[noise] structs for handshake response

quicktap/src/noise/handshake/response.rs

@@ -1 +1,42 @@
 //! `Noise_IKpsk2` handshake response packet
+
+use crate::noise::handshake::{HandshakeState, needs_cookie};
+use crate::qcrypto::hashes::{qcrypto_hash_twice, qcrypto_mac};
+use crate::qcrypto::LABEL_MAC1;
+
+struct HandshakeResponseRaw {
+    sender: [u8; 4],
+    receiver: [u8; 4],
+    ephemeral: [u8; 32],
+    empty: [u8; 0 + 16],
+}
+impl HandshakeResponseRaw {
+    fn to_bytes(&self, session: &mut HandshakeState) -> [u8; 92] {
+        let mut output_array = [0u8; 92];
+
+        output_array[0] = 2u8;
+        output_array[4..8].copy_from_slice(&self.sender);
+        output_array[8..12].copy_from_slice(&self.receiver);
+        output_array[12..44].copy_from_slice(&self.ephemeral);
+        output_array[44..60].copy_from_slice(&self.empty);
+
+        let mac1: [u8; 16] = qcrypto_mac(&qcrypto_hash_twice(LABEL_MAC1.as_bytes(), session.s_pub_i.as_bytes()), &output_array[..116]);
+
+        output_array[116..132].copy_from_slice(&mac1);
+
+        let mac2 = if needs_cookie(session) { qcrypto_mac(&session.cookies[session.cookies.len() - 1].cookie, &output_array[..132]) } else { [0u8; 16] };
+
+        output_array[132..148].copy_from_slice(&mac2);
+
+        output_array
+    }
+
+    fn from_bytes(packet: [u8; 92]) -> Self {
+        Self {
+            sender: packet[4..8].try_into().unwrap(),
+            receiver: packet[8..12].try_into().unwrap(),
+            ephemeral: packet[12..44].try_into().unwrap(),
+            empty: packet[44..60].try_into().unwrap(),
+        }
+    }
+}