Python中从PFX提取证书与密钥后如何写入文件？

你已经通过pkcs12.load_key_and_certificates获取到了x509.Certificate类型的证书对象、私钥以及附加证书，要将它们转换为字符串并写入文件，可按以下步骤操作：

处理证书（写入x.crt） #

x509.Certificate对象可以通过public_bytes()方法导出为PEM格式的字节流，再转成字符串写入文件：

from cryptography.hazmat.primitives import serialization

# 将证书转为PEM格式的字符串
cert_pem = certificate.public_bytes(
    encoding=serialization.Encoding.PEM
).decode("utf-8")

# 写入x.crt文件
with open("x.crt", "w") as f:
    f.write(cert_pem)

如果需要把附加证书也写入同一文件，可以遍历additional_certificates列表，逐个转换后追加：

# 写入主证书
with open("x.crt", "w") as f:
    f.write(cert_pem)
    # 追加附加证书
    for cert in additional_certificates:
        cert_add_pem = cert.public_bytes(encoding=serialization.Encoding.PEM).decode("utf-8")
        f.write(cert_add_pem)

处理私钥（写入x.key） #

私钥对象（通常是RSAPrivateKey或其他私钥类型）可以通过private_bytes()方法导出为PEM格式：

# 将私钥转为PEM格式的字符串
key_pem = private_key.private_bytes(
    encoding=serialization.Encoding.PEM,
    format=serialization.PrivateFormat.PKCS8,
    encryption_algorithm=serialization.NoEncryption()
).decode("utf-8")

# 写入x.key文件
with open("x.key", "w") as f:
    f.write(key_pem)

完整示例代码 #

把读取PFX和导出的逻辑整合起来：

from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.serialization import pkcs12

# 读取PFX文件
with open("your_file.pfx", "rb") as pxfile:
    private_key, certificate, additional_certificates = pkcs12.load_key_and_certificates(
        pxfile.read(),
        password=None,  # 如果PFX有密码，替换为b"your_password"
        backend=default_backend()
    )

# 导出证书到x.crt
cert_pem = certificate.public_bytes(encoding=serialization.Encoding.PEM).decode("utf-8")
with open("x.crt", "w") as f:
    f.write(cert_pem)
    for cert in additional_certificates:
        f.write(cert.public_bytes(encoding=serialization.Encoding.PEM).decode("utf-8"))

# 导出私钥到x.key
key_pem = private_key.private_bytes(
    encoding=serialization.Encoding.PEM,
    format=serialization.PrivateFormat.PKCS8,
    encryption_algorithm=serialization.NoEncryption()
).decode("utf-8")
with open("x.key", "w") as f:
    f.write(key_pem)

内容的提问来源于stack exchange，提问作者nick