/** * Copyright (C) 2011 Whisper Systems * Copyright (C) 2013 Open Whisper Systems * * 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 . */ package org.thoughtcrime.securesms.crypto; import android.content.Context; import android.content.SharedPreferences; import android.content.SharedPreferences.Editor; import android.util.Log; import org.spongycastle.asn1.ASN1Encoding; import org.spongycastle.asn1.ASN1Primitive; import org.spongycastle.asn1.ASN1Sequence; import org.spongycastle.asn1.DERInteger; import org.spongycastle.asn1.DERSequence; import org.spongycastle.crypto.signers.ECDSASigner; import org.whispersystems.textsecure.crypto.IdentityKey; import org.whispersystems.textsecure.crypto.IdentityKeyPair; import org.whispersystems.textsecure.crypto.InvalidKeyException; import org.whispersystems.textsecure.crypto.MasterCipher; import org.whispersystems.textsecure.crypto.MasterSecret; import org.whispersystems.textsecure.crypto.PublicKey; import org.whispersystems.textsecure.crypto.ecc.Curve; import org.whispersystems.textsecure.crypto.ecc.ECKeyPair; import org.whispersystems.textsecure.crypto.ecc.ECPrivateKey; import org.whispersystems.textsecure.crypto.ecc.NistECPrivateKey; import org.whispersystems.textsecure.crypto.ecc.NistECPublicKey; import org.whispersystems.textsecure.util.Base64; import org.whispersystems.textsecure.util.Conversions; import org.whispersystems.textsecure.util.Util; import java.io.IOException; import java.math.BigInteger; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; /** * Utility class for working with identity keys. * * @author Moxie Marlinspike */ public class IdentityKeyUtil { private static final String IDENTITY_PUBLIC_KEY_NIST_PREF = "pref_identity_public"; private static final String IDENTITY_PRIVATE_KEY_NIST_PREF = "pref_identity_private"; private static final String IDENTITY_PUBLIC_KEY_DJB_PREF = "pref_identity_public_curve25519"; private static final String IDENTITY_PRIVATE_KEY_DJB_PREF = "pref_identity_private_curve25519"; public static boolean hasIdentityKey(Context context, int type) { SharedPreferences preferences = context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0); if (type == Curve.DJB_TYPE) { return preferences.contains(IDENTITY_PUBLIC_KEY_DJB_PREF) && preferences.contains(IDENTITY_PRIVATE_KEY_DJB_PREF); } else if (type == Curve.NIST_TYPE) { return preferences.contains(IDENTITY_PUBLIC_KEY_NIST_PREF) && preferences.contains(IDENTITY_PRIVATE_KEY_NIST_PREF); } return false; } public static IdentityKey getIdentityKey(Context context, int type) { if (!hasIdentityKey(context, type)) return null; try { String key; if (type == Curve.DJB_TYPE) key = IDENTITY_PUBLIC_KEY_DJB_PREF; else if (type == Curve.NIST_TYPE) key = IDENTITY_PUBLIC_KEY_NIST_PREF; else return null; byte[] publicKeyBytes = Base64.decode(retrieve(context, key)); return new IdentityKey(publicKeyBytes, 0); } catch (IOException ioe) { Log.w("IdentityKeyUtil", ioe); return null; } catch (InvalidKeyException e) { Log.w("IdentityKeyUtil", e); return null; } } public static IdentityKeyPair getIdentityKeyPair(Context context, MasterSecret masterSecret, int type) { if (!hasIdentityKey(context, type)) return null; try { String key; if (type == Curve.DJB_TYPE) key = IDENTITY_PRIVATE_KEY_DJB_PREF; else if (type == Curve.NIST_TYPE) key = IDENTITY_PRIVATE_KEY_NIST_PREF; else return null; MasterCipher masterCipher = new MasterCipher(masterSecret); IdentityKey publicKey = getIdentityKey(context, type); ECPrivateKey privateKey = masterCipher.decryptKey(type, Base64.decode(retrieve(context, key))); return new IdentityKeyPair(publicKey, privateKey); } catch (IOException e) { throw new AssertionError(e); } catch (InvalidKeyException e) { throw new AssertionError(e); } } public static String getFingerprint(Context context, int type) { if (!hasIdentityKey(context, type)) return null; IdentityKey identityKey = getIdentityKey(context, type); if (identityKey == null) return null; else return identityKey.getFingerprint(); } public static void generateIdentityKeys(Context context, MasterSecret masterSecret) { ECKeyPair nistKeyPair = Curve.generateKeyPairForType(Curve.NIST_TYPE, false); ECKeyPair djbKeyPair = Curve.generateKeyPairForType(Curve.DJB_TYPE, false); MasterCipher masterCipher = new MasterCipher(masterSecret); IdentityKey nistIdentityKey = new IdentityKey(nistKeyPair.getPublicKey()); IdentityKey djbIdentityKey = new IdentityKey(djbKeyPair.getPublicKey()); byte[] nistPrivateKey = masterCipher.encryptKey(nistKeyPair.getPrivateKey()); byte[] djbPrivateKey = masterCipher.encryptKey(djbKeyPair.getPrivateKey()); save(context, IDENTITY_PUBLIC_KEY_NIST_PREF, Base64.encodeBytes(nistIdentityKey.serialize())); save(context, IDENTITY_PUBLIC_KEY_DJB_PREF, Base64.encodeBytes(djbIdentityKey.serialize())); save(context, IDENTITY_PRIVATE_KEY_NIST_PREF, Base64.encodeBytes(nistPrivateKey)); save(context, IDENTITY_PRIVATE_KEY_DJB_PREF, Base64.encodeBytes(djbPrivateKey)); } public static boolean hasCurve25519IdentityKeys(Context context) { return retrieve(context, IDENTITY_PUBLIC_KEY_DJB_PREF) != null && retrieve(context, IDENTITY_PRIVATE_KEY_DJB_PREF) != null; } public static void generateCurve25519IdentityKeys(Context context, MasterSecret masterSecret) { MasterCipher masterCipher = new MasterCipher(masterSecret); ECKeyPair djbKeyPair = Curve.generateKeyPairForType(Curve.DJB_TYPE, false); IdentityKey djbIdentityKey = new IdentityKey(djbKeyPair.getPublicKey()); byte[] djbPrivateKey = masterCipher.encryptKey(djbKeyPair.getPrivateKey()); save(context, IDENTITY_PUBLIC_KEY_DJB_PREF, Base64.encodeBytes(djbIdentityKey.serialize())); save(context, IDENTITY_PRIVATE_KEY_DJB_PREF, Base64.encodeBytes(djbPrivateKey)); } public static IdentityKey verifySignedKeyExchange(byte[] keyExchangeBytes) throws InvalidKeyException { try { byte[] messageBytes = new byte[1 + PublicKey.KEY_SIZE]; System.arraycopy(keyExchangeBytes, 0, messageBytes, 0, messageBytes.length); byte[] publicKeyBytes = new byte[IdentityKey.NIST_SIZE]; System.arraycopy(keyExchangeBytes, messageBytes.length, publicKeyBytes, 0, publicKeyBytes.length); int signatureLength = Conversions.byteArrayToShort(keyExchangeBytes, messageBytes.length + publicKeyBytes.length); byte[] signatureBytes = new byte[signatureLength]; System.arraycopy(keyExchangeBytes, messageBytes.length + publicKeyBytes.length + 2, signatureBytes, 0, signatureBytes.length); byte[] messageHash = getMessageHash(messageBytes, publicKeyBytes); IdentityKey identityKey = new IdentityKey(publicKeyBytes, 0); ECDSASigner verifier = new ECDSASigner(); if (identityKey.getPublicKey().getType() != Curve.NIST_TYPE) { throw new InvalidKeyException("Signing only support on P256 keys!"); } verifier.init(false, ((NistECPublicKey)identityKey.getPublicKey()).getParameters()); ASN1Sequence sequence = (ASN1Sequence) ASN1Primitive.fromByteArray(signatureBytes); BigInteger[] signatureIntegers = new BigInteger[]{ ((DERInteger)sequence.getObjectAt(0)).getValue(), ((DERInteger)sequence.getObjectAt(1)).getValue() }; if (!verifier.verifySignature(messageHash, signatureIntegers[0], signatureIntegers[1])) throw new InvalidKeyException("Invalid signature!"); else return identityKey; } catch (IOException ioe) { throw new InvalidKeyException(ioe); } } public static byte[] getSignedKeyExchange(Context context, MasterSecret masterSecret, byte[] keyExchangeBytes) { try { MasterCipher masterCipher = new MasterCipher(masterSecret); byte[] publicKeyBytes = getIdentityKey(context, Curve.NIST_TYPE).serialize(); byte[] messageHash = getMessageHash(keyExchangeBytes, publicKeyBytes); byte[] privateKeyBytes = Base64.decode(retrieve(context, IDENTITY_PRIVATE_KEY_NIST_PREF)); ECPrivateKey privateKey = masterCipher.decryptKey(Curve.NIST_TYPE, privateKeyBytes); ECDSASigner signer = new ECDSASigner(); signer.init(true, ((NistECPrivateKey)privateKey).getParameters()); BigInteger[] messageSignatureInts = signer.generateSignature(messageHash); DERInteger[] derMessageSignatureInts = new DERInteger[]{ new DERInteger(messageSignatureInts[0]), new DERInteger(messageSignatureInts[1]) }; byte[] messageSignatureBytes = new DERSequence(derMessageSignatureInts).getEncoded(ASN1Encoding.DER); byte[] messageSignature = new byte[2 + messageSignatureBytes.length]; Conversions.shortToByteArray(messageSignature, 0, messageSignatureBytes.length); System.arraycopy(messageSignatureBytes, 0, messageSignature, 2, messageSignatureBytes.length); return Util.combine(keyExchangeBytes, publicKeyBytes, messageSignature); } catch (IOException ioe) { throw new AssertionError(ioe); } catch (InvalidKeyException e) { throw new AssertionError(e); } } private static byte[] getMessageHash(byte[] messageBytes, byte[] publicKeyBytes) { try { MessageDigest md = MessageDigest.getInstance("SHA1"); md.update(messageBytes); return md.digest(publicKeyBytes); } catch (NoSuchAlgorithmException nsae) { throw new AssertionError(nsae); } } public static String retrieve(Context context, String key) { SharedPreferences preferences = context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0); return preferences.getString(key, null); } public static void save(Context context, String key, String value) { SharedPreferences preferences = context.getSharedPreferences(MasterSecretUtil.PREFERENCES_NAME, 0); Editor preferencesEditor = preferences.edit(); preferencesEditor.putString(key, value); preferencesEditor.commit(); } }