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From a97f75bc484762111ae4e994791f4a5af6294c26 Mon Sep 17 00:00:00 2001
From: Damien Miller <djm@mindrot.org>
Date: Tue, 11 Aug 2015 13:34:12 +1000
Subject: set sshpam_ctxt to NULL after free
Avoids use-after-free in monitor when privsep child is compromised.
Reported by Moritz Jodeit; ok dtucker@
Origin: upstream, https://anongit.mindrot.org/openssh.git/commit/?id=5e75f5198769056089fb06c4d738ab0e5abc66f7
Forwarded: not-needed
Last-Update: 2015-08-19
Patch-Name: backport-pam-use-after-free.patch
---
monitor.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/monitor.c b/monitor.c
index 870a6b9..e8541b4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1225,14 +1225,16 @@ mm_answer_pam_respond(int sock, Buffer *m)
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
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