feat: validate yonexus auth requests

plugin/core/runtime.ts

@@ -1,16 +1,26 @@
 import {
+  AUTH_ATTEMPT_WINDOW_SECONDS,
+  AUTH_MAX_ATTEMPTS_PER_WINDOW,
+  AUTH_RECENT_NONCE_WINDOW_SIZE,
   type BuiltinEnvelope,
   type HelloPayload,
   type PairConfirmPayload,
   YONEXUS_PROTOCOL_VERSION,
+  buildAuthFailed,
+  buildAuthSuccess,
   buildError,
   buildHelloAck,
   buildPairFailed,
   buildPairRequest,
   buildPairSuccess,
+  buildRePairRequired,
   decodeBuiltin,
   encodeBuiltin,
-  isBuiltinMessage
+  extractAuthRequestSigningInput,
+  isBuiltinMessage,
+  isTimestampFresh,
+  isValidAuthNonce,
+  type AuthRequestPayload
 } from "../../../Yonexus.Protocol/src/index.js";
 import type { YonexusServerConfig } from "./config.js";
 import {
@@ -21,6 +31,7 @@ import {
   type ClientRecord,
   type ServerRegistry
 } from "./persistence.js";
+import { verifySignature } from "../../../Yonexus.Client/plugin/crypto/keypair.js";
 import type { YonexusServerStore } from "./store.js";
 import { type ClientConnection, type ServerTransport } from "./transport.js";
 import { createPairingService, type PairingService } from "../services/pairing.js";
@@ -137,6 +148,14 @@ export class YonexusServerRuntime {
         connection,
         envelope as BuiltinEnvelope<"pair_confirm", PairConfirmPayload>
       );
+      return;
+    }
+
+    if (envelope.type === "auth_request") {
+      await this.handleAuthRequest(
+        connection,
+        envelope as BuiltinEnvelope<"auth_request", AuthRequestPayload>
+      );
     }
   }
 
@@ -313,6 +332,179 @@ export class YonexusServerRuntime {
     await this.persist();
   }
 
+  private async handleAuthRequest(
+    connection: ClientConnection,
+    envelope: BuiltinEnvelope<"auth_request", AuthRequestPayload>
+  ): Promise<void> {
+    const payload = envelope.payload;
+    if (!payload) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildError(
+            { code: "MALFORMED_MESSAGE", message: "auth_request payload is required" },
+            { requestId: envelope.requestId, timestamp: this.now() }
+          )
+        )
+      );
+      return;
+    }
+
+    const identifier = payload.identifier?.trim();
+    if (!identifier || !this.options.config.followerIdentifiers.includes(identifier)) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildAuthFailed(
+            {
+              identifier: identifier || "unknown",
+              reason: "unknown_identifier"
+            },
+            { requestId: envelope.requestId, timestamp: this.now() }
+          )
+        )
+      );
+      return;
+    }
+
+    const record = this.ensureClientRecord(identifier);
+    const session = this.registry.sessions.get(identifier);
+    if (!session || !canAuthenticate(record) || !record.secret || !record.publicKey) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildAuthFailed(
+            {
+              identifier,
+              reason: "not_paired"
+            },
+            { requestId: envelope.requestId, timestamp: this.now() }
+          )
+        )
+      );
+      return;
+    }
+
+    const now = this.now();
+    record.recentHandshakeAttempts = record.recentHandshakeAttempts.filter(
+      (timestamp) => now - timestamp < AUTH_ATTEMPT_WINDOW_SECONDS
+    );
+    record.recentHandshakeAttempts.push(now);
+
+    if (record.recentHandshakeAttempts.length > AUTH_MAX_ATTEMPTS_PER_WINDOW) {
+      await this.triggerRePairRequired(connection, record, envelope.requestId, "rate_limited");
+      return;
+    }
+
+    if (!isValidAuthNonce(payload.nonce)) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildAuthFailed(
+            {
+              identifier,
+              reason: "invalid_signature"
+            },
+            { requestId: envelope.requestId, timestamp: now }
+          )
+        )
+      );
+      return;
+    }
+
+    const freshness = isTimestampFresh(payload.proofTimestamp, now);
+    if (!freshness.ok) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildAuthFailed(
+            {
+              identifier,
+              reason: freshness.reason
+            },
+            { requestId: envelope.requestId, timestamp: now }
+          )
+        )
+      );
+      return;
+    }
+
+    const hasNonceCollision = record.recentNonces.some((entry) => entry.nonce === payload.nonce);
+    if (hasNonceCollision) {
+      await this.triggerRePairRequired(connection, record, envelope.requestId, "nonce_collision");
+      return;
+    }
+
+    const publicKey = payload.publicKey?.trim() || session.publicKey || record.publicKey;
+    if (!publicKey || publicKey !== record.publicKey) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildAuthFailed(
+            {
+              identifier,
+              reason: "invalid_signature"
+            },
+            { requestId: envelope.requestId, timestamp: now }
+          )
+        )
+      );
+      return;
+    }
+
+    const isValidSignature = await verifySignature(
+      publicKey,
+      extractAuthRequestSigningInput(payload, record.secret),
+      payload.signature
+    );
+
+    if (!isValidSignature) {
+      this.options.transport.sendToConnection(
+        connection,
+        encodeBuiltin(
+          buildAuthFailed(
+            {
+              identifier,
+              reason: "invalid_signature"
+            },
+            { requestId: envelope.requestId, timestamp: now }
+          )
+        )
+      );
+      return;
+    }
+
+    record.recentNonces = [...record.recentNonces, { nonce: payload.nonce, timestamp: now }].slice(
+      -AUTH_RECENT_NONCE_WINDOW_SIZE
+    );
+    record.lastAuthenticatedAt = now;
+    record.lastHeartbeatAt = now;
+    record.status = "online";
+    record.updatedAt = now;
+
+    if (session) {
+      session.isAuthenticated = true;
+      session.lastActivityAt = now;
+      session.publicKey = publicKey;
+    }
+    this.options.transport.markAuthenticated(identifier);
+    this.options.transport.sendToConnection(
+      { ...connection, identifier },
+      encodeBuiltin(
+        buildAuthSuccess(
+          {
+            identifier,
+            authenticatedAt: now,
+            status: "online"
+          },
+          { requestId: envelope.requestId, timestamp: now }
+        )
+      )
+    );
+
+    await this.persist();
+  }
+
   private determineNextAction(record: ClientRecord): "pair_required" | "auth_required" | "waiting_pair_confirm" {
     if (hasPendingPairing(record) && !isPairingExpired(record, this.now())) {
       return "waiting_pair_confirm";
@@ -398,6 +590,38 @@ export class YonexusServerRuntime {
     }
   }
 
+  private async triggerRePairRequired(
+    connection: ClientConnection,
+    record: ClientRecord,
+    requestId: string | undefined,
+    reason: "nonce_collision" | "rate_limited"
+  ): Promise<void> {
+    record.secret = undefined;
+    record.pairingStatus = "revoked";
+    record.pairingCode = undefined;
+    record.pairingExpiresAt = undefined;
+    record.pairingNotifyStatus = undefined;
+    record.recentNonces = [];
+    record.recentHandshakeAttempts = [];
+    record.status = "offline";
+    record.updatedAt = this.now();
+
+    this.options.transport.sendToConnection(
+      connection,
+      encodeBuiltin(
+        buildRePairRequired(
+          {
+            identifier: record.identifier,
+            reason
+          },
+          { requestId, timestamp: this.now() }
+        )
+      )
+    );
+
+    await this.persist();
+  }
+
   private async persist(): Promise<void> {
     await this.options.store.save(this.registry.clients.values());
   }