Libafl-fuzz: fix unicorn mode (#2502)

* libafl-fuzz: fix unicorn mode not using a deferred forkserver
libafl-fuzz: simplify handling args for harness

* fix unicorn_mode

---------

Co-authored-by: Dominik Maier <domenukk@gmail.com>

fuzzers/others/libafl-fuzz/Makefile.toml

@@ -13,7 +13,7 @@ LLVM_CONFIG = { value = "llvm-config-18", condition = { env_not_set = [
   "LLVM_CONFIG",
 ] } }
 AFL_VERSION = "598a3c6b5e24bd33e84b914e145810d39f88adf6"
-AFL_DIR = { value = "./AFLplusplus" }
+AFL_DIR = { value = "${PROJECT_DIR}/AFLplusplus" }
 AFL_CC_PATH = { value = "${AFL_DIR}/afl-clang-fast" }
 CC = { value = "clang" }
 
@@ -204,12 +204,15 @@ script = '''
 export AFL_PATH=${AFL_DIR}
 export AFL_CORES=1
 export AFL_STATS_INTERVAL=1
+
 # TODO: test unicorn persistent mode once it's fixed on AFL++
+
 LIBAFL_DEBUG_OUTPUT=1 AFL_DEBUG=1 AFL_DEBUG_CHILD=1 timeout 15s ${FUZZER} -m 0 -U -i ./test/seeds_unicorn -o ./test/output-unicorn-python -- python3 ${AFL_DIR}/unicorn_mode/samples/python_simple/simple_test_harness.py @@ || true
 test -n "$( ls ./test/output-unicorn-python/fuzzer_main/queue/id:000003* 2>/dev/null )" || {
 	echo "No new corpus entries found for Unicorn python3 mode"
 	exit 1
 }
+
 export AFL_COMPCOV_LEVEL=2
 LIBAFL_DEBUG_OUTPUT=1 AFL_DEBUG=1 AFL_DEBUG_CHILD=1 timeout 15s ${FUZZER} -m 0 -U -i ./test/seeds_unicorn_cmpcov -o ./test/output-unicorn-cmpcov -- python3 ${AFL_DIR}/unicorn_mode/samples/compcov_x64/compcov_test_harness.py @@ || true
 test -n "$( ls ./test/output-unicorn-cmpcov/fuzzer_main/queue/id:000002* 2>/dev/null )" || {

fuzzers/others/libafl-fuzz/src/executor.rs

@@ -52,7 +52,8 @@ pub fn check_binary(opt: &mut Opt, shmem_env_var: &str) -> Result<(), Error> {
         }
     }
     let metadata = bin_path.metadata()?;
-    let is_reg = !bin_path.is_symlink() && !bin_path.is_dir();
+    // AFL++ does not follow symlinks, BUT we do.
+    let is_reg = bin_path.is_file();
     let bin_size = metadata.st_size();
     let is_executable = metadata.permissions().mode() & 0o111 != 0;
     if !is_reg || !is_executable || bin_size < 4 {

fuzzers/others/libafl-fuzz/src/fuzzer.rs

@@ -1,4 +1,4 @@
-use std::{borrow::Cow, env, marker::PhantomData, path::PathBuf, time::Duration};
+use std::{borrow::Cow, marker::PhantomData, path::PathBuf, time::Duration};
 
 use libafl::{
     corpus::{CachedOnDiskCorpus, Corpus, OnDiskCorpus},
@@ -410,22 +410,11 @@ fn base_executor<'a>(
     if let Some(kill_signal) = opt.kill_signal {
         executor = executor.kill_signal(kill_signal);
     }
-    if opt.is_persistent || opt.qemu_mode {
+    if opt.is_persistent || opt.qemu_mode || opt.unicorn_mode {
         executor = executor.shmem_provider(shmem_provider);
     }
     // Set arguments for the target if necessary
-    let exec = opt.executable.display().to_string();
+    for arg in &opt.target_args {
-    // we skip all libafl-fuzz arguments.
-    let (mut skip, _) = env::args()
-        .enumerate()
-        .find(|i| i.1 == exec)
-        .expect("invariant; should never occur");
-    // we need the binary to remain as an argument if we are in qemu_mode
-    if !opt.qemu_mode {
-        skip += 1;
-    }
-    let args = env::args().skip(skip);
-    for arg in args {
         if arg == AFL_HARNESS_FILE_INPUT {
             let mut file = get_unique_std_input_file();
             if let Some(ext) = &opt.input_ext {
@@ -441,6 +430,8 @@ fn base_executor<'a>(
         }
     }
     if opt.qemu_mode {
+        // We need to give the harness as the first argument to afl-qemu-trace.
+        executor = executor.arg(opt.executable.clone());
         executor = executor.program(
             find_afl_binary("afl-qemu-trace", Some(opt.executable.clone()))
                 .expect("to find afl-qemu-trace"),

fuzzers/others/libafl-fuzz/src/main.rs

@@ -111,6 +111,7 @@ fn main() {
 /// The Configuration
 struct Opt {
     executable: PathBuf,
+    target_args: Vec<String>,
 
     // NOTE: afl-fuzz does not accept multiple input directories
     #[arg(short = 'i')]

fuzzers/others/libafl-fuzz/test/seeds_unicorn/in

@@ -0,0 +1 @@
+0

fuzzers/others/libafl-fuzz/test/seeds_unicorn_cmpcov/in

@@ -0,0 +1 @@
+