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Fix various crash, memory corruption and infinite loop conditions #1105

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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
  • Loading branch information
daxtens committed Dec 11, 2018
commit 15bf44fd2c1ad0e3fd87048b3fcc90c4dcff1175
5 changes: 5 additions & 0 deletions libarchive/archive_acl.c
Expand Up @@ -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
Expand Down