From 3800cdbaf04b775b091b4b88a40933a2aa800a90 Mon Sep 17 00:00:00 2001 From: Daniel Axtens 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=, text=0x7e2e92 "", want_type=, sc=) 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