From 3800cdbaf04b775b091b4b88a40933a2aa800a90 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Tue, 4 Dec 2018 14:29:42 +1100
Subject: [PATCH] Skip 0-length ACL fields
Currently, it is possible to create an archive that crashes bsdtar
with a malformed ACL:
Program received signal SIGSEGV, Segmentation fault.
archive_acl_from_text_l (acl=<optimised out>, text=0x7e2e92 "", want_type=<optimised out>, sc=<optimised out>) at libarchive/archive_acl.c:1726
1726 switch (*s) {
(gdb) p n
$1 = 1
(gdb) p field[n]
$2 = {start = 0x0, end = 0x0}
Stop this by checking that the length is not zero before beginning
the switch statement.
I am pretty sure this is the bug mentioned in the qsym paper [1],
and I was able to replicate it with a qsym + AFL + afl-rb setup.
[1] https://www.usenix.org/conference/usenixsecurity18/presentation/yun
---
libarchive/archive_acl.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/libarchive/archive_acl.c b/libarchive/archive_acl.c
index fe42b9b8..cb23ad88 100644
--- a/libarchive/archive_acl.c
+++ b/libarchive/archive_acl.c
@@ -1711,6 +1711,11 @@ archive_acl_from_text_l(struct archive_acl *acl, const char *text,
st = field[n].start + 1;
len = field[n].end - field[n].start;
+ if (len == 0) {
+ ret = ARCHIVE_WARN;
+ continue;
+ }
+
switch (*s) {
case 'u':
if (len == 1 || (len == 4
--
2.17.1