fix: return unsupported for email and kdf flows

src/handlers/sends-private.ts

@@ -35,6 +35,8 @@ import {
 } from './sends-shared';
 import { auditRequestMetadata, writeAuditEvent } from '../services/audit-events';
 
+const SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE = 'Send email verification is not supported by this server.';
+
 async function writeSendAudit(
   storage: StorageService,
   request: Request,
@@ -216,11 +218,17 @@ export async function handleCreateSend(request: Request, env: Env, userId: strin
   if (authTypeRaw.present && requestedAuthType === null) {
     return errorResponse('Invalid authType', 400);
   }
+  if (requestedAuthType === SendAuthType.Email) {
+    return errorResponse(SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE, 501);
+  }
 
   const normalizedEmails = normalizeEmails(emailsRaw.value);
   if (emailsRaw.present && emailsRaw.value !== null && normalizedEmails === null) {
     return errorResponse('Invalid emails', 400);
   }
+  if (normalizedEmails) {
+    return errorResponse(SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE, 501);
+  }
 
   const now = new Date().toISOString();
   const send: Send = {
@@ -340,11 +348,17 @@ export async function handleCreateFileSendV2(request: Request, env: Env, userId:
   if (authTypeRaw.present && requestedAuthType === null) {
     return errorResponse('Invalid authType', 400);
   }
+  if (requestedAuthType === SendAuthType.Email) {
+    return errorResponse(SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE, 501);
+  }
 
   const normalizedEmails = normalizeEmails(emailsRaw.value);
   if (emailsRaw.present && emailsRaw.value !== null && normalizedEmails === null) {
     return errorResponse('Invalid emails', 400);
   }
+  if (normalizedEmails) {
+    return errorResponse(SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE, 501);
+  }
 
   const now = new Date().toISOString();
   const send: Send = {
@@ -598,10 +612,11 @@ export async function handleUpdateSend(request: Request, env: Env, userId: strin
     if (parsedAuthType === null) {
       return errorResponse('Invalid authType', 400);
     }
-    send.authType = parsedAuthType;
+    if (parsedAuthType === SendAuthType.Email) {
-    if (parsedAuthType !== SendAuthType.Email) {
+      return errorResponse(SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE, 501);
-      send.emails = null;
     }
+    send.authType = parsedAuthType;
+    send.emails = null;
   }
 
   const emailsRaw = getAliasedProp(body, ['emails', 'Emails']);
@@ -610,10 +625,13 @@ export async function handleUpdateSend(request: Request, env: Env, userId: strin
     if (emailsRaw.value !== null && normalizedEmails === null) {
       return errorResponse('Invalid emails', 400);
     }
+    if (normalizedEmails) {
+      return errorResponse(SEND_EMAIL_AUTH_UNSUPPORTED_MESSAGE, 501);
+    }
     send.emails = normalizedEmails;
     if (send.emails) {
       send.authType = SendAuthType.Email;
-    } else if (send.authType === SendAuthType.Email) {
+    } else if (Number(send.authType) === SendAuthType.Email) {
       send.authType = SendAuthType.None;
     }
   }

src/handlers/sends-public.ts

@@ -368,7 +368,7 @@ export async function issueSendAccessToken(
             Object: 'error',
           },
         },
-        400
+        501
       ),
     };
   }

src/handlers/sends-shared.ts

@@ -464,7 +464,11 @@ export function sendPasswordLockedOAuthResponse(retryAfterSeconds: number): Resp
 
 export async function validatePublicSendAccess(send: Send, body: unknown): Promise<PublicSendAccessValidationResult> {
   if (hasEmailAuth(send)) {
-    return { ok: false, response: errorResponse(SEND_INACCESSIBLE_MSG, 404), reason: 'email_auth_unsupported' };
+    return {
+      ok: false,
+      response: errorResponse('Send email verification is not supported by this server.', 501),
+      reason: 'email_auth_unsupported',
+    };
   }
 
   if (!send.passwordHash) return { ok: true };

src/router-authenticated.ts

@@ -1,5 +1,5 @@
 import type { Env, User } from './types';
-import { errorResponse, jsonResponse } from './utils/response';
+import { errorResponse, jsonResponse, unsupportedResponse } from './utils/response';
 import {
   handleGetProfile,
   handleUpdateProfile,
@@ -116,6 +116,40 @@ export async function handleAuthenticatedRoute(
     }
   }
 
+  if ((path === '/api/accounts/kdf' || path === '/accounts/kdf') && (method === 'POST' || method === 'PUT')) {
+    return unsupportedResponse('KDF changes are not supported by this server.');
+  }
+
+  const mailBackedAccountPaths = new Set([
+    '/api/accounts/email-token',
+    '/accounts/email-token',
+    '/api/accounts/verify-email',
+    '/accounts/verify-email',
+    '/api/accounts/verify-email-token',
+    '/accounts/verify-email-token',
+    '/api/accounts/request-otp',
+    '/accounts/request-otp',
+    '/api/accounts/verify-otp',
+    '/accounts/verify-otp',
+  ]);
+  if (mailBackedAccountPaths.has(path) && (method === 'POST' || method === 'PUT')) {
+    return unsupportedResponse('Email delivery is not supported by this server.');
+  }
+
+  const emailTwoFactorPaths = new Set([
+    '/api/two-factor/get-email',
+    '/two-factor/get-email',
+    '/api/two-factor/send-email',
+    '/two-factor/send-email',
+    '/api/two-factor/send-email-login',
+    '/two-factor/send-email-login',
+    '/api/two-factor/email',
+    '/two-factor/email',
+  ]);
+  if (emailTwoFactorPaths.has(path) && (method === 'POST' || method === 'PUT' || method === 'DELETE')) {
+    return unsupportedResponse('Email two-step login is not supported by this server.');
+  }
+
   if (path === '/api/accounts/profile') {
     if (method === 'GET') return handleGetProfile(request, env, userId);
     if (method === 'PUT') return handleUpdateProfile(request, env, userId);

src/router-public.ts

@@ -28,7 +28,7 @@ import {
 } from './handlers/notifications';
 import { handlePublicUploadSendFile } from './handlers/sends';
 import { isSafeWebsiteIconContentType } from './utils/content-type';
-import { jsonResponse } from './utils/response';
+import { jsonResponse, unsupportedResponse } from './utils/response';
 import { StorageService } from './services/storage';
 import type { Env } from './types';
 
@@ -470,6 +470,29 @@ export async function handlePublicRoute(
     return handleRecoverTwoFactor(request, env);
   }
 
+  const publicMailBackedPaths = new Set([
+    '/api/accounts/resend-new-device-otp',
+    '/accounts/resend-new-device-otp',
+    '/api/accounts/register/send-verification-email',
+    '/accounts/register/send-verification-email',
+    '/identity/accounts/register/send-verification-email',
+    '/api/accounts/register/verification-email-clicked',
+    '/accounts/register/verification-email-clicked',
+    '/identity/accounts/register/verification-email-clicked',
+    '/api/accounts/register/finish',
+    '/accounts/register/finish',
+    '/identity/accounts/register/finish',
+    '/api/accounts/verify-email-token',
+    '/accounts/verify-email-token',
+    '/api/two-factor/send-email-login',
+    '/two-factor/send-email-login',
+  ]);
+  if (publicMailBackedPaths.has(path) && method === 'POST') {
+    const blocked = await enforcePublicRateLimit('public-sensitive', LIMITS.rateLimit.sensitivePublicRequestsPerMinute);
+    if (blocked) return blocked;
+    return unsupportedResponse('Email delivery is not supported by this server.');
+  }
+
   if (path === '/api/accounts/password-hint' && method === 'POST') {
     const blocked = await enforcePublicRateLimit('public-sensitive', LIMITS.rateLimit.sensitivePublicRequestsPerMinute);
     if (blocked) return blocked;

src/utils/response.ts

@@ -136,6 +136,10 @@ export function errorResponse(message: string, status: number = 400): Response {
   );
 }
 
+export function unsupportedResponse(message: string = 'This feature is not supported by this server.'): Response {
+  return errorResponse(message, 501);
+}
+
 // Identity endpoint error response (for /identity/connect/token)
 export function identityErrorResponse(message: string, error: string = 'invalid_grant', status: number = 400): Response {
   return jsonResponse(