security: fix CVE 2022 46172 (#4275)

* fallback to current user in user_write, add flag to disable user creation

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* update api and web ui

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* update default flows

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* add cve post to website

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* add tests

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/stages/user_write/api.py

@@ -15,6 +15,7 @@ class UserWriteStageSerializer(StageSerializer):
         fields = StageSerializer.Meta.fields + [
             "create_users_as_inactive",
             "create_users_group",
+            "can_create_users",
             "user_path_template",
         ]
 

authentik/stages/user_write/migrations/0006_userwritestage_can_create_users.py

@@ -0,0 +1,21 @@
+# Generated by Django 4.1.4 on 2022-12-22 14:30
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("authentik_stages_user_write", "0005_userwritestage_user_path_template"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="userwritestage",
+            name="can_create_users",
+            field=models.BooleanField(
+                default=True,
+                help_text="When set, this stage can create users. If not enabled and no user is available, stage will fail.",
+            ),
+        ),
+    ]

authentik/stages/user_write/models.py

@@ -13,6 +13,16 @@ class UserWriteStage(Stage):
     """Writes currently pending data into the pending user, or if no user exists,
     creates a new user with the data."""
 
+    can_create_users = models.BooleanField(
+        default=True,
+        help_text=_(
+            (
+                "When set, this stage can create users. "
+                "If not enabled and no user is available, stage will fail."
+            )
+        ),
+    )
+
     create_users_as_inactive = models.BooleanField(
         default=False,
         help_text=_("When set, newly created users are inactive and cannot login."),

authentik/stages/user_write/stage.py

@@ -1,10 +1,9 @@
 """Write stage logic"""
-from typing import Any
+from typing import Any, Optional
 
-from django.contrib import messages
 from django.contrib.auth import update_session_auth_hash
 from django.db import transaction
-from django.db.utils import IntegrityError
+from django.db.utils import IntegrityError, InternalError
 from django.http import HttpRequest, HttpResponse
 from django.utils.translation import gettext as _
 
@@ -47,7 +46,7 @@ class UserWriteStageView(StageView):
         """Wrapper for post requests"""
         return self.get(request)
 
-    def ensure_user(self) -> tuple[User, bool]:
+    def ensure_user(self) -> tuple[Optional[User], bool]:
         """Ensure a user exists"""
         user_created = False
         path = self.executor.plan.context.get(
@@ -55,7 +54,11 @@ class UserWriteStageView(StageView):
         )
         if path == "":
             path = User.default_path()
+        if not self.request.user.is_anonymous:
+            self.executor.plan.context.setdefault(PLAN_CONTEXT_PENDING_USER, self.request.user)
         if PLAN_CONTEXT_PENDING_USER not in self.executor.plan.context:
+            if not self.executor.current_stage.can_create_users:
+                return None, False
             self.executor.plan.context[PLAN_CONTEXT_PENDING_USER] = User(
                 is_active=not self.executor.current_stage.create_users_as_inactive,
                 path=path,
@@ -110,11 +113,14 @@ class UserWriteStageView(StageView):
         a new user is created."""
         if PLAN_CONTEXT_PROMPT not in self.executor.plan.context:
             message = _("No Pending data.")
-            messages.error(request, message)
             self.logger.debug(message)
-            return self.executor.stage_invalid()
+            return self.executor.stage_invalid(message)
         data = self.executor.plan.context[PLAN_CONTEXT_PROMPT]
         user, user_created = self.ensure_user()
+        if not user:
+            message = _("No user found and can't create new user.")
+            self.logger.info(message)
+            return self.executor.stage_invalid(message)
         # Before we change anything, check if the user is the same as in the request
         # and we're updating a password. In that case we need to update the session hash
         # Also check that we're not currently impersonating, so we don't update the session
@@ -137,9 +143,9 @@ class UserWriteStageView(StageView):
                     user.ak_groups.add(self.executor.current_stage.create_users_group)
                 if PLAN_CONTEXT_GROUPS in self.executor.plan.context:
                     user.ak_groups.add(*self.executor.plan.context[PLAN_CONTEXT_GROUPS])
-        except (IntegrityError, ValueError, TypeError) as exc:
+        except (IntegrityError, ValueError, TypeError, InternalError) as exc:
             self.logger.warning("Failed to save user", exc=exc)
-            return self.executor.stage_invalid()
+            return self.executor.stage_invalid(_("Failed to save user"))
         user_write.send(sender=self, request=request, user=user, data=data, created=user_created)
         # Check if the password has been updated, and update the session auth hash
         if should_update_session:

authentik/stages/user_write/tests.py

@@ -1,6 +1,4 @@
 """write tests"""
-import string
-from random import SystemRandom
 from unittest.mock import patch
 
 from django.urls import reverse
@@ -14,6 +12,7 @@ from authentik.flows.planner import PLAN_CONTEXT_PENDING_USER, FlowPlan
 from authentik.flows.tests import FlowTestCase
 from authentik.flows.tests.test_executor import TO_STAGE_RESPONSE_MOCK
 from authentik.flows.views.executor import SESSION_KEY_PLAN
+from authentik.lib.generators import generate_key
 from authentik.stages.prompt.stage import PLAN_CONTEXT_PROMPT
 from authentik.stages.user_write.models import UserWriteStage
 from authentik.stages.user_write.stage import PLAN_CONTEXT_GROUPS, UserWriteStageView
@@ -32,12 +31,11 @@ class TestUserWriteStage(FlowTestCase):
         )
         self.binding = FlowStageBinding.objects.create(target=self.flow, stage=self.stage, order=2)
         self.source = Source.objects.create(name="fake_source")
+        self.user = create_test_admin_user()
 
     def test_user_create(self):
         """Test creation of user"""
-        password = "".join(
-            SystemRandom().choice(string.ascii_uppercase + string.digits) for _ in range(8)
-        )
+        password = generate_key()
 
         plan = FlowPlan(flow_pk=self.flow.pk.hex, bindings=[self.binding], markers=[StageMarker()])
         plan.context[PLAN_CONTEXT_PROMPT] = {
@@ -66,9 +64,7 @@ class TestUserWriteStage(FlowTestCase):
 
     def test_user_update(self):
         """Test update of existing user"""
-        new_password = "".join(
-            SystemRandom().choice(string.ascii_uppercase + string.digits) for _ in range(8)
-        )
+        new_password = generate_key()
         plan = FlowPlan(flow_pk=self.flow.pk.hex, bindings=[self.binding], markers=[StageMarker()])
         plan.context[PLAN_CONTEXT_PENDING_USER] = User.objects.create(
             username="unittest", email="test@goauthentik.io"
@@ -142,6 +138,49 @@ class TestUserWriteStage(FlowTestCase):
             component="ak-stage-access-denied",
         )
 
+    def test_authenticated_no_user(self):
+        """Test user in session and none in plan"""
+        plan = FlowPlan(flow_pk=self.flow.pk.hex, bindings=[self.binding], markers=[StageMarker()])
+        self.client.force_login(self.user)
+        session = self.client.session
+        plan.context[PLAN_CONTEXT_PROMPT] = {
+            "username": "foo",
+            "attribute_some-custom-attribute": "test",
+            "some_ignored_attribute": "bar",
+        }
+        session[SESSION_KEY_PLAN] = plan
+        session.save()
+
+        response = self.client.get(
+            reverse("authentik_api:flow-executor", kwargs={"flow_slug": self.flow.slug})
+        )
+        self.assertStageRedirects(response, reverse("authentik_core:root-redirect"))
+        self.user.refresh_from_db()
+        self.assertEqual(self.user.username, "foo")
+
+    def test_no_create(self):
+        """Test can_create_users set to false"""
+        self.stage.can_create_users = False
+        self.stage.save()
+        plan = FlowPlan(flow_pk=self.flow.pk.hex, bindings=[self.binding], markers=[StageMarker()])
+        session = self.client.session
+        plan.context[PLAN_CONTEXT_PROMPT] = {
+            "username": "foo",
+            "attribute_some-custom-attribute": "test",
+            "some_ignored_attribute": "bar",
+        }
+        session[SESSION_KEY_PLAN] = plan
+        session.save()
+
+        response = self.client.get(
+            reverse("authentik_api:flow-executor", kwargs={"flow_slug": self.flow.slug})
+        )
+        self.assertStageResponse(
+            response,
+            self.flow,
+            component="ak-stage-access-denied",
+        )
+
     @patch(
         "authentik.flows.views.executor.to_stage_response",
         TO_STAGE_RESPONSE_MOCK,

blueprints/default/0-flow-password-change.yaml

@@ -45,6 +45,8 @@ entries:
     name: default-password-change-write
   id: default-password-change-write
   model: authentik_stages_user_write.userwritestage
+  attrs:
+    can_create_users: false
 - identifiers:
     order: 0
     stage: !KeyOf default-password-change-prompt

blueprints/default/20-flow-default-source-enrollment.yaml

@@ -57,6 +57,8 @@ entries:
     name: default-source-enrollment-write
   id: default-source-enrollment-write
   model: authentik_stages_user_write.userwritestage
+  attrs:
+    can_create_users: true
 - attrs:
     re_evaluate_policies: true
   identifiers:

blueprints/default/30-flow-default-user-settings-flow.yaml

@@ -109,6 +109,8 @@ entries:
   model: authentik_policies_expression.expressionpolicy
 - identifiers:
     name: default-user-settings-write
+  attrs:
+    can_create_users: false
   id: default-user-settings-write
   model: authentik_stages_user_write.userwritestage
 - attrs:

blueprints/default/91-flow-oobe.yaml

@@ -102,6 +102,8 @@ entries:
   identifiers:
     name: default-password-change-write
   model: authentik_stages_user_write.userwritestage
+  attrs:
+    can_create_users: false
 - attrs:
     evaluate_on_plan: true
     invalid_response_action: retry

blueprints/example/flows-enrollment-2-stage.yaml

@@ -95,7 +95,8 @@ entries:
       name: default-enrollment-user-write
     id: default-enrollment-user-write
     model: authentik_stages_user_write.userwritestage
-    attrs: {}
+    attrs:
+      can_create_users: true
   - identifiers:
       target: !KeyOf flow
       stage: !KeyOf default-enrollment-prompt-first

blueprints/example/flows-enrollment-email-verification.yaml

@@ -114,6 +114,7 @@ entries:
     model: authentik_stages_user_write.userwritestage
     attrs:
       create_users_as_inactive: true
+      can_create_users: true
   - identifiers:
       target: !KeyOf flow
       stage: !KeyOf default-enrollment-prompt-first

blueprints/example/flows-recovery-email-verification.yaml

@@ -63,6 +63,8 @@ entries:
       name: default-recovery-user-write
     id: default-recovery-user-write
     model: authentik_stages_user_write.userwritestage
+    attrs:
+      can_create_users: false
   - identifiers:
       name: default-recovery-identification
     id: default-recovery-identification

schema.yml

@@ -24574,6 +24574,10 @@ paths:
       operationId: stages_user_write_list
       description: UserWriteStage Viewset
       parameters:
+      - in: query
+        name: can_create_users
+        schema:
+          type: boolean
       - in: query
         name: create_users_as_inactive
         schema:
@@ -35042,6 +35046,10 @@ components:
           format: uuid
           nullable: true
           description: Optionally add newly created users to this group.
+        can_create_users:
+          type: boolean
+          description: When set, this stage can create users. If not enabled and no
+            user is available, stage will fail.
         user_path_template:
           type: string
     PatchedWebAuthnDeviceRequest:
@@ -38248,6 +38256,10 @@ components:
           format: uuid
           nullable: true
           description: Optionally add newly created users to this group.
+        can_create_users:
+          type: boolean
+          description: When set, this stage can create users. If not enabled and no
+            user is available, stage will fail.
         user_path_template:
           type: string
       required:
@@ -38276,6 +38288,10 @@ components:
           format: uuid
           nullable: true
           description: Optionally add newly created users to this group.
+        can_create_users:
+          type: boolean
+          description: When set, this stage can create users. If not enabled and no
+            user is available, stage will fail.
         user_path_template:
           type: string
       required:

web/src/admin/stages/user_write/UserWriteStageForm.ts

@@ -59,6 +59,21 @@ export class UserWriteStageForm extends ModelForm<UserWriteStage, string> {
             <ak-form-group .expanded=${true}>
                 <span slot="header"> ${t`Stage-specific settings`} </span>
                 <div slot="body" class="pf-c-form">
+                    <ak-form-element-horizontal name="canCreateUsers">
+                        <div class="pf-c-check">
+                            <input
+                                type="checkbox"
+                                class="pf-c-check__input"
+                                ?checked=${first(this.instance?.canCreateUsers, false)}
+                            />
+                            <label class="pf-c-check__label">
+                                ${t`Can create users`}
+                            </label>
+                        </div>
+                        <p class="pf-c-form__helper-text">
+                            ${t`When enabled, this stage has the ability to create new users. If no user is available in the flow with this disabled, the stage will fail.`}
+                        </p>
+                    </ak-form-element-horizontal>
                     <ak-form-element-horizontal name="createUsersAsInactive">
                         <div class="pf-c-check">
                             <input

web/src/user/user-settings/details/UserSettingsFlowExecutor.ts

@@ -98,13 +98,6 @@ export class UserSettingsFlowExecutor extends AKElement implements StageHost {
             if (!this.flowSlug) {
                 return;
             }
-            new FlowsApi(DEFAULT_CONFIG)
-                .flowsInstancesExecuteRetrieve({
-                    slug: this.flowSlug || "",
-                })
-                .then(() => {
-                    this.nextChallenge();
-                });
         });
     }
 

website/docs/security/CVE-2022-46172.md

@@ -0,0 +1,25 @@
+# CVE-2022-46172
+
+## Existing Authenticated Users can Create Arbitrary Accounts
+
+### Summary
+
+Any authenticated user can create an arbitrary number of accounts through the default flows. This would circumvent any policy in a situation where it is undesirable for users to create new accounts by themselves. This may also have carry over consequences to other applications being how these new basic accounts would exist throughout the SSO infrastructure. By default the newly created accounts cannot be logged into as no password reset exists by default. However password resets are likely to be enabled by most installations.
+
+### Patches
+
+authentik 2022.11.4, 2022.10.4 and 2022.12.0 fix this issue.
+
+### Impact
+
+This vulnerability could make it much easier for name and email collisions to occur, making it harder for user to log in. This also makes it more difficult for admins to properly administer users since more and more confusing users will exist. This paired with password reset flows if enabled would mean a circumvention of on-boarding policies. Say for instance a company wanted to invite a limited number of beta testers, those beta testers would be able to create an arbitrary number of accounts themselves.
+
+### Details
+
+This vulnerability has already been submitted over email, this security advisory serves as formalization towards broader information dissemination. This vulnerability pertains to the user context used in the default-user-settings-flow. /api/v3/flows/instances/default-user-settings-flow/execute/
+
+### For more information
+
+If you have any questions or comments about this advisory:
+
+-   Email us at [security@goauthentik.io](mailto:security@goauthentik.io)

website/sidebars.js

@@ -290,7 +290,11 @@ module.exports = {
                 title: "Security",
                 slug: "security",
             },
-            items: ["security/policy", "security/CVE-2022-46145"],
+            items: [
+                "security/policy",
+                "security/CVE-2022-46145",
+                "security/CVE-2022-46172",
+            ],
         },
     ],
 };