Add tests for SRPAuth class

1 files changed, 755 insertions, 0 deletions

diff --git a/src/leap/crypto/tests/test_srpauth.py b/src/leap/crypto/tests/test_srpauth.py
new file mode 100644
index 00000000..9a684a8f
--- /dev/null
+++ b/src/leap/crypto/tests/test_srpauth.py
@@ -0,0 +1,755 @@
+# -*- coding: utf-8 -*-
+# test_srpauth.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/>.
+"""
+Tests for:
+    * leap/crypto/srpauth.py
+"""
+try:
+    import unittest2 as unittest
+except ImportError:
+    import unittest
+import os
+import sys
+import binascii
+import requests
+import mock
+
+from mock import MagicMock
+from nose.twistedtools import reactor, deferred
+from twisted.python import log
+from twisted.internet import threads
+from functools import partial
+from requests.models import Response
+from simplejson.decoder import JSONDecodeError
+
+from leap.common.testing.https_server import where
+from leap.config.providerconfig import ProviderConfig
+from leap.crypto import srpregister, srpauth
+from leap.crypto.tests import fake_provider
+
+log.startLogging(sys.stdout)
+
+
+def _get_capath():
+    return where("cacert.pem")
+
+_here = os.path.split(__file__)[0]
+
+
+class ImproperlyConfiguredError(Exception):
+    """
+    Raised if the test provider is missing configuration
+    """
+
+
+class SRPAuthTestCase(unittest.TestCase):
+    """
+    Tests for the SRPAuth class
+    """
+    __name__ = "SRPAuth tests"
+
+    def setUp(self):
+        """
+        Sets up this TestCase with a simple and faked provider instance:
+
+        * runs a threaded reactor
+        * loads a mocked ProviderConfig that points to the certs in the
+          leap.common.testing module.
+        """
+        factory = fake_provider.get_provider_factory()
+        http = reactor.listenTCP(0, factory)
+        https = reactor.listenSSL(
+            0, factory,
+            fake_provider.OpenSSLServerContextFactory())
+        get_port = lambda p: p.getHost().port
+        self.http_port = get_port(http)
+        self.https_port = get_port(https)
+
+        provider = ProviderConfig()
+        provider.get_ca_cert_path = MagicMock()
+        provider.get_ca_cert_path.return_value = _get_capath()
+
+        provider.get_api_uri = MagicMock()
+        provider.get_api_uri.return_value = self._get_https_uri()
+
+        loaded = provider.load(path=os.path.join(
+            _here, "test_provider.json"))
+        if not loaded:
+            raise ImproperlyConfiguredError(
+                "Could not load test provider config")
+        self.register = srpregister.SRPRegister(provider_config=provider)
+        self.provider = provider
+        self.TEST_USER = "register_test_auth"
+        self.TEST_PASS = "pass"
+
+        # Reset the singleton
+        srpauth.SRPAuth._SRPAuth__instance = None
+        self.auth = srpauth.SRPAuth(self.provider)
+        self.auth_backend = self.auth._SRPAuth__instance
+
+        self.old_post = self.auth_backend._session.post
+        self.old_put = self.auth_backend._session.put
+        self.old_delete = self.auth_backend._session.delete
+
+        self.old_start_auth = self.auth_backend._start_authentication
+        self.old_proc_challenge = self.auth_backend._process_challenge
+        self.old_extract_data = self.auth_backend._extract_data
+        self.old_verify_session = self.auth_backend._verify_session
+        self.old_auth_preproc = self.auth_backend._authentication_preprocessing
+        self.old_get_sid = self.auth_backend.get_session_id
+        self.old_cookie_get = self.auth_backend._session.cookies.get
+        self.old_auth = self.auth_backend.authenticate
+
+    def tearDown(self):
+        self.auth_backend._session.post = self.old_post
+        self.auth_backend._session.put = self.old_put
+        self.auth_backend._session.delete = self.old_delete
+
+        self.auth_backend._start_authentication = self.old_start_auth
+        self.auth_backend._process_challenge = self.old_proc_challenge
+        self.auth_backend._extract_data = self.old_extract_data
+        self.auth_backend._verify_session = self.old_verify_session
+        self.auth_backend._authentication_preprocessing = self.old_auth_preproc
+        self.auth_backend.get_session_id = self.old_get_sid
+        self.auth_backend._session.cookies.get = self.old_cookie_get
+        self.auth_backend.authenticate = self.old_auth
+
+    # helper methods
+
+    def _get_https_uri(self):
+        """
+        Returns a https uri with the right https port initialized
+        """
+        return "https://localhost:%s" % (self.https_port,)
+
+    # Auth tests
+
+    def _prepare_auth_test(self, code=200, side_effect=None):
+        """
+        Creates the needed defers to test several test situations. It
+        adds up to the auth preprocessing step.
+
+        :param code: status code for the response of POST in requests
+        :type code: int
+        :param side_effect: side effect triggered by the POST method
+                            in requests
+        :type side_effect: some kind of Exception
+
+        :returns: the defer that is created
+        :rtype: defer.Deferred
+        """
+        res = Response()
+        res.status_code = code
+        self.auth_backend._session.post = MagicMock(return_value=res,
+                                                    side_effect=side_effect)
+
+        d = threads.deferToThread(self.register.register_user,
+                                  self.TEST_USER,
+                                  self.TEST_PASS)
+
+        def wrapper_preproc(*args):
+            return threads.deferToThread(
+                self.auth_backend._authentication_preprocessing,
+                self.TEST_USER, self.TEST_PASS)
+
+        d.addCallback(wrapper_preproc)
+
+        return d
+
+    def test_safe_unhexlify(self):
+        input_value = "somestring"
+        test_value = binascii.hexlify(input_value)
+        self.assertEqual(
+            self.auth_backend._safe_unhexlify(test_value),
+            input_value)
+
+    def test_safe_unhexlify_not_raises(self):
+        input_value = "somestring"
+        test_value = binascii.hexlify(input_value)[:-1]
+
+        with self.assertRaises(TypeError):
+            binascii.unhexlify(test_value)
+
+        self.auth_backend._safe_unhexlify(test_value)
+
+    def test_preprocessing_loads_a(self):
+        self.assertEqual(self.auth_backend._srp_a, None)
+        self.auth_backend._authentication_preprocessing("user", "pass")
+        self.assertIsNotNone(self.auth_backend._srp_a)
+        self.assertTrue(len(self.auth_backend._srp_a) > 0)
+
+    @deferred()
+    def test_start_authentication(self):
+        d = threads.deferToThread(self.register.register_user, self.TEST_USER,
+                                  self.TEST_PASS)
+
+        def wrapper_preproc(*args):
+            return threads.deferToThread(
+                self.auth_backend._authentication_preprocessing,
+                self.TEST_USER, self.TEST_PASS)
+
+        d.addCallback(wrapper_preproc)
+
+        def wrapper(_):
+            return threads.deferToThread(
+                self.auth_backend._start_authentication,
+                None, self.TEST_USER)
+
+        d.addCallback(wrapper)
+        return d
+
+    @deferred()
+    def test_start_authentication_fails_connerror(self):
+        d = self._prepare_auth_test(
+            side_effect=requests.exceptions.ConnectionError())
+
+        def wrapper(_):
+            with self.assertRaises(srpauth.SRPAuthConnectionError):
+                self.auth_backend._start_authentication(None, self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_start_authentication_fails_any_error(self):
+        d = self._prepare_auth_test(side_effect=Exception())
+
+        def wrapper(_):
+            with self.assertRaises(srpauth.SRPAuthenticationError):
+                self.auth_backend._start_authentication(None, self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_start_authentication_fails_unknown_user(self):
+        d = self._prepare_auth_test(422)
+
+        def wrapper(_):
+            with self.assertRaises(srpauth.SRPAuthUnknownUser):
+                with mock.patch('leap.util.request_helpers.get_content',
+                                new_callable=MagicMock()) as \
+                        content:
+                    content.return_value = ("{}", 0)
+
+                    self.auth_backend._start_authentication(
+                        None, self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_start_authentication_fails_errorcode(self):
+        d = self._prepare_auth_test(302)
+
+        def wrapper(_):
+            with self.assertRaises(srpauth.SRPAuthBadStatusCode):
+                with mock.patch('leap.util.request_helpers.get_content',
+                                new_callable=MagicMock()) as \
+                        content:
+                    content.return_value = ("{}", 0)
+
+                    self.auth_backend._start_authentication(None,
+                                                            self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_start_authentication_fails_no_salt(self):
+        d = self._prepare_auth_test(200)
+
+        def wrapper(_):
+            with self.assertRaises(srpauth.SRPAuthNoSalt):
+                with mock.patch('leap.util.request_helpers.get_content',
+                                new_callable=MagicMock()) as \
+                        content:
+                    content.return_value = ("{}", 0)
+
+                    self.auth_backend._start_authentication(None,
+                                                            self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_start_authentication_fails_no_B(self):
+        d = self._prepare_auth_test(200)
+
+        def wrapper(_):
+            with self.assertRaises(srpauth.SRPAuthNoB):
+                with mock.patch('leap.util.request_helpers.get_content',
+                                new_callable=MagicMock()) as \
+                        content:
+                    content.return_value = ('{"salt": ""}', 0)
+
+                    self.auth_backend._start_authentication(None,
+                                                            self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_start_authentication_correct_saltb(self):
+        d = self._prepare_auth_test(200)
+
+        test_salt = "12345"
+        test_B = "67890"
+
+        def wrapper(_):
+            with mock.patch('leap.util.request_helpers.get_content',
+                            new_callable=MagicMock()) as \
+                    content:
+                content.return_value = ('{"salt":"%s", "B":"%s"}' % (test_salt,
+                                                                     test_B),
+                                        0)
+
+                salt, B = self.auth_backend._start_authentication(
+                    None,
+                    self.TEST_USER)
+                self.assertEqual(salt, test_salt)
+                self.assertEqual(B, test_B)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    def _prepare_auth_challenge(self):
+        """
+        Creates the needed defers to test several test situations. It
+        adds up to the start authentication step.
+
+        :returns: the defer that is created
+        :rtype: defer.Deferred
+        """
+        d = threads.deferToThread(self.register.register_user,
+                                  self.TEST_USER,
+                                  self.TEST_PASS)
+
+        def wrapper_preproc(*args):
+            return threads.deferToThread(
+                self.auth_backend._authentication_preprocessing,
+                self.TEST_USER, self.TEST_PASS)
+
+        d.addCallback(wrapper_preproc)
+
+        def wrapper_start(*args):
+            return threads.deferToThread(
+                self.auth_backend._start_authentication,
+                None, self.TEST_USER)
+
+        d.addCallback(wrapper_start)
+
+        return d
+
+    @deferred()
+    def test_process_challenge_wrong_saltb(self):
+        d = self._prepare_auth_challenge()
+
+        def wrapper(salt_B):
+            with self.assertRaises(srpauth.SRPAuthBadDataFromServer):
+                self.auth_backend._process_challenge("",
+                                                     username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+        return d
+
+    @deferred()
+    def test_process_challenge_requests_problem_raises(self):
+        d = self._prepare_auth_challenge()
+
+        self.auth_backend._session.put = MagicMock(
+            side_effect=requests.exceptions.ConnectionError())
+
+        def wrapper(salt_B):
+            with self.assertRaises(srpauth.SRPAuthConnectionError):
+                self.auth_backend._process_challenge(salt_B,
+                                                     username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+
+        return d
+
+    @deferred()
+    def test_process_challenge_json_decode_error(self):
+        d = self._prepare_auth_challenge()
+
+        def wrapper(salt_B):
+            with mock.patch('leap.util.request_helpers.get_content',
+                            new_callable=MagicMock()) as \
+                    content:
+                content.return_value = ("{", 0)
+                content.side_effect = JSONDecodeError("", "", 0)
+
+                with self.assertRaises(srpauth.SRPAuthJSONDecodeError):
+                   self.auth_backend._process_challenge(
+                       salt_B,
+                       username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+
+        return d
+
+    @deferred()
+    def test_process_challenge_bad_password(self):
+        d = self._prepare_auth_challenge()
+
+        res = Response()
+        res.status_code = 422
+        self.auth_backend._session.put = MagicMock(return_value=res)
+
+        def wrapper(salt_B):
+            with mock.patch('leap.util.request_helpers.get_content',
+                            new_callable=MagicMock()) as \
+                    content:
+                content.return_value = ("", 0)
+                with self.assertRaises(srpauth.SRPAuthBadPassword):
+                    self.auth_backend._process_challenge(
+                        salt_B,
+                        username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+
+        return d
+
+    @deferred()
+    def test_process_challenge_bad_password2(self):
+        d = self._prepare_auth_challenge()
+
+        res = Response()
+        res.status_code = 422
+        self.auth_backend._session.put = MagicMock(return_value=res)
+
+        def wrapper(salt_B):
+            with mock.patch('leap.util.request_helpers.get_content',
+                            new_callable=MagicMock()) as \
+                    content:
+                content.return_value = ("[]", 0)
+                with self.assertRaises(srpauth.SRPAuthBadPassword):
+                    self.auth_backend._process_challenge(
+                        salt_B,
+                        username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+
+        return d
+
+    @deferred()
+    def test_process_challenge_other_error_code(self):
+        d = self._prepare_auth_challenge()
+
+        res = Response()
+        res.status_code = 300
+        self.auth_backend._session.put = MagicMock(return_value=res)
+
+        def wrapper(salt_B):
+            with mock.patch('leap.util.request_helpers.get_content',
+                            new_callable=MagicMock()) as \
+                    content:
+                content.return_value = ("{}", 0)
+                with self.assertRaises(srpauth.SRPAuthBadStatusCode):
+                    self.auth_backend._process_challenge(
+                        salt_B,
+                        username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+
+        return d
+
+    @deferred()
+    def test_process_challenge(self):
+        d = self._prepare_auth_challenge()
+
+        def wrapper(salt_B):
+            self.auth_backend._process_challenge(salt_B,
+                                                 username=self.TEST_USER)
+
+        d.addCallback(partial(threads.deferToThread, wrapper))
+
+        return d
+
+    def test_extract_data_wrong_data(self):
+        with self.assertRaises(srpauth.SRPAuthBadDataFromServer):
+            self.auth_backend._extract_data(None)
+
+        with self.assertRaises(srpauth.SRPAuthBadDataFromServer):
+            self.auth_backend._extract_data("")
+
+    def test_extract_data_fails_on_wrong_data_from_server(self):
+        with self.assertRaises(srpauth.SRPAuthBadDataFromServer):
+            self.auth_backend._extract_data({})
+
+        with self.assertRaises(srpauth.SRPAuthBadDataFromServer):
+            self.auth_backend._extract_data({"M2": ""})
+
+    def test_extract_data_sets_uidtoken(self):
+        test_uid = "someuid"
+        test_m2 = "somem2"
+        test_token = "sometoken"
+        test_data = {
+            "M2": test_m2,
+            "id": test_uid,
+            "token": test_token
+        }
+        m2 = self.auth_backend._extract_data(test_data)
+
+        self.assertEqual(m2, test_m2)
+        self.assertEqual(self.auth_backend.get_uid(), test_uid)
+        self.assertEqual(self.auth_backend.get_uid(),
+                         self.auth.get_uid())
+        self.assertEqual(self.auth_backend.get_token(), test_token)
+        self.assertEqual(self.auth_backend.get_token(),
+                         self.auth.get_token())
+
+    def _prepare_verify_session(self):
+        """
+        Prepares the tests for verify session with needed steps
+        before. It adds up to the extract_data step.
+
+        :returns: The defer to chain to
+        :rtype: defer.Deferred
+        """
+        d = self._prepare_auth_challenge()
+
+        def wrapper_proc_challenge(salt_B):
+            return self.auth_backend._process_challenge(
+                salt_B,
+                username=self.TEST_USER)
+
+        def wrapper_extract_data(data):
+            return self.auth_backend._extract_data(data)
+
+        d.addCallback(partial(threads.deferToThread, wrapper_proc_challenge))
+        d.addCallback(partial(threads.deferToThread, wrapper_extract_data))
+
+        return d
+
+    @deferred()
+    def test_verify_session_unhexlifiable_m2(self):
+        d = self._prepare_verify_session()
+
+        def wrapper(M2):
+            with self.assertRaises(srpauth.SRPAuthBadDataFromServer):
+                self.auth_backend._verify_session("za")  # unhexlifiable value
+
+        d.addCallback(wrapper)
+
+        return d
+
+    @deferred()
+    def test_verify_session_unverifiable_m2(self):
+        d = self._prepare_verify_session()
+
+        def wrapper(M2):
+            with self.assertRaises(srpauth.SRPAuthVerificationFailed):
+                # Correctly unhelifiable value, but not for verifying the
+                # session
+                self.auth_backend._verify_session("abc12")
+
+        d.addCallback(wrapper)
+
+        return d
+
+    @deferred()
+    def test_verify_session_fails_on_no_session_id(self):
+        d = self._prepare_verify_session()
+
+        def wrapper(M2):
+            self.auth_backend._session.cookies.get = MagicMock(
+                return_value=None)
+            with self.assertRaises(srpauth.SRPAuthNoSessionId):
+                self.auth_backend._verify_session(M2)
+
+        d.addCallback(wrapper)
+
+        return d
+
+    @deferred()
+    def test_verify_session_session_id(self):
+        d = self._prepare_verify_session()
+
+        test_session_id = "12345"
+
+        def wrapper(M2):
+            self.auth_backend._session.cookies.get = MagicMock(
+                return_value=test_session_id)
+            self.auth_backend._verify_session(M2)
+            self.assertEqual(self.auth_backend.get_session_id(),
+                             test_session_id)
+            self.assertEqual(self.auth_backend.get_session_id(),
+                             self.auth.get_session_id())
+
+        d.addCallback(wrapper)
+
+        return d
+
+    @deferred()
+    def test_verify_session(self):
+        d = self._prepare_verify_session()
+
+        def wrapper(M2):
+            self.auth_backend._verify_session(M2)
+
+        d.addCallback(wrapper)
+
+        return d
+
+    @deferred()
+    def test_authenticate(self):
+        self.auth_backend._authentication_preprocessing = MagicMock(
+            return_value=None)
+        self.auth_backend._start_authentication = MagicMock(return_value=None)
+        self.auth_backend._process_challenge = MagicMock(return_value=None)
+        self.auth_backend._extract_data = MagicMock(return_value=None)
+        self.auth_backend._verify_session = MagicMock(return_value=None)
+
+        d = self.auth_backend.authenticate(self.TEST_USER, self.TEST_PASS)
+
+        def check(*args):
+            self.auth_backend._authentication_preprocessing.\
+                assert_called_once_with(
+                    username=self.TEST_USER,
+                    password=self.TEST_PASS
+                )
+            self.auth_backend._start_authentication.assert_called_once_with(
+                None,
+                username=self.TEST_USER)
+            self.auth_backend._process_challenge.assert_called_once_with(
+                None,
+                username=self.TEST_USER)
+            self.auth_backend._extract_data.assert_called_once_with(
+                None,
+                username=self.TEST_USER)
+            self.auth_backend._verify_session.assert_called_once_with(None)
+
+        d.addCallback(check)
+
+        return d
+
+    @deferred()
+    def test_logout_fails_if_not_logged_in(self):
+
+        def wrapper(*args):
+            with self.assertRaises(AssertionError):
+                self.auth_backend.logout()
+
+        d = threads.deferToThread(wrapper)
+        return d
+
+    @deferred()
+    def test_logout_traps_delete(self):
+        self.auth_backend.get_session_id = MagicMock(return_value="1234")
+        self.auth_backend._session.delete = MagicMock(side_effect=Exception())
+
+        def wrapper(*args):
+            self.auth_backend.logout()
+
+        d = threads.deferToThread(wrapper)
+        return d
+
+    @deferred()
+    def test_logout_clears(self):
+        self.auth_backend._session_id = "1234"
+
+        def wrapper(*args):
+            old_session = self.auth_backend._session
+            self.auth_backend.logout()
+            self.assertIsNone(self.auth_backend.get_session_id())
+            self.assertIsNone(self.auth_backend.get_uid())
+            self.assertNotEqual(old_session, self.auth_backend._session)
+
+        d = threads.deferToThread(wrapper)
+        return d
+
+
+class SRPAuthSingletonTestCase(unittest.TestCase):
+    def setUp(self):
+        self.old_auth = srpauth.SRPAuth._SRPAuth__impl.authenticate
+
+    def tearDown(self):
+        srpauth.SRPAuth._SRPAuth__impl.authenticate = self.old_auth
+
+    def test_singleton(self):
+        obj1 = srpauth.SRPAuth(ProviderConfig())
+        obj2 = srpauth.SRPAuth(ProviderConfig())
+        self.assertEqual(obj1._SRPAuth__instance, obj2._SRPAuth__instance)
+
+    @deferred()
+    def test_authenticate_notifies_gui(self):
+        auth = srpauth.SRPAuth(ProviderConfig())
+        auth._SRPAuth__instance.authenticate = MagicMock(
+            return_value=threads.deferToThread(lambda: None))
+        auth._gui_notify = MagicMock()
+
+        d = auth.authenticate("", "")
+
+        def check(*args):
+            auth._gui_notify.assert_called_once_with(None)
+
+        d.addCallback(check)
+        return d
+
+    @deferred()
+    def test_authenticate_errsback(self):
+        auth = srpauth.SRPAuth(ProviderConfig())
+        auth._SRPAuth__instance.authenticate = MagicMock(
+            return_value=threads.deferToThread(MagicMock(
+                side_effect=Exception())))
+        auth._gui_notify = MagicMock()
+        auth._errback = MagicMock()
+
+        d = auth.authenticate("", "")
+
+        def check(*args):
+            self.assertFalse(auth._gui_notify.called)
+            self.assertEqual(auth._errback.call_count, 1)
+
+        d.addCallback(check)
+        return d
+
+    @deferred()
+    def test_authenticate_runs_cleanly_when_raises(self):
+        auth = srpauth.SRPAuth(ProviderConfig())
+        auth._SRPAuth__instance.authenticate = MagicMock(
+            return_value=threads.deferToThread(MagicMock(
+                side_effect=Exception())))
+
+        d = auth.authenticate("", "")
+
+        return d
+
+    @deferred()
+    def test_authenticate_runs_cleanly(self):
+        auth = srpauth.SRPAuth(ProviderConfig())
+        auth._SRPAuth__instance.authenticate = MagicMock(
+            return_value=threads.deferToThread(MagicMock()))
+
+        d = auth.authenticate("", "")
+
+        return d
+
+    def test_logout(self):
+        auth = srpauth.SRPAuth(ProviderConfig())
+        auth._SRPAuth__instance.logout = MagicMock()
+
+        self.assertTrue(auth.logout())
+
+    def test_logout_rets_false_when_raises(self):
+        auth = srpauth.SRPAuth(ProviderConfig())
+        auth._SRPAuth__instance.logout = MagicMock(
+            side_effect=Exception())
+
+        self.assertFalse(auth.logout())