Author: David Zimmer
Date: 01.20.12 - 6:08pm
Not sure if I blogged about this yet or not but there is an interesting nuance to Win7 x64 when running 32 bit applications.
In older versions of windows (and even 32bit Win7) when dlls are loaded, the entire image size is mapped into memory as one continuous block then the different sections are given the various permissions. The dll handle as returned from LoadLibrary or GetModuleHandle are actually the base address of the dll starting at the MZ headers. You can reference any byte within imagesize without worry.
The other day when testing scdbg on a Win7 x64 system, I was getting a strange crash so did a little probing. It turns out that 32 bit applications running on a x64 system are mapped differently. Each PE section is now explicitly mapped in with unallocated gaps between sections (if there were any as defined in teh pe section table)
I had been grabbing live copies of kernel32.text and ntdll.text and stuffing them into the emulator memory for quick and dirty support for some shellcodes which did return address scanning, I have since killed several birds with one stone and now load the proper code sections from compiled in resources. (at the cost of about 500k in size after upx compression)
Granted it was a dirty technique doing a not so recommended thing, but it had been stable since at least win2k and probably win98. Nuances aint they grand!