#x86 #x64 #rop #jop #gadget

bin+lib xgadget

Fast, parallel, cross-variant ROP/JOP gadget search for x86/x64 binaries

9 releases (4 breaking)

0.5.1 Jun 12, 2021
0.5.0 Feb 7, 2021
0.4.0 Nov 16, 2020
0.3.0 Nov 11, 2020
0.1.1 Jun 30, 2020

#113 in Development tools

43 downloads per month

MIT license

105KB
2K SLoC

xgadget

crates.io GitHub Actions

Fast, parallel, cross-variant ROP/JOP gadget search for x86 (32-bit) and x64 (64-bit) binaries. Uses the iced-x86 disassembler library.

Current state: decent test coverage, but still in beta. Issues/PRs welcome :)

About

To the best of my knowledge, xgadget is the first gadget search tool to have these features:

  • JOP search uses instruction semantics - not hardcoded regex for individual encodings
    • Optionally filter to JOP "dispatcher" gadgets with flag --dispatcher
  • Finds gadgets that work across multiple variants of a binary (e.g. different program or compiler versions)
    • Full-match - Same instruction sequence, same program counter: gadget fully re-usable.
      • E.g. pop rsp; add [rax-0x77], cl; ret ------------------------------------- [ 0xc748d ]
    • Partial-match - Same instruction sequence, different program counter: gadget logic portable.
      • E.g. pop rsp; add [rax-0x77], cl; ret; --- [ 'bin_v1.1': 0xc748d, 'bin_v1.2': 0xc9106 ]
    • This is entirely optional, you're free to run this tool on a single binary.
  • The stack pointer is explicitly colored in terminal output, for workflow convenience.

Other features include:

  • Both library API and CLI tool
  • Supports ELF32, ELF64, PE32, PE32+ [1], and raw files
  • Parallel across available cores [2], whether searching a single binary or multiple variants
  • CI/CD for automated integration test and binary releases (Linux, 64-bit) [3]
  • Statistical benchmark harness for performance tuning [4]
  • 8086/x86/x64 only, uses a speed-optimized disassembly backend [5]

API Usage

Find gadgets:

use xgadget;

let max_gadget_len = 5;

// Search single binary
let search_config = xgadget::SearchConfig::DEFAULT;
let bin_1 = xgadget::Binary::from_path_str("/path/to/bin_v1").unwrap();
let bins = vec![bin_1];
let gadgets = xgadget::find_gadgets(&bins, max_gadget_len, search_config).unwrap();
let stack_pivot_gadgets = xgadget::filter_stack_pivot(&gadgets);

// Search for cross-variant gadgets, including partial matches
let search_config = xgadget::SearchConfig::DEFAULT | xgadget::SearchConfig::PART;
let bin_1 = xgadget::Binary::from_path_str("/path/to/bin_v1").unwrap();
let bin_2 = xgadget::Binary::from_path_str("/path/to/bin_v2").unwrap();
let bins = vec![bin_1, bin_2];
let cross_gadgets = xgadget::find_gadgets(&bins, max_gadget_len, search_config).unwrap();
let cross_reg_pop_gadgets = xgadget::filter_reg_pop_only(&cross_gadgets);

Custom filters can be created using the GadgetAnalysis object and/or functions from the semantics module. How the above filter_stack_pivot function is implemented:

use rayon::prelude::*;
use iced_x86;
use xgadget::{Gadget, GadgetAnalysis};

/// Parallel filter to gadgets that write the stack pointer
pub fn filter_stack_pivot<'a>(gadgets: &[Gadget<'a>]) -> Vec<Gadget<'a>> {
   gadgets
       .par_iter()
       .filter(|g| {
           let regs_overwritten = GadgetAnalysis::new(&g).regs_overwritten();
           if regs_overwritten.contains(&iced_x86::Register::RSP)
               || regs_overwritten.contains(&iced_x86::Register::ESP)
               || regs_overwritten.contains(&iced_x86::Register::SP)
           {
               return true;
           }
           false
       })
       .cloned()
       .collect()
}

CLI Usage

Run xgadget --help:

xgadget v0.5.0

About:    Fast, parallel, cross-variant ROP/JOP gadget search for x86/x64 binaries.
Cores:    8 logical, 8 physical

USAGE:
   xgadget [FLAGS] [OPTIONS] <FILE(S)>...

FLAGS:
   -t, --att              Display gadgets using AT&T syntax [default: Intel syntax]
   -c, --check-sec        Run checksec on the 1+ binaries instead of gadget search
   -d, --dispatcher       Filter to potential JOP 'dispatcher' gadgets [default: all]
   -e, --extended-fmt     Print in terminal-wide format [default: only used for partial match search]
   -h, --help             Prints help information
       --inc-call         Include gadgets containing a call [default: don't include]
       --inc-imm16        Include '{ret, ret far} imm16' (e.g. add to stack ptr) [default: don't include]
   -j, --jop              Search for JOP gadgets only [default: ROP, JOP, and SYSCALL]
   -n, --no-color         Don't color output [default: color output]
       --param-ctrl       Filter to gadgets that control function parameters [default: all]
   -m, --partial-match    Include cross-variant partial matches [default: full matches only]
       --reg-pop          Filter to 'pop {reg} * 1+, {ret or ctrl-ed jmp/call}' gadgets [default: all]
   -r, --rop              Search for ROP gadgets only [default: ROP, JOP, and SYSCALL]
   -p, --stack-pivot      Filter to gadgets that write the stack ptr [default: all]
   -s, --sys              Search for SYSCALL gadgets only [default: ROP, JOP, and SYSCALL]
   -V, --version          Prints version information

OPTIONS:
   -a, --arch <ARCH>               For raw (no header) files: specify arch ('x8086', 'x86', or 'x64') [default: x64]
   -b, --bad-bytes <BYTE(S)>...    Filter to gadgets whose addrs don't contain given bytes [default: all]
   -l, --max-len <LEN>             Gadgets up to LEN instrs long. If 0: all gadgets, any length [default: 5]
       --no-deref <OPT_REG>        Filter to gadgets that don't deref any regs or a specific reg [default: all]
       --reg-ctrl <OPT_REG>        Filter to gadgets that control any reg or a specific reg [default: all]
   -f, --regex-filter <EXPR>       Filter to gadgets matching a regular expression

ARGS:
   <FILE(S)>...    1+ binaries to gadget search. If > 1: gadgets common to all

CLI Build and Install (Recommended)

Build a dynamically-linked binary from source and install it locally:

cargo install xgadget --features cli-bin    # Build on host (pre-req: https://www.rust-lang.org/tools/install)

CLI Binary Releases for Linux

Commits to this repo's master branch automatically run integration tests and build a statically-linked binary for 64-bit Linux. You can download it here to try out the CLI immediately, instead of building from source. Static binaries for Windows may also be supported in the future.

Unfortunately the statically-linked binary is several times slower on an i7-9700K, likely due to the built-in memory allocator for target x86_64-unknown-linux-musl. So building a dynamically-linked binary from source with the above cargo install command is highly recommended for performance (links against your system's allocator).

Why No Chain Generation?

Tools that attempt to automate ROP chain generation require heavyweight analysis - typically symbolic execution of an intermediate representation. While this works well for small binaries and CTF problems, it tends to be slow and difficult to scale for large, real-world programs. At present, xgadget has a different goal: enable an expert user to manually craft stable exploits by providing fast, accurate gadget discovery.

Yeah, but can it do 10 OS kernels under 10 seconds?! Repeatable Benchmark Harness

bash ./benches/bench_setup_ubuntu.sh     # Ubuntu-specific, download/build 10 kernel versions
cargo bench                              # Grab a coffee, this'll take a while...
  • bench_setup_ubuntu.sh downloads and builds 10 consecutive Linux kernels (versions 5.0.1 to 5.0.10 - with x86_64_defconfig).
  • cargo bench, among other benchmarks, searches all 10 kernels for common gadgets.

On an i7-9700K (8C/8T, 3.6GHz base, 4.9 GHz max) machine with gcc version 8.4.0: the average runtime, to process all ten 54MB kernels simultaneously with a max gadget length of 5 instructions and full-match search for all gadget types (ROP, JOP, and syscall gadgets), is only 6.3 seconds! Including partial matches as well takes just 7.9 seconds.

Acknowledgements

This project started as an optimized solution to Chapter 8, exercise 3 of "Practical Binary Analysis" by Dennis Andreisse [6], and builds on the design outlined therein.

References

Dependencies

~13MB
~283K SLoC