fuzz: Add a fuzz target for the HPKE message decoding

Author: poljar

afl/hpke-message-decoding/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "hpke-initial-message-decoding"
+version = "0.1.0"
+publish = false
+edition = "2021"
+
+[dependencies]
+afl = "*"
+
+[dependencies.vodozemac]
+path = "../.."
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]

afl/hpke-message-decoding/in/id:000000,time:0,execs:0,orig:test.bin

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "nightly"

afl/hpke-message-decoding/in/id:000001,src:000000,time:42,execs:183,op:havoc,rep:16,+cov

@@ -0,0 +1,12 @@
+use afl::fuzz;
+use vodozemac::hpke::InitialMessage;
+
+fn main() {
+    fuzz!(|data: &[u8]| {
+        if let Ok(decoded) = InitialMessage::from_bytes(data) {
+            let encoded = decoded.to_bytes();
+            let re_decoded = InitialMessage::from_bytes(&encoded).expect("Re-decoding should always succeed");
+            assert_eq!(decoded, re_decoded);
+        }
+    });
+}