fix: harden voice-call webhook verification

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

@@ -17,6 +17,11 @@ function createBaseConfig(provider: "telnyx" | "twilio" | "plivo" | "mock"): Voi
     serve: { port: 3334, bind: "127.0.0.1", path: "/voice/webhook" },
     tailscale: { mode: "off", path: "/voice/webhook" },
     tunnel: { provider: "none", allowNgrokFreeTierLoopbackBypass: false },
+    webhookSecurity: {
+      allowedHosts: [],
+      trustForwardingHeaders: false,
+      trustedProxyIPs: [],
+    },
     streaming: {
       enabled: false,
       sttProvider: "openai-realtime",

extensions/voice-call/src/config.ts

@@ -211,16 +211,37 @@ export const VoiceCallTunnelConfigSchema = z
      * will be allowed only for loopback requests (ngrok local agent).
      */
     allowNgrokFreeTierLoopbackBypass: z.boolean().default(false),
-    /**
-     * Legacy ngrok free tier compatibility mode (deprecated).
-     * Use allowNgrokFreeTierLoopbackBypass instead.
-     */
-    allowNgrokFreeTier: z.boolean().optional(),
   })
   .strict()
   .default({ provider: "none", allowNgrokFreeTierLoopbackBypass: false });
 export type VoiceCallTunnelConfig = z.infer<typeof VoiceCallTunnelConfigSchema>;
 
+// -----------------------------------------------------------------------------
+// Webhook Security Configuration
+// -----------------------------------------------------------------------------
+
+export const VoiceCallWebhookSecurityConfigSchema = z
+  .object({
+    /**
+     * Allowed hostnames for webhook URL reconstruction.
+     * Only these hosts are accepted from forwarding headers.
+     */
+    allowedHosts: z.array(z.string().min(1)).default([]),
+    /**
+     * Trust X-Forwarded-* headers without a hostname allowlist.
+     * WARNING: Only enable if you trust your proxy configuration.
+     */
+    trustForwardingHeaders: z.boolean().default(false),
+    /**
+     * Trusted proxy IP addresses. Forwarded headers are only trusted when
+     * the remote IP matches one of these addresses.
+     */
+    trustedProxyIPs: z.array(z.string().min(1)).default([]),
+  })
+  .strict()
+  .default({ allowedHosts: [], trustForwardingHeaders: false, trustedProxyIPs: [] });
+export type WebhookSecurityConfig = z.infer<typeof VoiceCallWebhookSecurityConfigSchema>;
+
 // -----------------------------------------------------------------------------
 // Outbound Call Configuration
 // -----------------------------------------------------------------------------
@@ -339,6 +360,9 @@ export const VoiceCallConfigSchema = z
     /** Tunnel configuration (unified ngrok/tailscale) */
     tunnel: VoiceCallTunnelConfigSchema,
 
+    /** Webhook signature reconstruction and proxy trust configuration */
+    webhookSecurity: VoiceCallWebhookSecurityConfigSchema,
+
     /** Real-time audio streaming configuration */
     streaming: VoiceCallStreamingConfigSchema,
 
@@ -409,10 +433,21 @@ export function resolveVoiceCallConfig(config: VoiceCallConfig): VoiceCallConfig
     allowNgrokFreeTierLoopbackBypass: false,
   };
   resolved.tunnel.allowNgrokFreeTierLoopbackBypass =
-    resolved.tunnel.allowNgrokFreeTierLoopbackBypass || resolved.tunnel.allowNgrokFreeTier || false;
+    resolved.tunnel.allowNgrokFreeTierLoopbackBypass ?? false;
   resolved.tunnel.ngrokAuthToken = resolved.tunnel.ngrokAuthToken ?? process.env.NGROK_AUTHTOKEN;
   resolved.tunnel.ngrokDomain = resolved.tunnel.ngrokDomain ?? process.env.NGROK_DOMAIN;
 
+  // Webhook Security Config
+  resolved.webhookSecurity = resolved.webhookSecurity ?? {
+    allowedHosts: [],
+    trustForwardingHeaders: false,
+    trustedProxyIPs: [],
+  };
+  resolved.webhookSecurity.allowedHosts = resolved.webhookSecurity.allowedHosts ?? [];
+  resolved.webhookSecurity.trustForwardingHeaders =
+    resolved.webhookSecurity.trustForwardingHeaders ?? false;
+  resolved.webhookSecurity.trustedProxyIPs = resolved.webhookSecurity.trustedProxyIPs ?? [];
+
   return resolved;
 }
 

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

@@ -1,5 +1,5 @@
 import crypto from "node:crypto";
-import type { PlivoConfig } from "../config.js";
+import type { PlivoConfig, WebhookSecurityConfig } from "../config.js";
 import type {
   HangupCallInput,
   InitiateCallInput,
@@ -23,6 +23,8 @@ export interface PlivoProviderOptions {
   skipVerification?: boolean;
   /** Outbound ring timeout in seconds */
   ringTimeoutSec?: number;
+  /** Webhook security options (forwarded headers/allowlist) */
+  webhookSecurity?: WebhookSecurityConfig;
 }
 
 type PendingSpeak = { text: string; locale?: string };
@@ -92,6 +94,10 @@ export class PlivoProvider implements VoiceCallProvider {
     const result = verifyPlivoWebhook(ctx, this.authToken, {
       publicUrl: this.options.publicUrl,
       skipVerification: this.options.skipVerification,
+      allowedHosts: this.options.webhookSecurity?.allowedHosts,
+      trustForwardingHeaders: this.options.webhookSecurity?.trustForwardingHeaders,
+      trustedProxyIPs: this.options.webhookSecurity?.trustedProxyIPs,
+      remoteIP: ctx.remoteAddress,
     });
 
     if (!result.ok) {
@@ -112,7 +118,7 @@ export class PlivoProvider implements VoiceCallProvider {
     // Keep providerCallId mapping for later call control.
     const callUuid = parsed.get("CallUUID") || undefined;
     if (callUuid) {
-      const webhookBase = PlivoProvider.baseWebhookUrlFromCtx(ctx);
+      const webhookBase = this.baseWebhookUrlFromCtx(ctx);
       if (webhookBase) {
         this.callUuidToWebhookUrl.set(callUuid, webhookBase);
       }
@@ -444,7 +450,7 @@ export class PlivoProvider implements VoiceCallProvider {
     ctx: WebhookContext,
     opts: { flow: string; callId?: string },
   ): string | null {
-    const base = PlivoProvider.baseWebhookUrlFromCtx(ctx);
+    const base = this.baseWebhookUrlFromCtx(ctx);
     if (!base) {
       return null;
     }
@@ -458,9 +464,16 @@ export class PlivoProvider implements VoiceCallProvider {
     return u.toString();
   }
 
-  private static baseWebhookUrlFromCtx(ctx: WebhookContext): string | null {
+  private baseWebhookUrlFromCtx(ctx: WebhookContext): string | null {
     try {
-      const u = new URL(reconstructWebhookUrl(ctx));
+      const u = new URL(
+        reconstructWebhookUrl(ctx, {
+          allowedHosts: this.options.webhookSecurity?.allowedHosts,
+          trustForwardingHeaders: this.options.webhookSecurity?.trustForwardingHeaders,
+          trustedProxyIPs: this.options.webhookSecurity?.trustedProxyIPs,
+          remoteIP: ctx.remoteAddress,
+        }),
+      );
       return `${u.origin}${u.pathname}`;
     } catch {
       return null;

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

@@ -1,5 +1,5 @@
 import crypto from "node:crypto";
-import type { TwilioConfig } from "../config.js";
+import type { TwilioConfig, WebhookSecurityConfig } from "../config.js";
 import type { MediaStreamHandler } from "../media-stream.js";
 import type { TelephonyTtsProvider } from "../telephony-tts.js";
 import type {
@@ -38,6 +38,8 @@ export interface TwilioProviderOptions {
   streamPath?: string;
   /** Skip webhook signature verification (development only) */
   skipVerification?: boolean;
+  /** Webhook security options (forwarded headers/allowlist) */
+  webhookSecurity?: WebhookSecurityConfig;
 }
 
 export class TwilioProvider implements VoiceCallProvider {

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

@@ -12,6 +12,10 @@ export function verifyTwilioProviderWebhook(params: {
     publicUrl: params.currentPublicUrl || undefined,
     allowNgrokFreeTierLoopbackBypass: params.options.allowNgrokFreeTierLoopbackBypass ?? false,
     skipVerification: params.options.skipVerification,
+    allowedHosts: params.options.webhookSecurity?.allowedHosts,
+    trustForwardingHeaders: params.options.webhookSecurity?.trustForwardingHeaders,
+    trustedProxyIPs: params.options.webhookSecurity?.trustedProxyIPs,
+    remoteIP: params.ctx.remoteAddress,
   });
 
   if (!result.ok) {

extensions/voice-call/src/runtime.ts

@@ -44,7 +44,7 @@ function resolveProvider(config: VoiceCallConfig): VoiceCallProvider {
   const allowNgrokFreeTierLoopbackBypass =
     config.tunnel?.provider === "ngrok" &&
     isLoopbackBind(config.serve?.bind) &&
-    (config.tunnel?.allowNgrokFreeTierLoopbackBypass || config.tunnel?.allowNgrokFreeTier || false);
+    (config.tunnel?.allowNgrokFreeTierLoopbackBypass ?? false);
 
   switch (config.provider) {
     case "telnyx":
@@ -70,6 +70,7 @@ function resolveProvider(config: VoiceCallConfig): VoiceCallProvider {
           publicUrl: config.publicUrl,
           skipVerification: config.skipSignatureVerification,
           streamPath: config.streaming?.enabled ? config.streaming.streamPath : undefined,
+          webhookSecurity: config.webhookSecurity,
         },
       );
     case "plivo":
@@ -82,6 +83,7 @@ function resolveProvider(config: VoiceCallConfig): VoiceCallProvider {
           publicUrl: config.publicUrl,
           skipVerification: config.skipSignatureVerification,
           ringTimeoutSec: Math.max(1, Math.floor(config.ringTimeoutMs / 1000)),
+          webhookSecurity: config.webhookSecurity,
         },
       );
     case "mock":

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

@@ -197,7 +197,7 @@ describe("verifyTwilioWebhook", () => {
     expect(result.ok).toBe(true);
   });
 
-  it("rejects invalid signatures even with ngrok free tier enabled", () => {
+  it("rejects invalid signatures even when attacker injects forwarded host", () => {
     const authToken = "test-auth-token";
     const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
 
@@ -212,14 +212,13 @@ describe("verifyTwilioWebhook", () => {
         rawBody: postBody,
         url: "http://127.0.0.1:3334/voice/webhook",
         method: "POST",
-        remoteAddress: "203.0.113.10",
       },
       authToken,
-      { allowNgrokFreeTierLoopbackBypass: true },
     );
 
     expect(result.ok).toBe(false);
-    expect(result.isNgrokFreeTier).toBe(true);
+    // X-Forwarded-Host is ignored by default, so URL uses Host header
+    expect(result.isNgrokFreeTier).toBe(false);
     expect(result.reason).toMatch(/Invalid signature/);
   });
 
@@ -248,4 +247,131 @@ describe("verifyTwilioWebhook", () => {
     expect(result.isNgrokFreeTier).toBe(true);
     expect(result.reason).toMatch(/compatibility mode/);
   });
+
+  it("ignores attacker X-Forwarded-Host without allowedHosts or trustForwardingHeaders", () => {
+    const authToken = "test-auth-token";
+    const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
+
+    // Attacker tries to inject their host - should be ignored
+    const result = verifyTwilioWebhook(
+      {
+        headers: {
+          host: "legitimate.example.com",
+          "x-forwarded-host": "attacker.evil.com",
+          "x-twilio-signature": "invalid",
+        },
+        rawBody: postBody,
+        url: "http://localhost:3000/voice/webhook",
+        method: "POST",
+      },
+      authToken,
+    );
+
+    expect(result.ok).toBe(false);
+    // Attacker's host is ignored - uses Host header instead
+    expect(result.verificationUrl).toBe("https://legitimate.example.com/voice/webhook");
+  });
+
+  it("uses X-Forwarded-Host when allowedHosts whitelist is provided", () => {
+    const authToken = "test-auth-token";
+    const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
+    const webhookUrl = "https://myapp.ngrok.io/voice/webhook";
+
+    const signature = twilioSignature({ authToken, url: webhookUrl, postBody });
+
+    const result = verifyTwilioWebhook(
+      {
+        headers: {
+          host: "localhost:3000",
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "myapp.ngrok.io",
+          "x-twilio-signature": signature,
+        },
+        rawBody: postBody,
+        url: "http://localhost:3000/voice/webhook",
+        method: "POST",
+      },
+      authToken,
+      { allowedHosts: ["myapp.ngrok.io"] },
+    );
+
+    expect(result.ok).toBe(true);
+    expect(result.verificationUrl).toBe(webhookUrl);
+  });
+
+  it("rejects X-Forwarded-Host not in allowedHosts whitelist", () => {
+    const authToken = "test-auth-token";
+    const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
+
+    const result = verifyTwilioWebhook(
+      {
+        headers: {
+          host: "localhost:3000",
+          "x-forwarded-host": "attacker.evil.com",
+          "x-twilio-signature": "invalid",
+        },
+        rawBody: postBody,
+        url: "http://localhost:3000/voice/webhook",
+        method: "POST",
+      },
+      authToken,
+      { allowedHosts: ["myapp.ngrok.io", "webhook.example.com"] },
+    );
+
+    expect(result.ok).toBe(false);
+    // Attacker's host not in whitelist, falls back to Host header
+    expect(result.verificationUrl).toBe("https://localhost/voice/webhook");
+  });
+
+  it("trusts forwarding headers only from trusted proxy IPs", () => {
+    const authToken = "test-auth-token";
+    const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
+    const webhookUrl = "https://proxy.example.com/voice/webhook";
+
+    const signature = twilioSignature({ authToken, url: webhookUrl, postBody });
+
+    const result = verifyTwilioWebhook(
+      {
+        headers: {
+          host: "localhost:3000",
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "proxy.example.com",
+          "x-twilio-signature": signature,
+        },
+        rawBody: postBody,
+        url: "http://localhost:3000/voice/webhook",
+        method: "POST",
+        remoteAddress: "203.0.113.10",
+      },
+      authToken,
+      { trustForwardingHeaders: true, trustedProxyIPs: ["203.0.113.10"] },
+    );
+
+    expect(result.ok).toBe(true);
+    expect(result.verificationUrl).toBe(webhookUrl);
+  });
+
+  it("ignores forwarding headers when trustedProxyIPs are set but remote IP is missing", () => {
+    const authToken = "test-auth-token";
+    const postBody = "CallSid=CS123&CallStatus=completed&From=%2B15550000000";
+
+    const result = verifyTwilioWebhook(
+      {
+        headers: {
+          host: "legitimate.example.com",
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "proxy.example.com",
+          "x-twilio-signature": "invalid",
+        },
+        rawBody: postBody,
+        url: "http://localhost:3000/voice/webhook",
+        method: "POST",
+      },
+      authToken,
+      { trustForwardingHeaders: true, trustedProxyIPs: ["203.0.113.10"] },
+    );
+
+    expect(result.ok).toBe(false);
+    expect(result.verificationUrl).toBe("https://legitimate.example.com/voice/webhook");
+  });
 });

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

@@ -57,9 +57,119 @@ function timingSafeEqual(a: string, b: string): boolean {
   return crypto.timingSafeEqual(bufA, bufB);
 }
 
+/**
+ * Configuration for secure URL reconstruction.
+ */
+export interface WebhookUrlOptions {
+  /**
+   * Whitelist of allowed hostnames. If provided, only these hosts will be
+   * accepted from forwarding headers. This prevents host header injection attacks.
+   *
+   * SECURITY: You must provide this OR set trustForwardingHeaders=true to use
+   * X-Forwarded-Host headers. Without either, forwarding headers are ignored.
+   */
+  allowedHosts?: string[];
+  /**
+   * Explicitly trust X-Forwarded-* headers without a whitelist.
+   * WARNING: Only set this to true if you trust your proxy configuration
+   * and understand the security implications.
+   *
+   * @default false
+   */
+  trustForwardingHeaders?: boolean;
+  /**
+   * List of trusted proxy IP addresses. X-Forwarded-* headers will only be
+   * trusted if the request comes from one of these IPs.
+   * Requires remoteIP to be set for validation.
+   */
+  trustedProxyIPs?: string[];
+  /**
+   * The IP address of the incoming request (for proxy validation).
+   */
+  remoteIP?: string;
+}
+
+/**
+ * Validate that a hostname matches RFC 1123 format.
+ * Prevents injection of malformed hostnames.
+ */
+function isValidHostname(hostname: string): boolean {
+  if (!hostname || hostname.length > 253) {
+    return false;
+  }
+  // RFC 1123 hostname: alphanumeric, hyphens, dots
+  // Also allow ngrok/tunnel subdomains
+  const hostnameRegex =
+    /^([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)*[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?$/;
+  return hostnameRegex.test(hostname);
+}
+
+/**
+ * Safely extract hostname from a host header value.
+ * Handles IPv6 addresses and prevents injection via malformed values.
+ */
+function extractHostname(hostHeader: string): string | null {
+  if (!hostHeader) {
+    return null;
+  }
+
+  let hostname: string;
+
+  // Handle IPv6 addresses: [::1]:8080
+  if (hostHeader.startsWith("[")) {
+    const endBracket = hostHeader.indexOf("]");
+    if (endBracket === -1) {
+      return null; // Malformed IPv6
+    }
+    hostname = hostHeader.substring(1, endBracket);
+    return hostname.toLowerCase();
+  }
+
+  // Handle IPv4/domain with optional port
+  // Check for @ which could indicate user info injection attempt
+  if (hostHeader.includes("@")) {
+    return null; // Reject potential injection: attacker.com:80@legitimate.com
+  }
+
+  hostname = hostHeader.split(":")[0];
+
+  // Validate the extracted hostname
+  if (!isValidHostname(hostname)) {
+    return null;
+  }
+
+  return hostname.toLowerCase();
+}
+
+function extractHostnameFromHeader(headerValue: string): string | null {
+  const first = headerValue.split(",")[0]?.trim();
+  if (!first) {
+    return null;
+  }
+  return extractHostname(first);
+}
+
+function normalizeAllowedHosts(allowedHosts?: string[]): Set<string> | null {
+  if (!allowedHosts || allowedHosts.length === 0) {
+    return null;
+  }
+  const normalized = new Set<string>();
+  for (const host of allowedHosts) {
+    const extracted = extractHostname(host.trim());
+    if (extracted) {
+      normalized.add(extracted);
+    }
+  }
+  return normalized.size > 0 ? normalized : null;
+}
+
 /**
  * Reconstruct the public webhook URL from request headers.
  *
+ * SECURITY: This function validates host headers to prevent host header
+ * injection attacks. When using forwarding headers (X-Forwarded-Host, etc.),
+ * always provide allowedHosts to whitelist valid hostnames.
+ *
  * When behind a reverse proxy (Tailscale, nginx, ngrok), the original URL
  * used by Twilio differs from the local request URL. We use standard
  * forwarding headers to reconstruct it.
@@ -70,17 +180,84 @@ function timingSafeEqual(a: string, b: string): boolean {
  * 3. Ngrok-Forwarded-Host (ngrok specific)
  * 4. Host header (direct connection)
  */
-export function reconstructWebhookUrl(ctx: WebhookContext): string {
+export function reconstructWebhookUrl(ctx: WebhookContext, options?: WebhookUrlOptions): string {
   const { headers } = ctx;
 
-  const proto = getHeader(headers, "x-forwarded-proto") || "https";
+  // SECURITY: Only trust forwarding headers if explicitly configured.
+  // Either allowedHosts must be set (for whitelist validation) or
+  // trustForwardingHeaders must be true (explicit opt-in to trust).
+  const allowedHosts = normalizeAllowedHosts(options?.allowedHosts);
+  const hasAllowedHosts = allowedHosts !== null;
+  const explicitlyTrusted = options?.trustForwardingHeaders === true;
 
-  const forwardedHost =
-    getHeader(headers, "x-forwarded-host") ||
-    getHeader(headers, "x-original-host") ||
-    getHeader(headers, "ngrok-forwarded-host") ||
-    getHeader(headers, "host") ||
-    "";
+  // Also check trusted proxy IPs if configured
+  const trustedProxyIPs = options?.trustedProxyIPs?.filter(Boolean) ?? [];
+  const hasTrustedProxyIPs = trustedProxyIPs.length > 0;
+  const remoteIP = options?.remoteIP ?? ctx.remoteAddress;
+  const fromTrustedProxy =
+    !hasTrustedProxyIPs || (remoteIP ? trustedProxyIPs.includes(remoteIP) : false);
+
+  // Only trust forwarding headers if: (has whitelist OR explicitly trusted) AND from trusted proxy
+  const shouldTrustForwardingHeaders = (hasAllowedHosts || explicitlyTrusted) && fromTrustedProxy;
+
+  const isAllowedForwardedHost = (host: string): boolean => !allowedHosts || allowedHosts.has(host);
+
+  // Determine protocol - only trust X-Forwarded-Proto from trusted proxies
+  let proto = "https";
+  if (shouldTrustForwardingHeaders) {
+    const forwardedProto = getHeader(headers, "x-forwarded-proto");
+    if (forwardedProto === "http" || forwardedProto === "https") {
+      proto = forwardedProto;
+    }
+  }
+
+  // Determine host - with security validation
+  let host: string | null = null;
+
+  if (shouldTrustForwardingHeaders) {
+    // Try forwarding headers in priority order
+    const forwardingHeaders = ["x-forwarded-host", "x-original-host", "ngrok-forwarded-host"];
+
+    for (const headerName of forwardingHeaders) {
+      const headerValue = getHeader(headers, headerName);
+      if (headerValue) {
+        const extracted = extractHostnameFromHeader(headerValue);
+        if (extracted && isAllowedForwardedHost(extracted)) {
+          host = extracted;
+          break;
+        }
+      }
+    }
+  }
+
+  // Fallback to Host header if no valid forwarding header found
+  if (!host) {
+    const hostHeader = getHeader(headers, "host");
+    if (hostHeader) {
+      const extracted = extractHostnameFromHeader(hostHeader);
+      if (extracted) {
+        host = extracted;
+      }
+    }
+  }
+
+  // Last resort: try to extract from ctx.url
+  if (!host) {
+    try {
+      const parsed = new URL(ctx.url);
+      const extracted = extractHostname(parsed.host);
+      if (extracted) {
+        host = extracted;
+      }
+    } catch {
+      // URL parsing failed - use empty string (will result in invalid URL)
+      host = "";
+    }
+  }
+
+  if (!host) {
+    host = "";
+  }
 
   // Extract path from the context URL (fallback to "/" on parse failure)
   let path = "/";
@@ -91,15 +268,16 @@ export function reconstructWebhookUrl(ctx: WebhookContext): string {
     // URL parsing failed
   }
 
-  // Remove port from host (ngrok URLs don't have ports)
-  const host = forwardedHost.split(":")[0] || forwardedHost;
-
   return `${proto}://${host}${path}`;
 }
 
-function buildTwilioVerificationUrl(ctx: WebhookContext, publicUrl?: string): string {
+function buildTwilioVerificationUrl(
+  ctx: WebhookContext,
+  publicUrl?: string,
+  urlOptions?: WebhookUrlOptions,
+): string {
   if (!publicUrl) {
-    return reconstructWebhookUrl(ctx);
+    return reconstructWebhookUrl(ctx, urlOptions);
   }
 
   try {
@@ -154,9 +332,6 @@ export interface TwilioVerificationResult {
 
 /**
  * Verify Twilio webhook with full context and detailed result.
- *
- * Handles the special case of ngrok free tier where signature validation
- * may fail due to URL discrepancies (ngrok adds interstitial page handling).
  */
 export function verifyTwilioWebhook(
   ctx: WebhookContext,
@@ -168,6 +343,26 @@ export function verifyTwilioWebhook(
     allowNgrokFreeTierLoopbackBypass?: boolean;
     /** Skip verification entirely (only for development) */
     skipVerification?: boolean;
+    /**
+     * Whitelist of allowed hostnames for host header validation.
+     * Prevents host header injection attacks.
+     */
+    allowedHosts?: string[];
+    /**
+     * Explicitly trust X-Forwarded-* headers without a whitelist.
+     * WARNING: Only enable if you trust your proxy configuration.
+     * @default false
+     */
+    trustForwardingHeaders?: boolean;
+    /**
+     * List of trusted proxy IP addresses. X-Forwarded-* headers will only
+     * be trusted from these IPs.
+     */
+    trustedProxyIPs?: string[];
+    /**
+     * The remote IP address of the request (for proxy validation).
+     */
+    remoteIP?: string;
   },
 ): TwilioVerificationResult {
   // Allow skipping verification for development/testing
@@ -181,8 +376,16 @@ export function verifyTwilioWebhook(
     return { ok: false, reason: "Missing X-Twilio-Signature header" };
   }
 
+  const isLoopback = isLoopbackAddress(options?.remoteIP ?? ctx.remoteAddress);
+  const allowLoopbackForwarding = options?.allowNgrokFreeTierLoopbackBypass && isLoopback;
+
   // Reconstruct the URL Twilio used
-  const verificationUrl = buildTwilioVerificationUrl(ctx, options?.publicUrl);
+  const verificationUrl = buildTwilioVerificationUrl(ctx, options?.publicUrl, {
+    allowedHosts: options?.allowedHosts,
+    trustForwardingHeaders: options?.trustForwardingHeaders || allowLoopbackForwarding,
+    trustedProxyIPs: options?.trustedProxyIPs,
+    remoteIP: options?.remoteIP,
+  });
 
   // Parse the body as URL-encoded params
   const params = new URLSearchParams(ctx.rawBody);
@@ -198,11 +401,7 @@ export function verifyTwilioWebhook(
   const isNgrokFreeTier =
     verificationUrl.includes(".ngrok-free.app") || verificationUrl.includes(".ngrok.io");
 
-  if (
-    isNgrokFreeTier &&
-    options?.allowNgrokFreeTierLoopbackBypass &&
-    isLoopbackAddress(ctx.remoteAddress)
-  ) {
+  if (isNgrokFreeTier && options?.allowNgrokFreeTierLoopbackBypass && isLoopback) {
     console.warn(
       "[voice-call] Twilio signature validation failed (ngrok free tier compatibility, loopback only)",
     );
@@ -384,6 +583,26 @@ export function verifyPlivoWebhook(
     publicUrl?: string;
     /** Skip verification entirely (only for development) */
     skipVerification?: boolean;
+    /**
+     * Whitelist of allowed hostnames for host header validation.
+     * Prevents host header injection attacks.
+     */
+    allowedHosts?: string[];
+    /**
+     * Explicitly trust X-Forwarded-* headers without a whitelist.
+     * WARNING: Only enable if you trust your proxy configuration.
+     * @default false
+     */
+    trustForwardingHeaders?: boolean;
+    /**
+     * List of trusted proxy IP addresses. X-Forwarded-* headers will only
+     * be trusted from these IPs.
+     */
+    trustedProxyIPs?: string[];
+    /**
+     * The remote IP address of the request (for proxy validation).
+     */
+    remoteIP?: string;
   },
 ): PlivoVerificationResult {
   if (options?.skipVerification) {
@@ -395,7 +614,12 @@ export function verifyPlivoWebhook(
   const signatureV2 = getHeader(ctx.headers, "x-plivo-signature-v2");
   const nonceV2 = getHeader(ctx.headers, "x-plivo-signature-v2-nonce");
 
-  const reconstructed = reconstructWebhookUrl(ctx);
+  const reconstructed = reconstructWebhookUrl(ctx, {
+    allowedHosts: options?.allowedHosts,
+    trustForwardingHeaders: options?.trustForwardingHeaders,
+    trustedProxyIPs: options?.trustedProxyIPs,
+    remoteIP: options?.remoteIP,
+  });
   let verificationUrl = reconstructed;
   if (options?.publicUrl) {
     try {