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Versions: 00 01

Network Working Group                               E. Hammer-Lahav, Ed.
Internet-Draft                                                    Yahoo!
Intended status: Standards Track                            July 6, 2009
Expires: January 7, 2010


                   The OAuth Protocol: Web Delegation
                   draft-ietf-oauth-web-delegation-01

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January 7, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document specifies the OAuth protocol web delegation method.
   OAuth allows clients to access server resources on behalf of another
   party (such a different client or an end user).  This document



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   defines a redirection-based user-agent process for end users to
   authorize access to clients by substituting their credentials
   (typically, a username and password pair) with a different set of
   delegation-specific credentials.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  4
   3.  Redirection-Based Authorization  . . . . . . . . . . . . . . .  4
   4.  Temporary Credentials  . . . . . . . . . . . . . . . . . . . .  5
   5.  Resource Owner Authorization . . . . . . . . . . . . . . . . .  6
   6.  Token Credentials  . . . . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
     8.1.  Credentials Transmission . . . . . . . . . . . . . . . . .  9
     8.2.  Phishing Attacks . . . . . . . . . . . . . . . . . . . . .  9
     8.3.  Scoping of Access Requests . . . . . . . . . . . . . . . . 10
     8.4.  Entropy of Secrets . . . . . . . . . . . . . . . . . . . . 10
     8.5.  Denial of Service / Resource Exhaustion Attacks  . . . . . 10
     8.6.  Cross-Site Request Forgery (CSRF)  . . . . . . . . . . . . 11
     8.7.  User Interface Redress . . . . . . . . . . . . . . . . . . 11
     8.8.  Automatic Processing of Repeat Authorizations  . . . . . . 12
   Appendix A.     Examples . . . . . . . . . . . . . . . . . . . . . 12
   Appendix A.1.   Obtaining Temporary Credentials  . . . . . . . . . 13
   Appendix A.2.   Requesting Resource Owner Authorization  . . . . . 14
   Appendix A.3.   Obtaining Token Credentials  . . . . . . . . . . . 14
   Appendix A.4.   Accessing protected resources  . . . . . . . . . . 14
   Appendix A.4.1. Generating Signature Base String . . . . . . . . . 14
   Appendix A.4.2. Calculating Signature Value  . . . . . . . . . . . 16
   Appendix A.4.3. Requesting protected resource  . . . . . . . . . . 16
   Appendix B.     Acknowledgments  . . . . . . . . . . . . . . . . . 16
   Appendix C.     Document History . . . . . . . . . . . . . . . . . 16
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 18
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18












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1.  Introduction

   The OAuth protocol provides a method for servers to allow third-party
   access to protected resources, without forcing their end users to
   share their credentials.  This pattern is common among services that
   allow third-party developers to extend the service functionality, by
   building applications using an open API.

   For example, a web user (resource owner) can grant a printing service
   (client) access to its private photos stored at a photo sharing
   service (server), without sharing its credentials with the printing
   service.  Instead, the user authenticates directly with the photo
   sharing service and issue the printing service delegation-specific
   credentials.

   OAuth introduces a third role to the traditional client-server
   authentication model: the resource owner.  In the OAuth model, the
   client requests access to resources hosted by the server but not
   controlled by the client, but by the resource owner.  In addition,
   OAuth allows the server to verify not only the resource owner's
   credentials, but also those of the client making the request.

   In order for the client to access resources, it first has to obtain
   permission from the resource owner.  This permission is expressed in
   the form of a token and matching shared-secret.  The purpose of the
   token is to substitute the need for the resource owner to share its
   server credentials (usually a username and password pair) with the
   client.  Unlike server credentials, tokens can be issued with a
   restricted scope and limited lifetime.

   This specification consists of two parts.
   [draft-ietf-oauth-authentication] defines a method for making
   authenticated HTTP requests using two sets of credentials, one
   identifying the client making the request, and a second identifying
   the resource owner on whose behalf the request is being made.

   This document defines a redirection-based user agent process for end
   users to authorize client access to their resources, by
   authenticating directly with the server and provisioning tokens to
   the client for use with the authentication method.

1.1.  Terminology

   client
         An HTTP client (per [RFC2616]) capable of making OAuth-
         authenticated requests per [draft-ietf-oauth-authentication].





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   server
         An HTTP server (per [RFC2616]) capable of accepting OAuth-
         authenticated requests per [draft-ietf-oauth-authentication].

   protected resource
         An access-restricted resource (per [RFC2616]) which can be
         obtained from the server using an OAuth-authenticated request
         per [draft-ietf-oauth-authentication].

   resource owner
         An entity capable of accessing and controlling protected
         resources by using credentials to authenticate with the server.

   token
         An unique identifier issued by the server and used by the
         client to associate authenticated requests with the resource
         owner whose authorization is requested or has been obtained by
         the client.  Tokens have a matching shared-secret that is used
         by the client to establish its ownership of the token, and its
         authority to represent the resource owner.


2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


3.  Redirection-Based Authorization

   OAuth uses a set of token credentials to represent the authorization
   granted to the client by the resource owner.  Typically, token
   credentials are issued by the server at the resource owner's request,
   after authenticating the resource owner's identity using its server
   credentials (usually a username and password pair).

   There are many ways in which a resource owner can facilitate the
   provisioning of token credentials.  This section defines one such
   way, using HTTP redirections and the resource owner's user agent.
   This redirection-based authorization method includes three steps:

   1.  The client obtains a set of temporary credentials from the
       server.

   2.  The resource owner authorizes the server to issue token
       credentials to the client using the temporary credentials.




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   3.  The client uses the temporary credentials to request a set of
       token credentials from the server, which will enable it to access
       the resource owner's protected resources.  The temporary
       credentials discarded.

   The temporary credentials MUST be revoked after being used once to
   obtain the token credentials.  It is RECOMMENDED that the temporary
   credentials have a limited lifetime.  Servers SHOULD enable resource
   owners to revoke token credentials after they have been issued to
   clients.

   In order for the client to perform these steps, the server needs to
   advertise the URIs of these three endpoints, as well as the HTTP
   method (GET, POST, etc.) used to make each requests.  To assist in
   communicating these endpoint, each is given a name:

   Temporary Credential Request
         The endpoint used by the client to obtain temporary credentials
         as described in Section 4.

   Resource Owner Authorization
         The endpoint to which the resource owner is redirected to grant
         authorization as described in Section 5.

   Token Request
         The endpoint used by the client to request a set of token
         credentials using the temporary credentials as described in
         Section 6.

   The three URIs MAY include a query component as defined by [RFC3986]
   section 3, but if present, the query MUST NOT contain any parameters
   beginning with the "oauth_" prefix.

   The method in which the server advertises its three endpoint is
   beyond the scope of this specification.


4.  Temporary Credentials

   The client obtains a set of temporary credentials from the server by
   making an authenticated request per
   [draft-ietf-oauth-authentication].  The client MUST use the HTTP
   method advertised by the server.  The HTTP POST method is
   RECOMMENDED.  The client constructs a request URI by adding the
   following parameter to the Temporary Credential Request endpoint URI:






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   oauth_callback:  An absolute URL to which the server will redirect
         the resource owner back when the Resource Owner Authorization
         step (Section 5) is completed.  If the client is unable to
         receive callbacks or a callback URI has been established via
         other means, the parameter value MUST be set to "oob" (case
         sensitive), to indicate an out-of-band configuration.

   Servers MAY specify additional parameters.

   When making the request, the client authenticates using only the
   client credentials.  The client MUST omit the "oauth_token" protocol
   parameter from the request and use an empty string as the token
   secret value.

   The server MUST verify that the request is valid per
   [draft-ietf-oauth-authentication] and respond back to the client with
   a set of temporary credentials.  The temporary credentials are
   included in the HTTP response body using the
   "application/x-www-form-urlencoded" content type as defined by
   [W3C.REC-html40-19980424].

   The response contains the following parameters:

   oauth_token
         The temporary credentials identifier.

   oauth_token_secret
         The temporary credentials shared-secret.

   oauth_callback_confirmed:  MUST be present and set to "true".  The
         client MAY use this to confirm that the server received the
         callback value.

   Note that even though the parameter names include the term 'token',
   these credentials are not token credentials, but are used in the next
   two steps in a similar manner to token credentials.

   For example (line breaks are for display purposes only):

     oauth_token=ab3cd9j4ks73hf7g&oauth_token_secret=xyz4992k83j47x0b&
     oauth_callback_confirmed=true


5.  Resource Owner Authorization

   Before the client requests a set of token credentials from the
   server, it MUST send the user to the server to authorize the request.
   The client constructs a request URI by adding the following



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   parameters to the Resource Owner Authorization endpoint URI:

   oauth_token
         REQUIRED.  The temporary credentials identifier obtained in
         Section 4 in the "oauth_token" parameter.  Servers MAY declare
         this parameter as OPTIONAL, in which case they MUST provide a
         way for the resource owner to indicate the identifier through
         other means.

   Servers MAY specify additional parameters.

   The client redirects the resource owner to the constructed URI using
   an HTTP redirection response, or by other means available to it via
   the resource owner's user agent.  The request MUST use the HTTP GET
   method.

   The way in which the server handles the authorization request is
   beyond the scope of this specification.  However, the server MUST
   first verify the identity of the resource owner.

   When asking the resource owner to authorize the requested access, the
   server SHOULD present to the resource owner information about the
   client requesting access based on the association of the temporary
   credentials with the client identity.  When displaying any such
   information, the server SHOULD indicate if the information has been
   verified.

   After receiving an authorization decision from the resource owner,
   the server redirects the resource owner to the callback URI if one
   was provided in the "oauth_callback" parameter or by other means.

   To make sure that the resource owner granting access is the same
   resource owner returning back to the client to complete the process,
   the server MUST generate a verification code: an unguessable value
   passed to the client via the resource owner and REQUIRED to complete
   the process.  The server constructs the request URI by adding the
   following parameter to the callback URI query component:

   oauth_token
         The temporary credentials identifier the resource owner
         authorized or denied access to.

   oauth_verifier:  The verification code.

   If the callback URI already includes a query component, the server
   MUST append the OAuth parameters to the end of the existing query.





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   For example (line breaks are for display purposes only):

     http://client.example.net/cb?state=1&oauth_token=ab3cd9j4ks73hf7g&
     oauth_verifier=473829k9302sa

   If the client did not provide a callback URI, the server SHOULD
   display the value of the verification code, and instruct the resource
   owner to manually inform the client that authorization is completed.
   If the server knows a client to be running on a limited device it
   SHOULD ensure that the verifier value is suitable for manual entry.


6.  Token Credentials

   The client obtains a set of token credentials from the server by
   making an authenticated request per
   [draft-ietf-oauth-authentication].  The client MUST use the HTTP
   method advertised by the server.  The HTTP POST method is
   RECOMMENDED.  The client constructs a request URI by adding the
   following parameter to the Token Request endpoint URI:

   oauth_verifier:  The verification code received from the server in
         the previous step.

   When making the request, the client authenticates using the client
   credentials as well as the temporary credentials.  The temporary
   credentials are used as a substitution for token credentials in the
   authenticated request.

   The server MUST verify the validity of the request per
   [draft-ietf-oauth-authentication], ensure that the resource owner has
   authorized the provisioning of token credentials to the client, and
   that the temporary credentials have not expired or used before.  The
   server MUST also verify the verification code received from the
   client.  If the request is valid and authorized, the token
   credentials are included in the HTTP response body using the
   "application/x-www-form-urlencoded" content type as defined by
   [W3C.REC-html40-19980424].

   The response contains the following parameters:

   oauth_token
         The token identifier.

   oauth_token_secret
         The token shared-secret.





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   For example:

     oauth_token=j49ddk933skd9dks&oauth_token_secret=ll399dj47dskfjdk

   The token credentials issued by the server MUST reflect the exact
   scope, duration, and other attributes approved by the resource owner.

   Once the client receives the token credentials, it can proceed to
   access protected resources on behalf of the resource owner by making
   an authenticated request per [draft-ietf-oauth-authentication] using
   the client credentials and the token credentials received.


7.  IANA Considerations

   This memo includes no request to IANA.


8.  Security Considerations

   As stated in [RFC2617], the greatest sources of risks are usually
   found not in the core protocol itself but in policies and procedures
   surrounding its use.  Implementers are strongly encouraged to assess
   how this protocol addresses their security requirements.

8.1.  Credentials Transmission

   The OAuth specification does not describe any mechanism for
   protecting tokens and shared-secrets from eavesdroppers when they are
   transmitted from the server to the client during the authorization
   phase.  Servers should ensure that these transmissions are protected
   using transport-layer mechanisms such as TLS or SSL.

8.2.  Phishing Attacks

   Wide deployment of OAuth and similar protocols may cause resource
   owners to become inured to the practice of being redirected to
   websites where they are asked to enter their passwords.  If resource
   owners are not careful to verify the authenticity of these websites
   before entering their credentials, it will be possible for attackers
   to exploit this practice to steal resource owners' passwords.

   Servers should attempt to educate resource owners about the risks
   phishing attacks pose, and should provide mechanisms that make it
   easy for resource owners to confirm the authenticity of their sites.






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8.3.  Scoping of Access Requests

   By itself, OAuth does not provide any method for scoping the access
   rights granted to a client.  However, most applications do require
   greater granularity of access rights.  For example, servers may wish
   to make it possible to grant access to some protected resources but
   not others, or to grant only limited access (such as read-only
   access) to those protected resources.

   When implementing OAuth, servers should consider the types of access
   resource owners may wish to grant clients, and should provide
   mechanisms to do so.  Servers should also take care to ensure that
   resource owners understand the access they are granting, as well as
   any risks that may be involved.

8.4.  Entropy of Secrets

   Unless a transport-layer security protocol is used, eavesdroppers
   will have full access to OAuth requests and signatures, and will thus
   be able to mount offline brute-force attacks to recover the
   credentials used.  Servers should be careful to assign shared-secrets
   which are long enough, and random enough, to resist such attacks for
   at least the length of time that the shared-secrets are valid.

   For example, if shared-secrets are valid for two weeks, servers
   should ensure that it is not possible to mount a brute force attack
   that recovers the shared-secret in less than two weeks.  Of course,
   servers are urged to err on the side of caution, and use the longest
   secrets reasonable.

   It is equally important that the pseudo-random number generator
   (PRNG) used to generate these secrets be of sufficiently high
   quality.  Many PRNG implementations generate number sequences that
   may appear to be random, but which nevertheless exhibit patterns or
   other weaknesses which make cryptanalysis or brute force attacks
   easier.  Implementers should be careful to use cryptographically
   secure PRNGs to avoid these problems.

8.5.  Denial of Service / Resource Exhaustion Attacks

   The OAuth protocol has a number of features which may make resource
   exhaustion attacks against servers possible.  For example, if a
   server includes a nontrivial amount of entropy in token shared-
   secrets as recommended above, then an attacker may be able to exhaust
   the server's entropy pool very quickly by repeatedly obtaining
   temporary credentials from the server.

   Similarly, OAuth requires servers to track used nonces.  If an



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   attacker is able to use many nonces quickly, the resources required
   to track them may exhaust available capacity.  And again, OAuth can
   require servers to perform potentially expensive computations in
   order to verify the signature on incoming requests.  An attacker may
   exploit this to perform a denial of service attack by sending a large
   number of invalid requests to the server.

   Resource Exhaustion attacks are by no means specific to OAuth.
   However, OAuth implementers should be careful to consider the
   additional avenues of attack that OAuth exposes, and design their
   implementations accordingly.  For example, entropy starvation
   typically results in either a complete denial of service while the
   system waits for new entropy or else in weak (easily guessable)
   secrets.  When implementing OAuth, servers should consider which of
   these presents a more serious risk for their application and design
   accordingly.

8.6.  Cross-Site Request Forgery (CSRF)

   Cross-Site Request Forgery (CSRF) is a web-based attack whereby HTTP
   requests are transmitted from a user that the website trusts or has
   authenticated.  CSRF attacks on OAuth approvals can allow an attacker
   to obtain authorization to protected resources without the consent of
   the User.  Servers SHOULD strongly consider best practices in CSRF
   prevention at all OAuth endpoints.

   CSRF attacks on OAuth callback URIs hosted by client are also
   possible.  Clients should prevent CSRF attacks on OAuth callback URIs
   by verifying that the resource owner at the client site intended to
   complete the OAuth negotiation with the server.

8.7.  User Interface Redress

   Servers should protect the authorization process against UI Redress
   attacks (also known as "clickjacking").  As of the time of this
   writing, no complete defenses against UI redress are available.
   Servers can mitigate the risk of UI redress attacks through the
   following techniques:

   o  Javascript frame busting.

   o  Javascript frame busting, and requiring that browsers have
      javascript enabled on the authorization page.

   o  Browser-specific anti-framing techniques.

   o  Requiring password reentry before issuing OAuth tokens.




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8.8.  Automatic Processing of Repeat Authorizations

   Servers may wish to automatically process authorization requests
   (Section 5) from clients which have been previously authorized by the
   resource owner.  When the resource owner is redirected to the server
   to grant access, the server detects that the resource owner has
   already granted access to that particular client.  Instead of
   prompting the resource owner for approval, the server automatically
   redirects the resource owner back to the client.

   If the client credentials are compromised, automatic processing
   creates additional security risks.  An attacker can use the stolen
   client credentials to redirect the resource owner to the server with
   an authorization request.  The server will then grant access to the
   resource owner's data without the resource owner's explicit approval,
   or even awareness of an attack.  If no automatic approval is
   implemented, an attacker must use social engineering to convince the
   resource owner to approve access.

   Servers can mitigate the risks associated with automatic processing
   by limiting the scope of token credentials obtained through automated
   approvals.  Tokens credentials obtained through explicit resource
   owner consent can remain unaffected. clients can mitigate the risks
   associated with automatic processing by protecting their client
   credentials.


Appendix A.  Examples

   In this example, photos.example.net is a photo sharing website
   (server), and printer.example.com is a photo printing service
   (client).  Jane (resource owner) would like printer.example.com to
   print a private photo stored at photos.example.net.

   When Jane signs-into photos.example.net using her username and
   password, she can access the photo by requesting the URI
   "http://photos.example.net/photo?file=vacation.jpg" (which also
   supports the optional "size" parameter).  Jane does not want to share
   her username and password with printer.example.com, but would like it
   to access the photo and print it.

   The server documentation advertises support for the "HMAC-SHA1" and
   "PLAINTEXT" methods, with "PLAINTEXT" restricted to secure (HTTPS)
   requests.  It also advertises the following endpoint URIs:







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   Temporary Credential Request
         https://photos.example.net/initiate, using HTTP POST

   Resource Owner Authorization URI:
         http://photos.example.net/authorize, using HTTP GET

   Token Request URI:
         https://photos.example.net/token, using HTTP POST

   The printer.example.com has already established client credentials
   with photos.example.net:

   Client Identifier
         "dpf43f3p2l4k3l03"

   Client Shared-Secret:
         "kd94hf93k423kf44"

   When printer.example.com attempts to print the request photo, it
   receives an HTTP response with a 401 (Unauthorized) status code, and
   a challenge to use OAuth:

     WWW-Authenticate: OAuth realm="http://photos.example.net/"

Appendix A.1.  Obtaining Temporary Credentials

   The client sends the following HTTPS POST request to the server:

     POST /initiate HTTP/1.1
     Host: photos.example.net
     Authorization: OAuth realm="http://photos.example.com/",
        oauth_consumer_key="dpf43f3p2l4k3l03",
        oauth_signature_method="PLAINTEXT",
        oauth_signature="kd94hf93k423kf44%26",
        oauth_timestamp="1191242090",
        oauth_nonce="hsu94j3884jdopsl",
        oauth_version="1.0",
        oauth_callback="http%3A%2F%2Fprinter.example.com%2Fready"

   The server validates the request and replies with a set of temporary
   credentials in the body of the HTTP response:

     oauth_token=hh5s93j4hdidpola&oauth_token_secret=hdhd0244k9j7ao03&
     oauth_callback_confirmed=true







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Appendix A.2.  Requesting Resource Owner Authorization

   The client redirects Jane's browser to the server's Resource Owner
   Authorization endpoint URI to obtain Jane's approval for accessing
   her private photos.

     http://photos.example.net/authorize?oauth_token=hh5s93j4hdidpola

   The server asks Jane to sign-in using her username and password and
   if successful, asks her if she approves granting printer.example.com
   access to her private photos.  Jane approves the request and is
   redirects her back to the client's callback URI:

     http://printer.example.com/ready?
     oauth_token=hh5s93j4hdidpola&oauth_verifier=hfdp7dh39dks9884

Appendix A.3.  Obtaining Token Credentials

   After being informed by the callback request that Jane approved
   authorized access, printer.example.com requests a set of token
   credentials using its temporary credentials:

     POST /token HTTP/1.1
     Host: photos.example.net
     Authorization: OAuth realm="http://photos.example.com/",
        oauth_consumer_key="dpf43f3p2l4k3l03",
        oauth_token="hh5s93j4hdidpola",
        oauth_signature_method="PLAINTEXT",
        oauth_signature="kd94hf93k423kf44%26hdhd0244k9j7ao03",
        oauth_timestamp="1191242092",
        oauth_nonce="dji430splmx33448",
        oauth_version="1.0"
        oauth_verifier="hfdp7dh39dks9884"

   The server validates the request and replies with a set of token
   credentials in the body of the HTTP response:

     oauth_token=nnch734d00sl2jdk&oauth_token_secret=pfkkdhi9sl3r4s00

Appendix A.4.  Accessing protected resources

   The printer is now ready to request the private photo.  Since the
   photo URI does not use HTTPS, the "HMAC-SHA1" method is required.

Appendix A.4.1.  Generating Signature Base String

   To generate the signature, it first needs to generate the signature
   base string.  The request contains the following parameters



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   ("oauth_signature" excluded) which need to be ordered and
   concatenated into a normalized string:

   oauth_consumer_key
         "dpf43f3p2l4k3l03"

   oauth_token
         "nnch734d00sl2jdk"

   oauth_signature_method
         "HMAC-SHA1"

   oauth_timestamp
         "1191242096"

   oauth_nonce
         "kllo9940pd9333jh"

   oauth_version
         "1.0"

   file
         "vacation.jpg"

   size
         "original"

   The following inputs are used to generate the signature base string:

   1.  The HTTP request method: "GET"

   2.  The request URI: "http://photos.example.net/photos"

   3.  The encoded normalized request parameters string: "file=vacation.
       jpg&oauth_consumer_key=dpf43f3p2l4k3l03&oauth_nonce=kllo9940pd933
       3jh&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1191242096&o
       auth_token=nnch734d00sl2jdk&oauth_version=1.0&size=original"

   The signature base string is (line breaks are for display purposes
   only):

     GET&http%3A%2F%2Fphotos.example.net%2Fphotos&file%3Dvacation.jpg%26
     oauth_consumer_key%3Ddpf43f3p2l4k3l03%26oauth_nonce%3Dkllo9940pd933
     3jh%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D119124
     2096%26oauth_token%3Dnnch734d00sl2jdk%26oauth_version%3D1.0%26size%
     3Doriginal





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Appendix A.4.2.  Calculating Signature Value

   HMAC-SHA1 produces the following "digest" value as a base64-encoded
   string (using the signature base string as "text" and
   "kd94hf93k423kf44&pfkkdhi9sl3r4s00" as "key"):

     tR3+Ty81lMeYAr/Fid0kMTYa/WM=

Appendix A.4.3.  Requesting protected resource

   All together, the client request for the photo is:

     GET /photos?file=vacation.jpg&size=original HTTP/1.1
     Host: photos.example.com
     Authorization: OAuth realm="http://photos.example.net/",
        oauth_consumer_key="dpf43f3p2l4k3l03",
        oauth_token="nnch734d00sl2jdk",
        oauth_signature_method="HMAC-SHA1",
        oauth_signature="tR3%2BTy81lMeYAr%2FFid0kMTYa%2FWM%3D",
        oauth_timestamp="1191242096",
        oauth_nonce="kllo9940pd9333jh",
        oauth_version="1.0"

   The photos.example.net sever validates the request and responds with
   the requested photo.


Appendix B.  Acknowledgments

   This specification is directly based on the [OAuth Core 1.0 Revision
   A] community specification which was the product of the OAuth
   community.  OAuth was modeled after existing proprietary protocols
   and best practices that have been independently implemented by
   various web sites.  This specification was orignially authored by:
   Mark Atwood, Dirk Balfanz, Darren Bounds, Richard M. Conlan, Blaine
   Cook, Leah Culver, Breno de Medeiros, Brian Eaton, Kellan Elliott-
   McCrea, Larry Halff, Eran Hammer-Lahav, Ben Laurie, Chris Messina,
   John Panzer, Sam Quigley, David Recordon, Eran Sandler, Jonathan
   Sergent, Todd Sieling, Brian Slesinsky, and Andy Smith.


Appendix C.  Document History

   [[ To be removed by the RFC editor before publication as an RFC. ]]

   -01





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   o  Moved all subsection from section 3 to the document root.

   -00

   o  Transitioned from the individual submission draft-hammer-oauth-02
      to working group draft.

   o  Split draft-hammer-oauth-02 into two drafts, one dealing with web
      delegation (this draft) and another dealing with authentication
      draft-ietf-oauth-web-authentication.

   o  Updated draft with changes from OAuth Core 1.0 Revision A to fix a
      session fixation exploit.


9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
              Leach, P., Luotonen, A., and L. Stewart, "HTTP
              Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [W3C.REC-html40-19980424]
              Hors, A., Jacobs, I., and D. Raggett, "HTML 4.0
              Specification", World Wide Web Consortium
              Recommendation REC-html40-19980424, April 1998,
              <http://www.w3.org/TR/1998/REC-html40-19980424>.

   [draft-ietf-oauth-authentication]
              Hammer-Lahav, E., Ed., "The OAuth Protocol:
              Authentication".







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9.2.  Informative References

   [OAuth Core 1.0 Revision A]
              OAuth, OCW., "OAuth Core 1.0".


Author's Address

   Eran Hammer-Lahav (editor)
   Yahoo!

   Email: eran@hueniverse.com
   URI:   http://hueniverse.com






































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