diff --git a/changelog.d/8942.feature b/changelog.d/8942.feature new file mode 100644 index 000000000..d450ef499 --- /dev/null +++ b/changelog.d/8942.feature @@ -0,0 +1 @@ +Add support for allowing users to pick their own user ID during a single-sign-on login. diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml index 549c581a9..077cb619c 100644 --- a/docs/sample_config.yaml +++ b/docs/sample_config.yaml @@ -1825,9 +1825,10 @@ oidc_config: # * user: The claims returned by the UserInfo Endpoint and/or in the ID # Token # - # This must be configured if using the default mapping provider. + # If this is not set, the user will be prompted to choose their + # own username. # - localpart_template: "{{ user.preferred_username }}" + #localpart_template: "{{ user.preferred_username }}" # Jinja2 template for the display name to set on first login. # diff --git a/docs/sso_mapping_providers.md b/docs/sso_mapping_providers.md index 7714b1d84..e1d6ede7b 100644 --- a/docs/sso_mapping_providers.md +++ b/docs/sso_mapping_providers.md @@ -15,12 +15,18 @@ where SAML mapping providers come into play. SSO mapping providers are currently supported for OpenID and SAML SSO configurations. Please see the details below for how to implement your own. -It is the responsibility of the mapping provider to normalise the SSO attributes -and map them to a valid Matrix ID. The -[specification for Matrix IDs](https://matrix.org/docs/spec/appendices#user-identifiers) -has some information about what is considered valid. Alternately an easy way to -ensure it is valid is to use a Synapse utility function: -`synapse.types.map_username_to_mxid_localpart`. +It is up to the mapping provider whether the user should be assigned a predefined +Matrix ID based on the SSO attributes, or if the user should be allowed to +choose their own username. + +In the first case - where users are automatically allocated a Matrix ID - it is +the responsibility of the mapping provider to normalise the SSO attributes and +map them to a valid Matrix ID. The [specification for Matrix +IDs](https://matrix.org/docs/spec/appendices#user-identifiers) has some +information about what is considered valid. + +If the mapping provider does not assign a Matrix ID, then Synapse will +automatically serve an HTML page allowing the user to pick their own username. External mapping providers are provided to Synapse in the form of an external Python module. You can retrieve this module from [PyPI](https://pypi.org) or elsewhere, @@ -80,8 +86,9 @@ A custom mapping provider must specify the following methods: with failures=1. The method should then return a different `localpart` value, such as `john.doe1`. - Returns a dictionary with two keys: - - localpart: A required string, used to generate the Matrix ID. - - displayname: An optional string, the display name for the user. + - `localpart`: A string, used to generate the Matrix ID. If this is + `None`, the user is prompted to pick their own username. + - `displayname`: An optional string, the display name for the user. * `get_extra_attributes(self, userinfo, token)` - This method must be async. - Arguments: @@ -165,12 +172,13 @@ A custom mapping provider must specify the following methods: redirected to. - This method must return a dictionary, which will then be used by Synapse to build a new user. The following keys are allowed: - * `mxid_localpart` - Required. The mxid localpart of the new user. + * `mxid_localpart` - The mxid localpart of the new user. If this is + `None`, the user is prompted to pick their own username. * `displayname` - The displayname of the new user. If not provided, will default to the value of `mxid_localpart`. * `emails` - A list of emails for the new user. If not provided, will default to an empty list. - + Alternatively it can raise a `synapse.api.errors.RedirectException` to redirect the user to another page. This is useful to prompt the user for additional information, e.g. if you want them to provide their own username. diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py index bbb740783..8d9b53be5 100644 --- a/synapse/app/homeserver.py +++ b/synapse/app/homeserver.py @@ -63,6 +63,7 @@ from synapse.rest import ClientRestResource from synapse.rest.admin import AdminRestResource from synapse.rest.health import HealthResource from synapse.rest.key.v2 import KeyApiV2Resource +from synapse.rest.synapse.client.pick_username import pick_username_resource from synapse.rest.well_known import WellKnownResource from synapse.server import HomeServer from synapse.storage import DataStore @@ -192,6 +193,7 @@ class SynapseHomeServer(HomeServer): "/_matrix/client/versions": client_resource, "/.well-known/matrix/client": WellKnownResource(self), "/_synapse/admin": AdminRestResource(self), + "/_synapse/client/pick_username": pick_username_resource(self), } ) diff --git a/synapse/config/oidc_config.py b/synapse/config/oidc_config.py index 1abf8ed40..4e3055282 100644 --- a/synapse/config/oidc_config.py +++ b/synapse/config/oidc_config.py @@ -203,9 +203,10 @@ class OIDCConfig(Config): # * user: The claims returned by the UserInfo Endpoint and/or in the ID # Token # - # This must be configured if using the default mapping provider. + # If this is not set, the user will be prompted to choose their + # own username. # - localpart_template: "{{{{ user.preferred_username }}}}" + #localpart_template: "{{{{ user.preferred_username }}}}" # Jinja2 template for the display name to set on first login. # diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py index cbd11a138..709f8dfc1 100644 --- a/synapse/handlers/oidc_handler.py +++ b/synapse/handlers/oidc_handler.py @@ -947,7 +947,7 @@ class OidcHandler(BaseHandler): UserAttributeDict = TypedDict( - "UserAttributeDict", {"localpart": str, "display_name": Optional[str]} + "UserAttributeDict", {"localpart": Optional[str], "display_name": Optional[str]} ) C = TypeVar("C") @@ -1028,10 +1028,10 @@ env = Environment(finalize=jinja_finalize) @attr.s class JinjaOidcMappingConfig: - subject_claim = attr.ib() # type: str - localpart_template = attr.ib() # type: Template - display_name_template = attr.ib() # type: Optional[Template] - extra_attributes = attr.ib() # type: Dict[str, Template] + subject_claim = attr.ib(type=str) + localpart_template = attr.ib(type=Optional[Template]) + display_name_template = attr.ib(type=Optional[Template]) + extra_attributes = attr.ib(type=Dict[str, Template]) class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]): @@ -1047,18 +1047,14 @@ class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]): def parse_config(config: dict) -> JinjaOidcMappingConfig: subject_claim = config.get("subject_claim", "sub") - if "localpart_template" not in config: - raise ConfigError( - "missing key: oidc_config.user_mapping_provider.config.localpart_template" - ) - - try: - localpart_template = env.from_string(config["localpart_template"]) - except Exception as e: - raise ConfigError( - "invalid jinja template for oidc_config.user_mapping_provider.config.localpart_template: %r" - % (e,) - ) + localpart_template = None # type: Optional[Template] + if "localpart_template" in config: + try: + localpart_template = env.from_string(config["localpart_template"]) + except Exception as e: + raise ConfigError( + "invalid jinja template", path=["localpart_template"] + ) from e display_name_template = None # type: Optional[Template] if "display_name_template" in config: @@ -1066,26 +1062,22 @@ class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]): display_name_template = env.from_string(config["display_name_template"]) except Exception as e: raise ConfigError( - "invalid jinja template for oidc_config.user_mapping_provider.config.display_name_template: %r" - % (e,) - ) + "invalid jinja template", path=["display_name_template"] + ) from e extra_attributes = {} # type Dict[str, Template] if "extra_attributes" in config: extra_attributes_config = config.get("extra_attributes") or {} if not isinstance(extra_attributes_config, dict): - raise ConfigError( - "oidc_config.user_mapping_provider.config.extra_attributes must be a dict" - ) + raise ConfigError("must be a dict", path=["extra_attributes"]) for key, value in extra_attributes_config.items(): try: extra_attributes[key] = env.from_string(value) except Exception as e: raise ConfigError( - "invalid jinja template for oidc_config.user_mapping_provider.config.extra_attributes.%s: %r" - % (key, e) - ) + "invalid jinja template", path=["extra_attributes", key] + ) from e return JinjaOidcMappingConfig( subject_claim=subject_claim, @@ -1100,14 +1092,17 @@ class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]): async def map_user_attributes( self, userinfo: UserInfo, token: Token, failures: int ) -> UserAttributeDict: - localpart = self._config.localpart_template.render(user=userinfo).strip() + localpart = None - # Ensure only valid characters are included in the MXID. - localpart = map_username_to_mxid_localpart(localpart) + if self._config.localpart_template: + localpart = self._config.localpart_template.render(user=userinfo).strip() - # Append suffix integer if last call to this function failed to produce - # a usable mxid. - localpart += str(failures) if failures else "" + # Ensure only valid characters are included in the MXID. + localpart = map_username_to_mxid_localpart(localpart) + + # Append suffix integer if last call to this function failed to produce + # a usable mxid. + localpart += str(failures) if failures else "" display_name = None # type: Optional[str] if self._config.display_name_template is not None: diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py index f054b66a5..548b02211 100644 --- a/synapse/handlers/sso.py +++ b/synapse/handlers/sso.py @@ -13,17 +13,19 @@ # See the License for the specific language governing permissions and # limitations under the License. import logging -from typing import TYPE_CHECKING, Awaitable, Callable, List, Optional +from typing import TYPE_CHECKING, Awaitable, Callable, Dict, List, Optional import attr +from typing_extensions import NoReturn from twisted.web.http import Request -from synapse.api.errors import RedirectException +from synapse.api.errors import RedirectException, SynapseError from synapse.http.server import respond_with_html from synapse.http.site import SynapseRequest from synapse.types import JsonDict, UserID, contains_invalid_mxid_characters from synapse.util.async_helpers import Linearizer +from synapse.util.stringutils import random_string if TYPE_CHECKING: from synapse.server import HomeServer @@ -40,16 +42,52 @@ class MappingException(Exception): @attr.s class UserAttributes: - localpart = attr.ib(type=str) + # the localpart of the mxid that the mapper has assigned to the user. + # if `None`, the mapper has not picked a userid, and the user should be prompted to + # enter one. + localpart = attr.ib(type=Optional[str]) display_name = attr.ib(type=Optional[str], default=None) emails = attr.ib(type=List[str], default=attr.Factory(list)) +@attr.s(slots=True) +class UsernameMappingSession: + """Data we track about SSO sessions""" + + # A unique identifier for this SSO provider, e.g. "oidc" or "saml". + auth_provider_id = attr.ib(type=str) + + # user ID on the IdP server + remote_user_id = attr.ib(type=str) + + # attributes returned by the ID mapper + display_name = attr.ib(type=Optional[str]) + emails = attr.ib(type=List[str]) + + # An optional dictionary of extra attributes to be provided to the client in the + # login response. + extra_login_attributes = attr.ib(type=Optional[JsonDict]) + + # where to redirect the client back to + client_redirect_url = attr.ib(type=str) + + # expiry time for the session, in milliseconds + expiry_time_ms = attr.ib(type=int) + + +# the HTTP cookie used to track the mapping session id +USERNAME_MAPPING_SESSION_COOKIE_NAME = b"username_mapping_session" + + class SsoHandler: # The number of attempts to ask the mapping provider for when generating an MXID. _MAP_USERNAME_RETRIES = 1000 + # the time a UsernameMappingSession remains valid for + _MAPPING_SESSION_VALIDITY_PERIOD_MS = 15 * 60 * 1000 + def __init__(self, hs: "HomeServer"): + self._clock = hs.get_clock() self._store = hs.get_datastore() self._server_name = hs.hostname self._registration_handler = hs.get_registration_handler() @@ -59,6 +97,9 @@ class SsoHandler: # a lock on the mappings self._mapping_lock = Linearizer(name="sso_user_mapping", clock=hs.get_clock()) + # a map from session id to session data + self._username_mapping_sessions = {} # type: Dict[str, UsernameMappingSession] + def render_error( self, request, error: str, error_description: Optional[str] = None ) -> None: @@ -206,6 +247,18 @@ class SsoHandler: # Otherwise, generate a new user. if not user_id: attributes = await self._call_attribute_mapper(sso_to_matrix_id_mapper) + + if attributes.localpart is None: + # the mapper doesn't return a username. bail out with a redirect to + # the username picker. + await self._redirect_to_username_picker( + auth_provider_id, + remote_user_id, + attributes, + client_redirect_url, + extra_login_attributes, + ) + user_id = await self._register_mapped_user( attributes, auth_provider_id, @@ -243,10 +296,8 @@ class SsoHandler: ) if not attributes.localpart: - raise MappingException( - "Error parsing SSO response: SSO mapping provider plugin " - "did not return a localpart value" - ) + # the mapper has not picked a localpart + return attributes # Check if this mxid already exists user_id = UserID(attributes.localpart, self._server_name).to_string() @@ -261,6 +312,59 @@ class SsoHandler: ) return attributes + async def _redirect_to_username_picker( + self, + auth_provider_id: str, + remote_user_id: str, + attributes: UserAttributes, + client_redirect_url: str, + extra_login_attributes: Optional[JsonDict], + ) -> NoReturn: + """Creates a UsernameMappingSession and redirects the browser + + Called if the user mapping provider doesn't return a localpart for a new user. + Raises a RedirectException which redirects the browser to the username picker. + + Args: + auth_provider_id: A unique identifier for this SSO provider, e.g. + "oidc" or "saml". + + remote_user_id: The unique identifier from the SSO provider. + + attributes: the user attributes returned by the user mapping provider. + + client_redirect_url: The redirect URL passed in by the client, which we + will eventually redirect back to. + + extra_login_attributes: An optional dictionary of extra + attributes to be provided to the client in the login response. + + Raises: + RedirectException + """ + session_id = random_string(16) + now = self._clock.time_msec() + session = UsernameMappingSession( + auth_provider_id=auth_provider_id, + remote_user_id=remote_user_id, + display_name=attributes.display_name, + emails=attributes.emails, + client_redirect_url=client_redirect_url, + expiry_time_ms=now + self._MAPPING_SESSION_VALIDITY_PERIOD_MS, + extra_login_attributes=extra_login_attributes, + ) + + self._username_mapping_sessions[session_id] = session + logger.info("Recorded registration session id %s", session_id) + + # Set the cookie and redirect to the username picker + e = RedirectException(b"/_synapse/client/pick_username") + e.cookies.append( + b"%s=%s; path=/" + % (USERNAME_MAPPING_SESSION_COOKIE_NAME, session_id.encode("ascii")) + ) + raise e + async def _register_mapped_user( self, attributes: UserAttributes, @@ -269,9 +373,38 @@ class SsoHandler: user_agent: str, ip_address: str, ) -> str: + """Register a new SSO user. + + This is called once we have successfully mapped the remote user id onto a local + user id, one way or another. + + Args: + attributes: user attributes returned by the user mapping provider, + including a non-empty localpart. + + auth_provider_id: A unique identifier for this SSO provider, e.g. + "oidc" or "saml". + + remote_user_id: The unique identifier from the SSO provider. + + user_agent: The user-agent in the HTTP request (used for potential + shadow-banning.) + + ip_address: The IP address of the requester (used for potential + shadow-banning.) + + Raises: + a MappingException if the localpart is invalid. + + a SynapseError with code 400 and errcode Codes.USER_IN_USE if the localpart + is already taken. + """ + # Since the localpart is provided via a potentially untrusted module, # ensure the MXID is valid before registering. - if contains_invalid_mxid_characters(attributes.localpart): + if not attributes.localpart or contains_invalid_mxid_characters( + attributes.localpart + ): raise MappingException("localpart is invalid: %s" % (attributes.localpart,)) logger.debug("Mapped SSO user to local part %s", attributes.localpart) @@ -326,3 +459,108 @@ class SsoHandler: await self._auth_handler.complete_sso_ui_auth( user_id, ui_auth_session_id, request ) + + async def check_username_availability( + self, localpart: str, session_id: str, + ) -> bool: + """Handle an "is username available" callback check + + Args: + localpart: desired localpart + session_id: the session id for the username picker + Returns: + True if the username is available + Raises: + SynapseError if the localpart is invalid or the session is unknown + """ + + # make sure that there is a valid mapping session, to stop people dictionary- + # scanning for accounts + + self._expire_old_sessions() + session = self._username_mapping_sessions.get(session_id) + if not session: + logger.info("Couldn't find session id %s", session_id) + raise SynapseError(400, "unknown session") + + logger.info( + "[session %s] Checking for availability of username %s", + session_id, + localpart, + ) + + if contains_invalid_mxid_characters(localpart): + raise SynapseError(400, "localpart is invalid: %s" % (localpart,)) + user_id = UserID(localpart, self._server_name).to_string() + user_infos = await self._store.get_users_by_id_case_insensitive(user_id) + + logger.info("[session %s] users: %s", session_id, user_infos) + return not user_infos + + async def handle_submit_username_request( + self, request: SynapseRequest, localpart: str, session_id: str + ) -> None: + """Handle a request to the username-picker 'submit' endpoint + + Will serve an HTTP response to the request. + + Args: + request: HTTP request + localpart: localpart requested by the user + session_id: ID of the username mapping session, extracted from a cookie + """ + self._expire_old_sessions() + session = self._username_mapping_sessions.get(session_id) + if not session: + logger.info("Couldn't find session id %s", session_id) + raise SynapseError(400, "unknown session") + + logger.info("[session %s] Registering localpart %s", session_id, localpart) + + attributes = UserAttributes( + localpart=localpart, + display_name=session.display_name, + emails=session.emails, + ) + + # the following will raise a 400 error if the username has been taken in the + # meantime. + user_id = await self._register_mapped_user( + attributes, + session.auth_provider_id, + session.remote_user_id, + request.get_user_agent(""), + request.getClientIP(), + ) + + logger.info("[session %s] Registered userid %s", session_id, user_id) + + # delete the mapping session and the cookie + del self._username_mapping_sessions[session_id] + + # delete the cookie + request.addCookie( + USERNAME_MAPPING_SESSION_COOKIE_NAME, + b"", + expires=b"Thu, 01 Jan 1970 00:00:00 GMT", + path=b"/", + ) + + await self._auth_handler.complete_sso_login( + user_id, + request, + session.client_redirect_url, + session.extra_login_attributes, + ) + + def _expire_old_sessions(self): + to_expire = [] + now = int(self._clock.time_msec()) + + for session_id, session in self._username_mapping_sessions.items(): + if session.expiry_time_ms <= now: + to_expire.append(session_id) + + for session_id in to_expire: + logger.info("Expiring mapping session %s", session_id) + del self._username_mapping_sessions[session_id] diff --git a/synapse/res/username_picker/index.html b/synapse/res/username_picker/index.html new file mode 100644 index 000000000..37ea8bb6d --- /dev/null +++ b/synapse/res/username_picker/index.html @@ -0,0 +1,19 @@ + + +
+