Segmentation fault when unpacking DXT5Crunched texture

[na-ji]

Code

import os
import UnityPy

env = UnityPy.load("./my_asset_bundle")

for obj in env.objects:
    # process specific object types
    if obj.type.name in ["Texture2D", "Sprite"]:
        # parse the object data
        data = obj.read()

        # create destination path
        dest = os.path.join("./dest", data.name)

        # make sure that the extension is correct
        # you probably only want to do so with images/textures
        dest, _ = os.path.splitext(dest)
        dest = dest + ".png"

        img = data.image
        img.save(dest)

Error

Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

This error is happening on the line img = data.image

Bug
The image should be read successfully without crashing the whole script. When I checked m_TextureFormat attribute, the returned value was 29. I've tried with others tools like AssetRipper, and they can extract everything without issue. Also, I tried to disable the C-typetree reader, but the segmentation fault is still occurring.

To Reproduce
my_asset_bundle.zip
I zipped the file to make GitHub accepts it. You need to unzip it first.

• Python version: 3.10.6
• UnityPy version: 1.10.3
• OS: macos Sonoma 14.0 on M1 Macbook pro

[K0lb3]

This is a bit tricky to fix, as this is one of the kinds of segfaults that are a bit random and happen only under hard to reproduce conditions. (Or in other words, I can't reproduce the issue, but I see that it could happen due to potato code in dependencies)

Can you check where the segfault happens specifically, during de-crunching or during the texture parsing by PIL?

[na-ji]

I've asked a colleague to test on his PC, and for him everything worked. He is on Windows while I'm on an M1 MacBook Pro. The difference might come from different OS + different architecture (arm vs amd).
I will try to debug ASAP to tell you from which line it's coming.

PS: Sorry for the delay, I didn't get any notification.

[na-ji]

Can you check where the segfault happens specifically, during de-crunching or during the texture parsing by PIL?

The segfault happens during de-crunching on this line

UnityPy/UnityPy/export/Texture2DConverter.py

Line 128 in 99c240c

image_data = texture2ddecoder.unpack_unity_crunch(image_data)

[K0lb3]

Thanks for the info.

And, well, this is pretty troublesome then, because the de-crunching is pure Unity code, so bug hunting it will be a nightmare.
The only "simple" solution would be making a python wrapper for the Rust rewrite of the texture2ddecoder, which includes a rewrite of the crunch code. This version is memory safe for sure.
It might take some time until I come around to this though.

[K0lb3]

Finished soon™️