From 3c9bdbd63e0f335e2aa17f640c3afdfa8d541a9a Mon Sep 17 00:00:00 2001
From: Jacek Kowalski <Jacek@jacekk.info>
Date: Tue, 03 Nov 2026 20:58:49 +0000
Subject: [PATCH] Verify target service when issuing proxy tickets

---
 src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java |   21 +++++++++++++++++----
 1 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java b/src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java
index 30da645..afc9c2c 100644
--- a/src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java
+++ b/src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java
@@ -40,6 +40,7 @@
     protected RealmModel realm;
     protected EventBuilder event;
     protected ClientModel client;
+    protected String service;
     protected AuthenticatedClientSessionModel clientSession;
     protected String pgtIou;
 
@@ -69,10 +70,7 @@
 
         event.detail(Details.REDIRECT_URI, service);
 
-        client = realm.getClientsStream()
-                .filter(c -> CASLoginProtocol.LOGIN_PROTOCOL.equals(c.getProtocol()))
-                .filter(c -> RedirectUtils.verifyRedirectUri(session, service, c) != null)
-                .findFirst().orElse(null);
+        client = findClient(service);
         if (client == null) {
             event.error(Errors.CLIENT_NOT_FOUND);
             throw new CASValidationException(CASErrorCode.INVALID_SERVICE, "Client not found", Response.Status.BAD_REQUEST);
@@ -83,11 +81,20 @@
             throw new CASValidationException(CASErrorCode.INVALID_SERVICE, "Client disabled", Response.Status.BAD_REQUEST);
         }
 
+        this.service = RedirectUtils.verifyRedirectUri(session, service, client);
+
         event.client(client.getClientId());
 
         session.getContext().setClient(client);
     }
 
+    protected ClientModel findClient(String service) {
+        return realm.getClientsStream()
+                .filter(c -> CASLoginProtocol.LOGIN_PROTOCOL.equals(c.getProtocol()))
+                .filter(c -> RedirectUtils.verifyRedirectUri(session, service, c) != null)
+                .findFirst().orElse(null);
+    }
+
     protected void checkTicket(String ticket, String prefix, boolean requireReauth) {
         if (ticket == null) {
             event.error(Errors.INVALID_CODE);
@@ -162,6 +169,12 @@
             throw new CASValidationException(CASErrorCode.INVALID_TICKET, "Code is expired", Response.Status.BAD_REQUEST);
         }
 
+        // Service and proxy tickets are valid only for the service they were issued for
+        if (!isReusable && (service == null || !service.equals(codeData.getRedirectUriParam()))) {
+            event.error(Errors.INVALID_REDIRECT_URI);
+            throw new CASValidationException(CASErrorCode.INVALID_SERVICE, "Ticket was not issued for this service", Response.Status.BAD_REQUEST);
+        }
+
         clientSession.setNote(CASLoginProtocol.SESSION_TICKET, ticket);
 
         if (requireReauth && AuthenticationManager.isSSOAuthentication(clientSession)) {

--
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