A Primer to the OAuth Protocol

The shared secret used to verify the request signature is called the Consumer Secret. Because it is vital to the integrity of this transaction, it is imperative that this piece of data be kept secret. In the case of a Web-based Consumer, such as a Web service, it is easy to keep the Consumer Secret safe. If the Consumer is a client-side application, the Consumer Secret must be hard-coded in each copy of the application. This means the Consumer Secret potentially is discoverable, which compromises the integrity of any desktop application.

There is a known session fixation attack vulnerability found in the OAuth 1.0 protocol that allows an attacker to gain access to a target's account. The attacker logs in to the Consumer site and initiates the OAuth authorization process. The attacker saves the authorization request page instead of clicking submit. This stores the request token and secret. The attacker sends a link to a victim, which, if clicked, will continue the authorization process as started by the attacker. Once completed, the attacker will have access to the victim's protected resources via the Consumer used.