Refactor the user-interactive auth handling (#6105)

Pull the checkers out to their own classes, rather than having them lost in a
massive 1000-line class which does everything.

This is also preparation for some more intelligent advertising of flows, as per #6100

3 files changed, 248 insertions, 131 deletions

diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 374372b69e..f920c2f6c1 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -21,10 +21,8 @@ import unicodedata
 import attr
 import bcrypt
 import pymacaroons
-from canonicaljson import json
 
 from twisted.internet import defer
-from twisted.web.client import PartialDownloadError
 
 import synapse.util.stringutils as stringutils
 from synapse.api.constants import LoginType
@@ -38,7 +36,8 @@ from synapse.api.errors import (
     UserDeactivatedError,
 )
 from synapse.api.ratelimiting import Ratelimiter
-from synapse.config.emailconfig import ThreepidBehaviour
+from synapse.handlers.ui_auth import INTERACTIVE_AUTH_CHECKERS
+from synapse.handlers.ui_auth.checkers import UserInteractiveAuthChecker
 from synapse.logging.context import defer_to_thread
 from synapse.module_api import ModuleApi
 from synapse.types import UserID
@@ -58,13 +57,12 @@ class AuthHandler(BaseHandler):
             hs (synapse.server.HomeServer):
         """
         super(AuthHandler, self).__init__(hs)
-        self.checkers = {
-            LoginType.RECAPTCHA: self._check_recaptcha,
-            LoginType.EMAIL_IDENTITY: self._check_email_identity,
-            LoginType.MSISDN: self._check_msisdn,
-            LoginType.DUMMY: self._check_dummy_auth,
-            LoginType.TERMS: self._check_terms_auth,
-        }
+
+        self.checkers = {}  # type: dict[str, UserInteractiveAuthChecker]
+        for auth_checker_class in INTERACTIVE_AUTH_CHECKERS:
+            inst = auth_checker_class(hs)
+            self.checkers[inst.AUTH_TYPE] = inst
+
         self.bcrypt_rounds = hs.config.bcrypt_rounds
 
         # This is not a cache per se, but a store of all current sessions that
@@ -292,7 +290,7 @@ class AuthHandler(BaseHandler):
             sess["creds"] = {}
         creds = sess["creds"]
 
-        result = yield self.checkers[stagetype](authdict, clientip)
+        result = yield self.checkers[stagetype].check_auth(authdict, clientip)
         if result:
             creds[stagetype] = result
             self._save_session(sess)
@@ -363,7 +361,7 @@ class AuthHandler(BaseHandler):
         login_type = authdict["type"]
         checker = self.checkers.get(login_type)
         if checker is not None:
-            res = yield checker(authdict, clientip=clientip)
+            res = yield checker.check_auth(authdict, clientip=clientip)
             return res
 
         # build a v1-login-style dict out of the authdict and fall back to the
@@ -376,125 +374,6 @@ class AuthHandler(BaseHandler):
         (canonical_id, callback) = yield self.validate_login(user_id, authdict)
         return canonical_id
 
-    @defer.inlineCallbacks
-    def _check_recaptcha(self, authdict, clientip, **kwargs):
-        try:
-            user_response = authdict["response"]
-        except KeyError:
-            # Client tried to provide captcha but didn't give the parameter:
-            # bad request.
-            raise LoginError(
-                400, "Captcha response is required", errcode=Codes.CAPTCHA_NEEDED
-            )
-
-        logger.info(
-            "Submitting recaptcha response %s with remoteip %s", user_response, clientip
-        )
-
-        # TODO: get this from the homeserver rather than creating a new one for
-        # each request
-        try:
-            client = self.hs.get_simple_http_client()
-            resp_body = yield client.post_urlencoded_get_json(
-                self.hs.config.recaptcha_siteverify_api,
-                args={
-                    "secret": self.hs.config.recaptcha_private_key,
-                    "response": user_response,
-                    "remoteip": clientip,
-                },
-            )
-        except PartialDownloadError as pde:
-            # Twisted is silly
-            data = pde.response
-            resp_body = json.loads(data)
-
-        if "success" in resp_body:
-            # Note that we do NOT check the hostname here: we explicitly
-            # intend the CAPTCHA to be presented by whatever client the
-            # user is using, we just care that they have completed a CAPTCHA.
-            logger.info(
-                "%s reCAPTCHA from hostname %s",
-                "Successful" if resp_body["success"] else "Failed",
-                resp_body.get("hostname"),
-            )
-            if resp_body["success"]:
-                return True
-        raise LoginError(401, "", errcode=Codes.UNAUTHORIZED)
-
-    def _check_email_identity(self, authdict, **kwargs):
-        return self._check_threepid("email", authdict, **kwargs)
-
-    def _check_msisdn(self, authdict, **kwargs):
-        return self._check_threepid("msisdn", authdict)
-
-    def _check_dummy_auth(self, authdict, **kwargs):
-        return defer.succeed(True)
-
-    def _check_terms_auth(self, authdict, **kwargs):
-        return defer.succeed(True)
-
-    @defer.inlineCallbacks
-    def _check_threepid(self, medium, authdict, **kwargs):
-        if "threepid_creds" not in authdict:
-            raise LoginError(400, "Missing threepid_creds", Codes.MISSING_PARAM)
-
-        threepid_creds = authdict["threepid_creds"]
-
-        identity_handler = self.hs.get_handlers().identity_handler
-
-        logger.info("Getting validated threepid. threepidcreds: %r", (threepid_creds,))
-        if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
-            if medium == "email":
-                threepid = yield identity_handler.threepid_from_creds(
-                    self.hs.config.account_threepid_delegate_email, threepid_creds
-                )
-            elif medium == "msisdn":
-                threepid = yield identity_handler.threepid_from_creds(
-                    self.hs.config.account_threepid_delegate_msisdn, threepid_creds
-                )
-            else:
-                raise SynapseError(400, "Unrecognized threepid medium: %s" % (medium,))
-        elif self.hs.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
-            row = yield self.store.get_threepid_validation_session(
-                medium,
-                threepid_creds["client_secret"],
-                sid=threepid_creds["sid"],
-                validated=True,
-            )
-
-            threepid = (
-                {
-                    "medium": row["medium"],
-                    "address": row["address"],
-                    "validated_at": row["validated_at"],
-                }
-                if row
-                else None
-            )
-
-            if row:
-                # Valid threepid returned, delete from the db
-                yield self.store.delete_threepid_session(threepid_creds["sid"])
-        else:
-            raise SynapseError(
-                400, "Password resets are not enabled on this homeserver"
-            )
-
-        if not threepid:
-            raise LoginError(401, "", errcode=Codes.UNAUTHORIZED)
-
-        if threepid["medium"] != medium:
-            raise LoginError(
-                401,
-                "Expecting threepid of type '%s', got '%s'"
-                % (medium, threepid["medium"]),
-                errcode=Codes.UNAUTHORIZED,
-            )
-
-        threepid["threepid_creds"] = authdict["threepid_creds"]
-
-        return threepid
-
     def _get_params_recaptcha(self):
         return {"public_key": self.hs.config.recaptcha_public_key}
 
diff --git a/synapse/handlers/ui_auth/__init__.py b/synapse/handlers/ui_auth/__init__.py
new file mode 100644
index 0000000000..824f37f8f8
--- /dev/null
+++ b/synapse/handlers/ui_auth/__init__.py
@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""This module implements user-interactive auth verification.
+
+TODO: move more stuff out of AuthHandler in here.
+
+"""
+
+from synapse.handlers.ui_auth.checkers import INTERACTIVE_AUTH_CHECKERS  # noqa: F401
diff --git a/synapse/handlers/ui_auth/checkers.py b/synapse/handlers/ui_auth/checkers.py
new file mode 100644
index 0000000000..fd633b7b0e
--- /dev/null
+++ b/synapse/handlers/ui_auth/checkers.py
@@ -0,0 +1,216 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+
+from canonicaljson import json
+
+from twisted.internet import defer
+from twisted.web.client import PartialDownloadError
+
+from synapse.api.constants import LoginType
+from synapse.api.errors import Codes, LoginError, SynapseError
+from synapse.config.emailconfig import ThreepidBehaviour
+
+logger = logging.getLogger(__name__)
+
+
+class UserInteractiveAuthChecker:
+    """Abstract base class for an interactive auth checker"""
+
+    def __init__(self, hs):
+        pass
+
+    def check_auth(self, authdict, clientip):
+        """Given the authentication dict from the client, attempt to check this step
+
+        Args:
+            authdict (dict): authentication dictionary from the client
+            clientip (str): The IP address of the client.
+
+        Raises:
+            SynapseError if authentication failed
+
+        Returns:
+            Deferred: the result of authentication (to pass back to the client?)
+        """
+        raise NotImplementedError()
+
+
+class DummyAuthChecker(UserInteractiveAuthChecker):
+    AUTH_TYPE = LoginType.DUMMY
+
+    def check_auth(self, authdict, clientip):
+        return defer.succeed(True)
+
+
+class TermsAuthChecker(UserInteractiveAuthChecker):
+    AUTH_TYPE = LoginType.TERMS
+
+    def check_auth(self, authdict, clientip):
+        return defer.succeed(True)
+
+
+class RecaptchaAuthChecker(UserInteractiveAuthChecker):
+    AUTH_TYPE = LoginType.RECAPTCHA
+
+    def __init__(self, hs):
+        super().__init__(hs)
+        self._http_client = hs.get_simple_http_client()
+        self._url = hs.config.recaptcha_siteverify_api
+        self._secret = hs.config.recaptcha_private_key
+
+    @defer.inlineCallbacks
+    def check_auth(self, authdict, clientip):
+        try:
+            user_response = authdict["response"]
+        except KeyError:
+            # Client tried to provide captcha but didn't give the parameter:
+            # bad request.
+            raise LoginError(
+                400, "Captcha response is required", errcode=Codes.CAPTCHA_NEEDED
+            )
+
+        logger.info(
+            "Submitting recaptcha response %s with remoteip %s", user_response, clientip
+        )
+
+        # TODO: get this from the homeserver rather than creating a new one for
+        # each request
+        try:
+            resp_body = yield self._http_client.post_urlencoded_get_json(
+                self._url,
+                args={
+                    "secret": self._secret,
+                    "response": user_response,
+                    "remoteip": clientip,
+                },
+            )
+        except PartialDownloadError as pde:
+            # Twisted is silly
+            data = pde.response
+            resp_body = json.loads(data)
+
+        if "success" in resp_body:
+            # Note that we do NOT check the hostname here: we explicitly
+            # intend the CAPTCHA to be presented by whatever client the
+            # user is using, we just care that they have completed a CAPTCHA.
+            logger.info(
+                "%s reCAPTCHA from hostname %s",
+                "Successful" if resp_body["success"] else "Failed",
+                resp_body.get("hostname"),
+            )
+            if resp_body["success"]:
+                return True
+        raise LoginError(401, "", errcode=Codes.UNAUTHORIZED)
+
+
+class _BaseThreepidAuthChecker:
+    def __init__(self, hs):
+        self.hs = hs
+        self.store = hs.get_datastore()
+
+    @defer.inlineCallbacks
+    def _check_threepid(self, medium, authdict):
+        if "threepid_creds" not in authdict:
+            raise LoginError(400, "Missing threepid_creds", Codes.MISSING_PARAM)
+
+        threepid_creds = authdict["threepid_creds"]
+
+        identity_handler = self.hs.get_handlers().identity_handler
+
+        logger.info("Getting validated threepid. threepidcreds: %r", (threepid_creds,))
+        if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
+            if medium == "email":
+                threepid = yield identity_handler.threepid_from_creds(
+                    self.hs.config.account_threepid_delegate_email, threepid_creds
+                )
+            elif medium == "msisdn":
+                threepid = yield identity_handler.threepid_from_creds(
+                    self.hs.config.account_threepid_delegate_msisdn, threepid_creds
+                )
+            else:
+                raise SynapseError(400, "Unrecognized threepid medium: %s" % (medium,))
+        elif self.hs.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
+            row = yield self.store.get_threepid_validation_session(
+                medium,
+                threepid_creds["client_secret"],
+                sid=threepid_creds["sid"],
+                validated=True,
+            )
+
+            threepid = (
+                {
+                    "medium": row["medium"],
+                    "address": row["address"],
+                    "validated_at": row["validated_at"],
+                }
+                if row
+                else None
+            )
+
+            if row:
+                # Valid threepid returned, delete from the db
+                yield self.store.delete_threepid_session(threepid_creds["sid"])
+        else:
+            raise SynapseError(
+                400, "Password resets are not enabled on this homeserver"
+            )
+
+        if not threepid:
+            raise LoginError(401, "", errcode=Codes.UNAUTHORIZED)
+
+        if threepid["medium"] != medium:
+            raise LoginError(
+                401,
+                "Expecting threepid of type '%s', got '%s'"
+                % (medium, threepid["medium"]),
+                errcode=Codes.UNAUTHORIZED,
+            )
+
+        threepid["threepid_creds"] = authdict["threepid_creds"]
+
+        return threepid
+
+
+class EmailIdentityAuthChecker(UserInteractiveAuthChecker, _BaseThreepidAuthChecker):
+    AUTH_TYPE = LoginType.EMAIL_IDENTITY
+
+    def __init__(self, hs):
+        UserInteractiveAuthChecker.__init__(self, hs)
+        _BaseThreepidAuthChecker.__init__(self, hs)
+
+    def check_auth(self, authdict, clientip):
+        return self._check_threepid("email", authdict)
+
+
+class MsisdnAuthChecker(UserInteractiveAuthChecker, _BaseThreepidAuthChecker):
+    AUTH_TYPE = LoginType.MSISDN
+
+    def __init__(self, hs):
+        UserInteractiveAuthChecker.__init__(self, hs)
+        _BaseThreepidAuthChecker.__init__(self, hs)
+
+    def check_auth(self, authdict, clientip):
+        return self._check_threepid("msisdn", authdict)
+
+
+INTERACTIVE_AUTH_CHECKERS = [
+    DummyAuthChecker,
+    TermsAuthChecker,
+    RecaptchaAuthChecker,
+    EmailIdentityAuthChecker,
+    MsisdnAuthChecker,
+]
+"""A list of UserInteractiveAuthChecker classes"""