Python 密码学：创建由现有 CA 签名的证书，并导出

Question

我正在创建一个像这样的 CA：

openssl genrsa -out ca.key 4096
openssl req -new -x509 -days 3650 -key ca.key -out ca.cert

这给了我两个 PEM 文件。

然后我调用这个函数，其中cert_authority和private_key是上面生成的数据的字符串。

def create_cert(cert_authority, private_key):
    one_day = datetime.timedelta(1, 0, 0)
    # Use our private key to generate a public key
    private_key = serialization.load_pem_private_key(
        private_key.encode("ascii"), password=None, backend=default_backend()
    )
    public_key = private_key.public_key()

    ca = x509.load_pem_x509_certificate(
        cert_authority.encode("ascii"), default_backend()
    )

    builder = x509.CertificateBuilder()
    builder = builder.subject_name(
        x509.Name([x509.NameAttribute(NameOID.COMMON_NAME, u"cryptography.io")])
    )
    builder = builder.issuer_name(ca.issuer)
    builder = builder.not_valid_before(datetime.datetime.today() - one_day)
    builder = builder.not_valid_after(datetime.datetime.today() + (one_day * 30))
    builder = builder.serial_number(x509.random_serial_number())
    builder = builder.public_key(public_key)

    cert = builder.sign(
        private_key=private_key, algorithm=hashes.SHA256(), backend=default_backend()
    )

    print(cert.public_bytes(serialization.Encoding.PEM))

然后，这会生成似乎是证书的内容，但是将数据复制并粘贴到文件中（并按照http://srdevspot.blogspot.com/2011/08/openssl-error0906d064pem包装 64 行并使用 Unix 换行符。 html ) 尝试验证时出现此错误：

$ openssl verify -CAfile ca.crt -untrusted phone.crt
unable to load certificates

希望我错过了一些简单的东西，因为我是这一切的新手！

最后我会注意到，如果密码学不是最好的，我愿意使用另一个加密库。

编辑：

现在根据保罗非常有用的回应使用这个：

def create_cert(cert_authority, private_key):
    one_day = datetime.timedelta(1, 0, 0)
    # Use our private key to generate a public key
    root_key = serialization.load_pem_private_key(
        private_key.encode("ascii"), password=None, backend=default_backend()
    )

    root_cert = x509.load_pem_x509_certificate(
        cert_authority.encode("ascii"), default_backend()
    )

    # Now we want to generate a cert from that root
    cert_key = rsa.generate_private_key(
        public_exponent=65537, key_size=2048, backend=default_backend()
    )
    new_subject = x509.Name(
        [
            x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u"Texas"),
            x509.NameAttribute(NameOID.LOCALITY_NAME, u"Austin"),
            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u"New Org Name!"),
        ]
    )
    cert = (
        x509.CertificateBuilder()
        .subject_name(new_subject)
        .issuer_name(root_cert.issuer)
        .public_key(cert_key.public_key())
        .serial_number(x509.random_serial_number())
        .not_valid_before(datetime.datetime.utcnow())
        .not_valid_after(datetime.datetime.utcnow() + datetime.timedelta(days=30))
        .add_extension(
            x509.SubjectAlternativeName([x509.DNSName(u"somedomain.com")]),
            critical=False,
        )
        .sign(root_key, hashes.SHA256(), default_backend())
    )

    # Dump to scratch
    with open("scratch/phone_cert.pem", "wb") as f:
        f.write(cert.public_bytes(encoding=serialization.Encoding.PEM))

    # Return PEM
    cert_pem = cert.public_bytes(encoding=serialization.Encoding.PEM)

    cert_key_pem = cert_key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.TraditionalOpenSSL,
        encryption_algorithm=serialization.NoEncryption(),
    )

    return cert_pem, cert_key_pem

这是保存文件并将创建的证书和私钥作为 PEM 字符串返回的正确方法吗？

我还发现，当我尝试使用openssl verify -verbose -CAfile ca.crt -untrusted phone_cert.pem该命令针对保存的 PEM 验证创建的证书时，该命令永远不会返回——可能是一个单独的问题，但会感谢任何想法。

Answer 1

我在这里看到了两个问题。首先，您正在创建另一个自签名证书，因此您生成的证书不是由 CA 签名的，它本身就是一个 CA。要更正此问题，您需要使用 CA 的私钥进行签名（例如private_key在您的示例中），但您需要创建一个与新证书关联的新私钥，并将其公钥嵌入到证书中。

certificate_private_key = <generate an ec or rsa key here>
certificate_public_key = certificate_private_key.public_key()

然后做

builder = builder.public_key(certificate_public_key)

您的输出也有问题，因为您试图从打印语句中复制和粘贴内容。的输出cert.public_bytes(serialization.Encoding.PEM)将是带有分隔符和正确 PEM 行长度的有效 X509 证书，因此将其直接写入文件：

with open("cert.crt", "wb") as f:
    f.write(cert.public_bytes(serialization.Encoding.PEM))

结果可以解析为 openssl x509 -noout -text -in cert.crt

这是一个完整的示例，cryptography用于创建自签名根 CA 并使用该 CA 签署证书。

import datetime

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


root_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048,
    backend=default_backend()
)
subject = issuer = x509.Name([
    x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
    x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u"Texas"),
    x509.NameAttribute(NameOID.LOCALITY_NAME, u"Austin"),
    x509.NameAttribute(NameOID.ORGANIZATION_NAME, u"My Company"),
    x509.NameAttribute(NameOID.COMMON_NAME, u"My CA"),
])
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.utcnow()
).not_valid_after(
    datetime.datetime.utcnow() + datetime.timedelta(days=3650)
).sign(root_key, hashes.SHA256(), default_backend())

# Now we want to generate a cert from that root
cert_key = rsa.generate_private_key(
    public_exponent=65537,
    key_size=2048,
    backend=default_backend()
)
new_subject = x509.Name([
    x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
    x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u"Texas"),
    x509.NameAttribute(NameOID.LOCALITY_NAME, u"Austin"),
    x509.NameAttribute(NameOID.ORGANIZATION_NAME, u"New Org Name!"),
])
cert = x509.CertificateBuilder().subject_name(
    new_subject
).issuer_name(
    root_cert.issuer
).public_key(
    cert_key.public_key()
).serial_number(
    x509.random_serial_number()
).not_valid_before(
    datetime.datetime.utcnow()
).not_valid_after(
datetime.datetime.utcnow() + datetime.timedelta(days=30)
).add_extension(
    x509.SubjectAlternativeName([x509.DNSName(u"somedomain.com")]),
    critical=False,
).sign(root_key, hashes.SHA256(), default_backend())

Answer 2

我必须发布答案，因为我是新手，还不能发表评论

我非常依赖 Pauls 的回答来进行我自己的实施，这非常有用且很有帮助。但是我必须在 CA 证书上再添加一个扩展名openssl verify -verbose -CAfile ca.crt client.crt才能正常工作。

添加.add_extension(x509.BasicConstraints(ca=True, path_length=None), critical=True)到根 CertificateBuilder 就可以了。

ca_crt = x509.CertificateBuilder() \
    .subject_name(subject) \
    .issuer_name(issuer) \
    .public_key(ca_key.public_key()) \
    .serial_number(x509.random_serial_number()) \
    .not_valid_before(datetime.datetime.today() - one_day) \
    .not_valid_after(datetime.datetime.today() + (one_day * 365)) \
    .add_extension(x509.BasicConstraints(ca=True, path_length=None), critical=True) \
    .sign(ca_key, hashes.SHA256(), default_backend())

其他一切都像保罗一样。