Re: Preventing exploitation with rebasing

[Bugtraq User <bq () soft-analysts com>]

> Going back to exe image files and rebasing. Surely they can be rebased even
> without a .reloc section? All I need to do is edit the image base in the PE
> header then parse the assembly looking for absolute addresses such as
> function addresses, static variables etc and modify these addresses, too.

I'm sorry but I don't think this is feasible in real life.  In a test 
program it may seem possible, but try and apply it to a real PE executable 
that actually does something and you will see that it is not.  To even 
begin to do what you suggest, you would need to:

1) Write a functional disassembler that understands instruction 
boundaries and knows which instructions reference absolute addresses 
(easy).

2) Understand parts of the code section that are not assembly 
instructions, such as JMP tables used by switch statements, and similar 
constructs (getting harder).

3) Understand and be able to predict unknown data types, or infer their 
data type by where they may or may not be referenced within code (quite 
difficult).

How do you know if \x44\x42\x41\x00 within a .data section is an absolute 
address 0x414244 or if it is actually the string DBA\0?

For all that effort, you might as well develop a more worthwhile security 
measure.