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custom mutator rust support (#752)

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* custom mutator rust support

* clarify how to view documentation for rust mutators

* remove `FuzzResult` hack and clarify lifetimes of CustomMutator::fuzz

* rename TErr associated tyep to Error to be more idiomatic

* fix warnings

* add example for fallible custom mutator

* make Fallible Custom Mutator the default and implement it's handle_err method by default

* rename CustomMutator::handle_err to handle_error

* add example mutator using lain
This commit is contained in:
julihoh
2021-02-27 15:05:13 +01:00
committed by GitHub
parent 79e02c2a9b
commit a5da9ce42c
15 changed files with 882 additions and 0 deletions
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custom_mutators/rust/.gitignore vendored Normal file
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# Generated by Cargo
# will have compiled files and executables
/target/
# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
Cargo.lock
# These are backup files generated by rustfmt
**/*.rs.bk

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custom_mutators/rust/Cargo.toml Normal file
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[workspace]
members = [
"custom_mutator-sys",
"custom_mutator",
"example",
"example_lain",
]

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custom_mutators/rust/README.md Normal file
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Bindings to create custom mutators in Rust.
These bindings are documented with rustdoc. To view the documentation run
```cargo doc -p custom_mutator --open```.
A minimal example can be found in `example`.
An example using [lain](https://github.com/microsoft/lain) can be found in `example_lain`.
Since lain requires a nightly rust toolchain, you need to set one up before you can play with it.

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custom_mutators/rust/custom_mutator-sys/Cargo.toml Normal file
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[package]
name = "custom_mutator-sys"
version = "0.1.0"
authors = ["Julius Hohnerlein <julihoh@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
[build-dependencies]
bindgen = "0.56"

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custom_mutators/rust/custom_mutator-sys/build.rs Normal file
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extern crate bindgen;
use std::env;
use std::path::PathBuf;
// this code is largely taken straight from the handbook: https://github.com/fitzgen/bindgen-tutorial-bzip2-sys
fn main() {
// Tell cargo to invalidate the built crate whenever the wrapper changes
println!("cargo:rerun-if-changed=wrapper.h");
// The bindgen::Builder is the main entry point
// to bindgen, and lets you build up options for
// the resulting bindings.
let bindings = bindgen::Builder::default()
// The input header we would like to generate
// bindings for.
.header("wrapper.h")
.whitelist_type("afl_state_t")
.blacklist_type(r"u\d+")
.opaque_type(r"_.*")
.opaque_type("FILE")
.opaque_type("in_addr(_t)?")
.opaque_type("in_port(_t)?")
.opaque_type("sa_family(_t)?")
.opaque_type("sockaddr_in(_t)?")
.opaque_type("time_t")
.rustfmt_bindings(true)
.size_t_is_usize(true)
// Tell cargo to invalidate the built crate whenever any of the
// included header files changed.
.parse_callbacks(Box::new(bindgen::CargoCallbacks))
// Finish the builder and generate the bindings.
.generate()
// Unwrap the Result and panic on failure.
.expect("Unable to generate bindings");
// Write the bindings to the $OUT_DIR/bindings.rs file.
let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
bindings
.write_to_file(out_path.join("bindings.rs"))
.expect("Couldn't write bindings!");
}

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custom_mutators/rust/custom_mutator-sys/src/lib.rs Normal file
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#![allow(non_upper_case_globals)]
#![allow(non_camel_case_types)]
#![allow(non_snake_case)]
include!(concat!(env!("OUT_DIR"), "/bindings.rs"));

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custom_mutators/rust/custom_mutator-sys/wrapper.h Normal file
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#include "../../../include/afl-fuzz.h"
#include "../../../include/common.h"
#include "../../../include/config.h"
#include "../../../include/debug.h"

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custom_mutators/rust/custom_mutator/Cargo.toml Normal file
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[package]
name = "custom_mutator"
version = "0.1.0"
authors = ["Julius Hohnerlein <julihoh@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[features]
afl_internals = ["custom_mutator-sys"]
[dependencies]
custom_mutator-sys = { path = "../custom_mutator-sys", optional=true }

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custom_mutators/rust/custom_mutator/src/lib.rs Normal file
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//! Somewhat safe and somewhat ergonomic bindings for creating [AFL++](https://github.com/AFLplusplus/AFLplusplus) [custom mutators](https://github.com/AFLplusplus/AFLplusplus/blob/stable/docs/custom_mutators.md) in Rust.
//!
//! # Usage
//! AFL++ custom mutators are expected to be dynamic libraries which expose a set of symbols.
//! Check out [`CustomMutator`] to see which functions of the API are supported.
//! Then use [`export_mutator`] to export the correct symbols for your mutator.
//! In order to use the mutator, your crate needs to be a library crate and have a `crate-type` of `cdylib`.
//! Putting
//! ```yaml
//! [lib]
//! crate-type = ["cdylib"]
//! ```
//! into your `Cargo.toml` should do the trick.
//! The final executable can be found in `target/(debug|release)/your_crate_name.so`.
//! # Example
//! See [`export_mutator`] for an example.
//!
//! # On `panic`s
//! This binding is panic-safe in that it will prevent panics from unwinding into AFL++. Any panic will `abort` at the boundary between the custom mutator and AFL++.
//!
//! # Access to AFL++ internals
//! This crate has an optional feature "afl_internals", which gives access to AFL++'s internal state.
//! The state is passed to [`CustomMutator::init`], when the feature is activated.
//!
//! _This is completely unsafe and uses automatically generated types extracted from the AFL++ source._
use std::{ffi::CStr, fmt::Debug, os::raw::c_uint};
#[cfg(feature = "afl_internals")]
#[doc(hidden)]
pub use custom_mutator_sys::afl_state;
#[allow(unused_variables)]
#[doc(hidden)]
pub trait RawCustomMutator {
#[cfg(feature = "afl_internals")]
fn init(afl: &'static afl_state, seed: c_uint) -> Self
where
Self: Sized;
#[cfg(not(feature = "afl_internals"))]
fn init(seed: c_uint) -> Self
where
Self: Sized;
fn fuzz<'b, 's: 'b>(
&'s mut self,
buffer: &'b mut [u8],
add_buff: Option<&[u8]>,
max_size: usize,
) -> Option<&'b [u8]>;
fn fuzz_count(&mut self, buffer: &[u8]) -> u32 {
1
}
fn queue_new_entry(&mut self, filename_new_queue: &CStr, _filename_orig_queue: Option<&CStr>) {}
fn queue_get(&mut self, filename: &CStr) -> bool {
true
}
fn describe(&mut self, max_description: usize) -> Option<&CStr> {
None
}
fn introspection(&mut self) -> Option<&CStr> {
None
}
/*fn post_process(&self, buffer: &[u8], unsigned char **out_buf)-> usize;
int afl_custom_init_trim(&self, buffer: &[u8]);
size_t afl_custom_trim(&self, unsigned char **out_buf);
int afl_custom_post_trim(&self, unsigned char success);
size_t afl_custom_havoc_mutation(&self, buffer: &[u8], unsigned char **out_buf, size_t max_size);
unsigned char afl_custom_havoc_mutation_probability(&self);*/
}
/// Wrappers for the custom mutator which provide the bridging between the C API and CustomMutator.
/// These wrappers are not intended to be used directly, rather export_mutator will use them to publish the custom mutator C API.
#[doc(hidden)]
pub mod wrappers {
#[cfg(feature = "afl_internals")]
use custom_mutator_sys::afl_state;
use core::slice;
use std::{
any::Any,
convert::TryInto,
ffi::{c_void, CStr},
mem::ManuallyDrop,
os::raw::{c_char, c_uint},
panic::catch_unwind,
process::abort,
ptr::null,
};
use crate::RawCustomMutator;
/// A structure to be used as the data pointer for our custom mutator. This was used as additional storage and is kept for now in case its needed later.
/// Also has some convenience functions for FFI conversions (from and to ptr) and tries to make misuse hard (see [`FFIContext::from`]).
struct FFIContext<M: RawCustomMutator> {
mutator: M,
}
impl<M: RawCustomMutator> FFIContext<M> {
fn from(ptr: *mut c_void) -> ManuallyDrop<Box<Self>> {
assert!(!ptr.is_null());
ManuallyDrop::new(unsafe { Box::from_raw(ptr as *mut Self) })
}
fn into_ptr(self: Box<Self>) -> *const c_void {
Box::into_raw(self) as *const c_void
}
#[cfg(feature = "afl_internals")]
fn new(afl: &'static afl_state, seed: c_uint) -> Box<Self> {
Box::new(Self {
mutator: M::init(afl, seed),
})
}
#[cfg(not(feature = "afl_internals"))]
fn new(seed: c_uint) -> Box<Self> {
Box::new(Self {
mutator: M::init(seed),
})
}
}
/// panic handler called for every panic
fn panic_handler(method: &str, panic_info: Box<dyn Any + Send + 'static>) -> ! {
use std::ops::Deref;
let cause = panic_info
.downcast_ref::<String>()
.map(String::deref)
.unwrap_or_else(|| {
panic_info
.downcast_ref::<&str>()
.copied()
.unwrap_or("<cause unknown>")
});
eprintln!("A panic occurred at {}: {}", method, cause);
abort()
}
/// Internal function used in the macro
#[cfg(not(feature = "afl_internals"))]
pub fn afl_custom_init_<M: RawCustomMutator>(seed: c_uint) -> *const c_void {
match catch_unwind(|| FFIContext::<M>::new(seed).into_ptr()) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_init", err),
}
}
/// Internal function used in the macro
#[cfg(feature = "afl_internals")]
pub fn afl_custom_init_<M: RawCustomMutator>(
afl: Option<&'static afl_state>,
seed: c_uint,
) -> *const c_void {
match catch_unwind(|| {
let afl = afl.expect("mutator func called with NULL afl");
FFIContext::<M>::new(afl, seed).into_ptr()
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_init", err),
}
}
/// Internal function used in the macro
pub unsafe fn afl_custom_fuzz_<M: RawCustomMutator>(
data: *mut c_void,
buf: *mut u8,
buf_size: usize,
out_buf: *mut *const u8,
add_buf: *mut u8,
add_buf_size: usize,
max_size: usize,
) -> usize {
match catch_unwind(|| {
let mut context = FFIContext::<M>::from(data);
if buf.is_null() {
panic!("null buf passed to afl_custom_fuzz")
}
if out_buf.is_null() {
panic!("null out_buf passed to afl_custom_fuzz")
}
let buff_slice = slice::from_raw_parts_mut(buf, buf_size);
let add_buff_slice = if add_buf.is_null() {
None
} else {
Some(slice::from_raw_parts(add_buf, add_buf_size))
};
match context
.mutator
.fuzz(buff_slice, add_buff_slice, max_size.try_into().unwrap())
{
Some(buffer) => {
*out_buf = buffer.as_ptr();
buffer.len().try_into().unwrap()
}
None => {
// return the input buffer with 0-length to let AFL skip this mutation attempt
*out_buf = buf;
0
}
}
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_fuzz", err),
}
}
/// Internal function used in the macro
pub unsafe fn afl_custom_fuzz_count_<M: RawCustomMutator>(
data: *mut c_void,
buf: *const u8,
buf_size: usize,
) -> u32 {
match catch_unwind(|| {
let mut context = FFIContext::<M>::from(data);
if buf.is_null() {
panic!("null buf passed to afl_custom_fuzz")
}
let buf_slice = slice::from_raw_parts(buf, buf_size);
// see https://doc.rust-lang.org/nomicon/borrow-splitting.html
let ctx = &mut **context;
let mutator = &mut ctx.mutator;
mutator.fuzz_count(buf_slice)
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_fuzz_count", err),
}
}
/// Internal function used in the macro
pub fn afl_custom_queue_new_entry_<M: RawCustomMutator>(
data: *mut c_void,
filename_new_queue: *const c_char,
filename_orig_queue: *const c_char,
) {
match catch_unwind(|| {
let mut context = FFIContext::<M>::from(data);
if filename_new_queue.is_null() {
panic!("received null filename_new_queue in afl_custom_queue_new_entry");
}
let filename_new_queue = unsafe { CStr::from_ptr(filename_new_queue) };
let filename_orig_queue = if !filename_orig_queue.is_null() {
Some(unsafe { CStr::from_ptr(filename_orig_queue) })
} else {
None
};
context
.mutator
.queue_new_entry(filename_new_queue, filename_orig_queue);
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_queue_new_entry", err),
}
}
/// Internal function used in the macro
pub unsafe fn afl_custom_deinit_<M: RawCustomMutator>(data: *mut c_void) {
match catch_unwind(|| {
// drop the context
ManuallyDrop::into_inner(FFIContext::<M>::from(data));
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_deinit", err),
}
}
/// Internal function used in the macro
pub fn afl_custom_introspection_<M: RawCustomMutator>(data: *mut c_void) -> *const c_char {
match catch_unwind(|| {
let mut context = FFIContext::<M>::from(data);
if let Some(res) = context.mutator.introspection() {
res.as_ptr()
} else {
null()
}
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_introspection", err),
}
}
/// Internal function used in the macro
pub fn afl_custom_describe_<M: RawCustomMutator>(
data: *mut c_void,
max_description_len: usize,
) -> *const c_char {
match catch_unwind(|| {
let mut context = FFIContext::<M>::from(data);
if let Some(res) = context.mutator.describe(max_description_len) {
res.as_ptr()
} else {
null()
}
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_describe", err),
}
}
/// Internal function used in the macro
pub fn afl_custom_queue_get_<M: RawCustomMutator>(
data: *mut c_void,
filename: *const c_char,
) -> u8 {
match catch_unwind(|| {
let mut context = FFIContext::<M>::from(data);
assert!(!filename.is_null());
context
.mutator
.queue_get(unsafe { CStr::from_ptr(filename) }) as u8
}) {
Ok(ret) => ret,
Err(err) => panic_handler("afl_custom_queue_get", err),
}
}
}
/// exports the given Mutator as a custom mutator as the C interface that AFL++ expects.
/// It is not possible to call this macro multiple times, because it would define the custom mutator symbols multiple times.
/// # Example
/// ```
/// # #[macro_use] extern crate custom_mutator;
/// # #[cfg(feature = "afl_internals")]
/// # use custom_mutator::afl_state;
/// # use custom_mutator::CustomMutator;
/// # use std::os::raw::c_uint;
/// struct MyMutator;
/// impl CustomMutator for MyMutator {
/// /// ...
/// # type Error = ();
/// # #[cfg(feature = "afl_internals")]
/// # fn init(_afl_state: &afl_state, _seed: c_uint) -> Result<Self,()> {unimplemented!()}
/// # #[cfg(not(feature = "afl_internals"))]
/// # fn init(_seed: c_uint) -> Result<Self,()> {unimplemented!()}
/// # fn fuzz<'b,'s:'b>(&'s mut self, _buffer: &'b mut [u8], _add_buff: Option<&[u8]>, _max_size: usize) -> Result<Option<&'b [u8]>,()> {unimplemented!()}
/// }
/// export_mutator!(MyMutator);
/// ```
#[macro_export]
macro_rules! export_mutator {
($mutator_type:ty) => {
#[cfg(feature = "afl_internals")]
#[no_mangle]
pub extern "C" fn afl_custom_init(
afl: ::std::option::Option<&'static $crate::afl_state>,
seed: ::std::os::raw::c_uint,
) -> *const ::std::os::raw::c_void {
$crate::wrappers::afl_custom_init_::<$mutator_type>(afl, seed)
}
#[cfg(not(feature = "afl_internals"))]
#[no_mangle]
pub extern "C" fn afl_custom_init(
_afl: *const ::std::os::raw::c_void,
seed: ::std::os::raw::c_uint,
) -> *const ::std::os::raw::c_void {
$crate::wrappers::afl_custom_init_::<$mutator_type>(seed)
}
#[no_mangle]
pub extern "C" fn afl_custom_fuzz_count(
data: *mut ::std::os::raw::c_void,
buf: *const u8,
buf_size: usize,
) -> u32 {
unsafe {
$crate::wrappers::afl_custom_fuzz_count_::<$mutator_type>(data, buf, buf_size)
}
}
#[no_mangle]
pub extern "C" fn afl_custom_fuzz(
data: *mut ::std::os::raw::c_void,
buf: *mut u8,
buf_size: usize,
out_buf: *mut *const u8,
add_buf: *mut u8,
add_buf_size: usize,
max_size: usize,
) -> usize {
unsafe {
$crate::wrappers::afl_custom_fuzz_::<$mutator_type>(
data,
buf,
buf_size,
out_buf,
add_buf,
add_buf_size,
max_size,
)
}
}
#[no_mangle]
pub extern "C" fn afl_custom_queue_new_entry(
data: *mut ::std::os::raw::c_void,
filename_new_queue: *const ::std::os::raw::c_char,
filename_orig_queue: *const ::std::os::raw::c_char,
) {
$crate::wrappers::afl_custom_queue_new_entry_::<$mutator_type>(
data,
filename_new_queue,
filename_orig_queue,
)
}
#[no_mangle]
pub extern "C" fn afl_custom_queue_get(
data: *mut ::std::os::raw::c_void,
filename: *const ::std::os::raw::c_char,
) -> u8 {
$crate::wrappers::afl_custom_queue_get_::<$mutator_type>(data, filename)
}
#[no_mangle]
pub extern "C" fn afl_custom_introspection(
data: *mut ::std::os::raw::c_void,
) -> *const ::std::os::raw::c_char {
$crate::wrappers::afl_custom_introspection_::<$mutator_type>(data)
}
#[no_mangle]
pub extern "C" fn afl_custom_describe(
data: *mut ::std::os::raw::c_void,
max_description_len: usize,
) -> *const ::std::os::raw::c_char {
$crate::wrappers::afl_custom_describe_::<$mutator_type>(data, max_description_len)
}
#[no_mangle]
pub extern "C" fn afl_custom_deinit(data: *mut ::std::os::raw::c_void) {
unsafe { $crate::wrappers::afl_custom_deinit_::<$mutator_type>(data) }
}
};
}
#[cfg(test)]
/// this sanity test is supposed to just find out whether an empty mutator being exported by the macro compiles
mod sanity_test {
use std::os::raw::c_uint;
#[cfg(feature = "afl_internals")]
use super::afl_state;
use super::{export_mutator, RawCustomMutator};
struct ExampleMutator;
impl RawCustomMutator for ExampleMutator {
#[cfg(feature = "afl_internals")]
fn init(_afl: &afl_state, _seed: c_uint) -> Self {
unimplemented!()
}
#[cfg(not(feature = "afl_internals"))]
fn init(_seed: c_uint) -> Self {
unimplemented!()
}
fn fuzz<'b, 's: 'b>(
&'s mut self,
_buffer: &'b mut [u8],
_add_buff: Option<&[u8]>,
_max_size: usize,
) -> Option<&'b [u8]> {
unimplemented!()
}
}
export_mutator!(ExampleMutator);
}
#[allow(unused_variables)]
/// A custom mutator.
/// [`CustomMutator::handle_error`] will be called in case any method returns an [`Result::Err`].
pub trait CustomMutator {
/// The error type. All methods must return the same error type.
type Error: Debug;
/// The method which handles errors.
/// By default, this method will log the error to stderr if the environment variable "`AFL_CUSTOM_MUTATOR_DEBUG`" is set and non-empty.
/// After logging the error, execution will continue on a best-effort basis.
///
/// This default behaviour can be customized by implementing this method.
fn handle_error(err: Self::Error) {
if std::env::var("AFL_CUSTOM_MUTATOR_DEBUG")
.map(|v| !v.is_empty())
.unwrap_or(false)
{
eprintln!("Error in custom mutator: {:?}", err)
}
}
#[cfg(feature = "afl_internals")]
fn init(afl: &'static afl_state, seed: c_uint) -> Result<Self, Self::Error>
where
Self: Sized;
#[cfg(not(feature = "afl_internals"))]
fn init(seed: c_uint) -> Result<Self, Self::Error>
where
Self: Sized;
fn fuzz_count(&mut self, buffer: &[u8]) -> Result<u32, Self::Error> {
Ok(1)
}
fn fuzz<'b, 's: 'b>(
&'s mut self,
buffer: &'b mut [u8],
add_buff: Option<&[u8]>,
max_size: usize,
) -> Result<Option<&'b [u8]>, Self::Error>;
fn queue_new_entry(
&mut self,
filename_new_queue: &CStr,
filename_orig_queue: Option<&CStr>,
) -> Result<(), Self::Error> {
Ok(())
}
fn queue_get(&mut self, filename: &CStr) -> Result<bool, Self::Error> {
Ok(true)
}
fn describe(&mut self, max_description: usize) -> Result<Option<&CStr>, Self::Error> {
Ok(None)
}
fn introspection(&mut self) -> Result<Option<&CStr>, Self::Error> {
Ok(None)
}
}
impl<M> RawCustomMutator for M
where
M: CustomMutator,
M::Error: Debug,
{
#[cfg(feature = "afl_internals")]
fn init(afl: &'static afl_state, seed: c_uint) -> Self
where
Self: Sized,
{
match Self::init(afl, seed) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
panic!("Error in afl_custom_init")
}
}
}
#[cfg(not(feature = "afl_internals"))]
fn init(seed: c_uint) -> Self
where
Self: Sized,
{
match Self::init(seed) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
panic!("Error in afl_custom_init")
}
}
}
fn fuzz_count(&mut self, buffer: &[u8]) -> u32 {
match self.fuzz_count(buffer) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
0
}
}
}
fn fuzz<'b, 's: 'b>(
&'s mut self,
buffer: &'b mut [u8],
add_buff: Option<&[u8]>,
max_size: usize,
) -> Option<&'b [u8]> {
match self.fuzz(buffer, add_buff, max_size) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
None
}
}
}
fn queue_new_entry(&mut self, filename_new_queue: &CStr, filename_orig_queue: Option<&CStr>) {
match self.queue_new_entry(filename_new_queue, filename_orig_queue) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
}
}
}
fn queue_get(&mut self, filename: &CStr) -> bool {
match self.queue_get(filename) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
false
}
}
}
fn describe(&mut self, max_description: usize) -> Option<&CStr> {
match self.describe(max_description) {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
None
}
}
}
fn introspection(&mut self) -> Option<&CStr> {
match self.introspection() {
Ok(r) => r,
Err(e) => {
Self::handle_error(e);
None
}
}
}
}

13
custom_mutators/rust/example/Cargo.toml Normal file
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@ -0,0 +1,13 @@
[package]
name = "example"
version = "0.1.0"
authors = ["Julius Hohnerlein <julihoh@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
custom_mutator = { path = "../custom_mutator" }
[lib]
crate-type = ["cdylib"]

50
custom_mutators/rust/example/src/lib.rs Normal file
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@ -0,0 +1,50 @@
#![allow(unused_variables)]
use custom_mutator::{export_mutator, CustomMutator};
use std::os::raw::c_uint;
struct ExampleMutator;
impl CustomMutator for ExampleMutator {
type Error = ();
fn init(seed: c_uint) -> Result<Self, ()> {
Ok(Self)
}
fn fuzz<'b, 's: 'b>(
&'s mut self,
buffer: &'b mut [u8],
add_buff: Option<&[u8]>,
max_size: usize,
) -> Result<Option<&'b [u8]>, ()> {
buffer.reverse();
Ok(Some(buffer))
}
}
struct OwnBufferExampleMutator {
own_buffer: Vec<u8>,
}
impl CustomMutator for OwnBufferExampleMutator {
type Error = ();
fn init(seed: c_uint) -> Result<Self, ()> {
Ok(Self {
own_buffer: Vec::new(),
})
}
fn fuzz<'b, 's: 'b>(
&'s mut self,
buffer: &'b mut [u8],
add_buff: Option<&[u8]>,
max_size: usize,
) -> Result<Option<&'b [u8]>, ()> {
self.own_buffer.reverse();
Ok(Some(self.own_buffer.as_slice()))
}
}
export_mutator!(ExampleMutator);

14
custom_mutators/rust/example_lain/Cargo.toml Normal file
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@ -0,0 +1,14 @@
[package]
name = "example_lain"
version = "0.1.0"
authors = ["Julius Hohnerlein <julihoh@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
custom_mutator = { path = "../custom_mutator" }
lain="0.5"
[lib]
crate-type = ["cdylib"]

1
custom_mutators/rust/example_lain/rust-toolchain Normal file
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@ -0,0 +1 @@
nightly

60
custom_mutators/rust/example_lain/src/lib.rs Normal file
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@ -0,0 +1,60 @@
use custom_mutator::{export_mutator, CustomMutator};
use lain::{
mutator::Mutator,
prelude::*,
rand::{rngs::StdRng, SeedableRng},
};
use std::os::raw::c_uint;
#[derive(Debug, Mutatable, NewFuzzed, BinarySerialize)]
struct MyStruct {
field_1: u8,
#[lain(bits = 3)]
field_2: u8,
#[lain(bits = 5)]
field_3: u8,
#[lain(min = 5, max = 10000)]
field_4: u32,
#[lain(ignore)]
ignored_field: u64,
}
struct LainMutator {
mutator: Mutator<StdRng>,
buffer: Vec<u8>,
}
impl CustomMutator for LainMutator {
type Error = ();
fn init(seed: c_uint) -> Result<Self, ()> {
Ok(Self {
mutator: Mutator::new(StdRng::seed_from_u64(seed as u64)),
buffer: Vec::new(),
})
}
fn fuzz<'b, 's: 'b>(
&'s mut self,
_buffer: &'b mut [u8],
_add_buff: Option<&[u8]>,
max_size: usize,
) -> Result<Option<&'b [u8]>, ()> {
// we just sample an instance of MyStruct, ignoring the current input
let instance = MyStruct::new_fuzzed(&mut self.mutator, None);
let size = instance.serialized_size();
if size > max_size {
return Err(());
}
self.buffer.clear();
self.buffer.reserve(size);
instance.binary_serialize::<_, BigEndian>(&mut self.buffer);
Ok(Some(self.buffer.as_slice()))
}
}
export_mutator!(LainMutator);

5
docs/custom_mutators.md
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@ -4,6 +4,11 @@ This file describes how you can implement custom mutations to be used in AFL.
For now, we support C/C++ library and Python module, collectivelly named as the For now, we support C/C++ library and Python module, collectivelly named as the
custom mutator. custom mutator.
There is also experimental support for Rust in `custom_mutators/rust`.
Please refer to that directory for documentation.
Run ```cargo doc -p custom_mutator --open``` in that directory to view the
documentation in your web browser.
Implemented by Implemented by
- C/C++ library (`*.so`): Khaled Yakdan from Code Intelligence (<yakdan@code-intelligence.de>) - C/C++ library (`*.so`): Khaled Yakdan from Code Intelligence (<yakdan@code-intelligence.de>)
- Python module: Christian Holler from Mozilla (<choller@mozilla.com>) - Python module: Christian Holler from Mozilla (<choller@mozilla.com>)