Image4 (Swift)

A Swift library and CLI tool for parsing and creating Apple's Image4 format.

This project is a Swift reimplementation of PyIMG4.

Features

• Parse & Create: Supports IMG4 containers, IM4P payloads, IM4M manifests, and IM4R restore info.
• Compression: Native support for LZSS and LZFSE (using Apple's Compression framework).
• Security: Handles encrypted payloads and keybag parsing.
• CLI: A powerful command-line interface for managing Image4 files.
• Modern Swift: Built with Swift 6.2 and Apple/Swift-ASN1.

Requirements

• Swift 6.2 or later
• macOS (requires native Compression and CommonCrypto frameworks)

Installation

Swift Package Manager

Add the following to your Package.swift dependencies:

.package(url: "https://github.com/p1atdev/Image4.git", from: "1.0.0"),

CLI Tool

git clone https://github.com/p1atdev/Image4.git
cd Image4
swift build -c release
cp .build/release/image4 /usr/local/bin/

Usage

Command Line Interface

USAGE: image4 <subcommand>

OPTIONS:
  -h, --help      Show help information.

SUBCOMMANDS:
  im4m            Image4 manifest commands.
  im4p            Image4 payload commands.
  im4r            Image4 restore info commands.
  img4            Image4 commands.

Example: Inspect an Image4 file

image4 img4 info -i kernelcache.release.iphone10b

Library API

Parsing an IM4P Payload

import Image4
import Foundation

let data = try Data(contentsOf: URL(fileURLWithPath: "kernelcache.im4p"))
let im4p = try IM4P(data: data)

print("FourCC: \(im4p.fourcc ?? "unknown")")

if let payload = im4p.payload {
    if payload.compression == .lzfse {
        try payload.decompress()
    }
    print("Decoded payload size: \(payload.data.count) bytes")
}

Creating an Image4 Container

import Image4

let im4p = IM4P()
im4p.fourcc = "krnl"
im4p.payload = IM4PData(data: rawData)
try im4p.payload?.compress(to: .lzfse)

let im4m = try IM4M(data: shshData)

let img4 = IMG4()
img4.im4p = im4p
img4.im4m = im4m

let finalData = try img4.output()

Credits

• PyIMG4 by @m1stadev for the original implementation and reference.
• LZSS for the Swift LZSS support.

License

This project is licensed under the MIT License - see the LICENSE file for details.