Python 密碼學：創建由現有 CA 簽名的證書，並導出

Question

我正在創建一個像這樣的 CA：

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

這給了我兩個 PEM 文件。

然后我調用這個函數，其中cert_authority和private_key是上面生成的數據的字符串。

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，這會生成似乎是證書的內容，但是將數據復制並粘貼到文件中（並按http://srdevspot.blogspot.com/2011/08/openssl-error0906d064pem包裝 64 行並使用 Unix 換行符。 html ) 嘗試驗證時出現此錯誤：

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

希望我錯過了一些簡單的東西，因為我是這一切的新手！

最后我會注意到，如果密碼學不是最好的，我願意使用另一個加密庫。

編輯：

現在根據保羅非常有用的回應使用這個：

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

這是保存文件並將創建的證書和私鑰作為 PEM 字符串返回的正確方法嗎？

我還發現，當我嘗試使用openssl verify -verbose -CAfile ca.crt -untrusted phone_cert.pem針對保存的 PEM 驗證創建的證書時，該命令永遠不會返回 - 可能是一個單獨的問題，但會感謝任何想法。

Answer 1

我在這里看到了兩個問題。 首先，您正在創建另一個自簽名證書，因此您生成的證書不是由 CA 簽名的，它本身就是一個 CA。 要糾正此問題，您需要使用 CA 的私鑰（例如，在您的示例中為private_key ）進行簽名，但您需要創建一個與新證書關聯的新私鑰，並將其公鑰嵌入到證書中。

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)

您的輸出也有問題，因為您試圖從打印語句中復制和粘貼內容。 cert.public_bytes(serialization.Encoding.PEM)的輸出將是一個有效的 X509 證書，帶有分隔符和正確的 PEM 行長度，因此將其直接寫入文件：

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

結果可以用openssl x509 -noout -text -in cert.crt

這是一個完整的示例，它利用cryptography創建自簽名根 CA 並使用該 CA 簽署證書。

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

因為我是新手，所以我必須發布一個答案，還不能發表評論🙄

我非常依賴 Pauls 的回答來進行我自己的實施，這非常有用且很有幫助。 但是我必須在 CA 證書上再添加一個擴展名，以便openssl verify -verbose -CAfile ca.crt client.crt正常工作。

將.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())

其他一切都像保羅一樣。