Add config option for always using "userinfo endpoint" for OIDC (#7658)

This allows for connecting to certain IdPs, e.g. GitLab.

2 files changed, 16 insertions, 4 deletions

diff --git a/synapse/config/oidc_config.py b/synapse/config/oidc_config.py
index f924116819..7597fbc864 100644
--- a/synapse/config/oidc_config.py
+++ b/synapse/config/oidc_config.py
@@ -56,6 +56,7 @@ class OIDCConfig(Config):
         self.oidc_userinfo_endpoint = oidc_config.get("userinfo_endpoint")
         self.oidc_jwks_uri = oidc_config.get("jwks_uri")
         self.oidc_skip_verification = oidc_config.get("skip_verification", False)
+        self.oidc_user_profile_method = oidc_config.get("user_profile_method", "auto")
         self.oidc_allow_existing_users = oidc_config.get("allow_existing_users", False)
 
         ump_config = oidc_config.get("user_mapping_provider", {})
@@ -159,6 +160,14 @@ class OIDCConfig(Config):
           #
           #skip_verification: true
 
+          # Whether to fetch the user profile from the userinfo endpoint. Valid
+          # values are: "auto" or "userinfo_endpoint".
+          #
+          # Defaults to "auto", which fetches the userinfo endpoint if "openid" is included
+          # in `scopes`. Uncomment the following to always fetch the userinfo endpoint.
+          #
+          #user_profile_method: "userinfo_endpoint"
+
           # Uncomment to allow a user logging in via OIDC to match a pre-existing account instead
           # of failing. This could be used if switching from password logins to OIDC. Defaults to false.
           #
diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index 19cd652675..05ac86e697 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -96,6 +96,7 @@ class OidcHandler:
         self.hs = hs
         self._callback_url = hs.config.oidc_callback_url  # type: str
         self._scopes = hs.config.oidc_scopes  # type: List[str]
+        self._user_profile_method = hs.config.oidc_user_profile_method  # type: str
         self._client_auth = ClientAuth(
             hs.config.oidc_client_id,
             hs.config.oidc_client_secret,
@@ -196,11 +197,11 @@ class OidcHandler:
                     % (m["response_types_supported"],)
                 )
 
-        # If the openid scope was not requested, we need a userinfo endpoint to fetch user infos
+        # 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 because the "openid" scope is not requested'
+                    '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
@@ -220,8 +221,10 @@ class OidcHandler:
         ``access_token`` with the ``userinfo_endpoint``.
         """
 
-        # Maybe that should be user-configurable and not inferred?
-        return "openid" not in self._scopes
+        return (
+            "openid" not in self._scopes
+            or self._user_profile_method == "userinfo_endpoint"
+        )
 
     async def load_metadata(self) -> OpenIDProviderMetadata:
         """Load and validate the provider metadata.