GSSAPI key exchange support

This patch has been rejected upstream: "None of the OpenSSH developers are
in favour of adding this, and this situation has not changed for several
years.  This is not a slight on Simon's patch, which is of fine quality, but
just that a) we don't trust GSSAPI implementations that much and b) we don't
like adding new KEX since they are pre-auth attack surface.  This one is
particularly scary, since it requires hooks out to typically root-owned
system resources."

However, quite a lot of people rely on this in Debian, and it's better to
have it merged into the main openssh package rather than having separate
-krb5 packages (as we used to have).  It seems to have a generally good
security history.

Author: Simon Wilkinson <simon@sxw.org.uk>
Author: Colin Watson <cjwatson@debian.org>
Author: Jakub Jelen <jjelen@redhat.com>
Origin: other, https://github.com/openssh-gsskex/openssh-gsskex/commits/debian/master
Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1242
Last-Updated: 2020-06-07

Patch-Name: gssapi.patch

1 files changed, 14 insertions, 1 deletions

diff --git a/clientloop.c b/clientloop.c
index da396c72a..42ace7789 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -112,6 +112,10 @@
 #include "ssherr.h"
 #include "hostfile.h"
 
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+
 /* import options */
 extern Options options;
 
@@ -1361,9 +1365,18 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
                         break;
 
                 /* Do channel operations unless rekeying in progress. */
-                if (!ssh_packet_is_rekeying(ssh))
+                if (!ssh_packet_is_rekeying(ssh)) {
                         channel_after_select(ssh, readset, writeset);
 
+#ifdef GSSAPI
+                        if (options.gss_renewal_rekey &&
+                            ssh_gssapi_credentials_updated(NULL)) {
+                                debug("credentials updated - forcing rekey");
+                                need_rekeying = 1;
+                        }
+#endif
+                }
+
                 /* Buffer input from the connection.  */
                 client_process_net_input(ssh, readset);