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.

Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1242
Last-Updated: 2017-01-16

Patch-Name: gssapi.patch

1 files changed, 14 insertions, 1 deletions

diff --git a/clientloop.c b/clientloop.c
index 064816234..38b0330e9 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -113,6 +113,10 @@
 #include "ssherr.h"
 #include "hostfile.h"
 
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+
 /* import options */
 extern Options options;
 
@@ -1664,9 +1668,18 @@ client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id)
                         break;
 
                 /* Do channel operations unless rekeying in progress. */
-                if (!ssh_packet_is_rekeying(active_state))
+                if (!ssh_packet_is_rekeying(active_state)) {
                         channel_after_select(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(readset);