feat: implement direct file upload for sends with JWT token validation

- Added `processSendFileUpload` function to handle file uploads for sends.
- Integrated JWT token creation and verification for secure file uploads.
- Updated `handleCreateFileSendV2` and `handleGetSendFileUpload` to use new upload URL generation.
- Refactored upload handling in `handleUploadSendFile` and `handlePublicUploadSendFile` to utilize the new upload process.
- Introduced `uploadDirectEncryptedPayload` for handling direct uploads with progress tracking.
- Enhanced API routes to support both POST and PUT methods for attachment uploads.
- Added localization strings for upload progress messages.
- Created utility functions for direct upload URL building and payload parsing.

src/handlers/attachments.ts

@@ -2,8 +2,14 @@ import { Env, Attachment, DEFAULT_DEV_SECRET } from '../types';
 import { notifyUserVaultSync } from '../durable/notifications-hub';
 import { StorageService } from '../services/storage';
 import { jsonResponse, errorResponse } from '../utils/response';
+import { buildDirectUploadUrl, getSafeJwtSecret, parseDirectUploadPayload } from '../utils/direct-upload';
 import { generateUUID } from '../utils/uuid';
-import { createFileDownloadToken, verifyFileDownloadToken } from '../utils/jwt';
+import {
+  createAttachmentUploadToken,
+  createFileDownloadToken,
+  verifyAttachmentUploadToken,
+  verifyFileDownloadToken,
+} from '../utils/jwt';
 import { cipherToResponse, shouldOmitPasskeysForResponse } from './ciphers';
 import { LIMITS } from '../config/limits';
 import { readActingDeviceIdentifier } from '../utils/device';
@@ -32,6 +38,55 @@ function formatSize(bytes: number): string {
   return `${(bytes / (1024 * 1024 * 1024)).toFixed(2)} GB`;
 }
 
+async function processAttachmentUpload(
+  request: Request,
+  env: Env,
+  attachment: Attachment,
+  cipherId: string
+): Promise<Response> {
+  const storage = new StorageService(env.DB);
+  const maxFileSize = getBlobStorageMaxBytes(env, LIMITS.attachment.maxFileSizeBytes);
+  const upload = await parseDirectUploadPayload(request, {
+    expectedSize: Number(attachment.size) || 0,
+    maxFileSize,
+    tooLargeMessage: `File too large. Maximum size is ${Math.floor(maxFileSize / (1024 * 1024))}MB`,
+  });
+  if (upload instanceof Response) {
+    return upload;
+  }
+
+  const path = getAttachmentObjectKey(cipherId, attachment.id);
+  try {
+    await putBlobObject(env, path, upload.body, {
+      size: upload.size,
+      contentType: upload.contentType,
+      customMetadata: {
+        cipherId,
+        attachmentId: attachment.id,
+      },
+    });
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    if (message.includes('KV object too large')) {
+      return errorResponse(`File too large. Maximum size is ${Math.floor(maxFileSize / (1024 * 1024))}MB`, 413);
+    }
+    return errorResponse('Attachment storage is not configured', 500);
+  }
+
+  if (upload.size !== attachment.size) {
+    attachment.size = upload.size;
+    attachment.sizeName = formatSize(upload.size);
+    await storage.saveAttachment(attachment);
+  }
+
+  const revisionInfo = await storage.updateCipherRevisionDate(cipherId);
+  if (revisionInfo) {
+    await notifyVaultSyncForRequest(request, env, revisionInfo.userId, revisionInfo.revisionDate);
+  }
+
+  return new Response(null, { status: 201 });
+}
+
 // POST /api/ciphers/{cipherId}/attachment/v2
 // Creates attachment metadata and returns upload URL
 export async function handleCreateAttachment(
@@ -92,12 +147,17 @@ export async function handleCreateAttachment(
   // Get updated cipher for response
   const updatedCipher = await storage.getCipher(cipherId);
   const attachments = await storage.getAttachmentsByCipher(cipherId);
+  const jwtSecret = getSafeJwtSecret(env);
+  if (!jwtSecret) {
+    return errorResponse('Server configuration error', 500);
+  }
+  const uploadToken = await createAttachmentUploadToken(userId, cipherId, attachmentId, jwtSecret);
 
   return jsonResponse({
     object: 'attachment-fileUpload',
     attachmentId: attachmentId,
-    url: `/api/ciphers/${cipherId}/attachment/${attachmentId}`,
-    fileUploadType: 0, // Direct upload
+    url: buildDirectUploadUrl(request, `/api/ciphers/${cipherId}/attachment/${attachmentId}`, uploadToken),
+    fileUploadType: 1,
     cipherResponse: cipherToResponse(updatedCipher!, attachments, {
       omitFido2Credentials: shouldOmitPasskeysForResponse(request),
     }),
@@ -114,7 +174,6 @@ export async function handleUploadAttachment(
   attachmentId: string
 ): Promise<Response> {
   const storage = new StorageService(env.DB);
-  const maxFileSize = getBlobStorageMaxBytes(env, LIMITS.attachment.maxFileSizeBytes);
 
   // Verify cipher exists and belongs to user
   const cipher = await storage.getCipher(cipherId);
@@ -128,63 +187,45 @@ export async function handleUploadAttachment(
     return errorResponse('Attachment not found', 404);
   }
 
-  // Check content-length header for size limit
-  const contentLength = request.headers.get('content-length');
-  if (contentLength && parseInt(contentLength) > maxFileSize) {
-    return errorResponse(`File too large. Maximum size is ${Math.floor(maxFileSize / (1024 * 1024))}MB`, 413);
+  return processAttachmentUpload(request, env, attachment, cipherId);
+}
+
+export async function handlePublicUploadAttachment(
+  request: Request,
+  env: Env,
+  cipherId: string,
+  attachmentId: string
+): Promise<Response> {
+  const jwtSecret = getSafeJwtSecret(env);
+  if (!jwtSecret) {
+    return errorResponse('Server configuration error', 500);
   }
 
-  // Get the file from multipart form data
-  const contentType = request.headers.get('content-type') || '';
-  if (!contentType.includes('multipart/form-data')) {
-    return errorResponse('Content-Type must be multipart/form-data', 400);
+  const token = new URL(request.url).searchParams.get('token');
+  if (!token) {
+    return errorResponse('Token required', 401);
   }
 
-  const formData = await request.formData();
-  const file = formData.get('data') as File | null;
-
-  if (!file) {
-    return errorResponse('No file uploaded', 400);
+  const claims = await verifyAttachmentUploadToken(token, jwtSecret);
+  if (!claims) {
+    return errorResponse('Invalid or expired token', 401);
+  }
+  if (claims.cipherId !== cipherId || claims.attachmentId !== attachmentId) {
+    return errorResponse('Token mismatch', 401);
   }
 
-  // Check actual file size
-  if (file.size > maxFileSize) {
-    return errorResponse(`File too large. Maximum size is ${Math.floor(maxFileSize / (1024 * 1024))}MB`, 413);
+  const storage = new StorageService(env.DB);
+  const cipher = await storage.getCipher(cipherId);
+  if (!cipher || cipher.userId !== claims.userId) {
+    return errorResponse('Cipher not found', 404);
   }
 
-  const path = getAttachmentObjectKey(cipherId, attachmentId);
-  try {
-    await putBlobObject(env, path, file.stream(), {
-      size: file.size,
-      contentType: 'application/octet-stream',
-      customMetadata: {
-        cipherId,
-        attachmentId,
-      },
-    });
-  } catch (error) {
-    const message = error instanceof Error ? error.message : String(error);
-    if (message.includes('KV object too large')) {
-      return errorResponse(`File too large. Maximum size is ${Math.floor(maxFileSize / (1024 * 1024))}MB`, 413);
-    }
-    return errorResponse('Attachment storage is not configured', 500);
+  const attachment = await storage.getAttachment(attachmentId);
+  if (!attachment || attachment.cipherId !== cipherId) {
+    return errorResponse('Attachment not found', 404);
   }
 
-  // Update attachment size if different
-  const actualSize = file.size;
-  if (actualSize !== attachment.size) {
-    attachment.size = actualSize;
-    attachment.sizeName = formatSize(actualSize);
-    await storage.saveAttachment(attachment);
-  }
-
-  // Update cipher revision date
-  const revisionInfo = await storage.updateCipherRevisionDate(cipherId);
-  if (revisionInfo) {
-    await notifyVaultSyncForRequest(request, env, revisionInfo.userId, revisionInfo.revisionDate);
-  }
-
-  return new Response(null, { status: 200 });
+  return processAttachmentUpload(request, env, attachment, cipherId);
 }
 
 // GET /api/ciphers/{cipherId}/attachment/{attachmentId}

src/handlers/sends-private.ts

@@ -1,6 +1,7 @@
 import { Env, Send, SendAuthType, SendType } from '../types';
 import { StorageService } from '../services/storage';
 import { jsonResponse, errorResponse } from '../utils/response';
+import { buildDirectUploadUrl, getSafeJwtSecret, parseDirectUploadPayload } from '../utils/direct-upload';
 import { generateUUID } from '../utils/uuid';
 import { parsePagination, encodeContinuationToken } from '../utils/pagination';
 import { LIMITS } from '../config/limits';
@@ -10,6 +11,7 @@ import {
   putBlobObject,
   deleteBlobObject,
 } from '../services/blob-store';
+import { createSendFileUploadToken, verifySendFileUploadToken } from '../utils/jwt';
 import {
   formatSize,
   getAliasedProp,
@@ -28,6 +30,57 @@ import {
   validateDeletionDate,
 } from './sends-shared';
 
+async function processSendFileUpload(
+  request: Request,
+  env: Env,
+  send: Send,
+  fileId: string
+): Promise<Response> {
+  const maxFileSize = getBlobStorageMaxBytes(env, LIMITS.send.maxFileSizeBytes);
+  const sendData = parseStoredSendData(send);
+  const expectedFileId = typeof sendData.id === 'string' ? sendData.id : null;
+  if (!expectedFileId || expectedFileId !== fileId) {
+    return errorResponse('Send file does not match send data.', 400);
+  }
+
+  const expectedFileName = typeof sendData.fileName === 'string' ? sendData.fileName : null;
+  const expectedSize = parseInteger(sendData.size);
+  const upload = await parseDirectUploadPayload(request, {
+    expectedSize,
+    expectedFileName,
+    maxFileSize,
+    tooLargeMessage: 'Send storage limit exceeded with this file',
+    sizeMismatchMessage: 'Send file size does not match.',
+    fileNameMismatchMessage: 'Send file name does not match.',
+  });
+  if (upload instanceof Response) {
+    return upload;
+  }
+
+  try {
+    await putBlobObject(env, getSendFileObjectKey(send.id, fileId), upload.body, {
+      size: upload.size,
+      contentType: upload.contentType,
+      customMetadata: {
+        sendId: send.id,
+        fileId,
+      },
+    });
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    if (message.includes('KV object too large')) {
+      return errorResponse('Send storage limit exceeded with this file', 413);
+    }
+    return errorResponse('Attachment storage is not configured', 500);
+  }
+
+  const storage = new StorageService(env.DB);
+  const revisionDate = await storage.updateRevisionDate(send.userId);
+  await notifyVaultSyncForRequest(request, env, send.userId, revisionDate);
+
+  return new Response(null, { status: 201 });
+}
+
 export async function handleGetSends(request: Request, env: Env, userId: string): Promise<Response> {
   const storage = new StorageService(env.DB);
   const url = new URL(request.url);
@@ -296,11 +349,16 @@ export async function handleCreateFileSendV2(request: Request, env: Env, userId:
   await storage.saveSend(send);
   const revisionDate = await storage.updateRevisionDate(userId);
   await notifyVaultSyncForRequest(request, env, userId, revisionDate);
+  const jwtSecret = getSafeJwtSecret(env);
+  if (!jwtSecret) {
+    return errorResponse('Server configuration error', 500);
+  }
+  const uploadToken = await createSendFileUploadToken(userId, send.id, fileId, jwtSecret);
 
   return jsonResponse({
-    fileUploadType: 0,
+    fileUploadType: 1,
     object: 'send-fileUpload',
-    url: `/api/sends/${send.id}/file/${fileId}`,
+    url: buildDirectUploadUrl(request, `/api/sends/${send.id}/file/${fileId}`, uploadToken),
     sendResponse: sendToResponse(send),
   });
 }
@@ -327,11 +385,16 @@ export async function handleGetSendFileUpload(
   if (!expectedFileId || expectedFileId !== fileId) {
     return errorResponse('Send file does not match send data.', 400);
   }
+  const jwtSecret = getSafeJwtSecret(env);
+  if (!jwtSecret) {
+    return errorResponse('Server configuration error', 500);
+  }
+  const uploadToken = await createSendFileUploadToken(userId, send.id, fileId, jwtSecret);
 
   return jsonResponse({
-    fileUploadType: 0,
+    fileUploadType: 1,
     object: 'send-fileUpload',
-    url: `/api/sends/${send.id}/file/${fileId}`,
+    url: buildDirectUploadUrl(request, `/api/sends/${send.id}/file/${fileId}`, uploadToken),
     sendResponse: sendToResponse(send),
   });
 }
@@ -344,7 +407,6 @@ export async function handleUploadSendFile(
   fileId: string
 ): Promise<Response> {
   const storage = new StorageService(env.DB);
-  const maxFileSize = getBlobStorageMaxBytes(env, LIMITS.send.maxFileSizeBytes);
   const send = await storage.getSend(sendId);
   if (!send || send.userId !== userId) {
     return errorResponse('Send not found. Unable to save the file.', 404);
@@ -353,58 +415,43 @@ export async function handleUploadSendFile(
     return errorResponse('Send is not a file type send.', 400);
   }
 
-  const sendData = parseStoredSendData(send);
-  const expectedFileId = typeof sendData.id === 'string' ? sendData.id : null;
-  if (!expectedFileId || expectedFileId !== fileId) {
-    return errorResponse('Send file does not match send data.', 400);
+  return processSendFileUpload(request, env, send, fileId);
+}
+
+export async function handlePublicUploadSendFile(
+  request: Request,
+  env: Env,
+  sendId: string,
+  fileId: string
+): Promise<Response> {
+  const jwtSecret = getSafeJwtSecret(env);
+  if (!jwtSecret) {
+    return errorResponse('Server configuration error', 500);
   }
 
-  const contentType = request.headers.get('content-type') || '';
-  if (!contentType.includes('multipart/form-data')) {
-    return errorResponse('Content-Type must be multipart/form-data', 400);
+  const token = new URL(request.url).searchParams.get('token');
+  if (!token) {
+    return errorResponse('Token required', 401);
   }
 
-  const formData = await request.formData();
-  const file = formData.get('data') as File | null;
-  if (!file) {
-    return errorResponse('No file uploaded', 400);
+  const claims = await verifySendFileUploadToken(token, jwtSecret);
+  if (!claims) {
+    return errorResponse('Invalid or expired token', 401);
+  }
+  if (claims.sendId !== sendId || claims.fileId !== fileId) {
+    return errorResponse('Token mismatch', 401);
   }
 
-  if (file.size > maxFileSize) {
-    return errorResponse('Send storage limit exceeded with this file', 413);
+  const storage = new StorageService(env.DB);
+  const send = await storage.getSend(sendId);
+  if (!send || send.userId !== claims.userId) {
+    return errorResponse('Send not found. Unable to save the file.', 404);
+  }
+  if (send.type !== SendType.File) {
+    return errorResponse('Send is not a file type send.', 400);
   }
 
-  const expectedFileName = typeof sendData.fileName === 'string' ? sendData.fileName : null;
-  if (expectedFileName && file.name !== expectedFileName) {
-    return errorResponse('Send file name does not match.', 400);
-  }
-
-  const expectedSize = parseInteger(sendData.size);
-  if (expectedSize !== null && file.size !== expectedSize) {
-    return errorResponse('Send file size does not match.', 400);
-  }
-
-  try {
-    await putBlobObject(env, getSendFileObjectKey(sendId, fileId), file.stream(), {
-      size: file.size,
-      contentType: 'application/octet-stream',
-      customMetadata: {
-        sendId,
-        fileId,
-      },
-    });
-  } catch (error) {
-    const message = error instanceof Error ? error.message : String(error);
-    if (message.includes('KV object too large')) {
-      return errorResponse('Send storage limit exceeded with this file', 413);
-    }
-    return errorResponse('Attachment storage is not configured', 500);
-  }
-
-  const revisionDate = await storage.updateRevisionDate(userId);
-  await notifyVaultSyncForRequest(request, env, userId, revisionDate);
-
-  return new Response(null, { status: 200 });
+  return processSendFileUpload(request, env, send, fileId);
 }
 
 export async function handleUpdateSend(request: Request, env: Env, userId: string, sendId: string): Promise<Response> {

src/router-authenticated.ts

@@ -165,7 +165,7 @@ export async function handleAuthenticatedRoute(
     const attachmentMatch = subPath.match(/^\/attachment\/([a-f0-9-]+)$/i);
     if (attachmentMatch) {
       const attachmentId = attachmentMatch[1];
-      if (method === 'POST') return handleUploadAttachment(request, env, userId, cipherId, attachmentId);
+      if (method === 'POST' || method === 'PUT') return handleUploadAttachment(request, env, userId, cipherId, attachmentId);
       if (method === 'GET') return handleGetAttachment(request, env, userId, cipherId, attachmentId);
       if (method === 'DELETE') return handleDeleteAttachment(request, env, userId, cipherId, attachmentId);
     }

src/router-public.ts

@@ -14,10 +14,12 @@ import {
   handleRecoverTwoFactor,
 } from './handlers/accounts';
 import { handlePublicDownloadAttachment } from './handlers/attachments';
+import { handlePublicUploadAttachment } from './handlers/attachments';
 import {
   handleNotificationsHub,
   handleNotificationsNegotiate,
 } from './handlers/notifications';
+import { handlePublicUploadSendFile } from './handlers/sends';
 import { jsonResponse } from './utils/response';
 import type { Env } from './types';
 
@@ -162,6 +164,16 @@ export async function handlePublicRoute(
     return handlePublicDownloadAttachment(request, env, publicAttachmentMatch[1], publicAttachmentMatch[2]);
   }
 
+  const publicAttachmentUploadMatch = path.match(/^\/api\/ciphers\/([a-f0-9-]+)\/attachment\/([a-f0-9-]+)$/i);
+  if (publicAttachmentUploadMatch && (method === 'POST' || method === 'PUT') && new URL(request.url).searchParams.has('token')) {
+    return handlePublicUploadAttachment(request, env, publicAttachmentUploadMatch[1], publicAttachmentUploadMatch[2]);
+  }
+
+  const publicSendUploadMatch = path.match(/^\/api\/sends\/([^/]+)\/file\/([^/]+)\/?$/i);
+  if (publicSendUploadMatch && (method === 'POST' || method === 'PUT') && new URL(request.url).searchParams.has('token')) {
+    return handlePublicUploadSendFile(request, env, publicSendUploadMatch[1], publicSendUploadMatch[2]);
+  }
+
   const sendAccessMatch = path.match(/^\/api\/sends\/access\/([^/]+)$/i);
   if (sendAccessMatch && method === 'POST') {
     const blocked = await enforcePublicRateLimit();

src/utils/direct-upload.ts

@@ -0,0 +1,104 @@
+import { LIMITS } from '../config/limits';
+import { DEFAULT_DEV_SECRET, Env } from '../types';
+import { errorResponse } from './response';
+
+export interface DirectUploadPayload {
+  body: ReadableStream;
+  contentType: string;
+  size: number;
+}
+
+interface ParseDirectUploadOptions {
+  expectedSize?: number | null;
+  expectedFileName?: string | null;
+  maxFileSize: number;
+  tooLargeMessage: string;
+  missingBodyMessage?: string;
+  contentLengthRequiredMessage?: string;
+  sizeMismatchMessage?: string;
+  fileNameMismatchMessage?: string;
+}
+
+export function buildDirectUploadUrl(request: Request, path: string, token: string): string {
+  const version = '2023-11-03';
+  const expiresAt = '2099-12-31T23:59:59Z';
+  const origin = new URL(request.url).origin;
+  return `${origin}${path}?sv=${encodeURIComponent(version)}&se=${encodeURIComponent(expiresAt)}&token=${encodeURIComponent(token)}`;
+}
+
+export function getSafeJwtSecret(env: Env): string | null {
+  const secret = (env.JWT_SECRET || '').trim();
+  if (!secret || secret.length < LIMITS.auth.jwtSecretMinLength || secret === DEFAULT_DEV_SECRET) {
+    return null;
+  }
+  return secret;
+}
+
+function parseContentLength(request: Request): number | null {
+  const raw = request.headers.get('content-length');
+  if (!raw) return null;
+  const value = Number(raw);
+  if (!Number.isFinite(value) || value < 0) return null;
+  return Math.floor(value);
+}
+
+export async function parseDirectUploadPayload(
+  request: Request,
+  options: ParseDirectUploadOptions
+): Promise<DirectUploadPayload | Response> {
+  const {
+    expectedSize = null,
+    expectedFileName = null,
+    maxFileSize,
+    tooLargeMessage,
+    missingBodyMessage = 'No file uploaded',
+    contentLengthRequiredMessage = 'Content-Length is required for direct uploads',
+    sizeMismatchMessage,
+    fileNameMismatchMessage,
+  } = options;
+  const contentType = request.headers.get('content-type') || '';
+
+  if (contentType.includes('multipart/form-data')) {
+    const formData = await request.formData();
+    const file = formData.get('data') as File | null;
+    if (!file) {
+      return errorResponse(missingBodyMessage, 400);
+    }
+    if (file.size > maxFileSize) {
+      return errorResponse(tooLargeMessage, 413);
+    }
+    if (expectedFileName && file.name !== expectedFileName) {
+      return errorResponse(fileNameMismatchMessage || 'File name does not match.', 400);
+    }
+    if (expectedSize !== null && expectedSize !== undefined && file.size !== expectedSize) {
+      return errorResponse(sizeMismatchMessage || 'File size does not match.', 400);
+    }
+    return {
+      body: file.stream(),
+      contentType: file.type || 'application/octet-stream',
+      size: file.size,
+    };
+  }
+
+  if (!request.body) {
+    return errorResponse(missingBodyMessage, 400);
+  }
+
+  const declaredSize = parseContentLength(request);
+  const uploadSize = declaredSize ?? (expectedSize && expectedSize > 0 ? expectedSize : null);
+  if (uploadSize === null) {
+    return errorResponse(contentLengthRequiredMessage, 400);
+  }
+  if (uploadSize > maxFileSize) {
+    return errorResponse(tooLargeMessage, 413);
+  }
+  if (expectedSize !== null && expectedSize !== undefined && uploadSize !== expectedSize) {
+    return errorResponse(sizeMismatchMessage || 'File size does not match.', 400);
+  }
+
+  return {
+    body: request.body,
+    contentType: contentType || 'application/octet-stream',
+    size: uploadSize,
+  };
+}

src/utils/jwt.ts

@@ -104,6 +104,13 @@ export interface FileDownloadClaims {
   exp: number;
 }
 
+export interface AttachmentUploadClaims {
+  userId: string;
+  cipherId: string;
+  attachmentId: string;
+  exp: number;
+}
+
 // Create file download token (short-lived, 5 minutes)
 export async function createFileDownloadToken(
   cipherId: string,
@@ -178,6 +185,73 @@ export async function verifyFileDownloadToken(
   }
 }
 
+export async function createAttachmentUploadToken(
+  userId: string,
+  cipherId: string,
+  attachmentId: string,
+  secret: string
+): Promise<string> {
+  const header = { alg: 'HS256', typ: 'JWT' };
+  const now = Math.floor(Date.now() / 1000);
+  const payload: AttachmentUploadClaims = {
+    userId,
+    cipherId,
+    attachmentId,
+    exp: now + LIMITS.auth.fileDownloadTokenTtlSeconds,
+  };
+
+  const encoder = new TextEncoder();
+  const headerB64 = base64UrlEncode(encoder.encode(JSON.stringify(header)));
+  const payloadB64 = base64UrlEncode(encoder.encode(JSON.stringify(payload)));
+  const data = `${headerB64}.${payloadB64}`;
+
+  const key = await crypto.subtle.importKey(
+    'raw',
+    encoder.encode(secret),
+    { name: 'HMAC', hash: 'SHA-256' },
+    false,
+    ['sign']
+  );
+
+  const signature = await crypto.subtle.sign('HMAC', key, encoder.encode(data));
+  const signatureB64 = base64UrlEncode(new Uint8Array(signature));
+  return `${data}.${signatureB64}`;
+}
+
+export async function verifyAttachmentUploadToken(
+  token: string,
+  secret: string
+): Promise<AttachmentUploadClaims | null> {
+  try {
+    const parts = token.split('.');
+    if (parts.length !== 3) return null;
+
+    const [headerB64, payloadB64, signatureB64] = parts;
+    const encoder = new TextEncoder();
+
+    const key = await crypto.subtle.importKey(
+      'raw',
+      encoder.encode(secret),
+      { name: 'HMAC', hash: 'SHA-256' },
+      false,
+      ['verify']
+    );
+
+    const data = `${headerB64}.${payloadB64}`;
+    const signature = base64UrlDecode(signatureB64);
+    const valid = await crypto.subtle.verify('HMAC', key, signature, encoder.encode(data));
+    if (!valid) return null;
+
+    const payload: AttachmentUploadClaims = JSON.parse(new TextDecoder().decode(base64UrlDecode(payloadB64)));
+    const now = Math.floor(Date.now() / 1000);
+    if (payload.exp < now) return null;
+    if (!payload.userId || !payload.cipherId || !payload.attachmentId) return null;
+    return payload;
+  } catch {
+    return null;
+  }
+}
+
 export interface SendFileDownloadClaims {
   sendId: string;
   fileId: string;
@@ -185,6 +259,13 @@ export interface SendFileDownloadClaims {
   exp: number;
 }
 
+export interface SendFileUploadClaims {
+  userId: string;
+  sendId: string;
+  fileId: string;
+  exp: number;
+}
+
 export async function createSendFileDownloadToken(
   sendId: string,
   fileId: string,
@@ -260,6 +341,73 @@ export async function verifySendFileDownloadToken(
   }
 }
 
+export async function createSendFileUploadToken(
+  userId: string,
+  sendId: string,
+  fileId: string,
+  secret: string
+): Promise<string> {
+  const header = { alg: 'HS256', typ: 'JWT' };
+  const now = Math.floor(Date.now() / 1000);
+  const payload: SendFileUploadClaims = {
+    userId,
+    sendId,
+    fileId,
+    exp: now + LIMITS.auth.fileDownloadTokenTtlSeconds,
+  };
+
+  const encoder = new TextEncoder();
+  const headerB64 = base64UrlEncode(encoder.encode(JSON.stringify(header)));
+  const payloadB64 = base64UrlEncode(encoder.encode(JSON.stringify(payload)));
+  const data = `${headerB64}.${payloadB64}`;
+
+  const key = await crypto.subtle.importKey(
+    'raw',
+    encoder.encode(secret),
+    { name: 'HMAC', hash: 'SHA-256' },
+    false,
+    ['sign']
+  );
+
+  const signature = await crypto.subtle.sign('HMAC', key, encoder.encode(data));
+  const signatureB64 = base64UrlEncode(new Uint8Array(signature));
+  return `${data}.${signatureB64}`;
+}
+
+export async function verifySendFileUploadToken(
+  token: string,
+  secret: string
+): Promise<SendFileUploadClaims | null> {
+  try {
+    const parts = token.split('.');
+    if (parts.length !== 3) return null;
+
+    const [headerB64, payloadB64, signatureB64] = parts;
+    const encoder = new TextEncoder();
+
+    const key = await crypto.subtle.importKey(
+      'raw',
+      encoder.encode(secret),
+      { name: 'HMAC', hash: 'SHA-256' },
+      false,
+      ['verify']
+    );
+
+    const data = `${headerB64}.${payloadB64}`;
+    const signature = base64UrlDecode(signatureB64);
+    const valid = await crypto.subtle.verify('HMAC', key, signature, encoder.encode(data));
+    if (!valid) return null;
+
+    const payload: SendFileUploadClaims = JSON.parse(new TextDecoder().decode(base64UrlDecode(payloadB64)));
+    const now = Math.floor(Date.now() / 1000);
+    if (payload.exp < now) return null;
+    if (!payload.userId || !payload.sendId || !payload.fileId) return null;
+    return payload;
+  } catch {
+    return null;
+  }
+}
+
 export interface SendAccessTokenClaims {
   sub: string; // send id
   typ: 'send_access';