Why does OAuth2 authentication work on home machine but not on a server?

Question

I'm struggling to get OAuth2 authorisation to work on a script I'm working on when I run it on an EC2 Linux server instance (running Ubuntu 13.04). The relevant snippet is:

with open('creds.txt') as f:
    creds = {}
    for line in f:
        creds[line.split(',')[0]] = line.split(',')[1].rstrip('\n')

self.client_id = creds['client_id']
self.client_secret = creds['client_secret']
self.username = creds['username']
self.password = creds['password'])

token_response = requests.post(
    "https://example.com/oauth2/access_token/", 
    data={
        "grant_type": "password",
        "client_id": self.client_id,
        "client_secret": self.client_secret,
        "username": self.username,
        "password": self.password,
        "scope": "read+write"}).json()

It runs fine on my home computer (running Windows 7), just not when I try and run it remotely where I get: {u'error': u'invalid_client'}.

I've tried setting up a new client ID and secret and still get the same response.

• Why does it work differently on a remote server to on my own machine?
• Does it matter on which machine the application was created (see comment)? - I eliminated this possibility by successfully authenticating using CURL in both environments.

The only thing I can think of now is that perhaps the requests library handles the POST request differently on Ubuntu. Does anyone know if this is the case?

Answer 1

This is probably the first thing I should have thought of when there's a difference between Nix and Windows environments:

Always check the EOL chars!

The problem was that when grabbing the username, password, etc. from my credentials file, I was stripping the newline character using string.rstrip('\n'), so in the Unix environment that was leaving an \r carriage return character behind which was then being passed as part of the POST request.

The simple and correct solution which works in both environments is to use string.rstrip() which strips all trailing whitespace and end of line chars.