com.healthmarketscience.jackcess.impl.office.RC4CryptoAPIProvider Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of jackcess-encrypt Show documentation
Show all versions of jackcess-encrypt Show documentation
An add-on to the Jackcess library for handling encryption in MS Access files.
/*
Copyright (c) 2013 James Ahlborn
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 com.healthmarketscience.jackcess.impl.office;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.EnumSet;
import java.util.Set;
import com.healthmarketscience.jackcess.impl.ByteUtil;
import com.healthmarketscience.jackcess.impl.PageChannel;
import org.bouncycastle.crypto.Digest;
import com.healthmarketscience.jackcess.util.StreamCipherCompat;
import com.healthmarketscience.jackcess.util.StreamCipherFactory;
import org.bouncycastle.crypto.digests.SHA1Digest;
import org.bouncycastle.crypto.params.KeyParameter;
/**
*
* @author James Ahlborn
*/
public class RC4CryptoAPIProvider extends StreamCipherProvider
{
private static final Set VALID_CRYPTO_ALGOS =
EnumSet.of(EncryptionHeader.CryptoAlgorithm.RC4);
private static final Set VALID_HASH_ALGOS =
EnumSet.of(EncryptionHeader.HashAlgorithm.SHA1);
private final EncryptionHeader _header;
private final EncryptionVerifier _verifier;
private final byte[] _baseHash;
private final int _encKeyByteSize;
public RC4CryptoAPIProvider(PageChannel channel, byte[] encodingKey,
ByteBuffer encProvBuf, byte[] pwdBytes)
{
super(channel, encodingKey);
_header = EncryptionHeader.read(encProvBuf, VALID_CRYPTO_ALGOS,
VALID_HASH_ALGOS);
_verifier = new EncryptionVerifier(encProvBuf, _header.getCryptoAlgorithm());
// OC: 2.3.5.2 (part 1)
_baseHash = hash(getDigest(), _verifier.getSalt(), pwdBytes);
_encKeyByteSize = bits2bytes(_header.getKeySize());
}
public boolean canEncodePartialPage() {
// RC4 ciphers are not influenced by the page contents, so we can easily
// encode part of the buffer.
return true;
}
@Override
protected Digest initDigest() {
return new SHA1Digest();
}
@Override
protected StreamCipherCompat initCipher() {
return StreamCipherFactory.newRC4Engine();
}
@Override
protected KeyParameter computeCipherParams(int pageNumber) {
// when actually decrypting pages, we incorporate the "encoding key"
return computeEncryptionKey(getEncodingKey(pageNumber));
}
private KeyParameter computeEncryptionKey(byte[] blockBytes) {
// OC: 2.3.5.2 (part 2)
byte[] encKey = hash(getDigest(), _baseHash, blockBytes, _encKeyByteSize);
if(_header.getKeySize() == 40) {
encKey = ByteUtil.copyOf(encKey, bits2bytes(128));
}
return new KeyParameter(encKey);
}
@Override
protected boolean verifyPassword(byte[] pwdBytes) {
StreamCipherCompat cipher = decryptInit(getStreamCipher(),
computeEncryptionKey(int2bytes(0)));
byte[] verifier = decryptBytes(cipher, _verifier.getEncryptedVerifier());
byte[] verifierHash =
fixToLength(decryptBytes(cipher, _verifier.getEncryptedVerifierHash()),
_verifier.getVerifierHashSize());
byte[] testHash = fixToLength(hash(getDigest(), verifier),
_verifier.getVerifierHashSize());
return Arrays.equals(verifierHash, testHash);
}
}
© 2015 - 2024 Weber Informatics LLC | Privacy Policy