Improve the libafl_libfuzzer corpus (#1539)

* improved libfuzzer corpus

* use .into() for converting ids to usize

* oops

* fix warning about unused arg

* fix some lingering CI errors

* actually save the last lmao

libafl/src/corpus/inmemory.rs

@@ -183,7 +183,7 @@ where
     /// Get the next id given a `CorpusId` (creation order)
     #[cfg(not(feature = "corpus_btreemap"))]
     #[must_use]
-    fn next(&self, idx: CorpusId) -> Option<CorpusId> {
+    pub fn next(&self, idx: CorpusId) -> Option<CorpusId> {
         if let Some(item) = self.map.get(&idx) {
             item.next
         } else {
@@ -194,7 +194,7 @@ where
     /// Get the next id given a `CorpusId` (creation order)
     #[cfg(feature = "corpus_btreemap")]
     #[must_use]
-    fn next(&self, idx: CorpusId) -> Option<CorpusId> {
+    pub fn next(&self, idx: CorpusId) -> Option<CorpusId> {
         // TODO see if using self.keys is faster
         let mut range = self
             .map
@@ -214,7 +214,7 @@ where
     /// Get the previous id given a `CorpusId` (creation order)
     #[cfg(not(feature = "corpus_btreemap"))]
     #[must_use]
-    fn prev(&self, idx: CorpusId) -> Option<CorpusId> {
+    pub fn prev(&self, idx: CorpusId) -> Option<CorpusId> {
         if let Some(item) = self.map.get(&idx) {
             item.prev
         } else {
@@ -225,7 +225,7 @@ where
     /// Get the previous id given a `CorpusId` (creation order)
     #[cfg(feature = "corpus_btreemap")]
     #[must_use]
-    fn prev(&self, idx: CorpusId) -> Option<CorpusId> {
+    pub fn prev(&self, idx: CorpusId) -> Option<CorpusId> {
         // TODO see if using self.keys is faster
         let mut range = self
             .map
@@ -245,28 +245,28 @@ where
     /// Get the first created id
     #[cfg(not(feature = "corpus_btreemap"))]
     #[must_use]
-    fn first(&self) -> Option<CorpusId> {
+    pub fn first(&self) -> Option<CorpusId> {
         self.first_idx
     }
 
     /// Get the first created id
     #[cfg(feature = "corpus_btreemap")]
     #[must_use]
-    fn first(&self) -> Option<CorpusId> {
+    pub fn first(&self) -> Option<CorpusId> {
         self.map.iter().next().map(|x| *x.0)
     }
 
     /// Get the last created id
     #[cfg(not(feature = "corpus_btreemap"))]
     #[must_use]
-    fn last(&self) -> Option<CorpusId> {
+    pub fn last(&self) -> Option<CorpusId> {
         self.last_idx
     }
 
     /// Get the last created id
     #[cfg(feature = "corpus_btreemap")]
     #[must_use]
-    fn last(&self) -> Option<CorpusId> {
+    pub fn last(&self) -> Option<CorpusId> {
         self.map.iter().next_back().map(|x| *x.0)
     }
 

libafl/src/monitors/mod.rs

@@ -21,7 +21,7 @@ use core::{fmt, fmt::Write, time::Duration};
 #[cfg(feature = "std")]
 pub use disk::{OnDiskJSONMonitor, OnDiskTOMLMonitor};
 use hashbrown::HashMap;
-use libafl_bolts::{current_time, format_duration_hms, ClientId};
+use libafl_bolts::{current_time, format_duration_hms, ClientId, Error};
 use serde::{Deserialize, Serialize};
 
 #[cfg(feature = "afl_exec_sec")]
@@ -210,6 +210,7 @@ impl ClientStats {
 
     /// Update the user-defined stat with name and value
     pub fn update_user_stats(&mut self, name: String, value: UserStats) {
+        log::info!("{}", Error::unknown("dumping backtrace for monitoring"));
         self.user_monitor.insert(name, value);
     }
 

libafl_bolts/src/lib.rs

@@ -140,7 +140,6 @@ use alloc::vec::Vec;
 use core::hash::BuildHasher;
 #[cfg(any(feature = "xxh3", feature = "alloc"))]
 use core::hash::Hasher;
-use core::{iter::Iterator, time};
 #[cfg(feature = "std")]
 use std::time::{SystemTime, UNIX_EPOCH};
 
@@ -175,18 +174,23 @@ pub mod launcher {}
 #[allow(unused_imports)]
 #[macro_use]
 extern crate libafl_derive;
-#[cfg(feature = "alloc")]
-use alloc::string::{FromUtf8Error, String};
 use core::{
     array::TryFromSliceError,
     fmt::{self, Display},
+    iter::Iterator,
     num::{ParseIntError, TryFromIntError},
+    time,
 };
 #[cfg(feature = "std")]
 use std::{env::VarError, io};
 
 #[cfg(feature = "libafl_derive")]
 pub use libafl_derive::SerdeAny;
+#[cfg(feature = "alloc")]
+use {
+    alloc::string::{FromUtf8Error, String},
+    core::cell::{BorrowError, BorrowMutError},
+};
 
 /// We need fixed names for many parts of this lib.
 pub trait Named {
@@ -444,6 +448,24 @@ impl Display for Error {
     }
 }
 
+#[cfg(feature = "alloc")]
+impl From<BorrowError> for Error {
+    fn from(err: BorrowError) -> Self {
+        Self::illegal_state(format!(
+            "Couldn't borrow from a RefCell as immutable: {err:?}"
+        ))
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl From<BorrowMutError> for Error {
+    fn from(err: BorrowMutError) -> Self {
+        Self::illegal_state(format!(
+            "Couldn't borrow from a RefCell as mutable: {err:?}"
+        ))
+    }
+}
+
 /// Stringify the postcard serializer error
 #[cfg(feature = "alloc")]
 impl From<postcard::Error> for Error {

libafl_libfuzzer/libafl_libfuzzer_runtime/Cargo.toml

@@ -40,7 +40,7 @@ log = "0.4.17"
 mimalloc = { version = "0.1.34", default-features = false, optional = true }
 num-traits = "0.2.15"
 rand = "0.8.5"
-serde = { version = "1.0", default-features = false, features = ["alloc", "derive"] } # serialization lib
+serde = { version = "1.0", features = ["derive"] } # serialization lib
 
 # clippy-suggested optimised byte counter
 bytecount = "0.6.3"

libafl_libfuzzer/libafl_libfuzzer_runtime/src/corpus.rs

@@ -0,0 +1,322 @@
+use std::{
+    cell::RefCell,
+    collections::{hash_map::Entry, BTreeMap, HashMap},
+    io::ErrorKind,
+    path::PathBuf,
+    sync::atomic::{AtomicU64, Ordering},
+};
+
+use libafl::{
+    corpus::{inmemory::TestcaseStorage, Corpus, CorpusId, Testcase},
+    inputs::{Input, UsesInput},
+};
+use libafl_bolts::Error;
+use serde::{Deserialize, Serialize};
+
+/// A corpus which attempts to mimic the behaviour of libFuzzer.
+#[derive(Deserialize, Serialize, Debug)]
+#[serde(bound = "I: serde::de::DeserializeOwned")]
+pub struct LibfuzzerCorpus<I>
+where
+    I: Input + Serialize,
+{
+    corpus_dir: PathBuf,
+    loaded_mapping: RefCell<HashMap<CorpusId, u64>>,
+    loaded_entries: RefCell<BTreeMap<u64, CorpusId>>,
+    mapping: TestcaseStorage<I>,
+    max_len: usize,
+
+    current: Option<CorpusId>,
+    next_recency: AtomicU64,
+}
+
+impl<I> LibfuzzerCorpus<I>
+where
+    I: Input + Serialize + for<'de> Deserialize<'de>,
+{
+    pub fn new(corpus_dir: PathBuf, max_len: usize) -> Self {
+        Self {
+            corpus_dir,
+            loaded_mapping: RefCell::new(HashMap::default()),
+            loaded_entries: RefCell::new(BTreeMap::default()),
+            mapping: TestcaseStorage::new(),
+            max_len,
+            current: None,
+            next_recency: AtomicU64::new(0),
+        }
+    }
+
+    pub fn dir_path(&self) -> &PathBuf {
+        &self.corpus_dir
+    }
+
+    /// Touch this index and maybe evict an entry if we have touched an input which was unloaded.
+    fn touch(&self, idx: CorpusId) -> Result<(), Error> {
+        let mut loaded_mapping = self.loaded_mapping.borrow_mut();
+        let mut loaded_entries = self.loaded_entries.borrow_mut();
+        match loaded_mapping.entry(idx) {
+            Entry::Occupied(mut e) => {
+                let &old = e.get();
+                let new = self.next_recency.fetch_add(1, Ordering::Relaxed);
+                e.insert(new);
+                loaded_entries.remove(&old);
+                loaded_entries.insert(new, idx);
+            }
+            Entry::Vacant(e) => {
+                // new entry! send it in
+                let new = self.next_recency.fetch_add(1, Ordering::Relaxed);
+                e.insert(new);
+                loaded_entries.insert(new, idx);
+            }
+        }
+        if loaded_entries.len() > self.max_len {
+            let idx = loaded_entries.pop_first().unwrap().1; // cannot panic
+            let cell = self.mapping.get(idx).ok_or_else(|| {
+                Error::key_not_found(format!("Tried to evict non-existent entry {idx}"))
+            })?;
+            let mut tc = cell.try_borrow_mut()?;
+            let _ = tc.input_mut().take();
+        }
+        Ok(())
+    }
+}
+
+impl<I> UsesInput for LibfuzzerCorpus<I>
+where
+    I: Input + Serialize + for<'de> Deserialize<'de>,
+{
+    type Input = I;
+}
+
+impl<I> Corpus for LibfuzzerCorpus<I>
+where
+    I: Input + Serialize + for<'de> Deserialize<'de>,
+{
+    fn count(&self) -> usize {
+        self.mapping.map.len()
+    }
+
+    fn add(&mut self, testcase: Testcase<Self::Input>) -> Result<CorpusId, Error> {
+        let idx = self.mapping.insert(RefCell::new(testcase));
+        let mut testcase = self.mapping.get(idx).unwrap().borrow_mut();
+
+        match testcase.file_path() {
+            Some(path) if path.canonicalize()?.starts_with(&self.corpus_dir) => {
+                // if it's already in the correct dir, we retain it
+            }
+            _ => {
+                let input = testcase.input().as_ref().ok_or_else(|| {
+                    Error::empty(
+                        "The testcase, when added to the corpus, must have an input present!",
+                    )
+                })?;
+                let name = input.generate_name(idx.into());
+                let path = self.corpus_dir.join(&name);
+
+                match input.to_file(&path) {
+                    Err(Error::File(e, _)) if e.kind() == ErrorKind::AlreadyExists => {
+                        // we do not care if the file already exists; in this case, we assume it is equal
+                    }
+                    res => res?,
+                }
+
+                // we DO NOT save metadata!
+
+                testcase.filename_mut().replace(name);
+                testcase.file_path_mut().replace(path);
+            }
+        };
+
+        self.touch(idx)?;
+        Ok(idx)
+    }
+
+    fn replace(
+        &mut self,
+        _idx: CorpusId,
+        _testcase: Testcase<Self::Input>,
+    ) -> Result<Testcase<Self::Input>, Error> {
+        unimplemented!("It is unsafe to use this corpus variant with replace!");
+    }
+
+    fn remove(&mut self, _id: CorpusId) -> Result<Testcase<Self::Input>, Error> {
+        unimplemented!("It is unsafe to use this corpus variant with replace!");
+    }
+
+    fn get(&self, id: CorpusId) -> Result<&RefCell<Testcase<Self::Input>>, Error> {
+        self.touch(id)?;
+        self.mapping.map.get(&id).map(|item| &item.testcase).ok_or_else(|| Error::illegal_state("Nonexistent corpus entry {id} requested (present in loaded entries, but not the mapping?)"))
+    }
+
+    fn current(&self) -> &Option<CorpusId> {
+        &self.current
+    }
+
+    fn current_mut(&mut self) -> &mut Option<CorpusId> {
+        &mut self.current
+    }
+
+    fn next(&self, id: CorpusId) -> Option<CorpusId> {
+        self.mapping.next(id)
+    }
+
+    fn prev(&self, id: CorpusId) -> Option<CorpusId> {
+        self.mapping.prev(id)
+    }
+
+    fn first(&self) -> Option<CorpusId> {
+        self.mapping.first()
+    }
+
+    fn last(&self) -> Option<CorpusId> {
+        self.mapping.last()
+    }
+
+    fn load_input_into(&self, testcase: &mut Testcase<Self::Input>) -> Result<(), Error> {
+        // we don't need to update the loaded testcases because it must have already been loaded
+        if testcase.input().is_none() {
+            let path = testcase.file_path().as_ref().ok_or_else(|| {
+                Error::empty("The testcase, when being saved, must have a file path!")
+            })?;
+            let input = I::from_file(path)?;
+            testcase.input_mut().replace(input);
+        }
+        Ok(())
+    }
+
+    fn store_input_from(&self, testcase: &Testcase<Self::Input>) -> Result<(), Error> {
+        let input = testcase.input().as_ref().ok_or_else(|| {
+            Error::empty("The testcase, when being saved, must have an input present!")
+        })?;
+        let path = testcase.file_path().as_ref().ok_or_else(|| {
+            Error::empty("The testcase, when being saved, must have a file path!")
+        })?;
+        match input.to_file(path) {
+            Err(Error::File(e, _)) if e.kind() == ErrorKind::AlreadyExists => {
+                // we do not care if the file already exists; in this case, we assume it is equal
+                Ok(())
+            }
+            res => res,
+        }
+    }
+}
+
+/// A corpus which attempts to mimic the behaviour of libFuzzer's crash output.
+#[derive(Deserialize, Serialize, Debug)]
+#[serde(bound = "I: serde::de::DeserializeOwned")]
+pub struct ArtifactCorpus<I>
+where
+    I: Input + Serialize,
+{
+    last: Option<RefCell<Testcase<I>>>,
+    count: usize,
+}
+
+impl<I> ArtifactCorpus<I>
+where
+    I: Input + Serialize + for<'de> Deserialize<'de>,
+{
+    pub fn new() -> Self {
+        Self {
+            last: None,
+            count: 0,
+        }
+    }
+}
+
+impl<I> UsesInput for ArtifactCorpus<I>
+where
+    I: Input + Serialize + for<'de> Deserialize<'de>,
+{
+    type Input = I;
+}
+
+impl<I> Corpus for ArtifactCorpus<I>
+where
+    I: Input + Serialize + for<'de> Deserialize<'de>,
+{
+    fn count(&self) -> usize {
+        self.count
+    }
+
+    fn add(&mut self, testcase: Testcase<Self::Input>) -> Result<CorpusId, Error> {
+        let idx = self.count;
+        self.count += 1;
+
+        let input = testcase.input().as_ref().ok_or_else(|| {
+            Error::empty("The testcase, when added to the corpus, must have an input present!")
+        })?;
+        let path = testcase.file_path().as_ref().ok_or_else(|| {
+            Error::illegal_state("Should have set the path in the LibfuzzerCrashCauseFeedback.")
+        })?;
+        match input.to_file(path) {
+            Err(Error::File(e, _)) if e.kind() == ErrorKind::AlreadyExists => {
+                // we do not care if the file already exists; in this case, we assume it is equal
+            }
+            res => res?,
+        }
+
+        // we DO NOT save metadata!
+        self.last = Some(RefCell::new(testcase));
+
+        Ok(CorpusId::from(idx))
+    }
+
+    fn replace(
+        &mut self,
+        _idx: CorpusId,
+        _testcase: Testcase<Self::Input>,
+    ) -> Result<Testcase<Self::Input>, Error> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn remove(&mut self, _id: CorpusId) -> Result<Testcase<Self::Input>, Error> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn get(&self, id: CorpusId) -> Result<&RefCell<Testcase<Self::Input>>, Error> {
+        let maybe_last = if self
+            .count
+            .checked_sub(1)
+            .map(CorpusId::from)
+            .map_or(false, |last| last == id)
+        {
+            self.last.as_ref()
+        } else {
+            None
+        };
+        maybe_last.ok_or_else(|| Error::illegal_argument("Can only get the last corpus ID."))
+    }
+
+    fn current(&self) -> &Option<CorpusId> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn current_mut(&mut self) -> &mut Option<CorpusId> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn next(&self, _id: CorpusId) -> Option<CorpusId> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn prev(&self, _id: CorpusId) -> Option<CorpusId> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn first(&self) -> Option<CorpusId> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn last(&self) -> Option<CorpusId> {
+        self.count.checked_sub(1).map(CorpusId::from)
+    }
+
+    fn load_input_into(&self, _testcase: &mut Testcase<Self::Input>) -> Result<(), Error> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+
+    fn store_input_from(&self, _testcase: &Testcase<Self::Input>) -> Result<(), Error> {
+        unimplemented!("Artifact prefix is thin and cannot get, replace, or remove.")
+    }
+}

libafl_libfuzzer/libafl_libfuzzer_runtime/src/feedbacks.rs

@@ -1,6 +1,5 @@
 use alloc::rc::Rc;
 use core::{cell::RefCell, fmt::Debug};
-use std::path::PathBuf;
 
 use libafl::{
     alloc,
@@ -77,12 +76,12 @@ impl LibfuzzerCrashCauseMetadata {
 
 #[derive(Debug)]
 pub struct LibfuzzerCrashCauseFeedback {
-    artifact_prefix: Option<ArtifactPrefix>,
+    artifact_prefix: ArtifactPrefix,
     exit_kind: ExitKind,
 }
 
 impl LibfuzzerCrashCauseFeedback {
-    pub fn new(artifact_prefix: Option<ArtifactPrefix>) -> Self {
+    pub fn new(artifact_prefix: ArtifactPrefix) -> Self {
         Self {
             artifact_prefix,
             exit_kind: ExitKind::Ok,
@@ -104,17 +103,10 @@ impl LibfuzzerCrashCauseFeedback {
             let name = testcase.input().as_ref().unwrap().generate_name(0);
             name
         };
-        let file_path = if let Some(artifact_prefix) = self.artifact_prefix.as_ref() {
+        let file_path = self.artifact_prefix.dir().join(format!(
-            if let Some(filename_prefix) = artifact_prefix.filename_prefix() {
+            "{}{prefix}-{base}",
-                artifact_prefix
+            self.artifact_prefix.filename_prefix()
-                    .dir()
+        ));
-                    .join(format!("{filename_prefix}{prefix}-{base}"))
-            } else {
-                artifact_prefix.dir().join(format!("{prefix}-{base}"))
-            }
-        } else {
-            PathBuf::from(format!("{prefix}-{base}"))
-        };
         *testcase.file_path_mut() = Some(file_path);
     }
 }

libafl_libfuzzer/libafl_libfuzzer_runtime/src/lib.rs

@@ -79,9 +79,11 @@ use libafl::{
     Error,
 };
 use libafl_bolts::AsSlice;
+use libc::_exit;
 
 use crate::options::{LibfuzzerMode, LibfuzzerOptions};
 
+mod corpus;
 mod feedbacks;
 mod fuzz;
 mod merge;
@@ -152,7 +154,7 @@ macro_rules! fuzz_with {
                 AsSlice,
         };
         use libafl::{
-            corpus::{CachedOnDiskCorpus, Corpus, OnDiskCorpus},
+            corpus::Corpus,
             executors::{ExitKind, InProcessExecutor, TimeoutExecutor},
             feedback_and_fast, feedback_not, feedback_or, feedback_or_fast,
             feedbacks::{ConstFeedback, CrashFeedback, MaxMapFeedback, NewHashFeedback, TimeFeedback, TimeoutFeedback},
@@ -179,6 +181,7 @@ macro_rules! fuzz_with {
         use std::{env::temp_dir, fs::create_dir, path::PathBuf};
 
         use crate::{BACKTRACE, CustomMutationStatus};
+        use crate::corpus::{ArtifactCorpus, LibfuzzerCorpus};
         use crate::feedbacks::{LibfuzzerCrashCauseFeedback, LibfuzzerKeepFeedback, ShrinkMapFeedback};
         use crate::misc::should_use_grimoire;
         use crate::observers::{MappedEdgeMapObserver, SizeValueObserver};
@@ -243,7 +246,7 @@ macro_rules! fuzz_with {
 
             // A feedback to choose if an input is a solution or not
             let mut objective = feedback_or_fast!(
-                LibfuzzerCrashCauseFeedback::new($options.artifact_prefix().cloned()),
+                LibfuzzerCrashCauseFeedback::new($options.artifact_prefix().clone()),
                 OomFeedback,
                 feedback_and_fast!(
                     CrashFeedback::new(),
@@ -269,13 +272,7 @@ macro_rules! fuzz_with {
                 dir
             };
 
-            let crash_corpus = if let Some(prefix) = $options.artifact_prefix() {
+            let crash_corpus = ArtifactCorpus::new();
-                OnDiskCorpus::with_meta_format_and_prefix(prefix.dir(), None, prefix.filename_prefix().clone(), false)
-                    .unwrap()
-            } else {
-                OnDiskCorpus::with_meta_format_and_prefix(&std::env::current_dir().unwrap(), None, None, false)
-                    .unwrap()
-            };
 
             // If not restarting, create a State from scratch
             let mut state = state.unwrap_or_else(|| {
@@ -283,7 +280,7 @@ macro_rules! fuzz_with {
                     // RNG
                     StdRand::with_seed(current_nanos()),
                     // Corpus that will be evolved, we keep it in memory for performance
-                    CachedOnDiskCorpus::with_meta_format_and_prefix(corpus_dir.clone(), 4096, None, None, true).unwrap(),
+                    LibfuzzerCorpus::new(corpus_dir.clone(), 4096),
                     // Corpus in which we store solutions (crashes in this example),
                     // on disk so the user can get them after stopping the fuzzer
                     crash_corpus,
@@ -591,7 +588,21 @@ pub unsafe extern "C" fn LLVMFuzzerRunDriver(
     .unwrap();
 
     if !options.unknown().is_empty() {
-        println!("Unrecognised options: {:?}", options.unknown());
+        eprintln!("Unrecognised options: {:?}", options.unknown());
+    }
+
+    for folder in options
+        .dirs()
+        .iter()
+        .chain(std::iter::once(options.artifact_prefix().dir()))
+    {
+        if !folder.try_exists().unwrap_or(false) {
+            eprintln!(
+                "Required folder {} did not exist; failing fast.",
+                folder.to_string_lossy()
+            );
+            _exit(1);
+        }
     }
 
     if *options.mode() != LibfuzzerMode::Tmin

libafl_libfuzzer/libafl_libfuzzer_runtime/src/merge.rs

@@ -8,7 +8,7 @@ use std::{
 };
 
 use libafl::{
-    corpus::{Corpus, OnDiskCorpus},
+    corpus::Corpus,
     events::{EventRestarter, SimpleRestartingEventManager},
     executors::{ExitKind, InProcessExecutor, TimeoutExecutor},
     feedback_and_fast, feedback_or_fast,
@@ -29,6 +29,7 @@ use libafl_bolts::{
 use libafl_targets::{OomFeedback, OomObserver, COUNTERS_MAPS};
 
 use crate::{
+    corpus::{ArtifactCorpus, LibfuzzerCorpus},
     feedbacks::{LibfuzzerCrashCauseFeedback, LibfuzzerKeepFeedback},
     observers::{MappedEdgeMapObserver, SizeTimeValueObserver},
     options::LibfuzzerOptions,
@@ -44,23 +45,7 @@ pub fn merge(
         return Err(Error::illegal_argument("Missing corpora to minimize; you should provide one directory to minimize into and one-to-many from which the inputs are loaded."));
     }
 
-    let crash_corpus = if let Some(prefix) = options.artifact_prefix() {
+    let crash_corpus = ArtifactCorpus::new();
-        OnDiskCorpus::with_meta_format_and_prefix(
-            prefix.dir(),
-            None,
-            prefix.filename_prefix().clone(),
-            true,
-        )
-        .unwrap()
-    } else {
-        OnDiskCorpus::with_meta_format_and_prefix(
-            &std::env::current_dir().unwrap(),
-            None,
-            None,
-            true,
-        )
-        .unwrap()
-    };
 
     let keep_observer = LibfuzzerKeepFeedback::new();
     let keep = keep_observer.keep();
@@ -130,7 +115,7 @@ pub fn merge(
 
     // A feedback to choose if an input is a solution or not
     let mut objective = feedback_or_fast!(
-        LibfuzzerCrashCauseFeedback::new(options.artifact_prefix().cloned()),
+        LibfuzzerCrashCauseFeedback::new(options.artifact_prefix().clone()),
         OomFeedback,
         CrashFeedback::new(),
         TimeoutFeedback::new()
@@ -163,7 +148,7 @@ pub fn merge(
             // RNG
             StdRand::new(),
             // Corpus that will be evolved, we keep it in memory for performance
-            OnDiskCorpus::with_meta_format_and_prefix(&corpus_dir, None, None, true).unwrap(),
+            LibfuzzerCorpus::new(corpus_dir, 4096),
             // Corpus in which we store solutions (crashes in this example),
             // on disk so the user can get them after stopping the fuzzer
             crash_corpus,

libafl_libfuzzer/libafl_libfuzzer_runtime/src/options.rs

@@ -2,6 +2,7 @@ use core::fmt::{Display, Formatter};
 use std::{path::PathBuf, time::Duration};
 
 use libafl::mutators::Tokens;
+use serde::{Deserialize, Serialize};
 
 use crate::options::RawOption::{Directory, Flag};
 
@@ -52,10 +53,10 @@ impl<'a> Display for OptionsParseError<'a> {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ArtifactPrefix {
     dir: PathBuf,
-    filename_prefix: Option<String>,
+    filename_prefix: String,
 }
 
 impl ArtifactPrefix {
@@ -64,10 +65,10 @@ impl ArtifactPrefix {
         if path.ends_with(std::path::MAIN_SEPARATOR) {
             Self {
                 dir,
-                filename_prefix: None,
+                filename_prefix: String::new(),
             }
         } else {
-            let filename_prefix = dir.file_name().map(|s| {
+            let filename_prefix = dir.file_name().map_or_else(String::new, |s| {
                 s.to_os_string()
                     .into_string()
                     .expect("Provided artifact prefix is not usable")
@@ -84,17 +85,26 @@ impl ArtifactPrefix {
         &self.dir
     }
 
-    pub fn filename_prefix(&self) -> &Option<String> {
+    pub fn filename_prefix(&self) -> &str {
         &self.filename_prefix
     }
 }
 
+impl Default for ArtifactPrefix {
+    fn default() -> Self {
+        Self {
+            dir: std::env::current_dir().expect("Must be able to get the current directory!"),
+            filename_prefix: String::new(),
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 #[allow(clippy::struct_excessive_bools)]
 pub struct LibfuzzerOptions {
     fuzzer_name: String,
     mode: LibfuzzerMode,
-    artifact_prefix: Option<ArtifactPrefix>,
+    artifact_prefix: ArtifactPrefix,
     timeout: Duration,
     grimoire: Option<bool>,
     forks: Option<usize>,
@@ -140,8 +150,8 @@ impl LibfuzzerOptions {
         &self.mode
     }
 
-    pub fn artifact_prefix(&self) -> Option<&ArtifactPrefix> {
+    pub fn artifact_prefix(&self) -> &ArtifactPrefix {
-        self.artifact_prefix.as_ref()
+        &self.artifact_prefix
     }
 
     pub fn timeout(&self) -> Duration {
@@ -333,7 +343,10 @@ impl<'a> LibfuzzerOptionsBuilder<'a> {
         LibfuzzerOptions {
             fuzzer_name,
             mode: self.mode.unwrap_or(LibfuzzerMode::Fuzz),
-            artifact_prefix: self.artifact_prefix.map(ArtifactPrefix::new),
+            artifact_prefix: self
+                .artifact_prefix
+                .map(ArtifactPrefix::new)
+                .unwrap_or_default(),
             timeout: self.timeout.unwrap_or(Duration::from_secs(1200)),
             grimoire: self.grimoire,
             forks: self.forks,

libafl_libfuzzer/libafl_libfuzzer_runtime/src/tmin.rs

@@ -1,7 +1,6 @@
 use std::{
     ffi::c_int,
     fs::{read, write},
-    path::PathBuf,
 };
 
 use libafl::{
@@ -119,21 +118,10 @@ fn minimize_crash_with_mutator<M: Mutator<BytesInput, TMinState>>(
             options.dirs()[0].as_path().as_os_str().to_str().unwrap()
         );
     } else {
-        let (mut dest, filename_prefix) = options.artifact_prefix().map_or_else(
+        let mut dest = options.artifact_prefix().dir().clone();
-            || (PathBuf::default(), ""),
-            |artifact_prefix| {
-                (
-                    artifact_prefix.dir().clone(),
-                    artifact_prefix
-                        .filename_prefix()
-                        .as_ref()
-                        .map_or("", String::as_str),
-                )
-            },
-        );
         dest.push(format!(
             "{}minimized-from-{}",
-            filename_prefix,
+            options.artifact_prefix().filename_prefix(),
             options.dirs()[0].file_name().unwrap().to_str().unwrap()
         ));
         write(&dest, input)?;