ALLO ALLO WS_FTP Server

From: Hugh Mann (hughmann_at_hotmail.com)
Date: 03/23/04

  • Next message: Hugh Mann: "Open the WS_FTP Server backdoor to SYSTEM"
    To: full-disclosure@lists.netsys.com, bugtraq@securityfocus.com
    Date: Tue, 23 Mar 2004 07:13:29 +0000
    
    
    

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Advisory Name: ALLO ALLO WS_FTP Server
    Impact : Arbitrary code execution as SYSTEM
    Discovered by: Hugh Mann hughmann@hotmail.com
    Tested progs : Ipswitch WS_FTP Server 4.0.2.EVAL
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Description
    ~~~~~~~~~~~
    A user who can upload files, and also has a max number of files limit or max
    total file size limit, can read any memory address the WS_FTP Server can
    read. With the right address, the user can cause a buffer overflow and
    execute arbitrary code as SYSTEM.

    Details
    ~~~~~~~
    There's a vulnerability in the ALLO handler when it sends an error string to
    the client. Instead of pushing an ASCIIZ string, it pushes a 64-bit value
    equal to total size of all files in user's dir and any sub-dirs. This is a
    value we can easily control if we exploit the WS_FTP Server REST
    vulnerability. If we change this value to a string of size equal to ~256
    bytes, we can overwrite the return address and execute arbitrary code as
    SYSTEM.

    Exploit
    ~~~~~~~
    See the attached source code.

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