Function encryptString

apps/api/src/lib/crypto/aes-gcm.utils.ts:56–81

(plaintext: string)

 * base64). The IV is fresh per call; never reuse a (key, iv) pair.
 */
export const encryptString = (plaintext: string): string => {
  const key = decodeKey(env.MFA_ENCRYPTION_KEY);
  const iv = randomBytes(AES_GCM_IV_BYTES);
  /*
   * Pinning `authTagLength` matters on decrypt — a missing option lets
   * Node accept a shorter-than-expected tag, which an attacker could
   * use to forge ciphertext. We pass it on encrypt too so the value
   * the cipher emits and the value the decipher will verify are the
   * same constant.
   */
  const cipher = createCipheriv(CIPHER_ALGORITHM, key, iv, {
    authTagLength: AES_GCM_TAG_BYTES,
  });
  const ciphertext = Buffer.concat([
    cipher.update(plaintext, "utf8"),
    cipher.final(),
  ]);
  const tag = cipher.getAuthTag();

  return [
    CIPHERTEXT_VERSION,
    iv.toString("base64"),
    ciphertext.toString("base64"),
    tag.toString("base64"),
  ].join("$");
};

/**
 * Inverse of `encryptString`. Throws on any failure (bad version,