package org.apache.poi.poifs.crypt.binaryrc4;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import org.apache.poi.EncryptedDocumentException;
import org.apache.poi.poifs.crypt.*;
import org.apache.poi.poifs.filesystem.DirectoryNode;
import org.apache.poi.poifs.filesystem.DocumentInputStream;
import org.apache.poi.util.LittleEndian;
import org.apache.poi.util.StringUtil;
public class BinaryRC4Decryptor extends Decryptor implements Cloneable {
private long length = -1L;
private int chunkSize = 512;
private class BinaryRC4CipherInputStream extends ChunkedCipherInputStream {
@Override
protected Cipher initCipherForBlock(Cipher existing, int block)
throws GeneralSecurityException {
return BinaryRC4Decryptor.this.initCipherForBlock(existing, block);
}
public BinaryRC4CipherInputStream(DocumentInputStream stream, long size)
throws GeneralSecurityException {
super(stream, size, chunkSize);
}
public BinaryRC4CipherInputStream(InputStream stream, int size, int initialPos)
throws GeneralSecurityException {
super(stream, size, chunkSize, initialPos);
}
}
protected BinaryRC4Decryptor() {
}
@Override
public boolean verifyPassword(String password) {
EncryptionVerifier ver = getEncryptionInfo().getVerifier();
SecretKey skey = generateSecretKey(password, ver);
try {
Cipher cipher = initCipherForBlock(null, 0, getEncryptionInfo(), skey, Cipher.DECRYPT_MODE);
byte[] encryptedVerifier = ver.getEncryptedVerifier();
byte[] verifier = new byte[encryptedVerifier.length];
cipher.update(encryptedVerifier, 0, encryptedVerifier.length, verifier);
setVerifier(verifier);
byte[] encryptedVerifierHash = ver.getEncryptedVerifierHash();
byte[] verifierHash = cipher.doFinal(encryptedVerifierHash);
HashAlgorithm hashAlgo = ver.getHashAlgorithm();
MessageDigest hashAlg = CryptoFunctions.getMessageDigest(hashAlgo);
byte[] calcVerifierHash = hashAlg.digest(verifier);
if (Arrays.equals(calcVerifierHash, verifierHash)) {
setSecretKey(skey);
return true;
}
} catch (GeneralSecurityException e) {
throw new EncryptedDocumentException(e);
}
return false;
}
@Override
public Cipher initCipherForBlock(Cipher cipher, int block)
throws GeneralSecurityException {
return initCipherForBlock(cipher, block, getEncryptionInfo(), getSecretKey(), Cipher.DECRYPT_MODE);
}
protected static Cipher initCipherForBlock(Cipher cipher, int block,
EncryptionInfo encryptionInfo, SecretKey skey, int encryptMode)
throws GeneralSecurityException {
EncryptionVerifier ver = encryptionInfo.getVerifier();
HashAlgorithm hashAlgo = ver.getHashAlgorithm();
byte[] blockKey = new byte[4];
LittleEndian.putUInt(blockKey, 0, block);
byte[] encKey = CryptoFunctions.generateKey(skey.getEncoded(), hashAlgo, blockKey, 16);
SecretKey key = new SecretKeySpec(encKey, skey.getAlgorithm());
if (cipher == null) {
EncryptionHeader em = encryptionInfo.getHeader();
cipher = CryptoFunctions.getCipher(key, em.getCipherAlgorithm(), null, null, encryptMode);
} else {
cipher.init(encryptMode, key);
}
return cipher;
}
protected static SecretKey generateSecretKey(String password, EncryptionVerifier ver) {
if (password.length() > 255) {
password = password.substring(0, 255);
}
HashAlgorithm hashAlgo = ver.getHashAlgorithm();
MessageDigest hashAlg = CryptoFunctions.getMessageDigest(hashAlgo);
byte[] hash = hashAlg.digest(StringUtil.getToUnicodeLE(password));
byte[] salt = ver.getSalt();
hashAlg.reset();
for (int i = 0; i < 16; i++) {
hashAlg.update(hash, 0, 5);
hashAlg.update(salt);
}
hash = new byte[5];
System.arraycopy(hashAlg.digest(), 0, hash, 0, 5);
return new SecretKeySpec(hash, ver.getCipherAlgorithm().jceId);
}
@Override
@SuppressWarnings("resource")
public ChunkedCipherInputStream getDataStream(DirectoryNode dir) throws IOException,
GeneralSecurityException {
DocumentInputStream dis = dir.createDocumentInputStream(DEFAULT_POIFS_ENTRY);
length = dis.readLong();
return new BinaryRC4CipherInputStream(dis, length);
}
@Override
public InputStream getDataStream(InputStream stream, int size, int initialPos)
throws IOException, GeneralSecurityException {
return new BinaryRC4CipherInputStream(stream, size, initialPos);
}
@Override
public long getLength() {
if (length == -1L) {
throw new IllegalStateException("Decryptor.getDataStream() was not called");
}
return length;
}
@Override
public void setChunkSize(int chunkSize) {
this.chunkSize = chunkSize;
}
@Override
public BinaryRC4Decryptor clone() throws CloneNotSupportedException {
return (BinaryRC4Decryptor)super.clone();
}
}