huskies: merge 728_story_cryptographic_peer_handshake_with_trusted_keys_gating

server/src/crdt_state/presence.rs

@@ -34,6 +34,22 @@ pub fn sign_challenge(challenge: &str) -> Option<(String, String)> {
     Some((pubkey_hex, sig_hex))
 }
 
+/// Sign a versioned challenge `"huskies-v1:{nonce}"` for the extended WebSocket
+/// mutual-auth handshake (responding node side).
+///
+/// The signature covers the full versioned string (not just the nonce), so an
+/// attacker cannot replay a signature from a previous handshake or a different
+/// protocol version.
+///
+/// Returns `(pubkey_hex, signature_hex)` or `None` before `init()`.
+pub fn sign_versioned_challenge(nonce: &str) -> Option<(String, String)> {
+    let state = get_crdt()?.lock().ok()?;
+    let pubkey_hex = crate::node_identity::public_key_hex(&state.keypair);
+    let versioned = format!("huskies-v1:{nonce}");
+    let sig_hex = crate::node_identity::sign_challenge(&state.keypair, &versioned);
+    Some((pubkey_hex, sig_hex))
+}
+
 /// Write a claim on a pipeline item via CRDT.
 ///
 /// Sets `claimed_by` to this node's ID and `claimed_at` to the current time.