Security fixes: swarm signature verification and error handling

src/app/api/swarm/gossip/route.ts

@@ -2,12 +2,15 @@
  * Swarm Gossip Endpoint
  * 
  * POST: Exchange node and handle information with other nodes
+ * 
+ * SECURITY: All requests must be cryptographically signed by the sender node.
  */
 
 import { NextResponse } from 'next/server';
 import { z } from 'zod';
 import { processGossip } from '@/lib/swarm/gossip';
 import { markNodeSuccess } from '@/lib/swarm/registry';
+import { verifySwarmRequest } from '@/lib/swarm/signature';
 import type { SwarmGossipPayload } from '@/lib/swarm/types';
 
 const handleSchema = z.object({
@@ -38,36 +41,55 @@ const gossipPayloadSchema = z.object({
   since: z.string().optional(),
 });
 
+// Schema including signature for verification
+const signedGossipSchema = gossipPayloadSchema.extend({
+  signature: z.string(),
+});
+
 /**
  * POST /api/swarm/gossip
  * 
  * Receives gossip from another node and responds with our own data.
  * This is the core of the epidemic protocol - nodes exchange what they know.
+ * 
+ * SECURITY: All gossip requests must be signed by the sender node.
  */
 export async function POST(request: Request) {
   try {
     const body = await request.json();
-    const payload = gossipPayloadSchema.parse(body) as SwarmGossipPayload;
+    const data = signedGossipSchema.parse(body);
     
     const ourDomain = process.env.NEXT_PUBLIC_NODE_DOMAIN;
     
     // Don't process gossip from ourselves
-    if (payload.sender === ourDomain) {
+    if (data.sender === ourDomain) {
       return NextResponse.json(
         { error: 'Cannot gossip with self' },
         { status: 400 }
       );
     }
 
-    console.log(`[Swarm] Gossip from ${payload.sender}: ${payload.nodes.length} nodes, ${payload.handles?.length || 0} handles`);
+    // SECURITY: Verify the node signature before processing
+    const { signature, ...payload } = data;
+    const isValid = await verifySwarmRequest(payload, signature, data.sender);
+
+    if (!isValid) {
+      console.warn(`[Swarm] Invalid signature for gossip from ${data.sender}`);
+      return NextResponse.json(
+        { error: 'Invalid signature' },
+        { status: 403 }
+      );
+    }
+
+    console.log(`[Swarm] Gossip from ${data.sender}: ${data.nodes.length} nodes, ${data.handles?.length || 0} handles`);
 
     // Process the incoming gossip and build our response
-    const response = await processGossip(payload);
+    const response = await processGossip(payload as SwarmGossipPayload);
     
     // Mark the sender as successfully contacted
-    await markNodeSuccess(payload.sender);
+    await markNodeSuccess(data.sender);
 
-    console.log(`[Swarm] Gossip response to ${payload.sender}: ${response.nodes.length} nodes, ${response.handles?.length || 0} handles`);
+    console.log(`[Swarm] Gossip response to ${data.sender}: ${response.nodes.length} nodes, ${response.handles?.length || 0} handles`);
 
     return NextResponse.json(response);
   } catch (error) {