set sshpam_ctxt to NULL after free
Avoids use-after-free in monitor when privsep child is compromised.
Reported by Moritz Jodeit; ok dtucker@
diff --git a/monitor.c b/monitor.c
index f1b873d..a914209 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1166,14 +1166,16 @@
int
mm_answer_pam_free_ctx(int sock, Buffer *m)
{
+ int r = sshpam_authok != NULL && sshpam_authok == sshpam_ctxt;
debug3("%s", __func__);
(sshpam_device.free_ctx)(sshpam_ctxt);
+ sshpam_ctxt = sshpam_authok = NULL;
buffer_clear(m);
mm_request_send(sock, MONITOR_ANS_PAM_FREE_CTX, m);
auth_method = "keyboard-interactive";
auth_submethod = "pam";
- return (sshpam_authok == sshpam_ctxt);
+ return r;
}
#endif