使用pyca/cryptography生成和管理X.509证书的完整指南-优快云博客

本文链接：https://blog.youkuaiyun.com/gitblog_01039/article/details/148464915

使用pyca/cryptography生成和管理X.509证书的完整指南

cryptography cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. 项目地址: https://gitcode.com/gh_mirrors/cr/cryptography

X.509证书基础概念

X.509证书是互联网安全通信的基础设施，主要用于客户端和服务器的身份验证。最常见的应用场景就是HTTPS网站的安全连接。证书通过公钥基础设施(PKI)体系建立信任链，确保通信双方的身份真实可靠。

证书签名请求(CSR)生成流程

在实际应用中，我们通常需要向证书颁发机构(CA)申请证书，这个过程需要先生成证书签名请求(CSR)。以下是完整的CSR生成步骤：

生成密钥对：首先需要创建公钥/私钥对
创建CSR：使用私钥签名生成证书请求
提交CA：将CSR(不含私钥)发送给证书颁发机构
验证身份：CA验证申请者对域名的所有权
获取证书：CA颁发签名后的证书
部署使用：在服务器上配置证书和私钥

实际操作示例

from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography import x509
from cryptography.x509.oid import NameOID
from cryptography.hazmat.primitives import hashes

# 生成RSA私钥
key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048,
)

# 保存私钥到文件(建议加密存储)
with open("private_key.pem", "wb") as f:
    f.write(key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.TraditionalOpenSSL,
        encryption_algorithm=serialization.BestAvailableEncryption(b"your_password"),
    ))

# 创建CSR
csr = x509.CertificateSigningRequestBuilder().subject_name(x509.Name([
    x509.NameAttribute(NameOID.COUNTRY_NAME, "CN"),
    x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, "Beijing"),
    x509.NameAttribute(NameOID.ORGANIZATION_NAME, "My Organization"),
    x509.NameAttribute(NameOID.COMMON_NAME, "example.com"),
])).add_extension(
    x509.SubjectAlternativeName([
        x509.DNSName("example.com"),
        x509.DNSName("www.example.com"),
    ]),
    critical=False,
).sign(key, hashes.SHA256())

# 保存CSR
with open("csr.pem", "wb") as f:
    f.write(csr.public_bytes(serialization.Encoding.PEM))

自签名证书的创建

自签名证书虽然不被公共CA信任，但在开发和测试环境中非常有用。创建过程与CSR类似，但需要自己完成签名环节。

import datetime

# 生成自签名证书
subject = issuer = x509.Name([
    x509.NameAttribute(NameOID.COUNTRY_NAME, "CN"),
    x509.NameAttribute(NameOID.ORGANIZATION_NAME, "Test Org"),
    x509.NameAttribute(NameOID.COMMON_NAME, "localhost"),
])

cert = x509.CertificateBuilder().subject_name(
    subject
).issuer_name(
    issuer
).public_key(
    key.public_key()
).serial_number(
    x509.random_serial_number()
).not_valid_before(
    datetime.datetime.now(datetime.timezone.utc)
).not_valid_after(
    datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(days=365)
).add_extension(
    x509.SubjectAlternativeName([x509.DNSName("localhost")]),
    critical=False,
).sign(key, hashes.SHA256())

# 保存证书
with open("certificate.pem", "wb") as f:
    f.write(cert.public_bytes(serialization.Encoding.PEM))

构建完整的CA证书体系

在企业内部或测试环境中，我们可能需要构建自己的CA体系。这通常包括根CA、中间CA和终端实体证书三级结构。

1. 创建根CA证书

root_key = ec.generate_private_key(ec.SECP256R1())

root_cert = x509.CertificateBuilder().subject_name(
    subject
).issuer_name(
    issuer
).public_key(
    root_key.public_key()
).serial_number(
    x509.random_serial_number()
).not_valid_before(
    datetime.datetime.now(datetime.timezone.utc)
).not_valid_after(
    datetime.datetime.now(datetime.timezone.utc) + datetime.timedelta(days=365*10)
).add_extension(
    x509.BasicConstraints(ca=True, path_length=None),
    critical=True,
).add_extension(
    x509.KeyUsage(
        digital_signature=True,
        key_cert_sign=True,
        crl_sign=True,
    ),
    critical=True,
).sign(root_key, hashes.SHA256())

2. 创建中间CA证书

int_key = ec.generate_private_key(ec.SECP256R1())

int_cert = x509.CertificateBuilder().subject_name(
    subject
).issuer_name(
    root_cert.subject
).public_key(
    int_key.public_key()
).add_extension(
    x509.BasicConstraints(ca=True, path_length=0),
    critical=True,
).sign(root_key, hashes.SHA256())

3. 颁发终端实体证书

ee_key = ec.generate_private_key(ec.SECP256R1())

ee_cert = x509.CertificateBuilder().subject_name(
    subject
).issuer_name(
    int_cert.subject
).public_key(
    ee_key.public_key()
).add_extension(
    x509.BasicConstraints(ca=False, path_length=None),
    critical=True,
).add_extension(
    x509.KeyUsage(
        digital_signature=True,
        key_encipherment=True,
    ),
    critical=True,
).sign(int_key, hashes.SHA256())

证书验证与密钥类型判断

在实际应用中，我们经常需要验证证书链的有效性，以及判断证书使用的密钥类型。

证书链验证

store = Store([root_cert])
builder = PolicyBuilder().store(store)
verifier = builder.build_server_verifier(DNSName("example.com"))
chain = verifier.verify(ee_cert, [int_cert])

密钥类型判断

public_key = cert.public_key()
if isinstance(public_key, rsa.RSAPublicKey):
    # RSA密钥处理逻辑
elif isinstance(public_key, ec.EllipticCurvePublicKey):
    # ECC密钥处理逻辑
else:
    # 其他密钥类型处理