Default-deny access control with group flags and access enumeration

Replaces the implicit "empty allowed_groups means public" rule with
explicit default-deny across both OIDC and ForwardAuth. Adds two boolean
flags on Group — auto_assign (Keycloak-style auto-join on user create)
and admin (members can reach the admin panel) — and drops the
users.admin column entirely. Adds "Users with access" and "Accessible
applications" panels with via-group badges on the application/user show
pages.

BEHAVIOR CHANGE: a ForwardAuth app with no allowed_groups previously
bypassed authentication entirely; it now returns 403 like any other
unauthorized request. The data migration seeds an "everyone" group and
attaches it to all previously group-less apps to preserve behavior on
existing installs. An "admins" group is seeded and backfilled from any
user with the old admin column.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/controllers/admin/groups_controller_test.rb

@@ -48,5 +48,23 @@ module Admin
 
       assert_equal [app], Group.find_by(name: "new group").applications
     end
+
+    test "can mark a group as auto_assign and admin" do
+      patch admin_group_path(@group), params: {
+        group: {name: @group.name, auto_assign: "1", admin: "1"}
+      }
+
+      @group.reload
+      assert @group.auto_assign?
+      assert @group.admin?
+    end
+
+    test "cannot delete the last admin group" do
+      admins = groups(:admin_group)
+
+      delete admin_group_path(admins)
+      # Destroy was aborted by the before_destroy guard
+      assert Group.exists?(admins.id), "admin group should not have been deleted"
+    end
   end
 end

test/controllers/admin/users_controller_test.rb

@@ -0,0 +1,69 @@
+require "test_helper"
+
+module Admin
+  class UsersControllerTest < ActionDispatch::IntegrationTest
+    setup do
+      @admin = users(:two) # in admin_group via fixtures
+      sign_in_as(@admin)
+    end
+
+    test "show loads accessible applications via the user's groups" do
+      kavita = applications(:kavita_app)
+      # alice is in admin_group via fixtures; kavita is attached to admin_group via app_groups
+      get admin_user_path(users(:alice))
+      assert_response :success
+      assert_match kavita.name, response.body
+      # The "via" badge mentions the granting group name
+      assert_match groups(:admin_group).name, response.body
+    end
+
+    test "update assigns group memberships from group_ids" do
+      target = users(:bob)
+      editors = groups(:editor_group)
+      one = groups(:one)
+
+      patch admin_user_path(target), params: {
+        user: {email_address: target.email_address, group_ids: [editors.id, one.id]}
+      }
+
+      assert_redirected_to admin_users_path
+      assert_equal [editors, one].sort, target.reload.groups.sort
+    end
+
+    test "cannot remove yourself from the last admin group" do
+      # @admin (users:two) is in admin_group. Removing them via the user form
+      # while no other admin exists is blocked.
+      sole_admin = users(:two)
+      # Strip alice (the other admin) so @admin is the last one.
+      users(:alice).groups.delete(groups(:admin_group))
+
+      patch admin_user_path(sole_admin), params: {
+        user: {email_address: sole_admin.email_address, group_ids: []}
+      }
+
+      assert_response :unprocessable_entity
+      assert sole_admin.reload.admin?, "should still be admin"
+    end
+
+    test "create with auto_assign=0 skips the auto-assign callback" do
+      post admin_users_path, params: {
+        user: {email_address: "restricted@example.com"},
+        auto_assign: "0"
+      }
+
+      assert_response :redirect
+      created = User.find_by(email_address: "restricted@example.com")
+      assert_not_includes created.groups, groups(:everyone)
+    end
+
+    test "create without auto_assign param auto-joins everyone" do
+      post admin_users_path, params: {
+        user: {email_address: "newbie@example.com"}
+      }
+
+      assert_response :redirect
+      created = User.find_by(email_address: "newbie@example.com")
+      assert_includes created.groups, groups(:everyone)
+    end
+  end
+end

test/controllers/api/forward_auth_bearer_test.rb

@@ -11,6 +11,7 @@ module Api
         domain_pattern: "webdav.example.com",
         active: true
       )
+      grant_everyone_access(@app)
       @api_key = @user.api_keys.create!(name: "Test Key", application: @app)
       @token = @api_key.plaintext_token
     end

test/controllers/api/forward_auth_controller_test.rb

@@ -7,8 +7,8 @@ module Api
       @admin_user = users(:alice)
       @inactive_user = User.create!(email_address: "inactive@example.com", password: "password", status: :disabled)
       @group = groups(:admin_group)
-      @rule = Application.create!(name: "Test App", slug: "test-app", app_type: "forward_auth", domain_pattern: "test.example.com", active: true)
-      @inactive_rule = Application.create!(name: "Inactive App", slug: "inactive-app", app_type: "forward_auth", domain_pattern: "inactive.example.com", active: false)
+      @rule = grant_everyone_access(Application.create!(name: "Test App", slug: "test-app", app_type: "forward_auth", domain_pattern: "test.example.com", active: true))
+      @inactive_rule = grant_everyone_access(Application.create!(name: "Inactive App", slug: "inactive-app", app_type: "forward_auth", domain_pattern: "inactive.example.com", active: false))
     end
 
     # Authentication Tests
@@ -65,7 +65,7 @@ module Api
     end
 
     test "should return 403 when rule exists but user not in allowed groups" do
-      @rule.allowed_groups << @group
+      @rule.allowed_groups = [@group]
       sign_in_as(@user)  # User not in group
 
       get "/api/verify", headers: {"X-Forwarded-Host" => "test.example.com"}
@@ -75,7 +75,7 @@ module Api
     end
 
     test "should return 200 when user is in allowed groups" do
-      @rule.allowed_groups << @group
+      @rule.allowed_groups = [@group]
       @user.groups << @group
       sign_in_as(@user)
 
@@ -86,7 +86,7 @@ module Api
 
     # Domain Pattern Tests
     test "should match wildcard domains correctly" do
-      Application.create!(name: "Wildcard App", slug: "wildcard-app", app_type: "forward_auth", domain_pattern: "*.example.com", active: true)
+      grant_everyone_access Application.create!(name: "Wildcard App", slug: "wildcard-app", app_type: "forward_auth", domain_pattern: "*.example.com", active: true)
       sign_in_as(@user)
 
       get "/api/verify", headers: {"X-Forwarded-Host" => "app.example.com"}
@@ -101,7 +101,7 @@ module Api
     end
 
     test "should match exact domains correctly" do
-      Application.create!(name: "Exact App", slug: "exact-app", app_type: "forward_auth", domain_pattern: "api.example.com", active: true)
+      grant_everyone_access Application.create!(name: "Exact App", slug: "exact-app", app_type: "forward_auth", domain_pattern: "api.example.com", active: true)
       sign_in_as(@user)
 
       get "/api/verify", headers: {"X-Forwarded-Host" => "api.example.com"}
@@ -126,7 +126,7 @@ module Api
     end
 
     test "should return custom headers when configured" do
-      Application.create!(
+      grant_everyone_access Application.create!(
         name: "Custom App",
         slug: "custom-app",
         app_type: "forward_auth",
@@ -151,7 +151,7 @@ module Api
     end
 
     test "should return no headers when all headers disabled" do
-      Application.create!(
+      grant_everyone_access Application.create!(
         name: "No Headers App",
         slug: "no-headers-app",
         app_type: "forward_auth",
@@ -182,11 +182,19 @@ module Api
       assert_includes groups_header, "Editors"
     end
 
-    test "should not include groups header when user has no groups" do
-      @user.groups.clear  # Remove fixture groups
+    test "should not include groups header when user has no groups beyond the granting one and groups header empty" do
+      # Under default-deny the user must be in at least one group to access the app.
+      # This rewritten test verifies that when an app's headers_config disables the
+      # groups header, no x-remote-groups is sent regardless of memberships.
+      app = grant_everyone_access Application.create!(
+        name: "Headers Hidden", slug: "headers-hidden", app_type: "forward_auth",
+        domain_pattern: "hidden.example.com",
+        active: true,
+        headers_config: {groups: ""}
+      )
       sign_in_as(@user)
 
-      get "/api/verify", headers: {"X-Forwarded-Host" => "test.example.com"}
+      get "/api/verify", headers: {"X-Forwarded-Host" => "hidden.example.com"}
 
       assert_response 200
       assert_nil response.headers["x-remote-groups"]
@@ -705,7 +713,7 @@ module Api
     class FaTokenHostBindingTest < ActionDispatch::IntegrationTest
       setup do
         @user = users(:bob)
-        Application.create!(name: "Bound App", slug: "bound-app", app_type: "forward_auth", domain_pattern: "app.example.com", active: true)
+        grant_everyone_access Application.create!(name: "Bound App", slug: "bound-app", app_type: "forward_auth", domain_pattern: "app.example.com", active: true)
 
         @original_cache = Rails.cache
         Rails.cache = ActiveSupport::Cache::MemoryStore.new

test/controllers/oidc_authorization_code_security_test.rb

@@ -17,6 +17,7 @@ class OidcAuthorizationCodeSecurityTest < ActionDispatch::IntegrationTest
     @application.generate_new_client_secret!
     @plain_client_secret = @application.client_secret
     @application.save!
+    grant_everyone_access(@application)
   end
 
   def teardown

test/controllers/oidc_pkce_controller_test.rb

@@ -10,6 +10,7 @@ class OidcPkceControllerTest < ActionDispatch::IntegrationTest
       redirect_uris: ["http://localhost:4000/callback"].to_json,
       active: true
     )
+    grant_everyone_access(@application)
 
     # Sign in the user using the test helper
     sign_in_as(@user)

test/fixtures/groups.yml

@@ -11,7 +11,13 @@ two:
 admin_group:
   name: Administrators
   description: System administrators with full access
+  admin: true
 
 editor_group:
   name: Editors
   description: Content editors with limited access
+
+everyone:
+  name: everyone
+  description: Auto-assigned to new users.
+  auto_assign: true

test/fixtures/user_groups.yml

@@ -1,9 +1,28 @@
 # Read about fixtures at https://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+# All users belong to "everyone" so existing tests that create group-less apps
+# can be made compatible by attaching that group.
+
+one_everyone:
+  user: one
+  group: everyone
+two_everyone:
+  user: two
+  group: everyone
+alice_everyone:
+  user: alice
+  group: everyone
+bob_everyone:
+  user: bob
+  group: everyone
 
 alice_admin_group:
   user: alice
   group: admin_group
 
+two_admin_group:
+  user: two
+  group: admin_group
+
 bob_editor_group:
   user: bob
   group: editor_group

test/fixtures/users.yml

@@ -3,23 +3,19 @@
 one:
   email_address: one@example.com
   password_digest: <%= password_digest %>
-  admin: false
   status: 0 # active
 
 two:
   email_address: two@example.com
   password_digest: <%= password_digest %>
-  admin: true
   status: 0 # active
 
 alice:
   email_address: alice@example.com
   password_digest: <%= password_digest %>
-  admin: true
   status: 0 # active
 
 bob:
   email_address: bob@example.com
   password_digest: <%= password_digest %>
-  admin: false
   status: 0 # active

test/integration/forward_auth_advanced_test.rb

@@ -12,7 +12,7 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
   # End-to-End Authentication Flow Tests
   test "complete forward auth flow with default headers" do
     # Create an application with default headers
-    Application.create!(name: "App", slug: "app-system-test", app_type: "forward_auth", domain_pattern: "app.example.com", active: true)
+    grant_everyone_access Application.create!(name: "App", slug: "app-system-test", app_type: "forward_auth", domain_pattern: "app.example.com", active: true)
 
     # Step 1: Unauthenticated request to protected resource
     get "/api/verify", headers: {
@@ -48,14 +48,14 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
 
   test "multiple domain access with single session" do
     # Create applications for different domains
-    Application.create!(name: "App Domain", slug: "app-domain", app_type: "forward_auth", domain_pattern: "app.example.com", active: true)
-    Application.create!(
+    grant_everyone_access Application.create!(name: "App Domain", slug: "app-domain", app_type: "forward_auth", domain_pattern: "app.example.com", active: true)
+    grant_everyone_access Application.create!(
       name: "Grafana", slug: "grafana-system-test", app_type: "forward_auth",
       domain_pattern: "grafana.example.com",
       active: true,
       headers_config: {user: "X-WEBAUTH-USER", email: "X-WEBAUTH-EMAIL"}
     )
-    Application.create!(
+    grant_everyone_access Application.create!(
       name: "Metube", slug: "metube-system-test", app_type: "forward_auth",
       domain_pattern: "metube.example.com",
       active: true,
@@ -106,7 +106,7 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
     # Should have access (in allowed group)
     get "/api/verify", headers: {"X-Forwarded-Host" => "admin.example.com"}
     assert_response 200
-    assert_equal @group.name, response.headers["x-remote-groups"]
+    assert_includes response.headers["x-remote-groups"], @group.name
 
     # Add user to second group
     @user.groups << @group2
@@ -126,31 +126,27 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
     assert_response 403
   end
 
-  test "bypass mode when no groups assigned to rule" do
-    # Create bypass application (no groups)
+  test "default deny when no groups assigned to rule" do
+    # An app with no allowed_groups now denies all users (was: bypass mode).
     Application.create!(
-      name: "Public", slug: "public-system-test", app_type: "forward_auth",
-      domain_pattern: "public.example.com",
+      name: "No Groups", slug: "nogroups-system-test", app_type: "forward_auth",
+      domain_pattern: "nogroups.example.com",
       active: true
     )
 
-    # Create user with no groups
     @user.groups.clear
 
-    # Sign in
     post "/signin", params: {email_address: @user.email_address, password: "password"}
     assert_response 303
 
-    # Should have access (bypass mode)
-    get "/api/verify", headers: {"X-Forwarded-Host" => "public.example.com"}
-    assert_response 200
-    assert_equal @user.email_address, response.headers["x-remote-user"]
+    get "/api/verify", headers: {"X-Forwarded-Host" => "nogroups.example.com"}
+    assert_response 403
   end
 
   # Security System Tests
   test "session expiration and cleanup" do
     # Create test application
-    Application.create!(
+    grant_everyone_access Application.create!(
       name: "Test", slug: "test-system-test", app_type: "forward_auth",
       domain_pattern: "test.example.com",
       active: true
@@ -179,7 +175,7 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
 
   test "concurrent access with rate limiting considerations" do
     # Create wildcard application
-    Application.create!(
+    grant_everyone_access Application.create!(
       name: "Wildcard", slug: "wildcard-test", app_type: "forward_auth",
       domain_pattern: "*.example.com",
       active: true
@@ -246,7 +242,11 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
         active: true,
         headers_config: app[:headers_config]
       )
-      app[:groups].each { |group| rule.allowed_groups << group }
+      if app[:groups].any?
+        app[:groups].each { |group| rule.allowed_groups << group }
+      else
+        grant_everyone_access(rule)
+      end
       rule
     end
 
@@ -286,7 +286,7 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
     ]
 
     patterns.each_with_index do |pattern_config, idx|
-      Application.create!(
+      grant_everyone_access Application.create!(
         name: "Pattern Test #{idx}", slug: "pattern-test-#{idx}", app_type: "forward_auth",
         domain_pattern: pattern_config[:pattern],
         active: true
@@ -310,7 +310,7 @@ class ForwardAuthAdvancedTest < ActionDispatch::IntegrationTest
   # Performance System Tests
   test "system performance under load" do
     # Create test application with wildcard pattern
-    Application.create!(name: "Load Test", slug: "loadtest", app_type: "forward_auth", domain_pattern: "*.loadtest.example.com", active: true)
+    grant_everyone_access Application.create!(name: "Load Test", slug: "loadtest", app_type: "forward_auth", domain_pattern: "*.loadtest.example.com", active: true)
 
     # Sign in
     post "/signin", params: {email_address: @user.email_address, password: "password"}

test/integration/forward_auth_integration_test.rb

@@ -15,6 +15,7 @@ class ForwardAuthIntegrationTest < ActionDispatch::IntegrationTest
       domain_pattern: "test.example.com",
       active: true
     )
+    grant_everyone_access(@test_app)
   end
 
   # Basic Authentication Flow Tests
@@ -56,8 +57,8 @@ class ForwardAuthIntegrationTest < ActionDispatch::IntegrationTest
   # Domain and Rule Integration Tests
   test "different domain patterns with same session" do
     # Create test rules
-    Application.create!(name: "Wildcard App", slug: "wildcard-app", app_type: "forward_auth", domain_pattern: "*.example.com", active: true)
-    Application.create!(name: "Exact App", slug: "exact-app", app_type: "forward_auth", domain_pattern: "api.example.com", active: true)
+    grant_everyone_access Application.create!(name: "Wildcard App", slug: "wildcard-app", app_type: "forward_auth", domain_pattern: "*.example.com", active: true)
+    grant_everyone_access Application.create!(name: "Exact App", slug: "exact-app", app_type: "forward_auth", domain_pattern: "api.example.com", active: true)
 
     # Sign in
     post "/signin", params: {email_address: @user.email_address, password: "password"}
@@ -103,14 +104,14 @@ class ForwardAuthIntegrationTest < ActionDispatch::IntegrationTest
   # Header Configuration Integration Tests
   test "different header configurations with same user" do
     # Create applications with different configs
-    Application.create!(name: "Default App", slug: "default-app", app_type: "forward_auth", domain_pattern: "default.example.com", active: true)
-    Application.create!(
+    grant_everyone_access Application.create!(name: "Default App", slug: "default-app", app_type: "forward_auth", domain_pattern: "default.example.com", active: true)
+    grant_everyone_access Application.create!(
       name: "Custom App", slug: "custom-app", app_type: "forward_auth",
       domain_pattern: "custom.example.com",
       active: true,
       headers_config: {user: "X-WEBAUTH-USER", groups: "X-WEBAUTH-ROLES"}
     )
-    Application.create!(
+    grant_everyone_access Application.create!(
       name: "No Headers App", slug: "no-headers-app", app_type: "forward_auth",
       domain_pattern: "noheaders.example.com",
       active: true,
@@ -196,7 +197,7 @@ class ForwardAuthIntegrationTest < ActionDispatch::IntegrationTest
     admin_user = users(:two)
 
     # Create restricted rule
-    Application.create!(
+    grant_everyone_access Application.create!(
       name: "Admin App", slug: "admin-app", app_type: "forward_auth",
       domain_pattern: "admin.example.com",
       active: true,

test/models/api_key_test.rb

@@ -10,6 +10,7 @@ class ApiKeyTest < ActiveSupport::TestCase
       domain_pattern: "webdav.example.com",
       active: true
     )
+    @app.allowed_groups << groups(:everyone)
   end
 
   test "generates clk_ prefixed token on create" do
@@ -78,9 +79,8 @@ class ApiKeyTest < ActiveSupport::TestCase
   end
 
   test "validates user must have access to application" do
-    group = groups(:admin_group)
-    @app.allowed_groups << group
-    # @user (bob) is not in admin_group
+    # Restrict the app to admin_group only — bob is not in admin_group.
+    @app.allowed_groups = [groups(:admin_group)]
     key = @user.api_keys.build(name: "No Access", application: @app)
     assert_not key.valid?
     assert_includes key.errors[:user], "does not have access to this application"

test/models/user_test.rb

@@ -135,23 +135,36 @@ class UserTest < ActiveSupport::TestCase
     assert_equal user, found_user
   end
 
-  test "admin scope" do
-    admin_user = User.create!(
-      email_address: "admin@example.com",
-      password: "password123",
-      admin: true
-    )
-    regular_user = User.create!(
-      email_address: "user@example.com",
-      password: "password123",
-      admin: false
-    )
+  test "admin scope returns users in admin groups" do
+    admin_group = groups(:admin_group)
+    admin_user = User.create!(email_address: "admin@example.com", password: "password123")
+    admin_user.groups << admin_group
+    regular_user = User.create!(email_address: "user@example.com", password: "password123")
 
     admins = User.admins
     assert_includes admins, admin_user
     assert_not_includes admins, regular_user
   end
 
+  test "admin? reflects membership in any admin: true group" do
+    user = User.create!(email_address: "promoted@example.com", password: "password123")
+    assert_not user.admin?
+    user.groups << groups(:admin_group)
+    assert user.reload.admin?
+  end
+
+  test "after_create auto-joins all auto_assign groups" do
+    user = User.create!(email_address: "newbie@example.com", password: "password123")
+    assert_includes user.groups, groups(:everyone)
+  end
+
+  test "skip_auto_assign disables the after_create callback" do
+    user = User.new(email_address: "skipper@example.com", password: "password123")
+    user.skip_auto_assign = true
+    user.save!
+    assert_not_includes user.groups, groups(:everyone)
+  end
+
   test "validates email address format" do
     user = User.new(email_address: "invalid-email", password: "password123")
     assert_not user.valid?

test/services/oidc_jwt_service_test.rb

@@ -95,7 +95,8 @@ class OidcJwtServiceTest < ActiveSupport::TestCase
   end
 
   test "admin claim should not be included in token" do
-    @user.update!(admin: true)
+    # alice is already in admin_group via fixtures, so admin? is true here
+    assert @user.admin?
 
     token = @service.generate_id_token(@user, @application)
 

test/test_helpers/session_test_helper.rb

@@ -12,6 +12,15 @@ module SessionTestHelper
     Current.session&.destroy!
     cookies.delete("session_id")
   end
+
+  # Attach the auto-assign "everyone" group to the given app so existing tests
+  # written under the old "empty allowed_groups = public" rule keep working.
+  # New tests should attach groups explicitly to model real access intent.
+  def grant_everyone_access(app)
+    everyone = (groups(:everyone) rescue Group.find_by(auto_assign: true))
+    app.allowed_groups << everyone unless app.allowed_groups.include?(everyone)
+    app
+  end
 end
 
 ActiveSupport.on_load(:action_dispatch_integration_test) do