8a76deb11e
* removed one bit of whitespace. * Marked up references to gpgme.h. * Fixed one spelling error. * Removed py2.6 from python search order since even if it is supported, it shouldn't be encouraged.
7.3 KiB
GNU Privacy Guard (GnuPG) Made Easy Python Bindings HOWTO (English)
Introduction
Version: 0.0.1-alpha [2018-03-07 Wed] Author: Ben McGinnes <ben@gnupg.org> Author GPG Key: DB4724E6FA4286C92B4E55C4321E4E2373590E5D
This document provides basic instruction in how to use the GPGME Python bindings to programmatically leverage the GPGME library.
GPGME Concepts
A C API
Unlike many modern APIs with which programmers will be more
familiar with these days, the GPGME API is a C API. The API is
intended for use by C coders who would be able to access its
features by including the gpgme.h header file eith their own C
source code and then access its functions just as they would any
other C headers.
This is a very effective method of gaining complete access to the API and in the most efficient manner possible. It does, however, have the drawback that it cannot be directly used by other languages without some means of providing an interface to those languages. This is where the need for bindings in various languages stems.
Python bindings
The Python bindings for GPGME provide a higher level means of accessing the complete feature set of GPGME itself. It also provides a more pythonic means of calling these API functions.
The bindings are generated dynamically with SWIG and the copy of
gpgme.h generated when GPGME is compiled.
This means that a version of the Python bindings is fundamentally
tied to the exact same version of GPGME used to gemerate that copy
of gpgme.h.
Difference between the Python bindings and other GnuPG Python packages
There have been numerous attempts to add GnuPG support to Python over the years. Some of the most well known are listed here, along with what differentiates them.
The python-gnupg package maintained by Vinay Sajip
This is arguably the most popular means of integrating GPG with
Python. The package utilises the subprocess module to implement
wrappers for the gpg and gpg2 executables normally invoked on
the command line (gpg.exe and gpg2.exe on Windows).
The popularity of this package stemmed from its ease of use and capability in providing the most commonly required features.
Unfortunately it has been beset by a number of security issues,
most of which stemmed from using unsafe methods of accessing the
command line via the subprocess calls.
The python-gnupg package is available under the MIT license.
The gnupg package created and maintained by Isis Lovecruft
In 2015 Isis Lovecruft from the Tor Project forked and then
re-implemented the python-gnupg package as just gnupg. This new
package also relied on subprocess to call the gpg or gpg2
binaries, but did so somewhat more securely.
However the naming and version numbering selected for this package resulted in conflicts with the original python-gnupg and since its functions were called in a different manner, the release of this package also resulted in a great deal of consternation when people installed what they thought was an upgrade that subsequently broke the code relying on it.
The gnupg package is available under the GNU General Public License version 3.0 (or later).
The PyME package maintained by Martin Albrecht
This package is the origin of these bindings, though they are
somewhat different now. For details of when and how the PyME
package was folded back into GPGME itself see the Short History
document in this Python bindings docs directory.
The PyME package was first released in 2002 and was also the first
attempt to implement a low level binding to GPGME. In doing so it
provided access to considerably more functionality than either the
python-gnupg or gnupg packages.
The PyME package is only available for Python 2.6 and 2.7.
Porting the PyME package to Python 3.4 in 2015 is what resulted in it being folded into the GPGME project and the current bindings are the end result of that effort.
The PyME package is available under the same dual licensing as GPGME itself: the GNU General Public License version 2.0 (or any later version) and the GNU Lesser Public License version 2.1 (or any later version).
GPGME Python bindings installation
No PyPI
Most third-party Python packages and modules are available and distributed through the Python Package Installer, known as PyPI.
Due to the nature of what these bindings are and how they work, it is infeasible to install the GPGME Python bindings in the same way.
Requirements
The GPGME Python bindings only have three requirements:
- A suitable version of Python 2 or Python 3. With Python 2 that means Python 2.7 and with Python 3 that means Python 3.4 or higher.
- SWIG.
- GPGME itself. Which also means that all of GPGME's dependencies must be installed too.
Installation
Installing the Python bindings is effectively achieved by compiling and installing GPGME itself.
Once SWIG is installed with Python and all the dependencies for
GPGME are installed you only need to confirm that the version(s) of
Python you want the bindings installed for are in your $PATH.
By default GPGME will attempt to install the bindings for the most
recent or highest version number of Python 2 and Python 3 it
detects in $PATH. It specifically checks for the python and
python3 executabled first and then checks for specific version
numbers.
For Python 2 it checks for these executables in this order:
python, python2 and python2.7.
For Python 3 it checks for these executables in this order:
python3, python3.6, python3.5 and python3.4.
Installing GPGME
See the GPGME README file for details of how to install GPGME from source.
Copyright and Licensing
Copyright (C) The GnuPG Project, 2018
Copyright © The GnuPG Project, 2018.
License TBA
Which license shall we use for these docs, hmm? Gotta be free, so that rules the GFDL out. I'll pick a CC or something later …