Interfacing to the LinkPoint API with Python - Sending XML Over SSL with Authentication

Question

I'm trying to make a successful connection to the LinkPoint gateway using Python. For those of you unfamiliar with their API you get a .pem file you use for authentication purposes.

I'm having trouble using this file and creating a secure connection over SSL.

According to their API documentation (which leaves a lot to be desired, btw) I believe the configuration should look similar to below:

HOST = 'secure.linkpt.net'
API_URL = 'https://secure.linkpt.net/lpc/servlet/lppay'
PORT = 1129
cert_key = my_cert_key.pem

Using this information and a valid XML string how can I create this connection?

I'm pretty new to HTTP connections in Python. I've successfully implemented connections with other APIs using a POST with urllib2. Naturally, my first attempt started with a similar approach hoping I could stumble on to a solution.

Something like:

headers = { 'User-Agent'     : 'Rico',
            'Content-type'   : 'text/xml; charset=\"UTF-8\"',
            'Content-length' : len(self.xml_string),
          }

# POST to First Data (Link Point)
req = urllib2.Request(API_URL, self.xml_string, headers)
response = urllib2.urlopen(req)
self.handleResponse(response.read())

I had little hopes this would work as I didn't provide anything about the cert_key or the PORT.

After this attempt I tried to use a similar approach as I found from a solution from another stackoverflow post. Unfortunately I wasn't able to get far with this as I don't have ca_certs or cert files (that I know of).

I've tried to use Requests but can't find the documentation/examples for me to make sense of it.

I've also tried to use Twisted, and I really hoped I could do something with this but this feels like trying to open a door with a wrecking ball. It just feels like overkill to me. I just need a simple connection/request/response...this seems overly complicated for that.

My next attempt was going to be PycURL, but have confronted enough despair during this process I thought I'd come here to see if someone had some good suggestions before diving into this.

If you think I should re-visit one of these tools please let me know. I didn't spend a great deal of time with any of these - just enough to get my feet wet. If you could also point me to a good example or detailed documentation that would be fantastic.

Also, I'd prefer not to use the standard SSL library to build the connection myself - I don't want to reinvent the wheel if I don't have to.

Answer 1

The solution I was able to use to get a valid connection was using httplib as follows:

import httplib

HOST = 'staging.linkpt.net'
API_URL = '/lpc/servlet/lppay'
PORT = 1129
CERTFILE = 'my_cert_file.pem'

headers = { 'User-Agent'     : 'Rico',
            'Content-type'   : 'text/xml; charset=\"UTF-8\"',
            'Content-length' : len(xml_str),
          }

conn = httplib.HTTPSConnection(HOST, PORT, cert_file = CERTFILE)
conn.putrequest("POST", API_URL)
conn.putheader(headers)
conn.endheaders()
conn.send(xml_str)
response = conn.getresponse()

I have yet been able to generate a valid request. Apparently I interpreted the API documentation incorrectly and keep getting a Malformed or unrecognized request. but at least I'm making the connection.

I'll update this answer if I'm able to determine more useful information regarding this subject.

UPDATE: A Link Point customer service employee told me I was using old API documentation. I've since tried with the newer version and still cannot connect. I can't even get a response from their server. This is no longer a possible solution to this problem.

UPDATE 2: I was able to solve this problem in another post SSL Connection Using .pem Certificate With Python

Enjoy!