Java tutorial
/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this file, * You can obtain one at http://mozilla.org/MPL/2.0/. */ package org.mozilla.gecko.sync.jpake; import java.io.UnsupportedEncodingException; import java.math.BigInteger; import java.util.LinkedList; import java.util.Queue; import org.json.simple.JSONObject; import org.mozilla.apache.commons.codec.binary.Base64; import org.mozilla.gecko.sync.ExtendedJSONObject; import org.mozilla.gecko.sync.Logger; import org.mozilla.gecko.sync.ThreadPool; import org.mozilla.gecko.sync.Utils; import org.mozilla.gecko.sync.crypto.CryptoException; import org.mozilla.gecko.sync.crypto.CryptoInfo; import org.mozilla.gecko.sync.crypto.KeyBundle; import org.mozilla.gecko.sync.crypto.NoKeyBundleException; import org.mozilla.gecko.sync.jpake.stage.CompleteStage; import org.mozilla.gecko.sync.jpake.stage.ComputeFinalStage; import org.mozilla.gecko.sync.jpake.stage.ComputeKeyVerificationStage; import org.mozilla.gecko.sync.jpake.stage.ComputeStepOneStage; import org.mozilla.gecko.sync.jpake.stage.ComputeStepTwoStage; import org.mozilla.gecko.sync.jpake.stage.DecryptDataStage; import org.mozilla.gecko.sync.jpake.stage.GetChannelStage; import org.mozilla.gecko.sync.jpake.stage.GetRequestStage; import org.mozilla.gecko.sync.jpake.stage.JPakeStage; import org.mozilla.gecko.sync.jpake.stage.PutRequestStage; import org.mozilla.gecko.sync.jpake.stage.VerifyPairingStage; import org.mozilla.gecko.sync.setup.Constants; import org.mozilla.gecko.sync.setup.activities.SetupSyncActivity; import ch.boye.httpclientandroidlib.entity.StringEntity; public class JPakeClient { private static String LOG_TAG = "JPakeClient"; // J-PAKE constants. public final static int REQUEST_TIMEOUT = 60 * 1000; // 1 min public final static int KEYEXCHANGE_VERSION = 3; public final static String JPAKE_VERIFY_VALUE = "0123456789ABCDEF"; private final static String JPAKE_SIGNERID_SENDER = "sender"; private final static String JPAKE_SIGNERID_RECEIVER = "receiver"; private final static int JPAKE_LENGTH_SECRET = 8; private final static int JPAKE_LENGTH_CLIENTID = 256; private final static int MAX_TRIES = 10; private final static int MAX_TRIES_FIRST_MSG = 300; private final static int MAX_TRIES_LAST_MSG = 300; // J-PAKE session values. public String clientId; public String secret; public String myEtag; public String mySignerId; public String theirEtag; public String theirSignerId; public String jpakeServer; // J-PAKE state. public boolean paired = false; public boolean finished = false; // J-PAKE values. public int jpakePollInterval; public int jpakeMaxTries; public String channel; public String channelUrl; // J-PAKE session data. public KeyBundle myKeyBundle; public JSONObject jCreds; public ExtendedJSONObject jOutgoing; public ExtendedJSONObject jIncoming; public JPakeParty jParty; public JPakeNumGenerator numGen; public int pollTries = 0; // UI controller. private SetupSyncActivity controllerActivity; private Queue<JPakeStage> stages; public JPakeClient(SetupSyncActivity activity) { controllerActivity = activity; jpakeServer = "https://setup.services.mozilla.com/"; jpakePollInterval = 1 * 1000; // 1 second jpakeMaxTries = MAX_TRIES; if (!jpakeServer.endsWith("/")) { jpakeServer += "/"; } setClientId(); numGen = new JPakeNumGeneratorRandom(); } /** * Set up Sender sequence of stages for J-PAKE. (sender of credentials) * */ private void prepareSenderStages() { Queue<JPakeStage> jStages = new LinkedList<JPakeStage>(); jStages.add(new ComputeStepOneStage()); jStages.add(new GetRequestStage()); jStages.add(new PutRequestStage()); jStages.add(new ComputeStepTwoStage()); jStages.add(new GetRequestStage()); jStages.add(new PutRequestStage()); jStages.add(new ComputeFinalStage()); jStages.add(new GetRequestStage()); jStages.add(new VerifyPairingStage()); // Calls onPaired if verified. stages = jStages; } /** * Set up Receiver sequence of stages for J-PAKE. (receiver of credentials) * */ private void prepareReceiverStages() { Queue<JPakeStage> jStages = new LinkedList<JPakeStage>(); jStages.add(new GetChannelStage()); jStages.add(new ComputeStepOneStage()); jStages.add(new PutRequestStage()); jStages.add(new GetRequestStage()); jStages.add(new JPakeStage() { @Override public void execute(JPakeClient jpakeClient) { // Notify controller that pairing has started. jpakeClient.onPairingStart(); // Switch back to smaller time-out. jpakeClient.jpakeMaxTries = JPakeClient.MAX_TRIES; jpakeClient.runNextStage(); } }); jStages.add(new ComputeStepTwoStage()); jStages.add(new PutRequestStage()); jStages.add(new GetRequestStage()); jStages.add(new ComputeFinalStage()); jStages.add(new ComputeKeyVerificationStage()); jStages.add(new PutRequestStage()); jStages.add(new JPakeStage() { @Override public void execute(JPakeClient jpakeClient) { jpakeMaxTries = MAX_TRIES_LAST_MSG; jpakeClient.runNextStage(); } }); jStages.add(new GetRequestStage()); jStages.add(new DecryptDataStage()); jStages.add(new CompleteStage()); stages = jStages; } /** * * Pairing using PIN provided on other device. Functionality available only * when a Sync account has already been set up. * * @param pin * 12-character string containing PIN entered by the user. */ public void pairWithPin(String pin) { mySignerId = JPAKE_SIGNERID_SENDER; theirSignerId = JPAKE_SIGNERID_RECEIVER; jParty = new JPakeParty(mySignerId); // Extract secret and server channel. secret = pin.substring(0, JPAKE_LENGTH_SECRET); channel = pin.substring(JPAKE_LENGTH_SECRET); channelUrl = jpakeServer + channel; prepareSenderStages(); runNextStage(); } /** * * Initiate pairing and receive data, without having received a PIN. The PIN * will be generated and passed on to the controller to be displayed to the * user. * * Starts J-PAKE protocol. */ public void receiveNoPin() { mySignerId = JPAKE_SIGNERID_RECEIVER; theirSignerId = JPAKE_SIGNERID_SENDER; jParty = new JPakeParty(mySignerId); // TODO: fetch from prefs jpakeMaxTries = MAX_TRIES_FIRST_MSG; createSecret(); prepareReceiverStages(); runNextStage(); } /** * Run next stage of J-PAKE. */ public void runNextStage() { if (finished || stages.size() == 0) { Logger.debug(LOG_TAG, "All stages complete."); return; } JPakeStage nextStage = null; try { nextStage = stages.remove(); Logger.debug(LOG_TAG, "starting stage " + nextStage.toString()); nextStage.execute(this); } catch (Exception e) { Logger.error(LOG_TAG, "Exception in stage " + nextStage, e); abort("Stage exception."); } } /** * Abort J-PAKE. * * @param reason * Reason for abort. */ public void abort(String reason) { finished = true; controllerActivity.displayAbort(reason); } /* Static helper methods used by stages. */ /** * Run on a different thread from the thread pool. * * @param run * Runnable to run on separate thread. */ public static void runOnThread(Runnable run) { ThreadPool.run(run); } /** * * @param secretString * String to convert to BigInteger * @return BigInteger representation of secretString * * @throws java.io.UnsupportedEncodingException */ public static BigInteger secretAsBigInteger(String secretString) throws UnsupportedEncodingException { return new BigInteger(secretString.getBytes("UTF-8")); } /** * Helper method for doing actual encryption. * * Input: String of JSONObject KeyBundle with keys for encryption * * Output: ExtendedJSONObject with IV, ciphertext, hmac (if sender) * * @throws org.mozilla.gecko.sync.crypto.CryptoException * @throws java.io.UnsupportedEncodingException */ public static ExtendedJSONObject encryptPayload(String data, KeyBundle keyBundle, boolean makeHmac) throws UnsupportedEncodingException, CryptoException { if (keyBundle == null) { throw new NoKeyBundleException(); } byte[] cleartextBytes = data.getBytes("UTF-8"); CryptoInfo encrypted = CryptoInfo.encrypt(cleartextBytes, keyBundle); ExtendedJSONObject payload = new ExtendedJSONObject(); String message64 = new String(Base64.encodeBase64(encrypted.getMessage())); String iv64 = new String(Base64.encodeBase64(encrypted.getIV())); payload.put(Constants.JSON_KEY_CIPHERTEXT, message64); payload.put(Constants.JSON_KEY_IV, iv64); if (makeHmac) { String hmacHex = Utils.byte2hex(encrypted.getHMAC()); payload.put(Constants.JSON_KEY_HMAC, hmacHex); } return payload; } /* * Helper for turning a JSON object into a payload. * * @param body JSONObject body to be converted to StringEntity. * @return StringEntity representation of JSONObject. * * @throws UnsupportedEncodingException */ public static StringEntity jsonEntity(JSONObject body) throws UnsupportedEncodingException { StringEntity entity = new StringEntity(body.toJSONString(), "UTF-8"); entity.setContentType("application/json"); return entity; } /* * Controller methods. */ public void makeAndDisplayPin(String channel) { controllerActivity.displayPin(secret + channel); } public void onPairingStart() { Logger.debug(LOG_TAG, "Pairing started."); controllerActivity.onPairingStart(); } public void onPaired() { Logger.debug(LOG_TAG, "Pairing completed. Starting credential exchange."); controllerActivity.onPaired(); } public void complete(JSONObject credentials) { controllerActivity.onComplete(credentials); } /* * Called from controller, with Sync credentials to be encrypted and sent. */ public void sendAndComplete(JSONObject jObj) throws JPakeNoActivePairingException { if (!paired || finished) { Logger.error(LOG_TAG, "Can't send data, no active pairing!"); throw new JPakeNoActivePairingException(); } stages.clear(); stages.add(new PutRequestStage()); stages.add(new CompleteStage()); // Encrypt data to send and set as jOutgoing. String outData = jObj.toJSONString(); encryptData(myKeyBundle, outData); // Start stages for sending credentials. runNextStage(); } /* Setup helper functions */ /* * Generates and sets a clientId for communications with JPAKE setup server. */ private void setClientId() { byte[] rBytes = Utils.generateRandomBytes(JPAKE_LENGTH_CLIENTID / 2); StringBuilder id = new StringBuilder(); for (byte b : rBytes) { String hexString = Integer.toHexString(b); if (hexString.length() == 1) { hexString = "0" + hexString; } int len = hexString.length(); id.append(hexString.substring(len - 2, len)); } clientId = id.toString(); } /* * Generates and sets a JPAKE PIN to be displayed to user. */ private void createSecret() { // 0-9a-z without 1,l,o,0 String key = "23456789abcdefghijkmnpqrstuvwxyz"; int keylen = key.length(); byte[] rBytes = Utils.generateRandomBytes(JPAKE_LENGTH_SECRET); StringBuilder secret = new StringBuilder(); for (byte b : rBytes) { secret.append(key.charAt(Math.abs(b) * keylen / 256)); } this.secret = secret.toString(); } /* * * Encrypt payload and package into jOutgoing for sending with a PUT request. * * @param keyBundle Encryption keys derived during J-PAKE. * * @param payload Credentials data to be encrypted. */ private void encryptData(KeyBundle keyBundle, String payload) { Logger.debug(LOG_TAG, "Encrypting data."); ExtendedJSONObject jPayload = null; try { jPayload = encryptPayload(payload, keyBundle, true); } catch (UnsupportedEncodingException e) { Logger.error(LOG_TAG, "Failed to encrypt data.", e); abort(Constants.JPAKE_ERROR_INTERNAL); return; } catch (CryptoException e) { Logger.error(LOG_TAG, "Failed to encrypt data.", e); abort(Constants.JPAKE_ERROR_INTERNAL); return; } jOutgoing = new ExtendedJSONObject(); jOutgoing.put(Constants.JSON_KEY_TYPE, mySignerId + "3"); jOutgoing.put(Constants.JSON_KEY_VERSION, KEYEXCHANGE_VERSION); jOutgoing.put(Constants.JSON_KEY_PAYLOAD, jPayload.object); } }