ALPNOfferedClientHelloExplorer.java
/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* Licensed 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 io.undertow.server.protocol.http;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import javax.net.ssl.SSLException;
import io.undertow.UndertowMessages;
/**
* Parses the client handshake to retrieve ALPN and cipher info
*/
final class ALPNOfferedClientHelloExplorer {
// Private constructor prevents construction outside this class.
private ALPNOfferedClientHelloExplorer() {
}
/**
* The header size of TLS/SSL records.
* <p>
* The value of this constant is {@value}.
*/
private static final int RECORD_HEADER_SIZE = 0x05;
static boolean isIncompleteHeader(ByteBuffer source) {
return source.remaining() < RECORD_HEADER_SIZE;
}
/**
* Checks if a client handshake is offering ALPN, and if so it returns a list of all ciphers. If ALPN is not being
* offered then this will return null.
*/
static List<Integer> parseClientHello(ByteBuffer source)
throws SSLException {
ByteBuffer input = source.duplicate();
// Do we have a complete header?
if (isIncompleteHeader(input)) {
throw new BufferUnderflowException();
}
// Is it a handshake message?
byte firstByte = input.get();
byte secondByte = input.get();
byte thirdByte = input.get();
if ((firstByte & 0x80) != 0 && thirdByte == 0x01) {
// looks like a V2ClientHello, we ignore it.
return null;
} else if (firstByte == 22) { // 22: handshake record
if (secondByte == 3 && thirdByte >= 1 && thirdByte <= 3) {
return exploreTLSRecord(input,
firstByte, secondByte, thirdByte);
}
}
return null;
}
/*
* struct {
* uint8 major;
* uint8 minor;
* } ProtocolVersion;
*
* enum {
* change_cipher_spec(20), alert(21), handshake(22),
* application_data(23), (255)
* } ContentType;
*
* struct {
* ContentType type;
* ProtocolVersion version;
* uint16 length;
* opaque fragment[TLSPlaintext.length];
* } TLSPlaintext;
*/
private static List<Integer> exploreTLSRecord(
ByteBuffer input, byte firstByte, byte secondByte,
byte thirdByte) throws SSLException {
// Is it a handshake message?
if (firstByte != 22) { // 22: handshake record
throw UndertowMessages.MESSAGES.notHandshakeRecord();
}
// Is there enough data for a full record?
int recordLength = getInt16(input);
if (recordLength > input.remaining()) {
throw new BufferUnderflowException();
}
// We have already had enough source bytes.
try {
return exploreHandshake(input,
secondByte, thirdByte, recordLength);
} catch (BufferUnderflowException ignored) {
throw UndertowMessages.MESSAGES.invalidHandshakeRecord();
}
}
/*
* enum {
* hello_request(0), client_hello(1), server_hello(2),
* certificate(11), server_key_exchange (12),
* certificate_request(13), server_hello_done(14),
* certificate_verify(15), client_key_exchange(16),
* finished(20)
* (255)
* } HandshakeType;
*
* struct {
* HandshakeType msg_type;
* uint24 length;
* select (HandshakeType) {
* case hello_request: HelloRequest;
* case client_hello: ClientHello;
* case server_hello: ServerHello;
* case certificate: Certificate;
* case server_key_exchange: ServerKeyExchange;
* case certificate_request: CertificateRequest;
* case server_hello_done: ServerHelloDone;
* case certificate_verify: CertificateVerify;
* case client_key_exchange: ClientKeyExchange;
* case finished: Finished;
* } body;
* } Handshake;
*/
private static List<Integer> exploreHandshake(
ByteBuffer input, byte recordMajorVersion,
byte recordMinorVersion, int recordLength) throws SSLException {
// What is the handshake type?
byte handshakeType = input.get();
if (handshakeType != 0x01) { // 0x01: client_hello message
throw UndertowMessages.MESSAGES.expectedClientHello();
}
// What is the handshake body length?
int handshakeLength = getInt24(input);
// Theoretically, a single handshake message might span multiple
// records, but in practice this does not occur.
if (handshakeLength > recordLength - 4) { // 4: handshake header size
throw UndertowMessages.MESSAGES.multiRecordSSLHandshake();
}
input = input.duplicate();
input.limit(handshakeLength + input.position());
return exploreRecord(input);
}
/*
* struct {
* uint32 gmt_unix_time;
* opaque random_bytes[28];
* } Random;
*
* opaque SessionID<0..32>;
*
* uint8 CipherSuite[2];
*
* enum { null(0), (255) } CompressionMethod;
*
* struct {
* ProtocolVersion client_version;
* Random random;
* SessionID session_id;
* CipherSuite cipher_suites<2..2^16-2>;
* CompressionMethod compression_methods<1..2^8-1>;
* select (extensions_present) {
* case false:
* struct {};
* case true:
* Extension extensions<0..2^16-1>;
* };
* } ClientHello;
*/
private static List<Integer> exploreRecord(
ByteBuffer input) throws SSLException {
// client version
byte helloMajorVersion = input.get();
byte helloMinorVersion = input.get();
if (helloMajorVersion != 3 && helloMinorVersion != 3) {
//we only care about TLS 1.2
return null;
}
// ignore random
for (int i = 0; i < 32; ++i) {// 32: the length of Random
byte d = input.get();
}
// session id
processByteVector8(input);
// cipher_suites
int int16 = getInt16(input);
List<Integer> ciphers = new ArrayList<>();
for (int i = 0; i < int16; i += 2) {
ciphers.add(getInt16(input));
}
// compression methods
processByteVector8(input);
if (input.remaining() > 0) {
return exploreExtensions(input, ciphers);
}
return null;
}
/*
* struct {
* ExtensionType extension_type;
* opaque extension_data<0..2^16-1>;
* } Extension;
*
* enum {
* server_name(0), max_fragment_length(1),
* client_certificate_url(2), trusted_ca_keys(3),
* truncated_hmac(4), status_request(5), (65535)
* } ExtensionType;
*/
private static List<Integer> exploreExtensions(ByteBuffer input, List<Integer> ciphers)
throws SSLException {
int length = getInt16(input); // length of extensions
while (length > 0) {
int extType = getInt16(input); // extenson type
int extLen = getInt16(input); // length of extension data
if (extType == 16) { // 0x00: ty
return ciphers;
} else { // ignore other extensions
processByteVector(input, extLen);
}
length -= extLen + 4;
}
return null;
}
private static int getInt8(ByteBuffer input) {
return input.get();
}
private static int getInt16(ByteBuffer input) {
return (input.get() & 0xFF) << 8 | input.get() & 0xFF;
}
private static int getInt24(ByteBuffer input) {
return (input.get() & 0xFF) << 16 | (input.get() & 0xFF) << 8 |
input.get() & 0xFF;
}
private static void processByteVector8(ByteBuffer input) {
int int8 = getInt8(input);
processByteVector(input, int8);
}
private static void processByteVector(ByteBuffer input, int length) {
for (int i = 0; i < length; ++i) {
byte b = input.get();
}
}
}