Modifying Linux-Based XVR Device Firmware: .img Extraction, SquashFS issues

[hamuz]

Hello,

I'm working on analyzing and modifying a Linux-based firmware file for an XVR recording device using WSL, but I'm encountering several issues with extracting and accessing files in the .img firmware file.

Binwalk Extraction Issue: I've tried using Binwalk for extraction, but instead of the expected squashfs file structure, I end up with dozens of .zlib files. Each .zlib file contains additional nested .zlib files, creating a "matryoshka doll" effect. I also tried using the mount method, but it fails to recognize the squashfs format and does not open it correctly.

7z and LZMA Issue: There is a 257C65.7z file within the firmware, which I believe might contain the operating system. This 7z file has an LZMA file inside, but I can't extract it or access its contents. When I attempt to open it with 7zip, I receive a data error, and LZMA doesn't recognize it as a valid LZMA file.

I'm having trouble identifying the root causes of these issues. If anyone has encountered similar problems or knows of alternative methods or tools that might work—especially for XVR device firmware—any advice would be greatly appreciated. 

Thank you in advance!