[FASM1] Setting PE Characteristics from Source Code

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nicebyte

Joined: 03 Jun 2022
Posts: 3

nicebyte 10 Feb 2025, 08:40

Hello,

I am writing some position independent code that I am compiling into a PE binary using FASM1.

I currently have to perform additional manipulations with the PE headers in order to make Windows engage ASLR for my binary, which is a bit annoying.

Is there some way to change PE Characteristics and DllCharacteristics from within my .asm file?

10 Feb 2025, 08:40

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20517
Location: In your JS exploiting you and your system

revolution 10 Feb 2025, 09:31

Inside the asm file there isn't a way to access the PE header.

Code:

format pe console
load x byte from $$

Code:

flat assembler  version 1.73.31  (16384 kilobytes memory)
test.asm [2]:
load x byte from $$
processed: load x byte from $$
error: value out of range.

10 Feb 2025, 09:31

Mat Quasar

Joined: 15 Dec 2024
Posts: 87

Mat Quasar 10 Feb 2025, 09:55

If you use fasm2 or fasmg, you can modify from basic.asm in chapter1.zip.

https://board.flatassembler.net/topic.php?t=20690

10 Feb 2025, 09:55

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 10 Feb 2025, 10:07

Mat Quasar wrote:

If you use fasm2 or fasmg, you can modify from basic.asm in chapter1.zip.

Even the standard fasm-compatible PE formatter for fasmg/fasm2 allows to set it up (with "PE.Settings.Characteristics"), like here:
https://github.com/tgrysztar/fasmg/blob/master/packages/aarch64/mixed.asm

10 Feb 2025, 10:07

Ali.Z

Joined: 08 Jan 2018
Posts: 772

Ali.Z 10 Feb 2025, 10:26

nicebyte wrote:

Hello,

I am writing some position independent code that I am compiling into a PE binary using FASM1.

I currently have to perform additional manipulations with the PE headers in order to make Windows engage ASLR for my binary, which is a bit annoying.

Is there some way to change PE Characteristics and DllCharacteristics from within my .asm file?

perhaps use a fixups relocation section.

_________________
Asm For Wise Humans

10 Feb 2025, 10:26

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 10 Feb 2025, 11:00

Ali.Z wrote:

perhaps use a fixups relocation section.

ASLR is a bit tricky.

10 Feb 2025, 11:00

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