Demystifying REST

Demystifying RESTKirsten Jones, Technical Leader, Cisco Systems

What Will I Cover?

HTTP Overview REST Web Services OAuth Authentication

HTTP – Protocol for the Web

HyperText Transfer Protocol Used for conversations between web

clients and servers Most of the internet uses HTTP Supports verbs for GET, PUT, POST,

DELETE Query parameter framework

How does HTTP Work?

Client sends a request Method URL Headers (sometimes) parameters (sometimes) body

Server replies with a response Content Status Headers

What do you Mean, Status?

HTTP response codes for dummies. 50x: we fucked up. 40x: you fucked up. 30x: ask that dude over there. 20x: cool.

Props to @DanaDanger for that one

An example request

Chrome browser sends a request to Google Method: GET URL: http://www.google.com Headers:▪ Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8▪ Accept-Language: en-US,en;q=0.8▪ Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3▪ Connection: keep-alive▪ User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3)

AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.168 Safari/535.19

▪ Accept-Encoding: gzip,deflate,sdch▪ Cookie: NID=59=EudJ2a15ql8832PCysQA0qchtuvGWMoA7rkp79VpIYAQ8-

j42IO17LFudCYNMXm9l6SHcu3YgrGRCdrRCyM468xPZaOek4Pi-AXQ8eARqU1SGYx6y7_9LW-c3HHb-vs2; PREF=ID=994f8de0e8b39a5b:U=237805f1f710dc73:FF=0:TM=1336752507:LM=1336752509:S=W0Hha7x4czdXp51U

▪ Host: www.google.com

Example Response

Google sends a response Headers:▪ Content-Length: 24716▪ Content-Encoding: gzip▪ Set-Cookie: NID=59=F48kbwfwOi-qCHJyrnMSUlDBVxK-

ZVKZpq5B5jttt_25IRN4lS-0rQcVttq-dnOIlQzafw1i4HPQAO0RpZ7NuC0WCKWta7SYoekx0--YGf2zIFZ9VXIKS-_UEaOH9iBe; expires=Sat, 10-Nov-2012 21:26:46 GMT; path=/; domain=.google.com; HttpOnly

▪ Expires: -1▪ Server: gws▪ X-XSS-Protection: 1; mode=block▪ Cache-Control: private, max-age=0▪ X-Frame-Options: SAMEORIGIN▪ Content-Type: text/html; charset=UTF-8▪ Date: Fri, 11 May 2012 21:26:46 GMT

Content: A bunch of HTML Status: 200

HTTP Sniffers - Macintosh Macintosh: HTTPScoop

http://tuffcode.com/

Macintosh: Charles (supports SSL) http://www.charlesproxy.com/

Windows: Fiddlerhttp://www.fiddler2.com/fiddler2/

Unix (or Mac): Wireshark (X11)http://www.wireshark.org/

Example: HTTPScoop

Request

Example: HTTPScoop

Headers

Example: HTTPScoop

Request/Response

REST APIs Leverage HTTP

Uses URL paths to define resources Create, Read, Update, Delete

POST, GET, PUT, DELETE Error Codes

HTTP Status Codes Request parameters

Query parameters Response types and configuration

Headers

Example REST Request

Blog Info from Tumblr GET (read) http

://api.tumblr.com/v2/blog/synedra.tumbler.com/info

Requires api_key sent as parameter

Example Request: Httpscoop

Example Request: Httpscoop

Headers

Example Request: Httpscoop

Request/Response

Example REST Response

Status: 200Content:{"meta": {"status":200, "msg":"OK” }, "response":{ "blog":{"title":"Untitled","posts":0, "name":"synedra", "url":"http:\/\/synedra.tumblr.com\/", "updated":0, "description":"","ask":false,"likes":0}}}

Why do we Need Authentication?

Monitor application use Know which users are making

requests Prevent DDOS attacks on the system

OAuth Authentication

Used by many APIs Each application gets a consumer key and

secret Authentication server handles authentication Each user of an application gets a unique

user token and secret Supports tracking of application/member use

of the API Allows users to protect username/password Industry standard – libraries for most

programming languages

How does OAuth Work?

REST web services call adds verification signature to each request

Query parameters Authorization header

Secrets are used to create signature Authentication server checks signature

to verify that it was created using shared secrets

If authentication succeeds, request is processed by API server

OAuth Example - Parameters Signature is generated based on

URL Parameters Consumer key User token

http://api.linkedin.com/v1/people/url=http%3A%2F%2Fwww.linkedin.com%2Fin%2Fsynedra?oauth_body_hash=2jmj7l5rSw0yVb%2FvlWAYkK%2FYBwk%3D&oauth_nonce=6283929&oauth_timestamp=1336775605&oauth_consumer_key=***KEY***&oauth_signature_method=HMAC-SHA1&oauth_version=1.0&oauth_token=***TOKEN***&oauth_signature=CqHiZI6tI3pQGe5a0vVgoT0822A%3D

OAuth Example - Parameters

Request

OAuth Example - Parameters

Headers (nothing special)

OAuth Example - Parameters

Request/Response

OAuth Example - Header

Signature is generated based on URL Parameters Consumer key User token

URL is unchanged: http://api.linkedin.com/v1/people/~/shares

Authorization header has oauth stuff:OAuth realm="http://api.linkedin.com", oauth_body_hash="JtgCKBurLIPLM4dXkn2E3lgrfI4%3D", oauth_nonce="60723468", oauth_timestamp="1336776657", oauth_consumer_key=”***KEY***", oauth_signature_method="HMAC-SHA1", oauth_version="1.0", oauth_token=”***TOKEN***", oauth_signature="8iWVpIK3LhRbu8JPf2gzC1YxQy4%3D"

OAuth Example - Header

No authorization parameters

OAuth Example - Header

Authorization is in the header

OAuth Example - Header

Request/response works the same

Using OAuth with PHP

How to use PECL OAuth to sign API requests

http://pecl.php.net/package/oauth Quick walkthrough to understand

process(but this talk is not about Oauth)

Get a request token

First step in OAuth: Get a request token for this authorization session

OAuth library handles signing the request

Get a verifier

Second step: Send the user to the server to authorize your application

After the user authorizes your application, the server returns a verification code for you to use

Get the access token

Third step: Use the verifier and the request token to get an access token

This is a long lived token

Make a call

Make an API call using the OAuth library

The library handles the signature generation

Summary

HTTP: Hypertext Transfer Protocol REST: REpresentational State

Transfer OAuth: Authentication