How can I decode a SSL certificate using python?

Question

How can I decode a pem-encoded (base64) certificate with Python? For example this here from github.com:

-----BEGIN CERTIFICATE-----
MIIHKjCCBhKgAwIBAgIQDnd2i         


        

Answer 1

You can use pyasn1 and pyasn1-modules packages to parse this kind of data. For instance:

from pyasn1_modules import pem, rfc2459
from pyasn1.codec.der import decoder

substrate = pem.readPemFromFile(open('cert.pem'))
cert = decoder.decode(substrate, asn1Spec=rfc2459.Certificate())[0]
print(cert.prettyPrint())

Read the docs for pyasn1 for the rest.