Author: des
Date: Sat Mar 12 23:50:19 2016
New Revision: 296780
URL: https://svnweb.freebsd.org/changeset/base/296780
Log:
Apply patch from 7.2p2 for xauth command injection bug.
Security: CVE-2016-3115
Modified:
stable/9/crypto/openssh/session.c
Modified: stable/9/crypto/openssh/session.c
==============================================================================
--- stable/9/crypto/openssh/session.c Sat Mar 12 23:25:05 2016
(r296779)
+++ stable/9/crypto/openssh/session.c Sat Mar 12 23:50:19 2016
(r296780)
@@ -48,6 +48,7 @@ __RCSID("$FreeBSD$");
#include <arpa/inet.h>
+#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
@@ -294,6 +295,21 @@ do_authenticated(Authctxt *authctxt)
do_cleanup(authctxt);
}
+/* Check untrusted xauth strings for metacharacters */
+static int
+xauth_valid_string(const char *s)
+{
+ size_t i;
+
+ for (i = 0; s[i] != '\0'; i++) {
+ if (!isalnum((u_char)s[i]) &&
+ s[i] != '.' && s[i] != ':' && s[i] != '/' &&
+ s[i] != '-' && s[i] != '_')
+ return 0;
+ }
+ return 1;
+}
+
/*
* Prepares for an interactive session. This is called after the user has
* been successfully authenticated. During this message exchange, pseudo
@@ -367,7 +383,13 @@ do_authenticated1(Authctxt *authctxt)
s->screen = 0;
}
packet_check_eom();
- success = session_setup_x11fwd(s);
+ if (xauth_valid_string(s->auth_proto) &&
+ xauth_valid_string(s->auth_data))
+ success = session_setup_x11fwd(s);
+ else {
+ success = 0;
+ error("Invalid X11 forwarding data");
+ }
if (!success) {
free(s->auth_proto);
free(s->auth_data);
@@ -2199,7 +2221,13 @@ session_x11_req(Session *s)
s->screen = packet_get_int();
packet_check_eom();
- success = session_setup_x11fwd(s);
+ if (xauth_valid_string(s->auth_proto) &&
+ xauth_valid_string(s->auth_data))
+ success = session_setup_x11fwd(s);
+ else {
+ success = 0;
+ error("Invalid X11 forwarding data");
+ }
if (!success) {
free(s->auth_proto);
free(s->auth_data);
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