fix(security): harden auth and request limits

src/handlers/accounts.ts

@@ -42,6 +42,9 @@ function looksLikeEncString(value: string): boolean {
  */
 function validateKdfParams(kdfType: number | undefined, kdfIterations: number | undefined, kdfMemory?: number | undefined, kdfParallelism?: number | undefined): string | null {
   const type = kdfType ?? 0;
+  if (type !== 0 && type !== 1) {
+    return 'KDF type must be PBKDF2-SHA256 or Argon2id';
+  }
   if (type === 0) {
     // PBKDF2-SHA256: minimum 100 000 iterations
     if (typeof kdfIterations === 'number' && kdfIterations < 100_000) {
@@ -448,7 +451,7 @@ export async function handleGetPasswordHint(request: Request, env: Env): Promise
   }
 
   const rateLimit = new RateLimitService(env.DB);
-  const minuteBudget = await rateLimit.consumeBudgetWithWindow(
+  const minuteBudget = await rateLimit.consumeStrictBudgetWithWindow(
     `${clientIdentifier}:password-hint`,
     LIMITS.rateLimit.passwordHintRequestsPerMinute,
     60
@@ -470,7 +473,7 @@ export async function handleGetPasswordHint(request: Request, env: Env): Promise
     );
   }
 
-  const hourlyBudget = await rateLimit.consumeBudgetWithWindow(
+  const hourlyBudget = await rateLimit.consumeStrictBudgetWithWindow(
     `${clientIdentifier}:password-hint-hour`,
     LIMITS.rateLimit.passwordHintRequestsPerHour,
     60 * 60
@@ -734,6 +737,11 @@ export async function handleChangePassword(request: Request, env: Env, userId: s
   const nextKdfParallelism = body.kdfParallelism ?? readNestedNumber(body, ['unlockData', 'kdf', 'parallelism']);
   const kdfErr = validateKdfParams(nextKdf, nextKdfIterations, nextKdfMemory, nextKdfParallelism);
   if (kdfErr) return errorResponse(kdfErr, 400);
+  const shouldUpdateHint = typeof body.masterPasswordHint === 'string' || body.masterPasswordHint === null;
+  const nextMasterPasswordHint = shouldUpdateHint ? normalizeMasterPasswordHint(body.masterPasswordHint) : undefined;
+  if (nextMasterPasswordHint && nextMasterPasswordHint.length > 120) {
+    return errorResponse('masterPasswordHint must be 120 characters or fewer', 400);
+  }
 
   user.masterPasswordHash = await auth.hashPasswordServer(newMasterPasswordHash, user.email);
   if (nextKey) user.key = nextKey;
@@ -743,8 +751,8 @@ export async function handleChangePassword(request: Request, env: Env, userId: s
   if (typeof nextKdfIterations === 'number') user.kdfIterations = nextKdfIterations;
   if (typeof nextKdfMemory === 'number') user.kdfMemory = nextKdfMemory;
   if (typeof nextKdfParallelism === 'number') user.kdfParallelism = nextKdfParallelism;
-  if (typeof body.masterPasswordHint === 'string' || body.masterPasswordHint === null) {
-    user.masterPasswordHint = body.masterPasswordHint;
+  if (shouldUpdateHint) {
+    user.masterPasswordHint = nextMasterPasswordHint ?? null;
   }
   user.securityStamp = generateUUID();
   user.updatedAt = new Date().toISOString();

src/handlers/attachments.ts

@@ -124,6 +124,10 @@ async function processAttachmentUpload(
   }
 
   const path = getAttachmentObjectKey(cipherId, attachment.id);
+  if (await getBlobObject(env, path)) {
+    return errorResponse('Attachment file has already been uploaded', 409);
+  }
+
   try {
     await putBlobObject(env, path, upload.body, {
       size: upload.size,

src/handlers/auth-requests.ts

@@ -5,6 +5,8 @@ import { readAuthRequestDeviceInfo, readActingDeviceIdentifier } from '../utils/
 import { errorResponse, jsonResponse } from '../utils/response';
 import { isAuthRequestExpired } from '../services/storage-auth-request-repo';
 import { notifyAuthRequestResponse, notifyUserAuthRequest } from '../durable/notifications-hub';
+import { RateLimitService, getClientIdentifier } from '../services/ratelimit';
+import { LIMITS } from '../config/limits';
 
 const AUTH_REQUEST_TYPE_AUTHENTICATE_AND_UNLOCK = 0;
 const AUTH_REQUEST_TYPE_UNLOCK = 1;
@@ -131,6 +133,30 @@ async function readJsonBody(request: Request): Promise<Record<string, any> | nul
   }
 }
 
+async function enforceAuthRequestCreateRateLimit(
+  request: Request,
+  env: Env,
+  email: string,
+  deviceIdentifier: string
+): Promise<Response | null> {
+  const clientIdentifier = getClientIdentifier(request);
+  if (!clientIdentifier) return errorResponse('Client IP is required', 403);
+
+  const rateLimit = new RateLimitService(env.DB);
+  const limit = LIMITS.rateLimit.authRequestRequestsPerMinute;
+  const encodedEmail = encodeURIComponent(email || 'missing');
+  const encodedDevice = encodeURIComponent(deviceIdentifier || 'missing');
+  const budgets = await Promise.all([
+    rateLimit.consumeStrictBudget(`auth-request:ip:${clientIdentifier}`, limit),
+    rateLimit.consumeStrictBudget(`auth-request:email:${encodedEmail}`, limit),
+    rateLimit.consumeStrictBudget(`auth-request:device:${encodedDevice}`, limit),
+  ]);
+  const blocked = budgets.find((budget) => !budget.allowed);
+  if (!blocked) return null;
+
+  return errorResponse('Too many authentication requests. Try again later.', 429);
+}
+
 function readBodyValue(body: Record<string, any>, names: string[]): unknown {
   for (const name of names) {
     if (body[name] !== undefined) return body[name];
@@ -164,6 +190,8 @@ export async function handleCreateAuthRequest(request: Request, env: Env): Promi
   if (!email || !publicKey || !accessCode || !deviceInfo.deviceIdentifier) {
     return errorResponse('Email, public key, device identifier, and access code are required.', 400);
   }
+  const rateLimitResponse = await enforceAuthRequestCreateRateLimit(request, env, email, deviceInfo.deviceIdentifier);
+  if (rateLimitResponse) return rateLimitResponse;
   if (!isSupportedAuthRequestType(type) || type === AUTH_REQUEST_TYPE_ADMIN_APPROVAL) {
     return errorResponse('Invalid auth request type.', 400);
   }