1From bd68ae1271598e8fdc72f2adb457e6882604582d Mon Sep 17 00:00:00 2001
2From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
3Date: Thu, 22 Feb 2018 16:39:43 +0100
4Subject: [PATCH] Fix a heap-buffer-overflow in find_archive()
5MIME-Version: 1.0
6Content-Type: text/plain; charset=UTF-8
7Content-Transfer-Encoding: 8bit
8
9rw_buffer has allocated rw_base_size bytes. But subsequend fgets() in
10find_archive() reads up-to BUFSIZ bytes.
11
12On my system, BUFSIZ is 8192. rw_base_size is usually equaled to
13a memory page size, 4096 on my system. Thus find_archive() can write
14beyonded allocated memmory for rw_buffer array:
15
16$ valgrind -- ./unshar /tmp/id\:000000\,sig\:06\,src\:000005+000030\,op\:splice\,rep\:4
17==30582== Memcheck, a memory error detector
18==30582== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
19==30582== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
20==30582== Command: ./unshar /tmp/id:000000,sig:06,src:000005+000030,op:splice,rep:4
21==30582==
22==30582== Invalid write of size 1
23==30582==    at 0x4EAB480: _IO_getline_info (in /usr/lib64/libc-2.27.so)
24==30582==    by 0x4EB47C2: fgets_unlocked (in /usr/lib64/libc-2.27.so)
25==30582==    by 0x10BF60: fgets_unlocked (stdio2.h:320)
26==30582==    by 0x10BF60: find_archive (unshar.c:243)
27==30582==    by 0x10BF60: unshar_file (unshar.c:379)
28==30582==    by 0x10BCCC: validate_fname (unshar-opts.c:604)
29==30582==    by 0x10BCCC: main (unshar-opts.c:639)
30==30582==  Address 0x523a790 is 0 bytes after a block of size 4,096 alloc'd
31==30582==    at 0x4C2DBBB: malloc (vg_replace_malloc.c:299)
32==30582==    by 0x10C670: init_unshar (unshar.c:450)
33==30582==    by 0x10BC55: main (unshar-opts.c:630)
34
35This was reported in
36<http://lists.gnu.org/archive/html/bug-gnu-utils/2018-02/msg00004.html>.
37
38CVE: CVE-2018-1000097
39Upstream-Status: Inappropriate [no upstream]
40Signed-off-by: Petr Písař <ppisar@redhat.com>
41Signed-off-by: Sinan Kaya <okaya@kernel.org>
42---
43 src/unshar.c | 2 +-
44 1 file changed, 1 insertion(+), 1 deletion(-)
45
46diff --git a/src/unshar.c b/src/unshar.c
47index 80bc3a9..0fc3773 100644
48--- a/src/unshar.c
49+++ b/src/unshar.c
50@@ -240,7 +240,7 @@ find_archive (char const * name, FILE * file, off_t start)
51       off_t position = ftello (file);
52
53       /* Read next line, fail if no more and no previous process.  */
54-      if (!fgets (rw_buffer, BUFSIZ, file))
55+      if (!fgets (rw_buffer, rw_base_size, file))
56 	{
57 	  if (!start)
58 	    error (0, 0, _("Found no shell commands in %s"), name);
59--
602.19.0
61
62