Re: Jump back to shellcode Windows overflow

From: chaboyd77at_private
Date: Wed Apr 23 2003 - 20:04:20 PDT

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    In-Reply-To: <3EA57FD0.4010603at_private>
    
    Thanks everyone for the help. 
    
    Tried placing shellcode at end, seemed to not overwrite EIP 
    anymore,strange. 
    Next, tried using a near jump and it works great (besides the fact that I 
    haven't got the shellcode working quite right yet).
     
    //  Near jump to shellcode (approx 422 bytes, jmp near -422)
       char jumpcode [] = 
       "\xE9\x55\xFE\xFF\xFF";
     
    My total buffer (460 bytes,411-414 overwrite EIP) now looks like this 
    (typical addresses):
     
    Top of Stack   NOPS   Shellcode  EIP     **   NOPS   jump
    00fbfddd          fbfde9   fbfe07        fbff87   fbff88         fbff9c
     
    I am attempting to use shellcode from the "Advanced Buffer Overflow" 
    writeup by Litchfield (I changed LoadLibrary and GetProcAddress calls to 
    the right addresses).  I'm worried that I won't have enough space(have 
    about 400 bytes to work with) if I decided to attempt to write my own 
    shellcode. Thanks for the assistance! I will let you know if everything 
    goes good.
     
    David
    
    
    >How about just a short or near jmp?  How many bytes between where EIP 
    lands 
    >and your shellcode?  I.E. jmp -128 or something?  EB 80, I think.
    



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