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Filename : core.py
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# -*- coding: utf-8 -*-

from __future__ import absolute_import, print_function, unicode_literals

import re
import os
import warnings
import weakref

from . import gpgme
from .errors import errorcheck, GPGMEError
from . import constants
from . import errors
from . import util

del absolute_import, print_function, unicode_literals

# Copyright (C) 2016-2018 g10 Code GmbH
# Copyright (C) 2004, 2008 Igor Belyi <belyi@users.sourceforge.net>
# Copyright (C) 2002 John Goerzen <jgoerzen@complete.org>
#
#    This library 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 library 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
#    Lesser General Public License for more details.
#
#    You should have received a copy of the GNU Lesser General Public
#    License along with this library; if not, write to the Free Software
#    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
"""Core functionality

Core functionality of GPGME wrapped in a object-oriented fashion.
Provides the 'Context' class for performing cryptographic operations,
and the 'Data' class describing buffers of data.

"""


class GpgmeWrapper(object):
    """Base wrapper class

    Not to be instantiated directly.

    """

    def __init__(self, wrapped):
        self._callback_excinfo = None
        self.wrapped = wrapped

    def __repr__(self):
        return '<{}/{!r}>'.format(
            super(GpgmeWrapper, self).__repr__(), self.wrapped)

    def __str__(self):
        acc = ['{}.{}'.format(__name__, self.__class__.__name__)]
        flags = [f for f in self._boolean_properties if getattr(self, f)]
        if flags:
            acc.append('({})'.format(' '.join(flags)))

        return '<{}>'.format(' '.join(acc))

    def __hash__(self):
        return hash(repr(self.wrapped))

    def __eq__(self, other):
        if other is None:
            return False
        else:
            return repr(self.wrapped) == repr(other.wrapped)

    @property
    def _ctype(self):
        """The name of the c type wrapped by this class

        Must be set by child classes.

        """
        raise NotImplementedError()

    @property
    def _cprefix(self):
        """The common prefix of c functions wrapped by this class

        Must be set by child classes.

        """
        raise NotImplementedError()

    def _errorcheck(self, name):
        """Must be implemented by child classes.

        This function must return a trueish value for all c functions
        returning gpgme_error_t."""
        raise NotImplementedError()

    """The set of all boolean properties"""
    _boolean_properties = set()

    def __wrap_boolean_property(self, key, do_set=False, value=None):
        get_func = getattr(gpgme, "{}get_{}".format(self._cprefix, key))
        set_func = getattr(gpgme, "{}set_{}".format(self._cprefix, key))

        def get(slf):
            return bool(get_func(slf.wrapped))

        def set_(slf, value):
            set_func(slf.wrapped, bool(value))

        p = property(get, set_, doc="{} flag".format(key))
        setattr(self.__class__, key, p)

        if do_set:
            set_(self, bool(value))
        else:
            return get(self)

    _munge_docstring = re.compile(r'gpgme_([^(]*)\(([^,]*), (.*\) -> .*)')

    def __getattr__(self, key):
        """On-the-fly generation of wrapper methods and properties"""
        if key[0] == '_' or self._cprefix is None:
            return None

        if key in self._boolean_properties:
            return self.__wrap_boolean_property(key)

        name = self._cprefix + key
        func = getattr(gpgme, name)

        if self._errorcheck(name):

            def _funcwrap(slf, *args):
                result = func(slf.wrapped, *args)
                if slf._callback_excinfo:
                    gpgme.gpg_raise_callback_exception(slf)
                return errorcheck(result, name)
        else:

            def _funcwrap(slf, *args):
                result = func(slf.wrapped, *args)
                if slf._callback_excinfo:
                    gpgme.gpg_raise_callback_exception(slf)
                return result

        doc = self._munge_docstring.sub(r'\2.\1(\3', getattr(func, "__doc__"))
        _funcwrap.__doc__ = doc

        # Monkey-patch the class.
        setattr(self.__class__, key, _funcwrap)

        # Bind the method to 'self'.
        def wrapper(*args):
            return _funcwrap(self, *args)

        wrapper.__doc__ = doc

        return wrapper

    def __setattr__(self, key, value):
        """On-the-fly generation of properties"""
        if key in self._boolean_properties:
            self.__wrap_boolean_property(key, True, value)
        else:
            super(GpgmeWrapper, self).__setattr__(key, value)


class Context(GpgmeWrapper):
    """Context for cryptographic operations

    All cryptographic operations in GPGME are performed within a
    context, which contains the internal state of the operation as
    well as configuration parameters.  By using several contexts you
    can run several cryptographic operations in parallel, with
    different configuration.

    Access to a context must be synchronized.

    """

    def __init__(self,
                 armor=False,
                 textmode=False,
                 offline=False,
                 signers=[],
                 pinentry_mode=constants.PINENTRY_MODE_DEFAULT,
                 protocol=constants.PROTOCOL_OpenPGP,
                 wrapped=None,
                 home_dir=None):
        """Construct a context object

        Keyword arguments:
        armor		-- enable ASCII armoring (default False)
        textmode	-- enable canonical text mode (default False)
        offline		-- do not contact external key sources (default False)
        signers		-- list of keys used for signing (default [])
        pinentry_mode	-- pinentry mode (default PINENTRY_MODE_DEFAULT)
        protocol	-- protocol to use (default PROTOCOL_OpenPGP)
        home_dir        -- state directory (default is the engine default)

        """
        if wrapped:
            self.own = False
        else:
            tmp = gpgme.new_gpgme_ctx_t_p()
            errorcheck(gpgme.gpgme_new(tmp))
            wrapped = gpgme.gpgme_ctx_t_p_value(tmp)
            gpgme.delete_gpgme_ctx_t_p(tmp)
            self.own = True
        super(Context, self).__init__(wrapped)
        self.armor = armor
        self.textmode = textmode
        self.offline = offline
        self.signers = signers
        self.pinentry_mode = pinentry_mode
        self.protocol = protocol
        self.home_dir = home_dir

    def __read__(self, sink, data):
        """Read helper

        Helper function to retrieve the results of an operation, or
        None if SINK is given.
        """
        if sink or data is None:
            return None
        data.seek(0, os.SEEK_SET)
        return data.read()

    def __repr__(self):
        return ("Context(armor={0.armor}, "
                "textmode={0.textmode}, offline={0.offline}, "
                "signers={0.signers}, pinentry_mode={0.pinentry_mode}, "
                "protocol={0.protocol}, home_dir={0.home_dir}"
                ")").format(self)

    def encrypt(self,
                plaintext,
                recipients=[],
                sign=True,
                sink=None,
                passphrase=None,
                always_trust=False,
                add_encrypt_to=False,
                prepare=False,
                expect_sign=False,
                compress=True):
        """Encrypt data

        Encrypt the given plaintext for the given recipients.  If the
        list of recipients is empty, the data is encrypted
        symmetrically with a passphrase.

        The passphrase can be given as parameter, using a callback
        registered at the context, or out-of-band via pinentry.

        Keyword arguments:
        recipients	-- list of keys to encrypt to
        sign		-- sign plaintext (default True)
        sink		-- write result to sink instead of returning it
        passphrase	-- for symmetric encryption
        always_trust	-- always trust the keys (default False)
        add_encrypt_to	-- encrypt to configured additional keys (default False)
        prepare		-- (ui) prepare for encryption (default False)
        expect_sign	-- (ui) prepare for signing (default False)
        compress	-- compress plaintext (default True)

        Returns:
        ciphertext	-- the encrypted data (or None if sink is given)
        result		-- additional information about the encryption
        sign_result	-- additional information about the signature(s)

        Raises:
        InvalidRecipients -- if encryption using a particular key failed
        InvalidSigners	-- if signing using a particular key failed
        GPGMEError	-- as signaled by the underlying library

        """
        ciphertext = sink if sink else Data()
        flags = 0
        flags |= always_trust * constants.ENCRYPT_ALWAYS_TRUST
        flags |= (not add_encrypt_to) * constants.ENCRYPT_NO_ENCRYPT_TO
        flags |= prepare * constants.ENCRYPT_PREPARE
        flags |= expect_sign * constants.ENCRYPT_EXPECT_SIGN
        flags |= (not compress) * constants.ENCRYPT_NO_COMPRESS

        if passphrase is not None:
            old_pinentry_mode = self.pinentry_mode
            old_passphrase_cb = getattr(self, '_passphrase_cb', None)
            self.pinentry_mode = constants.PINENTRY_MODE_LOOPBACK

            def passphrase_cb(hint, desc, prev_bad, hook=None):
                return passphrase

            self.set_passphrase_cb(passphrase_cb)

        try:
            if sign:
                self.op_encrypt_sign(recipients, flags, plaintext, ciphertext)
            else:
                self.op_encrypt(recipients, flags, plaintext, ciphertext)
        except errors.GPGMEError as e:
            result = self.op_encrypt_result()
            sig_result = self.op_sign_result() if sign else None
            results = (self.__read__(sink, ciphertext), result, sig_result)
            if e.getcode() == errors.UNUSABLE_PUBKEY:
                if result.invalid_recipients:
                    raise errors.InvalidRecipients(
                        result.invalid_recipients,
                        error=e.error,
                        results=results)
            if e.getcode() == errors.UNUSABLE_SECKEY:
                sig_result = self.op_sign_result()
                if sig_result.invalid_signers:
                    raise errors.InvalidSigners(
                        sig_result.invalid_signers,
                        error=e.error,
                        results=results)
            # Otherwise, just raise the error, but attach the results
            # first.
            e.results = results
            raise e
        finally:
            if passphrase is not None:
                self.pinentry_mode = old_pinentry_mode
                if old_passphrase_cb:
                    self.set_passphrase_cb(*old_passphrase_cb[1:])

        result = self.op_encrypt_result()
        assert not result.invalid_recipients
        sig_result = self.op_sign_result() if sign else None
        assert not sig_result or not sig_result.invalid_signers

        return self.__read__(sink, ciphertext), result, sig_result

    def decrypt(self, ciphertext, sink=None, passphrase=None, verify=True):
        """Decrypt data

        Decrypt the given ciphertext and verify any signatures.  If
        VERIFY is an iterable of keys, the ciphertext must be signed
        by all those keys, otherwise a MissingSignatures error is
        raised.  Note: if VERIFY is an empty iterable, that is treated
        the same as passing verify=True (that is, verify signatures
        and return data about any valid signatures found, but no
        signatures are required and no MissingSignatures error will be
        raised).

        If the ciphertext is symmetrically encrypted using a
        passphrase, that passphrase can be given as parameter, using a
        callback registered at the context, or out-of-band via
        pinentry.

        Keyword arguments:
        sink            -- write result to sink instead of returning it
        passphrase      -- for symmetric decryption
        verify          -- check signatures (boolean or iterable of keys,
                           see above) (default True)

        Returns:
        plaintext       -- the decrypted data (or None if sink is given)
        result          -- additional information about the decryption
        verify_result   -- additional information about the valid
                           signature(s) found

        Raises:
        UnsupportedAlgorithm -- if an unsupported algorithm was used
        MissingSignatures    -- if expected signatures are missing or bad
        GPGMEError           -- as signaled by the underlying library

        """
        do_sig_verification = False
        required_keys = None
        plaintext = sink if sink else Data()

        if passphrase is not None:
            old_pinentry_mode = self.pinentry_mode
            old_passphrase_cb = getattr(self, '_passphrase_cb', None)
            self.pinentry_mode = constants.PINENTRY_MODE_LOOPBACK

            def passphrase_cb(hint, desc, prev_bad, hook=None):
                return passphrase

            self.set_passphrase_cb(passphrase_cb)

        try:
            if isinstance(verify, bool):
                do_sig_verification = verify
            elif verify is None:
                warnings.warn(
                    "ctx.decrypt called with verify=None, should be bool or iterable (treating as False).",
                    category=DeprecationWarning)
                do_sig_verification = False
            else:
                # we hope this is an iterable:
                required_keys = verify
                do_sig_verification = True

            if do_sig_verification:
                self.op_decrypt_verify(ciphertext, plaintext)
            else:
                self.op_decrypt(ciphertext, plaintext)
        except errors.GPGMEError as e:
            result = self.op_decrypt_result()
            if do_sig_verification:
                verify_result = self.op_verify_result()
            else:
                verify_result = None
            # Just raise the error, but attach the results first.
            e.results = (self.__read__(sink, plaintext), result, verify_result)
            raise e
        finally:
            if passphrase is not None:
                self.pinentry_mode = old_pinentry_mode
                if old_passphrase_cb:
                    self.set_passphrase_cb(*old_passphrase_cb[1:])

        result = self.op_decrypt_result()

        if do_sig_verification:
            verify_result = self.op_verify_result()
        else:
            verify_result = None

        results = (self.__read__(sink, plaintext), result, verify_result)

        if result.unsupported_algorithm:
            raise errors.UnsupportedAlgorithm(result.unsupported_algorithm,
                                              results=results)

        if do_sig_verification:
            # filter out all invalid signatures
            verify_result.signatures = list(filter(lambda s: s.status == errors.NO_ERROR, verify_result.signatures))
            if required_keys is not None:
                missing = []
                for key in required_keys:
                    ok = False
                    for subkey in key.subkeys:
                        for sig in verify_result.signatures:
                            if sig.summary & constants.SIGSUM_VALID == 0:
                                continue
                            if subkey.can_sign and subkey.fpr == sig.fpr:
                                ok = True
                            break
                        if ok:
                            break
                    if not ok:
                        missing.append(key)
                if missing:
                    raise errors.MissingSignatures(verify_result, missing,
                                                   results=results)

        return results

    def sign(self, data, sink=None, mode=constants.SIG_MODE_NORMAL):
        """Sign data

        Sign the given data with either the configured default local
        key, or the 'signers' keys of this context.

        Keyword arguments:
        mode		-- signature mode (default: normal, see below)
        sink		-- write result to sink instead of returning it

        Returns:
        either
          signed_data	-- encoded data and signature (normal mode)
          signature	-- only the signature data (detached mode)
          cleartext	-- data and signature as text (cleartext mode)
            (or None if sink is given)
        result		-- additional information about the signature(s)

        Raises:
        InvalidSigners	-- if signing using a particular key failed
        GPGMEError	-- as signaled by the underlying library

        """
        signeddata = sink if sink else Data()

        try:
            self.op_sign(data, signeddata, mode)
        except errors.GPGMEError as e:
            results = (self.__read__(sink, signeddata), self.op_sign_result())
            if e.getcode() == errors.UNUSABLE_SECKEY:
                if results[1].invalid_signers:
                    raise errors.InvalidSigners(
                        results[1].invalid_signers,
                        error=e.error,
                        results=results)
            e.results = results
            raise e

        result = self.op_sign_result()
        assert not result.invalid_signers

        return self.__read__(sink, signeddata), result

    def verify(self, signed_data, signature=None, sink=None, verify=[]):
        """Verify signatures

        Verify signatures over data.  If VERIFY is an iterable of
        keys, the ciphertext must be signed by all those keys,
        otherwise an error is raised.

        Keyword arguments:
        signature	-- detached signature data
        sink		-- write result to sink instead of returning it

        Returns:
        data		-- the plain data
            (or None if sink is given, or we verified a detached signature)
        result		-- additional information about the signature(s)

        Raises:
        BadSignatures	-- if a bad signature is encountered
        MissingSignatures -- if expected signatures are missing or bad
        GPGMEError	-- as signaled by the underlying library

        """
        if signature:
            # Detached signature, we don't return the plain text.
            data = None
        else:
            data = sink if sink else Data()

        try:
            if signature:
                self.op_verify(signature, signed_data, None)
            else:
                self.op_verify(signed_data, None, data)
        except errors.GPGMEError as e:
            # Just raise the error, but attach the results first.
            e.results = (self.__read__(sink, data), self.op_verify_result())
            raise e

        results = (self.__read__(sink, data), self.op_verify_result())
        if any(s.status != errors.NO_ERROR for s in results[1].signatures):
            raise errors.BadSignatures(results[1], results=results)

        missing = list()
        for key in verify:
            ok = False
            for subkey in key.subkeys:
                for sig in results[1].signatures:
                    if sig.summary & constants.SIGSUM_VALID == 0:
                        continue
                    if subkey.can_sign and subkey.fpr == sig.fpr:
                        ok = True
                        break
                if ok:
                    break
            if not ok:
                missing.append(key)
        if missing:
            raise errors.MissingSignatures(
                results[1], missing, results=results)

        return results

    def key_import(self, data):
        """Import data

        Imports the given data into the Context.

        Returns:
                -- an object describing the results of imported or updated
                   keys

        Raises:
        TypeError      -- Very rarely.
        GPGMEError     -- as signaled by the underlying library:

                          Import status errors, when they occur, will usually
                          be of NODATA.  NO_PUBKEY indicates something
                          managed to run the function without any
                          arguments, while an argument of None triggers
                          the first NODATA of errors.GPGME in the
                          exception.
        """
        try:
            self.op_import(data)
            result = self.op_import_result()
            if result.considered == 0:
                status = constants.STATUS_IMPORT_PROBLEM
            else:
                status = constants.STATUS_KEY_CONSIDERED
        except Exception as e:
            if e == errors.GPGMEError:
                if e.code_str == "No data":
                    status = constants.STATUS_NODATA
                else:
                    status = constants.STATUS_FILE_ERROR
            elif e == TypeError and hasattr(data, "decode") is True:
                status = constants.STATUS_NO_PUBKEY
            elif e == TypeError and hasattr(data, "encode") is True:
                status = constants.STATUS_FILE_ERROR
            else:
                status = constants.STATUS_ERROR

        if status == constants.STATUS_KEY_CONSIDERED:
            import_result = result
        else:
            import_result = status

        return import_result

    def key_export(self, pattern=None):
        """Export keys.

        Exports public keys matching the pattern specified.  If no
        pattern is specified then exports all available keys.

        Keyword arguments:
        pattern	-- return keys matching pattern (default: all keys)

        Returns:
                -- A key block containing one or more OpenPGP keys in
                   either ASCII armoured or binary format as determined
                   by the Context().  If there are no matching keys it
                   returns None.

        Raises:
        GPGMEError     -- as signaled by the underlying library.
        """
        data = Data()
        mode = 0
        try:
            self.op_export(pattern, mode, data)
            data.seek(0, os.SEEK_SET)
            pk_result = data.read()
        except GPGMEError as e:
            pk_result = e

        if len(pk_result) > 0:
            result = pk_result
        else:
            result = None

        return result

    def key_export_minimal(self, pattern=None):
        """Export keys.

        Exports public keys matching the pattern specified in a
        minimised format.  If no pattern is specified then exports all
        available keys.

        Keyword arguments:
        pattern	-- return keys matching pattern (default: all keys)

        Returns:
                -- A key block containing one or more minimised OpenPGP
                   keys in either ASCII armoured or binary format as
                   determined by the Context().  If there are no matching
                   keys it returns None.

        Raises:
        GPGMEError     -- as signaled by the underlying library.
        """
        data = Data()
        mode = gpgme.GPGME_EXPORT_MODE_MINIMAL
        try:
            self.op_export(pattern, mode, data)
            data.seek(0, os.SEEK_SET)
            pk_result = data.read()
        except GPGMEError as e:
            pk_result = e

        if len(pk_result) > 0:
            result = pk_result
        else:
            result = None

        return result

    def key_export_secret(self, pattern=None):
        """Export secret keys.

        Exports secret keys matching the pattern specified.  If no
        pattern is specified then exports or attempts to export all
        available secret keys.

        IMPORTANT: Each secret key to be exported will prompt for its
        passphrase via an invocation of pinentry and gpg-agent.  If the
        passphrase is not entered or does not match then no data will be
        exported.  This is the same result as when specifying a pattern
        that is not matched by the available keys.

        Keyword arguments:
        pattern	-- return keys matching pattern (default: all keys)

        Returns:
                -- On success a key block containing one or more OpenPGP
                   secret keys in either ASCII armoured or binary format
                   as determined by the Context().
                -- On failure while not raising an exception, returns None.

        Raises:
        GPGMEError     -- as signaled by the underlying library.
        """
        data = Data()
        mode = gpgme.GPGME_EXPORT_MODE_SECRET
        try:
            self.op_export(pattern, mode, data)
            data.seek(0, os.SEEK_SET)
            sk_result = data.read()
        except GPGMEError as e:
            sk_result = e

        if len(sk_result) > 0:
            result = sk_result
        else:
            result = None

        return result

    def keylist(self,
                pattern=None,
                secret=False,
                mode=constants.keylist.mode.LOCAL,
                source=None):
        """List keys

        Keyword arguments:
        pattern	-- return keys matching pattern (default: all keys)
        secret	-- return only secret keys (default: False)
        mode    -- keylist mode (default: list local keys)
        source  -- read keys from source instead from the keyring
                       (all other options are ignored in this case)

        Returns:
                -- an iterator returning key objects

        Raises:
        GPGMEError	-- as signaled by the underlying library
        """
        if not source:
            self.set_keylist_mode(mode)
            self.op_keylist_start(pattern, secret)
        else:
            # Automatic wrapping of SOURCE is not possible here,
            # because the object must not be deallocated until the
            # iteration over the results ends.
            if not isinstance(source, Data):
                source = Data(file=source)
            self.op_keylist_from_data_start(source, 0)

        key = self.op_keylist_next()
        while key:
            yield key
            key = self.op_keylist_next()
        self.op_keylist_end()

    def create_key(self,
                   userid,
                   algorithm=None,
                   expires_in=0,
                   expires=True,
                   sign=False,
                   encrypt=False,
                   certify=False,
                   authenticate=False,
                   passphrase=None,
                   force=False):
        """Create a primary key

        Create a primary key for the user id USERID.

        ALGORITHM may be used to specify the public key encryption
        algorithm for the new key.  By default, a reasonable default
        is chosen.  You may use "future-default" to select an
        algorithm that will be the default in a future implementation
        of the engine.  ALGORITHM may be a string like "rsa", or
        "rsa2048" to explicitly request an algorithm and a key size.

        EXPIRES_IN specifies the expiration time of the key in number
        of seconds since the keys creation.  By default, a reasonable
        expiration time is chosen.  If you want to create a key that
        does not expire, use the keyword argument EXPIRES.

        SIGN, ENCRYPT, CERTIFY, and AUTHENTICATE can be used to
        request the capabilities of the new key.  If you don't request
        any, a reasonable set of capabilities is selected, and in case
        of OpenPGP, a subkey with a reasonable set of capabilities is
        created.

        If PASSPHRASE is None (the default), then the key will not be
        protected with a passphrase.  If PASSPHRASE is a string, it
        will be used to protect the key.  If PASSPHRASE is True, the
        passphrase must be supplied using a passphrase callback or
        out-of-band with a pinentry.

        Keyword arguments:
        algorithm    -- public key algorithm, see above (default: reasonable)
        expires_in   -- expiration time in seconds (default: reasonable)
        expires      -- whether or not the key should expire (default: True)
        sign         -- request the signing capability (see above)
        encrypt      -- request the encryption capability (see above)
        certify      -- request the certification capability (see above)
        authenticate -- request the authentication capability (see above)
        passphrase   -- protect the key with a passphrase (default: no
                        passphrase)
        force        -- force key creation even if a key with the same userid
                        exists (default: False)

        Returns:
                     -- an object describing the result of the key creation

        Raises:
        GPGMEError   -- as signaled by the underlying library

        """
        if util.is_a_string(passphrase):
            old_pinentry_mode = self.pinentry_mode
            old_passphrase_cb = getattr(self, '_passphrase_cb', None)
            self.pinentry_mode = constants.PINENTRY_MODE_LOOPBACK

            def passphrase_cb(hint, desc, prev_bad, hook=None):
                return passphrase

            self.set_passphrase_cb(passphrase_cb)

        try:
            self.op_createkey(
                userid,
                algorithm,
                0,  # reserved
                expires_in,
                None,  # extrakey
                ((constants.create.SIGN if sign else 0) |
                 (constants.create.ENCR if encrypt else 0) |
                 (constants.create.CERT if certify else 0) |
                 (constants.create.AUTH if authenticate else 0) |
                 (constants.create.NOPASSWD if passphrase is None else 0) |
                 (0 if expires else constants.create.NOEXPIRE) |
                 (constants.create.FORCE if force else 0)))
        finally:
            if util.is_a_string(passphrase):
                self.pinentry_mode = old_pinentry_mode
                if old_passphrase_cb:
                    self.set_passphrase_cb(*old_passphrase_cb[1:])

        return self.op_genkey_result()

    def create_subkey(self,
                      key,
                      algorithm=None,
                      expires_in=0,
                      expires=True,
                      sign=False,
                      encrypt=False,
                      authenticate=False,
                      passphrase=None):
        """Create a subkey

        Create a subkey for the given KEY.  As subkeys are a concept
        of OpenPGP, calling this is only valid for the OpenPGP
        protocol.

        ALGORITHM may be used to specify the public key encryption
        algorithm for the new subkey.  By default, a reasonable
        default is chosen.  You may use "future-default" to select an
        algorithm that will be the default in a future implementation
        of the engine.  ALGORITHM may be a string like "rsa", or
        "rsa2048" to explicitly request an algorithm and a key size.

        EXPIRES_IN specifies the expiration time of the subkey in
        number of seconds since the subkeys creation.  By default, a
        reasonable expiration time is chosen.  If you want to create a
        subkey that does not expire, use the keyword argument EXPIRES.

        SIGN, ENCRYPT, and AUTHENTICATE can be used to request the
        capabilities of the new subkey.  If you don't request any, an
        encryption subkey is generated.

        If PASSPHRASE is None (the default), then the subkey will not
        be protected with a passphrase.  If PASSPHRASE is a string, it
        will be used to protect the subkey.  If PASSPHRASE is True,
        the passphrase must be supplied using a passphrase callback or
        out-of-band with a pinentry.

        Keyword arguments:
        algorithm    -- public key algorithm, see above (default: reasonable)
        expires_in   -- expiration time in seconds (default: reasonable)
        expires      -- whether or not the subkey should expire (default: True)
        sign         -- request the signing capability (see above)
        encrypt      -- request the encryption capability (see above)
        authenticate -- request the authentication capability (see above)
        passphrase   -- protect the subkey with a passphrase (default: no
                        passphrase)

        Returns:
                     -- an object describing the result of the subkey creation

        Raises:
        GPGMEError   -- as signaled by the underlying library

        """
        if util.is_a_string(passphrase):
            old_pinentry_mode = self.pinentry_mode
            old_passphrase_cb = getattr(self, '_passphrase_cb', None)
            self.pinentry_mode = constants.PINENTRY_MODE_LOOPBACK

            def passphrase_cb(hint, desc, prev_bad, hook=None):
                return passphrase

            self.set_passphrase_cb(passphrase_cb)

        try:
            self.op_createsubkey(
                key,
                algorithm,
                0,  # reserved
                expires_in,
                ((constants.create.SIGN if sign else 0) |
                 (constants.create.ENCR if encrypt else 0) |
                 (constants.create.AUTH if authenticate else 0) |
                 (constants.create.NOPASSWD if passphrase is None else 0) |
                 (0 if expires else constants.create.NOEXPIRE)))
        finally:
            if util.is_a_string(passphrase):
                self.pinentry_mode = old_pinentry_mode
                if old_passphrase_cb:
                    self.set_passphrase_cb(*old_passphrase_cb[1:])

        return self.op_genkey_result()

    def key_add_uid(self, key, uid):
        """Add a UID

        Add the uid UID to the given KEY.  Calling this function is
        only valid for the OpenPGP protocol.

        Raises:
        GPGMEError   -- as signaled by the underlying library

        """
        self.op_adduid(key, uid, 0)

    def key_revoke_uid(self, key, uid):
        """Revoke a UID

        Revoke the uid UID from the given KEY.  Calling this function
        is only valid for the OpenPGP protocol.

        Raises:
        GPGMEError   -- as signaled by the underlying library

        """
        self.op_revuid(key, uid, 0)

    def key_sign(self, key, uids=None, expires_in=False, local=False):
        """Sign a key

        Sign a key with the current set of signing keys.  Calling this
        function is only valid for the OpenPGP protocol.

        If UIDS is None (the default), then all UIDs are signed.  If
        it is a string, then only the matching UID is signed.  If it
        is a list of strings, then all matching UIDs are signed.  Note
        that a case-sensitive exact string comparison is done.

        EXPIRES_IN specifies the expiration time of the signature in
        seconds.  If EXPIRES_IN is False, the signature does not
        expire.

        Keyword arguments:
        uids         -- user ids to sign, see above (default: sign all)
        expires_in   -- validity period of the signature in seconds
                                               (default: do not expire)
        local        -- create a local, non-exportable signature
                                               (default: False)

        Raises:
        GPGMEError   -- as signaled by the underlying library

        """
        flags = 0
        if uids is None or util.is_a_string(uids):
            pass  # through unchanged
        else:
            flags |= constants.keysign.LFSEP
            uids = "\n".join(uids)

        if not expires_in:
            flags |= constants.keysign.NOEXPIRE

        if local:
            flags |= constants.keysign.LOCAL

        self.op_keysign(key, uids, expires_in, flags)

    def key_tofu_policy(self, key, policy):
        """Set a keys' TOFU policy

        Set the TOFU policy associated with KEY to POLICY.  Calling
        this function is only valid for the OpenPGP protocol.

        Raises:
        GPGMEError   -- as signaled by the underlying library

        """
        self.op_tofu_policy(key, policy)

    def assuan_transact(self,
                        command,
                        data_cb=None,
                        inquire_cb=None,
                        status_cb=None):
        """Issue a raw assuan command

        This function can be used to issue a raw assuan command to the
        engine.

        If command is a string or bytes, it will be used as-is.  If it
        is an iterable of strings, it will be properly escaped and
        joined into an well-formed assuan command.

        Keyword arguments:
        data_cb		-- a callback receiving data lines
        inquire_cb	-- a callback providing more information
        status_cb	-- a callback receiving status lines

        Returns:
        result		-- the result of command as GPGMEError

        Raises:
        GPGMEError	-- as signaled by the underlying library

        """

        if util.is_a_string(command) or isinstance(command, bytes):
            cmd = command
        else:
            cmd = " ".join(util.percent_escape(f) for f in command)

        errptr = gpgme.new_gpgme_error_t_p()

        err = gpgme.gpgme_op_assuan_transact_ext(
            self.wrapped, cmd, (weakref.ref(self), data_cb)
            if data_cb else None, (weakref.ref(self), inquire_cb)
            if inquire_cb else None, (weakref.ref(self), status_cb)
            if status_cb else None, errptr)

        if self._callback_excinfo:
            gpgme.gpg_raise_callback_exception(self)

        errorcheck(err)

        status = gpgme.gpgme_error_t_p_value(errptr)
        gpgme.delete_gpgme_error_t_p(errptr)

        return GPGMEError(status) if status != 0 else None

    def interact(self, key, func, sink=None, flags=0, fnc_value=None):
        """Interact with the engine

        This method can be used to edit keys and cards interactively.
        KEY is the key to edit, FUNC is called repeatedly with two
        unicode arguments, 'keyword' and 'args'.  See the GPGME manual
        for details.

        Keyword arguments:
        sink		-- if given, additional output is written here
        flags		-- use constants.INTERACT_CARD to edit a card

        Raises:
        GPGMEError	-- as signaled by the underlying library

        """
        if key is None:
            raise ValueError("First argument cannot be None")

        if sink is None:
            sink = Data()

        if fnc_value:
            opaquedata = (weakref.ref(self), func, fnc_value)
        else:
            opaquedata = (weakref.ref(self), func)

        result = gpgme.gpgme_op_interact(self.wrapped, key, flags, opaquedata,
                                         sink)
        if self._callback_excinfo:
            gpgme.gpg_raise_callback_exception(self)
        errorcheck(result)

    @property
    def signers(self):
        """Keys used for signing"""
        return [self.signers_enum(i) for i in range(self.signers_count())]

    @signers.setter
    def signers(self, signers):
        old = self.signers
        self.signers_clear()
        try:
            for key in signers:
                self.signers_add(key)
        except:
            self.signers = old
            raise

    @property
    def pinentry_mode(self):
        """Pinentry mode"""
        return self.get_pinentry_mode()

    @pinentry_mode.setter
    def pinentry_mode(self, value):
        self.set_pinentry_mode(value)

    @property
    def protocol(self):
        """Protocol to use"""
        return self.get_protocol()

    @protocol.setter
    def protocol(self, value):
        errorcheck(gpgme.gpgme_engine_check_version(value))
        self.set_protocol(value)

    @property
    def home_dir(self):
        """Engine's home directory"""
        return self.engine_info.home_dir

    @home_dir.setter
    def home_dir(self, value):
        self.set_engine_info(self.protocol, home_dir=value)

    _ctype = 'gpgme_ctx_t'
    _cprefix = 'gpgme_'

    def _errorcheck(self, name):
        """This function should list all functions returning gpgme_error_t"""
        # The list of functions is created using:
        #
        # $ grep '^gpgme_error_t ' obj/lang/python/python3.5-gpg/gpgme.h \
        # | grep -v _op_ | awk "/\(gpgme_ctx/ { printf (\"'%s',\\n\", \$2) } "
        return ((name.startswith('gpgme_op_') and not
                 name.endswith('_result')) or name in {
                     'gpgme_new', 'gpgme_set_ctx_flag', 'gpgme_set_protocol',
                     'gpgme_set_sub_protocol', 'gpgme_set_keylist_mode',
                     'gpgme_set_pinentry_mode', 'gpgme_set_locale',
                     'gpgme_ctx_set_engine_info', 'gpgme_signers_add',
                     'gpgme_sig_notation_add', 'gpgme_set_sender',
                     'gpgme_cancel', 'gpgme_cancel_async', 'gpgme_get_key',
                     'gpgme_get_sig_key',
                })

    _boolean_properties = {'armor', 'textmode', 'offline'}

    def __del__(self):
        if not gpgme:
            # At interpreter shutdown, gpgme is set to NONE.
            return

        self._free_passcb()
        self._free_progresscb()
        self._free_statuscb()
        if self.own and self.wrapped and gpgme.gpgme_release:
            gpgme.gpgme_release(self.wrapped)
            self.wrapped = None

    # Implement the context manager protocol.
    def __enter__(self):
        return self

    def __exit__(self, type, value, tb):
        self.__del__()

    def op_keylist_all(self, *args, **kwargs):
        self.op_keylist_start(*args, **kwargs)
        key = self.op_keylist_next()
        while key:
            yield key
            key = self.op_keylist_next()
        self.op_keylist_end()

    def op_keylist_next(self):
        """Returns the next key in the list created
        by a call to op_keylist_start().  The object returned
        is of type Key."""
        ptr = gpgme.new_gpgme_key_t_p()
        try:
            errorcheck(gpgme.gpgme_op_keylist_next(self.wrapped, ptr))
            key = gpgme.gpgme_key_t_p_value(ptr)
        except errors.GPGMEError as excp:
            key = None
            if excp.getcode() != errors.EOF:
                raise excp
        gpgme.delete_gpgme_key_t_p(ptr)
        if key:
            key.__del__ = lambda self: gpgme.gpgme_key_unref(self)
            return key

    def get_key(self, fpr, secret=False):
        """Get a key given a fingerprint

        Keyword arguments:
        secret		-- to request a secret key

        Returns:
                        -- the matching key

        Raises:
        KeyError	-- if the key was not found
        GPGMEError	-- as signaled by the underlying library

        """
        ptr = gpgme.new_gpgme_key_t_p()

        try:
            errorcheck(gpgme.gpgme_get_key(self.wrapped, fpr, ptr, secret))
        except errors.GPGMEError as e:
            if e.getcode() == errors.EOF:
                raise errors.KeyNotFound(fpr)
            raise e

        key = gpgme.gpgme_key_t_p_value(ptr)
        gpgme.delete_gpgme_key_t_p(ptr)
        assert key
        key.__del__ = lambda self: gpgme.gpgme_key_unref(self)
        return key

    def op_trustlist_all(self, *args, **kwargs):
        self.op_trustlist_start(*args, **kwargs)
        trust = self.op_trustlist_next()
        while trust:
            yield trust
            trust = self.op_trustlist_next()
        self.op_trustlist_end()

    def op_trustlist_next(self):
        """Returns the next trust item in the list created
        by a call to op_trustlist_start().  The object returned
        is of type TrustItem."""
        ptr = gpgme.new_gpgme_trust_item_t_p()
        try:
            errorcheck(gpgme.gpgme_op_trustlist_next(self.wrapped, ptr))
            trust = gpgme.gpgme_trust_item_t_p_value(ptr)
        except errors.GPGMEError as excp:
            trust = None
            if excp.getcode() != errors.EOF:
                raise
        gpgme.delete_gpgme_trust_item_t_p(ptr)
        return trust

    def set_passphrase_cb(self, func, hook=None):
        """Sets the passphrase callback to the function specified by func.

        When the system needs a passphrase, it will call func with three args:
        hint, a string describing the key it needs the passphrase for;
        desc, a string describing the passphrase it needs;
        prev_bad, a boolean equal True if this is a call made after
        unsuccessful previous attempt.

        If hook has a value other than None it will be passed into the func
        as a forth argument.

        Please see the GPGME manual for more information.
        """
        if func is None:
            hookdata = None
        else:
            if hook is None:
                hookdata = (weakref.ref(self), func)
            else:
                hookdata = (weakref.ref(self), func, hook)
        gpgme.gpg_set_passphrase_cb(self, hookdata)

    def _free_passcb(self):
        if gpgme.gpg_set_passphrase_cb:
            self.set_passphrase_cb(None)

    def set_progress_cb(self, func, hook=None):
        """Sets the progress meter callback to the function specified by FUNC.
        If FUNC is None, the callback will be cleared.

        This function will be called to provide an interactive update
        of the system's progress.  The function will be called with
        three arguments, type, total, and current.  If HOOK is not
        None, it will be supplied as fourth argument.

        Please see the GPGME manual for more information.

        """
        if func is None:
            hookdata = None
        else:
            if hook is None:
                hookdata = (weakref.ref(self), func)
            else:
                hookdata = (weakref.ref(self), func, hook)
        gpgme.gpg_set_progress_cb(self, hookdata)

    def _free_progresscb(self):
        if gpgme.gpg_set_progress_cb:
            self.set_progress_cb(None)

    def set_status_cb(self, func, hook=None):
        """Sets the status callback to the function specified by FUNC.  If
        FUNC is None, the callback will be cleared.

        The function will be called with two arguments, keyword and
        args.  If HOOK is not None, it will be supplied as third
        argument.

        Please see the GPGME manual for more information.

        """
        if func is None:
            hookdata = None
        else:
            if hook is None:
                hookdata = (weakref.ref(self), func)
            else:
                hookdata = (weakref.ref(self), func, hook)
        gpgme.gpg_set_status_cb(self, hookdata)

    def _free_statuscb(self):
        if gpgme.gpg_set_status_cb:
            self.set_status_cb(None)

    @property
    def engine_info(self):
        """Configuration of the engine currently in use"""
        p = self.protocol
        infos = [i for i in self.get_engine_info() if i.protocol == p]
        assert len(infos) == 1
        return infos[0]

    def get_engine_info(self):
        """Get engine configuration

        Returns information about all configured and installed
        engines.

        Returns:
        infos		-- a list of engine infos

        """
        return gpgme.gpgme_ctx_get_engine_info(self.wrapped)

    def set_engine_info(self, proto, file_name=None, home_dir=None):
        """Change engine configuration

        Changes the configuration of the crypto engine implementing
        the protocol 'proto' for the context.

        Keyword arguments:
        file_name	-- engine program file name (unchanged if None)
        home_dir	-- configuration directory (unchanged if None)

        """
        self.ctx_set_engine_info(proto, file_name, home_dir)

    def wait(self, hang):
        """Wait for asynchronous call to finish. Wait forever if hang is True.
        Raises an exception on errors.

        Please read the GPGME manual for more information.

        """
        ptr = gpgme.new_gpgme_error_t_p()
        gpgme.gpgme_wait(self.wrapped, ptr, hang)
        status = gpgme.gpgme_error_t_p_value(ptr)
        gpgme.delete_gpgme_error_t_p(ptr)
        errorcheck(status)

    def op_edit(self, key, func, fnc_value, out):
        """Start key editing using supplied callback function

        Note: This interface is deprecated and will be removed with
        GPGME 1.8.  Please use .interact instead.  Furthermore, we
        implement this using gpgme_op_interact, so callbacks will get
        called with string keywords instead of numeric status
        messages.  Code that is using constants.STATUS_X or
        constants.status.X will continue to work, whereas code using
        magic numbers will break as a result.

        """
        warnings.warn(
            "Call to deprecated method op_edit.", category=DeprecationWarning)
        return self.interact(key, func, sink=out, fnc_value=fnc_value)


class Data(GpgmeWrapper):
    """Data buffer

    A lot of data has to be exchanged between the user and the crypto
    engine, like plaintext messages, ciphertext, signatures and
    information about the keys.  The technical details about
    exchanging the data information are completely abstracted by
    GPGME.  The user provides and receives the data via `gpgme_data_t'
    objects, regardless of the communication protocol between GPGME
    and the crypto engine in use.

    This Data class is the implementation of the GpgmeData objects.

    Please see the information about __init__ for instantiation.

    """

    _ctype = 'gpgme_data_t'
    _cprefix = 'gpgme_data_'

    def _errorcheck(self, name):
        """This function should list all functions returning gpgme_error_t"""
        # This list is compiled using
        #
        # $ grep -v '^gpgme_error_t ' obj/lang/python/python3.5-gpg/gpgme.h \
        #   | awk "/\(gpgme_data_t/ { printf (\"'%s',\\n\", \$2) } " \
        #   | sed "s/'\\*/'/"
        return name not in {
            'gpgme_data_read',
            'gpgme_data_write',
            'gpgme_data_seek',
            'gpgme_data_release',
            'gpgme_data_release_and_get_mem',
            'gpgme_data_get_encoding',
            'gpgme_data_get_file_name',
            'gpgme_data_set_flag',
            'gpgme_data_identify',
        }

    def __init__(self,
                 string=None,
                 file=None,
                 offset=None,
                 length=None,
                 cbs=None,
                 copy=True):
        """Initialize a new gpgme_data_t object.

        If no args are specified, make it an empty object.

        If string alone is specified, initialize it with the data
        contained there.

        If file, offset, and length are all specified, file must
        be either a filename or a file-like object, and the object
        will be initialized by reading the specified chunk from the file.

        If cbs is specified, it MUST be a tuple of the form:

        (read_cb, write_cb, seek_cb, release_cb[, hook])

        where the first four items are functions implementing reading,
        writing, seeking the data, and releasing any resources once
        the data object is deallocated.  The functions must match the
        following prototypes:

            def read(amount, hook=None):
                return <a b"bytes" object>

            def write(data, hook=None):
                return <the number of bytes written>

            def seek(offset, whence, hook=None):
                return <the new file position>

            def release(hook=None):
                <return value and exceptions are ignored>

        The functions may be bound methods.  In that case, you can
        simply use the 'self' reference instead of using a hook.

        If file is specified without any other arguments, then
        it must be a filename, and the object will be initialized from
        that file.

        """
        super(Data, self).__init__(None)
        self.data_cbs = None

        if cbs is not None:
            self.new_from_cbs(*cbs)
        elif string is not None:
            self.new_from_mem(string, copy)
        elif file is not None and offset is not None and length is not None:
            self.new_from_filepart(file, offset, length)
        elif file is not None:
            if util.is_a_string(file):
                self.new_from_file(file, copy)
            else:
                self.new_from_fd(file)
        else:
            self.new()

    def __del__(self):
        if not gpgme:
            # At interpreter shutdown, gpgme is set to NONE.
            return

        if self.wrapped is not None and gpgme.gpgme_data_release:
            gpgme.gpgme_data_release(self.wrapped)
            if self._callback_excinfo:
                gpgme.gpg_raise_callback_exception(self)
            self.wrapped = None
        self._free_datacbs()

    # Implement the context manager protocol.
    def __enter__(self):
        return self

    def __exit__(self, type, value, tb):
        self.__del__()

    def _free_datacbs(self):
        self._data_cbs = None

    def new(self):
        tmp = gpgme.new_gpgme_data_t_p()
        errorcheck(gpgme.gpgme_data_new(tmp))
        self.wrapped = gpgme.gpgme_data_t_p_value(tmp)
        gpgme.delete_gpgme_data_t_p(tmp)

    def new_from_mem(self, string, copy=True):
        tmp = gpgme.new_gpgme_data_t_p()
        errorcheck(
            gpgme.gpgme_data_new_from_mem(tmp, string, len(string), copy))
        self.wrapped = gpgme.gpgme_data_t_p_value(tmp)
        gpgme.delete_gpgme_data_t_p(tmp)

    def new_from_file(self, filename, copy=True):
        tmp = gpgme.new_gpgme_data_t_p()
        try:
            errorcheck(gpgme.gpgme_data_new_from_file(tmp, filename, copy))
        except errors.GPGMEError as e:
            if e.getcode() == errors.INV_VALUE and not copy:
                raise ValueError("delayed reads are not yet supported")
            else:
                raise e
        self.wrapped = gpgme.gpgme_data_t_p_value(tmp)
        gpgme.delete_gpgme_data_t_p(tmp)

    def new_from_cbs(self, read_cb, write_cb, seek_cb, release_cb, hook=None):
        tmp = gpgme.new_gpgme_data_t_p()
        if hook is not None:
            hookdata = (weakref.ref(self), read_cb, write_cb, seek_cb,
                        release_cb, hook)
        else:
            hookdata = (weakref.ref(self), read_cb, write_cb, seek_cb,
                        release_cb)
        gpgme.gpg_data_new_from_cbs(self, hookdata, tmp)
        self.wrapped = gpgme.gpgme_data_t_p_value(tmp)
        gpgme.delete_gpgme_data_t_p(tmp)

    def new_from_filepart(self, file, offset, length):
        """This wraps the GPGME gpgme_data_new_from_filepart() function.
        The argument "file" may be:

        * a string specifying a file name, or
        * a file-like object supporting the fileno() and the mode attribute.

        """

        tmp = gpgme.new_gpgme_data_t_p()
        filename = None
        fp = None

        if util.is_a_string(file):
            filename = file
        else:
            fp = gpgme.fdopen(file.fileno(), file.mode)
            if fp is None:
                raise ValueError("Failed to open file from %s arg %s" % (str(
                    type(file)), str(file)))

        errorcheck(
            gpgme.gpgme_data_new_from_filepart(tmp, filename, fp, offset,
                                               length))
        self.wrapped = gpgme.gpgme_data_t_p_value(tmp)
        gpgme.delete_gpgme_data_t_p(tmp)

    def new_from_fd(self, file):
        """This wraps the GPGME gpgme_data_new_from_fd() function.  The
        argument "file" must be a file-like object, supporting the
        fileno() method.

        """
        tmp = gpgme.new_gpgme_data_t_p()
        errorcheck(gpgme.gpgme_data_new_from_fd(tmp, file.fileno()))
        self.wrapped = gpgme.gpgme_data_t_p_value(tmp)
        gpgme.delete_gpgme_data_t_p(tmp)

    def new_from_stream(self, file):
        """This wrap around gpgme_data_new_from_stream is an alias for
        new_from_fd() method since in python there's no difference
        between file stream and file descriptor."""
        self.new_from_fd(file)

    def new_from_estream(self, file):
        """This wrap around gpgme_data_new_from_estream is an alias for
        new_from_fd() method since in python there's no difference
        between file stream and file descriptor, but using fd broke."""
        self.new_from_stream(file)

    def write(self, buffer):
        """Write buffer given as string or bytes.

        If a string is given, it is implicitly encoded using UTF-8."""
        written = gpgme.gpgme_data_write(self.wrapped, buffer)
        if written < 0:
            if self._callback_excinfo:
                gpgme.gpg_raise_callback_exception(self)
            else:
                raise GPGMEError.fromSyserror()
        return written

    def read(self, size=-1):
        """Read at most size bytes, returned as bytes.

        If the size argument is negative or omitted, read until EOF is reached.

        Returns the data read, or the empty string if there was no data
        to read before EOF was reached."""

        if size == 0:
            return ''

        if size > 0:
            try:
                result = gpgme.gpgme_data_read(self.wrapped, size)
            except:
                if self._callback_excinfo:
                    gpgme.gpg_raise_callback_exception(self)
                else:
                    raise
            return result
        else:
            chunks = []
            while True:
                try:
                    result = gpgme.gpgme_data_read(self.wrapped, 4096)
                except:
                    if self._callback_excinfo:
                        gpgme.gpg_raise_callback_exception(self)
                    else:
                        raise
                if len(result) == 0:
                    break
                chunks.append(result)
            return b''.join(chunks)


def pubkey_algo_string(subkey):
    """Return short algorithm string

    Return a public key algorithm string (e.g. "rsa2048") for a given
    SUBKEY.

    Returns:
    algo      - a string

    """
    return gpgme.gpgme_pubkey_algo_string(subkey)


def pubkey_algo_name(algo):
    """Return name of public key algorithm

    Return the name of the public key algorithm for a given numeric
    algorithm id ALGO (cf. RFC4880).

    Returns:
    algo      - a string

    """
    return gpgme.gpgme_pubkey_algo_name(algo)


def hash_algo_name(algo):
    """Return name of hash algorithm

    Return the name of the hash algorithm for a given numeric
    algorithm id ALGO (cf. RFC4880).

    Returns:
    algo      - a string

    """
    return gpgme.gpgme_hash_algo_name(algo)


def get_protocol_name(proto):
    """Get protocol description

    Get the string describing protocol PROTO.

    Returns:
    proto     - a string

    """
    return gpgme.gpgme_get_protocol_name(proto)


def addrspec_from_uid(uid):
    """Return the address spec

    Return the addr-spec (cf. RFC2822 section 4.3) from a user id UID.

    Returns:
    addr_spec - a string

    """
    return gpgme.gpgme_addrspec_from_uid(uid)


def check_version(version=None):
    return gpgme.gpgme_check_version(version)


# check_version also makes sure that several subsystems are properly
# initialized, and it must be run at least once before invoking any
# other function.  We do it here so that the user does not have to do
# it unless she really wants to check for a certain version.
check_version()


def engine_check_version(proto):
    try:
        errorcheck(gpgme.gpgme_engine_check_version(proto))
        return True
    except errors.GPGMEError:
        return False


def get_engine_info():
    ptr = gpgme.new_gpgme_engine_info_t_p()
    try:
        errorcheck(gpgme.gpgme_get_engine_info(ptr))
        info = gpgme.gpgme_engine_info_t_p_value(ptr)
    except errors.GPGMEError:
        info = None
    gpgme.delete_gpgme_engine_info_t_p(ptr)
    return info


def set_engine_info(proto, file_name, home_dir=None):
    """Changes the default configuration of the crypto engine implementing
    the protocol 'proto'. 'file_name' is the file name of
    the executable program implementing this protocol. 'home_dir' is the
    directory name of the configuration directory (engine's default is
    used if omitted)."""
    errorcheck(gpgme.gpgme_set_engine_info(proto, file_name, home_dir))


def set_locale(category, value):
    """Sets the default locale used by contexts"""
    errorcheck(gpgme.gpgme_set_locale(None, category, value))


def wait(hang):
    """Wait for asynchronous call on any Context  to finish.
    Wait forever if hang is True.

    For finished anynch calls it returns a tuple (status, context):
        status  - status return by asnynchronous call.
        context - context which caused this call to return.

    Please read the GPGME manual of more information."""
    ptr = gpgme.new_gpgme_error_t_p()
    context = gpgme.gpgme_wait(None, ptr, hang)
    status = gpgme.gpgme_error_t_p_value(ptr)
    gpgme.delete_gpgme_error_t_p(ptr)
    if context is None:
        errorcheck(status)
    else:
        context = Context(context)
    return (status, context)