Kirsten Jones, Technical Leader, Cisco Systems. Application Developers …Curious about using REST …Wanting help debugging the system Not REST API Architects.

Kirsten Jones, Technical Leader, Cisco Systems

Application Developers…Curious about using REST…Wanting help debugging the

system

Not REST API Architects (sorry!)

HTTP OverviewREST Web ServicesOAuth Authentication BasicsREST Debugging

HyperText Transfer ProtocolUsed for conversations between web

clients and serversMost of the internet uses HTTPSupports verbs for GET, PUT, POST,

DELETEQuery parameter framework

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

Server replies with a response Content Status Headers

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 this

Headers Generally meta-information about the

request For instance: requesting an image in a

specific formatParameters

Limit or describe how you want the resource (searches, filters)

Defines the resource you’re requesting

Request (client) Accept: Give me this kind of response.

Here’s a list in order of what I’m hoping you’ll send.Accept: text/html,application/xhtml+xml,application/xml

Response (server) Content-Type: This is the kind of response

I’m sending you.Content-Type: text/html; charset=UTF-8

Part of the URLEverything after the question mark,

delimited by ampersandshttp://www.example.com/

search_people?this=that&foo=bar

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

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

Some browsers provide tools to view HTTP traffic

Great for understanding what your browser is doing

Tracking programmatic traffic requires a separate tool

Macintosh: HTTPScoophttp://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/

Request

Headers

Request/Response

Uses URL paths to define resourcesCreate, Read, Update, Delete

POST, GET, PUT, DELETEError Codes

HTTP Status CodesRequest parameters

Query parametersResponse types and configuration

Headers

Blog Info from TumblrGET (read)

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

Requires api_key sent as parameterhttp://api.tumblr.com/v2/blog/

synedra.tumblr.com/info?api_key=my_api_key

Headers

Request/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}}}

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

REST web services call adds verification signature to each request

Query parameters Authorization header

Secrets are used to create signatureAuthentication server checks signature

to verify that it was created using shared secrets

If authentication succeeds, request is processed by API server

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

Request

Headers (nothing special)

Request/Response

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"

No authorization parameters

Authorization is in the header

Request/response works the same

Download the oauth2 package from github No, it’s OAuth 1.0a, ignore the name

Quick walkthrough to understand process (but this talk is not about OAuth)

import oauth2 as oauthconsumer_key = 'xxxxxxxxxxxxxx'consumer_secret = 'xxxxxxxxxxxxxx’

consumer = oauth.Consumer(consumer_key, consumer_secret)client = oauth.Client(consumer)

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

OAuth library handles signing the request

import oauth2 as oauthconsumer_key = 'xxxxxxxxxxxxxx'consumer_secret = 'xxxxxxxxxxxxxx’

consumer = oauth.Consumer(consumer_key, consumer_secret)client = oauth.Client(consumer)

resp, content = client.request(request_token_url, "POST")request_token = dict(urlparse.parse_qsl(content))

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

print "Go to the following link in your browser:"print "%s?oauth_token=%s" % (authorize_url, request_token['oauth_token'])accepted = 'n'while accepted.lower() == 'n': accepted = raw_input('Have you authorized me? (y/n) ')oauth_verifier = raw_input('What is the PIN? ’)

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

This is usually a long lived token

token = oauth.Token(request_token['oauth_token'], request_token['oauth_token_secret'])token.set_verifier(oauth_verifier)client = oauth.Client(consumer, token)

resp, content = client.request(access_token_url, "POST")access_token = dict(urlparse.parse_qsl(content))

Make an API call using the OAuth library

The library handles the signature generationurl = http://api.linkedin.com/v1/people/~consumer = oauth.Consumer(

key=”XXXXX",secret=”XXXXX")

token = oauth.Token(key=”XXXXX", secret=”XXXXX")

client = oauth.Client(consumer, token)

resp, content = client.request(url)

Use the documentation and resources provided by the platform team

Consoles, IODocs, OAuth signature checkers

Use existing, tested libraries Code defensively

401 authentication errors (signatures, tokens)

403 authorization errors (throttles, permissions)

400 errors – parameters, headersLibrary out of sync with API

Try building the request using just the OAuth library

Find someone else’s code that worksHTTP Servers aren’t that smart

HTTP: Hypertext Transfer ProtocolREST: REpresentational State

TransferOAuth: Authentication