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Re: MSBlast complete recode / analysis
From: H D Moore <sflist () digitaloffense net>
Date: Thu, 14 Aug 2003 15:39:24 -0500
On Thursday 14 August 2003 01:19 am, Rolf Rolles wrote:
MSBlast was compiled with LCC 1.x, which made it particularly easy to
analyze. The exploit encrypts itself via XOR. A few simple
modifications to the "Ripper" IDC on datarescue's site takes care of
The "encryption" only exists to prevent certain characters from ending up
in the payload. The source code for the xor encoder is public and part of
the Pex.pm module in the Releases section of the metasploit.com web site.
The shellcode binds cmd.exe to 135, and the attacker sends the
Not so, the shellcode creates a new socket on port 4444 and binds cmd.exe.
And the analysis of the exploit itself: (the comments became sparse
when I realized that the code was ripped from HalVar (URL is below)).
The code was not ripped from HalVar, but the universal loader code was
borrowed from a friend (and tweaked). As you can see from the comments
below, the ScanForApi stuff wasn't originally from HalVar or even LSD.
The hashing algorithm I use has four-byte keys, HalVar used two-byte
keys. There are a number of other huge differences in the bindshell code
(since I wrote mine from scratch).
mov eax, [fs:ecx]
; find kernelbase
; stolen from LSD who stole it from VX... it's a pity
The shellcode and xor encoder source code is available from the
metasploit.com web site. The relevant URL's are:
(slightly different from the version used in dcom.c)
(the LongXorDecoder routine)
Blah. Worms suck.
On Thursday 14 August 2003 11:49 am, Rolles, Rolf wrote:
since bugtraq is slow in accepting this, here it is.\
- Re: MSBlast complete recode / analysis H D Moore (Aug 14)