feat: enhance send functionality with improved key handling and decryption, update UI components for better user experience

src/handlers/sends.ts

@@ -195,6 +195,14 @@ function constantTimeEqual(a: Uint8Array, b: Uint8Array): boolean {
   return diff === 0;
 }
 
+function isLikelyHashB64(value: string): boolean {
+  const raw = String(value || '').trim();
+  if (!raw) return false;
+  if (!/^[A-Za-z0-9+/_=-]+$/.test(raw)) return false;
+  const decoded = base64UrlDecode(raw);
+  return !!decoded && decoded.length === 32;
+}
+
 async function setSendPassword(send: Send, password: string | null): Promise<void> {
   if (!password) {
     send.passwordHash = null;
@@ -206,6 +214,16 @@ async function setSendPassword(send: Send, password: string | null): Promise<voi
     return;
   }
 
+  // Official client behavior: request.password already contains PBKDF2 hash (base64).
+  // Keep it as-is to remain interoperable.
+  if (isLikelyHashB64(password)) {
+    send.passwordHash = password.trim();
+    send.passwordSalt = null;
+    send.passwordIterations = null;
+    send.authType = SendAuthType.Password;
+    return;
+  }
+
   const salt = crypto.getRandomValues(new Uint8Array(64));
   const hash = await deriveSendPasswordHash(password, salt, SEND_PASSWORD_ITERATIONS);
 
@@ -216,10 +234,15 @@ async function setSendPassword(send: Send, password: string | null): Promise<voi
 }
 
 export async function verifySendPassword(send: Send, password: string): Promise<boolean> {
-  if (!send.passwordHash || !send.passwordSalt || !send.passwordIterations) {
+  if (!send.passwordHash) {
     return false;
   }
 
+  // Official client behavior: password is already a hash in base64.
+  if (!send.passwordSalt || !send.passwordIterations) {
+    return verifySendPasswordHashB64(send, password);
+  }
+
   const salt = base64UrlDecode(send.passwordSalt);
   const expected = base64UrlDecode(send.passwordHash);
   if (!salt || !expected) return false;
@@ -360,14 +383,30 @@ async function validatePublicSendAccess(send: Send, body: unknown): Promise<Resp
   if (!send.passwordHash) return null;
 
   const passwordRaw = getAliasedProp(body, ['password', 'Password']);
+  const passwordHashB64Raw = getAliasedProp(body, [
+    'password_hash_b64',
+    'passwordHashB64',
+    'passwordHash',
+    'password_hash',
+  ]);
+
+  let validPassword = false;
+  if (send.passwordSalt && send.passwordIterations) {
     if (typeof passwordRaw.value !== 'string') {
       return errorResponse('Password not provided', 401);
     }
-
-  const validPassword = await verifySendPassword(send, passwordRaw.value);
-  if (!validPassword) {
-    return errorResponse('Invalid password', 400);
+    validPassword = await verifySendPassword(send, passwordRaw.value);
+  } else {
+    const candidate =
+      typeof passwordHashB64Raw.value === 'string'
+        ? passwordHashB64Raw.value
+        : typeof passwordRaw.value === 'string'
+          ? passwordRaw.value
+          : '';
+    if (!candidate) return errorResponse('Password not provided', 401);
+    validPassword = verifySendPasswordHashB64(send, candidate);
   }
+  if (!validPassword) return errorResponse('Invalid password', 400);
 
   return null;
 }
@@ -1153,12 +1192,12 @@ export async function handleDownloadSendFile(
 
 export async function issueSendAccessToken(
   env: Env,
-  sendId: string,
+  sendIdOrAccessId: string,
   passwordHashB64?: string | null,
   password?: string | null
 ): Promise<{ token: string } | { error: Response }> {
   const storage = new StorageService(env.DB);
-  const send = await storage.getSend(sendId);
+  const send = await resolveSendFromIdOrAccessId(storage, sendIdOrAccessId);
 
   if (!send || !isSendAvailable(send)) {
     return {

webapp/src/App.tsx

@@ -47,7 +47,7 @@ import {
   updateProfile,
   verifyMasterPassword,
 } from '@/lib/api';
-import { base64ToBytes, decryptBw, decryptStr } from '@/lib/crypto';
+import { base64ToBytes, decryptBw, decryptStr, hkdf } from '@/lib/crypto';
 import type { AppPhase, Cipher, Folder, Profile, Send, SendDraft, SessionState, ToastMessage, VaultDraft } from '@/lib/types';
 
 interface PendingTotp {
@@ -56,6 +56,21 @@ interface PendingTotp {
   masterKey: Uint8Array;
 }
 
+const SEND_KEY_SALT = 'bitwarden-send';
+const SEND_KEY_PURPOSE = 'send';
+
+function buildPublicSendUrl(origin: string, accessId: string, keyPart: string): string {
+  return `${origin}/#/send/${accessId}/${keyPart}`;
+}
+
+async function deriveSendKeyParts(sendKeyMaterial: Uint8Array): Promise<{ enc: Uint8Array; mac: Uint8Array }> {
+  if (sendKeyMaterial.length >= 64) {
+    return { enc: sendKeyMaterial.slice(0, 32), mac: sendKeyMaterial.slice(32, 64) };
+  }
+  const derived = await hkdf(sendKeyMaterial, SEND_KEY_SALT, SEND_KEY_PURPOSE, 64);
+  return { enc: derived.slice(0, 32), mac: derived.slice(32, 64) };
+}
+
 export default function App() {
   const [location, navigate] = useLocation();
   const [phase, setPhase] = useState<AppPhase>('loading');
@@ -460,14 +475,20 @@ export default function App() {
             try {
               if (send.key) {
                 const sendKeyRaw = await decryptBw(send.key, encKey, macKey);
-                const sendEnc = sendKeyRaw.slice(0, 32);
-                const sendMac = sendKeyRaw.slice(32, 64);
-                nextSend.decName = await decryptField(send.name || '', sendEnc, sendMac);
-                nextSend.decNotes = await decryptField(send.notes || '', sendEnc, sendMac);
-                nextSend.decText = await decryptField(send.text?.text || '', sendEnc, sendMac);
+                const derived = await deriveSendKeyParts(sendKeyRaw);
+                nextSend.decName = await decryptField(send.name || '', derived.enc, derived.mac);
+                nextSend.decNotes = await decryptField(send.notes || '', derived.enc, derived.mac);
+                nextSend.decText = await decryptField(send.text?.text || '', derived.enc, derived.mac);
+                if (send.file?.fileName) {
+                  const decFileName = await decryptField(send.file.fileName, derived.enc, derived.mac);
+                  nextSend.file = {
+                    ...(send.file || {}),
+                    fileName: decFileName || send.file.fileName,
+                  };
+                }
                 const shareKey = await buildSendShareKey(send.key, session.symEncKey!, session.symMacKey!);
                 nextSend.decShareKey = shareKey;
-                nextSend.shareUrl = `${window.location.origin}/send/${send.accessId}/${shareKey}`;
+                nextSend.shareUrl = buildPublicSendUrl(window.location.origin, send.accessId, shareKey);
               } else {
                 nextSend.decName = '';
                 nextSend.decNotes = '';
@@ -637,7 +658,7 @@ export default function App() {
       await sendsQuery.refetch();
       if (autoCopyLink && created.key && session.symEncKey && session.symMacKey) {
         const keyPart = await buildSendShareKey(created.key, session.symEncKey, session.symMacKey);
-        const shareUrl = `${window.location.origin}/send/${created.accessId}/${keyPart}`;
+        const shareUrl = buildPublicSendUrl(window.location.origin, created.accessId, keyPart);
         await navigator.clipboard.writeText(shareUrl);
       }
       pushToast('success', 'Send created');
@@ -654,7 +675,7 @@ export default function App() {
       await sendsQuery.refetch();
       if (autoCopyLink && updated.key && session.symEncKey && session.symMacKey) {
         const keyPart = await buildSendShareKey(updated.key, session.symEncKey, session.symMacKey);
-        const shareUrl = `${window.location.origin}/send/${updated.accessId}/${keyPart}`;
+        const shareUrl = buildPublicSendUrl(window.location.origin, updated.accessId, keyPart);
         await navigator.clipboard.writeText(shareUrl);
       }
       pushToast('success', 'Send updated');
@@ -709,11 +730,16 @@ export default function App() {
     }
   }
 
-  useEffect(() => {
-    if (phase === 'app' && location === '/') navigate('/vault');
-  }, [phase, location, navigate]);
+  const hashPathRaw = typeof window !== 'undefined' ? window.location.hash || '' : '';
+  const hashPath = hashPathRaw.startsWith('#') ? hashPathRaw.slice(1) : hashPathRaw;
+  const effectiveLocation = hashPath.startsWith('/send/') ? hashPath : location;
+  const publicSendMatch = effectiveLocation.match(/^\/send\/([^/]+)(?:\/([^/]+))?\/?$/i);
+  const isPublicSendRoute = !!publicSendMatch;
+
+  useEffect(() => {
+    if (phase === 'app' && location === '/' && !isPublicSendRoute) navigate('/vault');
+  }, [phase, location, isPublicSendRoute, navigate]);
 
-  const publicSendMatch = location.match(/^\/send\/([^/]+)(?:\/([^/]+))?\/?$/i);
   if (publicSendMatch) {
     return (
       <>

webapp/src/components/PublicSendPage.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState } from 'preact/hooks';
 import { Download, Eye, Lock } from 'lucide-preact';
-import { accessPublicSend, accessPublicSendFile, decryptPublicSend } from '@/lib/api';
+import { accessPublicSend, accessPublicSendFile, decryptPublicSend, decryptPublicSendFileBytes } from '@/lib/api';
 
 interface PublicSendPageProps {
   accessId: string;
@@ -19,7 +19,7 @@ export default function PublicSendPage(props: PublicSendPageProps) {
     setBusy(true);
     setError('');
     try {
-      const data = await accessPublicSend(props.accessId, pass);
+      const data = await accessPublicSend(props.accessId, props.keyPart, pass);
       if (!props.keyPart) {
         setError('This link is missing decryption key.');
         setSendData(null);
@@ -48,10 +48,22 @@ export default function PublicSendPage(props: PublicSendPageProps) {
     setBusy(true);
     setError('');
     try {
-      const url = await accessPublicSendFile(sendData.id, sendData.file.id, password || undefined);
+      const url = await accessPublicSendFile(sendData.id, sendData.file.id, props.keyPart, password || undefined);
       const resp = await fetch(url);
       if (!resp.ok) throw new Error('Download failed');
-      const blob = await resp.blob();
+      const encryptedBytes = await resp.arrayBuffer();
+      let blob: Blob;
+      if (props.keyPart) {
+        try {
+          const decryptedBytes = await decryptPublicSendFileBytes(encryptedBytes, props.keyPart);
+          blob = new Blob([decryptedBytes as unknown as BlobPart], { type: 'application/octet-stream' });
+        } catch {
+          // Legacy compatibility: early web-created file sends uploaded plaintext bytes.
+          blob = new Blob([encryptedBytes], { type: 'application/octet-stream' });
+        }
+      } else {
+        blob = new Blob([encryptedBytes], { type: 'application/octet-stream' });
+      }
       const obj = URL.createObjectURL(blob);
       const a = document.createElement('a');
       a.href = obj;

webapp/src/components/SendsPage.tsx

@@ -169,7 +169,7 @@ export default function SendsPage(props: SendsPageProps) {
   }
 
   function copyAccessUrl(send: Send): void {
-    const url = send.shareUrl || `${window.location.origin}/send/${send.accessId}`;
+    const url = send.shareUrl || `${window.location.origin}/#/send/${send.accessId}`;
     void navigator.clipboard.writeText(url);
     props.onNotify('success', 'Link copied');
   }

webapp/src/lib/api.ts

@@ -1,4 +1,4 @@
-import { base64ToBytes, bytesToBase64, decryptBw, decryptStr, encryptBw, hkdfExpand, pbkdf2 } from './crypto';
+import { base64ToBytes, bytesToBase64, decryptBw, decryptBwFileData, decryptStr, encryptBw, encryptBwFileData, hkdf, hkdfExpand, pbkdf2 } from './crypto';
 import type {
   AdminInvite,
   AdminUser,
@@ -673,19 +673,29 @@ function base64UrlToBytes(value: string): Uint8Array {
   return base64ToBytes(padded);
 }
 
+const SEND_KEY_SALT = 'bitwarden-send';
+const SEND_KEY_PURPOSE = 'send';
+const SEND_KEY_SEED_BYTES = 16;
+const SEND_PASSWORD_ITERATIONS = 100000;
+
 async function parseErrorMessage(resp: Response, fallback: string): Promise<string> {
   const body = await parseJson<TokenError>(resp);
   return body?.error_description || body?.error || fallback;
 }
 
-function toSendKeyParts(sendKeyBytes: Uint8Array): { enc: Uint8Array; mac: Uint8Array } {
-  if (sendKeyBytes.length >= 64) {
-    return { enc: sendKeyBytes.slice(0, 32), mac: sendKeyBytes.slice(32, 64) };
+async function toSendKeyParts(sendKeyMaterial: Uint8Array): Promise<{ enc: Uint8Array; mac: Uint8Array }> {
+  // Legacy compatibility: early NodeWarden builds stored a full 64-byte key material.
+  if (sendKeyMaterial.length >= 64) {
+    return { enc: sendKeyMaterial.slice(0, 32), mac: sendKeyMaterial.slice(32, 64) };
   }
-  const merged = new Uint8Array(64);
-  merged.set(sendKeyBytes.slice(0, 32), 0);
-  merged.set(sendKeyBytes.slice(0, 32), 32);
-  return { enc: merged.slice(0, 32), mac: merged.slice(32, 64) };
+  // Official behavior: send URL key is seed material; derive 64-byte key via HKDF.
+  const derived = await hkdf(sendKeyMaterial, SEND_KEY_SALT, SEND_KEY_PURPOSE, 64);
+  return { enc: derived.slice(0, 32), mac: derived.slice(32, 64) };
+}
+
+async function hashSendPasswordB64(password: string, sendKeyMaterial: Uint8Array): Promise<string> {
+  const hash = await pbkdf2(password, sendKeyMaterial, SEND_PASSWORD_ITERATIONS, 32);
+  return bytesToBase64(hash);
 }
 
 function parseMaxAccessCountRaw(value: string): number | null {
@@ -704,9 +714,9 @@ export async function createSend(
   if (!session.symEncKey || !session.symMacKey) throw new Error('Vault key unavailable');
   const userEnc = base64ToBytes(session.symEncKey);
   const userMac = base64ToBytes(session.symMacKey);
-  const sendKeyRaw = crypto.getRandomValues(new Uint8Array(64));
-  const sendKeyForUser = await encryptBw(sendKeyRaw, userEnc, userMac);
-  const sendKey = toSendKeyParts(sendKeyRaw);
+  const sendKeyMaterial = crypto.getRandomValues(new Uint8Array(SEND_KEY_SEED_BYTES));
+  const sendKeyForUser = await encryptBw(sendKeyMaterial, userEnc, userMac);
+  const sendKey = await toSendKeyParts(sendKeyMaterial);
   const nameCipher = await encryptTextValue(draft.name || '', sendKey.enc, sendKey.mac);
   const notesCipher = await encryptTextValue(draft.notes || '', sendKey.enc, sendKey.mac);
 
@@ -714,6 +724,7 @@ export async function createSend(
   const expirationIso = toIsoDateFromDays(draft.expirationDays, false);
   const maxAccessCount = parseMaxAccessCountRaw(draft.maxAccessCount);
   const password = String(draft.password || '');
+  const passwordHash = password ? await hashSendPasswordB64(password, sendKeyMaterial) : null;
 
   if (draft.type === 'text') {
     const text = String(draft.text || '').trim();
@@ -730,7 +741,7 @@ export async function createSend(
         hidden: false,
       },
       maxAccessCount,
-      password: password || null,
+      password: passwordHash,
       hideEmail: false,
       disabled: !!draft.disabled,
       deletionDate: deletionIso,
@@ -749,6 +760,10 @@ export async function createSend(
   }
 
   if (!draft.file) throw new Error('File is required');
+  const fileNameCipher = await encryptTextValue(draft.file.name, sendKey.enc, sendKey.mac);
+  if (!fileNameCipher) throw new Error('Invalid file name');
+  const plainFileBytes = new Uint8Array(await draft.file.arrayBuffer());
+  const encryptedFileBytes = await encryptBwFileData(plainFileBytes, sendKey.enc, sendKey.mac);
 
   const fileResp = await authedFetch('/api/sends/file/v2', {
     method: 'POST',
@@ -759,11 +774,11 @@ export async function createSend(
       notes: notesCipher,
       key: sendKeyForUser,
       file: {
-        fileName: draft.file.name,
+        fileName: fileNameCipher,
       },
-      fileLength: draft.file.size,
+      fileLength: encryptedFileBytes.byteLength,
       maxAccessCount,
-      password: password || null,
+      password: passwordHash,
       hideEmail: false,
       disabled: !!draft.disabled,
       deletionDate: deletionIso,
@@ -772,20 +787,20 @@ export async function createSend(
   });
   if (!fileResp.ok) throw new Error(await parseErrorMessage(fileResp, 'Create file send failed'));
 
-  const uploadInfo = await parseJson<{ url?: string }>(fileResp);
+  const uploadInfo = await parseJson<{ url?: string; sendResponse?: Send }>(fileResp);
   const uploadUrl = uploadInfo?.url;
   if (!uploadUrl) throw new Error('Create file send failed: missing upload URL');
 
   const formData = new FormData();
-  formData.set('data', draft.file, draft.file.name);
+  const encryptedBlob = new Blob([encryptedFileBytes as unknown as BlobPart], { type: 'application/octet-stream' });
+  formData.set('data', encryptedBlob, fileNameCipher);
   const uploadResp = await authedFetch(uploadUrl, {
     method: 'POST',
     body: formData,
   });
   if (!uploadResp.ok) throw new Error(await parseErrorMessage(uploadResp, 'Upload send file failed'));
-  const fileBody = await parseJson<{ sendResponse?: Send }>(fileResp);
-  if (!fileBody?.sendResponse?.id) throw new Error('Create file send failed');
-  return fileBody.sendResponse;
+  if (!uploadInfo?.sendResponse?.id) throw new Error('Create file send failed');
+  return uploadInfo.sendResponse;
 }
 
 export async function updateSend(
@@ -798,8 +813,8 @@ export async function updateSend(
   if (!send.key) throw new Error('Send key unavailable');
   const userEnc = base64ToBytes(session.symEncKey);
   const userMac = base64ToBytes(session.symMacKey);
-  const sendKeyRaw = await decryptBw(send.key, userEnc, userMac);
-  const sendKey = toSendKeyParts(sendKeyRaw);
+  const sendKeyMaterial = await decryptBw(send.key, userEnc, userMac);
+  const sendKey = await toSendKeyParts(sendKeyMaterial);
   const nameCipher = await encryptTextValue(draft.name || '', sendKey.enc, sendKey.mac);
   const notesCipher = await encryptTextValue(draft.notes || '', sendKey.enc, sendKey.mac);
 
@@ -813,6 +828,9 @@ export async function updateSend(
 
   const textCipher = await encryptTextValue(String(draft.text || ''), sendKey.enc, sendKey.mac);
 
+  const passwordRaw = String(draft.password || '');
+  const passwordHash = passwordRaw ? await hashSendPasswordB64(passwordRaw, sendKeyMaterial) : null;
+
   const payload = {
     id: send.id,
     type: draft.type === 'file' ? 1 : 0,
@@ -824,7 +842,7 @@ export async function updateSend(
       hidden: false,
     },
     maxAccessCount,
-    password: String(draft.password || '') || null,
+    password: passwordHash,
     hideEmail: false,
     disabled: !!draft.disabled,
     deletionDate: deletionIso,
@@ -850,8 +868,29 @@ export async function deleteSend(
   if (!resp.ok) throw new Error(await parseErrorMessage(resp, 'Delete send failed'));
 }
 
-export async function accessPublicSend(accessId: string, password?: string): Promise<any> {
-  const payload = password ? { password } : {};
+async function buildPublicSendAccessPayload(password?: string, keyPart?: string | null): Promise<Record<string, unknown>> {
+  const payload: Record<string, unknown> = {};
+  const plainPassword = String(password || '').trim();
+  if (!plainPassword) return payload;
+  payload.password = plainPassword;
+
+  // Official clients send a PBKDF2 hash bound to send key material.
+  if (keyPart) {
+    try {
+      const sendKeyMaterial = base64UrlToBytes(keyPart);
+      const passwordHashB64 = await hashSendPasswordB64(plainPassword, sendKeyMaterial);
+      payload.passwordHash = passwordHashB64;
+      payload.password_hash_b64 = passwordHashB64;
+      payload.passwordHashB64 = passwordHashB64;
+    } catch {
+      // Fallback to plain password for legacy compatibility.
+    }
+  }
+  return payload;
+}
+
+export async function accessPublicSend(accessId: string, keyPart?: string | null, password?: string): Promise<any> {
+  const payload = await buildPublicSendAccessPayload(password, keyPart);
   const resp = await fetch(`/api/sends/access/${encodeURIComponent(accessId)}`, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
@@ -866,8 +905,8 @@ export async function accessPublicSend(accessId: string, password?: string): Pro
   return (await parseJson<any>(resp)) || null;
 }
 
-export async function accessPublicSendFile(sendId: string, fileId: string, password?: string): Promise<string> {
-  const payload = password ? { password } : {};
+export async function accessPublicSendFile(sendId: string, fileId: string, keyPart?: string | null, password?: string): Promise<string> {
+  const payload = await buildPublicSendAccessPayload(password, keyPart);
   const resp = await fetch(`/api/sends/${encodeURIComponent(sendId)}/access/file/${encodeURIComponent(fileId)}`, {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
@@ -885,8 +924,8 @@ export async function accessPublicSendFile(sendId: string, fileId: string, passw
 }
 
 export async function decryptPublicSend(accessData: any, urlSafeKey: string): Promise<any> {
-  const sendKeyRaw = base64UrlToBytes(urlSafeKey);
-  const sendKey = toSendKeyParts(sendKeyRaw);
+  const sendKeyMaterial = base64UrlToBytes(urlSafeKey);
+  const sendKey = await toSendKeyParts(sendKeyMaterial);
   const out: any = { ...accessData };
   out.decName = await decryptStr(accessData?.name || '', sendKey.enc, sendKey.mac);
   if (accessData?.text?.text) {
@@ -902,8 +941,18 @@ export async function decryptPublicSend(accessData: any, urlSafeKey: string): Pr
   return out;
 }
 
+export async function decryptPublicSendFileBytes(
+  encryptedBytes: ArrayBuffer | Uint8Array,
+  urlSafeKey: string
+): Promise<Uint8Array> {
+  const sendKeyMaterial = base64UrlToBytes(urlSafeKey);
+  const sendKey = await toSendKeyParts(sendKeyMaterial);
+  const encrypted = encryptedBytes instanceof Uint8Array ? encryptedBytes : new Uint8Array(encryptedBytes);
+  return decryptBwFileData(encrypted, sendKey.enc, sendKey.mac);
+}
+
 export function buildSendShareKey(sendKeyEncrypted: string, userEncB64: string, userMacB64: string): Promise<string> {
   const userEnc = base64ToBytes(userEncB64);
   const userMac = base64ToBytes(userMacB64);
-  return decryptBw(sendKeyEncrypted, userEnc, userMac).then((raw) => bytesToBase64Url(raw));
+  return decryptBw(sendKeyEncrypted, userEnc, userMac).then((keyMaterial) => bytesToBase64Url(keyMaterial));
 }

webapp/src/lib/crypto.ts

@@ -62,6 +62,25 @@ export async function hkdfExpand(prk: Uint8Array, info: string, length: number):
   return result;
 }
 
+export async function hkdf(
+  ikm: Uint8Array,
+  salt: string | Uint8Array,
+  info: string | Uint8Array,
+  outputByteSize: number
+): Promise<Uint8Array> {
+  const saltBytes = typeof salt === 'string' ? new TextEncoder().encode(salt) : salt;
+  const infoBytes = typeof info === 'string' ? new TextEncoder().encode(info) : info;
+  const params: HkdfParams = {
+    name: 'HKDF',
+    salt: toBufferSource(saltBytes),
+    info: toBufferSource(infoBytes),
+    hash: 'SHA-256',
+  };
+  const key = await crypto.subtle.importKey('raw', toBufferSource(ikm), 'HKDF', false, ['deriveBits']);
+  const bits = await crypto.subtle.deriveBits(params, key, outputByteSize * 8);
+  return new Uint8Array(bits);
+}
+
 async function hmacSha256(keyBytes: Uint8Array, dataBytes: Uint8Array): Promise<Uint8Array> {
   const key = await crypto.subtle.importKey('raw', toBufferSource(keyBytes), { name: 'HMAC', hash: 'SHA-256' }, false, ['sign']);
   return new Uint8Array(await crypto.subtle.sign('HMAC', key, toBufferSource(dataBytes)));
@@ -77,6 +96,30 @@ async function decryptAesCbc(data: Uint8Array, key: Uint8Array, iv: Uint8Array):
   return new Uint8Array(await crypto.subtle.decrypt({ name: 'AES-CBC', iv: toBufferSource(iv) }, cryptoKey, toBufferSource(data)));
 }
 
+export async function encryptBwFileData(data: Uint8Array, encKey: Uint8Array, macKey: Uint8Array): Promise<Uint8Array> {
+  const iv = crypto.getRandomValues(new Uint8Array(16));
+  const cipher = await encryptAesCbc(data, encKey, iv);
+  const mac = await hmacSha256(macKey, concatBytes(iv, cipher));
+  const out = new Uint8Array(1 + iv.length + mac.length + cipher.length);
+  out[0] = 2; // EncryptionType.AesCbc256_HmacSha256_B64
+  out.set(iv, 1);
+  out.set(mac, 1 + iv.length);
+  out.set(cipher, 1 + iv.length + mac.length);
+  return out;
+}
+
+export async function decryptBwFileData(encrypted: Uint8Array, encKey: Uint8Array, macKey: Uint8Array): Promise<Uint8Array> {
+  if (!encrypted || encrypted.length < 1 + 16 + 32 + 1) throw new Error('Invalid encrypted file data');
+  const encType = encrypted[0];
+  if (encType !== 2) throw new Error('Unsupported file encryption type');
+  const iv = encrypted.slice(1, 17);
+  const mac = encrypted.slice(17, 49);
+  const cipher = encrypted.slice(49);
+  const expected = await hmacSha256(macKey, concatBytes(iv, cipher));
+  if (bytesToBase64(expected) !== bytesToBase64(mac)) throw new Error('MAC mismatch');
+  return decryptAesCbc(cipher, encKey, iv);
+}
+
 export async function encryptBw(data: Uint8Array, encKey: Uint8Array, macKey: Uint8Array): Promise<string> {
   const iv = crypto.getRandomValues(new Uint8Array(16));
   const cipher = await encryptAesCbc(data, encKey, iv);

webapp/src/styles.css

@@ -46,7 +46,7 @@ html {
 }
 
 .public-send-page {
-  min-height: 100vh;
+  min-height: 80vh;
   align-items: center;
   justify-items: center;
 }