goblin-ext

Binary modification utilities built on goblin.

This crate provides programmatic access to binary modification workflows typically done via command-line tools:

• Mach-O binaries (macOS/iOS): Functionality similar to Apple's install_name_tool
• ELF binaries (Linux/BSD): Functionality similar to patchelf

Features

• Modify dylib install names and dependencies (Mach-O)
• Add, remove, and modify runtime search paths (rpath)
• Change SONAME entries (ELF)
• Convert between RPATH and RUNPATH (ELF)
• Ad-hoc code signing support (Mach-O, with codesign feature)
• Support for both 32-bit and 64-bit binaries
• Support for FAT/universal binaries (Mach-O)
• Smart relocation strategies to handle growing sections
• no_std compatible (with alloc)

Installation

Add this to your Cargo.toml:

[dependencies]
goblin-ext = "0.1"

Feature Flags

Feature	Default	Description
std	Yes	Standard library support
mach	Yes	Mach-O binary support
elf	Yes	ELF binary support
codesign	No	Ad-hoc code signing for Mach-O binaries

Usage

Mach-O Example

use goblin_ext::MachOWriter;

let data = std::fs::read("libfoo.dylib")?;
let mut writer = MachOWriter::new(data)?;

// Change the install name
writer.change_id("@rpath/libfoo.dylib")?;

// Modify a dependency path
writer.change_dylib("/usr/lib/libold.dylib", "/usr/local/lib/libnew.dylib")?;

// Add an rpath
writer.add_rpath("@loader_path/../lib")?;

// Build the modified binary
let output = writer.build()?;
std::fs::write("libfoo_modified.dylib", output)?;

ELF Example

use goblin::elf::Elf;
use goblin_ext::ElfWriter;

let data = std::fs::read("binary")?;
let elf = Elf::parse(&data)?;
let mut writer = ElfWriter::new(&data, &elf)?;

// Set the RUNPATH
writer.set_rpath("/usr/local/lib")?;

// Or set multiple paths
writer.set_rpath("/usr/local/lib:/opt/lib")?;

// Write the modified binary
let output = writer.write()?;
std::fs::write("binary_modified", output)?;

FAT Binary Support (Mach-O)

use goblin_ext::modify_fat_binary;

let data = std::fs::read("universal.dylib")?;
let output = modify_fat_binary(&data, |writer| {
    writer.change_id("@rpath/universal.dylib")?;
    writer.add_rpath("@loader_path/../lib")?;
    Ok(())
})?;
std::fs::write("universal_modified.dylib", output)?;

API Overview

MachOWriter

Method	Description
get_id()	Get the binary's install name
change_id(name)	Change the dylib install name
get_dylibs()	List all dylib dependencies
change_dylib(old, new)	Modify a dependency path
delete_dylib(name)	Remove a dependency
add_dylib(name, kind)	Add a new dependency
get_rpaths()	List all runtime search paths
add_rpath(path)	Add an rpath
delete_rpath(path)	Remove an rpath
change_rpath(old, new)	Modify an rpath
build()	Serialize the modified binary

ElfWriter

Method	Description
set_rpath(path)	Set DT_RUNPATH (or DT_RPATH)
set_rpath_forced(path)	Force DT_RPATH instead of DT_RUNPATH
set_soname(name)	Set DT_SONAME
remove_rpath()	Remove DT_RPATH
remove_runpath()	Remove DT_RUNPATH
rpath_to_runpath()	Convert DT_RPATH to DT_RUNPATH
runpath_to_rpath()	Convert DT_RUNPATH to DT_RPATH
write()	Write the modified binary

Examples

The crate includes two example CLI tools:

install_name_tool

A Rust implementation of Apple's install_name_tool:

cargo run --example install_name_tool --features codesign -- \
    -id @rpath/libfoo.dylib \
    -add_rpath @loader_path/../lib \
    -change /usr/lib/libold.dylib /usr/local/lib/libnew.dylib \
    libfoo.dylib -o libfoo_modified.dylib

patchelf

A Rust implementation of patchelf:

cargo run --example patchelf -- set-rpath /usr/local/lib binary -o binary_modified
cargo run --example patchelf -- print-rpath binary
cargo run --example patchelf -- rpath-to-runpath binary -o binary_modified

Use Cases

• CI/CD pipelines: Automate binary patching as part of build processes
• Cross-compilation: Fix library paths for different deployment environments
• Package management: Relocate binaries to new install prefixes
• Development: Test binaries with different library versions

Minimum Supported Rust Version

This crate requires Rust 1.90.0 or later.

License

Licensed under the MIT License. See LICENSE for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.