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/* ====================================================================
   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.apache.poi.poifs.crypt.standard;

import java.io.IOException;

import org.apache.poi.EncryptedDocumentException;
import org.apache.poi.poifs.crypt.ChainingMode;
import org.apache.poi.poifs.crypt.CipherAlgorithm;
import org.apache.poi.poifs.crypt.EncryptionInfo;
import org.apache.poi.poifs.crypt.EncryptionInfoBuilder;
import org.apache.poi.poifs.crypt.HashAlgorithm;
import org.apache.poi.util.LittleEndianInput;

public class StandardEncryptionInfoBuilder implements EncryptionInfoBuilder {

    /**
     * initialize the builder from a stream
     */
    @Override
    public void initialize(EncryptionInfo info, LittleEndianInput dis) throws IOException {
        /* int hSize = */ dis.readInt();
        StandardEncryptionHeader header = new StandardEncryptionHeader(dis);
        info.setHeader(header);
        info.setVerifier(new StandardEncryptionVerifier(dis, header));

        if (info.getVersionMinor() == 2 && (info.getVersionMajor() == 3 || info.getVersionMajor() == 4)) {
            StandardDecryptor dec = new StandardDecryptor();
            dec.setEncryptionInfo(info);
            info.setDecryptor(dec);
        }
    }
    
    /**
     * initialize the builder from scratch
     */
    @Override
    public void initialize(EncryptionInfo info, CipherAlgorithm cipherAlgorithm, HashAlgorithm hashAlgorithm, int keyBits, int blockSize, ChainingMode chainingMode) {
        if (cipherAlgorithm == null) {
            cipherAlgorithm = CipherAlgorithm.aes128;
        }
        if (cipherAlgorithm != CipherAlgorithm.aes128 &&
            cipherAlgorithm != CipherAlgorithm.aes192 &&
            cipherAlgorithm != CipherAlgorithm.aes256) {
            throw new EncryptedDocumentException("Standard encryption only supports AES128/192/256.");
        }
        
        if (hashAlgorithm == null) {
            hashAlgorithm = HashAlgorithm.sha1;
        }
        if (hashAlgorithm != HashAlgorithm.sha1) {
            throw new EncryptedDocumentException("Standard encryption only supports SHA-1.");
        }
        if (chainingMode == null) {
            chainingMode = ChainingMode.ecb;
        }
        if (chainingMode != ChainingMode.ecb) {
            throw new EncryptedDocumentException("Standard encryption only supports ECB chaining.");
        }
        if (keyBits == -1) {
            keyBits = cipherAlgorithm.defaultKeySize;
        }
        if (blockSize == -1) {
            blockSize = cipherAlgorithm.blockSize;
        }
        boolean found = false;
        for (int ks : cipherAlgorithm.allowedKeySize) {
            found |= (ks == keyBits);
        }
        if (!found) {
            throw new EncryptedDocumentException("KeySize "+keyBits+" not allowed for Cipher "+cipherAlgorithm.toString());
        }
        info.setHeader(new StandardEncryptionHeader(cipherAlgorithm, hashAlgorithm, keyBits, blockSize, chainingMode));
        info.setVerifier(new StandardEncryptionVerifier(cipherAlgorithm, hashAlgorithm, keyBits, blockSize, chainingMode));
        StandardDecryptor dec = new StandardDecryptor();
        dec.setEncryptionInfo(info);
        info.setDecryptor(dec);
        StandardEncryptor enc = new StandardEncryptor();
        enc.setEncryptionInfo(info);
        info.setEncryptor(enc);
    }
}