How to decode CSR using pyOpenssl

Question

Get a string from the web page as it

-----BEGIN NEW CERTIFICATE REQUEST-----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-----END NEW CERTIFICATE REQUEST-----

How to decode it to plaintext like

Certificate information
Common name: www.xxx.net
Organization:xxx.net
Organizational unit:xxx.net
City/locality:bj
State/province:bj
Country:CN
Signature algorithm:SHA1
Key algorithm:RSA
Key size:1024

I know there is a third party pyopenssl, but not sure how to handle string buffer from web front-end. Or do you have any better idea? Thanks

mhawke · Accepted Answer · 2015-05-19T03:33:10.433

You can load the certificate using OpenSSL.crypto.load_certificate_request() and then access the key and subject details from there, e.g.

import OpenSSL.crypto
from OpenSSL.crypto import load_certificate_request, FILETYPE_PEM

csr = '''-----BEGIN NEW CERTIFICATE REQUEST-----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-----END NEW CERTIFICATE REQUEST-----'''

req = load_certificate_request(FILETYPE_PEM, csr)
key = req.get_pubkey()
key_type = 'RSA' if key.type() == OpenSSL.crypto.TYPE_RSA else 'DSA'
subject = req.get_subject()
components = dict(subject.get_components())
print "Common name:", components['CN']
print "Organisation:", components['O']
print "Orgainistional unit", components['OU']
print "City/locality:", components['L']
print "State/province:", components['ST']
print "Country:", components['C']
print "Signature algorithm:", '?'
print "Key algorithm:", key_type
print "Key size:", key.bits()

Unfortunately I don't know how to get the signature algorithm.

Yes,this works for me. thank you, while the Key size seems incorrect here. — Kent, May 19 '15 at 05:51
@kent: that's good. I think that the key size is correct, it's the same as reported by `openssl req -text — mhawke, May 19 '15 at 06:05
yep, using openssl req command the key size is 1024 bit, while run key.bit via pyopenssl, public-key 2048 bit. — Kent, May 19 '15 at 07:41
@kent: that's weird. `key.bits()` gives me 1024 for the CSR in your question. — mhawke, May 19 '15 at 10:53
See also `openssl req -text` and docs at https://www.openssl.org/docs/manmaster/man1/openssl-req.html , which also includes the signature algorithm. — here, Jan 17 '19 at 00:40

How to decode CSR using pyOpenssl

1 Answers1