https://bugs.gentoo.org/505604

From 9dcead87e6d7f66d34e7a56d11a30daca367dffb Mon Sep 17 00:00:00 2001
From: "Dmitry V. Levin" <ldv@altlinux.org>
Date: Wed, 26 Mar 2014 22:17:23 +0000
Subject: [PATCH] pam_timestamp: fix potential directory traversal issue
 (ticket #27)

pam_timestamp uses values of PAM_RUSER and PAM_TTY as components of
the timestamp pathname it creates, so extra care should be taken to
avoid potential directory traversal issues.

* modules/pam_timestamp/pam_timestamp.c (check_tty): Treat
"." and ".." tty values as invalid.
(get_ruser): Treat "." and ".." ruser values, as well as any ruser
value containing '/', as invalid.

Fixes CVE-2014-2583.

Reported-by: Sebastian Krahmer <krahmer@suse.de>
---
 modules/pam_timestamp/pam_timestamp.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/modules/pam_timestamp/pam_timestamp.c b/modules/pam_timestamp/pam_timestamp.c
index 5193733..b3f08b1 100644
--- a/modules/pam_timestamp/pam_timestamp.c
+++ b/modules/pam_timestamp/pam_timestamp.c
@@ -158,7 +158,7 @@ check_tty(const char *tty)
 		tty = strrchr(tty, '/') + 1;
 	}
 	/* Make sure the tty wasn't actually a directory (no basename). */
-	if (strlen(tty) == 0) {
+	if (!strlen(tty) || !strcmp(tty, ".") || !strcmp(tty, "..")) {
 		return NULL;
 	}
 	return tty;
@@ -243,6 +243,17 @@ get_ruser(pam_handle_t *pamh, char *ruserbuf, size_t ruserbuflen)
 		if (pwd != NULL) {
 			ruser = pwd->pw_name;
 		}
+	} else {
+		/*
+		 * This ruser is used by format_timestamp_name as a component
+		 * of constructed timestamp pathname, so ".", "..", and '/'
+		 * are disallowed to avoid potential path traversal issues.
+		 */
+		if (!strcmp(ruser, ".") ||
+		    !strcmp(ruser, "..") ||
+		    strchr(ruser, '/')) {
+			ruser = NULL;
+		}
 	}
 	if (ruser == NULL || strlen(ruser) >= ruserbuflen) {
 		*ruserbuf = '\0';
-- 
2.4.0