358 lines
12 KiB
Java
358 lines
12 KiB
Java
/**
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*
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* Copyright 2014 Florian Schmaus
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.jivesoftware.smack.sasl.core;
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import java.security.InvalidKeyException;
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import java.security.SecureRandom;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.Map;
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import javax.security.auth.callback.CallbackHandler;
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import org.jivesoftware.smack.SmackException;
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import org.jivesoftware.smack.sasl.SASLMechanism;
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import org.jivesoftware.smack.util.ByteUtils;
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import org.jivesoftware.smack.util.MAC;
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import org.jivesoftware.smack.util.SHA1;
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import org.jivesoftware.smack.util.stringencoder.Base64;
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import org.jxmpp.util.cache.Cache;
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import org.jxmpp.util.cache.LruCache;
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public class SCRAMSHA1Mechanism extends SASLMechanism {
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public static final String NAME = "SCRAM-SHA-1";
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private static final int RANDOM_ASCII_BYTE_COUNT = 32;
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private static final byte[] CLIENT_KEY_BYTES = toBytes("Client Key");
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private static final byte[] SERVER_KEY_BYTES = toBytes("Server Key");
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private static final byte[] ONE = new byte[] { 0, 0, 0, 1 };
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private static final SecureRandom RANDOM = new SecureRandom();
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private static final Cache<String, Keys> CACHE = new LruCache<String, Keys>(10);
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private enum State {
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INITIAL,
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AUTH_TEXT_SENT,
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RESPONSE_SENT,
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VALID_SERVER_RESPONSE,
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}
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/**
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* The state of the this instance of SASL SCRAM-SHA1 authentication.
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*/
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private State state = State.INITIAL;
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/**
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* The client's random ASCII which is used as nonce
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*/
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private String clientRandomAscii;
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private String clientFirstMessageBare;
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private byte[] serverSignature;
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@Override
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protected void authenticateInternal(CallbackHandler cbh) throws SmackException {
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throw new UnsupportedOperationException("CallbackHandler not (yet) supported");
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}
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@Override
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protected byte[] getAuthenticationText() throws SmackException {
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clientRandomAscii = getRandomAscii();
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String saslPrepedAuthcId = saslPrep(authenticationId);
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clientFirstMessageBare = "n=" + escape(saslPrepedAuthcId) + ",r=" + clientRandomAscii;
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String clientFirstMessage = getGS2Header() + clientFirstMessageBare;
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state = State.AUTH_TEXT_SENT;
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return toBytes(clientFirstMessage);
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}
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@Override
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public String getName() {
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return NAME;
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}
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@Override
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public int getPriority() {
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return 110;
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}
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@Override
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public SCRAMSHA1Mechanism newInstance() {
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return new SCRAMSHA1Mechanism();
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}
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@Override
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public void checkIfSuccessfulOrThrow() throws SmackException {
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if (state != State.VALID_SERVER_RESPONSE) {
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throw new SmackException("SCRAM-SHA1 is missing valid server response");
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}
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}
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@Override
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public boolean authzidSupported() {
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return true;
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}
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@Override
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protected byte[] evaluateChallenge(byte[] challenge) throws SmackException {
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final String challengeString = new String(challenge);
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switch (state) {
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case AUTH_TEXT_SENT:
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final String serverFirstMessage = challengeString;
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Map<Character, String> attributes = parseAttributes(challengeString);
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// Handle server random ASCII (nonce)
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String rvalue = attributes.get('r');
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if (rvalue == null) {
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throw new SmackException("Server random ASCII is null");
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}
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if (rvalue.length() <= clientRandomAscii.length()) {
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throw new SmackException("Server random ASCII is shorter then client random ASCII");
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}
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String receivedClientRandomAscii = rvalue.substring(0, clientRandomAscii.length());
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if (!receivedClientRandomAscii.equals(clientRandomAscii)) {
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throw new SmackException("Received client random ASCII does not match client random ASCII");
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}
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// Handle iterations
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int iterations;
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String iterationsString = attributes.get('i');
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if (iterationsString == null) {
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throw new SmackException("Iterations attribute not set");
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}
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try {
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iterations = Integer.parseInt(iterationsString);
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}
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catch (NumberFormatException e) {
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throw new SmackException("Exception parsing iterations", e);
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}
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// Handle salt
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String salt = attributes.get('s');
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if (salt == null) {
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throw new SmackException("SALT not send");
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}
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// Parsing and error checking is done, we can now begin to calculate the values
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// First the client-final-message-without-proof
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String clientFinalMessageWithoutProof = "c=" + Base64.encode(getGS2Header()) + ",r=" + rvalue;
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// AuthMessage := client-first-message-bare + "," + server-first-message + "," +
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// client-final-message-without-proof
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byte[] authMessage = toBytes(clientFirstMessageBare + ',' + serverFirstMessage + ','
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+ clientFinalMessageWithoutProof);
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// RFC 5802 § 5.1 "Note that a client implementation MAY cache ClientKey&ServerKey … for later reauthentication …
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// as it is likely that the server is going to advertise the same salt value upon reauthentication."
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final String cacheKey = password + ',' + salt;
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byte[] serverKey, clientKey;
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Keys keys = CACHE.get(cacheKey);
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if (keys == null) {
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// SaltedPassword := Hi(Normalize(password), salt, i)
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byte[] saltedPassword = hi(saslPrep(password), Base64.decode(salt), iterations);
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// ServerKey := HMAC(SaltedPassword, "Server Key")
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serverKey = hmac(saltedPassword, SERVER_KEY_BYTES);
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// ClientKey := HMAC(SaltedPassword, "Client Key")
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clientKey = hmac(saltedPassword, CLIENT_KEY_BYTES);
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keys = new Keys(clientKey, serverKey);
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CACHE.put(cacheKey, keys);
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}
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else {
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serverKey = keys.serverKey;
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clientKey = keys.clientKey;
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}
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// ServerSignature := HMAC(ServerKey, AuthMessage)
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serverSignature = hmac(serverKey, authMessage);
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// StoredKey := H(ClientKey)
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byte[] storedKey = SHA1.bytes(clientKey);
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// ClientSignature := HMAC(StoredKey, AuthMessage)
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byte[] clientSignature = hmac(storedKey, authMessage);
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// ClientProof := ClientKey XOR ClientSignature
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byte[] clientProof = new byte[clientKey.length];
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for (int i = 0; i < clientProof.length; i++) {
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clientProof[i] = (byte) (clientKey[i] ^ clientSignature[i]);
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}
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String clientFinalMessage = clientFinalMessageWithoutProof + ",p=" + Base64.encodeToString(clientProof);
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state = State.RESPONSE_SENT;
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return toBytes(clientFinalMessage);
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case RESPONSE_SENT:
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String clientCalculatedServerFinalMessage = "v=" + Base64.encodeToString(serverSignature);
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if (!clientCalculatedServerFinalMessage.equals(challengeString)) {
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throw new SmackException("Server final message does not match calculated one");
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}
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state = State.VALID_SERVER_RESPONSE;
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break;
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default:
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throw new SmackException("Invalid state");
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}
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return null;
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}
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private final String getGS2Header() {
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String authzidPortion = "";
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if (authorizationId != null) {
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authzidPortion = "a=" + authorizationId;
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}
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return "n," + authzidPortion + ",";
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}
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private static Map<Character, String> parseAttributes(String string) throws SmackException {
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if (string.length() == 0) {
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return Collections.emptyMap();
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}
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String[] keyValuePairs = string.split(",");
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Map<Character, String> res = new HashMap<Character, String>(keyValuePairs.length, 1);
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for (String keyValuePair : keyValuePairs) {
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if (keyValuePair.length() < 3) {
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throw new SmackException("Invalid Key-Value pair: " + keyValuePair);
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}
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char key = keyValuePair.charAt(0);
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if (keyValuePair.charAt(1) != '=') {
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throw new SmackException("Invalid Key-Value pair: " + keyValuePair);
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}
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String value = keyValuePair.substring(2);
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res.put(key, value);
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}
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return res;
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}
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/**
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* Generate random ASCII.
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* <p>
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* This method is non-static and package-private for unit testing purposes.
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* </p>
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* @return A String of 32 random printable ASCII characters.
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*/
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String getRandomAscii() {
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int count = 0;
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char[] randomAscii = new char[RANDOM_ASCII_BYTE_COUNT];
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while (count < RANDOM_ASCII_BYTE_COUNT) {
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int r = RANDOM.nextInt(128);
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char c = (char) r;
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// RFC 5802 § 5.1 specifies 'r:' to exclude the ',' character and to be only printable ASCII characters
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if (!isPrintableNonCommaAsciiChar(c)) {
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continue;
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}
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randomAscii[count++] = c;
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}
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return new String(randomAscii);
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}
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private static boolean isPrintableNonCommaAsciiChar(char c) {
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if (c == ',') {
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return false;
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}
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return c >= 32 && c < 127;
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}
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/**
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* Escapes usernames or passwords for SASL SCRAM-SHA1.
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* <p>
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* According to RFC 5802 § 5.1 'n:'
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* "The characters ',' or '=' in usernames are sent as '=2C' and '=3D' respectively."
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* </p>
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*
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* @param string
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* @return the escaped string
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*/
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private static String escape(String string) {
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StringBuilder sb = new StringBuilder((int) (string.length() * 1.1));
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for (int i = 0; i < string.length(); i++) {
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char c = string.charAt(i);
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switch (c) {
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case ',':
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sb.append("=2C");
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break;
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case '=':
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sb.append("=3D");
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break;
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default:
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sb.append(c);
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break;
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}
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}
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return sb.toString();
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}
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/**
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* RFC 5802 § 2.2 HMAC(key, str)
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*
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* @param key
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* @param str
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* @return the HMAC-SHA1 value of the input.
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* @throws SmackException
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*/
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private static byte[] hmac(byte[] key, byte[] str) throws SmackException {
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try {
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return MAC.hmacsha1(key, str);
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}
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catch (InvalidKeyException e) {
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throw new SmackException(NAME + " HMAC-SHA1 Exception", e);
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}
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}
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/**
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* RFC 5802 § 2.2 Hi(str, salt, i)
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* <p>
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* Hi() is, essentially, PBKDF2 [RFC2898] with HMAC() as the pseudorandom function
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* (PRF) and with dkLen == output length of HMAC() == output length of H().
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* </p>
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*
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* @param str
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* @param salt
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* @param iterations
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* @return the result of the Hi function.
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* @throws SmackException
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*/
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private static byte[] hi(String str, byte[] salt, int iterations) throws SmackException {
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byte[] key = str.getBytes();
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// U1 := HMAC(str, salt + INT(1))
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byte[] u = hmac(key, ByteUtils.concact(salt, ONE));
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byte[] res = u.clone();
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for (int i = 1; i < iterations; i++) {
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u = hmac(key, u);
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for (int j = 0; j < u.length; j++) {
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res[j] ^= u[j];
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}
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}
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return res;
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}
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private static class Keys {
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private final byte[] clientKey;
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private final byte[] serverKey;
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public Keys(byte[] clientKey, byte[] serverKey) {
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this.clientKey = clientKey;
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this.serverKey = serverKey;
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}
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}
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}
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