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package org.subethamail.smtp;
/**
* The interface that enables challenge-response communication necessary for SMTP AUTH.
* Since the authentication process can be stateful, an instance of this class can be stateful too.
* Do not share a single instance of this interface if you don't explicitly need to do so.
*
* @author Marco Trevisan
* @author Jeff Schnitzer
* @author Scott Hernandez
*/
public interface AuthenticationHandler
{
/**
* Initially called using an input string in the RFC2554 form: "AUTH [initial-response]".
* This method must return text which will be delivered to the client, or null if the exchange
* has been completed successfully. If a response is provided to the client, this continues
* the exchange - there will be another auth() call with the client's response.
*
* Depending on the authentication mechanism, the handshaking process may require
* many request-response passes. This method will return null only when the authentication process is finished.
*
* AuthenticationHandlers are associated with a single authentication exchange. If the exchange is stopped
* (ie fails) and is restarted, a new AuthenticationHandler is created. Upon successful authentication, your
* implementation of this object becomes part of the MessageContext. Your MessageHandler may upcast your
* AuthenticationHandler to obtain further information, such as identity.
*
* AuthenticationHandlers do not need to handle the "*" cancel response; this is handled by the framework.
*
* @return null if the authentication process is finished, otherwise a string to hand back to the client.
* @param clientInput The client's input, eg "AUTH PLAIN dGVzdAB0ZXN0ADEyMzQ="
* @throws org.subethamail.smtp.RejectException if authentication fails.
*/
public String auth(String clientInput) throws RejectException;
/**
* If the authentication process was successful, this returns the identity
* of the user. The type defining the identity can vary depending on the
* authentication mechanism used, but typically this returns a String username.
* If authentication was not successful, the return value is undefined.
*/
public Object getIdentity();
}