krb5 commit [krb5-1.18]: Check cross-realm TGT name for RBCD requests

https://github.com/krb5/krb5/commit/d9875e7b0ee4e520fc6b4d4c92f10ecd360e3dd6
commit d9875e7b0ee4e520fc6b4d4c92f10ecd360e3dd6
Author: Isaac Boukris <[email protected]>
Date:   Sun Jan 12 17:32:09 2020 +0100

    Check cross-realm TGT name for RBCD requests
    
    (cherry picked from commit deb64d5eca602c7147b4253e51976c45f58b465f)
    
    ticket: 8865
    version_fixed: 1.18

 src/kdc/kdc_util.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/kdc/kdc_util.c b/src/kdc/kdc_util.c
index d0fd5d7..221bde1 100644
--- a/src/kdc/kdc_util.c
+++ b/src/kdc/kdc_util.c
@@ -1699,11 +1699,13 @@ check_rbcd_policy(kdc_realm_t *kdc_active_realm, unsigned int flags,
     if (isflagset(flags, KRB5_KDB_FLAG_CROSS_REALM)) {
         /*
          * Check that the proxy server is local, that the second ticket is a
-         * cross realm TGT, and that the second ticket client matches the
-         * header ticket client.
+         * cross-realm TGT for us, and that the second ticket client matches
+         * the header ticket client.
          */
         if (isflagset(flags, KRB5_KDB_FLAG_ISSUING_REFERRAL) ||
             !is_cross_tgs_principal(stkt_server->princ) ||
+            !krb5_principal_compare_any_realm(kdc_context, stkt_server->princ,
+                                              tgs_server) ||
             !krb5_principal_compare(kdc_context, stkt_client_princ,
                                     header_client_princ)) {
             return KRB5KDC_ERR_BADOPTION;