Exploring OAuth-Protected APIs

From time to time I need to debug OAuth-protected APIs, checking response headers and examining XML and JSON payloads. curl generally rocks for this sort of thing, but when the APIs in question are protected with OAuth, things break down. Likewise for benchmarking (ab, httperf, etc.) and exploration–isn’t it nice to browse APIs that return XML in Firefox?

This needn’t to be the case.

Enter oauth-proxy

This is why I wrote oauth-proxy. It does what it says on the tin: it acts a proxy server that transparently adds OAuth headers to requests.

There are 2 steps to using it. First, install it:

$ easy_install oauth-proxy

Then, start it:

$ oauth-proxy \
    --consumer-key <consumer key> \
    --consumer-secret <consumer secret> \
    [--token <token>] \
    [--token-secret <token secret>] \
    [-p <proxy port>] \
    [--ssl]

If you’re accessing a resource that only requires 2-legged OAuth, you can omit --token and --token-secret. The proxy port defaults to 8001, and --ssl is used if you’re proxying connections to a provider that requires SSL (Fire Eagle, for example).

Once it’s been started, use curl to make requests through it:

$ curl -x localhost:8001 http://host.name/path

You can also benchmark your APIs through it using ApacheBench (ab, as it includes support for HTTP proxies). Note that you are introducing additional overhead by proxying the request, so your numbers may be a bit off.

$ ab -X localhost:8001 http://host.name/path

Firefox (and browsers in general) supports HTTP proxies, so you can add a “Manual Proxy Configuration” and pass requests through oauth-proxy to explore APIs in the comfort of your favorite browser. By default, all requests that Firefox makes will go through the proxy and be signed, which may confuse other websites you visit (and will inadvertently reveal your consumer key and access token but not the corresponding secrets).

Access Tokens Sold Separately

If you’re accessing a resource that requires 3-legged OAuth, you’ll need a token. You may already have one, but if you don’t, you can use the OAuth library for Ruby to obtain one.

First, install the gem (0.3.5 is current as of this writing):

$ sudo gem install oauth

Then, trigger the authorization process from the command-line:

$ oauth \
    --consumer-key <consumer key> \
    --consumer-secret <consumer secret> \
    --access-token-url http://host.name/path/to/access_token \
    --authorize-url http://host.name/path/to/authorize \
    --request-token-url http://host.name/path/to/request_token \
    authorize

Follow the prompts, and voilà, an access token and secret that you can use with oauth-proxy.

A Concrete Example

Twitter’s popular, right? Let’s use that.

First, register an application to get a consumer key and secret. I registered as a “client” application, since the command-line still doesn’t have a callback url.

Once that’s done, you’ll get a set of credentials that can be used to initiate the authorization process.

Let’s authorize.

$ oauth \
  --consumer-key <consumer key> \
  --consumer-secret <consumer secret> \
  --access-token-url http://twitter.com/oauth/access_token \
  --authorize-url http://twitter.com/oauth/authorize \
  --request-token-url http://twitter.com/oauth/request_token \
  authorize

After following the prompts, you’ll get something back that looks like this:

oauth_token_secret: [redacted]
oauth_token: [redacted]
user_id: [redacted]
screen_name: [redacted]

You can then use those values to start the OAuth proxy:

$ oauth-proxy \
    --consumer-key <consumer key> \
    --consumer-secret <consumer secret> \
    --token <access token> \
    --token-secret <token secret>

Now we’re set. Let’s go exploring:

$ curl -sx http://localhost:8001 \
    http://twitter.com/statuses/friends_timeline.json | \
    jsonpretty | pygmentize -l js

You’ll get exactly what you’re expecting and you’ll be using OAuth (this is a partially contrived example since Twitter still supports HTTP Base Auth).

(jsonpretty rocks. pygmentize (easy install pygments) makes it easier to make sense of the chaos.)

That’s all. I use this stuff all the time and can’t imagine debugging APIs without it.