title: pyOpenSSL's PKCS7 object provide very little information, how can I get the sha1 digest of the public key in the signature
body: <p>I would like to parse android apk's CERT.RSA in Python.
  I know it can be parsed with pyOpenSSL </p>
  
  <pre><code>import OpenSSL
  </code></pre>
  
  <p><s>cert = OpenSSL.crypto.load_certificate(OpenSSL.crypto.FILETYPE_ASN1, 
      open('CERT.RSA', 'rb').read())</s></p>
  
  <pre><code>cert = OpenSSL.crypto.load_pkcs7_data(type, buffer)
  </code></pre>
  
  <p>cert is of type 'OpenSSL.crypto.PKCS7'.</p>
  
  <p>BUT right now PKCS7 object is not complete, I cannot get attributes I need, is there any alternative way to parse that file?</p>