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: 2018-08-24

Patch-Name: gssapi.patch

1 files changed, 15 insertions, 2 deletions

diff --git a/auth-krb5.c b/auth-krb5.c
index 3096f1c8e..204752e1b 100644
--- a/auth-krb5.c
+++ b/auth-krb5.c
@@ -182,8 +182,13 @@ auth_krb5_password(Authctxt *authctxt, const char *password)
 
         len = strlen(authctxt->krb5_ticket_file) + 6;
         authctxt->krb5_ccname = xmalloc(len);
+#ifdef USE_CCAPI
+        snprintf(authctxt->krb5_ccname, len, "API:%s",
+            authctxt->krb5_ticket_file);
+#else
         snprintf(authctxt->krb5_ccname, len, "FILE:%s",
             authctxt->krb5_ticket_file);
+#endif
 
 #ifdef USE_PAM
         if (options.use_pam)
@@ -240,15 +245,22 @@ krb5_cleanup_proc(Authctxt *authctxt)
 #ifndef HEIMDAL
 krb5_error_code
 ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
-        int tmpfd, ret, oerrno;
+        int ret, oerrno;
         char ccname[40];
         mode_t old_umask;
+#ifdef USE_CCAPI
+        char cctemplate[] = "API:krb5cc_%d";
+#else
+        char cctemplate[] = "FILE:/tmp/krb5cc_%d_XXXXXXXXXX";
+        int tmpfd;
+#endif
 
         ret = snprintf(ccname, sizeof(ccname),
-            "FILE:/tmp/krb5cc_%d_XXXXXXXXXX", geteuid());
+            cctemplate, geteuid());
         if (ret < 0 || (size_t)ret >= sizeof(ccname))
                 return ENOMEM;
 
+#ifndef USE_CCAPI
         old_umask = umask(0177);
         tmpfd = mkstemp(ccname + strlen("FILE:"));
         oerrno = errno;
@@ -265,6 +277,7 @@ ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
                 return oerrno;
         }
         close(tmpfd);
+#endif
 
         return (krb5_cc_resolve(ctx, ccname, ccache));
 }