initial commit

Signed-off-by: Kamal Tufekcic <kamal@lo.sh>

soliton/fuzz/fuzz_targets/fuzz_auth_respond.rs

@@ -0,0 +1,33 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+use soliton::{
+    auth::auth_respond,
+    identity::{generate_identity, GeneratedIdentity, IdentitySecretKey},
+    primitives::xwing,
+};
+use std::sync::LazyLock;
+
+struct ClientKeys {
+    sk: IdentitySecretKey,
+}
+
+// Fixed client identity — keygen is expensive, amortise across corpus runs.
+static CLIENT: LazyLock<ClientKeys> = LazyLock::new(|| {
+    let GeneratedIdentity { secret_key: sk, .. } = generate_identity().unwrap();
+    ClientKeys { sk }
+});
+
+const CT_SIZE: usize = 1120;
+
+fuzz_target!(|data: &[u8]| {
+    if data.len() < CT_SIZE {
+        return;
+    }
+    let Ok(ct) = xwing::Ciphertext::from_bytes(data[..CT_SIZE].to_vec()) else { return; };
+
+    // auth_respond must never panic regardless of ciphertext content.
+    // Exercises: X-Wing decapsulation with arbitrary ct, HMAC-SHA256 derivation.
+    // KEM decapsulation always "succeeds" (returns some shared secret); the HMAC
+    // path always runs and the result is returned as Zeroizing<[u8; 32]>.
+    let _ = auth_respond(&CLIENT.sk, &ct);
+});