feat(web-security): encrypt offline data at rest

2026-04-06 16:07:37 +08:00
parent 1ea483016f
commit 1564d2dd30
8 changed files with 399 additions and 38 deletions
@@ -0,0 +1,126 @@
+const LOCAL_CRYPTO_KEY_STORAGE_KEY = "todolist.web.local-crypto-key";
+const LOCAL_CRYPTO_PREFIX = "locv1";
+const LOCAL_CRYPTO_IV_LENGTH = 12;
+const LOCAL_CRYPTO_KEY_LENGTH = 32;
+
+let cachedLocalCryptoKeyPromise: Promise<CryptoKey> | null = null;
+
+function toArrayBuffer(bytes: Uint8Array): ArrayBuffer {
+  return bytes.buffer.slice(bytes.byteOffset, bytes.byteOffset + bytes.byteLength) as ArrayBuffer;
+}
+
+function bytesToBase64Url(bytes: Uint8Array): string {
+  let binary = "";
+  const chunkSize = 0x8000;
+
+  for (let index = 0; index < bytes.length; index += chunkSize) {
+    const chunk = bytes.subarray(index, index + chunkSize);
+    binary += String.fromCharCode(...chunk);
+  }
+
+  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/u, "");
+}
+
+function base64UrlToBytes(value: string): Uint8Array {
+  const normalizedValue = value.replace(/-/g, "+").replace(/_/g, "/");
+  const paddedValue = normalizedValue + "=".repeat((4 - (normalizedValue.length % 4 || 4)) % 4);
+  const binary = atob(paddedValue);
+  const bytes = new Uint8Array(binary.length);
+
+  for (let index = 0; index < binary.length; index += 1) {
+    bytes[index] = binary.charCodeAt(index);
+  }
+
+  return bytes;
+}
+
+function createRandomKeyBytes(): Uint8Array {
+  const bytes = new Uint8Array(LOCAL_CRYPTO_KEY_LENGTH);
+  crypto.getRandomValues(bytes);
+  return bytes;
+}
+
+async function resolveLocalCryptoKey(): Promise<CryptoKey> {
+  if (cachedLocalCryptoKeyPromise) {
+    return cachedLocalCryptoKeyPromise;
+  }
+
+  cachedLocalCryptoKeyPromise = (async () => {
+    const savedKey = window.localStorage.getItem(LOCAL_CRYPTO_KEY_STORAGE_KEY);
+    const keyBytes = savedKey ? base64UrlToBytes(savedKey) : createRandomKeyBytes();
+
+    if (!savedKey) {
+      window.localStorage.setItem(LOCAL_CRYPTO_KEY_STORAGE_KEY, bytesToBase64Url(keyBytes));
+    }
+
+    return crypto.subtle.importKey("raw", toArrayBuffer(keyBytes), "AES-GCM", false, [
+      "encrypt",
+      "decrypt"
+    ]);
+  })();
+
+  return cachedLocalCryptoKeyPromise;
+}
+
+export function isLocalEncryptedString(value: string): boolean {
+  return value.startsWith(`${LOCAL_CRYPTO_PREFIX}:`);
+}
+
+export async function encryptLocalString(
+  value: string | null | undefined
+): Promise<string | null | undefined> {
+  if (value === undefined || value === null) {
+    return value;
+  }
+
+  if (isLocalEncryptedString(value)) {
+    return value;
+  }
+
+  const key = await resolveLocalCryptoKey();
+  const iv = crypto.getRandomValues(new Uint8Array(LOCAL_CRYPTO_IV_LENGTH));
+  const plaintext = new TextEncoder().encode(value);
+  const encryptedBuffer = await crypto.subtle.encrypt(
+    {
+      name: "AES-GCM",
+      iv
+    },
+    key,
+    plaintext
+  );
+
+  return `${LOCAL_CRYPTO_PREFIX}:${bytesToBase64Url(iv)}:${bytesToBase64Url(new Uint8Array(encryptedBuffer))}`;
+}
+
+export async function decryptLocalString(
+  value: string | null | undefined
+): Promise<string | null | undefined> {
+  if (value === undefined || value === null) {
+    return value;
+  }
+
+  if (!isLocalEncryptedString(value)) {
+    return value;
+  }
+
+  const [prefix, ivText, encryptedText] = value.split(":");
+  if (prefix !== LOCAL_CRYPTO_PREFIX || !ivText || !encryptedText) {
+    return null;
+  }
+
+  try {
+    const key = await resolveLocalCryptoKey();
+    const decryptedBuffer = await crypto.subtle.decrypt(
+      {
+        name: "AES-GCM",
+        iv: toArrayBuffer(base64UrlToBytes(ivText))
+      },
+      key,
+      toArrayBuffer(base64UrlToBytes(encryptedText))
+    );
+
+    return new TextDecoder().decode(decryptedBuffer);
+  } catch {
+    return null;
+  }
+}