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package com.sun.security.sasl;

import javax.security.sasl.*;
import java.security.NoSuchAlgorithmException;

import java.util.logging.Logger;
import java.util.logging.Level;

import static java.nio.charset.StandardCharsets.UTF_8;

Implements the CRAM-MD5 SASL client-side mechanism.
(RFC 2195).
CRAM-MD5 has no initial response. It receives bytes from
the server as a challenge, which it hashes by using MD5 and the password.
It concatenates the authentication ID with this result and returns it
as the response to the challenge. At that point, the exchange is complete.
Author:
Vincent Ryan, Rosanna Lee/**
 * Implements the CRAM-MD5 SASL client-side mechanism.
 * (<A HREF="http://www.ietf.org/rfc/rfc2195.txt">RFC 2195</A>).
 * CRAM-MD5 has no initial response. It receives bytes from
 * the server as a challenge, which it hashes by using MD5 and the password.
 * It concatenates the authentication ID with this result and returns it
 * as the response to the challenge. At that point, the exchange is complete.
 *
 * @author Vincent Ryan
 * @author Rosanna Lee
 */
final class CramMD5Client extends CramMD5Base implements SaslClient {
    private String username;

    
Creates a SASL mechanism with client credentials that it needs
to participate in CRAM-MD5 authentication exchange with the server.
Params:
authID – A  non-null string representing the principal
being authenticated.
pw – A non-null String or byte[]
containing the password. If it is an array, it is first cloned./**
     * Creates a SASL mechanism with client credentials that it needs
     * to participate in CRAM-MD5 authentication exchange with the server.
     *
     * @param authID A  non-null string representing the principal
     * being authenticated.
     *
     * @param pw A non-null String or byte[]
     * containing the password. If it is an array, it is first cloned.
     */
    CramMD5Client(String authID, byte[] pw) throws SaslException {
        if (authID == null || pw == null) {
            throw new SaslException(
                "CRAM-MD5: authentication ID and password must be specified");
        }

        username = authID;
        this.pw = pw;  // caller should have already cloned
    }

    
CRAM-MD5 has no initial response.
/**
     * CRAM-MD5 has no initial response.
     */
    public boolean hasInitialResponse() {
        return false;
    }

    
Processes the challenge data.
The server sends a challenge data using which the client must
compute an MD5-digest with its password as the key.
Params:
challengeData – A non-null byte array containing the challenge
       data from the server.
Throws:
SaslException – if platform does not have MD5 support
IllegalStateException – if this method is invoked more than once.
Returns:
A non-null byte array containing the response to be sent to
       the server./**
     * Processes the challenge data.
     *
     * The server sends a challenge data using which the client must
     * compute an MD5-digest with its password as the key.
     *
     * @param challengeData A non-null byte array containing the challenge
     *        data from the server.
     * @return A non-null byte array containing the response to be sent to
     *        the server.
     * @throws SaslException if platform does not have MD5 support
     * @throws IllegalStateException if this method is invoked more than once.
     */
    public byte[] evaluateChallenge(byte[] challengeData)
        throws SaslException {

        // See if we've been here before
        if (completed) {
            throw new IllegalStateException(
                "CRAM-MD5 authentication already completed");
        }

        if (aborted) {
            throw new IllegalStateException(
                "CRAM-MD5 authentication previously aborted due to error");
        }

        // generate a keyed-MD5 digest from the user's password and challenge.
        try {
            if (logger.isLoggable(Level.FINE)) {
                logger.log(Level.FINE, "CRAMCLNT01:Received challenge: {0}",
                    new String(challengeData, UTF_8));
            }

            String digest = HMAC_MD5(pw, challengeData);

            // clear it when we no longer need it
            clearPassword();

            // response is username + " " + digest
            String resp = username + " " + digest;

            logger.log(Level.FINE, "CRAMCLNT02:Sending response: {0}", resp);

            completed = true;

            return resp.getBytes(UTF_8);
        } catch (java.security.NoSuchAlgorithmException e) {
            aborted = true;
            throw new SaslException("MD5 algorithm not available on platform", e);
        }
    }
}