[refactor] move SRPAuth to SRPAuthImpl

Decouple SRPAuth from QT signaler and move it to SRPAuthImpl

1 files changed, 484 insertions, 462 deletions

diff --git a/src/leap/bitmask/crypto/srpauth.py b/src/leap/bitmask/crypto/srpauth.py
index f679430b..0a6513c8 100644
--- a/src/leap/bitmask/crypto/srpauth.py
+++ b/src/leap/bitmask/crypto/srpauth.py
@@ -118,465 +118,516 @@ class SRPAuthNoSessionId(SRPAuthenticationError):
     pass
 
 
-class SRPAuth(object):
+class SRPAuthImpl(object):
     """
-    SRPAuth singleton
+    Implementation of the SRPAuth interface
     """
 
-    class __impl(object):
+    LOGIN_KEY = "login"
+    A_KEY = "A"
+    CLIENT_AUTH_KEY = "client_auth"
+    SESSION_ID_KEY = "_session_id"
+    USER_VERIFIER_KEY = 'user[password_verifier]'
+    USER_SALT_KEY = 'user[password_salt]'
+    AUTHORIZATION_KEY = "Authorization"
+
+    def __init__(self, provider_config):
+        """
+        Constructor for SRPAuth implementation
+
+        :param provider_config: ProviderConfig needed to authenticate.
+        :type provider_config: ProviderConfig
         """
-        Implementation of the SRPAuth interface
+        leap_assert(provider_config,
+                    "We need a provider config to authenticate")
+
+        self._provider_config = provider_config
+        self._settings = Settings()
+
+        # **************************************************** #
+        # Dependency injection helpers, override this for more
+        # granular testing
+        self._fetcher = requests
+        self._srp = srp
+        self._hashfun = self._srp.SHA256
+        self._ng = self._srp.NG_1024
+        # **************************************************** #
+
+        self._reset_session()
+
+        self._session_id = None
+        self._session_id_lock = threading.Lock()
+        self._uuid = None
+        self._uuid_lock = threading.Lock()
+        self._token = None
+        self._token_lock = threading.Lock()
+
+        self._srp_user = None
+        self._srp_a = None
+
+        # User credentials stored for password changing checks
+        self._username = None
+        self._password = None
+
+    def _reset_session(self):
         """
+        Resets the current session and sets max retries to 30.
+        """
+        self._session = self._fetcher.session()
+        # We need to bump the default retries, otherwise logout
+        # fails most of the times
+        # NOTE: This is a workaround for the moment, the server
+        # side seems to return correctly every time, but it fails
+        # on the client end.
+        if requests_has_max_retries:
+            adapter = HTTPAdapter(max_retries=30)
+        else:
+            adapter = HTTPAdapter()
+        self._session.mount('https://', adapter)
+
+    def _safe_unhexlify(self, val):
+        """
+        Rounds the val to a multiple of 2 and returns the
+        unhexlified value
 
-        LOGIN_KEY = "login"
-        A_KEY = "A"
-        CLIENT_AUTH_KEY = "client_auth"
-        SESSION_ID_KEY = "_session_id"
-        USER_VERIFIER_KEY = 'user[password_verifier]'
-        USER_SALT_KEY = 'user[password_salt]'
-        AUTHORIZATION_KEY = "Authorization"
+        :param val: hexlified value
+        :type val: str
 
-        def __init__(self, provider_config, signaler=None):
-            """
-            Constructor for SRPAuth implementation
+        :rtype: binary hex data
+        :return: unhexlified val
+        """
+        return binascii.unhexlify(val) \
+            if (len(val) % 2 == 0) else binascii.unhexlify('0' + val)
 
-            :param provider_config: ProviderConfig needed to authenticate.
-            :type provider_config: ProviderConfig
-            :param signaler: Signaler object used to receive notifications
-                            from the backend
-            :type signaler: Signaler
-            """
-            leap_assert(provider_config,
-                        "We need a provider config to authenticate")
+    def _authentication_preprocessing(self, username, password):
+        """
+        Generates the SRP.User to get the A SRP parameter
 
-            self._provider_config = provider_config
-            self._signaler = signaler
-            self._settings = Settings()
-
-            # **************************************************** #
-            # Dependency injection helpers, override this for more
-            # granular testing
-            self._fetcher = requests
-            self._srp = srp
-            self._hashfun = self._srp.SHA256
-            self._ng = self._srp.NG_1024
-            # **************************************************** #
-
-            self._reset_session()
-
-            self._session_id = None
-            self._session_id_lock = threading.Lock()
-            self._uuid = None
-            self._uuid_lock = threading.Lock()
-            self._token = None
-            self._token_lock = threading.Lock()
-
-            self._srp_user = None
-            self._srp_a = None
+        :param username: username to login
+        :type username: str
+        :param password: password for the username
+        :type password: str
+        """
+        logger.debug("Authentication preprocessing...")
 
-            # User credentials stored for password changing checks
-            self._username = None
-            self._password = None
+        self._srp_user = self._srp.User(username.encode('utf-8'),
+                                        password.encode('utf-8'),
+                                        self._hashfun, self._ng)
+        _, A = self._srp_user.start_authentication()
 
-        def _reset_session(self):
-            """
-            Resets the current session and sets max retries to 30.
-            """
-            self._session = self._fetcher.session()
-            # We need to bump the default retries, otherwise logout
-            # fails most of the times
-            # NOTE: This is a workaround for the moment, the server
-            # side seems to return correctly every time, but it fails
-            # on the client end.
-            if requests_has_max_retries:
-                adapter = HTTPAdapter(max_retries=30)
-            else:
-                adapter = HTTPAdapter()
-            self._session.mount('https://', adapter)
+        self._srp_a = A
 
-        def _safe_unhexlify(self, val):
-            """
-            Rounds the val to a multiple of 2 and returns the
-            unhexlified value
+    def _start_authentication(self, _, username):
+        """
+        Sends the first request for authentication to retrieve the
+        salt and B parameter
+
+        Might raise all SRPAuthenticationError based:
+          SRPAuthenticationError
+          SRPAuthConnectionError
+          SRPAuthBadStatusCode
+          SRPAuthNoSalt
+          SRPAuthNoB
+
+        :param _: IGNORED, output from the previous callback (None)
+        :type _: IGNORED
+        :param username: username to login
+        :type username: str
 
-            :param val: hexlified value
-            :type val: str
+        :return: salt and B parameters
+        :rtype: tuple
+        """
+        logger.debug("Starting authentication process...")
+        try:
+            auth_data = {
+                self.LOGIN_KEY: username,
+                self.A_KEY: binascii.hexlify(self._srp_a)
+            }
+            sessions_url = "%s/%s/%s/" % \
+                (self._provider_config.get_api_uri(),
+                 self._provider_config.get_api_version(),
+                 "sessions")
+
+            ca_cert_path = self._provider_config.get_ca_cert_path()
+            ca_cert_path = ca_cert_path.encode(sys.getfilesystemencoding())
+
+            init_session = self._session.post(sessions_url,
+                                              data=auth_data,
+                                              verify=ca_cert_path,
+                                              timeout=REQUEST_TIMEOUT)
+            # Clean up A value, we don't need it anymore
+            self._srp_a = None
+        except requests.exceptions.ConnectionError as e:
+            logger.error("No connection made (salt): {0!r}".format(e))
+            raise SRPAuthConnectionError()
+        except Exception as e:
+            logger.error("Unknown error: %r" % (e,))
+            raise SRPAuthenticationError()
 
-            :rtype: binary hex data
-            :return: unhexlified val
-            """
-            return binascii.unhexlify(val) \
-                if (len(val) % 2 == 0) else binascii.unhexlify('0' + val)
+        content, mtime = reqhelper.get_content(init_session)
 
-        def _authentication_preprocessing(self, username, password):
-            """
-            Generates the SRP.User to get the A SRP parameter
+        if init_session.status_code not in (200,):
+            logger.error("No valid response (salt): "
+                         "Status code = %r. Content: %r" %
+                         (init_session.status_code, content))
+            if init_session.status_code == 422:
+                logger.error("Invalid username or password.")
+                raise SRPAuthBadUserOrPassword()
 
-            :param username: username to login
-            :type username: str
-            :param password: password for the username
-            :type password: str
-            """
-            logger.debug("Authentication preprocessing...")
+            logger.error("There was a problem with authentication.")
+            raise SRPAuthBadStatusCode()
 
-            self._srp_user = self._srp.User(username.encode('utf-8'),
-                                            password.encode('utf-8'),
-                                            self._hashfun, self._ng)
-            _, A = self._srp_user.start_authentication()
+        json_content = json.loads(content)
+        salt = json_content.get("salt", None)
+        B = json_content.get("B", None)
 
-            self._srp_a = A
+        if salt is None:
+            logger.error("The server didn't send the salt parameter.")
+            raise SRPAuthNoSalt()
+        if B is None:
+            logger.error("The server didn't send the B parameter.")
+            raise SRPAuthNoB()
 
-        def _start_authentication(self, _, username):
-            """
-            Sends the first request for authentication to retrieve the
-            salt and B parameter
+        return salt, B
 
-            Might raise all SRPAuthenticationError based:
-              SRPAuthenticationError
-              SRPAuthConnectionError
-              SRPAuthBadStatusCode
-              SRPAuthNoSalt
-              SRPAuthNoB
+    def _process_challenge(self, salt_B, username):
+        """
+        Given the salt and B processes the auth challenge and
+        generates the M2 parameter
+
+        Might raise SRPAuthenticationError based:
+          SRPAuthenticationError
+          SRPAuthBadDataFromServer
+          SRPAuthConnectionError
+          SRPAuthJSONDecodeError
+          SRPAuthBadUserOrPassword
+
+        :param salt_B: salt and B parameters for the username
+        :type salt_B: tuple
+        :param username: username for this session
+        :type username: str
 
-            :param _: IGNORED, output from the previous callback (None)
-            :type _: IGNORED
-            :param username: username to login
-            :type username: str
+        :return: the M2 SRP parameter
+        :rtype: str
+        """
+        logger.debug("Processing challenge...")
+        try:
+            salt, B = salt_B
+            unhex_salt = self._safe_unhexlify(salt)
+            unhex_B = self._safe_unhexlify(B)
+        except (TypeError, ValueError) as e:
+            logger.error("Bad data from server: %r" % (e,))
+            raise SRPAuthBadDataFromServer()
+        M = self._srp_user.process_challenge(unhex_salt, unhex_B)
+
+        auth_url = "%s/%s/%s/%s" % (self._provider_config.get_api_uri(),
+                                    self._provider_config.
+                                    get_api_version(),
+                                    "sessions",
+                                    username)
+
+        auth_data = {
+            self.CLIENT_AUTH_KEY: binascii.hexlify(M)
+        }
 
-            :return: salt and B parameters
-            :rtype: tuple
-            """
-            logger.debug("Starting authentication process...")
-            try:
-                auth_data = {
-                    self.LOGIN_KEY: username,
-                    self.A_KEY: binascii.hexlify(self._srp_a)
-                }
-                sessions_url = "%s/%s/%s/" % \
-                    (self._provider_config.get_api_uri(),
-                     self._provider_config.get_api_version(),
-                     "sessions")
-
-                ca_cert_path = self._provider_config.get_ca_cert_path()
-                ca_cert_path = ca_cert_path.encode(sys.getfilesystemencoding())
-
-                init_session = self._session.post(sessions_url,
-                                                  data=auth_data,
-                                                  verify=ca_cert_path,
-                                                  timeout=REQUEST_TIMEOUT)
-                # Clean up A value, we don't need it anymore
-                self._srp_a = None
-            except requests.exceptions.ConnectionError as e:
-                logger.error("No connection made (salt): {0!r}".format(e))
-                raise SRPAuthConnectionError()
-            except Exception as e:
-                logger.error("Unknown error: %r" % (e,))
-                raise SRPAuthenticationError()
-
-            content, mtime = reqhelper.get_content(init_session)
-
-            if init_session.status_code not in (200,):
-                logger.error("No valid response (salt): "
-                             "Status code = %r. Content: %r" %
-                             (init_session.status_code, content))
-                if init_session.status_code == 422:
-                    logger.error("Invalid username or password.")
-                    raise SRPAuthBadUserOrPassword()
-
-                logger.error("There was a problem with authentication.")
-                raise SRPAuthBadStatusCode()
-
-            json_content = json.loads(content)
-            salt = json_content.get("salt", None)
-            B = json_content.get("B", None)
-
-            if salt is None:
-                logger.error("The server didn't send the salt parameter.")
-                raise SRPAuthNoSalt()
-            if B is None:
-                logger.error("The server didn't send the B parameter.")
-                raise SRPAuthNoB()
-
-            return salt, B
-
-        def _process_challenge(self, salt_B, username):
-            """
-            Given the salt and B processes the auth challenge and
-            generates the M2 parameter
-
-            Might raise SRPAuthenticationError based:
-              SRPAuthenticationError
-              SRPAuthBadDataFromServer
-              SRPAuthConnectionError
-              SRPAuthJSONDecodeError
-              SRPAuthBadUserOrPassword
-
-            :param salt_B: salt and B parameters for the username
-            :type salt_B: tuple
-            :param username: username for this session
-            :type username: str
-
-            :return: the M2 SRP parameter
-            :rtype: str
-            """
-            logger.debug("Processing challenge...")
-            try:
-                salt, B = salt_B
-                unhex_salt = self._safe_unhexlify(salt)
-                unhex_B = self._safe_unhexlify(B)
-            except (TypeError, ValueError) as e:
-                logger.error("Bad data from server: %r" % (e,))
-                raise SRPAuthBadDataFromServer()
-            M = self._srp_user.process_challenge(unhex_salt, unhex_B)
-
-            auth_url = "%s/%s/%s/%s" % (self._provider_config.get_api_uri(),
-                                        self._provider_config.
-                                        get_api_version(),
-                                        "sessions",
-                                        username)
+        try:
+            auth_result = self._session.put(auth_url,
+                                            data=auth_data,
+                                            verify=self._provider_config.
+                                            get_ca_cert_path(),
+                                            timeout=REQUEST_TIMEOUT)
+        except requests.exceptions.ConnectionError as e:
+            logger.error("No connection made (HAMK): %r" % (e,))
+            raise SRPAuthConnectionError()
 
-            auth_data = {
-                self.CLIENT_AUTH_KEY: binascii.hexlify(M)
-            }
+        try:
+            content, mtime = reqhelper.get_content(auth_result)
+        except JSONDecodeError:
+            logger.error("Bad JSON content in auth result.")
+            raise SRPAuthJSONDecodeError()
 
+        if auth_result.status_code == 422:
+            error = ""
             try:
-                auth_result = self._session.put(auth_url,
-                                                data=auth_data,
-                                                verify=self._provider_config.
-                                                get_ca_cert_path(),
-                                                timeout=REQUEST_TIMEOUT)
-            except requests.exceptions.ConnectionError as e:
-                logger.error("No connection made (HAMK): %r" % (e,))
-                raise SRPAuthConnectionError()
+                error = json.loads(content).get("errors", "")
+            except ValueError:
+                logger.error("Problem parsing the received response: %s"
+                             % (content,))
+            except AttributeError:
+                logger.error("Expecting a dict but something else was "
+                             "received: %s", (content,))
+            logger.error("[%s] Wrong password (HAMK): [%s]" %
+                         (auth_result.status_code, error))
+            raise SRPAuthBadUserOrPassword()
+
+        if auth_result.status_code not in (200,):
+            logger.error("No valid response (HAMK): "
+                         "Status code = %s. Content = %r" %
+                         (auth_result.status_code, content))
+            raise SRPAuthBadStatusCode()
+
+        return json.loads(content)
+
+    def _extract_data(self, json_content):
+        """
+        Extracts the necessary parameters from json_content (M2,
+        id, token)
 
-            try:
-                content, mtime = reqhelper.get_content(auth_result)
-            except JSONDecodeError:
-                logger.error("Bad JSON content in auth result.")
-                raise SRPAuthJSONDecodeError()
-
-            if auth_result.status_code == 422:
-                error = ""
-                try:
-                    error = json.loads(content).get("errors", "")
-                except ValueError:
-                    logger.error("Problem parsing the received response: %s"
-                                 % (content,))
-                except AttributeError:
-                    logger.error("Expecting a dict but something else was "
-                                 "received: %s", (content,))
-                logger.error("[%s] Wrong password (HAMK): [%s]" %
-                             (auth_result.status_code, error))
-                raise SRPAuthBadUserOrPassword()
+        Might raise SRPAuthenticationError based:
+          SRPBadDataFromServer
 
-            if auth_result.status_code not in (200,):
-                logger.error("No valid response (HAMK): "
-                             "Status code = %s. Content = %r" %
-                             (auth_result.status_code, content))
-                raise SRPAuthBadStatusCode()
+        :param json_content: Data received from the server
+        :type json_content: dict
+        """
+        try:
+            M2 = json_content.get("M2", None)
+            uuid = json_content.get("id", None)
+            token = json_content.get("token", None)
+        except Exception as e:
+            logger.error(e)
+            raise SRPAuthBadDataFromServer()
 
-            return json.loads(content)
+        self.set_uuid(uuid)
+        self.set_token(token)
 
-        def _extract_data(self, json_content):
-            """
-            Extracts the necessary parameters from json_content (M2,
-            id, token)
+        if M2 is None or self.get_uuid() is None:
+            logger.error("Something went wrong. Content = %r" %
+                         (json_content,))
+            raise SRPAuthBadDataFromServer()
 
-            Might raise SRPAuthenticationError based:
-              SRPBadDataFromServer
+        events_signal(
+            proto.CLIENT_UID, content=uuid,
+            reqcbk=lambda req, res: None)  # make the rpc call async
 
-            :param json_content: Data received from the server
-            :type json_content: dict
-            """
-            try:
-                M2 = json_content.get("M2", None)
-                uuid = json_content.get("id", None)
-                token = json_content.get("token", None)
-            except Exception as e:
-                logger.error(e)
-                raise SRPAuthBadDataFromServer()
+        return M2
 
-            self.set_uuid(uuid)
-            self.set_token(token)
+    def _verify_session(self, M2):
+        """
+        Verifies the session based on the M2 parameter. If the
+        verification succeeds, it sets the session_id for this
+        session
 
-            if M2 is None or self.get_uuid() is None:
-                logger.error("Something went wrong. Content = %r" %
-                             (json_content,))
-                raise SRPAuthBadDataFromServer()
+        Might raise SRPAuthenticationError based:
+          SRPAuthBadDataFromServer
+          SRPAuthVerificationFailed
 
-            events_signal(
-                proto.CLIENT_UID, content=uuid,
-                reqcbk=lambda req, res: None)  # make the rpc call async
+        :param M2: M2 SRP parameter
+        :type M2: str
+        """
+        logger.debug("Verifying session...")
+        try:
+            unhex_M2 = self._safe_unhexlify(M2)
+        except TypeError:
+            logger.error("Bad data from server (HAWK)")
+            raise SRPAuthBadDataFromServer()
 
-            return M2
+        self._srp_user.verify_session(unhex_M2)
 
-        def _verify_session(self, M2):
-            """
-            Verifies the session based on the M2 parameter. If the
-            verification succeeds, it sets the session_id for this
-            session
+        if not self._srp_user.authenticated():
+            logger.error("Auth verification failed.")
+            raise SRPAuthVerificationFailed()
+        logger.debug("Session verified.")
 
-            Might raise SRPAuthenticationError based:
-              SRPAuthBadDataFromServer
-              SRPAuthVerificationFailed
+        session_id = self._session.cookies.get(self.SESSION_ID_KEY, None)
+        if not session_id:
+            logger.error("Bad cookie from server (missing _session_id)")
+            raise SRPAuthNoSessionId()
 
-            :param M2: M2 SRP parameter
-            :type M2: str
-            """
-            logger.debug("Verifying session...")
-            try:
-                unhex_M2 = self._safe_unhexlify(M2)
-            except TypeError:
-                logger.error("Bad data from server (HAWK)")
-                raise SRPAuthBadDataFromServer()
+        events_signal(
+            proto.CLIENT_SESSION_ID, content=session_id,
+            reqcbk=lambda req, res: None)  # make the rpc call asynch
 
-            self._srp_user.verify_session(unhex_M2)
+        self.set_session_id(session_id)
+        logger.debug("SUCCESS LOGIN")
+        return True
 
-            if not self._srp_user.authenticated():
-                logger.error("Auth verification failed.")
-                raise SRPAuthVerificationFailed()
-            logger.debug("Session verified.")
+    def _threader(self, cb, res, *args, **kwargs):
+        return threads.deferToThread(cb, res, *args, **kwargs)
 
-            session_id = self._session.cookies.get(self.SESSION_ID_KEY, None)
-            if not session_id:
-                logger.error("Bad cookie from server (missing _session_id)")
-                raise SRPAuthNoSessionId()
+    def _change_password(self, current_password, new_password):
+        """
+        Changes the password for the currently logged user if the current
+        password match.
+        It requires to be authenticated.
 
-            events_signal(
-                proto.CLIENT_SESSION_ID, content=session_id,
-                reqcbk=lambda req, res: None)  # make the rpc call async
+        Might raise:
+            SRPAuthBadUserOrPassword
+            requests.exceptions.HTTPError
 
-            self.set_session_id(session_id)
+        :param current_password: the current password for the logged user.
+        :type current_password: str
+        :param new_password: the new password for the user
+        :type new_password: str
+        """
+        leap_assert(self.get_uuid() is not None)
+
+        if current_password != self._password:
+            raise SRPAuthBadUserOrPassword
+
+        url = "%s/%s/users/%s.json" % (
+            self._provider_config.get_api_uri(),
+            self._provider_config.get_api_version(),
+            self.get_uuid())
+
+        salt, verifier = self._srp.create_salted_verification_key(
+            self._username.encode('utf-8'), new_password.encode('utf-8'),
+            self._hashfun, self._ng)
+
+        cookies = {self.SESSION_ID_KEY: self.get_session_id()}
+        headers = {
+            self.AUTHORIZATION_KEY:
+            "Token token={0}".format(self.get_token())
+        }
+        user_data = {
+            self.USER_VERIFIER_KEY: binascii.hexlify(verifier),
+            self.USER_SALT_KEY: binascii.hexlify(salt)
+        }
+
+        change_password = self._session.put(
+            url, data=user_data,
+            verify=self._provider_config.get_ca_cert_path(),
+            cookies=cookies,
+            timeout=REQUEST_TIMEOUT,
+            headers=headers)
+
+        # In case of non 2xx it raises HTTPError
+        change_password.raise_for_status()
+
+        self._password = new_password
 
-        def _threader(self, cb, res, *args, **kwargs):
-            return threads.deferToThread(cb, res, *args, **kwargs)
+    def change_password(self, current_password, new_password):
+        """
+        Changes the password for the currently logged user if the current
+        password match.
+        It requires to be authenticated.
 
-        def _change_password(self, current_password, new_password):
-            """
-            Changes the password for the currently logged user if the current
-            password match.
-            It requires to be authenticated.
+        :param current_password: the current password for the logged user.
+        :type current_password: str
+        :param new_password: the new password for the user
+        :type new_password: str
+        """
+        d = threads.deferToThread(
+            self._change_password, current_password, new_password)
+        return d
 
-            Might raise:
-                SRPAuthBadUserOrPassword
-                requests.exceptions.HTTPError
+    def authenticate(self, username, password):
+        """
+        Executes the whole authentication process for a user
 
-            :param current_password: the current password for the logged user.
-            :type current_password: str
-            :param new_password: the new password for the user
-            :type new_password: str
-            """
-            leap_assert(self.get_uuid() is not None)
+        Might raise SRPAuthenticationError
 
-            if current_password != self._password:
-                raise SRPAuthBadUserOrPassword
+        :param username: username for this session
+        :type username: unicode
+        :param password: password for this user
+        :type password: unicode
 
-            url = "%s/%s/users/%s.json" % (
-                self._provider_config.get_api_uri(),
-                self._provider_config.get_api_version(),
-                self.get_uuid())
+        :returns: A defer on a different thread
+        :rtype: twisted.internet.defer.Deferred
+        """
+        leap_assert(self.get_session_id() is None, "Already logged in")
+
+        # User credentials stored for password changing checks
+        self._username = username
+        self._password = password
+
+        self._reset_session()
+
+        d = threads.deferToThread(self._authentication_preprocessing,
+                                  username=username,
+                                  password=password)
+        
+        d.addCallback(partial(self._start_authentication, username=username))
+        d.addCallback(partial(self._process_challenge, username=username))
+        d.addCallback(self._extract_data)
+        d.addCallback(self._verify_session)
+        return d
 
-            salt, verifier = self._srp.create_salted_verification_key(
-                self._username.encode('utf-8'), new_password.encode('utf-8'),
-                self._hashfun, self._ng)
+    def logout(self):
+        """
+        Logs out the current session.
+        Expects a session_id to exists, might raise AssertionError
+        """
+        logger.debug("Starting logout...")
 
-            cookies = {self.SESSION_ID_KEY: self.get_session_id()}
-            headers = {
-                self.AUTHORIZATION_KEY:
-                "Token token={0}".format(self.get_token())
-            }
-            user_data = {
-                self.USER_VERIFIER_KEY: binascii.hexlify(verifier),
-                self.USER_SALT_KEY: binascii.hexlify(salt)
-            }
+        if self.get_session_id() is None:
+            logger.debug("Already logged out")
+            return
 
-            change_password = self._session.put(
-                url, data=user_data,
-                verify=self._provider_config.get_ca_cert_path(),
-                cookies=cookies,
-                timeout=REQUEST_TIMEOUT,
-                headers=headers)
+        logout_url = "%s/%s/%s/" % (self._provider_config.get_api_uri(),
+                                    self._provider_config.
+                                    get_api_version(),
+                                    "logout")
+        try:
+            self._session.delete(logout_url,
+                                 data=self.get_session_id(),
+                                 verify=self._provider_config.
+                                 get_ca_cert_path(),
+                                 timeout=REQUEST_TIMEOUT)
+        except Exception as e:
+            logger.warning("Something went wrong with the logout: %r" %
+                           (e,))
+            raise
+        else:
+            self.set_session_id(None)
+            self.set_uuid(None)
+            self.set_token(None)
+            # Also reset the session
+            self._session = self._fetcher.session()
+            logger.debug("Successfully logged out.")
 
-            # In case of non 2xx it raises HTTPError
-            change_password.raise_for_status()
+    def set_session_id(self, session_id):
+        with self._session_id_lock:
+            self._session_id = session_id
 
-            self._password = new_password
+    def get_session_id(self):
+        with self._session_id_lock:
+            return self._session_id
 
-        def change_password(self, current_password, new_password):
-            """
-            Changes the password for the currently logged user if the current
-            password match.
-            It requires to be authenticated.
+    def set_uuid(self, uuid):
+        with self._uuid_lock:
+            full_uid = "%s@%s" % (
+                self._username, self._provider_config.get_domain())
+            if uuid is not None:  # avoid removing the uuid from settings
+                self._settings.set_uuid(full_uid, uuid)
+            self._uuid = uuid
 
-            :param current_password: the current password for the logged user.
-            :type current_password: str
-            :param new_password: the new password for the user
-            :type new_password: str
-            """
-            d = threads.deferToThread(
-                self._change_password, current_password, new_password)
-            d.addCallback(self._change_password_ok)
-            d.addErrback(self._change_password_error)
+    def get_uuid(self):
+        with self._uuid_lock:
+            return self._uuid
 
-        def _change_password_ok(self, _):
-            """
-            Password change callback.
-            """
-            if self._signaler is not None:
-                self._signaler.signal(self._signaler.srp_password_change_ok)
+    def set_token(self, token):
+        with self._token_lock:
+            self._token = token
 
-        def _change_password_error(self, failure):
-            """
-            Password change errback.
-            """
-            logger.debug(
-                "Error changing password. Failure: {0}".format(failure))
-            if self._signaler is None:
-                return
+    def get_token(self):
+        with self._token_lock:
+            return self._token
 
-            if failure.check(SRPAuthBadUserOrPassword):
-                self._signaler.signal(self._signaler.srp_password_change_badpw)
-            else:
-                self._signaler.signal(self._signaler.srp_password_change_error)
+    def is_authenticated(self):
+        """
+        Return whether the user is authenticated or not.
 
-        def authenticate(self, username, password):
-            """
-            Executes the whole authentication process for a user
+        :rtype: bool
+        """
+        user = self._srp_user
+        if user is not None:
+            return user.authenticated()
 
-            Might raise SRPAuthenticationError
+        return False
 
-            :param username: username for this session
-            :type username: unicode
-            :param password: password for this user
-            :type password: unicode
 
-            :returns: A defer on a different thread
-            :rtype: twisted.internet.defer.Deferred
-            """
-            leap_assert(self.get_session_id() is None, "Already logged in")
-
-            # User credentials stored for password changing checks
-            self._username = username
-            self._password = password
-
-            self._reset_session()
-
-            # FIXME ---------------------------------------------------------
-            # 1. it makes no sense to defer each callback to a thread - DONE
-            # 2. the decision to use threads should be at another level.
-            #    (although it's not really needed, that was a hack around
-            #    the gui blocks)
-            #    it makes very hard to test this. The  __impl could be
-            #    separated and decoupled from the provider_config abstraction.
-
-            d = threads.deferToThread(self._authentication_preprocessing,
-                                      username=username,
-                                      password=password)
-
-            d.addCallback(partial(self._start_authentication, username=username))
-            d.addCallback(partial(self._process_challenge, username=username))
-            d.addCallback(self._extract_data)
-            d.addCallback(self._verify_session)
+class SRPAuth(object):
+    """
+    SRPAuth singleton
+    """
+    class __impl(SRPAuthImpl):
+
+        def __init__(self, provider_config, signaler=None):
+            SRPAuthImpl.__init__(self, provider_config)
+            self._signaler = signaler
+
+        def authenticate(self, username, password):
+            d = SRPAuthImpl.authenticate(self, username, password)
             d.addCallback(self._authenticate_ok)
             d.addErrback(self._authenticate_error)
             return d
@@ -620,82 +671,53 @@ class SRPAuth(object):
 
             self._signaler.signal(signal)
 
-        def logout(self):
+        def change_password(self, current_password, new_password):
+            """
+            Changes the password for the currently logged user if the current
+            password match.
+            It requires to be authenticated.
+
+            :param current_password: the current password for the logged user.
+            :type current_password: str
+            :param new_password: the new password for the user
+            :type new_password: str
             """
-            Logs out the current session.
-            Expects a session_id to exists, might raise AssertionError
+            d = SRPAuthImpl.change_password(self, current_password, new_password)
+            d.addCallback(self._change_password_ok)
+            d.addErrback(self._change_password_error)
+            return d
+
+        def _change_password_ok(self, _):
             """
-            logger.debug("Starting logout...")
+            Password change callback.
+            """
+            if self._signaler is not None:
+                self._signaler.signal(self._signaler.srp_password_change_ok)
 
-            if self.get_session_id() is None:
-                logger.debug("Already logged out")
+        def _change_password_error(self, failure):
+            """
+            Password change errback.
+            """
+            logger.debug(
+                "Error changing password. Failure: {0}".format(failure))
+            if self._signaler is None:
                 return
 
-            logout_url = "%s/%s/%s/" % (self._provider_config.get_api_uri(),
-                                        self._provider_config.
-                                        get_api_version(),
-                                        "logout")
+            if failure.check(SRPAuthBadUserOrPassword):
+                self._signaler.signal(self._signaler.srp_password_change_badpw)
+            else:
+                self._signaler.signal(self._signaler.srp_password_change_error)
+
+        def logout(self):
             try:
-                self._session.delete(logout_url,
-                                     data=self.get_session_id(),
-                                     verify=self._provider_config.
-                                     get_ca_cert_path(),
-                                     timeout=REQUEST_TIMEOUT)
-            except Exception as e:
-                logger.warning("Something went wrong with the logout: %r" %
-                               (e,))
+                SRPAuthImpl.logout(self)
+                if self._signaler is not None:
+                    self._signaler.signal(self._signaler.srp_logout_ok)
+            except Exception:
                 if self._signaler is not None:
                     self._signaler.signal(self._signaler.srp_logout_error)
                 raise
-            else:
-                self.set_session_id(None)
-                self.set_uuid(None)
-                self.set_token(None)
-                # Also reset the session
-                self._session = self._fetcher.session()
-                logger.debug("Successfully logged out.")
-                if self._signaler is not None:
-                    self._signaler.signal(self._signaler.srp_logout_ok)
-
-        def set_session_id(self, session_id):
-            with self._session_id_lock:
-                self._session_id = session_id
-
-        def get_session_id(self):
-            with self._session_id_lock:
-                return self._session_id
-
-        def set_uuid(self, uuid):
-            with self._uuid_lock:
-                full_uid = "%s@%s" % (
-                    self._username, self._provider_config.get_domain())
-                if uuid is not None:  # avoid removing the uuid from settings
-                    self._settings.set_uuid(full_uid, uuid)
-                self._uuid = uuid
-
-        def get_uuid(self):
-            with self._uuid_lock:
-                return self._uuid
-
-        def set_token(self, token):
-            with self._token_lock:
-                self._token = token
-
-        def get_token(self):
-            with self._token_lock:
-                return self._token
-
-        def is_authenticated(self):
-            """
-            Return whether the user is authenticated or not.
-
-            :rtype: bool
-            """
-            user = self._srp_user
-            if user is not None:
-                return user.authenticated()
 
-            return False
 
     __instance = None