feat(OIDC): add back channel logout (#8837)

# Which Problems Are Solved

Currently ZITADEL supports RP-initiated logout for clients. Back-channel
logout ensures that user sessions are terminated across all connected
applications, even if the user closes their browser or loses
connectivity providing a more secure alternative for certain use cases.

# How the Problems Are Solved

If the feature is activated and the client used for the authentication
has a back_channel_logout_uri configured, a
`session_logout.back_channel` will be registered. Once a user terminates
their session, a (notification) handler will send a SET (form POST) to
the registered uri containing a logout_token (with the user's ID and
session ID).

- A new feature "back_channel_logout" is added on system and instance
level
- A `back_channel_logout_uri` can be managed on OIDC applications
- Added a `session_logout` aggregate to register and inform about sent
`back_channel` notifications
- Added a `SecurityEventToken` channel and `Form`message type in the
notification handlers
- Added `TriggeredAtOrigin` fields to `HumanSignedOut` and
`TerminateSession` events for notification handling
- Exported various functions and types in the `oidc` package to be able
to reuse for token signing in the back_channel notifier.
- To prevent that current existing session termination events will be
handled, a setup step is added to set the `current_states` for the
`projections.notifications_back_channel_logout` to the current position

- [x] requires https://github.com/zitadel/oidc/pull/671

# Additional Changes

- Updated all OTEL dependencies to v1.29.0, since OIDC already updated
some of them to that version.
- Single Session Termination feature is correctly checked (fixed feature
mapping)

# Additional Context

- closes https://github.com/zitadel/zitadel/issues/8467
- TODO:
  - Documentation
  - UI to be done: https://github.com/zitadel/zitadel/issues/8469

---------

Co-authored-by: Hidde Wieringa <hidde@hiddewieringa.nl>

cmd/defaults.yaml

@@ -411,6 +411,7 @@ OIDC:
   DefaultLoginURLV2: "/login?authRequest=" # ZITADEL_OIDC_DEFAULTLOGINURLV2
   DefaultLogoutURLV2: "/logout?post_logout_redirect=" # ZITADEL_OIDC_DEFAULTLOGOUTURLV2
   PublicKeyCacheMaxAge: 24h # ZITADEL_OIDC_PUBLICKEYCACHEMAXAGE
+  DefaultBackChannelLogoutLifetime: 15m # ZITADEL_OIDC_DEFAULTBACKCHANNELLOGOUTLIFETIME
 
 SAML:
   ProviderConfig:

cmd/mirror/projections.go

@@ -200,6 +200,7 @@ func projections(
 		ctx,
 		config.Projections.Customizations["notifications"],
 		config.Projections.Customizations["notificationsquotas"],
+		config.Projections.Customizations["backchannel"],
 		config.Projections.Customizations["telemetry"],
 		*config.Telemetry,
 		config.ExternalDomain,
@@ -213,6 +214,8 @@ func projections(
 		keys.User,
 		keys.SMTP,
 		keys.SMS,
+		keys.OIDC,
+		config.OIDC.DefaultBackChannelLogoutLifetime,
 	)
 
 	config.Auth.Spooler.Client = client

cmd/setup/37.go

@@ -0,0 +1,27 @@
+package setup
+
+import (
+	"context"
+	_ "embed"
+
+	"github.com/zitadel/zitadel/internal/database"
+	"github.com/zitadel/zitadel/internal/eventstore"
+)
+
+var (
+	//go:embed 37.sql
+	addBackChannelLogoutURI string
+)
+
+type Apps7OIDConfigsBackChannelLogoutURI struct {
+	dbClient *database.DB
+}
+
+func (mig *Apps7OIDConfigsBackChannelLogoutURI) Execute(ctx context.Context, _ eventstore.Event) error {
+	_, err := mig.dbClient.ExecContext(ctx, addBackChannelLogoutURI)
+	return err
+}
+
+func (mig *Apps7OIDConfigsBackChannelLogoutURI) String() string {
+	return "37_apps7_oidc_configs_add_back_channel_logout_uri"
+}

cmd/setup/37.sql

@@ -0,0 +1 @@
+ALTER TABLE IF EXISTS projections.apps7_oidc_configs ADD COLUMN IF NOT EXISTS back_channel_logout_uri TEXT;

cmd/setup/38.go

@@ -0,0 +1,28 @@
+package setup
+
+import (
+	"context"
+	_ "embed"
+
+	"github.com/zitadel/zitadel/internal/database"
+	"github.com/zitadel/zitadel/internal/eventstore"
+)
+
+var (
+	//go:embed 38.sql
+	backChannelLogoutCurrentState string
+)
+
+type BackChannelLogoutNotificationStart struct {
+	dbClient *database.DB
+	esClient *eventstore.Eventstore
+}
+
+func (mig *BackChannelLogoutNotificationStart) Execute(ctx context.Context, e eventstore.Event) error {
+	_, err := mig.dbClient.ExecContext(ctx, backChannelLogoutCurrentState, e.Sequence(), e.CreatedAt(), e.Position())
+	return err
+}
+
+func (mig *BackChannelLogoutNotificationStart) String() string {
+	return "38_back_channel_logout_notification_start_"
+}

cmd/setup/38.sql

@@ -0,0 +1,20 @@
+INSERT INTO projections.current_states (
+    instance_id
+   , projection_name
+   , last_updated
+   , sequence
+   , event_date
+   , position
+   , filter_offset
+)
+    SELECT instance_id
+         , 'projections.notifications_back_channel_logout'
+         , now()
+         , $1
+         , $2
+         , $3
+         , 0
+    FROM eventstore.events2
+        WHERE aggregate_type = 'instance'
+            AND event_type = 'instance.added'
+    ON CONFLICT DO NOTHING;

cmd/setup/config.go

@@ -123,6 +123,8 @@ type Steps struct {
 	s34AddCacheSchema                       *AddCacheSchema
 	s35AddPositionToIndexEsWm               *AddPositionToIndexEsWm
 	s36FillV2Milestones                     *FillV2Milestones
+	s37Apps7OIDConfigsBackChannelLogoutURI  *Apps7OIDConfigsBackChannelLogoutURI
+	s38BackChannelLogoutNotificationStart   *BackChannelLogoutNotificationStart
 }
 
 func MustNewSteps(v *viper.Viper) *Steps {

cmd/setup/setup.go

@@ -166,6 +166,8 @@ func Setup(ctx context.Context, config *Config, steps *Steps, masterKey string)
 	steps.s34AddCacheSchema = &AddCacheSchema{dbClient: queryDBClient}
 	steps.s35AddPositionToIndexEsWm = &AddPositionToIndexEsWm{dbClient: esPusherDBClient}
 	steps.s36FillV2Milestones = &FillV2Milestones{dbClient: queryDBClient, eventstore: eventstoreClient}
+	steps.s37Apps7OIDConfigsBackChannelLogoutURI = &Apps7OIDConfigsBackChannelLogoutURI{dbClient: esPusherDBClient}
+	steps.s38BackChannelLogoutNotificationStart = &BackChannelLogoutNotificationStart{dbClient: esPusherDBClient, esClient: eventstoreClient}
 
 	err = projection.Create(ctx, projectionDBClient, eventstoreClient, config.Projections, nil, nil, nil)
 	logging.OnError(err).Fatal("unable to start projections")
@@ -211,6 +213,7 @@ func Setup(ctx context.Context, config *Config, steps *Steps, masterKey string)
 		steps.s34AddCacheSchema,
 		steps.s35AddPositionToIndexEsWm,
 		steps.s36FillV2Milestones,
+		steps.s38BackChannelLogoutNotificationStart,
 	} {
 		mustExecuteMigration(ctx, eventstoreClient, step, "migration failed")
 	}
@@ -227,6 +230,7 @@ func Setup(ctx context.Context, config *Config, steps *Steps, masterKey string)
 		steps.s27IDPTemplate6SAMLNameIDFormat,
 		steps.s32AddAuthSessionID,
 		steps.s33SMSConfigs3TwilioAddVerifyServiceSid,
+		steps.s37Apps7OIDConfigsBackChannelLogoutURI,
 	} {
 		mustExecuteMigration(ctx, eventstoreClient, step, "migration failed")
 	}
@@ -424,6 +428,7 @@ func initProjections(
 		ctx,
 		config.Projections.Customizations["notifications"],
 		config.Projections.Customizations["notificationsquotas"],
+		config.Projections.Customizations["backchannel"],
 		config.Projections.Customizations["telemetry"],
 		*config.Telemetry,
 		config.ExternalDomain,
@@ -437,6 +442,8 @@ func initProjections(
 		keys.User,
 		keys.SMTP,
 		keys.SMS,
+		keys.OIDC,
+		config.OIDC.DefaultBackChannelLogoutLifetime,
 	)
 	for _, p := range notify_handler.Projections() {
 		err := migration.Migrate(ctx, eventstoreClient, p)

cmd/start/start.go

@@ -270,6 +270,7 @@ func startZitadel(ctx context.Context, config *Config, masterKey string, server
 		ctx,
 		config.Projections.Customizations["notifications"],
 		config.Projections.Customizations["notificationsquotas"],
+		config.Projections.Customizations["backchannel"],
 		config.Projections.Customizations["telemetry"],
 		*config.Telemetry,
 		config.ExternalDomain,
@@ -283,6 +284,8 @@ func startZitadel(ctx context.Context, config *Config, masterKey string, server
 		keys.User,
 		keys.SMTP,
 		keys.SMS,
+		keys.OIDC,
+		config.OIDC.DefaultBackChannelLogoutLifetime,
 	)
 	notification.Start(ctx)