path: root/client/src/leap/soledad/client/api.py

# -*- coding: utf-8 -*-
# api.py
# Copyright (C) 2013, 2014 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/>.
"""
Soledad - Synchronization Of Locally Encrypted Data Among Devices.

This module holds the public api for Soledad.

Soledad is the part of LEAP that manages storage and synchronization of
application data. It is built on top of U1DB reference Python API and
implements (1) a SQLCipher backend for local storage in the client, (2) a
SyncTarget that encrypts data before syncing, and (3) a CouchDB backend for
remote storage in the server side.
"""
import binascii
import errno
import httplib
import logging
import os
import socket
import ssl
import urlparse

try:
    import cchardet as chardet
except ImportError:
    import chardet
from itertools import chain

from StringIO import StringIO
from u1db.remote import http_client
from u1db.remote.ssl_match_hostname import match_hostname
from twisted.plugin import getPlugins
from zope.interface import implements

from leap.common.config import get_path_prefix
from leap.common.plugins import collect_plugins

from leap.soledad.common import SHARED_DB_NAME
from leap.soledad.common import soledad_assert
from leap.soledad.common import soledad_assert_type

from leap.soledad.client import adbapi
from leap.soledad.client import events as soledad_events
from leap.soledad.client import interfaces as soledad_interfaces
from leap.soledad.client.crypto import SoledadCrypto
from leap.soledad.client.secrets import SoledadSecrets
from leap.soledad.client.shared_db import SoledadSharedDatabase
from leap.soledad.client.sqlcipher import SQLCipherOptions, SQLCipherU1DBSync

logger = logging.getLogger(name=__name__)

#
# Constants
#

"""
Path to the certificate file used to certify the SSL connection between
Soledad client and server.
"""
SOLEDAD_CERT = None


class Soledad(object):
    """
    Soledad provides encrypted data storage and sync.

    A Soledad instance is used to store and retrieve data in a local encrypted
    database and synchronize this database with Soledad server.

    This class is also responsible for bootstrapping users' account by
    creating cryptographic secrets and/or storing/fetching them on Soledad
    server.

    Soledad uses ``leap.common.events`` to signal events. The possible events
    to be signaled are:

        SOLEDAD_CREATING_KEYS: emitted during bootstrap sequence when key
            generation starts.
        SOLEDAD_DONE_CREATING_KEYS: emitted during bootstrap sequence when key
            generation finishes.
        SOLEDAD_UPLOADING_KEYS: emitted during bootstrap sequence when soledad
            starts sending keys to server.
        SOLEDAD_DONE_UPLOADING_KEYS: emitted during bootstrap sequence when
            soledad finishes sending keys to server.
        SOLEDAD_DOWNLOADING_KEYS: emitted during bootstrap sequence when
            soledad starts to retrieve keys from server.
        SOLEDAD_DONE_DOWNLOADING_KEYS: emitted during bootstrap sequence when
            soledad finishes downloading keys from server.
        SOLEDAD_NEW_DATA_TO_SYNC: emitted upon call to C{need_sync()} when
          there's indeed new data to be synchronized between local database
          replica and server's replica.
        SOLEDAD_DONE_DATA_SYNC: emitted inside C{sync()} method when it has
            finished synchronizing with remote replica.
    """
    implements(soledad_interfaces.ILocalStorage,
               soledad_interfaces.ISyncableStorage,
               soledad_interfaces.ISecretsStorage)

    local_db_file_name = 'soledad.u1db'
    secrets_file_name = "soledad.json"
    default_prefix = os.path.join(get_path_prefix(), 'leap', 'soledad')

    def __init__(self, uuid, passphrase, secrets_path, local_db_path,
                 server_url, cert_file, shared_db=None,
                 auth_token=None, defer_encryption=False, syncable=True):
        """
        Initialize configuration, cryptographic keys and dbs.

        :param uuid: User's uuid.
        :type uuid: str

        :param passphrase:
            The passphrase for locking and unlocking encryption secrets for
            local and remote storage.
        :type passphrase: unicode

        :param secrets_path:
            Path for storing encrypted key used for symmetric encryption.
        :type secrets_path: str

        :param local_db_path: Path for local encrypted storage db.
        :type local_db_path: str

        :param server_url:
            URL for Soledad server. This is used either to sync with the user's
            remote db and to interact with the shared recovery database.
        :type server_url: str

        :param cert_file:
            Path to the certificate of the ca used to validate the SSL
            certificate used by the remote soledad server.
        :type cert_file: str

        :param shared_db:
            The shared database.
        :type shared_db: HTTPDatabase

        :param auth_token:
            Authorization token for accessing remote databases.
        :type auth_token: str

        :param defer_encryption:
            Whether to defer encryption/decryption of documents, or do it
            inline while syncing.
        :type defer_encryption: bool

        :param syncable:
            If set to ``False``, this database will not attempt to synchronize
            with remote replicas (default is ``True``)
        :type syncable: bool

        :raise BootstrapSequenceError:
            Raised when the secret initialization sequence (i.e. retrieval
            from server or generation and storage on server) has failed for
            some reason.
        """
        # store config params
        self._uuid = uuid
        self._passphrase = passphrase
        self._local_db_path = local_db_path
        self._server_url = server_url
        self._defer_encryption = defer_encryption
        self._secrets_path = None

        self.shared_db = shared_db

        # configure SSL certificate
        global SOLEDAD_CERT
        SOLEDAD_CERT = cert_file

        # init crypto variables
        self._set_token(auth_token)
        self._crypto = SoledadCrypto(self)

        self._init_config_with_defaults()
        self._init_working_dirs()

        self._secrets_path = secrets_path

        # Initialize shared recovery database
        self.init_shared_db(server_url, uuid, self._creds, syncable=syncable)

        # The following can raise BootstrapSequenceError, that will be
        # propagated upwards.
        self._init_secrets()
        self._init_u1db_sqlcipher_backend()

        if syncable:
            self._init_u1db_syncer()

    #
    # initialization/destruction methods
    #
    def _init_config_with_defaults(self):
        """
        Initialize configuration using default values for missing params.
        """
        soledad_assert_type(self._passphrase, unicode)
        initialize = lambda attr, val: getattr(
            self, attr, None) is None and setattr(self, attr, val)

        initialize("_secrets_path", os.path.join(
            self.default_prefix, self.secrets_file_name))
        initialize("_local_db_path", os.path.join(
            self.default_prefix, self.local_db_file_name))
        # initialize server_url
        soledad_assert(self._server_url is not None,
                       'Missing URL for Soledad server.')

    def _init_working_dirs(self):
        """
        Create work directories.

        :raise OSError: in case file exists and is not a dir.
        """
        paths = map(lambda x: os.path.dirname(x), [
            self._local_db_path, self._secrets_path])
        for path in paths:
            create_path_if_not_exists(path)

    def _init_secrets(self):
        """
        Initialize Soledad secrets.
        """
        self._secrets = SoledadSecrets(
            self.uuid, self._passphrase, self._secrets_path,
            self.shared_db, self._crypto)
        self._secrets.bootstrap()

    def _init_u1db_sqlcipher_backend(self):
        """
        Initialize the U1DB SQLCipher database for local storage.

        Instantiates a modified twisted adbapi that will maintain a threadpool
        with a u1db-sqclipher connection for each thread, and will return
        deferreds for each u1db query.

        Currently, Soledad uses the default SQLCipher cipher, i.e.
        'aes-256-cbc'. We use scrypt to derive a 256-bit encryption key,
        and internally the SQLCipherDatabase initialization uses the 'raw
        PRAGMA key' format to handle the key to SQLCipher.
        """
        tohex = binascii.b2a_hex
        # sqlcipher only accepts the hex version
        key = tohex(self._secrets.get_local_storage_key())
        sync_db_key = tohex(self._secrets.get_sync_db_key())

        opts = SQLCipherOptions(
            self._local_db_path, key,
            is_raw_key=True, create=True,
            defer_encryption=self._defer_encryption,
            sync_db_key=sync_db_key,
        )
        self._sqlcipher_opts = opts
        self._dbpool = adbapi.getConnectionPool(opts)

    def _init_u1db_syncer(self):
        """
        Initialize the U1DB synchronizer.
        """
        replica_uid = self._dbpool.replica_uid
        self._dbsyncer = SQLCipherU1DBSync(
            self._sqlcipher_opts, self._crypto, replica_uid,
            SOLEDAD_CERT,
            defer_encryption=self._defer_encryption)

    #
    # Closing methods
    #

    def close(self):
        """
        Close underlying U1DB database.
        """
        logger.debug("Closing soledad")
        self._dbpool.close()
        if getattr(self, '_dbsyncer', None):
            self._dbsyncer.close()

    #
    # ILocalStorage
    #

    def _defer(self, meth, *args, **kw):
        """
        Defer a method to be run on a U1DB connection pool.

        :param meth: A method to defer to the U1DB connection pool.
        :type meth: callable
        :return: A deferred.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._dbpool.runU1DBQuery(meth, *args, **kw)

    def put_doc(self, doc):
        """
        Update a document.

        If the document currently has conflicts, put will fail.
        If the database specifies a maximum document size and the document
        exceeds it, put will fail and raise a DocumentTooBig exception.

        ============================== WARNING ==============================
        This method converts the document's contents to unicode in-place. This
        means that after calling `put_doc(doc)`, the contents of the
        document, i.e. `doc.content`, might be different from before the
        call.
        ============================== WARNING ==============================

        :param doc: A document with new content.
        :type doc: leap.soledad.common.document.SoledadDocument
        :return: A deferred whose callback will be invoked with the new
            revision identifier for the document. The document object will
            also be updated.
        :rtype: twisted.internet.defer.Deferred
        """
        doc.content = _convert_to_unicode(doc.content)
        return self._defer("put_doc", doc)

    def delete_doc(self, doc):
        """
        Mark a document as deleted.

        Will abort if the current revision doesn't match doc.rev.
        This will also set doc.content to None.

        :param doc: A document to be deleted.
        :type doc: leap.soledad.common.document.SoledadDocument
        :return: A deferred.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("delete_doc", doc)

    def get_doc(self, doc_id, include_deleted=False):
        """
        Get the JSON string for the given document.

        :param doc_id: The unique document identifier
        :type doc_id: str
        :param include_deleted: If set to True, deleted documents will be
            returned with empty content. Otherwise asking for a deleted
            document will return None.
        :type include_deleted: bool
        :return: A deferred whose callback will be invoked with a document
            object.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer(
            "get_doc", doc_id, include_deleted=include_deleted)

    def get_docs(
            self, doc_ids, check_for_conflicts=True, include_deleted=False):
        """
        Get the JSON content for many documents.

        :param doc_ids: A list of document identifiers.
        :type doc_ids: list
        :param check_for_conflicts: If set to False, then the conflict check
            will be skipped, and 'None' will be returned instead of True/False.
        :type check_for_conflicts: bool
        :param include_deleted: If set to True, deleted documents will be
            returned with empty content. Otherwise deleted documents will not
            be included in the results.
        :type include_deleted: bool
        :return: A deferred whose callback will be invoked with an iterable
            giving the document object for each document id in matching
            doc_ids order.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer(
            "get_docs", doc_ids, check_for_conflicts=check_for_conflicts,
            include_deleted=include_deleted)

    def get_all_docs(self, include_deleted=False):
        """
        Get the JSON content for all documents in the database.

        :param include_deleted: If set to True, deleted documents will be
            returned with empty content. Otherwise deleted documents will not
            be included in the results.
        :type include_deleted: bool

        :return: A deferred which, when fired, will pass the a tuple
            containing (generation, [Document]) to the callback, with the
            current generation of the database, followed by a list of all the
            documents in the database.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("get_all_docs", include_deleted)

    def create_doc(self, content, doc_id=None):
        """
        Create a new document.

        You can optionally specify the document identifier, but the document
        must not already exist. See 'put_doc' if you want to override an
        existing document.
        If the database specifies a maximum document size and the document
        exceeds it, create will fail and raise a DocumentTooBig exception.

        :param content: A Python dictionary.
        :type content: dict
        :param doc_id: An optional identifier specifying the document id.
        :type doc_id: str
        :return: A deferred whose callback will be invoked with a document.
        :rtype: twisted.internet.defer.Deferred
        """
        # TODO we probably should pass an optional "encoding" parameter to
        # create_doc (and probably to put_doc too). There are cases (mail
        # payloads for example) in which we already have the encoding in the
        # headers, so we don't need to guess it.
        return self._defer(
            "create_doc", _convert_to_unicode(content), doc_id=doc_id)

    def create_doc_from_json(self, json, doc_id=None):
        """
        Create a new document.

        You can optionally specify the document identifier, but the document
        must not already exist. See 'put_doc' if you want to override an
        existing document.
        If the database specifies a maximum document size and the document
        exceeds it, create will fail and raise a DocumentTooBig exception.

        :param json: The JSON document string
        :type json: dict
        :param doc_id: An optional identifier specifying the document id.
        :type doc_id: str
        :return: A deferred whose callback will be invoked with a document.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("create_doc_from_json", json, doc_id=doc_id)

    def create_index(self, index_name, *index_expressions):
        """
        Create a named index, which can then be queried for future lookups.

        Creating an index which already exists is not an error, and is cheap.
        Creating an index which does not match the index_expressions of the
        existing index is an error.
        Creating an index will block until the expressions have been evaluated
        and the index generated.

        :param index_name: A unique name which can be used as a key prefix
        :type index_name: str
        :param index_expressions: index expressions defining the index
            information.

            Examples:

            "fieldname", or "fieldname.subfieldname" to index alphabetically
            sorted on the contents of a field.

            "number(fieldname, width)", "lower(fieldname)"
        :type index_expresions: list of str
        :return: A deferred.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("create_index", index_name, *index_expressions)

    def delete_index(self, index_name):
        """
        Remove a named index.

        :param index_name: The name of the index we are removing
        :type index_name: str
        :return: A deferred.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("delete_index", index_name)

    def list_indexes(self):
        """
        List the definitions of all known indexes.

        :return: A deferred whose callback will be invoked with a list of
            [('index-name', ['field', 'field2'])] definitions.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("list_indexes")

    def get_from_index(self, index_name, *key_values):
        """
        Return documents that match the keys supplied.

        You must supply exactly the same number of values as have been defined
        in the index. It is possible to do a prefix match by using '*' to
        indicate a wildcard match. You can only supply '*' to trailing entries,
        (eg 'val', '*', '*' is allowed, but '*', 'val', 'val' is not.)
        It is also possible to append a '*' to the last supplied value (eg
        'val*', '*', '*' or 'val', 'val*', '*', but not 'val*', 'val', '*')

        :param index_name: The index to query
        :type index_name: str
        :param key_values: values to match. eg, if you have
            an index with 3 fields then you would have:
            get_from_index(index_name, val1, val2, val3)
        :type key_values: list
        :return: A deferred whose callback will be invoked with a list of
            [Document].
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("get_from_index", index_name, *key_values)

    def get_count_from_index(self, index_name, *key_values):
        """
        Return the count for a given combination of index_name
        and key values.

        Extension method made from similar methods in u1db version 13.09

        :param index_name: The index to query
        :type index_name: str
        :param key_values: values to match. eg, if you have
                           an index with 3 fields then you would have:
                           get_from_index(index_name, val1, val2, val3)
        :type key_values: tuple
        :return: A deferred whose callback will be invoked with the count.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("get_count_from_index", index_name, *key_values)

    def get_range_from_index(self, index_name, start_value, end_value):
        """
        Return documents that fall within the specified range.

        Both ends of the range are inclusive. For both start_value and
        end_value, one must supply exactly the same number of values as have
        been defined in the index, or pass None. In case of a single column
        index, a string is accepted as an alternative for a tuple with a single
        value. It is possible to do a prefix match by using '*' to indicate
        a wildcard match. You can only supply '*' to trailing entries, (eg
        'val', '*', '*' is allowed, but '*', 'val', 'val' is not.) It is also
        possible to append a '*' to the last supplied value (eg 'val*', '*',
        '*' or 'val', 'val*', '*', but not 'val*', 'val', '*')

        :param index_name: The index to query
        :type index_name: str
        :param start_values: tuples of values that define the lower bound of
            the range. eg, if you have an index with 3 fields then you would
            have: (val1, val2, val3)
        :type start_values: tuple
        :param end_values: tuples of values that define the upper bound of the
            range. eg, if you have an index with 3 fields then you would have:
            (val1, val2, val3)
        :type end_values: tuple
        :return: A deferred whose callback will be invoked with a list of
            [Document].
        :rtype: twisted.internet.defer.Deferred
        """

        return self._defer(
            "get_range_from_index", index_name, start_value, end_value)

    def get_index_keys(self, index_name):
        """
        Return all keys under which documents are indexed in this index.

        :param index_name: The index to query
        :type index_name: str
        :return: A deferred whose callback will be invoked with a list of
            tuples of indexed keys.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("get_index_keys", index_name)

    def get_doc_conflicts(self, doc_id):
        """
        Get the list of conflicts for the given document.

        The order of the conflicts is such that the first entry is the value
        that would be returned by "get_doc".

        :param doc_id: The unique document identifier
        :type doc_id: str
        :return: A deferred whose callback will be invoked with a list of the
            Document entries that are conflicted.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("get_doc_conflicts", doc_id)

    def resolve_doc(self, doc, conflicted_doc_revs):
        """
        Mark a document as no longer conflicted.

        We take the list of revisions that the client knows about that it is
        superseding. This may be a different list from the actual current
        conflicts, in which case only those are removed as conflicted.  This
        may fail if the conflict list is significantly different from the
        supplied information. (sync could have happened in the background from
        the time you GET_DOC_CONFLICTS until the point where you RESOLVE)

        :param doc: A Document with the new content to be inserted.
        :type doc: SoledadDocument
        :param conflicted_doc_revs: A list of revisions that the new content
            supersedes.
        :type conflicted_doc_revs: list(str)
        :return: A deferred.
        :rtype: twisted.internet.defer.Deferred
        """
        return self._defer("resolve_doc", doc, conflicted_doc_revs)

    @property
    def local_db_path(self):
        return self._local_db_path

    @property
    def uuid(self):
        return self._uuid

    #
    # ISyncableStorage
    #

    def sync(self, defer_decryption=True):
        """
        Synchronize documents with the server replica.

        :param defer_decryption:
            Whether to defer decryption of documents, or do it inline while
            syncing.
        :type defer_decryption: bool

        :return: A deferred whose callback will be invoked with the local
            generation before the synchronization was performed.
        :rtype: twisted.internet.defer.Deferred
        """

        # -----------------------------------------------------------------
        # TODO this needs work.
        # Should review/write tests to check that this:

        # (1) Defer to the syncer pool -- DONE (on dbsyncer)
        # (2) Return the deferred
        # (3) Add the callback for signaling the event (executed on reactor
        #     thread)
        # (4) Check that the deferred is called with the local gen.

        # -----------------------------------------------------------------

        sync_url = urlparse.urljoin(self._server_url, 'user-%s' % self.uuid)
        d = self._dbsyncer.sync(
            sync_url,
            creds=self._creds,
            defer_decryption=defer_decryption)

        def _sync_callback(local_gen):
            self._last_received_docs = docs = self._dbsyncer.received_docs

            # Post-Sync Hooks
            if docs:
                iface = soledad_interfaces.ISoledadPostSyncPlugin
                suitable_plugins = collect_plugins(iface)
                for plugin in suitable_plugins:
                    watched = plugin.watched_doc_types
                    r = [filter(
                        lambda s: s.startswith(preffix),
                        docs) for preffix in watched]
                    filtered = list(chain(*r))
                    plugin.process_received_docs(filtered)

            soledad_events.emit(
                soledad_events.SOLEDAD_DONE_DATA_SYNC, self.uuid)
            return local_gen

        def _sync_errback(failure):
            s = StringIO()
            failure.printDetailedTraceback(file=s)
            msg = "Soledad exception when syncing!\n" + s.getvalue()
            logger.error(msg)
            return failure

        d.addCallbacks(_sync_callback, _sync_errback)
        return d

    @property
    def syncing(self):
        """
        Return wether Soledad is currently synchronizing with the server.

        :return: Wether Soledad is currently synchronizing with the server.
        :rtype: bool
        """
        return self._dbsyncer.syncing

    def _set_token(self, token):
        """
        Set the authentication token for remote database access.

        Internally, this builds the credentials dictionary with the following
        format:

            {
                'token': {
                    'uuid': '<uuid>'
                    'token': '<token>'
                }
            }

        :param token: The authentication token.
        :type token: str
        """
        self._creds = {
            'token': {
                'uuid': self.uuid,
                'token': token,
            }
        }

    def _get_token(self):
        """
        Return current token from credentials dictionary.
        """
        return self._creds['token']['token']

    token = property(_get_token, _set_token, doc='The authentication Token.')

    #
    # ISecretsStorage
    #

    def init_shared_db(self, server_url, uuid, creds, syncable=True):
        """
        Initialize the shared database.

        :param server_url: URL of the remote database.
        :type server_url: str
        :param uuid: The user's unique id.
        :type uuid: str
        :param creds: A tuple containing the authentication method and
            credentials.
        :type creds: tuple
        :param syncable:
            If syncable is False, the database will not attempt to sync against
            a remote replica.
        :type syncable: bool
        """
        # only case this is False is for testing purposes
        if self.shared_db is None:
            shared_db_url = urlparse.urljoin(server_url, SHARED_DB_NAME)
            self.shared_db = SoledadSharedDatabase.open_database(
                shared_db_url,
                uuid,
                creds=creds,
                syncable=syncable)

    @property
    def storage_secret(self):
        """
        Return the secret used for local storage encryption.

        :return: The secret used for local storage encryption.
        :rtype: str
        """
        return self._secrets.storage_secret

    @property
    def remote_storage_secret(self):
        """
        Return the secret used for encryption of remotely stored data.

        :return: The secret used for remote storage  encryption.
        :rtype: str
        """
        return self._secrets.remote_storage_secret

    @property
    def secrets(self):
        """
        Return the secrets object.

        :return: The secrets object.
        :rtype: SoledadSecrets
        """
        return self._secrets

    def change_passphrase(self, new_passphrase):
        """
        Change the passphrase that encrypts the storage secret.

        :param new_passphrase: The new passphrase.
        :type new_passphrase: unicode

        :raise NoStorageSecret: Raised if there's no storage secret available.
        """
        self._secrets.change_passphrase(new_passphrase)

    #
    # Raw SQLCIPHER Queries
    #

    def raw_sqlcipher_query(self, *args, **kw):
        """
        Run a raw sqlcipher query in the local database, and return a deferred
        that will be fired with the result.
        """
        return self._dbpool.runQuery(*args, **kw)

    def raw_sqlcipher_operation(self, *args, **kw):
        """
        Run a raw sqlcipher operation in the local database, and return a
        deferred that will be fired with None.
        """
        return self._dbpool.runOperation(*args, **kw)


def _convert_to_unicode(content):
    """
    Convert content to unicode (or all the strings in content).

    NOTE: Even though this method supports any type, it will
    currently ignore contents of lists, tuple or any other
    iterable than dict. We don't need support for these at the
    moment

    :param content: content to convert
    :type content: object

    :rtype: object
    """
    # Chardet doesn't guess very well with some smallish payloads.
    # This parameter might need some empirical tweaking.
    CUTOFF_CONFIDENCE = 0.90

    if isinstance(content, unicode):
        return content
    elif isinstance(content, str):
        encoding = "utf-8"
        result = chardet.detect(content)
        if result["confidence"] > CUTOFF_CONFIDENCE:
            encoding = result["encoding"]
        try:
            content = content.decode(encoding)
        except UnicodeError as e:
            logger.error("Unicode error: {0!r}. Using 'replace'".format(e))
            content = content.decode(encoding, 'replace')
        return content
    else:
        if isinstance(content, dict):
            for key in content.keys():
                content[key] = _convert_to_unicode(content[key])
    return content


def create_path_if_not_exists(path):
    try:
        if not os.path.isdir(path):
            logger.info('Creating directory: %s.' % path)
        os.makedirs(path)
    except OSError as exc:
        if exc.errno == errno.EEXIST and os.path.isdir(path):
            pass
        else:
            raise

# ----------------------------------------------------------------------------
# Monkey patching u1db to be able to provide a custom SSL cert
# ----------------------------------------------------------------------------

# We need a more reasonable timeout (in seconds)
SOLEDAD_TIMEOUT = 120


class VerifiedHTTPSConnection(httplib.HTTPSConnection):
    """
    HTTPSConnection verifying server side certificates.
    """
    # derived from httplib.py

    def connect(self):
        """
        Connect to a host on a given (SSL) port.
        """
        try:
            source = self.source_address
            sock = socket.create_connection((self.host, self.port),
                                            SOLEDAD_TIMEOUT, source)
        except AttributeError:
            # source_address was introduced in 2.7
            sock = socket.create_connection((self.host, self.port),
                                            SOLEDAD_TIMEOUT)
        if self._tunnel_host:
            self.sock = sock
            self._tunnel()

        self.sock = ssl.wrap_socket(sock,
                                    ca_certs=SOLEDAD_CERT,
                                    cert_reqs=ssl.CERT_REQUIRED)
        match_hostname(self.sock.getpeercert(), self.host)


old__VerifiedHTTPSConnection = http_client._VerifiedHTTPSConnection
http_client._VerifiedHTTPSConnection = VerifiedHTTPSConnection