Here's a simple example using the urllib2 interface. First create an SSL context to set verification of the peer:
>>> from OpenSSL import SSL >>> ctx = SSL.Context(SSL.SSLv3_METHOD) >>> verify_callback = lambda conn, x509, errnum, errdepth, preverify_ok: preverify_ok >>> ctx.set_verify(SSL.VERIFY_PEER, verify_callback) >>> ctx.load_verify_locations(None, './cacerts')
Create an opener adding in the context object and GET the URL. The custom build opener adds in a new PyOpenSSL based HTTPSContextHandler.
>>> from ndg.httpsclient.urllib2_build_opener import build_opener >>> opener = build_opener(ssl_context=ctx) >>> res = opener.open('https://localhost/') >>> print res.read()
The above verify callback above is just a placeholder. For more a comprehensive implementation ndg_httpsclient includes a callback with support for checking of the peer FQDN against the subjectAltName in the certificate. If subjectAltName is absent, it defaults to an attempted match against the certificate subject CommonName.
The callback is implemented as a class which is a callable. This means that you can instantiate it, configuring the required settings and then pass the resulting object direct to the context's set_verify:
>>> from ndg.httpsclient.ssl_peer_verification import ServerSSLCertVerification >>> verify_callback = ServerSSLCertVerification(hostname='localhost')
To get the subjectAltName support I needed pyasn1 with some help from this query to correctly parse the relevant certificate extension. So adding this into the context creation steps above:
>>> from OpenSSL import SSL >>> ctx = SSL.Context(SSL.SSLv3_METHOD) >>> verify_callback =
>>> ctx.set_verify(SSL.VERIFY_PEER, verify_callback) >>> ctx.load_verify_locations(None, './cacerts')
The package will work without pyasn1 but then you loose the subjectAltName support. Warning messages will flag this up. I can pass this context object to the urllib2 style opener as before, or using the httplib interface:
>>> from ndg.httpsclient.https import HTTPSConnection >>> conn = HTTPSConnection('localhost', port=4443, ssl_context=ctx) >>> conn.connect() >>> conn.request('GET', '/') >>> resp = conn.getresponse() >>> resp.read()
A big thank you to Richard for his help getting this package written and ready for use. Amongst other things he's added a suite of convenience wrapper functions and a command line script.