Added display_name_claim in jwt_config which sets the user's display name upon registration

changelog.d/17708.feature

@@ -0,0 +1 @@
+Added the `display_name_claim` option to the JWT configuration. This option allows specifying the claim key that contains the user's display name in the JWT payload.

docs/usage/configuration/config_documentation.md

@@ -3709,6 +3709,8 @@ Additional sub-options for this setting include:
    Required if `enabled` is set to true.
 * `subject_claim`: Name of the claim containing a unique identifier for the user.
    Optional, defaults to `sub`.
+* `display_name_claim`: Name of the claim containing the display name for the user. Optional.
+   If provided, the display name will be set to the value of this claim upon first login.
 * `issuer`: The issuer to validate the "iss" claim against. Optional. If provided the
    "iss" claim will be required and validated for all JSON web tokens.
 * `audiences`: A list of audiences to validate the "aud" claim against. Optional.
@@ -3723,6 +3725,7 @@ jwt_config:
     secret: "provided-by-your-issuer"
     algorithm: "provided-by-your-issuer"
     subject_claim: "name_of_claim"
+    display_name_claim: "name_of_claim"
     issuer: "provided-by-your-issuer"
     audiences:
         - "provided-by-your-issuer"

synapse/config/jwt.py

@@ -38,6 +38,7 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
             self.jwt_algorithm = jwt_config["algorithm"]
 
             self.jwt_subject_claim = jwt_config.get("subject_claim", "sub")
+            self.jwt_display_name_claim = jwt_config.get("display_name_claim")
 
             # The issuer and audiences are optional, if provided, it is asserted
             # that the claims exist on the JWT.
@@ -49,5 +50,6 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
             self.jwt_secret = None
             self.jwt_algorithm = None
             self.jwt_subject_claim = None
+            self.jwt_display_name_claim = None
             self.jwt_issuer = None
             self.jwt_audiences = None

synapse/handlers/jwt.py

@@ -18,7 +18,7 @@
 # [This file includes modifications made by New Vector Limited]
 #
 #
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Optional, Tuple
 
 from authlib.jose import JsonWebToken, JWTClaims
 from authlib.jose.errors import BadSignatureError, InvalidClaimError, JoseError
@@ -36,11 +36,12 @@ def __init__(self, hs: "HomeServer"):
 
         self.jwt_secret = hs.config.jwt.jwt_secret
         self.jwt_subject_claim = hs.config.jwt.jwt_subject_claim
+        self.jwt_display_name_claim = hs.config.jwt.jwt_display_name_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:
+    def validate_login(self, login_submission: JsonDict) -> Tuple[str, Optional[str]]:
         """
         Authenticates the user for the /login API
 
@@ -49,7 +50,8 @@ def validate_login(self, login_submission: JsonDict) -> str:
                 (including 'type' and other relevant fields)
 
         Returns:
-            The user ID that is logging in.
+            A tuple of (user_id, display_name) of the user that is logging in.
+            If the JWT does not contain a display name, the second element of the tuple will be None.
 
         Raises:
             LoginError if there was an authentication problem.
@@ -109,4 +111,10 @@ def validate_login(self, login_submission: JsonDict) -> str:
         if user is None:
             raise LoginError(403, "Invalid JWT", errcode=Codes.FORBIDDEN)
 
-        return UserID(user, self.hs.hostname).to_string()
+        default_display_name = None
+        if self.jwt_display_name_claim:
+            display_name_claim = claims.get(self.jwt_display_name_claim, None)
+            if display_name_claim is not None:
+                default_display_name = display_name_claim
+
+        return UserID(user, self.hs.hostname).to_string(), default_display_name

synapse/rest/client/login.py

@@ -363,6 +363,7 @@ async def _complete_login(
         login_submission: JsonDict,
         callback: Optional[Callable[[LoginResponse], Awaitable[None]]] = None,
         create_non_existent_users: bool = False,
+        default_display_name: Optional[str] = None,
         ratelimit: bool = True,
         auth_provider_id: Optional[str] = None,
         should_issue_refresh_token: bool = False,
@@ -410,7 +411,8 @@ async def _complete_login(
             canonical_uid = await self.auth_handler.check_user_exists(user_id)
             if not canonical_uid:
                 canonical_uid = await self.registration_handler.register_user(
-                    localpart=UserID.from_string(user_id).localpart
+                    localpart=UserID.from_string(user_id).localpart,
+                    default_display_name=default_display_name,
                 )
             user_id = canonical_uid
 
@@ -546,11 +548,14 @@ async def _do_jwt_login(
         Returns:
             The body of the JSON response.
         """
-        user_id = self.hs.get_jwt_handler().validate_login(login_submission)
+        user_id, default_display_name = self.hs.get_jwt_handler().validate_login(
+            login_submission
+        )
         return await self._complete_login(
             user_id,
             login_submission,
             create_non_existent_users=True,
+            default_display_name=default_display_name,
             should_issue_refresh_token=should_issue_refresh_token,
             request_info=request_info,
         )