为什么要使用SSLEngine, 参考javadoc的说明:
SSLSocket 类提供很多相同的安全功能，但是所有的入站和出站数据都是使用底层 Socket 自动地传输，底层 Socket 设计为使用阻塞模型。虽然这适合于很多应用程序，但是此模型却不提供大型服务器所需的可伸缩性。
SSLEngine 的主要特征是它在入站和出站的字节流上操作，与传输机制无关。安排到同位体可靠的 I/O 传输是 SSLEngine 用户的职责。通过从 I/O 传输机制中分离出 SSL/TLS 抽象，SSLEngine 可以被用于各种 I/O 类型，例如 non-blocking I/O (polling)、selectable non-blocking I/O、 Socket 和传统的 Input/OutputStreams、本地的 ByteBuffers 或字节数组、未来的异步 I/O 模型等等。
怎么使用SSLEngine, 示例源代码位置:
http://www.cs.lafayette.edu/docs/java/guide/security/jsse/samples/
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/**
* A SSLEngine usage example which simplifies the presentation
* by removing the I/O and multi-threading concerns.
*
* The demo creates two SSLEngines, simulating a client and server.
* The "transport" layer consists two ByteBuffers: think of them
* as directly connected pipes.
*
* Note, this is a *very* simple example: real code will be much more
* involved. For example, different threading and I/O models could be
* used, transport mechanisms could close unexpectedly, and so on.
*
* When this application runs, notice that several messages
* (wrap/unwrap) pass before any application data is consumed or
* produced. (For more information, please see the SSL/TLS
* specifications.) There may several steps for a successful handshake,
* so it's typical to see the following series of operations:
*
* client server message
* ====== ====== =======
* wrap() ... ClientHello
* ... unwrap() ClientHello
* ... wrap() ServerHello/Certificate
* unwrap() ... ServerHello/Certificate
* wrap() ... ClientKeyExchange
* wrap() ... ChangeCipherSpec
* wrap() ... Finished
* ... unwrap() ClientKeyExchange
* ... unwrap() ChangeCipherSpec
* ... unwrap() Finished
* ... wrap() ChangeCipherSpec
* ... wrap() Finished
* unwrap() ... ChangeCipherSpec
* unwrap() ... Finished
*/
import javax.net.ssl.*;
import javax.net.ssl.SSLEngineResult.*;
import java.io.*;
import java.security.*;
import java.nio.*;
public class SSLEngineSimpleDemo {
/*
* Enables logging of the SSLEngine operations.
*/
private static boolean logging = true;
/*
* Enables the JSSE system debugging system property:
*
* -Djavax.net.debug=all
*
* This gives a lot of low-level information about operations underway,
* including specific handshake messages, and might be best examined after
* gaining some familiarity with this application.
*/
private static boolean debug = false;
private SSLContext sslc;
private SSLEngine clientEngine; // client Engine
private ByteBuffer clientOut; // write side of clientEngine
private ByteBuffer clientIn; // read side of clientEngine
private SSLEngine serverEngine; // server Engine
private ByteBuffer serverOut; // write side of serverEngine
private ByteBuffer serverIn; // read side of serverEngine
/*
* For data transport, this example uses local ByteBuffers. This isn't
* really useful, but the purpose of this example is to show SSLEngine
* concepts, not how to do network transport.
*/
private ByteBuffer cTOs; // "reliable" transport client->server
private ByteBuffer sTOc; // "reliable" transport server->client
/*
* The following is to set up the keystores.
*/
private static String keyStoreFile = "testkeys";
private static String trustStoreFile = "testkeys";
private static String passwd = "passphrase";
/*
* Main entry point for this demo.
*/
public static void main(String args[]) throws Exception {
if (debug) {
System.setProperty("javax.net.debug", "all");
}
SSLEngineSimpleDemo demo = new SSLEngineSimpleDemo();
demo.runDemo();
System.out.println("Demo Completed.");
}
/*
* Create an initialized SSLContext to use for this demo.
*/
public SSLEngineSimpleDemo() throws Exception {
KeyStore ks = KeyStore.getInstance("JKS");
KeyStore ts = KeyStore.getInstance("JKS");
char[] passphrase = "passphrase".toCharArray();
ks.load(new FileInputStream(keyStoreFile), passphrase);
ts.load(new FileInputStream(trustStoreFile), passphrase);
KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
kmf.init(ks, passphrase);
TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");
tmf.init(ts);
SSLContext sslCtx = SSLContext.getInstance("TLS");
sslCtx.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
sslc = sslCtx;
}
/*
* Run the demo.
*
* Sit in a tight loop, both engines calling wrap/unwrap regardless of
* whether data is available or not. We do this until both engines report
* back they are closed.
*
* The main loop handles all of the I/O phases of the SSLEngine's lifetime:
*
* initial handshaking application data transfer engine closing
*
* One could easily separate these phases into separate sections of code.
*/
private void runDemo() throws Exception {
boolean dataDone = false;
createSSLEngines();
createBuffers();
SSLEngineResult clientResult; // results from client's last operation
SSLEngineResult serverResult; // results from server's last operation
/*
* Examining the SSLEngineResults could be much more involved, and may
* alter the overall flow of the application.
*
* For example, if we received a BUFFER_OVERFLOW when trying to write to
* the output pipe, we could reallocate a larger pipe, but instead we
* wait for the peer to drain it.
*/
while (!isEngineClosed(clientEngine) || !isEngineClosed(serverEngine)) {
log("================");
clientResult = clientEngine.wrap(clientOut, cTOs);
log("client wrap: ", clientResult);
runDelegatedTasks(clientResult, clientEngine);
serverResult = serverEngine.wrap(serverOut, sTOc);
log("server wrap: ", serverResult);
runDelegatedTasks(serverResult, serverEngine);
cTOs.flip();
sTOc.flip();
log("----");
clientResult = clientEngine.unwrap(sTOc, clientIn);
log("client unwrap: ", clientResult);
runDelegatedTasks(clientResult, clientEngine);
serverResult = serverEngine.unwrap(cTOs, serverIn);
log("server unwrap: ", serverResult);
runDelegatedTasks(serverResult, serverEngine);
cTOs.compact();
sTOc.compact();
/*
* After we've transfered all application data between the client
* and server, we close the clientEngine's outbound stream. This
* generates a close_notify handshake message, which the server
* engine receives and responds by closing itself.
*
* In normal operation, each SSLEngine should call closeOutbound().
* To protect against truncation attacks, SSLEngine.closeInbound()
* should be called whenever it has determined that no more input
* data will ever be available (say a closed input stream).
*/
if (!dataDone && (clientOut.limit() == serverIn.position())
&& (serverOut.limit() == clientIn.position())) {
/*
* A sanity check to ensure we got what was sent.
*/
checkTransfer(serverOut, clientIn);
checkTransfer(clientOut, serverIn);
log("\tClosing clientEngine's *OUTBOUND*...");
clientEngine.closeOutbound();
// serverEngine.closeOutbound();
dataDone = true;
}
}
}
/*
* Using the SSLContext created during object creation, create/configure the
* SSLEngines we'll use for this demo.
*/
private void createSSLEngines() throws Exception {
/*
* Configure the serverEngine to act as a server in the SSL/TLS
* handshake. Also, require SSL client authentication.
*/
serverEngine = sslc.createSSLEngine();
serverEngine.setUseClientMode(false);
serverEngine.setNeedClientAuth(true);
/*
* Similar to above, but using client mode instead.
*/
clientEngine = sslc.createSSLEngine("client", 80);
clientEngine.setUseClientMode(true);
}
/*
* Create and size the buffers appropriately.
*/
private void createBuffers() {
/*
* We'll assume the buffer sizes are the same between client and server.
*/
SSLSession session = clientEngine.getSession();
int appBufferMax = session.getApplicationBufferSize();
int netBufferMax = session.getPacketBufferSize();
/*
* We'll make the input buffers a bit bigger than the max needed size,
* so that unwrap()s following a successful data transfer won't generate
* BUFFER_OVERFLOWS.
*
* We'll use a mix of direct and indirect ByteBuffers for tutorial
* purposes only. In reality, only use direct ByteBuffers when they give
* a clear performance enhancement.
*/
clientIn = ByteBuffer.allocate(appBufferMax + 50);
serverIn = ByteBuffer.allocate(appBufferMax + 50);
cTOs = ByteBuffer.allocateDirect(netBufferMax);
sTOc = ByteBuffer.allocateDirect(netBufferMax);
clientOut = ByteBuffer.wrap("Hi Server, I'm Client".getBytes());
serverOut = ByteBuffer.wrap("Hello Client, I'm Server".getBytes());
}
/*
* If the result indicates that we have outstanding tasks to do, go ahead
* and run them in this thread.
*/
private static void runDelegatedTasks(SSLEngineResult result,
SSLEngine engine) throws Exception {
if (result.getHandshakeStatus() == HandshakeStatus.NEED_TASK) {
Runnable runnable;
while ((runnable = engine.getDelegatedTask()) != null) {
log("\trunning delegated task...");
runnable.run();
}
HandshakeStatus hsStatus = engine.getHandshakeStatus();
if (hsStatus == HandshakeStatus.NEED_TASK) {
throw new Exception("handshake shouldn't need additional tasks");
}
log("\tnew HandshakeStatus: " + hsStatus);
}
}
private static boolean isEngineClosed(SSLEngine engine) {
return (engine.isOutboundDone() && engine.isInboundDone());
}
/*
* Simple check to make sure everything came across as expected.
*/
private static void checkTransfer(ByteBuffer a, ByteBuffer b)
throws Exception {
a.flip();
b.flip();
if (!a.equals(b)) {
throw new Exception("Data didn't transfer cleanly");
} else {
log("\tData transferred cleanly");
}
a.position(a.limit());
b.position(b.limit());
a.limit(a.capacity());
b.limit(b.capacity());
}
/*
* Logging code
*/
private static boolean resultOnce = true;
private static void log(String str, SSLEngineResult result) {
if (!logging) {
return;
}
if (resultOnce) {
resultOnce = false;
System.out.println("The format of the SSLEngineResult is: \n"
+ "\t\"getStatus() / getHandshakeStatus()\" +\n"
+ "\t\"bytesConsumed() / bytesProduced()\"\n");
}
HandshakeStatus hsStatus = result.getHandshakeStatus();
log(str + result.getStatus() + "/" + hsStatus + ", "
+ result.bytesConsumed() + "/" + result.bytesProduced()
+ " bytes");
if (hsStatus == HandshakeStatus.FINISHED) {
log("\t...ready for application data");
}
}
private static void log(String str) {
if (logging) {
System.out.println(str);
}
}
}