/* * Copyright (C) 2010 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package net.robotmedia.billing.utils; import javax.crypto.*; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.PBEKeySpec; import javax.crypto.spec.SecretKeySpec; import java.io.UnsupportedEncodingException; import java.security.GeneralSecurityException; import java.security.spec.KeySpec; /** * An obfuscator that uses AES to encrypt data. */ public class AESObfuscator { private static final String UTF8 = "UTF-8"; private static final String KEYGEN_ALGORITHM = "PBEWITHSHAAND256BITAES-CBC-BC"; private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding"; private static final byte[] IV = {16, 74, 71, -80, 32, 101, -47, 72, 117, -14, 0, -29, 70, 65, -12, 74}; private static final String header = "net.robotmedia.billing.utils.AESObfuscator-1|"; private Cipher mEncryptor; private Cipher mDecryptor; public AESObfuscator(byte[] salt, String password) { try { SecretKeyFactory factory = SecretKeyFactory.getInstance(KEYGEN_ALGORITHM); KeySpec keySpec = new PBEKeySpec(password.toCharArray(), salt, 1024, 256); SecretKey tmp = factory.generateSecret(keySpec); SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES"); mEncryptor = Cipher.getInstance(CIPHER_ALGORITHM); mEncryptor.init(Cipher.ENCRYPT_MODE, secret, new IvParameterSpec(IV)); mDecryptor = Cipher.getInstance(CIPHER_ALGORITHM); mDecryptor.init(Cipher.DECRYPT_MODE, secret, new IvParameterSpec(IV)); } catch (GeneralSecurityException e) { // This can't happen on a compatible Android device. throw new RuntimeException("Invalid environment", e); } } public String obfuscate(String original) { if (original == null) { return null; } try { // Header is appended as an integrity check return Base64.encode(mEncryptor.doFinal((header + original).getBytes(UTF8))); } catch (UnsupportedEncodingException e) { throw new RuntimeException("Invalid environment", e); } catch (GeneralSecurityException e) { throw new RuntimeException("Invalid environment", e); } } public String unobfuscate(String obfuscated) throws ValidationException { if (obfuscated == null) { return null; } try { String result = new String(mDecryptor.doFinal(Base64.decode(obfuscated)), UTF8); // Check for presence of header. This serves as a final integrity check, for cases // where the block size is correct during decryption. int headerIndex = result.indexOf(header); if (headerIndex != 0) { throw new ValidationException("Header not found (invalid data or key)" + ":" + obfuscated); } return result.substring(header.length(), result.length()); } catch (Base64DecoderException e) { throw new ValidationException(e.getMessage() + ":" + obfuscated); } catch (IllegalBlockSizeException e) { throw new ValidationException(e.getMessage() + ":" + obfuscated); } catch (BadPaddingException e) { throw new ValidationException(e.getMessage() + ":" + obfuscated); } catch (UnsupportedEncodingException e) { throw new RuntimeException("Invalid environment", e); } } public class ValidationException extends Exception { public ValidationException() { super(); } public ValidationException(String s) { super(s); } private static final long serialVersionUID = 1L; } }