Use listings for baby_fuzzer book chapter (#1289)

* Clarify setup steps for the baby fuzzer

Specifically:
- Explicitly mention that the dependency path must point to a specific
  directory in the cloned repo (and not the root directory)
- Explicitly mention how to manually trigger the panic in the harness
  for testing purposes

* Clean up documentation on the baby fuzzer

Since the baby fuzzer chapter of the documentation is done in a
"tutorial", step-by-step fashion, it would be nice to be able to see
where exactly new lines have to be placed in the existing code. To that
end, the code used in the tutorial is moved to snippets (as is done in
the Rust Book), as it allows for much more convenient maintenance of the
snippets, as well as easy hiding of the non-important code on any given
snippet.

Furthermore, a few minor fixes are applied; a typo on a comment and a
missing unsafe block.

* Fix code snippet attributes for baby fuzzer

Specifically:
- Remove unnecessary `compile_fail` attribute
- Add `ignore` attribute to the snippets of the complete baby fuzzer. As
  explained in [#1290], it is expected for the baby fuzzer to return a
  non-0 exit code, so this should not trigger a failure during `mdbook
  test`.

* Fix CLI snippet language

For CLI snippets, the "language" should be set to `console`.

* Remove nested safe block in baby_fuzzer listings

Author: kokkonisd

docs/.gitignore

@@ -1 +1,2 @@
 book
+!listings/**/*

docs/listings/baby_fuzzer/listing-01/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "baby_fuzzer"
+version = "0.1.0"
+authors = ["Your Name <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

docs/listings/baby_fuzzer/listing-01/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

docs/listings/baby_fuzzer/listing-02/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "baby_fuzzer"
+version = "0.1.0"
+authors = ["Your Name <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+libafl = { path = "path/to/libafl/" }
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+lto = true
+codegen-units = 1
+opt-level = 3
+debug = true

docs/listings/baby_fuzzer/listing-02/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

docs/listings/baby_fuzzer/listing-03/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "baby_fuzzer"
+version = "0.1.0"
+authors = ["Your Name <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+libafl = { path = "path/to/libafl/" }
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+lto = true
+codegen-units = 1
+opt-level = 3
+debug = true
+
+[features]
+panic = []

docs/listings/baby_fuzzer/listing-03/src/main.rs

@@ -0,0 +1,25 @@
+extern crate libafl;
+use libafl::{
+    bolts::AsSlice,
+    executors::ExitKind,
+    inputs::{BytesInput, HasTargetBytes},
+};
+
+fn main() {
+    let mut harness = |input: &BytesInput| {
+        let target = input.target_bytes();
+        let buf = target.as_slice();
+        if buf.len() > 0 && buf[0] == 'a' as u8 {
+            if buf.len() > 1 && buf[1] == 'b' as u8 {
+                if buf.len() > 2 && buf[2] == 'c' as u8 {
+                    panic!("=)");
+                }
+            }
+        }
+        ExitKind::Ok
+    };
+    // To test the panic:
+    let input = BytesInput::new(Vec::from("abc"));
+    #[cfg(feature = "panic")]
+    harness(&input);
+}

docs/listings/baby_fuzzer/listing-04/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "baby_fuzzer"
+version = "0.1.0"
+authors = ["Your Name <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+libafl = { path = "path/to/libafl/" }
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+lto = true
+codegen-units = 1
+opt-level = 3
+debug = true
+
+[features]
+panic = []

docs/listings/baby_fuzzer/listing-04/src/main.rs

@@ -0,0 +1,85 @@
+/* ANCHOR: use */
+extern crate libafl;
+
+use libafl::{
+    bolts::{current_nanos, rands::StdRand, AsSlice},
+    corpus::{InMemoryCorpus, OnDiskCorpus},
+    events::SimpleEventManager,
+    executors::{inprocess::InProcessExecutor, ExitKind},
+    fuzzer::StdFuzzer,
+    generators::RandPrintablesGenerator,
+    inputs::{BytesInput, HasTargetBytes},
+    monitors::SimpleMonitor,
+    schedulers::QueueScheduler,
+    state::StdState,
+};
+use std::path::PathBuf;
+/* ANCHOR_END: use */
+
+fn main() {
+    let mut harness = |input: &BytesInput| {
+        let target = input.target_bytes();
+        let buf = target.as_slice();
+        if buf.len() > 0 && buf[0] == 'a' as u8 {
+            if buf.len() > 1 && buf[1] == 'b' as u8 {
+                if buf.len() > 2 && buf[2] == 'c' as u8 {
+                    panic!("=)");
+                }
+            }
+        }
+        ExitKind::Ok
+    };
+    // To test the panic:
+    let input = BytesInput::new(Vec::from("abc"));
+    #[cfg(feature = "panic")]
+    harness(&input);
+
+    /* ANCHOR: state */
+    // create a State from scratch
+    let mut state = StdState::new(
+        // RNG
+        StdRand::with_seed(current_nanos()),
+        // Corpus that will be evolved, we keep it in memory for performance
+        InMemoryCorpus::new(),
+        // Corpus in which we store solutions (crashes in this example),
+        // on disk so the user can get them after stopping the fuzzer
+        OnDiskCorpus::new(PathBuf::from("./crashes")).unwrap(),
+        &mut (),
+        &mut (),
+    )
+    .unwrap();
+    /* ANCHOR_END: state */
+
+    /* ANCHOR: event_manager */
+    // The Monitor trait defines how the fuzzer stats are displayed to the user
+    let mon = SimpleMonitor::new(|s| println!("{s}"));
+
+    // The event manager handles the various events generated during the fuzzing loop
+    // such as the notification of the addition of a new item to the corpus
+    let mut mgr = SimpleEventManager::new(mon);
+    /* ANCHOR_END: event_manager */
+
+    /* ANCHOR: scheduler_fuzzer */
+    // A queue policy to get testcasess from the corpus
+    let scheduler = QueueScheduler::new();
+
+    // A fuzzer with feedbacks and a corpus scheduler
+    let mut fuzzer = StdFuzzer::new(scheduler, (), ());
+    /* ANCHOR_END: scheduler_fuzzer */
+
+    /* ANCHOR: executor */
+    // Create the executor for an in-process function
+    let mut executor = InProcessExecutor::new(&mut harness, (), &mut fuzzer, &mut state, &mut mgr)
+        .expect("Failed to create the Executor");
+    /* ANCHOR_END: executor */
+
+    /* ANCHOR: generator */
+    // Generator of printable bytearrays of max size 32
+    let mut generator = RandPrintablesGenerator::new(32);
+
+    // Generate 8 initial inputs
+    state
+        .generate_initial_inputs(&mut fuzzer, &mut executor, &mut generator, &mut mgr, 8)
+        .expect("Failed to generate the initial corpus");
+    /* ANCHOR_END: generator */
+}

docs/listings/baby_fuzzer/listing-05/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "baby_fuzzer"
+version = "0.1.0"
+authors = ["Your Name <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+libafl = { path = "path/to/libafl/" }
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+lto = true
+codegen-units = 1
+opt-level = 3
+debug = true
+
+[features]
+panic = []