|
|
|
if verified is True:
|
|
for i in range(len(result.signatures)):
|
|
sign = result.signatures[i]
|
|
print("""Good signature from:
|
|
{0}
|
|
with key {1}
|
|
made at {2}
|
|
""".format(c.get_key(sign.fpr).uids[0].uid, sign.fpr,
|
|
time.ctime(sign.timestamp)))
|
|
else:
|
|
pass
|
|
#+end_src
|
|
|
|
|
|
* Creating keys and subkeys
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: key-generation
|
|
:END:
|
|
|
|
The one thing, aside from GnuPG itself, that GPGME depends on, of
|
|
course, is the keys themselves. So it is necessary to be able to
|
|
generate them and modify them by adding subkeys, revoking or disabling
|
|
them, sometimes deleting them and doing the same for user IDs.
|
|
|
|
In the following examples a key will be created for the world's
|
|
greatest secret agent, Danger Mouse. Since Danger Mouse is a secret
|
|
agent he needs to be able to protect information to =SECRET= level
|
|
clearance, so his keys will be 3072-bit keys.
|
|
|
|
The pre-configured =gpg.conf= file which sets cipher, digest and other
|
|
preferences contains the following configuration parameters:
|
|
|
|
#+begin_src conf
|
|
expert
|
|
allow-freeform-uid
|
|
allow-secret-key-import
|
|
trust-model tofu+pgp
|
|
tofu-default-policy unknown
|
|
enable-large-rsa
|
|
enable-dsa2
|
|
cert-digest-algo SHA512
|
|
default-preference-list TWOFISH CAMELLIA256 AES256 CAMELLIA192 AES192 CAMELLIA128 AES BLOWFISH IDEA CAST5 3DES SHA512 SHA384 SHA256 SHA224 RIPEMD160 SHA1 ZLIB BZIP2 ZIP Uncompressed
|
|
personal-cipher-preferences TWOFISH CAMELLIA256 AES256 CAMELLIA192 AES192 CAMELLIA128 AES BLOWFISH IDEA CAST5 3DES
|
|
personal-digest-preferences SHA512 SHA384 SHA256 SHA224 RIPEMD160 SHA1
|
|
personal-compress-preferences ZLIB BZIP2 ZIP Uncompressed
|
|
#+end_src
|
|
|
|
|
|
** Primary key
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: keygen-primary
|
|
:END:
|
|
|
|
Generating a primary key uses the =create_key= method in a Context.
|
|
It contains multiple arguments and keyword arguments, including:
|
|
=userid=, =algorithm=, =expires_in=, =expires=, =sign=, =encrypt=,
|
|
=certify=, =authenticate=, =passphrase= and =force=. The defaults for
|
|
all of those except =userid=, =algorithm=, =expires_in=, =expires= and
|
|
=passphrase= is =False=. The defaults for =algorithm= and
|
|
=passphrase= is =None=. The default for =expires_in= is =0=. The
|
|
default for =expires= is =True=. There is no default for =userid=.
|
|
|
|
If =passphrase= is left as =None= then the key will not be generated
|
|
with a passphrase, if =passphrase= is set to a string then that will
|
|
be the passphrase and if =passphrase= is set to =True= then gpg-agent
|
|
will launch pinentry to prompt for a passphrase. For the sake of
|
|
convenience, these examples will keep =passphrase= set to =None=.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
c = gpg.Context()
|
|
|
|
c.home_dir = "~/.gnupg-dm"
|
|
userid = "Danger Mouse <dm@secret.example.net>"
|
|
|
|
dmkey = c.create_key(userid, algorithm="rsa3072", expires_in=31536000,
|
|
sign=True, certify=True)
|
|
#+end_src
|
|
|
|
One thing to note here is the use of setting the =c.home_dir=
|
|
parameter. This enables generating the key or keys in a different
|
|
location. In this case to keep the new key data created for this
|
|
example in a separate location rather than adding it to existing and
|
|
active key store data. As with the default directory, =~/.gnupg=, any
|
|
temporary or separate directory needs the permissions set to only
|
|
permit access by the directory owner. On posix systems this means
|
|
setting the directory permissions to 700.
|
|
|
|
The =temp-homedir-config.py= script in the HOWTO examples directory
|
|
will create an alternative homedir with these configuration options
|
|
already set and the correct directory and file permissions.
|
|
|
|
The successful generation of the key can be confirmed via the returned
|
|
=GenkeyResult= object, which includes the following data:
|
|
|
|
#+begin_src python -i
|
|
print("""
|
|
Fingerprint: {0}
|
|
Primary Key: {1}
|
|
Public Key: {2}
|
|
Secret Key: {3}
|
|
Sub Key: {4}
|
|
User IDs: {5}
|
|
""".format(dmkey.fpr, dmkey.primary, dmkey.pubkey, dmkey.seckey, dmkey.sub,
|
|
dmkey.uid))
|
|
#+end_src
|
|
|
|
Alternatively the information can be confirmed using the command line
|
|
program:
|
|
|
|
#+begin_src shell
|
|
bash-4.4$ gpg --homedir ~/.gnupg-dm -K
|
|
~/.gnupg-dm/pubring.kbx
|
|
----------------------
|
|
sec rsa3072 2018-03-15 [SC] [expires: 2019-03-15]
|
|
177B7C25DB99745EE2EE13ED026D2F19E99E63AA
|
|
uid [ultimate] Danger Mouse <dm@secret.example.net>
|
|
|
|
bash-4.4$
|
|
#+end_src
|
|
|
|
As with generating keys manually, to preconfigure expanded preferences
|
|
for the cipher, digest and compression algorithms, the =gpg.conf= file
|
|
must contain those details in the home directory in which the new key
|
|
is being generated. I used a cut down version of my own =gpg.conf=
|
|
file in order to be able to generate this:
|
|
|
|
#+begin_src shell
|
|
bash-4.4$ gpg --homedir ~/.gnupg-dm --edit-key 177B7C25DB99745EE2EE13ED026D2F19E99E63AA showpref quit
|
|
Secret key is available.
|
|
|
|
sec rsa3072/026D2F19E99E63AA
|
|
created: 2018-03-15 expires: 2019-03-15 usage: SC
|
|
trust: ultimate validity: ultimate
|
|
[ultimate] (1). Danger Mouse <dm@secret.example.net>
|
|
|
|
[ultimate] (1). Danger Mouse <dm@secret.example.net>
|
|
Cipher: TWOFISH, CAMELLIA256, AES256, CAMELLIA192, AES192, CAMELLIA128, AES, BLOWFISH, IDEA, CAST5, 3DES
|
|
Digest: SHA512, SHA384, SHA256, SHA224, RIPEMD160, SHA1
|
|
Compression: ZLIB, BZIP2, ZIP, Uncompressed
|
|
Features: MDC, Keyserver no-modify
|
|
|
|
bash-4.4$
|
|
#+end_src
|
|
|
|
|
|
** Subkeys
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: keygen-subkeys
|
|
:END:
|
|
|
|
Adding subkeys to a primary key is fairly similar to creating the
|
|
primary key with the =create_subkey= method. Most of the arguments
|
|
are the same, but not quite all. Instead of the =userid= argument
|
|
there is now a =key= argument for selecting which primary key to add
|
|
the subkey to.
|
|
|
|
In the following example an encryption subkey will be added to the
|
|
primary key. Since Danger Mouse is a security conscious secret agent,
|
|
this subkey will only be valid for about six months, half the length
|
|
of the primary key.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
c = gpg.Context()
|
|
c.home_dir = "~/.gnupg-dm"
|
|
|
|
key = c.get_key(dmkey.fpr, secret=True)
|
|
dmsub = c.create_subkey(key, algorithm="rsa3072", expires_in=15768000,
|
|
encrypt=True)
|
|
#+end_src
|
|
|
|
As with the primary key, the results here can be checked with:
|
|
|
|
#+begin_src python -i
|
|
print("""
|
|
Fingerprint: {0}
|
|
Primary Key: {1}
|
|
Public Key: {2}
|
|
Secret Key: {3}
|
|
Sub Key: {4}
|
|
User IDs: {5}
|
|
""".format(dmsub.fpr, dmsub.primary, dmsub.pubkey, dmsub.seckey, dmsub.sub,
|
|
dmsub.uid))
|
|
#+end_src
|
|
|
|
As well as on the command line with:
|
|
|
|
#+begin_src shell
|
|
bash-4.4$ gpg --homedir ~/.gnupg-dm -K
|
|
~/.gnupg-dm/pubring.kbx
|
|
----------------------
|
|
sec rsa3072 2018-03-15 [SC] [expires: 2019-03-15]
|
|
177B7C25DB99745EE2EE13ED026D2F19E99E63AA
|
|
uid [ultimate] Danger Mouse <dm@secret.example.net>
|
|
ssb rsa3072 2018-03-15 [E] [expires: 2018-09-13]
|
|
|
|
bash-4.4$
|
|
#+end_src
|
|
|
|
|
|
** User IDs
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: keygen-uids
|
|
:END:
|
|
|
|
|
|
*** Adding User IDs
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: keygen-uids-add
|
|
:END:
|
|
|
|
By comparison to creating primary keys and subkeys, adding a new user
|
|
ID to an existing key is much simpler. The method used to do this is
|
|
=key_add_uid= and the only arguments it takes are for the =key= and
|
|
the new =uid=.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
c = gpg.Context()
|
|
c.home_dir = "~/.gnupg-dm"
|
|
|
|
dmfpr = "177B7C25DB99745EE2EE13ED026D2F19E99E63AA"
|
|
key = c.get_key(dmfpr, secret=True)
|
|
uid = "Danger Mouse <danger.mouse@secret.example.net>"
|
|
|
|
c.key_add_uid(key, uid)
|
|
#+end_src
|
|
|
|
Unsurprisingly the result of this is:
|
|
|
|
#+begin_src shell
|
|
bash-4.4$ gpg --homedir ~/.gnupg-dm -K
|
|
~/.gnupg-dm/pubring.kbx
|
|
----------------------
|
|
sec rsa3072 2018-03-15 [SC] [expires: 2019-03-15]
|
|
177B7C25DB99745EE2EE13ED026D2F19E99E63AA
|
|
uid [ultimate] Danger Mouse <danger.mouse@secret.example.net>
|
|
uid [ultimate] Danger Mouse <dm@secret.example.net>
|
|
ssb rsa3072 2018-03-15 [E] [expires: 2018-09-13]
|
|
|
|
bash-4.4$
|
|
#+end_src
|
|
|
|
|
|
*** Revokinging User IDs
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: keygen-uids-revoke
|
|
:END:
|
|
|
|
Revoking a user ID is a fairly similar process, except that it uses
|
|
the =key_revoke_uid= method.
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
c = gpg.Context()
|
|
c.home_dir = "~/.gnupg-dm"
|
|
|
|
dmfpr = "177B7C25DB99745EE2EE13ED026D2F19E99E63AA"
|
|
key = c.get_key(dmfpr, secret=True)
|
|
uid = "Danger Mouse <danger.mouse@secret.example.net>"
|
|
|
|
c.key_revoke_uid(key, uid)
|
|
#+end_src
|
|
|
|
|
|
** Key certification
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: key-sign
|
|
:END:
|
|
|
|
Since key certification is more frequently referred to as key signing,
|
|
the method used to perform this function is =key_sign=.
|
|
|
|
The =key_sign= method takes four arguments: =key=, =uids=,
|
|
=expires_in= and =local=. The default value of =uids= is =None= and
|
|
which results in all user IDs being selected. The default value of
|
|
both =expires_in= and =local= is =False=; which results in the
|
|
signature never expiring and being able to be exported.
|
|
|
|
The =key= is the key being signed rather than the key doing the
|
|
signing. To change the key doing the signing refer to the signing key
|
|
selection above for signing messages and files.
|
|
|
|
If the =uids= value is not =None= then it must either be a string to
|
|
match a single user ID or a list of strings to match multiple user
|
|
IDs. In this case the matching of those strings must be precise and
|
|
it is case sensitive.
|
|
|
|
To sign Danger Mouse's key for just the initial user ID with a
|
|
signature which will last a little over a month, do this:
|
|
|
|
#+begin_src python -i
|
|
import gpg
|
|
|
|
c = gpg.Context()
|
|
uid = "Danger Mouse <dm@secret.example.net>"
|
|
|
|
dmfpr = "177B7C25DB99745EE2EE13ED026D2F19E99E63AA"
|
|
key = c.get_key(dmfpr, secret=True)
|
|
c.key_sign(key, uids=uid, expires_in=2764800)
|
|
#+end_src
|
|
|
|
|
|
* Miscellaneous work-arounds
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: cheats-and-hacks
|
|
:END:
|
|
|
|
|
|
** Group lines
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: group-lines
|
|
:END:
|
|
|
|
There is not yet an easy way to access groups configured in the
|
|
gpg.conf file from within GPGME. As a consequence these central
|
|
groupings of keys cannot be shared amongst multiple programs, such as
|
|
MUAs readily.
|
|
|
|
The following code, however, provides a work-around for obtaining this
|
|
information in Python.
|
|
|
|
#+begin_src python -i
|
|
import subprocess
|
|
|
|
lines = subprocess.getoutput("gpgconf --list-options gpg").splitlines()
|
|
|
|
for i in range(len(lines)):
|
|
if lines[i].startswith("group") is True:
|
|
line = lines[i]
|
|
else:
|
|
pass
|
|
|
|
groups = line.split(":")[-1].replace('"', '').split(',')
|
|
|
|
group_lines = []
|
|
group_lists = []
|
|
|
|
for i in range(len(groups)):
|
|
group_lines.append(groups[i].split("="))
|
|
group_lists.append(groups[i].split("="))
|
|
|
|
for i in range(len(group_lists)):
|
|
group_lists[i][1] = group_lists[i][1].split()
|
|
#+end_src
|
|
|
|
The result of that code is that =group_lines= is a list of lists where
|
|
=group_lines[i][0]= is the name of the group and =group_lines[i][1]=
|
|
is the key IDs of the group as a string.
|
|
|
|
The =group_lists= result is very similar in that it is a list of
|
|
lists. The first part, =group_lists[i][0]= matches
|
|
=group_lines[i][0]= as the name of the group, but =group_lists[i][1]=
|
|
is the key IDs of the group as a string.
|
|
|
|
A demonstration of using the =groups.py= module is also available in
|
|
the form of the executable =mutt-groups.py= script. This second
|
|
script reads all the group entries in a user's =gpg.conf= file and
|
|
converts them into crypt-hooks suitable for use with the Mutt and
|
|
Neomutt mail clients.
|
|
|
|
|
|
* Copyright and Licensing
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: copyright-and-license
|
|
:END:
|
|
|
|
|
|
** Copyright (C) The GnuPG Project, 2018
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: copyright
|
|
:END:
|
|
|
|
Copyright © The GnuPG Project, 2018.
|
|
|
|
|
|
** License GPL compatible
|
|
:PROPERTIES:
|
|
:CUSTOM_ID: license
|
|
:END:
|
|
|
|
This file is free software; as a special exception the author gives
|
|
unlimited permission to copy and/or distribute it, with or without
|
|
modifications, as long as this notice is preserved.
|
|
|
|
This file is distributed in the hope that it will be useful, but
|
|
WITHOUT ANY WARRANTY, to the extent permitted by law; without even the
|
|
implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
|
|
PURPOSE.
|
|
|
|
|
|
* Footnotes
|
|
|
|
[fn:1] =Short_History.org= and/or =Short_History.html=.
|
|
|
|
[fn:2] The =lang/python/docs/= directory in the GPGME source.
|
|
|
|
[fn:3] You probably don't really want to do this. Searching the
|
|
keyservers for "gnupg.org" produces over 400 results, the majority of
|
|
which aren't actually at the gnupg.org domain, but just included a
|
|
comment regarding the project in their key somewhere.
|
|
|
|
[fn:4] As Python 3.7 is a very recent release, it is not given
|
|
priority over 3.6 yet, but will probably be prioritised by the release
|
|
of Python 3.7.2.
|