providers/oauth2: correctly fill claims_supported based on selected scopes (#4429)

* providers/oauth2: correctly fill claims_supported based on selected scopes

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

* add nonce claim

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

authentik/providers/oauth2/views/provider.py

@@ -6,6 +6,7 @@ from django.shortcuts import get_object_or_404, reverse
 from django.views import View
 from structlog.stdlib import get_logger
 
+from authentik.core.exceptions import PropertyMappingExpressionException
 from authentik.core.models import Application
 from authentik.providers.oauth2.constants import (
     ACR_AUTHENTIK_DEFAULT,
@@ -108,9 +109,13 @@ class ProviderInfoView(View):
             "scopes_supported": scopes,
             # https://openid.net/specs/openid-connect-core-1_0.html#RequestObject
             "request_parameter_supported": False,
-            # Because claims are dynamic and per-application, the only claims listed here
-            # are ones that are always set by authentik itself on every token
-            "claims_supported": [
+            "claims_supported": self.get_claims(provider),
+            "claims_parameter_supported": False,
+        }
+
+    def get_claims(self, provider: OAuth2Provider) -> list[str]:
+        """Get a list of supported claims based on configured scope mappings"""
+        default_claims = [
             "sub",
             "iss",
             "aud",
@@ -118,9 +123,25 @@ class ProviderInfoView(View):
             "iat",
             "auth_time",
             "acr",
-            ],
-            "claims_parameter_supported": False,
-        }
+            "amr",
+            "nonce",
+        ]
+        for scope in ScopeMapping.objects.filter(provider=provider).order_by("scope_name"):
+            value = None
+            try:
+                value = scope.evaluate(
+                    user=self.request.user,
+                    request=self.request,
+                    provider=provider,
+                )
+            except PropertyMappingExpressionException:
+                continue
+            if value is None:
+                continue
+            if not isinstance(value, dict):
+                continue
+            default_claims.extend(value.keys())
+        return default_claims
 
     # pylint: disable=unused-argument
     def get(self, request: HttpRequest, *args, **kwargs) -> HttpResponse:

authentik/providers/oauth2/views/userinfo.py

@@ -110,6 +110,8 @@ class UserInfoView(View):
             return HttpResponseBadRequest()
         claims = self.get_claims(self.token)
         claims["sub"] = self.token.id_token.sub
+        if self.token.id_token.nonce:
+            claims["nonce"] = self.token.id_token.nonce
         response = TokenResponse(claims)
         return response