CSR X509 Extensions

Asked by Michal Kwiatkowski

How can I get x509 Extenstions from a CSR using pyOpenSSL?
I need to get Subject Alternative Names, but as far, all I can read from CSR is public key and subject.
I've googled no reasonable solution.
Any suggestions?

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Jean-Paul Calderone (exarkun) said :
#1

pyOpenSSL does not expose the OpenSSL APIs for inspecting X509Req extensions. To do what you want, bindings for these OpenSSL APIs need to be added to pyOpenSSL.

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Stephen Holsapple (sholsapp) said :
#2

It doesn't appear any progress has been made on this since the last update and I'm willing to add the bindings. Can someone kick me off in the right direction? Should I use x509.c as a template?

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Adi Roiban (adiroiban) said :
#3

pyopenssl was changed recently and is now a pure Python project. Development was moved at https://github.com/pyca/pyopenssl

The low level stuff was moved into a separate project called: cryptography https://github.com/pyca/cryptography

OpenSSL bindings are here: https://github.com/pyca/cryptography/tree/master/cryptography/hazmat/bindings/openssl

The C binding part is now handled by cffi http://cffi.readthedocs.org/en/release-0.8/

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Pascal Louis-Marie (plouismarie) said :
#4

Who read that 4 years after... ME!

And I want to share my working python3 code to decode a CSR.
It displays the alt name list too, this code works in flask :

@app.route("/Csrcheck",methods=['GET', 'POST'])
def csrcheck():
  csr=request.form['csrcontent'] # you can here replace the csr value by the CSR hash straight here
  if csr == "":
    return "please populate the csr first and try again"
  if "CERTIFICATE" not in csr:
    return "The csr syntax looks bogus, please review and try again"
  else:
    try:
      req = load_certificate_request(FILETYPE_PEM, csr)
      subject = req.get_subject()
      altname = req.get_extensions()
      listaltname=''
      for elem in altname:
        listaltname+=str(elem).split('DNS:')[1]+' '
      components = dict(subject.get_components())
      result="<b>Common name</b> : {} <br> \
              <b>Alt name</b> : {} <br> \
              <b>Organisation</b> : {} <br> \
              <b>Organisation unit</b> : {} <br>\
              <b>City</b> : {} <br>\
              <b>State</b> : {} <br>\
              <b>Country</b> : {} <br>\ ".format(components[b'CN'].decode(),listaltname,components[b'O'].decode(),components[b'OU'].decode(),components[b'L'].decode(),components[b'ST'].decode(),components[b'C'].decode())
      myhtml=" Here is the content of the populated CSR : <br>" + result
      return myhtml
    except OpenSSL.crypto.Error:
      return 'Could not extract CSR content, please review and try again'

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