[linux-pam] pam_timestamp: fix potential directory traversal issue (ticket #27)

[Dmitry V. Levin]

commit 9dcead87e6d7f66d34e7a56d11a30daca367dffb
Author: Dmitry V. Levin <ldv(a)altlinux.org&gt;
Date:   Wed Mar 26 22:17:23 2014 +0000

    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(a)suse.de&gt;

 modules/pam_timestamp/pam_timestamp.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)
---
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';