Fuzzing for the json decoder

Hey it seems like it's working!

fuzz/.gitignore

@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage

fuzz/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "fwd-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.fwd]
+path = ".."
+
+[[bin]]
+name = "fuzz_target_1"
+path = "fuzz_targets/fuzz_target_1.rs"
+test = false
+doc = false
+bench = false

fuzz/fuzz_targets/fuzz_target_1.rs

@@ -0,0 +1,11 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+
+extern crate fwd;
+use fwd::server::refresh::docker::JsonValue;
+
+fuzz_target!(|data: &[u8]| {
+    // fuzzed code goes here
+    let _ = JsonValue::parse(data);
+});

src/lib.rs

@@ -1,7 +1,7 @@
 mod client;
 mod message;
 mod reverse;
-mod server;
+pub mod server;
 
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");
 pub const REV: &str = env!("REPO_REV");

src/server/mod.rs

@@ -5,7 +5,7 @@ use log::{error, warn};
 use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt, BufReader, BufWriter};
 use tokio::sync::mpsc;
 
-mod refresh;
+pub mod refresh;
 
 // We drive writes through an mpsc queue, because we not only handle requests
 // and responses from the client (refresh ports and the like) but also need

src/server/refresh.rs

@@ -10,7 +10,7 @@ use crate::message::PortDesc;
 mod procfs;
 
 #[cfg(unix)]
-mod docker;
+pub mod docker;
 
 pub async fn get_entries(_send_anonymous: bool) -> Result<Vec<PortDesc>> {
     #[cfg_attr(not(target_os = "linux"), allow(unused_mut))]

src/server/refresh/docker.rs

@@ -77,7 +77,7 @@ async fn list_containers() -> Result<Vec<u8>> {
 }
 
 #[derive(Debug, PartialEq)]
-enum JsonValue {
+pub enum JsonValue {
     Null,
     True,
     False,
@@ -207,7 +207,7 @@ impl JsonValue {
                         }
                         i += 1;
                     }
-                    if i == blob.len() {
+                    if i >= blob.len() {
                         bail!("Unterminated string at {i}");
                     }
                     assert_eq!(blob[i], b'"');
@@ -874,4 +874,10 @@ mod test {
         ]);
         assert_eq!(result, expected);
     }
+
+    #[test]
+    pub fn json_decode_unterminated_string_with_escape() {
+        let input = b"\"\\";
+        let _ = JsonValue::parse(input);
+    }
 }