Python怎样实现代码签名？数字证书验证

cryptography

cryptography

from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import rsa, padding
from cryptography.hazmat.backends import default_backend
from cryptography import x509
from cryptography.hazmat.primitives import serialization
from datetime import datetime, timedelta

# --- 签名方 ---

def generate_key_pair():
    # 实际应用中，私钥需要安全存储，不能直接写在代码里
    private_key = rsa.generate_private_key(
        public_exponent=65537,
        key_size=2048,
        backend=default_backend()
    )
    return private_key, private_key.public_key()

def create_self_signed_cert(private_key, public_key):
    subject = issuer = x509.Name([
        x509.NameAttribute(x509.oid.NameOID.COUNTRY_NAME, u"US"),
        x509.NameAttribute(x509.oid.NameOID.STATE_OR_PROVINCE_NAME, u"California"),
        x509.NameAttribute(x509.oid.NameOID.LOCALITY_NAME, u"San Francisco"),
        x509.NameAttribute(x509.oid.NameOID.ORGANIZATION_NAME, u"MyCompany"),
        x509.NameAttribute(x509.oid.NameOID.COMMON_NAME, u"Code Signer"),
    ])
    cert = (
        x509.CertificateBuilder()
        .subject_name(subject)
        .issuer_name(issuer)
        .public_key(public_key)
        .serial_number(x509.random_serial_number())
        .not_valid_before(datetime.utcnow())
        .not_valid_after(datetime.utcnow() + timedelta(days=365))
        .add_extension(x509.BasicConstraints(ca=True, path_length=None), critical=True)
        .sign(private_key, hashes.SHA256(), default_backend())
    )
    return cert

def sign_data(private_key, data_to_sign):
    hasher = hashes.Hash(hashes.SHA256(), backend=default_backend())
    hasher.update(data_to_sign)
    digest = hasher.finalize()

    signature = private_key.sign(
        digest,
        padding.PSS(
            mgf=padding.MGF1(hashes.SHA256()),
            salt_length=padding.PSS.MAX_LENGTH
        ),
        hashes.SHA256()
    )
    return signature, digest # 返回签名和原始哈希，方便理解

# --- 验证方 ---

def verify_signature(public_key, signed_data, signature):
    hasher = hashes.Hash(hashes.SHA256(), backend=default_backend())
    hasher.update(signed_data)
    digest = hasher.finalize()

    try:
        public_key.verify(
            signature,
            digest,
            padding.PSS(
                mgf=padding.MGF1(hashes.SHA256()),
                salt_length=padding.PSS.MAX_LENGTH
            ),
            hashes.SHA256()
        )
        print("签名验证成功：代码完整且来源可信。")
        return True
    except Exception as e:
        print(f"签名验证失败：{e}。代码可能被篡改或签名无效。")
        return False

# 示例流程
if __name__ == "__main__":
    # 模拟代码内容
    code_content = b"print('Hello, secure world!')\nimport os\n# Some sensitive code..."

    # 1. 签名方生成密钥和自签名证书
    print("--- 签名方操作 ---")
    signer_private_key, signer_public_key = generate_key_pair()
    signer_cert = create_self_signed_cert(signer_private_key, signer_public_key)
    print("密钥对和自签名证书已生成。")

    # 2. 签名代码
    signature, original_digest = sign_data(signer_private_key, code_content)
    print(f"代码已签名，原始哈希: {original_digest.hex()}")

    # 3. 模拟传输（代码、签名、证书）
    # 实际中，这些会以某种方式打包或传输
    received_code = code_content # 假设传输过程中未被篡改
    received_signature = signature
    received_cert_pem = signer_cert.public_bytes(serialization.Encoding.PEM)

    print("\n--- 验证方操作 ---")
    # 4. 验证方加载证书
    loaded_cert = x509.load_pem_x509_certificate(received_cert_pem, default_backend())
    verifier_public_key = loaded_cert.public_key()
    print("证书已加载，公钥已提取。")

    # 5. 验证证书有效性（简单检查）
    if datetime.utcnow() > loaded_cert.not_valid_after or datetime.utcnow() < loaded_cert.not_valid_before:
        print("警告：证书已过期或尚未生效！")
    else:
        print("证书有效期检查通过。")

    # 6. 验证签名
    verify_signature(verifier_public_key, received_code, received_signature)

    # 模拟代码被篡改的情况
    print("\n--- 模拟代码被篡改 ---")
    tampered_code = b"print('Hello, secure world! This is malicious code!')"
    print("代码被篡改，尝试验证...")
    verify_signature(verifier_public_key, tampered_code, received_signature)

cryptography.x509