Add Default JWT Algorithms from .well-known endpoint

Author: zkayyali812

ansible_base/authentication/authenticator_plugins/oidc.py

@@ -123,7 +123,11 @@ class OpenIdConnectConfiguration(BaseAuthenticatorConfiguration):
     )
 
     JWT_ALGORITHMS = ListField(
-        help_text=_("The algorithm(s) for decoding JWT responses from the IDP."),
+        help_text=_(
+            "The algorithm(s) for decoding JWT responses from the IDP. "
+            "Leave blank to extract from the .well-known configuration (if that fails we will attempt the default algorithms). "
+            "Set to ['none'] to not use encrypted tokens (the provider must send unencrypted tokens for this to work)"
+        ),
         default=None,
         allow_null=True,
         validators=[JWTAlgorithmListFieldValidator()],
@@ -300,3 +304,56 @@ def get_alternative_uid(self, **kwargs):
             return preferred_username
 
         return None
+
+    def _discover_algorithms_from_config(self, config):
+        """
+        Discover JWT algorithms from OIDC configuration
+        """
+        # Try signing algorithms first (most common)
+        algorithms = config.get("id_token_signing_alg_values_supported")
+        if algorithms:
+            logger.debug(f"JWT signing algorithms supported by the IDP: {algorithms}")
+            return algorithms
+
+        # Fallback to encryption algorithms
+        algorithms = config.get("id_token_encryption_alg_values_supported")
+        if algorithms:
+            logger.debug(f"JWT encryption algorithms supported by the IDP: {algorithms}")
+            return algorithms
+
+        # Try userinfo signing algorithms as final fallback
+        algorithms = config.get("userinfo_signing_alg_values_supported")
+        if algorithms:
+            logger.debug(f"JWT userinfo signing algorithms supported by the IDP: {algorithms}")
+            return algorithms
+
+        return None
+
+    def _get_jwt_algorithms(self, existing_setting=None) -> list[str]:
+        """
+        Get the JWT algorithms to pass to the decode
+        """
+        if existing_setting:
+            algorithms = existing_setting
+        else:
+            try:
+                logger.debug("Attempting to get the JWT algorithms from the .well-known/openid-configuration")
+                config = self.oidc_config()
+                algorithms = self._discover_algorithms_from_config(config)
+
+                if not algorithms:
+                    raise Exception("No algorithms found in OIDC config")
+
+            except Exception as e:
+                # Fallback to default algorithms if discovery fails
+                lib_defaults = OpenIdConnectAuth.JWT_ALGORITHMS
+                logger.error(f"Unable to get JWT algorithms from the .well-known/openid-configuration, defaulting to {lib_defaults}: {e}")
+                algorithms = lib_defaults
+
+        # Ensure we always return a list
+        if not isinstance(algorithms, list):
+            algorithms = [algorithms] if algorithms else []
+
+        # Set the property for use elsewhere
+        self.JWT_ALGORITHMS = algorithms
+        return algorithms

ansible_base/authentication/models/authenticator.py

@@ -52,6 +52,31 @@ class Authenticator(UniqueNamedCommonModel):
         on_delete=SET_NULL,
     )
 
+    def save_default_jwt_algorithms(self):
+        try:
+            # Create a proper plugin instance with the database instance
+            from ansible_base.authentication.authenticator_plugins.utils import get_authenticator_class
+
+            authenticator_class = get_authenticator_class(self.type)
+            plugin_instance = authenticator_class(database_instance=self)
+
+            # Try to get algorithms from .well-known endpoint
+            import logging
+
+            logger = logging.getLogger('ansible_base.authentication.models.authenticator')
+            logger.info("Auto-populating JWT algorithms for OIDC authenticator from .well-known endpoint")
+
+            algorithms = plugin_instance._get_jwt_algorithms()
+            if algorithms:
+                self.configuration['JWT_ALGORITHMS'] = algorithms
+                logger.info(f"Successfully populated JWT algorithms: {algorithms}")
+        except Exception as e:
+            import logging
+
+            logger = logging.getLogger('ansible_base.authentication.models.authenticator')
+            logger.warning(f"Could not auto-populate JWT algorithms for OIDC authenticator: {e}")
+            # Don't fail the save operation, just log the warning
+
     def save(self, *args, **kwargs):
         from ansible_base.lib.utils.encryption import ansible_encryption
 
@@ -65,6 +90,10 @@ def save(self, *args, **kwargs):
             if field in self.configuration:
                 self.configuration[field] = ansible_encryption.encrypt_string(self.configuration[field])
 
+        # Auto-populate JWT algorithms for OIDC authenticators if not set
+        if self.type == "ansible_base.authentication.authenticator_plugins.oidc" and self.configuration and not self.configuration.get('JWT_ALGORITHMS'):
+            self.save_default_jwt_algorithms()
+
         if not self.slug:
             self.slug = generate_authenticator_slug()
         super().save(*args, **kwargs)