Check for FAST in encrypted challenge client

If we reach the encrypted challenge clpreauth process method without
an armor key, error out instead of crashing.  This can happen if (a)
the KDC offers encrypted challenge even though the request doesn't use
FAST (the Heimdal KDC apparently does this), and (b) we fall back to
that preauth method before generating a preauthenticated request,
typically because of a prompter failure in encrypted timestamp.
Reported by Nico Williams.

(cherry picked from commit ff6aac3e018e80fa32df2e14446c6ed9595dfc3c)

ticket: 8573
version_fixed: 1.15.2

diff --git a/src/lib/krb5/krb/preauth_ec.c b/src/lib/krb5/krb/preauth_ec.c
index b1978336a063829a1fcf2e23adfa48d2d590e0de..c1aa9090fb6c5e8b05235bcdd41af1e136242e95 100644 (file)
--- a/src/lib/krb5/krb/preauth_ec.c
+++ b/src/lib/krb5/krb/preauth_ec.c
@@ -58,6 +58,8 @@ ec_process(krb5_context context, krb5_clpreauth_moddata moddata,
     krb5_keyblock *challenge_key = NULL, *armor_key, *as_key;
 
     armor_key = cb->fast_armor(context, rock);
+    if (armor_key == NULL)
+        return ENOENT;
     retval = cb->get_as_key(context, rock, &as_key);
     if (retval == 0 && padata->length) {
         krb5_enc_data *enc = NULL;