alfonmga / gopacker

UPX-like packer written in Go

gopacker

A UPX-like packer to shrink executables.

Quick Start

go get github.com/nirhaas/gopacker
gopacker <executable_to_pack>

How does it work

Packing

• Copy gopacker executable itself to output file.
• Compress and stream (append) to output file.
• Append compressed size.
• Append magic string.

Output file is now a functional executable.

Unpacking

When running the packed executable:

• Checks the last few bytes to see if magic string is there.
• Reading compressed size.
• Reading compressed data.
• Uncompressing to memory.
• Overriding the packed executable.
• syscall exec to run the unpacked executable.

Possible TODO:

• Better compression.
• Encryption.