From: Daniel Axtens Date: Tue, 4 Dec 2018 03:29:42 +0000 (+1100) Subject: Skip 0-length ACL fields X-Git-Tag: v3.4.0~149^2~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=15bf44fd2c1ad0e3fd87048b3fcc90c4dcff1175;p=thirdparty%2Flibarchive.git 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 --- diff --git a/libarchive/archive_acl.c b/libarchive/archive_acl.c index 512beee1f..7beeee86e 100644 --- a/libarchive/archive_acl.c +++ b/libarchive/archive_acl.c @@ -1723,6 +1723,11 @@ 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