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From 7406e666efe2d19e93cf6f50735b3a927bc3dfce Mon Sep 17 00:00:00 2001
From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Mon, 20 Mar 2023 20:22:14 +0100
Subject: Only set PAM_RHOST if the remote host is not "UNKNOWN"
When using sshd's -i option with stdio that is not a AF_INET/AF_INET6
socket, auth_get_canonical_hostname() returns "UNKNOWN" which is then
set as the value of PAM_RHOST, causing pam to try to do a reverse DNS
query of "UNKNOWN", which times out multiple times, causing a
substantial slowdown when logging in.
To fix this, let's only set PAM_RHOST if the hostname is not "UNKNOWN".
Author: Daan De Meyer <daan.j.demeyer@gmail.com>
Last-Update: 2024-04-03
Patch-Name: pam-avoid-unknown-host.patch
---
auth-pam.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/auth-pam.c b/auth-pam.c
index 13c0a792e..b22883b95 100644
--- a/auth-pam.c
+++ b/auth-pam.c
@@ -735,7 +735,7 @@ sshpam_init(struct ssh *ssh, Authctxt *authctxt)
sshpam_laddr = get_local_ipaddr(
ssh_packet_get_connection_in(ssh));
}
- if (sshpam_rhost != NULL) {
+ if (sshpam_rhost != NULL && strcmp(sshpam_rhost, "UNKNOWN") != 0) {
debug("PAM: setting PAM_RHOST to \"%s\"", sshpam_rhost);
sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST,
sshpam_rhost);
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