CVE-2021-3671 HEIMDAL kdc: validate sname in TGS-REQ
In tgs_build_reply(), validate the server name in the TGS-REQ is present before
dereferencing.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14770
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14817
[abartlet@samba.org backported from from Heimdal
commit
04171147948d0a3636bc6374181926f0fb2ec83a via reference
to an earlier patch by Joseph Sutton]
RN: An unuthenticated user can crash the AD DC KDC by omitting the server name in a TGS-REQ
Reviewed-by: Andreas Schneider <asn@samba.org>
(cherry picked from commit
0cb4b939f192376bf5e33637863a91a20f74c5a5)