Use correct name-type in TGS-REQs for 2008R2 RODCs

Correctly set the name-type for the TGS principals to KRB5_NT_SRV_INST
in TGS-REQs.  (Previously, only AS-REQs had the name-type set in this
way.)  Windows Server 2008 R2 read-only domain controllers (RODCs)
insist on having the correct name-type for the TGS principal in
TGS-REQs as well as AS-REQs, at least for the TGT-forwarding case.

Thanks to Sebastian Galiano for reporting this bug and helping with
testing.

(cherry picked from commit 5994d8928b8ff88751b14bc60c7d7bfce8b30e57)

ticket: 7142 (new)
version_fixed: 1.9.4
status: resolved

2 files changed, 19 insertions, 12 deletions

diff --git a/src/lib/krb5/krb/fwd_tgt.c b/src/lib/krb5/krb/fwd_tgt.c
index 5725e49..198ef8e 100644
--- a/src/lib/krb5/krb/fwd_tgt.c
+++ b/src/lib/krb5/krb/fwd_tgt.c
@@ -29,6 +29,7 @@
 #ifdef HAVE_MEMORY_H
 #include <memory.h>
 #endif
+#include "int-proto.h"
 
 /* helper function: convert flags to necessary KDC options */
 #define flags2options(flags) (flags & KDC_TKT_COMMON_MASK)
@@ -99,14 +100,9 @@ krb5_fwd_tgt_creds(krb5_context context, krb5_auth_context auth_context, char *r
     if ((retval = krb5_copy_principal(context, client, &creds.client)))
         goto errout;
 
-    if ((retval = krb5_build_principal_ext(context, &creds.server,
-                                           client->realm.length,
-                                           client->realm.data,
-                                           KRB5_TGS_NAME_SIZE,
-                                           KRB5_TGS_NAME,
-                                           client->realm.length,
-                                           client->realm.data,
-                                           0)))
+    retval = krb5int_tgtname(context, &client->realm, &client->realm,
+                             &creds.server);
+    if (retval)
         goto errout;
 
     /* fetch tgt directly from cache */
diff --git a/src/lib/krb5/krb/tgtname.c b/src/lib/krb5/krb/tgtname.c
index 416badd..534b39e 100644
--- a/src/lib/krb5/krb/tgtname.c
+++ b/src/lib/krb5/krb/tgtname.c
@@ -34,8 +34,19 @@
 krb5_error_code
 krb5int_tgtname(krb5_context context, const krb5_data *server, const krb5_data *client, krb5_principal *tgtprinc)
 {
-    return krb5_build_principal_ext(context, tgtprinc, client->length, client->data,
-                                    KRB5_TGS_NAME_SIZE, KRB5_TGS_NAME,
-                                    server->length, server->data,
-                                    0);
+    krb5_error_code ret;
+
+    ret = krb5_build_principal_ext(context, tgtprinc, client->length, client->data,
+                                   KRB5_TGS_NAME_SIZE, KRB5_TGS_NAME,
+                                   server->length, server->data,
+                                   0);
+    if (ret)
+        return ret;
+    /*
+     * Windows Server 2008 R2 RODC insists on TGS principal names having the
+     * right name type.
+     */
+    krb5_princ_type(context, *tgtprinc) = KRB5_NT_SRV_INST;
+
+    return ret;
 }