fix: gate ngrok free-tier bypass to loopback

docs/plugins/voice-call.md

@@ -104,6 +104,7 @@ Notes:
 - `mock` is a local dev provider (no network calls).
 - `skipSignatureVerification` is for local testing only.
 - If you use ngrok free tier, set `publicUrl` to the exact ngrok URL; signature verification is always enforced.
+- `tunnel.allowNgrokFreeTierLoopbackBypass: true` allows Twilio webhooks with invalid signatures **only** when `tunnel.provider="ngrok"` and `serve.bind` is loopback (ngrok local agent). Use for local dev only.
 - Ngrok free tier URLs can change or add interstitial behavior; if `publicUrl` drifts, Twilio signatures will fail. For production, prefer a stable domain or Tailscale funnel.
 
 ## TTS for calls

extensions/voice-call/CHANGELOG.md

@@ -6,6 +6,7 @@
 - Breaking: voice-call TTS now uses core `messages.tts` (plugin TTS config deep‑merges with core).
 - Telephony TTS supports OpenAI + ElevenLabs; Edge TTS is ignored for calls.
 - Removed legacy `tts.model`/`tts.voice`/`tts.instructions` plugin fields.
+- Ngrok free-tier bypass renamed to `tunnel.allowNgrokFreeTierLoopbackBypass` and gated to loopback + `tunnel.provider="ngrok"`.
 
 ## 2026.1.23
 

extensions/voice-call/README.md

@@ -74,6 +74,7 @@ Put under `plugins.entries.voice-call.config`:
 Notes:
 - Twilio/Telnyx/Plivo require a **publicly reachable** webhook URL.
 - `mock` is a local dev provider (no network calls).
+- `tunnel.allowNgrokFreeTierLoopbackBypass: true` allows Twilio webhooks with invalid signatures **only** when `tunnel.provider="ngrok"` and `serve.bind` is loopback (ngrok local agent). Use for local dev only.
 
 ## TTS for calls
 

extensions/voice-call/clawdbot.plugin.json

@@ -78,8 +78,8 @@
       "label": "ngrok Domain",
       "advanced": true
     },
-    "tunnel.allowNgrokFreeTier": {
-      "label": "Allow ngrok Free Tier",
+    "tunnel.allowNgrokFreeTierLoopbackBypass": {
+      "label": "Allow ngrok Free Tier (Loopback Bypass)",
       "advanced": true
     },
     "streaming.enabled": {
@@ -330,7 +330,7 @@
           "ngrokDomain": {
             "type": "string"
           },
-          "allowNgrokFreeTier": {
+          "allowNgrokFreeTierLoopbackBypass": {
             "type": "boolean"
           }
         }

extensions/voice-call/index.ts

@@ -62,8 +62,8 @@ const voiceCallConfigSchema = {
       advanced: true,
     },
     "tunnel.ngrokDomain": { label: "ngrok Domain", advanced: true },
-    "tunnel.allowNgrokFreeTier": {
-      label: "Allow ngrok Free Tier",
+    "tunnel.allowNgrokFreeTierLoopbackBypass": {
+      label: "Allow ngrok Free Tier (Loopback Bypass)",
       advanced: true,
     },
     "streaming.enabled": { label: "Enable Streaming", advanced: true },

extensions/voice-call/src/config.test.ts

@@ -19,7 +19,7 @@ function createBaseConfig(
     maxConcurrentCalls: 1,
     serve: { port: 3334, bind: "127.0.0.1", path: "/voice/webhook" },
     tailscale: { mode: "off", path: "/voice/webhook" },
-    tunnel: { provider: "none", allowNgrokFreeTier: false },
+    tunnel: { provider: "none", allowNgrokFreeTierLoopbackBypass: false },
     streaming: {
       enabled: false,
       sttProvider: "openai-realtime",

extensions/voice-call/src/config.ts

@@ -217,12 +217,17 @@ export const VoiceCallTunnelConfigSchema = z
     /**
      * Allow ngrok free tier compatibility mode.
      * When true, signature verification failures on ngrok-free.app URLs
-     * will include extra diagnostics. Signature verification is still required.
+     * will be allowed only for loopback requests (ngrok local agent).
      */
-    allowNgrokFreeTier: z.boolean().default(false),
+    allowNgrokFreeTierLoopbackBypass: z.boolean().default(false),
+    /**
+     * Legacy ngrok free tier compatibility mode (deprecated).
+     * Use allowNgrokFreeTierLoopbackBypass instead.
+     */
+    allowNgrokFreeTier: z.boolean().optional(),
   })
   .strict()
-  .default({ provider: "none", allowNgrokFreeTier: false });
+  .default({ provider: "none", allowNgrokFreeTierLoopbackBypass: false });
 export type VoiceCallTunnelConfig = z.infer<typeof VoiceCallTunnelConfigSchema>;
 
 // -----------------------------------------------------------------------------
@@ -419,8 +424,12 @@ export function resolveVoiceCallConfig(config: VoiceCallConfig): VoiceCallConfig
   // Tunnel Config
   resolved.tunnel = resolved.tunnel ?? {
     provider: "none",
-    allowNgrokFreeTier: false,
+    allowNgrokFreeTierLoopbackBypass: false,
   };
+  resolved.tunnel.allowNgrokFreeTierLoopbackBypass =
+    resolved.tunnel.allowNgrokFreeTierLoopbackBypass ||
+    resolved.tunnel.allowNgrokFreeTier ||
+    false;
   resolved.tunnel.ngrokAuthToken =
     resolved.tunnel.ngrokAuthToken ?? process.env.NGROK_AUTHTOKEN;
   resolved.tunnel.ngrokDomain =

extensions/voice-call/src/providers/twilio.ts

@@ -31,8 +31,8 @@ import { verifyTwilioProviderWebhook } from "./twilio/webhook.js";
  * @see https://www.twilio.com/docs/voice/media-streams
  */
 export interface TwilioProviderOptions {
-  /** Allow ngrok free tier compatibility mode (less secure) */
-  allowNgrokFreeTier?: boolean;
+  /** Allow ngrok free tier compatibility mode (loopback only, less secure) */
+  allowNgrokFreeTierLoopbackBypass?: boolean;
   /** Override public URL for signature verification */
   publicUrl?: string;
   /** Path for media stream WebSocket (e.g., /voice/stream) */

extensions/voice-call/src/providers/twilio/webhook.ts

@@ -11,7 +11,8 @@ export function verifyTwilioProviderWebhook(params: {
 }): WebhookVerificationResult {
   const result = verifyTwilioWebhook(params.ctx, params.authToken, {
     publicUrl: params.currentPublicUrl || undefined,
-    allowNgrokFreeTier: params.options.allowNgrokFreeTier ?? false,
+    allowNgrokFreeTierLoopbackBypass:
+      params.options.allowNgrokFreeTierLoopbackBypass ?? false,
     skipVerification: params.options.skipVerification,
   });
 

extensions/voice-call/src/runtime.ts

@@ -33,7 +33,19 @@ type Logger = {
   debug: (message: string) => void;
 };
 
+function isLoopbackBind(bind: string | undefined): boolean {
+  if (!bind) return false;
+  return bind === "127.0.0.1" || bind === "::1" || bind === "localhost";
+}
+
 function resolveProvider(config: VoiceCallConfig): VoiceCallProvider {
+  const allowNgrokFreeTierLoopbackBypass =
+    config.tunnel?.provider === "ngrok" &&
+    isLoopbackBind(config.serve?.bind) &&
+    (config.tunnel?.allowNgrokFreeTierLoopbackBypass ||
+      config.tunnel?.allowNgrokFreeTier ||
+      false);
+
   switch (config.provider) {
     case "telnyx":
       return new TelnyxProvider({
@@ -48,7 +60,7 @@ function resolveProvider(config: VoiceCallConfig): VoiceCallProvider {
           authToken: config.twilio?.authToken,
         },
         {
-          allowNgrokFreeTier: config.tunnel?.allowNgrokFreeTier ?? false,
+          allowNgrokFreeTierLoopbackBypass,
           publicUrl: config.publicUrl,
           skipVerification: config.skipSignatureVerification,
           streamPath: config.streaming?.enabled

extensions/voice-call/src/types.ts

@@ -180,6 +180,7 @@ export type WebhookContext = {
   url: string;
   method: "GET" | "POST" | "PUT" | "DELETE" | "PATCH";
   query?: Record<string, string | string[] | undefined>;
+  remoteAddress?: string;
 };
 
 export type ProviderWebhookParseResult = {

extensions/voice-call/src/webhook-security.test.ts

@@ -221,13 +221,40 @@ describe("verifyTwilioWebhook", () => {
         rawBody: postBody,
         url: "http://127.0.0.1:3334/voice/webhook",
         method: "POST",
+        remoteAddress: "203.0.113.10",
       },
       authToken,
-      { allowNgrokFreeTier: true },
+      { allowNgrokFreeTierLoopbackBypass: true },
     );
 
     expect(result.ok).toBe(false);
     expect(result.isNgrokFreeTier).toBe(true);
     expect(result.reason).toMatch(/Invalid signature/);
   });
+
+  it("allows invalid signatures for ngrok free tier only on loopback", () => {
+    const authToken = "test-auth-token";
+    const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
+
+    const result = verifyTwilioWebhook(
+      {
+        headers: {
+          host: "127.0.0.1:3334",
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "local.ngrok-free.app",
+          "x-twilio-signature": "invalid",
+        },
+        rawBody: postBody,
+        url: "http://127.0.0.1:3334/voice/webhook",
+        method: "POST",
+        remoteAddress: "127.0.0.1",
+      },
+      authToken,
+      { allowNgrokFreeTierLoopbackBypass: true },
+    );
+
+    expect(result.ok).toBe(true);
+    expect(result.isNgrokFreeTier).toBe(true);
+    expect(result.reason).toMatch(/compatibility mode/);
+  });
 });

extensions/voice-call/src/webhook-security.ts

@@ -131,6 +131,13 @@ function getHeader(
   return value;
 }
 
+function isLoopbackAddress(address?: string): boolean {
+  if (!address) return false;
+  if (address === "127.0.0.1" || address === "::1") return true;
+  if (address.startsWith("::ffff:127.")) return true;
+  return false;
+}
+
 /**
  * Result of Twilio webhook verification with detailed info.
  */
@@ -155,8 +162,8 @@ export function verifyTwilioWebhook(
   options?: {
     /** Override the public URL (e.g., from config) */
     publicUrl?: string;
-    /** Allow ngrok free tier compatibility mode (less secure) */
-    allowNgrokFreeTier?: boolean;
+    /** Allow ngrok free tier compatibility mode (loopback only, less secure) */
+    allowNgrokFreeTierLoopbackBypass?: boolean;
     /** Skip verification entirely (only for development) */
     skipVerification?: boolean;
   },
@@ -195,6 +202,22 @@ export function verifyTwilioWebhook(
     verificationUrl.includes(".ngrok-free.app") ||
     verificationUrl.includes(".ngrok.io");
 
+  if (
+    isNgrokFreeTier &&
+    options?.allowNgrokFreeTierLoopbackBypass &&
+    isLoopbackAddress(ctx.remoteAddress)
+  ) {
+    console.warn(
+      "[voice-call] Twilio signature validation failed (ngrok free tier compatibility, loopback only)",
+    );
+    return {
+      ok: true,
+      reason: "ngrok free tier compatibility mode (loopback only)",
+      verificationUrl,
+      isNgrokFreeTier: true,
+    };
+  }
+
   return {
     ok: false,
     reason: `Invalid signature for URL: ${verificationUrl}`,

extensions/voice-call/src/webhook.ts

@@ -252,6 +252,7 @@ export class VoiceCallWebhookServer {
       url: `http://${req.headers.host}${req.url}`,
       method: "POST",
       query: Object.fromEntries(url.searchParams),
+      remoteAddress: req.socket.remoteAddress ?? undefined,
     };
 
     // Verify signature