mirror of
https://github.com/oxen-io/session-android.git
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371 lines
15 KiB
Java
371 lines
15 KiB
Java
/**
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* Copyright (C) 2011 Whisper Systems
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* Copyright (C) 2013 Open Whisper Systems
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package org.thoughtcrime.securesms.crypto;
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import android.content.Context;
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import android.content.SharedPreferences;
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import android.support.annotation.NonNull;
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import android.support.annotation.Nullable;
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import android.text.TextUtils;
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import android.util.Log;
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import org.thoughtcrime.securesms.util.Base64;
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import org.thoughtcrime.securesms.util.Util;
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import org.whispersystems.libsignal.InvalidKeyException;
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import org.whispersystems.libsignal.ecc.Curve;
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import org.whispersystems.libsignal.ecc.ECKeyPair;
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import org.whispersystems.libsignal.ecc.ECPrivateKey;
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import org.whispersystems.libsignal.ecc.ECPublicKey;
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import java.io.IOException;
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import java.security.GeneralSecurityException;
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import java.security.NoSuchAlgorithmException;
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import java.security.SecureRandom;
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import java.security.spec.InvalidKeySpecException;
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import java.util.Arrays;
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import javax.crypto.Cipher;
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import javax.crypto.KeyGenerator;
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import javax.crypto.Mac;
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import javax.crypto.SecretKey;
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import javax.crypto.SecretKeyFactory;
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import javax.crypto.spec.PBEKeySpec;
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import javax.crypto.spec.PBEParameterSpec;
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import javax.crypto.spec.SecretKeySpec;
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/**
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* Helper class for generating and securely storing a MasterSecret.
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*
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* @author Moxie Marlinspike
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*/
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public class MasterSecretUtil {
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public static final String UNENCRYPTED_PASSPHRASE = "unencrypted";
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public static final String PREFERENCES_NAME = "SecureSMS-Preferences";
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private static final String ASYMMETRIC_LOCAL_PUBLIC_DJB = "asymmetric_master_secret_curve25519_public";
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private static final String ASYMMETRIC_LOCAL_PRIVATE_DJB = "asymmetric_master_secret_curve25519_private";
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public static MasterSecret changeMasterSecretPassphrase(Context context,
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MasterSecret masterSecret,
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String newPassphrase)
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{
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try {
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byte[] combinedSecrets = Util.combine(masterSecret.getEncryptionKey().getEncoded(),
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masterSecret.getMacKey().getEncoded());
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byte[] encryptionSalt = generateSalt();
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int iterations = generateIterationCount(newPassphrase, encryptionSalt);
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byte[] encryptedMasterSecret = encryptWithPassphrase(encryptionSalt, iterations, combinedSecrets, newPassphrase);
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byte[] macSalt = generateSalt();
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byte[] encryptedAndMacdMasterSecret = macWithPassphrase(macSalt, iterations, encryptedMasterSecret, newPassphrase);
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save(context, "encryption_salt", encryptionSalt);
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save(context, "mac_salt", macSalt);
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save(context, "passphrase_iterations", iterations);
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save(context, "master_secret", encryptedAndMacdMasterSecret);
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save(context, "passphrase_initialized", true);
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return masterSecret;
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} catch (GeneralSecurityException gse) {
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throw new AssertionError(gse);
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}
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}
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public static MasterSecret changeMasterSecretPassphrase(Context context,
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String originalPassphrase,
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String newPassphrase)
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throws InvalidPassphraseException
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{
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MasterSecret masterSecret = getMasterSecret(context, originalPassphrase);
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changeMasterSecretPassphrase(context, masterSecret, newPassphrase);
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return masterSecret;
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}
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public static MasterSecret getMasterSecret(Context context, String passphrase)
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throws InvalidPassphraseException
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{
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try {
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byte[] encryptedAndMacdMasterSecret = retrieve(context, "master_secret");
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byte[] macSalt = retrieve(context, "mac_salt");
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int iterations = retrieve(context, "passphrase_iterations", 100);
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byte[] encryptedMasterSecret = verifyMac(macSalt, iterations, encryptedAndMacdMasterSecret, passphrase);
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byte[] encryptionSalt = retrieve(context, "encryption_salt");
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byte[] combinedSecrets = decryptWithPassphrase(encryptionSalt, iterations, encryptedMasterSecret, passphrase);
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byte[] encryptionSecret = Util.split(combinedSecrets, 16, 20)[0];
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byte[] macSecret = Util.split(combinedSecrets, 16, 20)[1];
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return new MasterSecret(new SecretKeySpec(encryptionSecret, "AES"),
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new SecretKeySpec(macSecret, "HmacSHA1"));
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} catch (GeneralSecurityException e) {
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Log.w("keyutil", e);
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return null; //XXX
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} catch (IOException e) {
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Log.w("keyutil", e);
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return null; //XXX
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}
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}
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public static AsymmetricMasterSecret getAsymmetricMasterSecret(@NonNull Context context,
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@Nullable MasterSecret masterSecret)
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{
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try {
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byte[] djbPublicBytes = retrieve(context, ASYMMETRIC_LOCAL_PUBLIC_DJB);
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byte[] djbPrivateBytes = retrieve(context, ASYMMETRIC_LOCAL_PRIVATE_DJB);
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ECPublicKey djbPublicKey = null;
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ECPrivateKey djbPrivateKey = null;
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if (djbPublicBytes != null) {
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djbPublicKey = Curve.decodePoint(djbPublicBytes, 0);
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}
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if (masterSecret != null) {
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MasterCipher masterCipher = new MasterCipher(masterSecret);
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if (djbPrivateBytes != null) {
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djbPrivateKey = masterCipher.decryptKey(djbPrivateBytes);
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}
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}
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return new AsymmetricMasterSecret(djbPublicKey, djbPrivateKey);
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} catch (InvalidKeyException | IOException ike) {
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throw new AssertionError(ike);
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}
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}
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public static AsymmetricMasterSecret generateAsymmetricMasterSecret(Context context,
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MasterSecret masterSecret)
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{
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MasterCipher masterCipher = new MasterCipher(masterSecret);
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ECKeyPair keyPair = Curve.generateKeyPair();
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save(context, ASYMMETRIC_LOCAL_PUBLIC_DJB, keyPair.getPublicKey().serialize());
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save(context, ASYMMETRIC_LOCAL_PRIVATE_DJB, masterCipher.encryptKey(keyPair.getPrivateKey()));
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return new AsymmetricMasterSecret(keyPair.getPublicKey(), keyPair.getPrivateKey());
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}
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public static MasterSecret generateMasterSecret(Context context, String passphrase) {
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try {
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byte[] encryptionSecret = generateEncryptionSecret();
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byte[] macSecret = generateMacSecret();
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byte[] masterSecret = Util.combine(encryptionSecret, macSecret);
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byte[] encryptionSalt = generateSalt();
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int iterations = generateIterationCount(passphrase, encryptionSalt);
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byte[] encryptedMasterSecret = encryptWithPassphrase(encryptionSalt, iterations, masterSecret, passphrase);
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byte[] macSalt = generateSalt();
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byte[] encryptedAndMacdMasterSecret = macWithPassphrase(macSalt, iterations, encryptedMasterSecret, passphrase);
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save(context, "encryption_salt", encryptionSalt);
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save(context, "mac_salt", macSalt);
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save(context, "passphrase_iterations", iterations);
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save(context, "master_secret", encryptedAndMacdMasterSecret);
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save(context, "passphrase_initialized", true);
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return new MasterSecret(new SecretKeySpec(encryptionSecret, "AES"),
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new SecretKeySpec(macSecret, "HmacSHA1"));
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} catch (GeneralSecurityException e) {
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Log.w("keyutil", e);
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return null;
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}
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}
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public static boolean hasAsymmericMasterSecret(Context context) {
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SharedPreferences settings = context.getSharedPreferences(PREFERENCES_NAME, 0);
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return settings.contains(ASYMMETRIC_LOCAL_PUBLIC_DJB);
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}
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public static boolean isPassphraseInitialized(Context context) {
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SharedPreferences preferences = context.getSharedPreferences(PREFERENCES_NAME, 0);
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return preferences.getBoolean("passphrase_initialized", false);
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}
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private static void save(Context context, String key, int value) {
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if (!context.getSharedPreferences(PREFERENCES_NAME, 0)
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.edit()
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.putInt(key, value)
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.commit())
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{
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throw new AssertionError("failed to save a shared pref in MasterSecretUtil");
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}
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}
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private static void save(Context context, String key, byte[] value) {
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if (!context.getSharedPreferences(PREFERENCES_NAME, 0)
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.edit()
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.putString(key, Base64.encodeBytes(value))
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.commit())
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{
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throw new AssertionError("failed to save a shared pref in MasterSecretUtil");
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}
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}
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private static void save(Context context, String key, boolean value) {
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if (!context.getSharedPreferences(PREFERENCES_NAME, 0)
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.edit()
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.putBoolean(key, value)
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.commit())
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{
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throw new AssertionError("failed to save a shared pref in MasterSecretUtil");
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}
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}
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private static byte[] retrieve(Context context, String key) throws IOException {
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SharedPreferences settings = context.getSharedPreferences(PREFERENCES_NAME, 0);
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String encodedValue = settings.getString(key, "");
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if (TextUtils.isEmpty(encodedValue)) return null;
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else return Base64.decode(encodedValue);
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}
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private static int retrieve(Context context, String key, int defaultValue) throws IOException {
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SharedPreferences settings = context.getSharedPreferences(PREFERENCES_NAME, 0);
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return settings.getInt(key, defaultValue);
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}
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private static byte[] generateEncryptionSecret() {
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try {
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KeyGenerator generator = KeyGenerator.getInstance("AES");
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generator.init(128);
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SecretKey key = generator.generateKey();
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return key.getEncoded();
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} catch (NoSuchAlgorithmException ex) {
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Log.w("keyutil", ex);
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return null;
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}
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}
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private static byte[] generateMacSecret() {
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try {
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KeyGenerator generator = KeyGenerator.getInstance("HmacSHA1");
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return generator.generateKey().getEncoded();
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} catch (NoSuchAlgorithmException e) {
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Log.w("keyutil", e);
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return null;
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}
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}
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private static byte[] generateSalt() throws NoSuchAlgorithmException {
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SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
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byte[] salt = new byte[16];
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random.nextBytes(salt);
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return salt;
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}
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private static int generateIterationCount(String passphrase, byte[] salt) {
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int TARGET_ITERATION_TIME = 50; //ms
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int MINIMUM_ITERATION_COUNT = 100; //default for low-end devices
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int BENCHMARK_ITERATION_COUNT = 10000; //baseline starting iteration count
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try {
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PBEKeySpec keyspec = new PBEKeySpec(passphrase.toCharArray(), salt, BENCHMARK_ITERATION_COUNT);
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SecretKeyFactory skf = SecretKeyFactory.getInstance("PBEWITHSHA1AND128BITAES-CBC-BC");
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long startTime = System.currentTimeMillis();
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skf.generateSecret(keyspec);
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long finishTime = System.currentTimeMillis();
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int scaledIterationTarget = (int) (((double)BENCHMARK_ITERATION_COUNT / (double)(finishTime - startTime)) * TARGET_ITERATION_TIME);
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if (scaledIterationTarget < MINIMUM_ITERATION_COUNT) return MINIMUM_ITERATION_COUNT;
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else return scaledIterationTarget;
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} catch (NoSuchAlgorithmException e) {
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Log.w("MasterSecretUtil", e);
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return MINIMUM_ITERATION_COUNT;
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} catch (InvalidKeySpecException e) {
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Log.w("MasterSecretUtil", e);
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return MINIMUM_ITERATION_COUNT;
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}
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}
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private static SecretKey getKeyFromPassphrase(String passphrase, byte[] salt, int iterations)
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throws GeneralSecurityException
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{
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PBEKeySpec keyspec = new PBEKeySpec(passphrase.toCharArray(), salt, iterations);
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SecretKeyFactory skf = SecretKeyFactory.getInstance("PBEWITHSHA1AND128BITAES-CBC-BC");
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return skf.generateSecret(keyspec);
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}
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private static Cipher getCipherFromPassphrase(String passphrase, byte[] salt, int iterations, int opMode)
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throws GeneralSecurityException
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{
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SecretKey key = getKeyFromPassphrase(passphrase, salt, iterations);
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Cipher cipher = Cipher.getInstance(key.getAlgorithm());
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cipher.init(opMode, key, new PBEParameterSpec(salt, iterations));
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return cipher;
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}
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private static byte[] encryptWithPassphrase(byte[] encryptionSalt, int iterations, byte[] data, String passphrase)
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throws GeneralSecurityException
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{
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Cipher cipher = getCipherFromPassphrase(passphrase, encryptionSalt, iterations, Cipher.ENCRYPT_MODE);
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return cipher.doFinal(data);
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}
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private static byte[] decryptWithPassphrase(byte[] encryptionSalt, int iterations, byte[] data, String passphrase)
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throws GeneralSecurityException, IOException
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{
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Cipher cipher = getCipherFromPassphrase(passphrase, encryptionSalt, iterations, Cipher.DECRYPT_MODE);
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return cipher.doFinal(data);
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}
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private static Mac getMacForPassphrase(String passphrase, byte[] salt, int iterations)
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throws GeneralSecurityException
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{
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SecretKey key = getKeyFromPassphrase(passphrase, salt, iterations);
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byte[] pbkdf2 = key.getEncoded();
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SecretKeySpec hmacKey = new SecretKeySpec(pbkdf2, "HmacSHA1");
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Mac hmac = Mac.getInstance("HmacSHA1");
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hmac.init(hmacKey);
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return hmac;
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}
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private static byte[] verifyMac(byte[] macSalt, int iterations, byte[] encryptedAndMacdData, String passphrase) throws InvalidPassphraseException, GeneralSecurityException, IOException {
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Mac hmac = getMacForPassphrase(passphrase, macSalt, iterations);
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byte[] encryptedData = new byte[encryptedAndMacdData.length - hmac.getMacLength()];
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System.arraycopy(encryptedAndMacdData, 0, encryptedData, 0, encryptedData.length);
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byte[] givenMac = new byte[hmac.getMacLength()];
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System.arraycopy(encryptedAndMacdData, encryptedAndMacdData.length-hmac.getMacLength(), givenMac, 0, givenMac.length);
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byte[] localMac = hmac.doFinal(encryptedData);
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if (Arrays.equals(givenMac, localMac)) return encryptedData;
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else throw new InvalidPassphraseException("MAC Error");
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}
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private static byte[] macWithPassphrase(byte[] macSalt, int iterations, byte[] data, String passphrase) throws GeneralSecurityException {
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Mac hmac = getMacForPassphrase(passphrase, macSalt, iterations);
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byte[] mac = hmac.doFinal(data);
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byte[] result = new byte[data.length + mac.length];
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System.arraycopy(data, 0, result, 0, data.length);
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System.arraycopy(mac, 0, result, data.length, mac.length);
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return result;
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}
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}
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