winbind: Fix 100% loop

Thanks to "L.P.H. van Belle" <belle@bazuin.nl>
for help in reproducing the issue.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11038

From the bug report:

"With e551cdb37d3e re-applied the problem is gone with
and without kerberos. Moreover, if correctly configured,
sshd requests you to change your password at logon time,
which then succeeds.

The problem why I had this reverted was because I had not
gone through the pain to correctly configure all the PAM
services (in particular the "account" section), leading
to sshd letting the user in when the password had to be
changed."

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit e551cdb37d3e8cfb155bc33f9b162761c8d60889)

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Fri Oct  2 00:16:29 CEST 2015 on sn-devel-104

(cherry picked from commit e524ab9f7ee9f4aff50dd5bc42312f9000bf1c6e)

diff --git a/source3/libads/kerberos.c b/source3/libads/kerberos.c
index d5e023873f8bd80bf7fa678a3b2341cd886de13e..b865d7a8bbe3d740b1f0513e7b802e9bc96eca72 100644 (file)
--- a/source3/libads/kerberos.c
+++ b/source3/libads/kerberos.c
@@ -50,6 +50,22 @@ kerb_prompter(krb5_context ctx, void *data,
 {
        if (num_prompts == 0) return 0;
 
+       if ((num_prompts == 2) &&
+           (prompts[0].type == KRB5_PROMPT_TYPE_NEW_PASSWORD) &&
+           (prompts[1].type == KRB5_PROMPT_TYPE_NEW_PASSWORD_AGAIN)) {
+               /*
+                * We don't want to change passwords here. We're
+                * called from heimal when the KDC returns
+                * KRB5KDC_ERR_KEY_EXPIRED, but at this point we don't
+                * have the chance to ask the user for a new
+                * password. If we return 0 (i.e. success), we will be
+                * spinning in the endless for-loop in
+                * change_password() in
+                * source4/heimdal/lib/krb5/init_creds_pw.c:526ff
+                */
+               return KRB5KDC_ERR_KEY_EXPIRED;
+       }
+
        memset(prompts[0].reply->data, '\0', prompts[0].reply->length);
        if (prompts[0].reply->length > 0) {
                if (data) {