001/**
002 *
003 * Copyright 2013 Florian Schmaus
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.jivesoftware.smack.compression;
018
019import java.io.IOException;
020import java.io.InputStream;
021import java.io.OutputStream;
022
023public abstract class XMPPInputOutputStream {
024
025    protected static FlushMethod flushMethod;
026
027    /**
028     * Set the used flushed method when compressing data. The default is full flush which may not
029     * achieve the best compression ratio, but provides better security against certain attacks.
030     * Only use sync flush if you fully understand the implications.
031     * 
032     * @see <a href="https://blog.thijsalkema.de/blog/2014/08/07/https-attacks-and-xmpp-2-crime-and-breach/">Attacks against XMPP when using compression</a>
033     * @param flushMethod
034     */
035    public static void setFlushMethod(FlushMethod flushMethod) {
036        XMPPInputOutputStream.flushMethod = flushMethod;
037    }
038
039    protected final String compressionMethod;
040
041    protected XMPPInputOutputStream(String compressionMethod) {
042        this.compressionMethod = compressionMethod;
043    }
044
045    public String getCompressionMethod() {
046        return compressionMethod;
047    }
048
049    public abstract boolean isSupported();
050
051    public abstract InputStream getInputStream(InputStream inputStream) throws IOException;
052
053    public abstract OutputStream getOutputStream(OutputStream outputStream) throws IOException;
054
055    public enum FlushMethod {
056        FULL_FLUSH,
057        SYNC_FLUSH,
058    }
059}