custom mutator rust support (#752)

* 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

4 files changed, 63 insertions, 0 deletions

diff --git a/custom_mutators/rust/custom_mutator-sys/Cargo.toml b/custom_mutators/rust/custom_mutator-sys/Cargo.toml
new file mode 100644
index 00000000..104f7df0
--- /dev/null
+++ b/custom_mutators/rust/custom_mutator-sys/Cargo.toml
@@ -0,0 +1,12 @@
+[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"
diff --git a/custom_mutators/rust/custom_mutator-sys/build.rs b/custom_mutators/rust/custom_mutator-sys/build.rs
new file mode 100644
index 00000000..3c88a90d
--- /dev/null
+++ b/custom_mutators/rust/custom_mutator-sys/build.rs
@@ -0,0 +1,42 @@
+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!");
+}
diff --git a/custom_mutators/rust/custom_mutator-sys/src/lib.rs b/custom_mutators/rust/custom_mutator-sys/src/lib.rs
new file mode 100644
index 00000000..a38a13a8
--- /dev/null
+++ b/custom_mutators/rust/custom_mutator-sys/src/lib.rs
@@ -0,0 +1,5 @@
+#![allow(non_upper_case_globals)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+
+include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
diff --git a/custom_mutators/rust/custom_mutator-sys/wrapper.h b/custom_mutators/rust/custom_mutator-sys/wrapper.h
new file mode 100644
index 00000000..81cdb90f
--- /dev/null
+++ b/custom_mutators/rust/custom_mutator-sys/wrapper.h
@@ -0,0 +1,4 @@
+#include "../../../include/afl-fuzz.h"
+#include "../../../include/common.h"
+#include "../../../include/config.h"
+#include "../../../include/debug.h"