org.sejda.sambox.encryption.Algorithm2B Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of sambox Show documentation

An Apache PDFBox fork intended to be used as PDF processor for Sejda and PDFsam related projects

There is a newer version: 3.0.21

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.sejda.sambox.encryption;

import static org.bouncycastle.util.Arrays.concatenate;
import static org.bouncycastle.util.Arrays.copyOf;
import static org.bouncycastle.util.Arrays.copyOfRange;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

/**
 * Algorithm 2B as defined in Chap 7.6.3.3.3 of PDF 32000-2
 * 
 * @author Andrea Vacondio
 *
 */
class Algorithm2B implements Algorithm2AHash
{

    private static final BigInteger THREE = new BigInteger("3");
    private static final Map HASHES = new HashMap<>();

    static
    {
        HASHES.put(0, MessageDigests.sha256());
        HASHES.put(1, MessageDigests.sha384());
        HASHES.put(2, MessageDigests.sha512());
    }

    private final AESEncryptionAlgorithmEngine aes128 = AESEngineNoPadding.cbc();
    private final byte[] u;

    Algorithm2B(byte[] u)
    {
        this.u = Optional.ofNullable(u).orElse(new byte[0]);
    }

    Algorithm2B()
    {
        this.u = new byte[0];
    }

    @Override
    public byte[] computeHash(byte[] input, byte[] password)
    {
        byte[] k = copyOf(HASHES.get(0).digest(input), 32);
        byte[] e = new byte[0];
        for (int round = 0; round < 64 || (e[e.length - 1] & 0xFF) > round - 32; round++)
        {
            byte[] k1Element = concatenate(password, k, u);
            byte[] k1 = new byte[0];
            for (int i = 0; i < 64; i++)
            {
                k1 = concatenate(k1, k1Element);
            }
            e = aes128.encryptBytes(k1, copyOf(k, 16), copyOfRange(k, 16, 32));
            k = HASHES.get(new BigInteger(1, copyOf(e, 16)).mod(THREE).intValue()).digest(e);
        }
        return copyOf(k, 32);
    }
}