python - 如何使用 python 解码 SSL 证书？

Question

如何使用 Python 解码 pem 编码 (base64) 证书？例如这里来自 github.com:

-----BEGIN CERTIFICATE-----
MIIHKjCCBhKgAwIBAgIQDnd2il0H8OV5WcoqnVCCtTANBgkqhkiG9w0BAQUFADBp
MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3
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MQswCQYDVQQGEwJVUzETMBEGA1UECBMKQ2FsaWZvcm5pYTEWMBQGA1UEBxMNU2Fu
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n2Xkw9dJh1tybLEvrG8=
-----END CERTIFICATE-----

根据ssl-shopper它应该是这样的:

Common Name: github.com
Subject Alternative Names: github.com, www.github.com
Organization: GitHub, Inc.
Locality: San Francisco
State: California
Country: US
Valid From: May 26, 2011
Valid To: July 29, 2013

如何使用 python 获取此明文？

Answer 1

即使在最新版本中，Python 的标准库也不包含任何可以解码 X.509 证书的内容。但是，附加组件 cryptography包确实支持这一点。引用 example from the documentation :

>>> from cryptography import x509
>>> from cryptography.hazmat.backends import default_backend
>>> cert = x509.load_pem_x509_certificate(pem_data, default_backend())
>>> cert.serial_number
2

另一个可以选择的附加包是pyopenssl .这是围绕 OpenSSL C API 的一个薄包装，这意味着它可能做你想做的事，但预计要花几天时间在文档上撕下你的头发。

如果您无法安装 Python 附加包，但您有 openssl 命令行实用程序，

import subprocess
cert_txt = subprocess.check_output(["openssl", "x509", "-text", "-noout", 
                                    "-in", certificate])

应该产生与您从 cert_txt 中的网络实用程序获得的内容大致相同的内容。

顺便说一句，直接进行 base64 解码为您提供二进制 gobbledygook 的原因是这里有两层编码。 X.509 certificates是 ASN.1数据结构，序列化为 X.690 DER格式，然后，由于 DER 是二进制格式，base64-armored 以便于文件传输。 (这方面的许多标准都是在 90 年代编写的，当时除了 7 位 ASCII 外，您无法可靠地发布任何东西。)