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>

internal/query/projection/app.go

@@ -58,6 +58,7 @@ const (
 	AppOIDCConfigColumnClockSkew                = "clock_skew"
 	AppOIDCConfigColumnAdditionalOrigins        = "additional_origins"
 	AppOIDCConfigColumnSkipNativeAppSuccessPage = "skip_native_app_success_page"
+	AppOIDCConfigColumnBackChannelLogoutURI     = "back_channel_logout_uri"
 
 	appSAMLTableSuffix             = "saml_configs"
 	AppSAMLConfigColumnAppID       = "app_id"
@@ -125,6 +126,7 @@ func (*appProjection) Init() *old_handler.Check {
 			handler.NewColumn(AppOIDCConfigColumnClockSkew, handler.ColumnTypeInt64, handler.Default(0)),
 			handler.NewColumn(AppOIDCConfigColumnAdditionalOrigins, handler.ColumnTypeTextArray, handler.Nullable()),
 			handler.NewColumn(AppOIDCConfigColumnSkipNativeAppSuccessPage, handler.ColumnTypeBool, handler.Default(false)),
+			handler.NewColumn(AppOIDCConfigColumnBackChannelLogoutURI, handler.ColumnTypeText, handler.Nullable()),
 		},
 			handler.NewPrimaryKey(AppOIDCConfigColumnInstanceID, AppOIDCConfigColumnAppID),
 			appOIDCTableSuffix,
@@ -500,6 +502,7 @@ func (p *appProjection) reduceOIDCConfigAdded(event eventstore.Event) (*handler.
 				handler.NewCol(AppOIDCConfigColumnClockSkew, e.ClockSkew),
 				handler.NewCol(AppOIDCConfigColumnAdditionalOrigins, database.TextArray[string](e.AdditionalOrigins)),
 				handler.NewCol(AppOIDCConfigColumnSkipNativeAppSuccessPage, e.SkipNativeAppSuccessPage),
+				handler.NewCol(AppOIDCConfigColumnBackChannelLogoutURI, e.BackChannelLogoutURI),
 			},
 			handler.WithTableSuffix(appOIDCTableSuffix),
 		),
@@ -522,7 +525,7 @@ func (p *appProjection) reduceOIDCConfigChanged(event eventstore.Event) (*handle
 		return nil, zerrors.ThrowInvalidArgumentf(nil, "HANDL-GNHU1", "reduce.wrong.event.type %s", project.OIDCConfigChangedType)
 	}
 
-	cols := make([]handler.Column, 0, 15)
+	cols := make([]handler.Column, 0, 16)
 	if e.Version != nil {
 		cols = append(cols, handler.NewCol(AppOIDCConfigColumnVersion, *e.Version))
 	}
@@ -568,6 +571,9 @@ func (p *appProjection) reduceOIDCConfigChanged(event eventstore.Event) (*handle
 	if e.SkipNativeAppSuccessPage != nil {
 		cols = append(cols, handler.NewCol(AppOIDCConfigColumnSkipNativeAppSuccessPage, *e.SkipNativeAppSuccessPage))
 	}
+	if e.BackChannelLogoutURI != nil {
+		cols = append(cols, handler.NewCol(AppOIDCConfigColumnBackChannelLogoutURI, *e.BackChannelLogoutURI))
+	}
 
 	if len(cols) == 0 {
 		return handler.NewNoOpStatement(e), nil

internal/query/projection/app_test.go

@@ -558,7 +558,8 @@ func TestAppProjection_reduces(t *testing.T) {
                         "idTokenUserinfoAssertion": true,
                         "clockSkew": 1000,
                         "additionalOrigins": ["origin.one.ch", "origin.two.ch"],
-						"skipNativeAppSuccessPage": true
+						"skipNativeAppSuccessPage": true,
+						"backChannelLogoutURI": "back.channel.one.ch"
 		}`),
 					), project.OIDCConfigAddedEventMapper),
 			},
@@ -569,7 +570,7 @@ func TestAppProjection_reduces(t *testing.T) {
 				executer: &testExecuter{
 					executions: []execution{
 						{
-							expectedStmt: "INSERT INTO projections.apps7_oidc_configs (app_id, instance_id, version, client_id, client_secret, redirect_uris, response_types, grant_types, application_type, auth_method_type, post_logout_redirect_uris, is_dev_mode, access_token_type, access_token_role_assertion, id_token_role_assertion, id_token_userinfo_assertion, clock_skew, additional_origins, skip_native_app_success_page) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19)",
+							expectedStmt: "INSERT INTO projections.apps7_oidc_configs (app_id, instance_id, version, client_id, client_secret, redirect_uris, response_types, grant_types, application_type, auth_method_type, post_logout_redirect_uris, is_dev_mode, access_token_type, access_token_role_assertion, id_token_role_assertion, id_token_userinfo_assertion, clock_skew, additional_origins, skip_native_app_success_page, back_channel_logout_uri) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20)",
 							expectedArgs: []interface{}{
 								"app-id",
 								"instance-id",
@@ -590,6 +591,7 @@ func TestAppProjection_reduces(t *testing.T) {
 								1 * time.Microsecond,
 								database.TextArray[string]{"origin.one.ch", "origin.two.ch"},
 								true,
+								"back.channel.one.ch",
 							},
 						},
 						{
@@ -630,7 +632,8 @@ func TestAppProjection_reduces(t *testing.T) {
                         "idTokenUserinfoAssertion": true,
                         "clockSkew": 1000,
                         "additionalOrigins": ["origin.one.ch", "origin.two.ch"],
-						"skipNativeAppSuccessPage": true
+						"skipNativeAppSuccessPage": true,
+						"backChannelLogoutURI": "back.channel.one.ch"
 		}`),
 					), project.OIDCConfigAddedEventMapper),
 			},
@@ -641,7 +644,7 @@ func TestAppProjection_reduces(t *testing.T) {
 				executer: &testExecuter{
 					executions: []execution{
 						{
-							expectedStmt: "INSERT INTO projections.apps7_oidc_configs (app_id, instance_id, version, client_id, client_secret, redirect_uris, response_types, grant_types, application_type, auth_method_type, post_logout_redirect_uris, is_dev_mode, access_token_type, access_token_role_assertion, id_token_role_assertion, id_token_userinfo_assertion, clock_skew, additional_origins, skip_native_app_success_page) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19)",
+							expectedStmt: "INSERT INTO projections.apps7_oidc_configs (app_id, instance_id, version, client_id, client_secret, redirect_uris, response_types, grant_types, application_type, auth_method_type, post_logout_redirect_uris, is_dev_mode, access_token_type, access_token_role_assertion, id_token_role_assertion, id_token_userinfo_assertion, clock_skew, additional_origins, skip_native_app_success_page, back_channel_logout_uri) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20)",
 							expectedArgs: []interface{}{
 								"app-id",
 								"instance-id",
@@ -662,6 +665,7 @@ func TestAppProjection_reduces(t *testing.T) {
 								1 * time.Microsecond,
 								database.TextArray[string]{"origin.one.ch", "origin.two.ch"},
 								true,
+								"back.channel.one.ch",
 							},
 						},
 						{
@@ -700,8 +704,8 @@ func TestAppProjection_reduces(t *testing.T) {
                         "idTokenUserinfoAssertion": true,
                         "clockSkew": 1000,
                         "additionalOrigins": ["origin.one.ch", "origin.two.ch"],
-						"skipNativeAppSuccessPage": true
-
+						"skipNativeAppSuccessPage": true,
+						"backChannelLogoutURI": "back.channel.one.ch"
 		}`),
 					), project.OIDCConfigChangedEventMapper),
 			},
@@ -712,7 +716,7 @@ func TestAppProjection_reduces(t *testing.T) {
 				executer: &testExecuter{
 					executions: []execution{
 						{
-							expectedStmt: "UPDATE projections.apps7_oidc_configs SET (version, redirect_uris, response_types, grant_types, application_type, auth_method_type, post_logout_redirect_uris, is_dev_mode, access_token_type, access_token_role_assertion, id_token_role_assertion, id_token_userinfo_assertion, clock_skew, additional_origins, skip_native_app_success_page) = ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15) WHERE (app_id = $16) AND (instance_id = $17)",
+							expectedStmt: "UPDATE projections.apps7_oidc_configs SET (version, redirect_uris, response_types, grant_types, application_type, auth_method_type, post_logout_redirect_uris, is_dev_mode, access_token_type, access_token_role_assertion, id_token_role_assertion, id_token_userinfo_assertion, clock_skew, additional_origins, skip_native_app_success_page, back_channel_logout_uri) = ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16) WHERE (app_id = $17) AND (instance_id = $18)",
 							expectedArgs: []interface{}{
 								domain.OIDCVersionV1,
 								database.TextArray[string]{"redirect.one.ch", "redirect.two.ch"},
@@ -729,6 +733,7 @@ func TestAppProjection_reduces(t *testing.T) {
 								1 * time.Microsecond,
 								database.TextArray[string]{"origin.one.ch", "origin.two.ch"},
 								true,
+								"back.channel.one.ch",
 								"app-id",
 								"instance-id",
 							},

internal/query/projection/instance_features.go

@@ -104,6 +104,10 @@ func (*instanceFeatureProjection) Reducers() []handler.AggregateReducer {
 				Event:  feature_v2.InstanceDisableUserTokenEvent,
 				Reduce: reduceInstanceSetFeature[bool],
 			},
+			{
+				Event:  feature_v2.InstanceEnableBackChannelLogout,
+				Reduce: reduceInstanceSetFeature[bool],
+			},
 			{
 				Event:  instance.InstanceRemovedEventType,
 				Reduce: reduceInstanceRemovedHelper(InstanceDomainInstanceIDCol),

internal/query/projection/system_features.go

@@ -84,6 +84,10 @@ func (*systemFeatureProjection) Reducers() []handler.AggregateReducer {
 				Event:  feature_v2.SystemDisableUserTokenEvent,
 				Reduce: reduceSystemSetFeature[bool],
 			},
+			{
+				Event:  feature_v2.SystemEnableBackChannelLogout,
+				Reduce: reduceSystemSetFeature[bool],
+			},
 		},
 	}}
 }