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/*
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* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.security.ssl;
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import java.io.IOException;
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import javax.net.ssl.SSLProtocolException;
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/*
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* [RFC6066] TLS specifies a fixed maximum plaintext fragment length of
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* 2^14 bytes. It may be desirable for constrained clients to negotiate
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* a smaller maximum fragment length due to memory limitations or bandwidth
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* limitations.
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*
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* In order to negotiate smaller maximum fragment lengths, clients MAY
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* include an extension of type "max_fragment_length" in the (extended)
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* client hello. The "extension_data" field of this extension SHALL
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* contain:
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*
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* enum{
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* 2^9(1), 2^10(2), 2^11(3), 2^12(4), (255)
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* } MaxFragmentLength;
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*
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* whose value is the desired maximum fragment length.
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*/
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final class MaxFragmentLengthExtension extends HelloExtension {
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private static final int MAX_FRAGMENT_LENGTH_512 = 1; // 2^9
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private static final int MAX_FRAGMENT_LENGTH_1024 = 2; // 2^10
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private static final int MAX_FRAGMENT_LENGTH_2048 = 3; // 2^11
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private static final int MAX_FRAGMENT_LENGTH_4096 = 4; // 2^12
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final int maxFragmentLength;
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MaxFragmentLengthExtension(int fragmentSize) {
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super(ExtensionType.EXT_MAX_FRAGMENT_LENGTH);
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if (fragmentSize < 1024) {
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maxFragmentLength = MAX_FRAGMENT_LENGTH_512;
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} else if (fragmentSize < 2048) {
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maxFragmentLength = MAX_FRAGMENT_LENGTH_1024;
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} else if (fragmentSize < 4096) {
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maxFragmentLength = MAX_FRAGMENT_LENGTH_2048;
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} else {
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maxFragmentLength = MAX_FRAGMENT_LENGTH_4096;
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}
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}
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MaxFragmentLengthExtension(HandshakeInStream s, int len)
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throws IOException {
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super(ExtensionType.EXT_MAX_FRAGMENT_LENGTH);
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// check the extension length
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if (len != 1) {
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throw new SSLProtocolException("Invalid " + type + " extension");
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}
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maxFragmentLength = s.getInt8();
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if ((maxFragmentLength > 4) || (maxFragmentLength < 1)) {
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throw new SSLProtocolException("Invalid " + type + " extension");
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}
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}
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// Length of the encoded extension, including the type and length fields
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@Override
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int length() {
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return 5; // 4: extension type and length fields
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// 1: MaxFragmentLength field
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}
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@Override
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void send(HandshakeOutStream s) throws IOException {
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s.putInt16(type.id);
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s.putInt16(1);
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s.putInt8(maxFragmentLength);
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}
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int getMaxFragLen() {
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switch (maxFragmentLength) {
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case MAX_FRAGMENT_LENGTH_512:
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return 512;
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case MAX_FRAGMENT_LENGTH_1024:
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return 1024;
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case MAX_FRAGMENT_LENGTH_2048:
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return 2048;
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case MAX_FRAGMENT_LENGTH_4096:
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return 4096;
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}
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// unlikely to happen
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return -1;
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}
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static boolean needFragLenNego(int fragmentSize) {
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return (fragmentSize > 0) && (fragmentSize <= 4096);
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}
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static int getValidMaxFragLen(int fragmentSize) {
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if (fragmentSize < 1024) {
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return 512;
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} else if (fragmentSize < 2048) {
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return 1024;
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} else if (fragmentSize < 4096) {
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return 2048;
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} else if (fragmentSize == 4096) {
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return 4096;
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} else {
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return 16384;
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}
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}
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@Override
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public String toString() {
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return "Extension " + type + ", max_fragment_length: " +
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"(2^" + (maxFragmentLength + 8) + ")";
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}
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}
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