From fc40907a5866310f620d22c7f76ba5c148fafc07 Mon Sep 17 00:00:00 2001
From: Jacek Kowalski <Jacek@jacekk.info>
Date: Tue, 03 Nov 2026 21:04:42 +0000
Subject: [PATCH] Return CAS error instead of HTTP 500 on malformed tickets

---
 src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java |   32 +++++++++++++++++++++++++-------
 1 files changed, 25 insertions(+), 7 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 f510ebe..c517572 100644
--- a/src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java
+++ b/src/main/java/org/keycloak/protocol/cas/endpoints/AbstractValidateEndpoint.java
@@ -18,6 +18,7 @@
 import org.keycloak.services.managers.UserSessionCrossDCManager;
 import org.keycloak.services.util.DefaultClientSessionContext;
 
+import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.util.HashMap;
 import java.util.HexFormat;
@@ -185,8 +186,6 @@
             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)) {
             event.error(Errors.SESSION_EXPIRED);
             throw new CASValidationException(CASErrorCode.INVALID_TICKET, "Interactive authentication was requested but not performed", Response.Status.BAD_REQUEST);
@@ -225,19 +224,33 @@
             throw new CASValidationException(CASErrorCode.INVALID_TICKET, "Session not active", Response.Status.BAD_REQUEST);
         }
 
+        // Single logout refers to the service ticket the client session was established with
+        if (prefix.equals(CASLoginProtocol.SERVICE_TICKET_PREFIX)) {
+            clientSession.setNote(CASLoginProtocol.SESSION_TICKET, ticket);
+        }
     }
 
     protected void createProxyGrant(String pgtUrl) {
-        if ( RedirectUtils.verifyRedirectUri(session, pgtUrl, client) == null ) {
+        String verifiedPgtUrl = RedirectUtils.verifyRedirectUri(session, pgtUrl, client);
+        if (verifiedPgtUrl == null) {
             event.error(Errors.INVALID_REQUEST);
             throw new CASValidationException(CASErrorCode.INVALID_PROXY_CALLBACK, "Proxy callback is invalid", Response.Status.BAD_REQUEST);
         }
 
+        // The callback receives a PGT, so require HTTPS unless the realm's "Require SSL" setting allows plain HTTP for the host
+        URI pgtUri = URI.create(verifiedPgtUrl);
+        boolean isHttps = "https".equalsIgnoreCase(pgtUri.getScheme());
+        boolean isHttp = "http".equalsIgnoreCase(pgtUri.getScheme());
+        if (pgtUri.getHost() == null || !(isHttps || (isHttp && !realm.getSslRequired().isRequired(pgtUri.getHost())))) {
+            event.error(Errors.INVALID_REQUEST);
+            throw new CASValidationException(CASErrorCode.INVALID_PROXY_CALLBACK, "Proxy callback must use HTTPS", Response.Status.BAD_REQUEST);
+        }
+
         String pgtIou = getPGTIOU();
-        String pgtId  = getPGT(session, clientSession, pgtUrl);
+        String pgtId  = getPGT(session, clientSession, verifiedPgtUrl);
 
         try {
-            HttpGet request = new HttpGet(new URIBuilder(pgtUrl).setParameter("pgtIou",pgtIou).setParameter("pgtId",pgtId).build());
+            HttpGet request = new HttpGet(new URIBuilder(verifiedPgtUrl).setParameter("pgtIou",pgtIou).setParameter("pgtId",pgtId).build());
             request.setConfig(PGT_CALLBACK_REQUEST_CONFIG);
 
             HttpClient httpClient = session.getProvider(HttpClientProvider.class).getHttpClient();
@@ -317,7 +330,12 @@
     }
 
     private String hexDecode(String hex) {
-        byte[] bytes = HexFormat.of().parseHex(hex);
-        return new String(bytes, StandardCharsets.US_ASCII);
+        try {
+            byte[] bytes = HexFormat.of().parseHex(hex);
+            return new String(bytes, StandardCharsets.US_ASCII);
+        } catch (IllegalArgumentException e) {
+            event.error(Errors.INVALID_CODE);
+            throw new CASValidationException(CASErrorCode.INVALID_TICKET_SPEC, "Invalid format of the code", Response.Status.BAD_REQUEST);
+        }
     }
 }

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