stages/password: move password validation to serializer (#6766)

* handle non-applicable when restarting flow

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

* flows: add StageInvalidException error to be used in challenge/response serializer validation to return a stage_invalid error

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

* rework password stage

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

---------

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

authentik/flows/exceptions.py

@@ -26,3 +26,8 @@ class EmptyFlowException(SentryIgnoredException):
 
 class FlowSkipStageException(SentryIgnoredException):
     """Exception to skip a stage"""
+
+
+class StageInvalidException(SentryIgnoredException):
+    """Exception can be thrown in a `Challenge` or `ChallengeResponse` serializer's
+    validation to trigger a `executor.stage_invalid()` response"""

authentik/flows/stage.py

@@ -23,6 +23,7 @@ from authentik.flows.challenge import (
     RedirectChallenge,
     WithUserInfoChallenge,
 )
+from authentik.flows.exceptions import StageInvalidException
 from authentik.flows.models import InvalidResponseAction
 from authentik.flows.planner import PLAN_CONTEXT_APPLICATION, PLAN_CONTEXT_PENDING_USER
 from authentik.lib.avatars import DEFAULT_AVATAR
@@ -100,8 +101,14 @@ class ChallengeStageView(StageView):
 
     def post(self, request: Request, *args, **kwargs) -> HttpResponse:
         """Handle challenge response"""
+        valid = False
+        try:
             challenge: ChallengeResponse = self.get_response_instance(data=request.data)
-        if not challenge.is_valid():
+            valid = challenge.is_valid()
+        except StageInvalidException as exc:
+            self.logger.debug("Got StageInvalidException", exc=exc)
+            return self.executor.stage_invalid()
+        if not valid:
             if self.executor.current_binding.invalid_response_action in [
                 InvalidResponseAction.RESTART,
                 InvalidResponseAction.RESTART_WITH_CONTEXT,

authentik/flows/views/executor.py

@@ -362,10 +362,15 @@ class FlowExecutorView(APIView):
     def restart_flow(self, keep_context=False) -> HttpResponse:
         """Restart the currently active flow, optionally keeping the current context"""
         planner = FlowPlanner(self.flow)
+        planner.use_cache = False
         default_context = None
         if keep_context:
             default_context = self.plan.context
+        try:
             plan = planner.plan(self.request, default_context)
+        except FlowNonApplicableException as exc:
+            self._logger.warning("f(exec): Flow restart not applicable to current user", exc=exc)
+            return self.handle_invalid_flow(exc)
         self.request.session[SESSION_KEY_PLAN] = plan
         kwargs = self.kwargs
         kwargs.update({"flow_slug": self.flow.slug})

authentik/stages/password/stage.py

@@ -7,7 +7,7 @@ from django.core.exceptions import PermissionDenied
 from django.http import HttpRequest, HttpResponse
 from django.urls import reverse
 from django.utils.translation import gettext as _
-from rest_framework.exceptions import ErrorDetail, ValidationError
+from rest_framework.exceptions import ValidationError
 from rest_framework.fields import CharField
 from sentry_sdk.hub import Hub
 from structlog.stdlib import get_logger
@@ -20,6 +20,7 @@ from authentik.flows.challenge import (
     ChallengeTypes,
     WithUserInfoChallenge,
 )
+from authentik.flows.exceptions import StageInvalidException
 from authentik.flows.models import Flow, FlowDesignation, Stage
 from authentik.flows.planner import PLAN_CONTEXT_PENDING_USER
 from authentik.flows.stage import ChallengeStageView
@@ -79,9 +80,52 @@ class PasswordChallenge(WithUserInfoChallenge):
 class PasswordChallengeResponse(ChallengeResponse):
     """Password challenge response"""
 
+    component = CharField(default="ak-stage-password")
+
     password = CharField(trim_whitespace=False)
 
-    component = CharField(default="ak-stage-password")
+    def validate_password(self, password: str) -> str | None:
+        """Validate password and authenticate user"""
+        executor = self.stage.executor
+        if PLAN_CONTEXT_PENDING_USER not in executor.plan.context:
+            raise StageInvalidException("No pending user")
+        # Get the pending user's username, which is used as
+        # an Identifier by most authentication backends
+        pending_user: User = executor.plan.context[PLAN_CONTEXT_PENDING_USER]
+        auth_kwargs = {
+            "password": password,
+            "username": pending_user.username,
+        }
+        try:
+            with Hub.current.start_span(
+                op="authentik.stages.password.authenticate",
+                description="User authenticate call",
+            ):
+                user = authenticate(
+                    self.stage.request,
+                    executor.current_stage.backends,
+                    executor.current_stage,
+                    **auth_kwargs,
+                )
+        except PermissionDenied as exc:
+            del auth_kwargs["password"]
+            # User was found, but permission was denied (i.e. user is not active)
+            self.stage.logger.debug("Denied access", **auth_kwargs)
+            raise StageInvalidException("Denied access") from exc
+        except ValidationError as exc:
+            del auth_kwargs["password"]
+            # User was found, authentication succeeded, but another signal raised an error
+            # (most likely LDAP)
+            self.stage.logger.debug("Validation error from signal", exc=exc, **auth_kwargs)
+            raise StageInvalidException("Validation error") from exc
+        if not user:
+            # No user was found -> invalid credentials
+            self.stage.logger.info("Invalid credentials")
+            raise ValidationError(_("Invalid password"), "invalid")
+        # User instance returned from authenticate() has .backend property set
+        executor.plan.context[PLAN_CONTEXT_PENDING_USER] = user
+        executor.plan.context[PLAN_CONTEXT_AUTHENTICATION_BACKEND] = user.backend
+        return password
 
 
 class PasswordStageView(ChallengeStageView):
@@ -122,43 +166,4 @@ class PasswordStageView(ChallengeStageView):
         """Authenticate against django's authentication backend"""
         if PLAN_CONTEXT_PENDING_USER not in self.executor.plan.context:
             return self.executor.stage_invalid()
-        # Get the pending user's username, which is used as
-        # an Identifier by most authentication backends
-        pending_user: User = self.executor.plan.context[PLAN_CONTEXT_PENDING_USER]
-        auth_kwargs = {
-            "password": response.validated_data.get("password", None),
-            "username": pending_user.username,
-        }
-        try:
-            with Hub.current.start_span(
-                op="authentik.stages.password.authenticate",
-                description="User authenticate call",
-            ):
-                user = authenticate(
-                    self.request,
-                    self.executor.current_stage.backends,
-                    self.executor.current_stage,
-                    **auth_kwargs,
-                )
-        except PermissionDenied:
-            del auth_kwargs["password"]
-            # User was found, but permission was denied (i.e. user is not active)
-            self.logger.debug("Denied access", **auth_kwargs)
-            return self.executor.stage_invalid()
-        except ValidationError as exc:
-            del auth_kwargs["password"]
-            # User was found, authentication succeeded, but another signal raised an error
-            # (most likely LDAP)
-            self.logger.debug("Validation error from signal", exc=exc, **auth_kwargs)
-            return self.executor.stage_invalid()
-        if not user:
-            # No user was found -> invalid credentials
-            self.logger.info("Invalid credentials")
-            # Manually inject error into form
-            response._errors.setdefault("password", [])
-            response._errors["password"].append(ErrorDetail(_("Invalid password"), "invalid"))
-            return self.challenge_invalid(response)
-        # User instance returned from authenticate() has .backend property set
-        self.executor.plan.context[PLAN_CONTEXT_PENDING_USER] = user
-        self.executor.plan.context[PLAN_CONTEXT_AUTHENTICATION_BACKEND] = user.backend
         return self.executor.stage_ok()