From c7af7b7f95b33e43f7dc65e856a66633d30b1986 Mon Sep 17 00:00:00 2001
From: Hannes Hansen <mail@hannesh.de>
Date: Fri, 25 Oct 2024 14:31:41 +0200
Subject: [PATCH] added token validation for api auth; fix #44

---
 mlflow_oidc_auth/config.py |  5 +++
 mlflow_oidc_auth/views.py  | 73 ++++++++++++++++++++++++++++++++++++--
 pyproject.toml             |  1 +
 3 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/mlflow_oidc_auth/config.py b/mlflow_oidc_auth/config.py
index 1121d78..0590b27 100644
--- a/mlflow_oidc_auth/config.py
+++ b/mlflow_oidc_auth/config.py
@@ -34,6 +34,11 @@ class AppConfig:
     OIDC_REDIRECT_URI = os.environ.get("OIDC_REDIRECT_URI", None)
     OIDC_CLIENT_ID = os.environ.get("OIDC_CLIENT_ID", None)
     OIDC_CLIENT_SECRET = os.environ.get("OIDC_CLIENT_SECRET", None)
+    OIDC_AUDIENCE = os.environ.get("OIDC_AUDIENCE", None)
+    OIDC_PUBLIC_KEYS_URL = os.environ.get("OIDC_PUBLIC_KEYS_URL", None)
+    OIDC_USERNAME_TOKEN_ATTRIBUTE = os.environ.get("OIDC_USERNAME_TOKEN_ATTRIBUTE", "email")
+    OIDC_SIGNING_ALG = os.environ.get("OIDC_SIGNING_ALG", None) # ES256, EdDSA, PS256, RS256, HS256
+    OIDC_HS256_SECRET = os.environ.get("OIDC_HS256_SECRET", None) # ES256, EdDSA, PS256, RS256, HS256
 
     # https://flask-session.readthedocs.io/en/latest/config.html
     SESSION_TYPE = os.environ.get("SESSION_TYPE", "filesystem")
diff --git a/mlflow_oidc_auth/views.py b/mlflow_oidc_auth/views.py
index 88df955..ecacb8b 100644
--- a/mlflow_oidc_auth/views.py
+++ b/mlflow_oidc_auth/views.py
@@ -1,3 +1,4 @@
+import json
 import os
 import re
 import requests
@@ -96,6 +97,8 @@
 
 from mlflow.server import app
 
+import jwt
+
 # Create the OAuth2 client
 auth_client = WebApplicationClient(AppConfig.get_property("OIDC_CLIENT_ID"))
 store = SqlAlchemyStore()
@@ -186,6 +189,9 @@ def _get_permission_from_store_or_default(
 
 def authenticate_request_basic_auth() -> Union[Authorization, Response]:
     username = request.authorization.username
+    if username == "" or username is None:
+        app.logger.debug("Username is not set in basic auth")
+        return False
     password = request.authorization.password
     app.logger.debug("Authenticating user %s", username)
     if store.authenticate_user(username.lower(), password):
@@ -195,6 +201,64 @@ def authenticate_request_basic_auth() -> Union[Authorization, Response]:
     else:
         app.logger.debug("User %s not authenticated", username)
         return False
+    
+
+def _get_public_keys():
+    """
+    Returns:
+        List of RSA public keys usable by PyJWT.
+    """
+    r = requests.get(AppConfig.get_property("OIDC_PUBLIC_KEYS_URL"))
+    public_keys = []
+    jwk_set = r.json()
+    for key_dict in jwk_set["keys"]:
+        public_key = jwt.algorithms.RSAAlgorithm.from_jwk(json.dumps(key_dict))
+        public_keys.append(public_key)
+    return public_keys
+
+
+def validate_token(token, key, sign_alg):
+    try:
+        token = jwt.decode(token, key=key, audience=AppConfig.get_property("OIDC_AUDIENCE"), algorithms=[sign_alg])
+    except jwt.exceptions.InvalidTokenError as e:
+        app.logger.debug(f"Token is not valid: {token}")
+        raise MlflowException(f"Token is not valid: {str(e)}")
+    username_token_attr = AppConfig.get_property("OIDC_USERNAME_TOKEN_ATTRIBUTE")
+    username = token[username_token_attr]
+    if username == "" or username is None:
+        app.logger.debug(f"username from token attribute {username_token_attr} is {username}")
+        raise MlflowException(f"Username is not set at attribute: {username_token_attr}")
+    _set_username(username)
+
+
+def authenticate_token():
+    """
+    Verify the token in the request.
+    """
+    token = request.authorization.token
+    if token == "" or token is None:
+        app.logger.debug(f"Token is not set: {token}")
+        return False
+    sign_alg = AppConfig.get_property("OIDC_SIGNING_ALG")
+    token_is_valid = False
+    if sign_alg == "HS256":
+        key = AppConfig.get_property("OIDC_HS256_SECRET")
+        try:
+            validate_token(token, key, sign_alg)
+            token_is_valid = True
+        except MlflowException as e:
+            return False
+
+    keys = _get_public_keys()
+    for key in keys:
+        try:
+            validate_token(token, key, sign_alg)
+            token_is_valid = True
+            break
+        except MlflowException as e:
+            return False
+    
+    return token_is_valid
 
 
 def _get_username():
@@ -617,8 +681,13 @@ def before_request_hook():
     if _is_unprotected_route(request.path):
         return
     if request.authorization is not None:
-        if not authenticate_request_basic_auth():
-            return make_basic_auth_response()
+        if not authenticate_token():
+            app.logger.debug("No valid token authentication found")
+            # TODO maybe return 401 here instead of basic auth response
+
+            if not authenticate_request_basic_auth():
+                app.logger.debug("No valid basic authentication found")
+                return make_basic_auth_response()
     else:
         # authentication
         if not _get_username():
diff --git a/pyproject.toml b/pyproject.toml
index c905976..6619248 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,6 +32,7 @@ dependencies = [
   "Flask-Session>=0.7.0",
   "gunicorn<24; platform_system != 'Windows'",
   "alembic<2,!=1.10.0",
+  "pyjwt[crypto]>=2.9.0,<3.0.0"
 ]
 
 [project.optional-dependencies]