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