I already asked a similar question but after a deeper analysis of the filesystem I found out that I misunderstood the problem and that's why I decided to delete the old question and make a new one.
I extracted a squashfs filesystem from a NAND Flash with binwalk. The problem was that I couldn't see the files that it contains, even sasquatch wasn't able to extract the files.
That's why I assumed that I was dealing with a vendor hacked version of squashfs that sasquatch couldn't handle.
However after a deeper analysis I found out that the extracted squashfs filesystem was looking very suspicious to me due to two things.
First of all it starts with a generic squashfs header but right after the header there is a large sequence of 0xFF Bytes that is interrupted by a 0x01 Byte every 17. Byte.
Besides of that the whole sequence is interrupted periodically by some kind of UBI signature.
You can see this in the picture.
The second thing that looked suspicious to me was that after the large sequence mentioned above the UBI signature kept appearing periodically (until the end ) through the whole part that is supposed to be what the suqashfs contains. (the signature is sometimes different from each other but still very similar).
I also know from the boot process analysis that the rootfs of the device is mounted on top of a UBI volume:
root=/dev/ubiblock0_1 noinitrd ro ubi.mtd=6 mtdparts=spi0.0:256k(u-boot),64k(u-boot-env),128k(reserved),64k(art);spi0.1:5m(kernel0),5m(kernel1),118m(ubi) rootfstype=squashfs ubi.block=0,1 mem=64M
Has the UBI signature that is appearing through the entire squashfs file something to do with the fact that it is mounted on top of a UBI volume and how do I deal with that?
Or how can I mount it/is it possible to mount it like this?