Add gnupg._trust module for functions dealing with trustdb.

* ADD function gnupg._trust._create_trustdb().
 * ADD function gnupg._trust.import_ownertrust().
 * ADD function gnupg._trust.export_ownertrust().
 * ADD function gnupg._trust.fix_trustdb().

gnupg/_trust.py

@@ -0,0 +1,102 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of python-gnupg, a Python interface to GnuPG.
+# Copyright © 2013 Isis Lovecruft, <isis@leap.se> 0xA3ADB67A2CDB8B35
+#           © 2013 Andrej B.
+#           © 2013 LEAP Encryption Access Project
+#           © 2008-2012 Vinay Sajip
+#           © 2005 Steve Traugott
+#           © 2004 A.M. Kuchling
+# 
+# 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 3 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 included LICENSE file for details.
+
+'''trust.py
+-----------
+Functions for handling trustdb and trust calculations.
+
+The functions within this module take an instance of :class:`gnupg.GPGBase` or
+a suitable subclass as their first argument.
+'''
+
+from __future__ import absolute_import
+
+import os
+
+from .      import _util
+from ._util import log
+
+def _create_trustdb(cls):
+    """Create the trustdb file in our homedir, if it doesn't exist."""
+    trustdb = os.path.join(cls.homedir, 'trustdb.gpg')
+    if not os.path.isfile(trustdb):
+        log.info("GnuPG complained that your trustdb file was missing. %s"
+                 % "This is likely due to changing to a new homedir.")
+        log.info("Creating trustdb.gpg file in your GnuPG homedir.")
+        cls.fix_trustdb(trustdb)
+
+def export_ownertrust(cls, trustdb=None):
+    """Export ownertrust to a trustdb file.
+
+    If there is already a file named 'trustdb.gpg' in the current GnuPG
+    homedir, it will be renamed to 'trustdb.gpg.bak'.
+
+    :param string trustdb: The path to the trustdb.gpg file. If not given,
+        defaults to 'trustdb.gpg' in the current GnuPG homedir.
+    """
+    if trustdb is None:
+        trustdb = os.path.join(cls.homedir, 'trustdb.gpg')
+
+    try:
+        os.rename(trustdb, trustdb + '.bak')
+    except (OSError, IOError) as err:
+        log.debug(err.message)
+
+    export_proc = cls._open_subprocess('--export-ownertrust')
+    tdb = open(trustdb, 'wb')
+    _util._threaded_copy_data(export_proc.stdout, tdb)
+
+def import_ownertrust(self, trustdb=None):
+    """Import ownertrust from a trustdb file.
+
+    :param string trustdb: The path to the trustdb.gpg file. If not given,
+        defaults to 'trustdb.gpg' in the current GnuPG homedir.
+    """
+    if trustdb is None:
+        trustdb = os.path.join(cls.homedir, 'trustdb.gpg')
+
+    import_proc = cls._open_subprocess('--import-ownertrust')
+    tdb = open(trustdb, 'rb')
+    _util._threaded_copy_data(tdb, import_proc.stdin)
+
+def fix_trustdb(cls, trustdb=None):
+    """Attempt to repair a broken trustdb.gpg file.
+
+    GnuPG>=2.0.x has this magical-seeming flag: '--fix-trustdb'. You'd think
+    it would fix the the trustdb. Hah! It doesn't. Here's what it does
+    instead:
+
+    (python-gnupg)∃!isisⒶwintermute:(testing/digest-algo *$=)~/code/python-gnupg ∴ gpg2 --fix-trustdb
+    gpg: You may try to re-create the trustdb using the commands:
+    gpg:   cd ~/.gnupg
+    gpg:   gpg2 --export-ownertrust > otrust.tmp
+    gpg:   rm trustdb.gpg
+    gpg:   gpg2 --import-ownertrust < otrust.tmp
+    gpg: If that does not work, please consult the manual
+
+    Brilliant piece of software engineering right there.
+
+    :param string trustdb: The path to the trustdb.gpg file. If not given,
+        defaults to 'trustdb.gpg' in the current GnuPG homedir.
+    """
+    if trustdb is None:
+        trustdb = os.path.join(cls.homedir, 'trustdb.gpg')
+    export_proc = cls._open_subprocess('--export-ownertrust')
+    import_proc = cls._open_subprocess('--import-ownertrust')
+    _util._threaded_copy_data(export_proc.stdout, import_proc.stdin)