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synapse-product/synapse/handlers/oidc.py
Quentin Gliech fe1daad672
Move the "email unsubscribe" resource, refactor the macaroon generator & simplify the access token verification logic. (#12986) 
This simplifies the access token verification logic by removing the `rights`
parameter which was only ever used for the unsubscribe link in email
notifications. The latter has been moved under the `/_synapse` namespace,
since it is not a standard API.

This also makes the email verification link more secure, by embedding the
app_id and pushkey in the macaroon and verifying it. This prevents the user
from tampering the query parameters of that unsubscribe link.

Macaroon generation is refactored:

- Centralised all macaroon generation and verification logic to the
  `MacaroonGenerator`
- Moved to `synapse.utils`
- Changed the constructor to require only a `Clock`, hostname, and a secret key
  (instead of a full `Homeserver`).
- Added tests for all methods.
2022-06-14 09:12:08 -04:00

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# Copyright 2020 Quentin Gliech
# Copyright 2021 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 inspect
import logging
from typing import TYPE_CHECKING, Any, Dict, Generic, List, Optional, TypeVar, Union
from urllib.parse import urlencode, urlparse
import attr
from authlib.common.security import generate_token
from authlib.jose import JsonWebToken, jwt
from authlib.oauth2.auth import ClientAuth
from authlib.oauth2.rfc6749.parameters import prepare_grant_uri
from authlib.oidc.core import CodeIDToken, UserInfo
from authlib.oidc.discovery import OpenIDProviderMetadata, get_well_known_url
from jinja2 import Environment, Template
from pymacaroons.exceptions import (
MacaroonDeserializationException,
MacaroonInitException,
MacaroonInvalidSignatureException,
)
from typing_extensions import TypedDict
from twisted.web.client import readBody
from twisted.web.http_headers import Headers
from synapse.config import ConfigError
from synapse.config.oidc import OidcProviderClientSecretJwtKey, OidcProviderConfig
from synapse.handlers.sso import MappingException, UserAttributes
from synapse.http.site import SynapseRequest
from synapse.logging.context import make_deferred_yieldable
from synapse.types import JsonDict, UserID, map_username_to_mxid_localpart
from synapse.util import Clock, json_decoder
from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
from synapse.util.macaroons import MacaroonGenerator, OidcSessionData
from synapse.util.templates import _localpart_from_email_filter
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
# we want the cookie to be returned to us even when the request is the POSTed
# result of a form on another domain, as is used with `response_mode=form_post`.
#
# Modern browsers will not do so unless we set SameSite=None; however *older*
# browsers (including all versions of Safari on iOS 12?) don't support
# SameSite=None, and interpret it as SameSite=Strict:
# https://bugs.webkit.org/show_bug.cgi?id=198181
#
# As a rather painful workaround, we set *two* cookies, one with SameSite=None
# and one with no SameSite, in the hope that at least one of them will get
# back to us.
#
# Secure is necessary for SameSite=None (and, empirically, also breaks things
# on iOS 12.)
#
# Here we have the names of the cookies, and the options we use to set them.
_SESSION_COOKIES = [
(b"oidc_session", b"HttpOnly; Secure; SameSite=None"),
(b"oidc_session_no_samesite", b"HttpOnly"),
]
#: A token exchanged from the token endpoint, as per RFC6749 sec 5.1. and
#: OpenID.Core sec 3.1.3.3.
class Token(TypedDict):
access_token: str
token_type: str
id_token: Optional[str]
refresh_token: Optional[str]
expires_in: int
scope: Optional[str]
#: A JWK, as per RFC7517 sec 4. The type could be more precise than that, but
#: there is no real point of doing this in our case.
JWK = Dict[str, str]
#: A JWK Set, as per RFC7517 sec 5.
class JWKS(TypedDict):
keys: List[JWK]
class OidcHandler:
"""Handles requests related to the OpenID Connect login flow."""
def __init__(self, hs: "HomeServer"):
self._sso_handler = hs.get_sso_handler()
provider_confs = hs.config.oidc.oidc_providers
# we should not have been instantiated if there is no configured provider.
assert provider_confs
self._macaroon_generator = hs.get_macaroon_generator()
self._providers: Dict[str, "OidcProvider"] = {
p.idp_id: OidcProvider(hs, self._macaroon_generator, p)
for p in provider_confs
}
async def load_metadata(self) -> None:
"""Validate the config and load the metadata from the remote endpoint.
Called at startup to ensure we have everything we need.
"""
for idp_id, p in self._providers.items():
try:
await p.load_metadata()
if not p._uses_userinfo:
await p.load_jwks()
except Exception as e:
raise Exception(
"Error while initialising OIDC provider %r" % (idp_id,)
) from e
async def handle_oidc_callback(self, request: SynapseRequest) -> None:
"""Handle an incoming request to /_synapse/client/oidc/callback
Since we might want to display OIDC-related errors in a user-friendly
way, we don't raise SynapseError from here. Instead, we call
``self._sso_handler.render_error`` which displays an HTML page for the error.
Most of the OpenID Connect logic happens here:
- first, we check if there was any error returned by the provider and
display it
- then we fetch the session cookie, decode and verify it
- the ``state`` query parameter should match with the one stored in the
session cookie
Once we know the session is legit, we then delegate to the OIDC Provider
implementation, which will exchange the code with the provider and complete the
login/authentication.
Args:
request: the incoming request from the browser.
"""
# This will always be set by the time Twisted calls us.
assert request.args is not None
# The provider might redirect with an error.
# In that case, just display it as-is.
if b"error" in request.args:
# error response from the auth server. see:
# https://tools.ietf.org/html/rfc6749#section-4.1.2.1
# https://openid.net/specs/openid-connect-core-1_0.html#AuthError
error = request.args[b"error"][0].decode()
description = request.args.get(b"error_description", [b""])[0].decode()
# Most of the errors returned by the provider could be due by
# either the provider misbehaving or Synapse being misconfigured.
# The only exception of that is "access_denied", where the user
# probably cancelled the login flow. In other cases, log those errors.
logger.log(
logging.INFO if error == "access_denied" else logging.ERROR,
"Received OIDC callback with error: %s %s",
error,
description,
)
self._sso_handler.render_error(request, error, description)
return
# otherwise, it is presumably a successful response. see:
# https://tools.ietf.org/html/rfc6749#section-4.1.2
# Fetch the session cookie. See the comments on SESSION_COOKIES for why there
# are two.
for cookie_name, _ in _SESSION_COOKIES:
session: Optional[bytes] = request.getCookie(cookie_name)
if session is not None:
break
else:
logger.info("Received OIDC callback, with no session cookie")
self._sso_handler.render_error(
request, "missing_session", "No session cookie found"
)
return
# Remove the cookies. There is a good chance that if the callback failed
# once, it will fail next time and the code will already be exchanged.
# Removing the cookies early avoids spamming the provider with token requests.
#
# we have to build the header by hand rather than calling request.addCookie
# because the latter does not support SameSite=None
# (https://twistedmatrix.com/trac/ticket/10088)
for cookie_name, options in _SESSION_COOKIES:
request.cookies.append(
b"%s=; Expires=Thu, Jan 01 1970 00:00:00 UTC; %s"
% (cookie_name, options)
)
# Check for the state query parameter
if b"state" not in request.args:
logger.info("Received OIDC callback, with no state parameter")
self._sso_handler.render_error(
request, "invalid_request", "State parameter is missing"
)
return
state = request.args[b"state"][0].decode()
# Deserialize the session token and verify it.
try:
session_data = self._macaroon_generator.verify_oidc_session_token(
session, state
)
except (MacaroonInitException, MacaroonDeserializationException, KeyError) as e:
logger.exception("Invalid session for OIDC callback")
self._sso_handler.render_error(request, "invalid_session", str(e))
return
except MacaroonInvalidSignatureException as e:
logger.warning("Could not verify session for OIDC callback: %s", e)
self._sso_handler.render_error(request, "mismatching_session", str(e))
return
logger.info("Received OIDC callback for IdP %s", session_data.idp_id)
oidc_provider = self._providers.get(session_data.idp_id)
if not oidc_provider:
logger.error("OIDC session uses unknown IdP %r", oidc_provider)
self._sso_handler.render_error(request, "unknown_idp", "Unknown IdP")
return
if b"code" not in request.args:
logger.info("Code parameter is missing")
self._sso_handler.render_error(
request, "invalid_request", "Code parameter is missing"
)
return
code = request.args[b"code"][0].decode()
await oidc_provider.handle_oidc_callback(request, session_data, code)
class OidcError(Exception):
"""Used to catch errors when calling the token_endpoint"""
def __init__(self, error: str, error_description: Optional[str] = None):
self.error = error
self.error_description = error_description
def __str__(self) -> str:
if self.error_description:
return f"{self.error}: {self.error_description}"
return self.error
class OidcProvider:
"""Wraps the config for a single OIDC IdentityProvider
Provides methods for handling redirect requests and callbacks via that particular
IdP.
"""
def __init__(
self,
hs: "HomeServer",
macaroon_generator: MacaroonGenerator,
provider: OidcProviderConfig,
):
self._store = hs.get_datastores().main
self._macaroon_generaton = macaroon_generator
self._config = provider
self._callback_url: str = hs.config.oidc.oidc_callback_url
# Calculate the prefix for OIDC callback paths based on the public_baseurl.
# We'll insert this into the Path= parameter of any session cookies we set.
public_baseurl_path = urlparse(hs.config.server.public_baseurl).path
self._callback_path_prefix = (
public_baseurl_path.encode("utf-8") + b"_synapse/client/oidc"
)
self._oidc_attribute_requirements = provider.attribute_requirements
self._scopes = provider.scopes
self._user_profile_method = provider.user_profile_method
client_secret: Optional[Union[str, JwtClientSecret]] = None
if provider.client_secret:
client_secret = provider.client_secret
elif provider.client_secret_jwt_key:
client_secret = JwtClientSecret(
provider.client_secret_jwt_key,
provider.client_id,
provider.issuer,
hs.get_clock(),
)
self._client_auth = ClientAuth(
provider.client_id,
client_secret,
provider.client_auth_method,
)
self._client_auth_method = provider.client_auth_method
# cache of metadata for the identity provider (endpoint uris, mostly). This is
# loaded on-demand from the discovery endpoint (if discovery is enabled), with
# possible overrides from the config. Access via `load_metadata`.
self._provider_metadata = RetryOnExceptionCachedCall(self._load_metadata)
# cache of JWKs used by the identity provider to sign tokens. Loaded on demand
# from the IdP's jwks_uri, if required.
self._jwks = RetryOnExceptionCachedCall(self._load_jwks)
self._user_mapping_provider = provider.user_mapping_provider_class(
provider.user_mapping_provider_config
)
self._skip_verification = provider.skip_verification
self._allow_existing_users = provider.allow_existing_users
self._http_client = hs.get_proxied_http_client()
self._server_name: str = hs.config.server.server_name
# identifier for the external_ids table
self.idp_id = provider.idp_id
# user-facing name of this auth provider
self.idp_name = provider.idp_name
# MXC URI for icon for this auth provider
self.idp_icon = provider.idp_icon
# optional brand identifier for this auth provider
self.idp_brand = provider.idp_brand
self._sso_handler = hs.get_sso_handler()
self._sso_handler.register_identity_provider(self)
def _validate_metadata(self, m: OpenIDProviderMetadata) -> None:
"""Verifies the provider metadata.
This checks the validity of the currently loaded provider. Not
everything is checked, only:
- ``issuer``
- ``authorization_endpoint``
- ``token_endpoint``
- ``response_types_supported`` (checks if "code" is in it)
- ``jwks_uri``
Raises:
ValueError: if something in the provider is not valid
"""
# Skip verification to allow non-compliant providers (e.g. issuers not running on a secure origin)
if self._skip_verification is True:
return
m.validate_issuer()
m.validate_authorization_endpoint()
m.validate_token_endpoint()
if m.get("token_endpoint_auth_methods_supported") is not None:
m.validate_token_endpoint_auth_methods_supported()
if (
self._client_auth_method
not in m["token_endpoint_auth_methods_supported"]
):
raise ValueError(
'"{auth_method}" not in "token_endpoint_auth_methods_supported" ({supported!r})'.format(
auth_method=self._client_auth_method,
supported=m["token_endpoint_auth_methods_supported"],
)
)
if m.get("response_types_supported") is not None:
m.validate_response_types_supported()
if "code" not in m["response_types_supported"]:
raise ValueError(
'"code" not in "response_types_supported" (%r)'
% (m["response_types_supported"],)
)
# Ensure there's a userinfo endpoint to fetch from if it is required.
if self._uses_userinfo:
if m.get("userinfo_endpoint") is None:
raise ValueError(
'provider has no "userinfo_endpoint", even though it is required'
)
else:
# If we're not using userinfo, we need a valid jwks to validate the ID token
m.validate_jwks_uri()
@property
def _uses_userinfo(self) -> bool:
"""Returns True if the ``userinfo_endpoint`` should be used.
This is based on the requested scopes: if the scopes include
``openid``, the provider should give use an ID token containing the
user information. If not, we should fetch them using the
``access_token`` with the ``userinfo_endpoint``.
"""
return (
"openid" not in self._scopes
or self._user_profile_method == "userinfo_endpoint"
)
async def load_metadata(self, force: bool = False) -> OpenIDProviderMetadata:
"""Return the provider metadata.
If this is the first call, the metadata is built from the config and from the
metadata discovery endpoint (if enabled), and then validated. If the metadata
is successfully validated, it is then cached for future use.
Args:
force: If true, any cached metadata is discarded to force a reload.
Raises:
ValueError: if something in the provider is not valid
Returns:
The provider's metadata.
"""
if force:
# reset the cached call to ensure we get a new result
self._provider_metadata = RetryOnExceptionCachedCall(self._load_metadata)
return await self._provider_metadata.get()
async def _load_metadata(self) -> OpenIDProviderMetadata:
# start out with just the issuer (unlike the other settings, discovered issuer
# takes precedence over configured issuer, because configured issuer is
# required for discovery to take place.)
#
metadata = OpenIDProviderMetadata(issuer=self._config.issuer)
# load any data from the discovery endpoint, if enabled
if self._config.discover:
url = get_well_known_url(self._config.issuer, external=True)
metadata_response = await self._http_client.get_json(url)
metadata.update(metadata_response)
# override any discovered data with any settings in our config
if self._config.authorization_endpoint:
metadata["authorization_endpoint"] = self._config.authorization_endpoint
if self._config.token_endpoint:
metadata["token_endpoint"] = self._config.token_endpoint
if self._config.userinfo_endpoint:
metadata["userinfo_endpoint"] = self._config.userinfo_endpoint
if self._config.jwks_uri:
metadata["jwks_uri"] = self._config.jwks_uri
self._validate_metadata(metadata)
return metadata
async def load_jwks(self, force: bool = False) -> JWKS:
"""Load the JSON Web Key Set used to sign ID tokens.
If we're not using the ``userinfo_endpoint``, user infos are extracted
from the ID token, which is a JWT signed by keys given by the provider.
The keys are then cached.
Args:
force: Force reloading the keys.
Returns:
The key set
Looks like this::
{
'keys': [
{
'kid': 'abcdef',
'kty': 'RSA',
'alg': 'RS256',
'use': 'sig',
'e': 'XXXX',
'n': 'XXXX',
}
]
}
"""
if force:
# reset the cached call to ensure we get a new result
self._jwks = RetryOnExceptionCachedCall(self._load_jwks)
return await self._jwks.get()
async def _load_jwks(self) -> JWKS:
metadata = await self.load_metadata()
# Load the JWKS using the `jwks_uri` metadata.
uri = metadata.get("jwks_uri")
if not uri:
# this should be unreachable: load_metadata validates that
# there is a jwks_uri in the metadata if _uses_userinfo is unset
raise RuntimeError('Missing "jwks_uri" in metadata')
jwk_set = await self._http_client.get_json(uri)
return jwk_set
async def _exchange_code(self, code: str) -> Token:
"""Exchange an authorization code for a token.
This calls the ``token_endpoint`` with the authorization code we
received in the callback to exchange it for a token. The call uses the
``ClientAuth`` to authenticate with the client with its ID and secret.
See:
https://tools.ietf.org/html/rfc6749#section-3.2
https://openid.net/specs/openid-connect-core-1_0.html#TokenEndpoint
Args:
code: The authorization code we got from the callback.
Returns:
A dict containing various tokens.
May look like this::
{
'token_type': 'bearer',
'access_token': 'abcdef',
'expires_in': 3599,
'id_token': 'ghijkl',
'refresh_token': 'mnopqr',
}
Raises:
OidcError: when the ``token_endpoint`` returned an error.
"""
metadata = await self.load_metadata()
token_endpoint = metadata.get("token_endpoint")
raw_headers: Dict[str, str] = {
"Content-Type": "application/x-www-form-urlencoded",
"User-Agent": self._http_client.user_agent.decode("ascii"),
"Accept": "application/json",
}
args = {
"grant_type": "authorization_code",
"code": code,
"redirect_uri": self._callback_url,
}
body = urlencode(args, True)
# Fill the body/headers with credentials
uri, raw_headers, body = self._client_auth.prepare(
method="POST", uri=token_endpoint, headers=raw_headers, body=body
)
headers = Headers({k: [v] for (k, v) in raw_headers.items()})
# Do the actual request
# We're not using the SimpleHttpClient util methods as we don't want to
# check the HTTP status code and we do the body encoding ourself.
response = await self._http_client.request(
method="POST",
uri=uri,
data=body.encode("utf-8"),
headers=headers,
)
# This is used in multiple error messages below
status = "{code} {phrase}".format(
code=response.code, phrase=response.phrase.decode("utf-8")
)
resp_body = await make_deferred_yieldable(readBody(response))
if response.code >= 500:
# In case of a server error, we should first try to decode the body
# and check for an error field. If not, we respond with a generic
# error message.
try:
resp = json_decoder.decode(resp_body.decode("utf-8"))
error = resp["error"]
description = resp.get("error_description", error)
except (ValueError, KeyError):
# Catch ValueError for the JSON decoding and KeyError for the "error" field
error = "server_error"
description = (
(
'Authorization server responded with a "{status}" error '
"while exchanging the authorization code."
).format(status=status),
)
raise OidcError(error, description)
# Since it is a not a 5xx code, body should be a valid JSON. It will
# raise if not.
resp = json_decoder.decode(resp_body.decode("utf-8"))
if "error" in resp:
error = resp["error"]
# In case the authorization server responded with an error field,
# it should be a 4xx code. If not, warn about it but don't do
# anything special and report the original error message.
if response.code < 400:
logger.debug(
"Invalid response from the authorization server: "
'responded with a "{status}" '
"but body has an error field: {error!r}".format(
status=status, error=resp["error"]
)
)
description = resp.get("error_description", error)
raise OidcError(error, description)
# Now, this should not be an error. According to RFC6749 sec 5.1, it
# should be a 200 code. We're a bit more flexible than that, and will
# only throw on a 4xx code.
if response.code >= 400:
description = (
'Authorization server responded with a "{status}" error '
'but did not include an "error" field in its response.'.format(
status=status
)
)
logger.warning(description)
# Body was still valid JSON. Might be useful to log it for debugging.
logger.warning("Code exchange response: %r", resp)
raise OidcError("server_error", description)
return resp
async def _fetch_userinfo(self, token: Token) -> UserInfo:
"""Fetch user information from the ``userinfo_endpoint``.
Args:
token: the token given by the ``token_endpoint``.
Must include an ``access_token`` field.
Returns:
UserInfo: an object representing the user.
"""
logger.debug("Using the OAuth2 access_token to request userinfo")
metadata = await self.load_metadata()
resp = await self._http_client.get_json(
metadata["userinfo_endpoint"],
headers={"Authorization": ["Bearer {}".format(token["access_token"])]},
)
logger.debug("Retrieved user info from userinfo endpoint: %r", resp)
return UserInfo(resp)
async def _parse_id_token(self, token: Token, nonce: str) -> CodeIDToken:
"""Return an instance of UserInfo from token's ``id_token``.
Args:
token: the token given by the ``token_endpoint``.
Must include an ``id_token`` field.
nonce: the nonce value originally sent in the initial authorization
request. This value should match the one inside the token.
Returns:
The decoded claims in the ID token.
"""
metadata = await self.load_metadata()
claims_params = {
"nonce": nonce,
"client_id": self._client_auth.client_id,
}
if "access_token" in token:
# If we got an `access_token`, there should be an `at_hash` claim
# in the `id_token` that we can check against.
claims_params["access_token"] = token["access_token"]
alg_values = metadata.get("id_token_signing_alg_values_supported", ["RS256"])
jwt = JsonWebToken(alg_values)
claim_options = {"iss": {"values": [metadata["issuer"]]}}
id_token = token["id_token"]
logger.debug("Attempting to decode JWT id_token %r", id_token)
# Try to decode the keys in cache first, then retry by forcing the keys
# to be reloaded
jwk_set = await self.load_jwks()
try:
claims = jwt.decode(
id_token,
key=jwk_set,
claims_cls=CodeIDToken,
claims_options=claim_options,
claims_params=claims_params,
)
except ValueError:
logger.info("Reloading JWKS after decode error")
jwk_set = await self.load_jwks(force=True) # try reloading the jwks
claims = jwt.decode(
id_token,
key=jwk_set,
claims_cls=CodeIDToken,
claims_options=claim_options,
claims_params=claims_params,
)
logger.debug("Decoded id_token JWT %r; validating", claims)
claims.validate(leeway=120) # allows 2 min of clock skew
return claims
async def handle_redirect_request(
self,
request: SynapseRequest,
client_redirect_url: Optional[bytes],
ui_auth_session_id: Optional[str] = None,
) -> str:
"""Handle an incoming request to /login/sso/redirect
It returns a redirect to the authorization endpoint with a few
parameters:
- ``client_id``: the client ID set in ``oidc_config.client_id``
- ``response_type``: ``code``
- ``redirect_uri``: the callback URL ; ``{base url}/_synapse/client/oidc/callback``
- ``scope``: the list of scopes set in ``oidc_config.scopes``
- ``state``: a random string
- ``nonce``: a random string
In addition generating a redirect URL, we are setting a cookie with
a signed macaroon token containing the state, the nonce and the
client_redirect_url params. Those are then checked when the client
comes back from the provider.
Args:
request: the incoming request from the browser.
We'll respond to it with a redirect and a cookie.
client_redirect_url: the URL that we should redirect the client to
when everything is done (or None for UI Auth)
ui_auth_session_id: The session ID of the ongoing UI Auth (or
None if this is a login).
Returns:
The redirect URL to the authorization endpoint.
"""
state = generate_token()
nonce = generate_token()
if not client_redirect_url:
client_redirect_url = b""
cookie = self._macaroon_generaton.generate_oidc_session_token(
state=state,
session_data=OidcSessionData(
idp_id=self.idp_id,
nonce=nonce,
client_redirect_url=client_redirect_url.decode(),
ui_auth_session_id=ui_auth_session_id or "",
),
)
# Set the cookies. See the comments on _SESSION_COOKIES for why there are two.
#
# we have to build the header by hand rather than calling request.addCookie
# because the latter does not support SameSite=None
# (https://twistedmatrix.com/trac/ticket/10088)
for cookie_name, options in _SESSION_COOKIES:
request.cookies.append(
b"%s=%s; Max-Age=3600; Path=%s; %s"
% (
cookie_name,
cookie.encode("utf-8"),
self._callback_path_prefix,
options,
)
)
metadata = await self.load_metadata()
authorization_endpoint = metadata.get("authorization_endpoint")
return prepare_grant_uri(
authorization_endpoint,
client_id=self._client_auth.client_id,
response_type="code",
redirect_uri=self._callback_url,
scope=self._scopes,
state=state,
nonce=nonce,
)
async def handle_oidc_callback(
self, request: SynapseRequest, session_data: "OidcSessionData", code: str
) -> None:
"""Handle an incoming request to /_synapse/client/oidc/callback
By this time we have already validated the session on the synapse side, and
now need to do the provider-specific operations. This includes:
- exchange the code with the provider using the ``token_endpoint`` (see
``_exchange_code``)
- once we have the token, use it to either extract the UserInfo from
the ``id_token`` (``_parse_id_token``), or use the ``access_token``
to fetch UserInfo from the ``userinfo_endpoint``
(``_fetch_userinfo``)
- map those UserInfo to a Matrix user (``_map_userinfo_to_user``) and
finish the login
Args:
request: the incoming request from the browser.
session_data: the session data, extracted from our cookie
code: The authorization code we got from the callback.
"""
# Exchange the code with the provider
try:
logger.debug("Exchanging OAuth2 code for a token")
token = await self._exchange_code(code)
except OidcError as e:
logger.warning("Could not exchange OAuth2 code: %s", e)
self._sso_handler.render_error(request, e.error, e.error_description)
return
logger.debug("Successfully obtained OAuth2 token data: %r", token)
# If there is an id_token, it should be validated, regardless of the
# userinfo endpoint is used or not.
if token.get("id_token") is not None:
try:
id_token = await self._parse_id_token(token, nonce=session_data.nonce)
sid = id_token.get("sid")
except Exception as e:
logger.exception("Invalid id_token")
self._sso_handler.render_error(request, "invalid_token", str(e))
return
else:
id_token = None
sid = None
# Now that we have a token, get the userinfo either from the `id_token`
# claims or by fetching the `userinfo_endpoint`.
if self._uses_userinfo:
try:
userinfo = await self._fetch_userinfo(token)
except Exception as e:
logger.exception("Could not fetch userinfo")
self._sso_handler.render_error(request, "fetch_error", str(e))
return
elif id_token is not None:
userinfo = UserInfo(id_token)
else:
logger.error("Missing id_token in token response")
self._sso_handler.render_error(
request, "invalid_token", "Missing id_token in token response"
)
return
# first check if we're doing a UIA
if session_data.ui_auth_session_id:
try:
remote_user_id = self._remote_id_from_userinfo(userinfo)
except Exception as e:
logger.exception("Could not extract remote user id")
self._sso_handler.render_error(request, "mapping_error", str(e))
return
return await self._sso_handler.complete_sso_ui_auth_request(
self.idp_id, remote_user_id, session_data.ui_auth_session_id, request
)
# otherwise, it's a login
logger.debug("Userinfo for OIDC login: %s", userinfo)
# Ensure that the attributes of the logged in user meet the required
# attributes by checking the userinfo against attribute_requirements
# In order to deal with the fact that OIDC userinfo can contain many
# types of data, we wrap non-list values in lists.
if not self._sso_handler.check_required_attributes(
request,
{k: v if isinstance(v, list) else [v] for k, v in userinfo.items()},
self._oidc_attribute_requirements,
):
return
# Call the mapper to register/login the user
try:
await self._complete_oidc_login(
userinfo, token, request, session_data.client_redirect_url, sid
)
except MappingException as e:
logger.exception("Could not map user")
self._sso_handler.render_error(request, "mapping_error", str(e))
async def _complete_oidc_login(
self,
userinfo: UserInfo,
token: Token,
request: SynapseRequest,
client_redirect_url: str,
sid: Optional[str],
) -> None:
"""Given a UserInfo response, complete the login flow
UserInfo should have a claim that uniquely identifies users. This claim
is usually `sub`, but can be configured with `oidc_config.subject_claim`.
It is then used as an `external_id`.
If we don't find the user that way, we should register the user,
mapping the localpart and the display name from the UserInfo.
If a user already exists with the mxid we've mapped and allow_existing_users
is disabled, raise an exception.
Otherwise, render a redirect back to the client_redirect_url with a loginToken.
Args:
userinfo: an object representing the user
token: a dict with the tokens obtained from the provider
request: The request to respond to
client_redirect_url: The redirect URL passed in by the client.
Raises:
MappingException: if there was an error while mapping some properties
"""
try:
remote_user_id = self._remote_id_from_userinfo(userinfo)
except Exception as e:
raise MappingException(
"Failed to extract subject from OIDC response: %s" % (e,)
)
# Older mapping providers don't accept the `failures` argument, so we
# try and detect support.
mapper_signature = inspect.signature(
self._user_mapping_provider.map_user_attributes
)
supports_failures = "failures" in mapper_signature.parameters
async def oidc_response_to_user_attributes(failures: int) -> UserAttributes:
"""
Call the mapping provider to map the OIDC userinfo and token to user attributes.
This is backwards compatibility for abstraction for the SSO handler.
"""
if supports_failures:
attributes = await self._user_mapping_provider.map_user_attributes(
userinfo, token, failures
)
else:
# If the mapping provider does not support processing failures,
# do not continually generate the same Matrix ID since it will
# continue to already be in use. Note that the error raised is
# arbitrary and will get turned into a MappingException.
if failures:
raise MappingException(
"Mapping provider does not support de-duplicating Matrix IDs"
)
attributes = await self._user_mapping_provider.map_user_attributes(
userinfo, token
)
return UserAttributes(**attributes)
async def grandfather_existing_users() -> Optional[str]:
if self._allow_existing_users:
# If allowing existing users we want to generate a single localpart
# and attempt to match it.
attributes = await oidc_response_to_user_attributes(failures=0)
if attributes.localpart is None:
# If no localpart is returned then we will generate one, so
# there is no need to search for existing users.
return None
user_id = UserID(attributes.localpart, self._server_name).to_string()
users = await self._store.get_users_by_id_case_insensitive(user_id)
if users:
# If an existing matrix ID is returned, then use it.
if len(users) == 1:
previously_registered_user_id = next(iter(users))
elif user_id in users:
previously_registered_user_id = user_id
else:
# Do not attempt to continue generating Matrix IDs.
raise MappingException(
"Attempted to login as '{}' but it matches more than one user inexactly: {}".format(
user_id, users
)
)
return previously_registered_user_id
return None
# Mapping providers might not have get_extra_attributes: only call this
# method if it exists.
extra_attributes = None
get_extra_attributes = getattr(
self._user_mapping_provider, "get_extra_attributes", None
)
if get_extra_attributes:
extra_attributes = await get_extra_attributes(userinfo, token)
await self._sso_handler.complete_sso_login_request(
self.idp_id,
remote_user_id,
request,
client_redirect_url,
oidc_response_to_user_attributes,
grandfather_existing_users,
extra_attributes,
auth_provider_session_id=sid,
)
def _remote_id_from_userinfo(self, userinfo: UserInfo) -> str:
"""Extract the unique remote id from an OIDC UserInfo block
Args:
userinfo: An object representing the user given by the OIDC provider
Returns:
remote user id
"""
remote_user_id = self._user_mapping_provider.get_remote_user_id(userinfo)
# Some OIDC providers use integer IDs, but Synapse expects external IDs
# to be strings.
return str(remote_user_id)
# number of seconds a newly-generated client secret should be valid for
CLIENT_SECRET_VALIDITY_SECONDS = 3600
# minimum remaining validity on a client secret before we should generate a new one
CLIENT_SECRET_MIN_VALIDITY_SECONDS = 600
class JwtClientSecret:
"""A class which generates a new client secret on demand, based on a JWK
This implementation is designed to comply with the requirements for Apple Sign in:
https://developer.apple.com/documentation/sign_in_with_apple/generate_and_validate_tokens#3262048
It looks like those requirements are based on https://tools.ietf.org/html/rfc7523,
but it's worth noting that we still put the generated secret in the "client_secret"
field (or rather, whereever client_auth_method puts it) rather than in a
client_assertion field in the body as that RFC seems to require.
"""
def __init__(
self,
key: OidcProviderClientSecretJwtKey,
oauth_client_id: str,
oauth_issuer: str,
clock: Clock,
):
self._key = key
self._oauth_client_id = oauth_client_id
self._oauth_issuer = oauth_issuer
self._clock = clock
self._cached_secret = b""
self._cached_secret_replacement_time = 0
def __str__(self) -> str:
# if client_auth_method is client_secret_basic, then ClientAuth.prepare calls
# encode_client_secret_basic, which calls "{}".format(secret), which ends up
# here.
return self._get_secret().decode("ascii")
def __bytes__(self) -> bytes:
# if client_auth_method is client_secret_post, then ClientAuth.prepare calls
# encode_client_secret_post, which ends up here.
return self._get_secret()
def _get_secret(self) -> bytes:
now = self._clock.time()
# if we have enough validity on our existing secret, use it
if now < self._cached_secret_replacement_time:
return self._cached_secret
issued_at = int(now)
expires_at = issued_at + CLIENT_SECRET_VALIDITY_SECONDS
# we copy the configured header because jwt.encode modifies it.
header = dict(self._key.jwt_header)
# see https://tools.ietf.org/html/rfc7523#section-3
payload = {
"sub": self._oauth_client_id,
"aud": self._oauth_issuer,
"iat": issued_at,
"exp": expires_at,
**self._key.jwt_payload,
}
logger.info(
"Generating new JWT for %s: %s %s", self._oauth_issuer, header, payload
)
self._cached_secret = jwt.encode(header, payload, self._key.key)
self._cached_secret_replacement_time = (
expires_at - CLIENT_SECRET_MIN_VALIDITY_SECONDS
)
return self._cached_secret
class UserAttributeDict(TypedDict):
localpart: Optional[str]
confirm_localpart: bool
display_name: Optional[str]
emails: List[str]
C = TypeVar("C")
class OidcMappingProvider(Generic[C]):
"""A mapping provider maps a UserInfo object to user attributes.
It should provide the API described by this class.
"""
def __init__(self, config: C):
"""
Args:
config: A custom config object from this module, parsed by ``parse_config()``
"""
@staticmethod
def parse_config(config: dict) -> C:
"""Parse the dict provided by the homeserver's config
Args:
config: A dictionary containing configuration options for this provider
Returns:
A custom config object for this module
"""
raise NotImplementedError()
def get_remote_user_id(self, userinfo: UserInfo) -> str:
"""Get a unique user ID for this user.
Usually, in an OIDC-compliant scenario, it should be the ``sub`` claim from the UserInfo object.
Args:
userinfo: An object representing the user given by the OIDC provider
Returns:
A unique user ID
"""
raise NotImplementedError()
async def map_user_attributes(
self, userinfo: UserInfo, token: Token, failures: int
) -> UserAttributeDict:
"""Map a `UserInfo` object into user attributes.
Args:
userinfo: An object representing the user given by the OIDC provider
token: A dict with the tokens returned by the provider
failures: How many times a call to this function with this
UserInfo has resulted in a failure.
Returns:
A dict containing the ``localpart`` and (optionally) the ``display_name``
"""
raise NotImplementedError()
async def get_extra_attributes(self, userinfo: UserInfo, token: Token) -> JsonDict:
"""Map a `UserInfo` object into additional attributes passed to the client during login.
Args:
userinfo: An object representing the user given by the OIDC provider
token: A dict with the tokens returned by the provider
Returns:
A dict containing additional attributes. Must be JSON serializable.
"""
return {}
# Used to clear out "None" values in templates
def jinja_finalize(thing: Any) -> Any:
return thing if thing is not None else ""
env = Environment(finalize=jinja_finalize)
env.filters.update(
{
"localpart_from_email": _localpart_from_email_filter,
}
)
@attr.s(slots=True, frozen=True, auto_attribs=True)
class JinjaOidcMappingConfig:
subject_claim: str
localpart_template: Optional[Template]
display_name_template: Optional[Template]
email_template: Optional[Template]
extra_attributes: Dict[str, Template]
confirm_localpart: bool = False
class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]):
"""An implementation of a mapping provider based on Jinja templates.
This is the default mapping provider.
"""
def __init__(self, config: JinjaOidcMappingConfig):
self._config = config
@staticmethod
def parse_config(config: dict) -> JinjaOidcMappingConfig:
subject_claim = config.get("subject_claim", "sub")
def parse_template_config(option_name: str) -> Optional[Template]:
if option_name not in config:
return None
try:
return env.from_string(config[option_name])
except Exception as e:
raise ConfigError("invalid jinja template", path=[option_name]) from e
localpart_template = parse_template_config("localpart_template")
display_name_template = parse_template_config("display_name_template")
email_template = parse_template_config("email_template")
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("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", path=["extra_attributes", key]
) from e
confirm_localpart = config.get("confirm_localpart") or False
if not isinstance(confirm_localpart, bool):
raise ConfigError("must be a bool", path=["confirm_localpart"])
return JinjaOidcMappingConfig(
subject_claim=subject_claim,
localpart_template=localpart_template,
display_name_template=display_name_template,
email_template=email_template,
extra_attributes=extra_attributes,
confirm_localpart=confirm_localpart,
)
def get_remote_user_id(self, userinfo: UserInfo) -> str:
return userinfo[self._config.subject_claim]
async def map_user_attributes(
self, userinfo: UserInfo, token: Token, failures: int
) -> UserAttributeDict:
localpart = None
if self._config.localpart_template:
localpart = self._config.localpart_template.render(user=userinfo).strip()
# 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 ""
def render_template_field(template: Optional[Template]) -> Optional[str]:
if template is None:
return None
return template.render(user=userinfo).strip()
display_name = render_template_field(self._config.display_name_template)
if display_name == "":
display_name = None
emails: List[str] = []
email = render_template_field(self._config.email_template)
if email:
emails.append(email)
return UserAttributeDict(
localpart=localpart,
display_name=display_name,
emails=emails,
confirm_localpart=self._config.confirm_localpart,
)
async def get_extra_attributes(self, userinfo: UserInfo, token: Token) -> JsonDict:
extras: Dict[str, str] = {}
for key, template in self._config.extra_attributes.items():
try:
extras[key] = template.render(user=userinfo).strip()
except Exception as e:
# Log an error and skip this value (don't break login for this).
logger.error("Failed to render OIDC extra attribute %s: %s" % (key, e))
return extras
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