Android Open Source - conceal Cipher Helper

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License

The source code is released under:

BSD License For Conceal software Copyright (c) 2014, Facebook, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that...

Java Source Code

package com.facebook.crypto;
/*  www . j  a  v a 2  s . c o  m*/
import com.facebook.crypto.cipher.NativeGCMCipher;
import com.facebook.crypto.cipher.NativeGCMCipherException;
import com.facebook.crypto.exception.CryptoInitializationException;
import com.facebook.crypto.exception.KeyChainException;
import com.facebook.crypto.keychain.KeyChain;
import com.facebook.crypto.streams.NativeGCMCipherInputStream;
import com.facebook.crypto.streams.NativeGCMCipherOutputStream;
import com.facebook.crypto.util.Assertions;
import com.facebook.crypto.util.NativeCryptoLibrary;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * A helper class with common functionality required for cipher operations in {@link Crypto}.
 */
/* package */ class CipherHelper {

  private final KeyChain mKeyChain;
  private final NativeCryptoLibrary mNativeCryptoLibrary;

  public CipherHelper(KeyChain keyChain, NativeCryptoLibrary nativeCryptoLibrary) {
    mKeyChain = keyChain;
    mNativeCryptoLibrary = nativeCryptoLibrary;
  }

  public OutputStream getCipherOutputStream(OutputStream cipherStream, Entity entity)
    throws KeyChainException, CryptoInitializationException, IOException {

    cipherStream.write(VersionCodes.CIPHER_SERALIZATION_VERSION);
    cipherStream.write(VersionCodes.CIPHER_ID);

    byte[] iv = mKeyChain.getNewIV();
    NativeGCMCipher gcmCipher = new NativeGCMCipher(mNativeCryptoLibrary);
    gcmCipher.encryptInit(mKeyChain.getCipherKey(), iv);
    cipherStream.write(iv);

    byte[] entityBytes = entity.getBytes();
    computeCipherAad(gcmCipher, VersionCodes.CIPHER_SERALIZATION_VERSION, VersionCodes.CIPHER_ID, entityBytes);
    return new NativeGCMCipherOutputStream(cipherStream, gcmCipher);
  }

  /**
   * Returns a cipher stream for the crypto version and id.
   */
  public InputStream getCipherInputStream(InputStream cipherStream, Entity entity, byte cryptoVersion, byte cipherID)
    throws IOException, KeyChainException, CryptoInitializationException {

    Assertions.checkArgumentForIO(cryptoVersion == VersionCodes.CIPHER_SERALIZATION_VERSION,
      "Unexpected crypto version " + cryptoVersion);

    Assertions.checkArgumentForIO(cipherID == VersionCodes.CIPHER_ID,
      "Unexpected cipher ID " + cipherID);

    byte[] iv = new byte[NativeGCMCipher.IV_LENGTH];
    int read = cipherStream.read(iv);
    if (read != iv.length) {
      throw new IOException("Not enough bytes for iv: " + read);
    }

    NativeGCMCipher gcmCipher = new NativeGCMCipher(mNativeCryptoLibrary);
    gcmCipher.decryptInit(mKeyChain.getCipherKey(), iv);

    byte[] entityBytes = entity.getBytes();
    computeCipherAad(gcmCipher, cryptoVersion, cipherID, entityBytes);
    return new NativeGCMCipherInputStream(cipherStream, gcmCipher);
  }

  /**
   * Gets the length of the meta data for the version of the API being decrypted.
   * This should preserve the following invariant:
   * </p>
   * Ciphertext data size = Plaintext data + Cipher meta data.
   */
  public int getCipherMetaDataLength() {
    return 2 + NativeGCMCipher.IV_LENGTH + NativeGCMCipher.TAG_LENGTH;
  }

  /**
   * Computes the Aad data for the cipher.
   */
  public void computeCipherAad(NativeGCMCipher gcmCipher, byte cryptoVersion, byte cipherID, byte[] entityBytes)
    throws NativeGCMCipherException {
    byte[] cryptoVersionBytes = { cryptoVersion };
    byte[] cipherIDBytes = { cipherID };
    gcmCipher.updateAad(cryptoVersionBytes, 1);
    gcmCipher.updateAad(cipherIDBytes, 1);
    gcmCipher.updateAad(entityBytes, entityBytes.length);
  }
}

Java Source Code List

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