Say I have a disk image (possibly partitioned) that I have permission to read. However, I don't have permission to mount it via loopback*. In theory, the data is all there; I could write code that resembles the Linux kernel's, partition editors and
mount's own code to parse the image, look for partitions, interpret the filesystem and extract a file. But does such a tool already exist for GNU/Linux systems?
*Really, I'm in the position of writing tools to deal with it, and I don't want to (a) assume that the user of those tools can
sudo and (b) require them to
sudo where it might not be necessary.
(If the answer changes depending on filesystem,
ext2-4 is more important to me. But answers that cover multiple popular filesystems will be preferred.)