OAuth
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    OAuth OAuth Presentation Transcript

    • Open Authentication
      Introduction
      Definitions
      Protocol Workflow
      OAuth Tokens
      Security Architecture
      OAuth and Twitter
      Coding Oauth
      Demo
      Troubleshooting
    • OAuth?
      Oaths is an authorization standard for API’s that does away with logins and passwords to grant authorization to a third-party
    • Why OAuth?
      Every day a new websites are launched which tie services from different sites and offer you
    • OAuth Definitions
      Service provider
      The website or web-service where the restricted resources are located
      User
      User have ‘stuff’ they don’t want to make pubic on the service provider but they do want to share it with another site
      Consumer
      The name for the application trying access the users resources
      Protected Resources
      The ‘stuff’ oauth protects and allow access.
      Tokens
      Tokens are used instead of user credentials to access resources
    • OAuth : Protocol Workflow
    • Jane wants to share some of her vacation photos with her friends. Jane uses Faji, a photo sharing site, for sharing journey photos. She signs into her faji.com account, and uploads two photos which she marks private.
      Using OAuth terminology
      Jane is the User
      Faji is the Service Provider.
      The 2 photos Jane uploaded are the Protected Resources.
      OAuth Example
    • Jane wants to share them with her grandmother. But grandma doesn’t have an internet connection so Jane plans to order prints and have them mailed to grandma. Being a responsible person, Jane uses Beppa, an environmentally friendly photo printing service.
      Using OAuth terminology,
      Beppa is the Consumer.
      Beppa must use OAuth to gain access to the photos in order to print them.
    • When Beppa added support for Faji photo import, a Beppa developer known in OAuth as a Consumer Developer obtained a Consumer Key and Consumer Secret from Faji to be used with Faji’s OAuth-enabled API.
      Using OAuth terminology,
      Consumer Key
      Consumer secret
    • Beppa requests from Faji a Request Token. At this point, the Request Token is not User-specific, and can be used by Beppa to gain User approval from Jane to access her private photos.
      Using OAuth terminology,
      Request Token
    • When Beppa receives the Request Token, it redirects Jane to the Faji OAuth User Authorization URL with the Request Token and asks Faji to redirect Jane back once approval has been granted to http://beppa.com/order.
      Using OAuth terminology,
      Oauth User Authorization URL
      Call Back URL
    • After successfully logging into Faji, Jane is asked to grant access to Beppa, the Consumer. Faji informs Jane of who is requesting access (in this case Beppa) and the type of access being granted. Jane can approve or deny access.
    • Jane waits for Beppa to present her with her photos fetched from her Faji account.
    • While Jane waits, Beppa uses the authorized Request Token and exchanges it for an Access Token. Request Tokens are only good for obtaining User approval, while Access Tokens are used to access Protected Resources, in this case Jane’s photos.
      In the first request, Beppa exchanges the Request Token for an Access Token and in the second (can be multiple requests, one for a list of photos, and a few more to get each photo) request gets the photos.
      Using OAuth terminology,
      Access Token
    • Jane is very impressed how Beppa grabbed her photos without asking for her username and password. She likes what she sees and place the print order.
    • Tokens
      OAuth uses three types of credentials
      Client credentials (consumer key and secret)
      Temporary credentials (request token and secret)
      Token credentials (access token and secret)
    • Client Credentials
      Allows server to authenticate server
      Allows server to get information about the client
      Oauth_consumer_key
      Oauth_consumer_secret
    • Token Credentials
      Token credentials are in place of username and password
      The client uses token credentials to access resource owner protected resource
      Token credentials are limited in scope and duration
      Oauth_access_token
      Oauth_access_secret
    • Temporary credentials
      Used to identify the authorization request
      To accommodate different clients like desktop, mobile etc.
      Add extra flexibility and security
      Oauth_token
      Oauth_token_secret
    • OAuth Security Architecture
    • Signature and Hash
      OAuth uses digital signatures instead of sending the full credentials (specifically, passwords) with each request. 
      The sender uses a mathematical algorithm to calculate the signature of the request and includes it with the request.
    • Hash Algorithm
      A common way to sign digital content is using a hash algorithm. 
      Hashing is the process of taking data (of any size) and condensing it to a much smaller value (digest) in a fully reproducible (one-way) manner
      This means that using the same hash algorithm on the same data will always produce the same smaller value
      Hashing usually does not allow going from the smaller value back to the original.
    • Shared Secret
      By itself, hashing does not verify the identity of the sender, only data integrity.
      In order to allow the recipient to verify that the request came from the claimed sender, the hash algorithm is combined with a shared secret
      If both sides agree on some shared secret known only to them, they can add it to the content being hashed.
    • Nonce(‘Number used Once’)
      What is missing is something to prevent requests intercepted by an unauthorized party, usually by sniffing the network, from being reused. This is known as a replay attack.
      Able to make the same sign request over and over again.
      To prevent compromised requests from being used again (replayed), OAuth uses a nonce and timestamp.
      By having a unique identifier for each request, the Service Provider is able to prevent requests from being used more than once
    • TimeStamp
      Using nonces can be very costly for Service Providers as they demand persistent storage of all nonce values received, ever.
      OAuth adds a timestamp value to each request which allows the Service Provider to only keep nonce values for a limited time.
      When a request comes in with a timestamp that is older than the retained time frame, it is rejected as the Service Provider no longer has nonces from that time period.
    • Signature Methods
      OAuth defines 3 signature methods used to sign and verify requests
      PLAINTEXT
      HMAC-SHA1
      RSA-SHA1
      When signing requests, it is necessary to specify which signature method has been used to allow the recipient to reproduce the signature for verification
      The decision of which signature method to use depends on the security requirements of each application
    • Signature Base String
      Not only must they both use the same algorithm and share secret, but they must sign the same content. 
      This requires a consistent method for converting HTTP requests into a single string which is used as the signed content — the Signature Base String.. 
    • Getting the Request Token
      Building a reqestToken request requires the following:
      HTTP Method,
      Request URI,
      oauth_callback,
      oauth_consumer_key,
      oauth_nonce,
      oauth_signature_method,
      oauth_timestamp
      oauth_version
    • Getting the Request Token
      • First build your string to sign
    • Getting the Request Token
      First build your string to sign
      These parameters get sorted alphabetically, each value is URL escaped, and than concatenated into a single string.
    • Create your Authorization HTTP Header & and Issue the request
      Now we sign this string using our consumer secret and create an HTTP Authorization header. The signature should be placed in the oauth_signature value
      Getting the Request token
    • Now we issue this request to the requestToken endpoint, and if all is sucessful,you will get something like the following URL encoded response:
      The oauth_token field is now your request token, and the oauth_token_secret will be used for signing your request for an access toen.oaut_callback_confirmed just gives you confirmation the we recognized your oauth_callback parameter
      You will want to “hold on” to oauth_token and oauth_token_secret until you have completed the access token step
      Evaluate the Request Token
    • Now that we have a request token, we can build the url to authorize the user. we will then redirect the user to this url so they can grant your application access.
      An authorization url is simply this end point:
      https://api.twitter.com/oauth/authorize with a query parameter tacked on called oauth_token.the value for this parameter is equal to the request token you received in the previous step.
      The user needs to land on this page within 5 minutes of your request take cycle. you should not pass an oauth_callback parameter to this page(you already did that in the request token step)
      Authorizing the member
      Build your Authorization URL
      https://api.twitter.com/oauth/authorize?oauth_token=O6npS44e8ZPQfVcYfHVTGXtnLVBQ4xn8Wu2eBFtPNQ
    • Send the user to Twitter Authorization Page
      The user will then be sent to our authorization page. when completed the user will either be sent back to your oauth_callback URL or presented with a series of digits they will be instructed to hand-enter into your application(if you are performing out-of-band authentication)
      Authorizing the member
    • Prepare your singing secret
      Regardless of whether you used out-of-band authentication or not, you will now be equipped with a request token an oauth_token_secret and an oauth_verfier.you are now going to exchange that request token for an access token, imbued with permission of the Twitter member to act on their behalf
      Getting an Access token
    • Getting the Access Token
      • First build your string to sign
    • First build your string to sign
      These parameters get sorted alphabetically, each value is URL escaped, and than concatenated into a single string.
      Getting the Access Token
    • Create your Authorization HTTP Header & and Issue the request
      Now we sign this string using our request token secret and create an HTTP Authorization header. The signature should be placed in the oauth_signature value
      Getting the Access token
    • Now we issue this request to the aceessToken endpoint, and if all is sucessful,you will get something like the following URL encoded response:
      The oauth_token field is now your access token, and the auth_toke_secert will be used for signing all request on behalf of the member.
      You will want to “hold on” to oauth_token and oauth_token_secret until you have completed the access token step
      Evaluate the Access Token
    • Get Followers/ids
    • XML Response
    • Oauth is complicated, and there are a number of things that go wrong.
      Here are some tips.
      Every error response we send you will contain an xml body describing the error, including a timestamp representing server time. Some oauth-based requests will also return an OAUTH_PROBLEM http header
      Make sure that your server’s system clock is in sync with ours
      Oauth_callback should only be provided on the request token step.
      Oauth_verifier is required in the access Token.
      PUT & POST operations typically have xml content-types. your oauth library should exclude the request body in signature calculations as a result.
      For the access token step, remember that the request tokens oauth_token_secret must be used as part of your signing key
      Likewise, for all resource requests, your access tokens oauth_token_secret must be used as part of your signing key.
      Troubleshooting
    • References
      http://oauth.net/
      http://hueniverse.com/oauth/
      http://developer.yahoo.com/oauth/
      http://dev.twitter.com/pages/oauth_faq