fix: harden tailscale serve auth

steipete · steipete · commit fd9be79be194 · 2026-01-26T12:49:19.000Z
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -35,6 +35,7 @@ Status: unreleased.
 - macOS: keep custom SSH usernames in remote target. (#2046) Thanks @algal.
 
 ### Fixes
+- Security: harden Tailscale Serve auth by validating identity via local tailscaled before trusting headers.
 - Web UI: improve WebChat image paste previews and allow image-only sends. (#1925) Thanks @smartprogrammer93.
 
 ## 2026.1.24-3
diff --git a/docs/gateway/configuration.md b/docs/gateway/configuration.md
@@ -2878,10 +2878,11 @@ Auth and Tailscale:
 - `gateway.auth.password` can be set here, or via `CLAWDBOT_GATEWAY_PASSWORD` (recommended).
 - `gateway.auth.allowTailscale` allows Tailscale Serve identity headers
   (`tailscale-user-login`) to satisfy auth when the request arrives on loopback
-  with `x-forwarded-for`, `x-forwarded-proto`, and `x-forwarded-host`. When
-  `true`, Serve requests do not need a token/password; set `false` to require
-  explicit credentials. Defaults to `true` when `tailscale.mode = "serve"` and
-  auth mode is not `password`.
+  with `x-forwarded-for`, `x-forwarded-proto`, and `x-forwarded-host`. Clawdbot
+  verifies the identity by resolving the `x-forwarded-for` address via
+  `tailscale whois` before accepting it. When `true`, Serve requests do not need
+  a token/password; set `false` to require explicit credentials. Defaults to
+  `true` when `tailscale.mode = "serve"` and auth mode is not `password`.
 - `gateway.tailscale.mode: "serve"` uses Tailscale Serve (tailnet only, loopback bind).
 - `gateway.tailscale.mode: "funnel"` exposes the dashboard publicly; requires auth.
 - `gateway.tailscale.resetOnExit` resets Serve/Funnel config on shutdown.
diff --git a/docs/gateway/security.md b/docs/gateway/security.md
@@ -333,9 +333,11 @@ Rotation checklist (token/password):
 
 When `gateway.auth.allowTailscale` is `true` (default for Serve), Clawdbot
 accepts Tailscale Serve identity headers (`tailscale-user-login`) as
-authentication. This only triggers for requests that hit loopback and include
-`x-forwarded-for`, `x-forwarded-proto`, and `x-forwarded-host` as injected by
-Tailscale.
+authentication. Clawdbot verifies the identity by resolving the
+`x-forwarded-for` address through the local Tailscale daemon (`tailscale whois`)
+and matching it to the header. This only triggers for requests that hit loopback
+and include `x-forwarded-for`, `x-forwarded-proto`, and `x-forwarded-host` as
+injected by Tailscale.
 
 **Security rule:** do not forward these headers from your own reverse proxy. If
 you terminate TLS or proxy in front of the gateway, disable
diff --git a/docs/gateway/tailscale.md b/docs/gateway/tailscale.md
@@ -25,9 +25,12 @@ Set `gateway.auth.mode` to control the handshake:
 
 When `tailscale.mode = "serve"` and `gateway.auth.allowTailscale` is `true`,
 valid Serve proxy requests can authenticate via Tailscale identity headers
-(`tailscale-user-login`) without supplying a token/password. Clawdbot only
-treats a request as Serve when it arrives from loopback with Tailscale’s
-`x-forwarded-for`, `x-forwarded-proto`, and `x-forwarded-host` headers.
+(`tailscale-user-login`) without supplying a token/password. Clawdbot verifies
+the identity by resolving the `x-forwarded-for` address via the local Tailscale
+daemon (`tailscale whois`) and matching it to the header before accepting it.
+Clawdbot only treats a request as Serve when it arrives from loopback with
+Tailscale’s `x-forwarded-for`, `x-forwarded-proto`, and `x-forwarded-host`
+headers.
 To require explicit credentials, set `gateway.auth.allowTailscale: false` or
 force `gateway.auth.mode: "password"`.
 
diff --git a/docs/web/control-ui.md b/docs/web/control-ui.md
@@ -70,10 +70,11 @@ Open:
 
 By default, Serve requests can authenticate via Tailscale identity headers
 (`tailscale-user-login`) when `gateway.auth.allowTailscale` is `true`. Clawdbot
-only accepts these when the request hits loopback with Tailscale’s
-`x-forwarded-*` headers. Set `gateway.auth.allowTailscale: false` (or force
-`gateway.auth.mode: "password"`) if you want to require a token/password even
-for Serve traffic.
+verifies the identity by resolving the `x-forwarded-for` address with
+`tailscale whois` and matching it to the header, and only accepts these when the
+request hits loopback with Tailscale’s `x-forwarded-*` headers. Set
+`gateway.auth.allowTailscale: false` (or force `gateway.auth.mode: "password"`)
+if you want to require a token/password even for Serve traffic.
 
 ### Bind to tailnet + token
 
diff --git a/src/gateway/auth.test.ts b/src/gateway/auth.test.ts
@@ -125,6 +125,7 @@ describe("gateway auth", () => {
     const res = await authorizeGatewayConnect({
       auth: { mode: "token", token: "secret", allowTailscale: true },
       connectAuth: null,
+      tailscaleWhois: async () => ({ login: "peter", name: "Peter" }),
       req: {
         socket: { remoteAddress: "127.0.0.1" },
         headers: {
@@ -143,6 +144,28 @@ describe("gateway auth", () => {
     expect(res.user).toBe("peter");
   });
 
+  it("rejects mismatched tailscale identity when required", async () => {
+    const res = await authorizeGatewayConnect({
+      auth: { mode: "none", allowTailscale: true },
+      connectAuth: null,
+      tailscaleWhois: async () => ({ login: "alice@example.com", name: "Alice" }),
+      req: {
+        socket: { remoteAddress: "127.0.0.1" },
+        headers: {
+          host: "gateway.local",
+          "x-forwarded-for": "100.64.0.1",
+          "x-forwarded-proto": "https",
+          "x-forwarded-host": "ai-hub.bone-egret.ts.net",
+          "tailscale-user-login": "peter@example.com",
+          "tailscale-user-name": "Peter",
+        },
+      } as never,
+    });
+
+    expect(res.ok).toBe(false);
+    expect(res.reason).toBe("tailscale_user_mismatch");
+  });
+
   it("treats trusted proxy loopback clients as direct", async () => {
     const res = await authorizeGatewayConnect({
       auth: { mode: "none", allowTailscale: true },
diff --git a/src/gateway/auth.ts b/src/gateway/auth.ts
@@ -1,7 +1,8 @@
 import { timingSafeEqual } from "node:crypto";
 import type { IncomingMessage } from "node:http";
 import type { GatewayAuthConfig, GatewayTailscaleMode } from "../config/config.js";
-import { isTrustedProxyAddress, resolveGatewayClientIp } from "./net.js";
+import { readTailscaleWhoisIdentity, type TailscaleWhoisIdentity } from "../infra/tailscale.js";
+import { isTrustedProxyAddress, parseForwardedForClientIp, resolveGatewayClientIp } from "./net.js";
 export type ResolvedGatewayAuthMode = "none" | "token" | "password";
 
 export type ResolvedGatewayAuth = {
@@ -29,11 +30,17 @@ type TailscaleUser = {
   profilePic?: string;
 };
 
+type TailscaleWhoisLookup = (ip: string) => Promise<TailscaleWhoisIdentity | null>;
+
 function safeEqual(a: string, b: string): boolean {
   if (a.length !== b.length) return false;
   return timingSafeEqual(Buffer.from(a), Buffer.from(b));
 }
 
+function normalizeLogin(login: string): string {
+  return login.trim().toLowerCase();
+}
+
 function isLoopbackAddress(ip: string | undefined): boolean {
   if (!ip) return false;
   if (ip === "127.0.0.1") return true;
@@ -58,6 +65,12 @@ function headerValue(value: string | string[] | undefined): string | undefined {
   return Array.isArray(value) ? value[0] : value;
 }
 
+function resolveTailscaleClientIp(req?: IncomingMessage): string | undefined {
+  if (!req) return undefined;
+  const forwardedFor = headerValue(req.headers?.["x-forwarded-for"]);
+  return forwardedFor ? parseForwardedForClientIp(forwardedFor) : undefined;
+}
+
 function resolveRequestClientIp(
   req?: IncomingMessage,
   trustedProxies?: string[],
@@ -118,6 +131,39 @@ function isTailscaleProxyRequest(req?: IncomingMessage): boolean {
   return isLoopbackAddress(req.socket?.remoteAddress) && hasTailscaleProxyHeaders(req);
 }
 
+async function resolveVerifiedTailscaleUser(params: {
+  req?: IncomingMessage;
+  tailscaleWhois: TailscaleWhoisLookup;
+}): Promise<{ ok: true; user: TailscaleUser } | { ok: false; reason: string }> {
+  const { req, tailscaleWhois } = params;
+  const tailscaleUser = getTailscaleUser(req);
+  if (!tailscaleUser) {
+    return { ok: false, reason: "tailscale_user_missing" };
+  }
+  if (!isTailscaleProxyRequest(req)) {
+    return { ok: false, reason: "tailscale_proxy_missing" };
+  }
+  const clientIp = resolveTailscaleClientIp(req);
+  if (!clientIp) {
+    return { ok: false, reason: "tailscale_whois_failed" };
+  }
+  const whois = await tailscaleWhois(clientIp);
+  if (!whois?.login) {
+    return { ok: false, reason: "tailscale_whois_failed" };
+  }
+  if (normalizeLogin(whois.login) !== normalizeLogin(tailscaleUser.login)) {
+    return { ok: false, reason: "tailscale_user_mismatch" };
+  }
+  return {
+    ok: true,
+    user: {
+      login: whois.login,
+      name: whois.name ?? tailscaleUser.name,
+      profilePic: tailscaleUser.profilePic,
+    },
+  };
+}
+
 export function resolveGatewayAuth(params: {
   authConfig?: GatewayAuthConfig | null;
   env?: NodeJS.ProcessEnv;
@@ -155,29 +201,26 @@ export async function authorizeGatewayConnect(params: {
   connectAuth?: ConnectAuth | null;
   req?: IncomingMessage;
   trustedProxies?: string[];
+  tailscaleWhois?: TailscaleWhoisLookup;
 }): Promise<GatewayAuthResult> {
   const { auth, connectAuth, req, trustedProxies } = params;
+  const tailscaleWhois = params.tailscaleWhois ?? readTailscaleWhoisIdentity;
   const localDirect = isLocalDirectRequest(req, trustedProxies);
 
   if (auth.allowTailscale && !localDirect) {
-    const tailscaleUser = getTailscaleUser(req);
-    const tailscaleProxy = isTailscaleProxyRequest(req);
-
-    if (tailscaleUser && tailscaleProxy) {
+    const tailscaleCheck = await resolveVerifiedTailscaleUser({
+      req,
+      tailscaleWhois,
+    });
+    if (tailscaleCheck.ok) {
       return {
         ok: true,
         method: "tailscale",
-        user: tailscaleUser.login,
+        user: tailscaleCheck.user.login,
       };
     }
-
     if (auth.mode === "none") {
-      if (!tailscaleUser) {
-        return { ok: false, reason: "tailscale_user_missing" };
-      }
-      if (!tailscaleProxy) {
-        return { ok: false, reason: "tailscale_proxy_missing" };
-      }
+      return { ok: false, reason: tailscaleCheck.reason };
     }
   }
 
@@ -192,7 +235,7 @@ export async function authorizeGatewayConnect(params: {
     if (!connectAuth?.token) {
       return { ok: false, reason: "token_missing" };
     }
-    if (connectAuth.token !== auth.token) {
+    if (!safeEqual(connectAuth.token, auth.token)) {
       return { ok: false, reason: "token_mismatch" };
     }
     return { ok: true, method: "token" };
diff --git a/src/gateway/net.ts b/src/gateway/net.ts
@@ -36,7 +36,7 @@ function stripOptionalPort(ip: string): string {
   return ip;
 }
 
-function parseForwardedForClientIp(forwardedFor?: string): string | undefined {
+export function parseForwardedForClientIp(forwardedFor?: string): string | undefined {
   const raw = forwardedFor?.split(",")[0]?.trim();
   if (!raw) return undefined;
   return normalizeIp(stripOptionalPort(raw));
diff --git a/src/gateway/server/ws-connection/message-handler.ts b/src/gateway/server/ws-connection/message-handler.ts
@@ -100,6 +100,10 @@ function formatGatewayAuthFailureMessage(params: {
       return "unauthorized: tailscale identity missing (use Tailscale Serve auth or gateway token/password)";
     case "tailscale_proxy_missing":
       return "unauthorized: tailscale proxy headers missing (use Tailscale Serve or gateway token/password)";
+    case "tailscale_whois_failed":
+      return "unauthorized: tailscale identity check failed (use Tailscale Serve auth or gateway token/password)";
+    case "tailscale_user_mismatch":
+      return "unauthorized: tailscale identity mismatch (use Tailscale Serve auth or gateway token/password)";
     default:
       break;
   }
diff --git a/src/infra/tailscale.ts b/src/infra/tailscale.ts
@@ -213,6 +213,18 @@ type ExecErrorDetails = {
   code?: unknown;
 };
 
+export type TailscaleWhoisIdentity = {
+  login: string;
+  name?: string;
+};
+
+type TailscaleWhoisCacheEntry = {
+  value: TailscaleWhoisIdentity | null;
+  expiresAt: number;
+};
+
+const whoisCache = new Map<string, TailscaleWhoisCacheEntry>();
+
 function extractExecErrorText(err: unknown) {
   const errOutput = err as ExecErrorDetails;
   const stdout = typeof errOutput.stdout === "string" ? errOutput.stdout : "";
@@ -381,3 +393,73 @@ export async function disableTailscaleFunnel(exec: typeof runExec = runExec) {
     timeoutMs: 15_000,
   });
 }
+
+function getString(value: unknown): string | undefined {
+  return typeof value === "string" && value.trim() ? value.trim() : undefined;
+}
+
+function readRecord(value: unknown): Record<string, unknown> | null {
+  return value && typeof value === "object" ? (value as Record<string, unknown>) : null;
+}
+
+function parseWhoisIdentity(payload: Record<string, unknown>): TailscaleWhoisIdentity | null {
+  const userProfile =
+    readRecord(payload.UserProfile) ?? readRecord(payload.userProfile) ?? readRecord(payload.User);
+  const login =
+    getString(userProfile?.LoginName) ??
+    getString(userProfile?.Login) ??
+    getString(userProfile?.login) ??
+    getString(payload.LoginName) ??
+    getString(payload.login);
+  if (!login) return null;
+  const name =
+    getString(userProfile?.DisplayName) ??
+    getString(userProfile?.Name) ??
+    getString(userProfile?.displayName) ??
+    getString(payload.DisplayName) ??
+    getString(payload.name);
+  return { login, name };
+}
+
+function readCachedWhois(ip: string, now: number): TailscaleWhoisIdentity | null | undefined {
+  const cached = whoisCache.get(ip);
+  if (!cached) return undefined;
+  if (cached.expiresAt <= now) {
+    whoisCache.delete(ip);
+    return undefined;
+  }
+  return cached.value;
+}
+
+function writeCachedWhois(ip: string, value: TailscaleWhoisIdentity | null, ttlMs: number) {
+  whoisCache.set(ip, { value, expiresAt: Date.now() + ttlMs });
+}
+
+export async function readTailscaleWhoisIdentity(
+  ip: string,
+  exec: typeof runExec = runExec,
+  opts?: { timeoutMs?: number; cacheTtlMs?: number; errorTtlMs?: number },
+): Promise<TailscaleWhoisIdentity | null> {
+  const normalized = ip.trim();
+  if (!normalized) return null;
+  const now = Date.now();
+  const cached = readCachedWhois(normalized, now);
+  if (cached !== undefined) return cached;
+
+  const cacheTtlMs = opts?.cacheTtlMs ?? 60_000;
+  const errorTtlMs = opts?.errorTtlMs ?? 5_000;
+  try {
+    const tailscaleBin = await getTailscaleBinary();
+    const { stdout } = await exec(tailscaleBin, ["whois", "--json", normalized], {
+      timeoutMs: opts?.timeoutMs ?? 5_000,
+      maxBuffer: 200_000,
+    });
+    const parsed = stdout ? parsePossiblyNoisyJsonObject(stdout) : {};
+    const identity = parseWhoisIdentity(parsed);
+    writeCachedWhois(normalized, identity, cacheTtlMs);
+    return identity;
+  } catch {
+    writeCachedWhois(normalized, null, errorTtlMs);
+    return null;
+  }
+}

Original file line number	Diff line number	Diff line change
`@@ -36,7 +36,7 @@ function stripOptionalPort(ip: string): string {`
`36`	`36`	`return ip;`
`37`	`37`	`}`
`38`	`38`
`39`		`-function parseForwardedForClientIp(forwardedFor?: string): string \| undefined {`
	`39`	`+export function parseForwardedForClientIp(forwardedFor?: string): string \| undefined {`
`40`	`40`	`const raw = forwardedFor?.split(",")[0]?.trim();`
`41`	`41`	`if (!raw) return undefined;`
`42`	`42`	`return normalizeIp(stripOptionalPort(raw));`