HTpFnZsB

1public static DecryptedSessionKey decryptSessionKey(PrivateKey pk, EncryptedSessionKey encryptedSessionKey) throws KomandorException {
2    SecretKey key_ = null;
3    byte[] iv = null;
4    try {
5      int sizeLength = 4;
6      byte[] bKey = Base64.decode(encryptedSessionKey.getEncryptedKey(), Base64.NO_WRAP);
7      
8      byte[] bBlobLength = SystemUtils.reverseByteArray(Arrays.copyOfRange(bKey, 0, sizeLength));
9      int blobLength = ByteBuffer.wrap(bBlobLength).getInt();
10      
11      byte[] bSimpleBlob = Arrays.copyOfRange(bKey, sizeLength, sizeLength + blobLength);
12      byte[] bBlobHeader = Arrays.copyOfRange(bSimpleBlob, 0, 16);
13      byte[] sv = Arrays.copyOfRange(bSimpleBlob, 16, 24);
14      byte[] bEncryptedKey = Arrays.copyOfRange(bSimpleBlob, 24, 24 + 32);
15      byte[] bMacKey = Arrays.copyOfRange(bSimpleBlob, 56, 56 + 4);
16      byte[] bEncryptedParams = Arrays.copyOfRange(bSimpleBlob, 60, blobLength);
17      
18      // Получаем IV вектор
19      int IVStart = sizeLength + blobLength;
20      byte[] bIVLength = SystemUtils.reverseByteArray(Arrays.copyOfRange(bKey, IVStart, IVStart + sizeLength));
21      int IVLength = ByteBuffer.wrap(bIVLength).getInt();
22      iv = Arrays.copyOfRange(bKey, IVStart + sizeLength, IVStart + sizeLength + IVLength);
23      
24      // Получаем зашифрованный ключ
25      final Gost28147_89_EncryptedKey ek = new Gost28147_89_EncryptedKey();
26      ek.encryptedKey = new Gost28147_89_Key(bEncryptedKey);
27      ek.macKey = new Gost28147_89_MAC(bMacKey);
28      final Asn1BerEncodeBuffer ebuf = new Asn1BerEncodeBuffer();
29      ek.encode(ebuf);
30      final byte[] wrap = ebuf.getMsgCopy();
31      
32      // Генерируем ключ согласования
33      SecretKey responderAgree = generateKeyAgreement(pk, encryptedSessionKey.getCertificate(), sv);
34      
35      if (responderAgree == null) {
36        throw new KomandorException("Key agreement is null");
37      }
38      
39      // Расшифровываем ключ
40      Cipher cipher = Cipher.getInstance(CIPHER_ALG + CIPHER_KEY_ALG_PARAMS);
41      cipher.init(Cipher.UNWRAP_MODE, responderAgree);
42      key_ = (SecretKey) cipher.unwrap(wrap, null, Cipher.SECRET_KEY);
43    } catch (Exception e) {
44      throw new KomandorException(e);
45    }
46    return new DecryptedSessionKey(key_, iv);
47  }
48
49private static SecretKey generateKeyAgreement(PrivateKey pk, X509Certificate partnerCert, byte[] sv) throws NoSuchProviderException, NoSuchAlgorithmException, InvalidAlgorithmParameterException, InvalidKeyException {
50    final IvParameterSpec ivspec = new IvParameterSpec(sv);
51    final KeyAgreement keyAgree = KeyAgreement.getInstance(pk.getAlgorithm(), JCSP.PROVIDER_NAME);
52    keyAgree.init(pk, ivspec, null);
53    keyAgree.doPhase(partnerCert.getPublicKey(), true);
54    return keyAgree.generateSecret(CIPHER_ALG);
55  }