feat: implement CSRF protection

src/ahriman/core/auth/helpers.py

@@ -22,6 +22,11 @@ try:
 except ImportError:
     aiohttp_security = None  # type: ignore[assignment]
 
+try:
+    import aiohttp_session
+except ImportError:
+    aiohttp_session = None  # type: ignore[assignment]
+
 from typing import Any
 
 
@@ -50,7 +55,7 @@ async def check_authorized(*args: Any, **kwargs: Any) -> Any:
 
     Args:
         *args(Any): argument list as provided by check_authorized function
-        **kwargs(Any): named argument list as provided by authorized_userid function
+        **kwargs(Any): named argument list as provided by check_authorized function
 
     Returns:
         Any: ``None`` in case if no aiohttp_security module found and function call otherwise
@@ -66,7 +71,7 @@ async def forget(*args: Any, **kwargs: Any) -> Any:
 
     Args:
         *args(Any): argument list as provided by forget function
-        **kwargs(Any): named argument list as provided by authorized_userid function
+        **kwargs(Any): named argument list as provided by forget function
 
     Returns:
         Any: ``None`` in case if no aiohttp_security module found and function call otherwise
@@ -76,13 +81,29 @@ async def forget(*args: Any, **kwargs: Any) -> Any:
     return None
 
 
+async def get_session(*args: Any, **kwargs: Any) -> Any:
+    """
+    handle aiohttp session methods
+
+    Args:
+        *args(Any): argument list as provided by get_session function
+        **kwargs(Any): named argument list as provided by get_session function
+
+    Returns:
+        Any: empty dictionary in case if no aiohttp_session module found and function call otherwise
+    """
+    if aiohttp_session is not None:
+        return await aiohttp_session.get_session(*args, **kwargs)
+    return {}
+
+
 async def remember(*args: Any, **kwargs: Any) -> Any:
     """
     handle disabled auth
 
     Args:
         *args(Any): argument list as provided by remember function
-        **kwargs(Any): named argument list as provided by authorized_userid function
+        **kwargs(Any): named argument list as provided by remember function
 
     Returns:
         Any: ``None`` in case if no aiohttp_security module found and function call otherwise

src/ahriman/core/auth/oauth.py

@@ -19,6 +19,8 @@
 #
 import aioauth_client
 
+from typing import Any
+
 from ahriman.core.auth.mapping import Mapping
 from ahriman.core.configuration import Configuration
 from ahriman.core.database import SQLite
@@ -53,7 +55,7 @@ class OAuth(Mapping):
         self.client_secret = configuration.get("auth", "client_secret")
         # in order to use OAuth feature the service must be publicity available
         # thus we expect that address is set
-        self.redirect_uri = f"""{configuration.get("web", "address")}/api/v1/login"""
+        self.redirect_uri = f"{configuration.get("web", "address")}/api/v1/login"
         self.provider = self.get_provider(configuration.get("auth", "oauth_provider"))
         # it is list, but we will have to convert to string it anyway
         self.scopes = configuration.get("auth", "oauth_scopes")
@@ -102,27 +104,35 @@ class OAuth(Mapping):
         """
         return self.provider(client_id=self.client_id, client_secret=self.client_secret)
 
-    def get_oauth_url(self) -> str:
+    def get_oauth_url(self, state: str) -> str:
         """
         get authorization URI for the specified settings
 
+        Args:
+            state(str): CSRF token to pass to OAuth2 provider
+
         Returns:
             str: authorization URI as a string
         """
         client = self.get_client()
-        uri: str = client.get_authorize_url(scope=self.scopes, redirect_uri=self.redirect_uri)
+        uri: str = client.get_authorize_url(scope=self.scopes, redirect_uri=self.redirect_uri, state=state)
         return uri
 
-    async def get_oauth_username(self, code: str) -> str | None:
+    async def get_oauth_username(self, code: str, state: str | None, session: dict[str, Any]) -> str | None:
         """
         extract OAuth username from remote
 
         Args:
             code(str): authorization code provided by external service
+            state(str | None): CSRF token returned by external service
+            session(dict[str, Any]): current session instance
 
         Returns:
             str | None: username as is in OAuth provider
         """
+        if state is None or state != session.get("state"):
+            return None
+
         try:
             client = self.get_client()
             access_token, _ = await client.get_access_token(code, redirect_uri=self.redirect_uri)

src/ahriman/web/schemas/oauth2_schema.py

@@ -28,3 +28,6 @@ class OAuth2Schema(Schema):
     code = fields.String(metadata={
         "description": "OAuth2 authorization code. In case if not set, the redirect to provider will be initiated",
     })
+    state = fields.String(metadata={
+        "description": "CSRF token returned by OAuth2 provider",
+    })

src/ahriman/web/views/v1/user/login.py

@@ -18,9 +18,10 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 #
 from aiohttp.web import HTTPBadRequest, HTTPFound, HTTPMethodNotAllowed, HTTPUnauthorized
+from secrets import token_urlsafe
 from typing import ClassVar
 
-from ahriman.core.auth.helpers import remember
+from ahriman.core.auth.helpers import get_session, remember
 from ahriman.models.user_access import UserAccess
 from ahriman.web.apispec.decorators import apidocs
 from ahriman.web.schemas import LoginSchema, OAuth2Schema
@@ -68,15 +69,18 @@ class LoginView(BaseView):
             raise HTTPMethodNotAllowed(self.request.method, ["POST"])
 
         oauth_provider = self.validator
-        if not isinstance(oauth_provider, OAuth):  # there is actually property, but mypy does not like it anyway
+        if not isinstance(oauth_provider, OAuth):
             raise HTTPMethodNotAllowed(self.request.method, ["POST"])
 
+        session = await get_session(self.request)
+
         code = self.request.query.get("code")
         if not code:
-            raise HTTPFound(oauth_provider.get_oauth_url())
+            state = session["state"] = token_urlsafe()
+            raise HTTPFound(oauth_provider.get_oauth_url(state))
 
         response = HTTPFound("/")
-        identity = await oauth_provider.get_oauth_username(code)
+        identity = await oauth_provider.get_oauth_username(code, self.request.query.get("state"), session)
         if identity is not None and await self.validator.known_username(identity):
             await remember(self.request, response, identity)
             raise response