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package com.sun.security.sasl;

import javax.security.sasl.*;
import javax.security.auth.callback.*;
import java.util.Random;
import java.util.Map;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.security.NoSuchAlgorithmException;

import java.util.logging.Level;

Implements the CRAM-MD5 SASL server-side mechanism. (RFC 2195). CRAM-MD5 has no initial response. client <---- M={random, timestamp, server-fqdn} ------- server client ----- {username HMAC_MD5(pw, M)} --------------> server CallbackHandler must be able to handle the following callbacks: - NameCallback: default name is name of user for whom to get password - PasswordCallback: must fill in password; if empty, no pw - AuthorizeCallback: must setAuthorized() and canonicalized authorization id - auth id == authzid, but needed to get canonicalized authzid
Author:Rosanna Lee
/** * Implements the CRAM-MD5 SASL server-side mechanism. * (<A HREF="http://www.ietf.org/rfc/rfc2195.txt">RFC 2195</A>). * CRAM-MD5 has no initial response. * * client <---- M={random, timestamp, server-fqdn} ------- server * client ----- {username HMAC_MD5(pw, M)} --------------> server * * CallbackHandler must be able to handle the following callbacks: * - NameCallback: default name is name of user for whom to get password * - PasswordCallback: must fill in password; if empty, no pw * - AuthorizeCallback: must setAuthorized() and canonicalized authorization id * - auth id == authzid, but needed to get canonicalized authzid * * @author Rosanna Lee */
final class CramMD5Server extends CramMD5Base implements SaslServer { private String fqdn; private byte[] challengeData = null; private String authzid; private CallbackHandler cbh;
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. */
CramMD5Server(String protocol, String serverFqdn, Map<String, ?> props, CallbackHandler cbh) throws SaslException { if (serverFqdn == null) { throw new SaslException( "CRAM-MD5: fully qualified server name must be specified"); } fqdn = serverFqdn; this.cbh = cbh; }
Generates challenge based on response sent by client. CRAM-MD5 has no initial response. First call generates challenge. Second call verifies client response. If authentication fails, throws SaslException.
Params:
  • responseData – A non-null byte array containing the response data from the client.
Throws:
Returns:A non-null byte array containing the challenge to be sent to the client for the first call; null when 2nd call is successful.
/** * Generates challenge based on response sent by client. * * CRAM-MD5 has no initial response. * First call generates challenge. * Second call verifies client response. If authentication fails, throws * SaslException. * * @param responseData A non-null byte array containing the response * data from the client. * @return A non-null byte array containing the challenge to be sent to * the client for the first call; null when 2nd call is successful. * @throws SaslException If authentication fails. */
public byte[] evaluateResponse(byte[] responseData) 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"); } try { if (challengeData == null) { if (responseData.length != 0) { aborted = true; throw new SaslException( "CRAM-MD5 does not expect any initial response"); } // Generate challenge {random, timestamp, fqdn} Random random = new Random(); long rand = random.nextLong(); long timestamp = System.currentTimeMillis(); StringBuffer buf = new StringBuffer(); buf.append('<'); buf.append(rand); buf.append('.'); buf.append(timestamp); buf.append('@'); buf.append(fqdn); buf.append('>'); String challengeStr = buf.toString(); logger.log(Level.FINE, "CRAMSRV01:Generated challenge: {0}", challengeStr); challengeData = challengeStr.getBytes("UTF8"); return challengeData.clone(); } else { // Examine response to see if correctly encrypted challengeData if(logger.isLoggable(Level.FINE)) { logger.log(Level.FINE, "CRAMSRV02:Received response: {0}", new String(responseData, "UTF8")); } // Extract username from response int ulen = 0; for (int i = 0; i < responseData.length; i++) { if (responseData[i] == ' ') { ulen = i; break; } } if (ulen == 0) { aborted = true; throw new SaslException( "CRAM-MD5: Invalid response; space missing"); } String username = new String(responseData, 0, ulen, "UTF8"); logger.log(Level.FINE, "CRAMSRV03:Extracted username: {0}", username); // Get user's password NameCallback ncb = new NameCallback("CRAM-MD5 authentication ID: ", username); PasswordCallback pcb = new PasswordCallback("CRAM-MD5 password: ", false); cbh.handle(new Callback[]{ncb,pcb}); char pwChars[] = pcb.getPassword(); if (pwChars == null || pwChars.length == 0) { // user has no password; OK to disclose to server aborted = true; throw new SaslException( "CRAM-MD5: username not found: " + username); } pcb.clearPassword(); String pwStr = new String(pwChars); for (int i = 0; i < pwChars.length; i++) { pwChars[i] = 0; } pw = pwStr.getBytes("UTF8"); // Generate a keyed-MD5 digest from the user's password and // original challenge. String digest = HMAC_MD5(pw, challengeData); logger.log(Level.FINE, "CRAMSRV04:Expecting digest: {0}", digest); // clear pw when we no longer need it clearPassword(); // Check whether digest is as expected byte [] expectedDigest = digest.getBytes("UTF8"); int digestLen = responseData.length - ulen - 1; if (expectedDigest.length != digestLen) { aborted = true; throw new SaslException("Invalid response"); } int j = 0; for (int i = ulen + 1; i < responseData.length ; i++) { if (expectedDigest[j++] != responseData[i]) { aborted = true; throw new SaslException("Invalid response"); } } // All checks out, use AuthorizeCallback to canonicalize name AuthorizeCallback acb = new AuthorizeCallback(username, username); cbh.handle(new Callback[]{acb}); if (acb.isAuthorized()) { authzid = acb.getAuthorizedID(); } else { // Not authorized aborted = true; throw new SaslException( "CRAM-MD5: user not authorized: " + username); } logger.log(Level.FINE, "CRAMSRV05:Authorization id: {0}", authzid); completed = true; return null; } } catch (UnsupportedEncodingException e) { aborted = true; throw new SaslException("UTF8 not available on platform", e); } catch (NoSuchAlgorithmException e) { aborted = true; throw new SaslException("MD5 algorithm not available on platform", e); } catch (UnsupportedCallbackException e) { aborted = true; throw new SaslException("CRAM-MD5 authentication failed", e); } catch (SaslException e) { throw e; // rethrow } catch (IOException e) { aborted = true; throw new SaslException("CRAM-MD5 authentication failed", e); } } public String getAuthorizationID() { if (completed) { return authzid; } else { throw new IllegalStateException( "CRAM-MD5 authentication not completed"); } } }