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/**
* Copyright (C) 2011 Whisper Systems
* Copyright (C) 2013 Open Whisper Systems
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*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.thoughtcrime.securesms.crypto;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.support.annotation.NonNull;
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import org.thoughtcrime.securesms.util.Base64;
import org.whispersystems.libsignal.IdentityKey;
import org.whispersystems.libsignal.IdentityKeyPair;
import org.whispersystems.libsignal.InvalidKeyException;
import org.whispersystems.libsignal.ecc.Curve;
import org.whispersystems.libsignal.ecc.ECKeyPair;
import org.whispersystems.libsignal.ecc.ECPrivateKey;
import java.io.IOException;
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/**
* Utility class for working with identity keys.
*
* @author Moxie Marlinspike
*/
public class IdentityKeyUtil {
private static final String TAG = IdentityKeyUtil.class.getSimpleName();
private static final String IDENTITY_PUBLIC_KEY_CIPHERTEXT_LEGACY_PREF = "pref_identity_public_curve25519";
private static final String IDENTITY_PRIVATE_KEY_CIPHERTEXT_LEGACY_PREF = "pref_identity_private_curve25519";
private static final String IDENTITY_PUBLIC_KEY_PREF = "pref_identity_public_v3";
private static final String IDENTITY_PRIVATE_KEY_PREF = "pref_identity_private_v3";
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public static boolean hasIdentityKey(Context context) {
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SharedPreferences preferences = context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0);
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return
preferences.contains(IDENTITY_PUBLIC_KEY_PREF) &&
preferences.contains(IDENTITY_PRIVATE_KEY_PREF);
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}
public static @NonNull IdentityKey getIdentityKey(@NonNull Context context) {
if (!hasIdentityKey(context)) throw new AssertionError("There isn't one!");
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try {
byte[] publicKeyBytes = Base64.decode(retrieve(context, IDENTITY_PUBLIC_KEY_PREF));
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return new IdentityKey(publicKeyBytes, 0);
} catch (IOException | InvalidKeyException e) {
throw new AssertionError(e);
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}
}
public static @NonNull IdentityKeyPair getIdentityKeyPair(@NonNull Context context) {
if (!hasIdentityKey(context)) throw new AssertionError("There isn't one!");
try {
IdentityKey publicKey = getIdentityKey(context);
ECPrivateKey privateKey = Curve.decodePrivatePoint(Base64.decode(retrieve(context, IDENTITY_PRIVATE_KEY_PREF)));
return new IdentityKeyPair(publicKey, privateKey);
} catch (IOException e) {
throw new AssertionError(e);
}
}
public static void generateIdentityKeys(Context context) {
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ECKeyPair djbKeyPair = Curve.generateKeyPair();
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IdentityKey djbIdentityKey = new IdentityKey(djbKeyPair.getPublicKey());
ECPrivateKey djbPrivateKey = djbKeyPair.getPrivateKey();
save(context, IDENTITY_PUBLIC_KEY_PREF, Base64.encodeBytes(djbIdentityKey.serialize()));
save(context, IDENTITY_PRIVATE_KEY_PREF, Base64.encodeBytes(djbPrivateKey.serialize()));
}
public static void migrateIdentityKeys(@NonNull Context context,
@NonNull MasterSecret masterSecret)
{
if (!hasIdentityKey(context)) {
if (hasLegacyIdentityKeys(context)) {
IdentityKeyPair legacyPair = getLegacyIdentityKeyPair(context, masterSecret);
save(context, IDENTITY_PUBLIC_KEY_PREF, Base64.encodeBytes(legacyPair.getPublicKey().serialize()));
save(context, IDENTITY_PRIVATE_KEY_PREF, Base64.encodeBytes(legacyPair.getPrivateKey().serialize()));
delete(context, IDENTITY_PUBLIC_KEY_CIPHERTEXT_LEGACY_PREF);
delete(context, IDENTITY_PRIVATE_KEY_CIPHERTEXT_LEGACY_PREF);
} else {
generateIdentityKeys(context);
}
}
}
private static boolean hasLegacyIdentityKeys(Context context) {
return
retrieve(context, IDENTITY_PUBLIC_KEY_CIPHERTEXT_LEGACY_PREF) != null &&
retrieve(context, IDENTITY_PRIVATE_KEY_CIPHERTEXT_LEGACY_PREF) != null;
}
private static IdentityKeyPair getLegacyIdentityKeyPair(@NonNull Context context,
@NonNull MasterSecret masterSecret)
{
try {
MasterCipher masterCipher = new MasterCipher(masterSecret);
byte[] publicKeyBytes = Base64.decode(retrieve(context, IDENTITY_PUBLIC_KEY_CIPHERTEXT_LEGACY_PREF));
IdentityKey identityKey = new IdentityKey(publicKeyBytes, 0);
ECPrivateKey privateKey = masterCipher.decryptKey(Base64.decode(retrieve(context, IDENTITY_PRIVATE_KEY_CIPHERTEXT_LEGACY_PREF)));
return new IdentityKeyPair(identityKey, privateKey);
} catch (IOException | InvalidKeyException e) {
throw new AssertionError(e);
}
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}
private static String retrieve(Context context, String key) {
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SharedPreferences preferences = context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0);
return preferences.getString(key, null);
}
private static void save(Context context, String key, String value) {
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SharedPreferences preferences = context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0);
Editor preferencesEditor = preferences.edit();
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preferencesEditor.putString(key, value);
if (!preferencesEditor.commit()) throw new AssertionError("failed to save identity key/value to shared preferences");
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}
private static void delete(Context context, String key) {
context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0).edit().remove(key).commit();
}
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}