001// Copyright 2012-2013 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.internal.util;
016
017import org.apache.commons.codec.binary.Base64;
018import org.apache.tapestry5.commons.util.ExceptionUtils;
019
020import javax.crypto.Mac;
021import java.io.IOException;
022import java.io.OutputStream;
023import java.security.Key;
024
025/**
026 * An output stream that wraps around a {@link Mac} (message authentication code algorithm).  This is currently
027 * used for symmetric (private) keys, but in theory could be used with assymetric (public/private) keys.
028 *
029 * @since 5.3.6
030 */
031public class MacOutputStream extends OutputStream
032{
033    private final Mac mac;
034
035    public static MacOutputStream streamFor(Key key) throws IOException
036    {
037        try
038        {
039            Mac mac = Mac.getInstance(key.getAlgorithm());
040            mac.init(key);
041
042            return new MacOutputStream(mac);
043        } catch (Exception ex)
044        {
045            throw new IOException("Unable to create MacOutputStream: " + ExceptionUtils.toMessage(ex), ex);
046        }
047    }
048
049    public MacOutputStream(Mac mac)
050    {
051        assert mac != null;
052
053        this.mac = mac;
054    }
055
056    /**
057     * Should only be invoked once, immediately after this stream is closed; it generates the final MAC result, and
058     * returns it as a Base64 encoded string.
059     *
060     * @return Base64 encoded MAC result
061     */
062    public String getResult()
063    {
064        byte[] result = mac.doFinal();
065
066        return new String(Base64.encodeBase64(result));
067    }
068
069    @Override
070    public void write(int b) throws IOException
071    {
072        mac.update((byte) b);
073    }
074
075    @Override
076    public void write(byte[] b) throws IOException
077    {
078        mac.update(b);
079    }
080
081    @Override
082    public void write(byte[] b, int off, int len) throws IOException
083    {
084        mac.update(b, off, len);
085    }
086}