Merge branch 'master' of ssh://leap.se/leap_client

1 files changed, 636 insertions, 0 deletions

diff --git a/src/leap/keymanager/openpgp.py b/src/leap/keymanager/openpgp.py
new file mode 100644
index 00000000..89323117
--- /dev/null
+++ b/src/leap/keymanager/openpgp.py
@@ -0,0 +1,636 @@
+# -*- coding: utf-8 -*-
+# openpgp.py
+# Copyright (C) 2013 LEAP
+#
+# 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
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Infrastructure for using OpenPGP keys in Key Manager.
+"""
+import logging
+import os
+import re
+import shutil
+import tempfile
+
+from leap.common.check import leap_assert, leap_assert_type
+from leap.keymanager import errors
+from leap.keymanager.keys import (
+    EncryptionKey,
+    EncryptionScheme,
+    is_address,
+    build_key_from_dict,
+    KEYMANAGER_KEY_TAG,
+    TAGS_ADDRESS_PRIVATE_INDEX,
+)
+from leap.keymanager.gpg import GPGWrapper
+
+logger = logging.getLogger(__name__)
+
+
+#
+# gpg wrapper and decorator
+#
+
+def temporary_gpgwrapper(keys=None):
+    """
+    Returns a unitary gpg wrapper that implements context manager
+    protocol.
+
+    :param key_data: ASCII armored key data.
+    :type key_data: str
+
+    :return: a GPGWrapper instance
+    :rtype: GPGWrapper
+    """
+    # TODO do here checks on key_data
+    return TempGPGWrapper(keys=keys)
+
+
+def with_temporary_gpg(fun):
+    """
+    Decorator to add a temporary gpg wrapper as context
+    to gpg related functions.
+
+    Decorated functions are expected to return a function whose only
+    argument is a gpgwrapper instance.
+    """
+    def wrapped(*args, **kwargs):
+        """
+        We extract the arguments passed to the wrapped function,
+        run the function and do validations.
+        We expect that the positional arguments are `data`,
+        and an optional `key`.
+        All the rest of arguments should be passed as named arguments
+        to allow for a correct unpacking.
+        """
+        if len(args) == 2:
+            keys = args[1] if isinstance(args[1], OpenPGPKey) else None
+        else:
+            keys = None
+
+        # sign/verify keys passed as arguments
+        sign = kwargs.get('sign', None)
+        if sign:
+            keys = [keys, sign]
+
+        verify = kwargs.get('verify', None)
+        if verify:
+            keys = [keys, verify]
+
+        # is the wrapped function sign or verify?
+        fun_name = fun.__name__
+        is_sign_function = True if fun_name == "sign" else False
+        is_verify_function = True if fun_name == "verify" else False
+
+        result = None
+
+        with temporary_gpgwrapper(keys) as gpg:
+            result = fun(*args, **kwargs)(gpg)
+
+            # TODO: cleanup a little bit the
+            # validation. maybe delegate to other
+            # auxiliary functions for clarity.
+
+            ok = getattr(result, 'ok', None)
+
+            stderr = getattr(result, 'stderr', None)
+            if stderr:
+                logger.debug("%s" % (stderr,))
+
+            if ok is False:
+                raise errors.EncryptionDecryptionFailed(
+                    'Failed to encrypt/decrypt in %s: %s' % (
+                        fun.__name__,
+                        stderr))
+
+            if verify is not None:
+                # A verify key has been passed
+                if result.valid is False or \
+                        verify.fingerprint != result.pubkey_fingerprint:
+                    raise errors.InvalidSignature(
+                        'Failed to verify signature with key %s: %s' %
+                        (verify.key_id, stderr))
+
+            if is_sign_function:
+                # Specific validation for sign function
+                privkey = gpg.list_keys(secret=True).pop()
+                rfprint = result.fingerprint
+                kfprint = privkey['fingerprint']
+                if result.fingerprint is None:
+                    raise errors.SignFailed(
+                        'Failed to sign with key %s: %s' %
+                        (privkey['keyid'], stderr))
+                leap_assert(
+                    result.fingerprint == kfprint,
+                    'Signature and private key fingerprints mismatch: '
+                    '%s != %s' %
+                    (rfprint, kfprint))
+
+            if is_verify_function:
+                # Specific validation for verify function
+                pubkey = gpg.list_keys().pop()
+                valid = result.valid
+                rfprint = result.fingerprint
+                kfprint = pubkey['fingerprint']
+                if valid is False or rfprint != kfprint:
+                    raise errors.InvalidSignature(
+                        'Failed to verify signature '
+                        'with key %s.' % pubkey['keyid'])
+                result = result.valid
+
+            # ok, enough checks. let's return data if available
+            if hasattr(result, 'data'):
+                result = result.data
+        return result
+    return wrapped
+
+
+class TempGPGWrapper(object):
+    """
+    A context manager returning a temporary GPG wrapper keyring, which
+    contains exactly zero or one pubkeys, and zero or one privkeys.
+
+    Temporary unitary keyrings allow the to use GPG's facilities for exactly
+    one key. This function creates an empty temporary keyring and imports
+    C{keys} if it is not None.
+    """
+    def __init__(self, keys=None):
+        """
+        :param keys: OpenPGP key, or list of.
+        :type keys: OpenPGPKey or list of OpenPGPKeys
+        """
+        self._gpg = None
+        if not keys:
+            keys = list()
+        if not isinstance(keys, list):
+            keys = [keys]
+        self._keys = keys
+        for key in filter(None, keys):
+            leap_assert_type(key, OpenPGPKey)
+
+    def __enter__(self):
+        """
+        Calls the unitary gpgwrapper initializer
+
+        :return: A GPG wrapper with a unitary keyring.
+        :rtype: gnupg.GPG
+        """
+        self._build_keyring()
+        return self._gpg
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        """
+        Ensures the gpgwrapper is properly destroyed.
+        """
+        # TODO handle exceptions and log here
+        self._destroy_keyring()
+
+    def _build_keyring(self):
+        """
+        Create an empty GPG keyring and import C{keys} into it.
+
+        :param keys: List of keys to add to the keyring.
+        :type keys: list of OpenPGPKey
+
+        :return: A GPG wrapper with a unitary keyring.
+        :rtype: gnupg.GPG
+        """
+        privkeys = [key for key in self._keys if key and key.private is True]
+        publkeys = [key for key in self._keys if key and key.private is False]
+        # here we filter out public keys that have a correspondent
+        # private key in the list because the private key_data by
+        # itself is enough to also have the public key in the keyring,
+        # and we want to count the keys afterwards.
+
+        privaddrs = map(lambda privkey: privkey.address, privkeys)
+        publkeys = filter(
+            lambda pubkey: pubkey.address not in privaddrs, publkeys)
+
+        listkeys = lambda: self._gpg.list_keys()
+        listsecretkeys = lambda: self._gpg.list_keys(secret=True)
+
+        self._gpg = GPGWrapper(gnupghome=tempfile.mkdtemp())
+        leap_assert(len(listkeys()) is 0, 'Keyring not empty.')
+
+        # import keys into the keyring:
+        # concatenating ascii-armored keys, which is correctly
+        # understood by the GPGWrapper.
+
+        self._gpg.import_keys("".join(
+            [x.key_data for x in publkeys + privkeys]))
+
+        # assert the number of keys in the keyring
+        leap_assert(
+            len(listkeys()) == len(publkeys) + len(privkeys),
+            'Wrong number of public keys in keyring: %d, should be %d)' %
+            (len(listkeys()), len(publkeys) + len(privkeys)))
+        leap_assert(
+            len(listsecretkeys()) == len(privkeys),
+            'Wrong number of private keys in keyring: %d, should be %d)' %
+            (len(listsecretkeys()), len(privkeys)))
+
+    def _destroy_keyring(self):
+        """
+        Securely erase a unitary keyring.
+        """
+        # TODO: implement some kind of wiping of data or a more
+        # secure way that
+        # does not write to disk.
+
+        try:
+            for secret in [True, False]:
+                for key in self._gpg.list_keys(secret=secret):
+                    self._gpg.delete_keys(
+                        key['fingerprint'],
+                        secret=secret)
+            leap_assert(len(self._gpg.list_keys()) is 0, 'Keyring not empty!')
+
+        except:
+            raise
+
+        finally:
+            leap_assert(self._gpg.gnupghome != os.path.expanduser('~/.gnupg'),
+                        "watch out! Tried to remove default gnupg home!")
+            shutil.rmtree(self._gpg.gnupghome)
+
+
+#
+# API functions
+#
+
+@with_temporary_gpg
+def encrypt_asym(data, key, passphrase=None, sign=None):
+    """
+    Encrypt C{data} using public @{key} and sign with C{sign} key.
+
+    :param data: The data to be encrypted.
+    :type data: str
+    :param pubkey: The key used to encrypt.
+    :type pubkey: OpenPGPKey
+    :param sign: The key used for signing.
+    :type sign: OpenPGPKey
+
+    :return: The encrypted data.
+    :rtype: str
+    """
+    leap_assert_type(key, OpenPGPKey)
+    leap_assert(key.private is False, 'Key is not public.')
+    if sign is not None:
+        leap_assert_type(sign, OpenPGPKey)
+        leap_assert(sign.private is True)
+
+    # Here we cannot assert for correctness of sig because the sig is in
+    # the ciphertext.
+    # result.ok    - (bool) indicates if the operation succeeded
+    # result.data  - (bool) contains the result of the operation
+
+    return lambda gpg: gpg.encrypt(
+        data, key.fingerprint,
+        sign=sign.key_id if sign else None,
+        passphrase=passphrase, symmetric=False)
+
+
+@with_temporary_gpg
+def decrypt_asym(data, key, passphrase=None, verify=None):
+    """
+    Decrypt C{data} using private @{key} and verify with C{verify} key.
+
+    :param data: The data to be decrypted.
+    :type data: str
+    :param privkey: The key used to decrypt.
+    :type privkey: OpenPGPKey
+    :param verify: The key used to verify a signature.
+    :type verify: OpenPGPKey
+
+    :return: The decrypted data.
+    :rtype: str
+
+    @raise InvalidSignature: Raised if unable to verify the signature with
+        C{verify} key.
+    """
+    leap_assert(key.private is True, 'Key is not private.')
+    if verify is not None:
+        leap_assert_type(verify, OpenPGPKey)
+        leap_assert(verify.private is False)
+
+    return lambda gpg: gpg.decrypt(
+        data, passphrase=passphrase)
+
+
+@with_temporary_gpg
+def is_encrypted(data):
+    """
+    Return whether C{data} was encrypted using OpenPGP.
+
+    :param data: The data we want to know about.
+    :type data: str
+
+    :return: Whether C{data} was encrypted using this wrapper.
+    :rtype: bool
+    """
+    return lambda gpg: gpg.is_encrypted(data)
+
+
+@with_temporary_gpg
+def is_encrypted_asym(data):
+    """
+    Return whether C{data} was asymmetrically encrypted using OpenPGP.
+
+    :param data: The data we want to know about.
+    :type data: str
+
+    :return: Whether C{data} was encrypted using this wrapper.
+    :rtype: bool
+    """
+    return lambda gpg: gpg.is_encrypted_asym(data)
+
+
+@with_temporary_gpg
+def sign(data, privkey):
+    """
+    Sign C{data} with C{privkey}.
+
+    :param data: The data to be signed.
+    :type data: str
+
+    :param privkey: The private key to be used to sign.
+    :type privkey: OpenPGPKey
+
+    :return: The ascii-armored signed data.
+    :rtype: str
+    """
+    leap_assert_type(privkey, OpenPGPKey)
+    leap_assert(privkey.private is True)
+
+    # result.fingerprint - contains the fingerprint of the key used to
+    #                      sign.
+    return lambda gpg: gpg.sign(data, keyid=privkey.key_id)
+
+
+@with_temporary_gpg
+def verify(data, key):
+    """
+    Verify signed C{data} with C{pubkey}.
+
+    :param data: The data to be verified.
+    :type data: str
+
+    :param pubkey: The public key to be used on verification.
+    :type pubkey: OpenPGPKey
+
+    :return: The ascii-armored signed data.
+    :rtype: str
+    """
+    leap_assert_type(key, OpenPGPKey)
+    leap_assert(key.private is False)
+
+    return lambda gpg: gpg.verify(data)
+
+
+#
+# Helper functions
+#
+
+
+def _build_key_from_gpg(address, key, key_data):
+    """
+    Build an OpenPGPKey for C{address} based on C{key} from
+    local gpg storage.
+
+    ASCII armored GPG key data has to be queried independently in this
+    wrapper, so we receive it in C{key_data}.
+
+    :param address: The address bound to the key.
+    :type address: str
+    :param key: Key obtained from GPG storage.
+    :type key: dict
+    :param key_data: Key data obtained from GPG storage.
+    :type key_data: str
+    :return: An instance of the key.
+    :rtype: OpenPGPKey
+    """
+    return OpenPGPKey(
+        address,
+        key_id=key['keyid'],
+        fingerprint=key['fingerprint'],
+        key_data=key_data,
+        private=True if key['type'] == 'sec' else False,
+        length=key['length'],
+        expiry_date=key['expires'],
+        validation=None,  # TODO: verify for validation.
+    )
+
+
+#
+# The OpenPGP wrapper
+#
+
+class OpenPGPKey(EncryptionKey):
+    """
+    Base class for OpenPGP keys.
+    """
+
+
+class OpenPGPScheme(EncryptionScheme):
+    """
+    A wrapper for OpenPGP keys.
+    """
+
+    def __init__(self, soledad):
+        """
+        Initialize the OpenPGP wrapper.
+
+        :param soledad: A Soledad instance for key storage.
+        :type soledad: leap.soledad.Soledad
+        """
+        EncryptionScheme.__init__(self, soledad)
+
+    def gen_key(self, address):
+        """
+        Generate an OpenPGP keypair bound to C{address}.
+
+        :param address: The address bound to the key.
+        :type address: str
+        :return: The key bound to C{address}.
+        :rtype: OpenPGPKey
+        @raise KeyAlreadyExists: If key already exists in local database.
+        """
+        # make sure the key does not already exist
+        leap_assert(is_address(address), 'Not an user address: %s' % address)
+        try:
+            self.get_key(address)
+            raise errors.KeyAlreadyExists(address)
+        except errors.KeyNotFound:
+            pass
+
+        def _gen_key(gpg):
+            params = gpg.gen_key_input(
+                key_type='RSA',
+                key_length=4096,
+                name_real=address,
+                name_email=address,
+                name_comment='Generated by LEAP Key Manager.')
+            gpg.gen_key(params)
+            pubkeys = gpg.list_keys()
+            # assert for new key characteristics
+            leap_assert(
+                len(pubkeys) is 1,  # a unitary keyring!
+                'Keyring has wrong number of keys: %d.' % len(pubkeys))
+            key = gpg.list_keys(secret=True).pop()
+            leap_assert(
+                len(key['uids']) is 1,  # with just one uid!
+                'Wrong number of uids for key: %d.' % len(key['uids']))
+            leap_assert(
+                re.match('.*<%s>$' % address, key['uids'][0]) is not None,
+                'Key not correctly bound to address.')
+            # insert both public and private keys in storage
+            for secret in [True, False]:
+                key = gpg.list_keys(secret=secret).pop()
+                openpgp_key = _build_key_from_gpg(
+                    address, key,
+                    gpg.export_keys(key['fingerprint'], secret=secret))
+                self.put_key(openpgp_key)
+
+        with temporary_gpgwrapper() as gpg:
+            # TODO: inspect result, or use decorator
+            _gen_key(gpg)
+
+        return self.get_key(address, private=True)
+
+    def get_key(self, address, private=False):
+        """
+        Get key bound to C{address} from local storage.
+
+        :param address: The address bound to the key.
+        :type address: str
+        :param private: Look for a private key instead of a public one?
+        :type private: bool
+
+        :return: The key bound to C{address}.
+        :rtype: OpenPGPKey
+        @raise KeyNotFound: If the key was not found on local storage.
+        """
+        leap_assert(is_address(address), 'Not an user address: %s' % address)
+        doc = self._get_key_doc(address, private)
+        if doc is None:
+            raise errors.KeyNotFound(address)
+        return build_key_from_dict(OpenPGPKey, address, doc.content)
+
+    def put_ascii_key(self, key_data):
+        """
+        Put key contained in ascii-armored C{key_data} in local storage.
+
+        :param key_data: The key data to be stored.
+        :type key_data: str
+        """
+        leap_assert_type(key_data, str)
+        # TODO: add more checks for correct key data.
+        leap_assert(key_data is not None, 'Data does not represent a key.')
+
+        def _put_ascii_key(gpg):
+            gpg.import_keys(key_data)
+            privkey = None
+            pubkey = None
+
+            try:
+                privkey = gpg.list_keys(secret=True).pop()
+            except IndexError:
+                pass
+            pubkey = gpg.list_keys(secret=False).pop()  # unitary keyring
+            # extract adress from first uid on key
+            match = re.match('.*<([\w.-]+@[\w.-]+)>.*', pubkey['uids'].pop())
+            leap_assert(match is not None, 'No user address in key data.')
+            address = match.group(1)
+            if privkey is not None:
+                match = re.match(
+                    '.*<([\w.-]+@[\w.-]+)>.*', privkey['uids'].pop())
+                leap_assert(match is not None, 'No user address in key data.')
+                privaddress = match.group(1)
+                leap_assert(
+                    address == privaddress,
+                    'Addresses in pub and priv key differ.')
+                leap_assert(
+                    pubkey['fingerprint'] == privkey['fingerprint'],
+                    'Fingerprints for pub and priv key differ.')
+                # insert private key in storage
+                openpgp_privkey = _build_key_from_gpg(
+                    address, privkey,
+                    gpg.export_keys(privkey['fingerprint'], secret=True))
+                self.put_key(openpgp_privkey)
+            # insert public key in storage
+            openpgp_pubkey = _build_key_from_gpg(
+                address, pubkey,
+                gpg.export_keys(pubkey['fingerprint'], secret=False))
+            self.put_key(openpgp_pubkey)
+
+        with temporary_gpgwrapper() as gpg:
+            # TODO: inspect result, or use decorator
+            _put_ascii_key(gpg)
+
+    def put_key(self, key):
+        """
+        Put C{key} in local storage.
+
+        :param key: The key to be stored.
+        :type key: OpenPGPKey
+        """
+        doc = self._get_key_doc(key.address, private=key.private)
+        if doc is None:
+            self._soledad.create_doc_from_json(key.get_json())
+        else:
+            doc.set_json(key.get_json())
+            self._soledad.put_doc(doc)
+
+    def _get_key_doc(self, address, private=False):
+        """
+        Get the document with a key (public, by default) bound to C{address}.
+
+        If C{private} is True, looks for a private key instead of a public.
+
+        :param address: The address bound to the key.
+        :type address: str
+        :param private: Whether to look for a private key.
+        :type private: bool
+        :return: The document with the key or None if it does not exist.
+        :rtype: leap.soledad.backends.leap_backend.LeapDocument
+        """
+        doclist = self._soledad.get_from_index(
+            TAGS_ADDRESS_PRIVATE_INDEX,
+            KEYMANAGER_KEY_TAG,
+            address,
+            '1' if private else '0')
+        if len(doclist) is 0:
+            return None
+        leap_assert(
+            len(doclist) is 1,
+            'Found more than one %s key for address!' %
+            'private' if private else 'public')
+        return doclist.pop()
+
+    def delete_key(self, key):
+        """
+        Remove C{key} from storage.
+
+        :param key: The key to be removed.
+        :type key: EncryptionKey
+        """
+        leap_assert(key.__class__ is OpenPGPKey, 'Wrong key type.')
+        stored_key = self.get_key(key.address, private=key.private)
+        if stored_key is None:
+            raise errors.KeyNotFound(key)
+        if stored_key.__dict__ != key.__dict__:
+            raise errors.KeyAttributesDiffer(key)
+        doc = self._get_key_doc(key.address, key.private)
+        self._soledad.delete_doc(doc)