backhand

Library and binaries for the reading, creating, and modification of SquashFS file systems.

Library

Add the following to your Cargo.toml file: toml [dependencies] backhand = "0.10.0"

Reading/Writing/Modifying Firmware

```rust,no_run use std::fs::File; use std::io::Cursor; use backhand::{FilesystemReader, FilesystemWriter, NodeHeader};

// read let file = File::open("file.squashfs").unwrap(); let readfilesystem = FilesystemReader::fromreader(file).unwrap();

// convert to writer let mut writefilesystem = FilesystemWriter::fromfsreader(&readfilesystem).unwrap();

// add file with data from slice let d = NodeHeader::default(); let bytes = Cursor::new(b"Fear is the mind-killer."); writefilesystem.pushfile(bytes, "a/d/e/new_file", d);

// add file with data from file let newfile = File::open("dune").unwrap(); writefilesystem.pushfile(newfile, "/root/dune", d);

// modify file let bytes = Cursor::new(b"The sleeper must awaken.\n"); writefilesystem.replacefile("/a/b/c/d/e/first_file", bytes).unwrap();

// write into a new file let mut output = File::create("modified.squashfs").unwrap(); write_filesystem.write(&mut output).unwrap(); ```

Binaries

These are currently under development and are missing features, MR's welcome!

To install, run cargo install backhand --locked.

unsquashfs-backhand

```no_test tool to uncompress, extract and list squashfs filesystems

Usage: unsquashfs [OPTIONS]

Arguments: Squashfs file

Options: -o, --offset Skip BYTES at the start of FILESYSTEM [default: 0] -l, --list List filesystem, do not write to DEST -d, --dest Extract to [PATHNAME] [default: squashfs-root] -i, --info Print files as they are extracted -f, --force If file already exists then overwrite -s, --stat Display filesystem superblock information -h, --help Print help information -V, --version Print version information ```

add-backhand

```no_test tool to add files to squashfs filesystems

Usage: add [OPTIONS]

Arguments: Squashfs input image Path of file to read, to write into squashfs Path of file inserted into squashfs

Options: -o, --out Squashfs output image [default: added.squashfs] -h, --help Print help -V, --version Print version ```

replace-backhand

```no_test tool to replace files in squashfs filesystems

Usage: replace [OPTIONS]

Arguments: Squashfs input image Path of file to read, to write into squashfs Path of file replaced in image

Options: -o, --out Squashfs output image [default: replaced.squashfs] -h, --help Print help -V, --version Print version ```

Testing

This library is extensively tested with all library features and images from openwrt and extracted from manufacturers devices.

To run basic tests, use cargo test --release. To start fuzzing, run cargo fuzz list then pick one! Then start with cargo fuzz run [NAME].