Flatten the synapse.rest.client package (#10600)

synapse/rest/client/register.py

@@ -0,0 +1,879 @@
+# Copyright 2015 - 2016 OpenMarket Ltd
+# Copyright 2017 Vector Creations Ltd
+#
+# 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 hmac
+import logging
+import random
+from typing import List, Union
+
+import synapse
+import synapse.api.auth
+import synapse.types
+from synapse.api.constants import APP_SERVICE_REGISTRATION_TYPE, LoginType
+from synapse.api.errors import (
+    Codes,
+    InteractiveAuthIncompleteError,
+    SynapseError,
+    ThreepidValidationError,
+    UnrecognizedRequestError,
+)
+from synapse.config import ConfigError
+from synapse.config.captcha import CaptchaConfig
+from synapse.config.consent import ConsentConfig
+from synapse.config.emailconfig import ThreepidBehaviour
+from synapse.config.ratelimiting import FederationRateLimitConfig
+from synapse.config.registration import RegistrationConfig
+from synapse.config.server import is_threepid_reserved
+from synapse.handlers.auth import AuthHandler
+from synapse.handlers.ui_auth import UIAuthSessionDataConstants
+from synapse.http.server import finish_request, respond_with_html
+from synapse.http.servlet import (
+    RestServlet,
+    assert_params_in_dict,
+    parse_boolean,
+    parse_json_object_from_request,
+    parse_string,
+)
+from synapse.metrics import threepid_send_requests
+from synapse.push.mailer import Mailer
+from synapse.types import JsonDict
+from synapse.util.msisdn import phone_number_to_msisdn
+from synapse.util.ratelimitutils import FederationRateLimiter
+from synapse.util.stringutils import assert_valid_client_secret, random_string
+from synapse.util.threepids import (
+    canonicalise_email,
+    check_3pid_allowed,
+    validate_email,
+)
+
+from ._base import client_patterns, interactive_auth_handler
+
+# We ought to be using hmac.compare_digest() but on older pythons it doesn't
+# exist. It's a _really minor_ security flaw to use plain string comparison
+# because the timing attack is so obscured by all the other code here it's
+# unlikely to make much difference
+if hasattr(hmac, "compare_digest"):
+    compare_digest = hmac.compare_digest
+else:
+
+    def compare_digest(a, b):
+        return a == b
+
+
+logger = logging.getLogger(__name__)
+
+
+class EmailRegisterRequestTokenRestServlet(RestServlet):
+    PATTERNS = client_patterns("/register/email/requestToken$")
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        super().__init__()
+        self.hs = hs
+        self.identity_handler = hs.get_identity_handler()
+        self.config = hs.config
+
+        if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
+            self.mailer = Mailer(
+                hs=self.hs,
+                app_name=self.config.email_app_name,
+                template_html=self.config.email_registration_template_html,
+                template_text=self.config.email_registration_template_text,
+            )
+
+    async def on_POST(self, request):
+        if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.OFF:
+            if self.hs.config.local_threepid_handling_disabled_due_to_email_config:
+                logger.warning(
+                    "Email registration has been disabled due to lack of email config"
+                )
+            raise SynapseError(
+                400, "Email-based registration has been disabled on this server"
+            )
+        body = parse_json_object_from_request(request)
+
+        assert_params_in_dict(body, ["client_secret", "email", "send_attempt"])
+
+        # Extract params from body
+        client_secret = body["client_secret"]
+        assert_valid_client_secret(client_secret)
+
+        # For emails, canonicalise the address.
+        # We store all email addresses canonicalised in the DB.
+        # (See on_POST in EmailThreepidRequestTokenRestServlet
+        # in synapse/rest/client/account.py)
+        try:
+            email = validate_email(body["email"])
+        except ValueError as e:
+            raise SynapseError(400, str(e))
+        send_attempt = body["send_attempt"]
+        next_link = body.get("next_link")  # Optional param
+
+        if not check_3pid_allowed(self.hs, "email", email):
+            raise SynapseError(
+                403,
+                "Your email domain is not authorized to register on this server",
+                Codes.THREEPID_DENIED,
+            )
+
+        await self.identity_handler.ratelimit_request_token_requests(
+            request, "email", email
+        )
+
+        existing_user_id = await self.hs.get_datastore().get_user_id_by_threepid(
+            "email", email
+        )
+
+        if existing_user_id is not None:
+            if self.hs.config.request_token_inhibit_3pid_errors:
+                # Make the client think the operation succeeded. See the rationale in the
+                # comments for request_token_inhibit_3pid_errors.
+                # Also wait for some random amount of time between 100ms and 1s to make it
+                # look like we did something.
+                await self.hs.get_clock().sleep(random.randint(1, 10) / 10)
+                return 200, {"sid": random_string(16)}
+
+            raise SynapseError(400, "Email is already in use", Codes.THREEPID_IN_USE)
+
+        if self.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE:
+            assert self.hs.config.account_threepid_delegate_email
+
+            # Have the configured identity server handle the request
+            ret = await self.identity_handler.requestEmailToken(
+                self.hs.config.account_threepid_delegate_email,
+                email,
+                client_secret,
+                send_attempt,
+                next_link,
+            )
+        else:
+            # Send registration emails from Synapse
+            sid = await self.identity_handler.send_threepid_validation(
+                email,
+                client_secret,
+                send_attempt,
+                self.mailer.send_registration_mail,
+                next_link,
+            )
+
+            # Wrap the session id in a JSON object
+            ret = {"sid": sid}
+
+        threepid_send_requests.labels(type="email", reason="register").observe(
+            send_attempt
+        )
+
+        return 200, ret
+
+
+class MsisdnRegisterRequestTokenRestServlet(RestServlet):
+    PATTERNS = client_patterns("/register/msisdn/requestToken$")
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        super().__init__()
+        self.hs = hs
+        self.identity_handler = hs.get_identity_handler()
+
+    async def on_POST(self, request):
+        body = parse_json_object_from_request(request)
+
+        assert_params_in_dict(
+            body, ["client_secret", "country", "phone_number", "send_attempt"]
+        )
+        client_secret = body["client_secret"]
+        assert_valid_client_secret(client_secret)
+        country = body["country"]
+        phone_number = body["phone_number"]
+        send_attempt = body["send_attempt"]
+        next_link = body.get("next_link")  # Optional param
+
+        msisdn = phone_number_to_msisdn(country, phone_number)
+
+        if not check_3pid_allowed(self.hs, "msisdn", msisdn):
+            raise SynapseError(
+                403,
+                "Phone numbers are not authorized to register on this server",
+                Codes.THREEPID_DENIED,
+            )
+
+        await self.identity_handler.ratelimit_request_token_requests(
+            request, "msisdn", msisdn
+        )
+
+        existing_user_id = await self.hs.get_datastore().get_user_id_by_threepid(
+            "msisdn", msisdn
+        )
+
+        if existing_user_id is not None:
+            if self.hs.config.request_token_inhibit_3pid_errors:
+                # Make the client think the operation succeeded. See the rationale in the
+                # comments for request_token_inhibit_3pid_errors.
+                # Also wait for some random amount of time between 100ms and 1s to make it
+                # look like we did something.
+                await self.hs.get_clock().sleep(random.randint(1, 10) / 10)
+                return 200, {"sid": random_string(16)}
+
+            raise SynapseError(
+                400, "Phone number is already in use", Codes.THREEPID_IN_USE
+            )
+
+        if not self.hs.config.account_threepid_delegate_msisdn:
+            logger.warning(
+                "No upstream msisdn account_threepid_delegate configured on the server to "
+                "handle this request"
+            )
+            raise SynapseError(
+                400, "Registration by phone number is not supported on this homeserver"
+            )
+
+        ret = await self.identity_handler.requestMsisdnToken(
+            self.hs.config.account_threepid_delegate_msisdn,
+            country,
+            phone_number,
+            client_secret,
+            send_attempt,
+            next_link,
+        )
+
+        threepid_send_requests.labels(type="msisdn", reason="register").observe(
+            send_attempt
+        )
+
+        return 200, ret
+
+
+class RegistrationSubmitTokenServlet(RestServlet):
+    """Handles registration 3PID validation token submission"""
+
+    PATTERNS = client_patterns(
+        "/registration/(?P<medium>[^/]*)/submit_token$", releases=(), unstable=True
+    )
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        super().__init__()
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.config = hs.config
+        self.clock = hs.get_clock()
+        self.store = hs.get_datastore()
+
+        if self.config.threepid_behaviour_email == ThreepidBehaviour.LOCAL:
+            self._failure_email_template = (
+                self.config.email_registration_template_failure_html
+            )
+
+    async def on_GET(self, request, medium):
+        if medium != "email":
+            raise SynapseError(
+                400, "This medium is currently not supported for registration"
+            )
+        if self.config.threepid_behaviour_email == ThreepidBehaviour.OFF:
+            if self.config.local_threepid_handling_disabled_due_to_email_config:
+                logger.warning(
+                    "User registration via email has been disabled due to lack of email config"
+                )
+            raise SynapseError(
+                400, "Email-based registration is disabled on this server"
+            )
+
+        sid = parse_string(request, "sid", required=True)
+        client_secret = parse_string(request, "client_secret", required=True)
+        assert_valid_client_secret(client_secret)
+        token = parse_string(request, "token", required=True)
+
+        # Attempt to validate a 3PID session
+        try:
+            # Mark the session as valid
+            next_link = await self.store.validate_threepid_session(
+                sid, client_secret, token, self.clock.time_msec()
+            )
+
+            # Perform a 302 redirect if next_link is set
+            if next_link:
+                if next_link.startswith("file:///"):
+                    logger.warning(
+                        "Not redirecting to next_link as it is a local file: address"
+                    )
+                else:
+                    request.setResponseCode(302)
+                    request.setHeader("Location", next_link)
+                    finish_request(request)
+                    return None
+
+            # Otherwise show the success template
+            html = self.config.email_registration_template_success_html_content
+            status_code = 200
+        except ThreepidValidationError as e:
+            status_code = e.code
+
+            # Show a failure page with a reason
+            template_vars = {"failure_reason": e.msg}
+            html = self._failure_email_template.render(**template_vars)
+
+        respond_with_html(request, status_code, html)
+
+
+class UsernameAvailabilityRestServlet(RestServlet):
+    PATTERNS = client_patterns("/register/available")
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        super().__init__()
+        self.hs = hs
+        self.registration_handler = hs.get_registration_handler()
+        self.ratelimiter = FederationRateLimiter(
+            hs.get_clock(),
+            FederationRateLimitConfig(
+                # Time window of 2s
+                window_size=2000,
+                # Artificially delay requests if rate > sleep_limit/window_size
+                sleep_limit=1,
+                # Amount of artificial delay to apply
+                sleep_msec=1000,
+                # Error with 429 if more than reject_limit requests are queued
+                reject_limit=1,
+                # Allow 1 request at a time
+                concurrent_requests=1,
+            ),
+        )
+
+    async def on_GET(self, request):
+        if not self.hs.config.enable_registration:
+            raise SynapseError(
+                403, "Registration has been disabled", errcode=Codes.FORBIDDEN
+            )
+
+        ip = request.getClientIP()
+        with self.ratelimiter.ratelimit(ip) as wait_deferred:
+            await wait_deferred
+
+            username = parse_string(request, "username", required=True)
+
+            await self.registration_handler.check_username(username)
+
+            return 200, {"available": True}
+
+
+class RegisterRestServlet(RestServlet):
+    PATTERNS = client_patterns("/register$")
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        super().__init__()
+
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+        self.auth_handler = hs.get_auth_handler()
+        self.registration_handler = hs.get_registration_handler()
+        self.identity_handler = hs.get_identity_handler()
+        self.room_member_handler = hs.get_room_member_handler()
+        self.macaroon_gen = hs.get_macaroon_generator()
+        self.ratelimiter = hs.get_registration_ratelimiter()
+        self.password_policy_handler = hs.get_password_policy_handler()
+        self.clock = hs.get_clock()
+        self._registration_enabled = self.hs.config.enable_registration
+        self._msc2918_enabled = hs.config.access_token_lifetime is not None
+
+        self._registration_flows = _calculate_registration_flows(
+            hs.config, self.auth_handler
+        )
+
+    @interactive_auth_handler
+    async def on_POST(self, request):
+        body = parse_json_object_from_request(request)
+
+        client_addr = request.getClientIP()
+
+        await self.ratelimiter.ratelimit(None, client_addr, update=False)
+
+        kind = b"user"
+        if b"kind" in request.args:
+            kind = request.args[b"kind"][0]
+
+        if kind == b"guest":
+            ret = await self._do_guest_registration(body, address=client_addr)
+            return ret
+        elif kind != b"user":
+            raise UnrecognizedRequestError(
+                "Do not understand membership kind: %s" % (kind.decode("utf8"),)
+            )
+
+        if self._msc2918_enabled:
+            # Check if this registration should also issue a refresh token, as
+            # per MSC2918
+            should_issue_refresh_token = parse_boolean(
+                request, name="org.matrix.msc2918.refresh_token", default=False
+            )
+        else:
+            should_issue_refresh_token = False
+
+        # Pull out the provided username and do basic sanity checks early since
+        # the auth layer will store these in sessions.
+        desired_username = None
+        if "username" in body:
+            if not isinstance(body["username"], str) or len(body["username"]) > 512:
+                raise SynapseError(400, "Invalid username")
+            desired_username = body["username"]
+
+        # fork off as soon as possible for ASes which have completely
+        # different registration flows to normal users
+
+        # == Application Service Registration ==
+        if body.get("type") == APP_SERVICE_REGISTRATION_TYPE:
+            if not self.auth.has_access_token(request):
+                raise SynapseError(
+                    400,
+                    "Appservice token must be provided when using a type of m.login.application_service",
+                )
+
+            # Verify the AS
+            self.auth.get_appservice_by_req(request)
+
+            # Set the desired user according to the AS API (which uses the
+            # 'user' key not 'username'). Since this is a new addition, we'll
+            # fallback to 'username' if they gave one.
+            desired_username = body.get("user", desired_username)
+
+            # XXX we should check that desired_username is valid. Currently
+            # we give appservices carte blanche for any insanity in mxids,
+            # because the IRC bridges rely on being able to register stupid
+            # IDs.
+
+            access_token = self.auth.get_access_token_from_request(request)
+
+            if not isinstance(desired_username, str):
+                raise SynapseError(400, "Desired Username is missing or not a string")
+
+            result = await self._do_appservice_registration(
+                desired_username,
+                access_token,
+                body,
+                should_issue_refresh_token=should_issue_refresh_token,
+            )
+
+            return 200, result
+        elif self.auth.has_access_token(request):
+            raise SynapseError(
+                400,
+                "An access token should not be provided on requests to /register (except if type is m.login.application_service)",
+            )
+
+        # == Normal User Registration == (everyone else)
+        if not self._registration_enabled:
+            raise SynapseError(403, "Registration has been disabled", Codes.FORBIDDEN)
+
+        # For regular registration, convert the provided username to lowercase
+        # before attempting to register it. This should mean that people who try
+        # to register with upper-case in their usernames don't get a nasty surprise.
+        #
+        # Note that we treat usernames case-insensitively in login, so they are
+        # free to carry on imagining that their username is CrAzYh4cKeR if that
+        # keeps them happy.
+        if desired_username is not None:
+            desired_username = desired_username.lower()
+
+        # Check if this account is upgrading from a guest account.
+        guest_access_token = body.get("guest_access_token", None)
+
+        # Pull out the provided password and do basic sanity checks early.
+        #
+        # Note that we remove the password from the body since the auth layer
+        # will store the body in the session and we don't want a plaintext
+        # password store there.
+        password = body.pop("password", None)
+        if password is not None:
+            if not isinstance(password, str) or len(password) > 512:
+                raise SynapseError(400, "Invalid password")
+            self.password_policy_handler.validate_password(password)
+
+        if "initial_device_display_name" in body and password is None:
+            # ignore 'initial_device_display_name' if sent without
+            # a password to work around a client bug where it sent
+            # the 'initial_device_display_name' param alone, wiping out
+            # the original registration params
+            logger.warning("Ignoring initial_device_display_name without password")
+            del body["initial_device_display_name"]
+
+        session_id = self.auth_handler.get_session_id(body)
+        registered_user_id = None
+        password_hash = None
+        if session_id:
+            # if we get a registered user id out of here, it means we previously
+            # registered a user for this session, so we could just return the
+            # user here. We carry on and go through the auth checks though,
+            # for paranoia.
+            registered_user_id = await self.auth_handler.get_session_data(
+                session_id, UIAuthSessionDataConstants.REGISTERED_USER_ID, None
+            )
+            # Extract the previously-hashed password from the session.
+            password_hash = await self.auth_handler.get_session_data(
+                session_id, UIAuthSessionDataConstants.PASSWORD_HASH, None
+            )
+
+        # Ensure that the username is valid.
+        if desired_username is not None:
+            await self.registration_handler.check_username(
+                desired_username,
+                guest_access_token=guest_access_token,
+                assigned_user_id=registered_user_id,
+            )
+
+        # Check if the user-interactive authentication flows are complete, if
+        # not this will raise a user-interactive auth error.
+        try:
+            auth_result, params, session_id = await self.auth_handler.check_ui_auth(
+                self._registration_flows,
+                request,
+                body,
+                "register a new account",
+            )
+        except InteractiveAuthIncompleteError as e:
+            # The user needs to provide more steps to complete auth.
+            #
+            # Hash the password and store it with the session since the client
+            # is not required to provide the password again.
+            #
+            # If a password hash was previously stored we will not attempt to
+            # re-hash and store it for efficiency. This assumes the password
+            # does not change throughout the authentication flow, but this
+            # should be fine since the data is meant to be consistent.
+            if not password_hash and password:
+                password_hash = await self.auth_handler.hash(password)
+                await self.auth_handler.set_session_data(
+                    e.session_id,
+                    UIAuthSessionDataConstants.PASSWORD_HASH,
+                    password_hash,
+                )
+            raise
+
+        # Check that we're not trying to register a denied 3pid.
+        #
+        # the user-facing checks will probably already have happened in
+        # /register/email/requestToken when we requested a 3pid, but that's not
+        # guaranteed.
+        if auth_result:
+            for login_type in [LoginType.EMAIL_IDENTITY, LoginType.MSISDN]:
+                if login_type in auth_result:
+                    medium = auth_result[login_type]["medium"]
+                    address = auth_result[login_type]["address"]
+
+                    if not check_3pid_allowed(self.hs, medium, address):
+                        raise SynapseError(
+                            403,
+                            "Third party identifiers (email/phone numbers)"
+                            + " are not authorized on this server",
+                            Codes.THREEPID_DENIED,
+                        )
+
+        if registered_user_id is not None:
+            logger.info(
+                "Already registered user ID %r for this session", registered_user_id
+            )
+            # don't re-register the threepids
+            registered = False
+        else:
+            # If we have a password in this request, prefer it. Otherwise, there
+            # might be a password hash from an earlier request.
+            if password:
+                password_hash = await self.auth_handler.hash(password)
+            if not password_hash:
+                raise SynapseError(400, "Missing params: password", Codes.MISSING_PARAM)
+
+            desired_username = params.get("username", None)
+            guest_access_token = params.get("guest_access_token", None)
+
+            if desired_username is not None:
+                desired_username = desired_username.lower()
+
+            threepid = None
+            if auth_result:
+                threepid = auth_result.get(LoginType.EMAIL_IDENTITY)
+
+                # Also check that we're not trying to register a 3pid that's already
+                # been registered.
+                #
+                # This has probably happened in /register/email/requestToken as well,
+                # but if a user hits this endpoint twice then clicks on each link from
+                # the two activation emails, they would register the same 3pid twice.
+                for login_type in [LoginType.EMAIL_IDENTITY, LoginType.MSISDN]:
+                    if login_type in auth_result:
+                        medium = auth_result[login_type]["medium"]
+                        address = auth_result[login_type]["address"]
+                        # For emails, canonicalise the address.
+                        # We store all email addresses canonicalised in the DB.
+                        # (See on_POST in EmailThreepidRequestTokenRestServlet
+                        # in synapse/rest/client/account.py)
+                        if medium == "email":
+                            try:
+                                address = canonicalise_email(address)
+                            except ValueError as e:
+                                raise SynapseError(400, str(e))
+
+                        existing_user_id = await self.store.get_user_id_by_threepid(
+                            medium, address
+                        )
+
+                        if existing_user_id is not None:
+                            raise SynapseError(
+                                400,
+                                "%s is already in use" % medium,
+                                Codes.THREEPID_IN_USE,
+                            )
+
+            entries = await self.store.get_user_agents_ips_to_ui_auth_session(
+                session_id
+            )
+
+            registered_user_id = await self.registration_handler.register_user(
+                localpart=desired_username,
+                password_hash=password_hash,
+                guest_access_token=guest_access_token,
+                threepid=threepid,
+                address=client_addr,
+                user_agent_ips=entries,
+            )
+            # Necessary due to auth checks prior to the threepid being
+            # written to the db
+            if threepid:
+                if is_threepid_reserved(
+                    self.hs.config.mau_limits_reserved_threepids, threepid
+                ):
+                    await self.store.upsert_monthly_active_user(registered_user_id)
+
+            # Remember that the user account has been registered (and the user
+            # ID it was registered with, since it might not have been specified).
+            await self.auth_handler.set_session_data(
+                session_id,
+                UIAuthSessionDataConstants.REGISTERED_USER_ID,
+                registered_user_id,
+            )
+
+            registered = True
+
+        return_dict = await self._create_registration_details(
+            registered_user_id,
+            params,
+            should_issue_refresh_token=should_issue_refresh_token,
+        )
+
+        if registered:
+            await self.registration_handler.post_registration_actions(
+                user_id=registered_user_id,
+                auth_result=auth_result,
+                access_token=return_dict.get("access_token"),
+            )
+
+        return 200, return_dict
+
+    async def _do_appservice_registration(
+        self, username, as_token, body, should_issue_refresh_token: bool = False
+    ):
+        user_id = await self.registration_handler.appservice_register(
+            username, as_token
+        )
+        return await self._create_registration_details(
+            user_id,
+            body,
+            is_appservice_ghost=True,
+            should_issue_refresh_token=should_issue_refresh_token,
+        )
+
+    async def _create_registration_details(
+        self,
+        user_id: str,
+        params: JsonDict,
+        is_appservice_ghost: bool = False,
+        should_issue_refresh_token: bool = False,
+    ):
+        """Complete registration of newly-registered user
+
+        Allocates device_id if one was not given; also creates access_token.
+
+        Args:
+            user_id: full canonical @user:id
+            params: registration parameters, from which we pull device_id,
+                initial_device_name and inhibit_login
+            is_appservice_ghost
+            should_issue_refresh_token: True if this registration should issue
+                a refresh token alongside the access token.
+        Returns:
+             dictionary for response from /register
+        """
+        result = {"user_id": user_id, "home_server": self.hs.hostname}
+        if not params.get("inhibit_login", False):
+            device_id = params.get("device_id")
+            initial_display_name = params.get("initial_device_display_name")
+            (
+                device_id,
+                access_token,
+                valid_until_ms,
+                refresh_token,
+            ) = await self.registration_handler.register_device(
+                user_id,
+                device_id,
+                initial_display_name,
+                is_guest=False,
+                is_appservice_ghost=is_appservice_ghost,
+                should_issue_refresh_token=should_issue_refresh_token,
+            )
+
+            result.update({"access_token": access_token, "device_id": device_id})
+
+            if valid_until_ms is not None:
+                expires_in_ms = valid_until_ms - self.clock.time_msec()
+                result["expires_in_ms"] = expires_in_ms
+
+            if refresh_token is not None:
+                result["refresh_token"] = refresh_token
+
+        return result
+
+    async def _do_guest_registration(self, params, address=None):
+        if not self.hs.config.allow_guest_access:
+            raise SynapseError(403, "Guest access is disabled")
+        user_id = await self.registration_handler.register_user(
+            make_guest=True, address=address
+        )
+
+        # we don't allow guests to specify their own device_id, because
+        # we have nowhere to store it.
+        device_id = synapse.api.auth.GUEST_DEVICE_ID
+        initial_display_name = params.get("initial_device_display_name")
+        (
+            device_id,
+            access_token,
+            valid_until_ms,
+            refresh_token,
+        ) = await self.registration_handler.register_device(
+            user_id, device_id, initial_display_name, is_guest=True
+        )
+
+        result = {
+            "user_id": user_id,
+            "device_id": device_id,
+            "access_token": access_token,
+            "home_server": self.hs.hostname,
+        }
+
+        if valid_until_ms is not None:
+            expires_in_ms = valid_until_ms - self.clock.time_msec()
+            result["expires_in_ms"] = expires_in_ms
+
+        if refresh_token is not None:
+            result["refresh_token"] = refresh_token
+
+        return 200, result
+
+
+def _calculate_registration_flows(
+    # technically `config` has to provide *all* of these interfaces, not just one
+    config: Union[RegistrationConfig, ConsentConfig, CaptchaConfig],
+    auth_handler: AuthHandler,
+) -> List[List[str]]:
+    """Get a suitable flows list for registration
+
+    Args:
+        config: server configuration
+        auth_handler: authorization handler
+
+    Returns: a list of supported flows
+    """
+    # FIXME: need a better error than "no auth flow found" for scenarios
+    # where we required 3PID for registration but the user didn't give one
+    require_email = "email" in config.registrations_require_3pid
+    require_msisdn = "msisdn" in config.registrations_require_3pid
+
+    show_msisdn = True
+    show_email = True
+
+    if config.disable_msisdn_registration:
+        show_msisdn = False
+        require_msisdn = False
+
+    enabled_auth_types = auth_handler.get_enabled_auth_types()
+    if LoginType.EMAIL_IDENTITY not in enabled_auth_types:
+        show_email = False
+        if require_email:
+            raise ConfigError(
+                "Configuration requires email address at registration, but email "
+                "validation is not configured"
+            )
+
+    if LoginType.MSISDN not in enabled_auth_types:
+        show_msisdn = False
+        if require_msisdn:
+            raise ConfigError(
+                "Configuration requires msisdn at registration, but msisdn "
+                "validation is not configured"
+            )
+
+    flows = []
+
+    # only support 3PIDless registration if no 3PIDs are required
+    if not require_email and not require_msisdn:
+        # Add a dummy step here, otherwise if a client completes
+        # recaptcha first we'll assume they were going for this flow
+        # and complete the request, when they could have been trying to
+        # complete one of the flows with email/msisdn auth.
+        flows.append([LoginType.DUMMY])
+
+    # only support the email-only flow if we don't require MSISDN 3PIDs
+    if show_email and not require_msisdn:
+        flows.append([LoginType.EMAIL_IDENTITY])
+
+    # only support the MSISDN-only flow if we don't require email 3PIDs
+    if show_msisdn and not require_email:
+        flows.append([LoginType.MSISDN])
+
+    if show_email and show_msisdn:
+        # always let users provide both MSISDN & email
+        flows.append([LoginType.MSISDN, LoginType.EMAIL_IDENTITY])
+
+    # Prepend m.login.terms to all flows if we're requiring consent
+    if config.user_consent_at_registration:
+        for flow in flows:
+            flow.insert(0, LoginType.TERMS)
+
+    # Prepend recaptcha to all flows if we're requiring captcha
+    if config.enable_registration_captcha:
+        for flow in flows:
+            flow.insert(0, LoginType.RECAPTCHA)
+
+    return flows
+
+
+def register_servlets(hs, http_server):
+    EmailRegisterRequestTokenRestServlet(hs).register(http_server)
+    MsisdnRegisterRequestTokenRestServlet(hs).register(http_server)
+    UsernameAvailabilityRestServlet(hs).register(http_server)
+    RegistrationSubmitTokenServlet(hs).register(http_server)
+    RegisterRestServlet(hs).register(http_server)