1 files changed, 10 insertions, 0 deletions
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 0bffeae..624c3c3 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -248,6 +248,10 @@ class MeshBayTransport {
       // Kept for the life of the connection: a join_request is signed over it,
       // which is what stops one being lifted onto another connection.
       this._nonceNode = nonceNode;
+      // Announced in the challenge because joining needs it before the ack: a
+      // first-time member has no GEK, so they cannot complete the handshake that
+      // would prove this key. Unverified here; checked against the ack below.
+      this.nodePk = reply.node_pk || null;
       const gid = groupId || '';
 
       const proof = await C.handshakeProof(
@@ -281,6 +285,12 @@ class MeshBayTransport {
       // fails the GEK proof — this covers the case where an attacker HAS the GEK
       // (an ex-member, or a leaked key) and swaps the node underneath.
       // Strict refusal: a warning users can click through is decorative.
+      // The key announced in the challenge must be the one that just proved
+      // itself. A peer that changed identity mid-handshake is not one to trust
+      // with anything, including a join we may already have signed for it.
+      if (this.nodePk && this.nodePk !== ack.node_pk) {
+        throw new Error('Node identity changed during the handshake — refusing');
+      }
       _checkNodePin(nodeId, ack.node_pk);
       this.nodePk = ack.node_pk;