Add embed-runtime feature (#1489)

* Add library embedding feature to libafl_libfuzzer

* Add comment describing embed-runtime feature and CI test

Author: novafacing

.github/workflows/build_and_test.yml

@@ -105,6 +105,10 @@ jobs:
     - name: Run miri tests
       run: RUST_BACKTRACE=1 MIRIFLAGS="-Zmiri-disable-isolation" cargo +nightly miri test
 
+    # --- test embedding the libafl_libfuzzer_runtime library
+    - name: Test Build libafl_libfuzzer with embed
+      run: cargo +nightly test --features=embed-runtime --manifest-path libafl_libfuzzer/Cargo.toml
+
   ubuntu-check:
     runs-on: ubuntu-22.04
     steps:

libafl_libfuzzer/Cargo.toml

@@ -14,7 +14,7 @@ include = [
   "/Cargo.toml",
   "/build.rs",
   "/libafl_libfuzzer_runtime",
-  "!/libafl_libfuzzer_runtime/target"
+  "!/libafl_libfuzzer_runtime/target",
 ]
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
@@ -30,6 +30,10 @@ rustversion = "1.0"
 arbitrary-derive = ["libfuzzer-sys/arbitrary-derive"]
 ## Enables fuzzer introspection with LibAFL's `introspection` feature
 introspection = []
+## Embeds the built libafl_libfuzzer_runtime library into the crate with include_bytes! for use
+## in downstream cases like libafl_cc linking the runtime with:
+## `-fsanitize=fuzzer-no-link -l:libafl_libfuzzer_runtime.a`
+embed-runtime = []
 
 [dependencies]
 libfuzzer-sys = { version = "0.4.7", default-features = false }
@@ -39,6 +43,4 @@ document-features = { version = "0.2" }
 features = ["document-features"]
 all-features = true
 
-rustdoc-args = [
-    "--cfg", "docsrs",
-]
+rustdoc-args = ["--cfg", "docsrs"]

libafl_libfuzzer/build.rs

@@ -70,6 +70,16 @@ fn main() {
     let mut lib_path = custom_lib_dir.join(std::env::var_os("TARGET").unwrap());
     lib_path.push("release");
 
+    #[cfg(all(feature = "embed-runtime", target_family = "unix"))]
+    {
+        // NOTE: lib, .a are added always on unix-like systems as described in:
+        // https://gist.github.com/novafacing/1389cbb2f0a362d7eb103e67b4468e2b
+        println!(
+            "cargo:rustc-env=LIBAFL_LIBFUZZER_RUNTIME_PATH={}",
+            lib_path.join("libafl_libfuzzer_runtime.a").display()
+        );
+    }
+
     println!(
         "cargo:rustc-link-search=native={}",
         lib_path.to_str().unwrap()

libafl_libfuzzer/src/lib.rs

@@ -90,3 +90,28 @@ extern "C" {
         harness_fn: Option<extern "C" fn(*const u8, usize) -> c_int>,
     ) -> c_int;
 }
+
+#[cfg(all(
+    feature = "embed-runtime",
+    target_family = "unix",
+    // Disable when building with clippy, as it will complain about the missing environment
+    // variable which is set by the build script, which is not run under clippy.
+    not(feature = "cargo-clippy")
+))]
+pub const LIBAFL_LIBFUZZER_RUNTIME_LIBRARY: &'static [u8] =
+    include_bytes!(env!("LIBAFL_LIBFUZZER_RUNTIME_PATH"));
+
+#[cfg(test)]
+mod tests {
+    #[cfg(all(feature = "embed-runtime", not(feature = "cargo-clippy")))]
+    #[test]
+    fn test_embed_runtime_sized() {
+        use crate::LIBAFL_LIBFUZZER_RUNTIME_LIBRARY;
+
+        assert_ne!(
+            LIBAFL_LIBFUZZER_RUNTIME_LIBRARY.len(),
+            0,
+            "Runtime library empty"
+        );
+    }
+}