Python urllib2, basic HTTP authentication, and tr.im

Question

I'm playing around, trying to write some code to use the tr.im APIs to shorten a URL.

After reading http://docs.python.org/library/urllib2.html, I tried:

   TRIM_API_URL = 'http://api.tr.im/api'
   auth_handler = urllib2.HTTPBasicAuthHandler()
   auth_handler.add_password(realm='tr.im',
                             uri=TRIM_API_URL,
                             user=USERNAME,
                             passwd=PASSWORD)
   opener = urllib2.build_opener(auth_handler)
   urllib2.install_opener(opener)
   response = urllib2.urlopen('%s/trim_simple?url=%s'
                              % (TRIM_API_URL, url_to_trim))
   url = response.read().strip()

response.code is 200 (I think it should be 202). url is valid, but the basic HTTP authentication doesn't seem to have worked, because the shortened URL isn't in my list of URLs (at http://tr.im/?page=1).

After reading http://www.voidspace.org.uk/python/articles/authentication.shtml#doing-it-properly I also tried:

   TRIM_API_URL = 'api.tr.im/api'
   password_mgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
   password_mgr.add_password(None, TRIM_API_URL, USERNAME, PASSWORD)
   auth_handler = urllib2.HTTPBasicAuthHandler(password_mgr)
   opener = urllib2.build_opener(auth_handler)
   urllib2.install_opener(opener)
   response = urllib2.urlopen('http://%s/trim_simple?url=%s'
                              % (TRIM_API_URL, url_to_trim))
   url = response.read().strip()

But I get the same results. (response.code is 200 and url is valid, but not recorded in my account at http://tr.im/.)

If I use query string parameters instead of basic HTTP authentication, like this:

   TRIM_API_URL = 'http://api.tr.im/api'
   response = urllib2.urlopen('%s/trim_simple?url=%s&username=%s&password=%s'
                              % (TRIM_API_URL,
                                 url_to_trim,
                                 USERNAME,
                                 PASSWORD))
   url = response.read().strip()

...then not only is url valid but it's recorded in my tr.im account. (Though response.code is still 200.)

There must be something wrong with my code though (and not tr.im's API), because

$ curl -u yacitus:xxxx http://api.tr.im/api/trim_url.json?url=http://www.google.co.uk

...returns:

{"trimpath":"hfhb","reference":"nH45bftZDWOX0QpVojeDbOvPDnaRaJ","trimmed":"11\/03\/2009","destination":"http:\/\/www.google.co.uk\/","trim_path":"hfhb","domain":"google.co.uk","url":"http:\/\/tr.im\/hfhb","visits":0,"status":{"result":"OK","code":"200","message":"tr.im URL Added."},"date_time":"2009-03-11T10:15:35-04:00"}

...and the URL does appear in my list of URLs on http://tr.im/?page=1.

And if I run:

$ curl -u yacitus:xxxx http://api.tr.im/api/trim_url.json?url=http://www.google.co.uk

...again, I get:

{"trimpath":"hfhb","reference":"nH45bftZDWOX0QpVojeDbOvPDnaRaJ","trimmed":"11\/03\/2009","destination":"http:\/\/www.google.co.uk\/","trim_path":"hfhb","domain":"google.co.uk","url":"http:\/\/tr.im\/hfhb","visits":0,"status":{"result":"OK","code":"201","message":"tr.im URL Already Created [yacitus]."},"date_time":"2009-03-11T10:15:35-04:00"}

Note code is 201, and message is "tr.im URL Already Created [yacitus]."

I must not be doing the basic HTTP authentication correctly (in either attempt). Can you spot my problem? Perhaps I should look and see what's being sent over the wire? I've never done that before. Are there Python APIs I can use (perhaps in pdb)? Or is there another tool (preferably for Mac OS X) I can use?

Phobia

the site must return "WWW-Authenticate" and code 401 before urllib2 (or httplib2) will send your credentials. See my answer below. – Traipse

Note: This service seems to be defunct. – Glyceryl

Answer 1

This seems to work really well (taken from another thread)

import urllib2, base64

request = urllib2.Request("http://api.foursquare.com/v1/user")
base64string = base64.encodestring('%s:%s' % (username, password)).replace('\n', '')
request.add_header("Authorization", "Basic %s" % base64string)   
result = urllib2.urlopen(request)

Phenazine

Instead of base64.encodestring and replace, use base64.standard_b64encode – Hokku

request.add_header('Authorization', b'Basic ' + base64.b64encode(username + b':' + password)) – Veinlet

Based on this answer I have created a package urllib2_prior_auth which has no dependencies outside of stdlib, and I try to push the relevant change to stdlib. – Ossy

Or even shorter / avoiding a import : request.add_header('Authorization', b'Basic ' + (username + b':' + password).encode('base64')) – Tarim

Answer 2

Really cheap solution:

urllib.urlopen('http://user:[email protected]/api')

(which you may decide is not suitable for a number of reasons, like security of the url)

Github API example:

>>> import urllib, json
>>> result = urllib.urlopen('https://personal-access-token:[email protected]/repos/:owner/:repo')
>>> r = json.load(result.fp)
>>> result.close()

Goodish

Are there any advantages to this over using query string parameters? – Phobia

Daryl: if it works, I would say that it's an advantage yes, and probably more secure than query string arguments as most http clients are a bit more careful about how they handle them. – Goodish

I'll probably go with this (so you get my upvote), but I'd still like to figure out what's wrong with my code (so this won't be my accepted answer). – Phobia

This returns an error... InvalidURL: nonnumeric port: '[email protected]/api' – Casillas

@nbolton make sure you are not using urllib2.urlopen(url) – Hett

Answer 3

Take a look at this SO post answer and also look at this basic authentication tutorial from the urllib2 missing manual.

In order for urllib2 basic authentication to work, the http response must contain HTTP code 401 Unauthorized and a key "WWW-Authenticate" with the value "Basic" otherwise, Python won't send your login info, and you will need to either use Requests, or urllib.urlopen(url) with your login in the url, or add a the header like in @Flowpoke's answer.

You can view your error by putting your urlopen in a try block:

try:
    urllib2.urlopen(urllib2.Request(url))
except urllib2.HTTPError, e:
    print e.headers
    print e.headers.has_key('WWW-Authenticate')

Traipse

This helped me because printing the headers lead me to realise I had typo'd the authentication realm. +1 – Rounce

Answer 4

The recommended way is to use requests module:

#!/usr/bin/env python
import requests # $ python -m pip install requests
####from pip._vendor import requests # bundled with python

url = 'https://httpbin.org/hidden-basic-auth/user/passwd'
user, password = 'user', 'passwd'

r = requests.get(url, auth=(user, password)) # send auth unconditionally
r.raise_for_status() # raise an exception if the authentication fails

Here's a single source Python 2/3 compatible urllib2-based variant:

#!/usr/bin/env python
import base64
try:
    from urllib.request import Request, urlopen
except ImportError: # Python 2
    from urllib2 import Request, urlopen

credentials = '{user}:{password}'.format(**vars()).encode()
urlopen(Request(url, headers={'Authorization': # send auth unconditionally
    b'Basic ' + base64.b64encode(credentials)})).close()

Python 3.5+ introduces HTTPPasswordMgrWithPriorAuth() that allows:

..to eliminate unnecessary 401 response handling, or to unconditionally send credentials on the first request in order to communicate with servers that return a 404 response instead of a 401 if the Authorization header is not sent..

#!/usr/bin/env python3
import urllib.request as urllib2

password_manager = urllib2.HTTPPasswordMgrWithPriorAuth()
password_manager.add_password(None, url, user, password,
                              is_authenticated=True) # to handle 404 variant
auth_manager = urllib2.HTTPBasicAuthHandler(password_manager)
opener = urllib2.build_opener(auth_manager)

opener.open(url).close()

It is easy to replace HTTPBasicAuthHandler() with ProxyBasicAuthHandler() if necessary in this case.

Veinlet

HTTPPasswordMgrWithPriorAuth and is_authenticated=True is the key!!! – Subtropics

Answer 5

I would suggest that the current solution is to use my package urllib2_prior_auth which solves this pretty nicely (I work on inclusion to the standard lib.

Ossy

It has been included into Python 3.5 as urrlib.request.HTTPBasicPriorAuthHandler – Ossy

Answer 6

Same solutions as Python urllib2 Basic Auth Problem apply.

see https://mcmap.net/q/169456/-python-urllib2-basic-auth-problem; you can subclass urllib2.HTTPBasicAuthHandler to add the Authorization header to each request that matches the known url.

class PreemptiveBasicAuthHandler(urllib2.HTTPBasicAuthHandler):
    '''Preemptive basic auth.

    Instead of waiting for a 403 to then retry with the credentials,
    send the credentials if the url is handled by the password manager.
    Note: please use realm=None when calling add_password.'''
    def http_request(self, req):
        url = req.get_full_url()
        realm = None
        # this is very similar to the code from retry_http_basic_auth()
        # but returns a request object.
        user, pw = self.passwd.find_user_password(realm, url)
        if pw:
            raw = "%s:%s" % (user, pw)
            auth = 'Basic %s' % base64.b64encode(raw).strip()
            req.add_unredirected_header(self.auth_header, auth)
        return req

    https_request = http_request

Xeric

Isn't the call to strip redundant after b64encode? – Tinctorial

Answer 7

Try python-request or python-grab

Booboo