[python] AES-GCM加解密函数

代码片段：

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
import base64

def string_to_uint8_array(data: str) -> bytes:
    """将字符串转换为字节数组 (类似 JavaScript 的 stringToUint8Array)"""
    return data.encode()

def aes_gcm_encrypt_fixed(key: bytes, plaintext: str, nonce: bytes, associated_data: bytes) -> dict:
    """
    使用固定密钥、随机数、关联数据的 AES-GCM 加密
    :param key: 密钥 (16, 24, or 32 bytes)
    :param plaintext: 明文字符串
    :param nonce: 随机数 (IV, 12 bytes)
    :param associated_data: 关联数据 (AAD)
    :return: 包含密文和认证标签的字典
    """
    aes_gcm = Cipher(algorithms.AES(key), modes.GCM(nonce), backend=default_backend()).encryptor()

    if associated_data:
        aes_gcm.authenticate_additional_data(associated_data)

    ciphertext = aes_gcm.update(string_to_uint8_array(plaintext)) + aes_gcm.finalize()

    return {
        "ciphertext": ciphertext,
        "tag": aes_gcm.tag,
    }

def aes_gcm_decrypt_fixed(key: bytes, ciphertext: bytes, nonce: bytes, tag: bytes, associated_data: bytes) -> str:
    """
    使用固定密钥、随机数、关联数据的 AES-GCM 解密
    :param key: 密钥
    :param ciphertext: 密文
    :param nonce: 随机数 (IV, 12 bytes)
    :param tag: 认证标签
    :param associated_data: 关联数据 (AAD)
    :return: 解密后的明文字符串
    """
    aes_gcm = Cipher(algorithms.AES(key), modes.GCM(nonce, tag), backend=default_backend()).decryptor()

    if associated_data:
        aes_gcm.authenticate_additional_data(associated_data)

    plaintext = aes_gcm.update(ciphertext) + aes_gcm.finalize()

    return plaintext.decode()

# 测试代码

if __name__ == "__main__":
    # 固定密钥（与 JavaScript 中的 "r*************" 对应）
    key = string_to_uint8_array("r**********")  # 必须是 16 字节
    # 固定随机数（与 JavaScript 中的 Uint8Array([107, -6, -128, -1, ...]) 对应）
    nonce = bytes([107, 250, 128, 255, 71, 217, 212, 105, 222, 129, 215, 168])
    # 固定附加数据（与 JavaScript 中的 Uint8Array([97, 115, ...]) 对应）
    associated_data = bytes([97, 115, 115, 111, 99, 105, 97, 116, 105, 111, 110])

    plaintext = "123456"  # 明文字符串

    # 加密
    encrypted_data = aes_gcm_encrypt_fixed(key, plaintext, nonce, associated_data)
    print(f"Ciphertext (Base64): {base64.b64encode(encrypted_data['ciphertext']).decode()}")
    print(f"Tag (Base64): {base64.b64encode(encrypted_data['tag']).decode()}")
    res = base64.b64encode(encrypted_data['ciphertext']).decode() +base64.b64encode(encrypted_data['tag']).decode()
    print("final:",res)
    # 解密
    decrypted_text = aes_gcm_decrypt_fixed(
        key,
        encrypted_data['ciphertext'],
        nonce,
        encrypted_data['tag'],
        associated_data,
    )
    print(f"Decrypted Text: {decrypted_text}")