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# Copyright 2023 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.
from typing import TYPE_CHECKING
from authlib.jose import JsonWebToken, JWTClaims
from authlib.jose.errors import BadSignatureError, InvalidClaimError, JoseError
from synapse.api.errors import Codes, LoginError
from synapse.types import JsonDict, UserID
if TYPE_CHECKING:
from synapse.server import HomeServer
class JwtHandler:
def __init__(self, hs: "HomeServer"):
self.hs = hs
self.jwt_secret = hs.config.jwt.jwt_secret
self.jwt_subject_claim = hs.config.jwt.jwt_subject_claim
self.jwt_algorithm = hs.config.jwt.jwt_algorithm
self.jwt_issuer = hs.config.jwt.jwt_issuer
self.jwt_audiences = hs.config.jwt.jwt_audiences
def validate_login(self, login_submission: JsonDict) -> str:
"""
Authenticates the user for the /login API
Args:
login_submission: the whole of the login submission
(including 'type' and other relevant fields)
Returns:
The user ID that is logging in.
Raises:
LoginError if there was an authentication problem.
"""
token = login_submission.get("token", None)
if token is None:
raise LoginError(
403, "Token field for JWT is missing", errcode=Codes.FORBIDDEN
)
jwt = JsonWebToken([self.jwt_algorithm])
claim_options = {}
if self.jwt_issuer is not None:
claim_options["iss"] = {"value": self.jwt_issuer, "essential": True}
if self.jwt_audiences is not None:
claim_options["aud"] = {"values": self.jwt_audiences, "essential": True}
try:
claims = jwt.decode(
token,
key=self.jwt_secret,
claims_cls=JWTClaims,
claims_options=claim_options,
)
except BadSignatureError:
# We handle this case separately to provide a better error message
raise LoginError(
403,
"JWT validation failed: Signature verification failed",
errcode=Codes.FORBIDDEN,
)
except JoseError as e:
# A JWT error occurred, return some info back to the client.
raise LoginError(
403,
"JWT validation failed: %s" % (str(e),),
errcode=Codes.FORBIDDEN,
)
try:
claims.validate(leeway=120) # allows 2 min of clock skew
# Enforce the old behavior which is rolled out in productive
# servers: if the JWT contains an 'aud' claim but none is
# configured, the login attempt will fail
if claims.get("aud") is not None:
if self.jwt_audiences is None or len(self.jwt_audiences) == 0:
raise InvalidClaimError("aud")
except JoseError as e:
raise LoginError(
403,
"JWT validation failed: %s" % (str(e),),
errcode=Codes.FORBIDDEN,
)
user = claims.get(self.jwt_subject_claim, None)
if user is None:
raise LoginError(403, "Invalid JWT", errcode=Codes.FORBIDDEN)
return UserID(user, self.hs.hostname).to_string()
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