gix-config: Add fuzzer for file::Section

Author: nathaniel-brough

Cargo.lock

@@ -12,6 +12,7 @@ cargo-fuzz = true
 [dependencies]
 libfuzzer-sys = "0.4.7"
 arbitrary = { version = "1", features = ["derive"] }
+bstr = "1.8.0"
 
 [dependencies.gix-config]
 path = ".."
@@ -25,3 +26,9 @@ name = "parse"
 path = "fuzz_targets/parse.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "fuzz_file_section"
+path = "fuzz_targets/fuzz_file_section.rs"
+test = false
+doc = false

gix-config/fuzz/Cargo.toml

@@ -0,0 +1,39 @@
+#![no_main]
+
+use arbitrary::Arbitrary;
+use bstr::BStr;
+use gix_config::file::{Metadata, Section};
+use libfuzzer_sys::fuzz_target;
+use std::borrow::Cow;
+use std::hint::black_box;
+
+#[derive(Arbitrary, Debug)]
+struct Ctx<'a> {
+    name: Cow<'a, str>,
+    subsection: Option<&'a [u8]>,
+    #[arbitrary(default)]
+    meta: Metadata,
+    value_key: &'a str,
+}
+
+macro_rules! unwrap_or_return {
+    ($e:expr) => {
+        match $e {
+            Ok(val) => val,
+            Err(_) => return,
+        }
+    };
+}
+
+fuzz_target!(|ctx: Ctx| {
+    let section = unwrap_or_return!(Section::new(
+        ctx.name.clone(),
+        ctx.subsection.map(|x| Cow::from(BStr::new(x))),
+        ctx.meta.clone(),
+    ));
+    _ = black_box(section.values(ctx.value_key));
+    for key in section.keys() {
+        _ = black_box(section.value(key).expect("The key exists, so should the value."));
+    }
+    _ = black_box(section.to_bstring());
+});