Question

I am trying access a REST API.

I can get it working in Curl/REST Client (the UI tool), with preemptive authentication enabled.

But, using urllib2, it doesn’t seem to support this by default and I can’t find a way to turn it on.

Thanks 🙂

Answer 1

Here’s a simple Preemptive HTTP basic auth handler, based on the code from urllib2.HTTPBasicAuthHandler. It can be used in the exact same manner, except an Authorization header will be added to every request with a matching URL. Note that this handler should be used with a HTTPPasswordMgrWithDefaultRealm. That’s because there is no realm coming back in a WWW-Authenticate challenge since you’re being preemptive.

class PreemptiveBasicAuthHandler(urllib2.BaseHandler):

        def __init__(self, password_mgr=None):
                if password_mgr is None:
                        password_mgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
                self.passwd = password_mgr
                self.add_password = self.passwd.add_password

        def http_request(self,req):
                uri = req.get_full_url()
                user, pw = self.passwd.find_user_password(None,uri)
                #logging.debug('ADDING REQUEST HEADER for uri (%s): %s:%s',uri,user,pw)
                if pw is None: return req

                raw = "%s:%s" % (user, pw)
                auth = 'Basic %s' % base64.b64encode(raw).strip()
                req.add_unredirected_header('Authorization', auth)
                return req