Ticket History #9008: Fix KDC null deref on TGS inner body null server

Fix KDC null deref on TGS inner body null server

After the KDC decodes a FAST inner body, it does not check for a null
server. Prior to commit 39548a5b17bbda9eeb63625a201cfd19b9de1c5b this
would typically result in an error from krb5_unparse_name(), but with
the addition of get_local_tgt() it results in a null dereference. Add
a null check.

Reported by Joseph Sutton of Catalyst.

CVE-2021-37750:

In MIT krb5 releases 1.14 and later, an authenticated attacker can
cause a null dereference in the KDC by sending a FAST TGS request with
no server field.

(cherry picked from commit d775c95af7606a51bf79547a94fa52ddd1cb7f49)

https://github.com/krb5/krb5/commit/fd9decf85055acca218c34c9e1222dc692b973d4
Author: Greg Hudson <ghudson@mit.edu>
Commit: fd9decf85055acca218c34c9e1222dc692b973d4
Branch: krb5-1.18
src/kdc/do_tgs_req.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)

Fix KDC null deref on TGS inner body null server

After the KDC decodes a FAST inner body, it does not check for a null
server. Prior to commit 39548a5b17bbda9eeb63625a201cfd19b9de1c5b this
would typically result in an error from krb5_unparse_name(), but with
the addition of get_local_tgt() it results in a null dereference. Add
a null check.

Reported by Joseph Sutton of Catalyst.

CVE-2021-37750:

In MIT krb5 releases 1.14 and later, an authenticated attacker can
cause a null dereference in the KDC by sending a FAST TGS request with
no server field.

(cherry picked from commit d775c95af7606a51bf79547a94fa52ddd1cb7f49)

https://github.com/krb5/krb5/commit/f5162aa63fb7652eae2ad74be4c3bdf869c0d1f7
Author: Greg Hudson <ghudson@mit.edu>
Commit: f5162aa63fb7652eae2ad74be4c3bdf869c0d1f7
Branch: krb5-1.19
src/kdc/do_tgs_req.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)