Merge remote-tracking branch 'origin/develop' into debian

Conflicts:
	client/src/leap/__init__.py
	client/src/leap/soledad/client/__init__.py
	client/src/leap/soledad/client/auth.py
	client/src/leap/soledad/client/crypto.py
	client/src/leap/soledad/client/shared_db.py
	client/src/leap/soledad/client/sqlcipher.py
	client/src/leap/soledad/client/target.py
	common/src/leap/soledad/common/couch.py
	common/src/leap/soledad/common/crypto.py
	common/src/leap/soledad/common/objectstore.py
	common/src/leap/soledad/common/tests/__init__.py
	common/src/leap/soledad/common/tests/couchdb.ini.template
	common/src/leap/soledad/common/tests/test_couch.py
	common/src/leap/soledad/common/tests/test_server.py
	common/src/leap/soledad/common/tests/test_soledad.py
	common/src/leap/soledad/common/tests/test_sqlcipher.py
	common/src/leap/soledad/common/tests/test_target.py
	common/src/leap/soledad/common/tests/u1db_tests/README
	common/src/leap/soledad/common/tests/u1db_tests/__init__.py
	common/src/leap/soledad/common/tests/u1db_tests/test_backends.py
	common/src/leap/soledad/common/tests/u1db_tests/test_document.py
	common/src/leap/soledad/common/tests/u1db_tests/test_http_app.py
	common/src/leap/soledad/common/tests/u1db_tests/test_http_client.py
	common/src/leap/soledad/common/tests/u1db_tests/test_http_database.py
	common/src/leap/soledad/common/tests/u1db_tests/test_https.py
	common/src/leap/soledad/common/tests/u1db_tests/test_open.py
	common/src/leap/soledad/common/tests/u1db_tests/test_remote_sync_target.py
	common/src/leap/soledad/common/tests/u1db_tests/test_sqlite_backend.py
	common/src/leap/soledad/common/tests/u1db_tests/test_sync.py
	common/src/leap/soledad/common/tests/u1db_tests/testing-certs/Makefile
	common/src/leap/soledad/common/tests/u1db_tests/testing-certs/cacert.pem
	common/src/leap/soledad/common/tests/u1db_tests/testing-certs/testing.cert
	common/src/leap/soledad/common/tests/u1db_tests/testing-certs/testing.key
	pkg/soledad
	server/pkg/soledad
	server/setup.py
	server/src/leap/soledad/server/auth.py
	setup.py
	soledad/setup.py
	soledad/src/leap/__init__.py
	soledad/src/leap/soledad/__init__.py
	soledad/src/leap/soledad/auth.py
	soledad/src/leap/soledad/crypto.py
	soledad/src/leap/soledad/shared_db.py
	soledad/src/leap/soledad/sqlcipher.py
	soledad/src/leap/soledad/target.py
	soledad/src/leap/soledad/tests/__init__.py
	soledad/src/leap/soledad/tests/couchdb.ini.template
	soledad/src/leap/soledad/tests/test_couch.py
	soledad/src/leap/soledad/tests/test_crypto.py
	soledad/src/leap/soledad/tests/test_server.py
	soledad/src/leap/soledad/tests/test_soledad.py
	soledad/src/leap/soledad/tests/test_sqlcipher.py
	soledad/src/leap/soledad/tests/test_target.py
	soledad/src/leap/soledad/tests/u1db_tests/README
	soledad/src/leap/soledad/tests/u1db_tests/__init__.py
	soledad/src/leap/soledad/tests/u1db_tests/test_backends.py
	soledad/src/leap/soledad/tests/u1db_tests/test_document.py
	soledad/src/leap/soledad/tests/u1db_tests/test_http_app.py
	soledad/src/leap/soledad/tests/u1db_tests/test_http_client.py
	soledad/src/leap/soledad/tests/u1db_tests/test_http_database.py
	soledad/src/leap/soledad/tests/u1db_tests/test_https.py
	soledad/src/leap/soledad/tests/u1db_tests/test_open.py
	soledad/src/leap/soledad/tests/u1db_tests/test_remote_sync_target.py
	soledad/src/leap/soledad/tests/u1db_tests/test_sqlite_backend.py
	soledad/src/leap/soledad/tests/u1db_tests/test_sync.py
	soledad/src/leap/soledad/tests/u1db_tests/testing-certs/Makefile
	soledad/src/leap/soledad/tests/u1db_tests/testing-certs/cacert.pem
	soledad/src/leap/soledad/tests/u1db_tests/testing-certs/testing.cert
	soledad/src/leap/soledad/tests/u1db_tests/testing-certs/testing.key
	soledad_server/pkg/soledad
	soledad_server/src/leap/soledad_server/auth.py
	soledad_server/src/leap/soledad_server/couch.py
	soledad_server/src/leap/soledad_server/objectstore.py
	src/leap/__init__.py
	src/leap/soledad/__init__.py
	src/leap/soledad/auth.py
	src/leap/soledad/backends/couch.py
	src/leap/soledad/backends/leap_backend.py
	src/leap/soledad/backends/objectstore.py
	src/leap/soledad/backends/sqlcipher.py
	src/leap/soledad/crypto.py
	src/leap/soledad/server.py
	src/leap/soledad/shared_db.py
	src/leap/soledad/tests/__init__.py
	src/leap/soledad/tests/couchdb.ini.template
	src/leap/soledad/tests/test_couch.py
	src/leap/soledad/tests/test_leap_backend.py
	src/leap/soledad/tests/test_server.py
	src/leap/soledad/tests/test_soledad.py
	src/leap/soledad/tests/test_sqlcipher.py
	src/leap/soledad/tests/u1db_tests/README
	src/leap/soledad/tests/u1db_tests/__init__.py
	src/leap/soledad/tests/u1db_tests/test_backends.py
	src/leap/soledad/tests/u1db_tests/test_document.py
	src/leap/soledad/tests/u1db_tests/test_http_app.py
	src/leap/soledad/tests/u1db_tests/test_http_client.py
	src/leap/soledad/tests/u1db_tests/test_http_database.py
	src/leap/soledad/tests/u1db_tests/test_https.py
	src/leap/soledad/tests/u1db_tests/test_open.py
	src/leap/soledad/tests/u1db_tests/test_remote_sync_target.py
	src/leap/soledad/tests/u1db_tests/test_sqlite_backend.py
	src/leap/soledad/tests/u1db_tests/test_sync.py
	src/leap/soledad/tests/u1db_tests/testing-certs/Makefile
	src/leap/soledad/tests/u1db_tests/testing-certs/cacert.pem
	src/leap/soledad/tests/u1db_tests/testing-certs/testing.cert
	src/leap/soledad/tests/u1db_tests/testing-certs/testing.key

4 files changed, 568 insertions, 0 deletions

diff --git a/server/src/leap/__init__.py b/server/src/leap/__init__.py
new file mode 100644
index 00000000..f48ad105
--- /dev/null
+++ b/server/src/leap/__init__.py
@@ -0,0 +1,6 @@
+# See http://peak.telecommunity.com/DevCenter/setuptools#namespace-packages
+try:
+    __import__('pkg_resources').declare_namespace(__name__)
+except ImportError:
+    from pkgutil import extend_path
+    __path__ = extend_path(__path__, __name__)
diff --git a/server/src/leap/soledad/__init__.py b/server/src/leap/soledad/__init__.py
new file mode 100644
index 00000000..f48ad105
--- /dev/null
+++ b/server/src/leap/soledad/__init__.py
@@ -0,0 +1,6 @@
+# See http://peak.telecommunity.com/DevCenter/setuptools#namespace-packages
+try:
+    __import__('pkg_resources').declare_namespace(__name__)
+except ImportError:
+    from pkgutil import extend_path
+    __path__ = extend_path(__path__, __name__)
diff --git a/server/src/leap/soledad/server/__init__.py b/server/src/leap/soledad/server/__init__.py
new file mode 100644
index 00000000..4ed8efc9
--- /dev/null
+++ b/server/src/leap/soledad/server/__init__.py
@@ -0,0 +1,125 @@
+# -*- coding: utf-8 -*-
+# server.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/>.
+
+
+"""
+A U1DB server that stores data using CouchDB as its persistence layer.
+
+This should be run with:
+    twistd -n web --wsgi=leap.soledad_server.application --port=2424
+"""
+
+import configparser
+
+from u1db.remote import http_app
+
+
+# Keep OpenSSL's tsafe before importing Twisted submodules so we can put
+# it back if Twisted==12.0.0 messes with it.
+from OpenSSL import tsafe
+old_tsafe = tsafe
+
+from twisted.web.wsgi import WSGIResource
+from twisted.internet import reactor
+from twisted import version
+if version.base() == "12.0.0":
+    # Put OpenSSL's tsafe back into place. This can probably be removed if we
+    # come to use Twisted>=12.3.0.
+    import sys
+    sys.modules['OpenSSL.tsafe'] = old_tsafe
+
+
+from leap.soledad.server.auth import SoledadTokenAuthMiddleware
+from leap.soledad.common.couch import CouchServerState
+
+
+#-----------------------------------------------------------------------------
+# Soledad WSGI application
+#-----------------------------------------------------------------------------
+
+class SoledadApp(http_app.HTTPApp):
+    """
+    Soledad WSGI application
+    """
+
+    SHARED_DB_NAME = 'shared'
+    """
+    The name of the shared database that holds user's encrypted secrets.
+    """
+
+    USER_DB_PREFIX = 'user-'
+    """
+    The string prefix of users' databases.
+    """
+
+    def __call__(self, environ, start_response):
+        """
+        Handle a WSGI call to the Soledad application.
+
+        @param environ: Dictionary containing CGI variables.
+        @type environ: dict
+        @param start_response: Callable of the form start_response(status,
+            response_headers, exc_info=None).
+        @type start_response: callable
+
+        @return: HTTP application results.
+        @rtype: list
+        """
+        # ensure the shared database exists
+        self.state.ensure_database(self.SHARED_DB_NAME)
+        return http_app.HTTPApp.__call__(self, environ, start_response)
+
+
+#-----------------------------------------------------------------------------
+# Auxiliary functions
+#-----------------------------------------------------------------------------
+
+def load_configuration(file_path):
+    """
+    Load server configuration from file.
+
+    @param file_path: The path to the configuration file.
+    @type file_path: str
+
+    @return: A dictionary with the configuration.
+    @rtype: dict
+    """
+    conf = {
+        'couch_url': 'http://localhost:5984',
+    }
+    config = configparser.ConfigParser()
+    config.read(file_path)
+    if 'soledad-server' in config:
+        for key in conf:
+            if key in config['soledad-server']:
+                conf[key] = config['soledad-server'][key]
+    # TODO: implement basic parsing/sanitization of options comming from
+    # config file.
+    return conf
+
+
+#-----------------------------------------------------------------------------
+# Run as Twisted WSGI Resource
+#-----------------------------------------------------------------------------
+
+conf = load_configuration('/etc/leap/soledad-server.conf')
+state = CouchServerState(conf['couch_url'])
+
+# WSGI application that may be used by `twistd -web`
+application = SoledadTokenAuthMiddleware(SoledadApp(state))
+
+resource = WSGIResource(reactor, reactor.getThreadPool(), application)
diff --git a/server/src/leap/soledad/server/auth.py b/server/src/leap/soledad/server/auth.py
new file mode 100644
index 00000000..3bcfcf04
--- /dev/null
+++ b/server/src/leap/soledad/server/auth.py
@@ -0,0 +1,431 @@
+# -*- coding: utf-8 -*-
+# auth.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/>.
+
+
+"""
+Authentication facilities for Soledad Server.
+"""
+
+
+import httplib
+import simplejson as json
+
+
+from u1db import DBNAME_CONSTRAINTS
+from abc import ABCMeta, abstractmethod
+from routes.mapper import Mapper
+from couchdb.client import Server
+from twisted.python import log
+
+
+#-----------------------------------------------------------------------------
+# Authentication
+#-----------------------------------------------------------------------------
+
+class Unauthorized(Exception):
+    """
+    User authentication failed.
+    """
+
+
+class URLToAuthorization(object):
+    """
+    Verify if actions can be performed by a user.
+    """
+
+    HTTP_METHOD_GET = 'GET'
+    HTTP_METHOD_PUT = 'PUT'
+    HTTP_METHOD_DELETE = 'DELETE'
+    HTTP_METHOD_POST = 'POST'
+
+    def __init__(self, uuid, shared_db_name, user_db_prefix):
+        """
+        Initialize the mapper.
+
+        The C{uuid} is used to create the rules that will either allow or
+        disallow the user to perform specific actions.
+
+        @param uuid: The user uuid.
+        @type uuid: str
+        @param shared_db_name: The name of the shared database that holds
+            user's encrypted secrets.
+        @type shared_db_name: str
+        @param user_db_prefix: The string prefix of users' databases.
+        @type user_db_prefix: str
+        """
+        self._map = Mapper(controller_scan=None)
+        self._user_db_prefix = user_db_prefix
+        self._shared_db_name = shared_db_name
+        self._register_auth_info(self._uuid_dbname(uuid))
+
+    def is_authorized(self, environ):
+        """
+        Return whether an HTTP request that produced the CGI C{environ}
+        corresponds to an authorized action.
+
+        @param environ: Dictionary containing CGI variables.
+        @type environ: dict
+
+        @return: Whether the action is authorized or not.
+        @rtype: bool
+        """
+        return self._map.match(environ=environ) is not None
+
+    def _register(self, pattern, http_methods):
+        """
+        Register a C{pattern} in the mapper as valid for C{http_methods}.
+
+        @param pattern: The URL pattern that corresponds to the user action.
+        @type pattern: str
+        @param http_methods: A list of authorized HTTP methods.
+        @type http_methods: list of str
+        """
+        self._map.connect(
+            None, pattern, http_methods=http_methods,
+            conditions=dict(method=http_methods),
+            requirements={'dbname': DBNAME_CONSTRAINTS})
+
+    def _uuid_dbname(self, uuid):
+        """
+        Return the database name corresponding to C{uuid}.
+
+        @param uuid: The user uid.
+        @type uuid: str
+
+        @return: The database name corresponding to C{uuid}.
+        @rtype: str
+        """
+        return '%s%s' % (self._user_db_prefix, uuid)
+
+    def _register_auth_info(self, dbname):
+        """
+        Register the authorization info in the mapper using C{dbname} as the
+        user's database name.
+
+        This method sets up the following authorization rules:
+
+            URL path                      | Authorized actions
+            --------------------------------------------------
+            /                             | GET
+            /shared-db                    | GET
+            /shared-db/docs               | -
+            /shared-db/doc/{id}           | GET, PUT, DELETE
+            /shared-db/sync-from/{source} | -
+            /user-db                      | GET, PUT, DELETE
+            /user-db/docs                 | -
+            /user-db/doc/{id}             | -
+            /user-db/sync-from/{source}   | GET, PUT, POST
+
+        @param dbname: The name of the user's database.
+        @type dbname: str
+        """
+        # auth info for global resource
+        self._register('/', [self.HTTP_METHOD_GET])
+        # auth info for shared-db database resource
+        self._register(
+            '/%s' % self._shared_db_name,
+            [self.HTTP_METHOD_GET])
+        # auth info for shared-db doc resource
+        self._register(
+            '/%s/doc/{id:.*}' % self._shared_db_name,
+            [self.HTTP_METHOD_GET, self.HTTP_METHOD_PUT,
+             self.HTTP_METHOD_DELETE])
+        # auth info for user-db database resource
+        self._register(
+            '/%s' % dbname,
+            [self.HTTP_METHOD_GET, self.HTTP_METHOD_PUT,
+             self.HTTP_METHOD_DELETE])
+        # auth info for user-db sync resource
+        self._register(
+            '/%s/sync-from/{source_replica_uid}' % dbname,
+            [self.HTTP_METHOD_GET, self.HTTP_METHOD_PUT,
+             self.HTTP_METHOD_POST])
+        # generate the regular expressions
+        self._map.create_regs()
+
+
+class SoledadAuthMiddleware(object):
+    """
+    Soledad Authentication WSGI middleware.
+
+    This class must be extended to implement specific authentication methods
+    (see SoledadTokenAuthMiddleware below).
+
+    It expects an HTTP_AUTHORIZATION header containing the the concatenation of
+    the following strings:
+
+        1. The authentication scheme. It will be verified by the
+           _verify_authentication_scheme() method.
+
+        2. A space character.
+
+        3. The base64 encoded string of the concatenation of the user uuid with
+           the authentication data, separated by a collon, like this:
+
+               base64("<uuid>:<auth_data>")
+
+    After authentication check, the class performs an authorization check to
+    verify whether the user is authorized to perform the requested action.
+
+    On client-side, 2 methods must be implemented so the soledad client knows
+    how to send authentication headers to server:
+
+        * set_<method>_credentials: store authentication credentials in the
+          class.
+
+        * _sign_request: format and include custom authentication data in
+          the HTTP_AUTHORIZATION header.
+
+    See leap.soledad.auth and u1db.remote.http_client.HTTPClient to understand
+    how to do it.
+    """
+
+    __metaclass__ = ABCMeta
+
+    HTTP_AUTH_KEY = "HTTP_AUTHORIZATION"
+    PATH_INFO_KEY = "PATH_INFO"
+
+    CONTENT_TYPE_JSON = ('content-type', 'application/json')
+
+    def __init__(self, app):
+        """
+        Initialize the Soledad Authentication Middleware.
+
+        @param app: The application to run on successfull authentication.
+        @type app: u1db.remote.http_app.HTTPApp
+        @param prefix: Auth app path prefix.
+        @type prefix: str
+        """
+        self._app = app
+
+    def _error(self, start_response, status, description, message=None):
+        """
+        Send a JSON serialized error to WSGI client.
+
+        @param start_response: Callable of the form start_response(status,
+            response_headers, exc_info=None).
+        @type start_response: callable
+        @param status: Status string of the form "999 Message here"
+        @type status: str
+        @param response_headers: A list of (header_name, header_value) tuples
+            describing the HTTP response header.
+        @type response_headers: list
+        @param description: The error description.
+        @type description: str
+        @param message: The error message.
+        @type message: str
+
+        @return: List with JSON serialized error message.
+        @rtype list
+        """
+        start_response("%d %s" % (status, httplib.responses[status]),
+                       [self.CONTENT_TYPE_JSON])
+        err = {"error": description}
+        if message:
+            err['message'] = message
+        return [json.dumps(err)]
+
+    def _unauthorized_error(self, start_response, message):
+        """
+        Send a unauth error.
+
+        @param message: The error message.
+        @type message: str
+        @param start_response: Callable of the form start_response(status,
+            response_headers, exc_info=None).
+        @type start_response: callable
+
+        @return: List with JSON serialized error message.
+        @rtype list
+        """
+        return self._error(
+            start_response,
+            401,
+            "unauthorized",
+            message)
+
+    def __call__(self, environ, start_response):
+        """
+        Handle a WSGI call to the authentication application.
+
+        @param environ: Dictionary containing CGI variables.
+        @type environ: dict
+        @param start_response: Callable of the form start_response(status,
+            response_headers, exc_info=None).
+        @type start_response: callable
+
+        @return: Target application results if authentication succeeds, an
+        error message otherwise.
+        @rtype: list
+        """
+        # check for authentication header
+        auth = environ.get(self.HTTP_AUTH_KEY)
+        if not auth:
+            return self._unauthorized_error(
+                start_response, "Missing authentication header.")
+
+        # get authentication data
+        scheme, encoded = auth.split(None, 1)
+        uuid, auth_data = encoded.decode('base64').split(':', 1)
+        if not self._verify_authentication_scheme(scheme):
+            return self._unauthorized_error("Wrong authentication scheme")
+
+        # verify if user is athenticated
+        if not self._verify_authentication_data(uuid, auth_data):
+            return self._unauthorized_error(
+                start_response,
+                self._get_auth_error_string())
+
+        # verify if user is authorized to perform action
+        if not self._verify_authorization(environ, uuid):
+            return self._unauthorized_error(
+                start_response,
+                "Unauthorized action.")
+
+        # move on to the real Soledad app
+        del environ[self.HTTP_AUTH_KEY]
+        return self._app(environ, start_response)
+
+    @abstractmethod
+    def _verify_authentication_scheme(self, scheme):
+        """
+        Verify if authentication scheme is valid.
+
+        @param scheme: Auth scheme extracted from the HTTP_AUTHORIZATION
+            header.
+        @type scheme: str
+
+        @return: Whether the authentitcation scheme is valid.
+        """
+        return None
+
+    @abstractmethod
+    def _verify_authentication_data(self, uuid, auth_data):
+        """
+        Verify valid authenticatiion for this request.
+
+        @param uuid: The user's uuid.
+        @type uuid: str
+        @param auth_data: Authentication data.
+        @type auth_data: str
+
+        @return: Whether the token is valid for authenticating the request.
+        @rtype: bool
+        """
+        return None
+
+    def _verify_authorization(self, environ, uuid):
+        """
+        Verify if the user is authorized to perform the requested action over
+        the requested database.
+
+        @param environ: Dictionary containing CGI variables.
+        @type environ: dict
+        @param uuid: The user's uuid.
+        @type uuid: str
+
+        @return: Whether the user is authorize to perform the requested action
+            over the requested db.
+        @rtype: bool
+        """
+        return URLToAuthorization(
+            uuid, self._app.SHARED_DB_NAME,
+            self._app.USER_DB_PREFIX
+        ).is_authorized(environ)
+
+    @abstractmethod
+    def _get_auth_error_string(self):
+        """
+        Return an error string specific for each kind of authentication method.
+
+        @return: The error string.
+        """
+        return None
+
+
+class SoledadTokenAuthMiddleware(SoledadAuthMiddleware):
+    """
+    Token based authentication.
+    """
+
+    TOKENS_DB = "tokens"
+    TOKENS_TYPE_KEY = "type"
+    TOKENS_TYPE_DEF = "Token"
+    TOKENS_USER_ID_KEY = "user_id"
+
+    TOKEN_AUTH_ERROR_STRING = "Incorrect address or token."
+
+    def _verify_authentication_scheme(self, scheme):
+        """
+        Verify if authentication scheme is valid.
+
+        @param scheme: Auth scheme extracted from the HTTP_AUTHORIZATION
+            header.
+        @type scheme: str
+
+        @return: Whether the authentitcation scheme is valid.
+        """
+        if scheme.lower() != 'token':
+            return False
+        return True
+
+    def _verify_authentication_data(self, uuid, auth_data):
+        """
+        Extract token from C{auth_data} and proceed with verification of
+        C{uuid} authentication.
+
+        @param uuid: The user UID.
+        @type uuid: str
+        @param auth_data: Authentication data (i.e. the token).
+        @type auth_data: str
+
+        @return: Whether the token is valid for authenticating the request.
+        @rtype: bool
+        """
+        token = auth_data  # we expect a cleartext token at this point
+        return self._verify_token_in_couchdb(uuid, token)
+
+    def _verify_token_in_couchdb(self, uuid, token):
+        """
+        Query couchdb to decide if C{token} is valid for C{uuid}.
+
+        @param uuid: The user uuid.
+        @type uuid: str
+        @param token: The token.
+        @type token: str
+        """
+        server = Server(url=self._app.state.couch_url)
+        try:
+            dbname = self.TOKENS_DB
+            db = server[dbname]
+            token = db.get(token)
+            if token is None:
+                return False
+            return token[self.TOKENS_TYPE_KEY] == self.TOKENS_TYPE_DEF and \
+                token[self.TOKENS_USER_ID_KEY] == uuid
+        except Exception as e:
+            log.err(e)
+            return False
+        return True
+
+    def _get_auth_error_string(self):
+        """
+        Get the error string for token auth.
+
+        @return: The error string.
+        """
+        return self.TOKEN_AUTH_ERROR_STRING