python bindings examples

* Added a secret key export variant which saves output as both GPG
  binary and ASCII armoured, plus saves in $GNUPGHOME and uses
  multiple methods of determining what that location is.

lang/python/examples/howto/export-secret-keys.py

@@ -0,0 +1,110 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+from __future__ import absolute_import, division, unicode_literals
+
+# Copyright (C) 2018 Ben McGinnes <ben@gnupg.org>
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation; either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License and the GNU
+# Lesser General Public Licensefor more details.
+#
+# You should have received a copy of the GNU General Public License and the GNU
+# Lesser General Public along with this program; if not, see
+# <http://www.gnu.org/licenses/>.
+
+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