ProxyCommand support (Issue 970) (#971)

* Added SocketClient.connectVia(InputStream, OutputStream) method for ProxyCommand support (#970)

* Added ProxyCommand example (#970)

* Comment only (#970)

* NullPointerException (#970)

* small change to trigger workflow

Author: knoxg

examples/src/main/java/net/schmizz/sshj/examples/ProxyCommand.java

@@ -0,0 +1,66 @@
+package net.schmizz.sshj.examples;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.concurrent.TimeUnit;
+
+import net.schmizz.sshj.SSHClient;
+import net.schmizz.sshj.common.IOUtils;
+import net.schmizz.sshj.connection.channel.direct.Session;
+import net.schmizz.sshj.transport.verification.PromiscuousVerifier;
+
+/**
+ * This example uses a separate process to handle I/O, similar to the "ProxyCommand" directive in openssh.
+ * 
+ */
+public class ProxyCommand {
+    public static void main(String... args)
+            throws IOException {
+    	
+    	/* 
+    	for testing, uses a locally-installed ssh client,
+    	
+    	but for AWS SSM, once you've negotiated the OAuth/SAML login for SSO, 
+    	then called StsClient.getCallerIdentity() to check that worked
+    	then called Ec2Client.describeInstances() to convert an IP to an instanceId/availableZone combo
+    	then called Ec2InstanceConnectClient.sendSSHPublicKey() to open a 60-second login window 
+    	you'd create an SSM ssh session via something like
+    	 
+    	ProcessBuilder pb = new ProcessBuilder("aws", "ssm", "start-session", "--region", "ap-southeast-2", "--target", instanceId,
+	       "--document-name", "AWS-StartSSHSession",
+	       "--parameters", "portNumber=22"
+	    
+	    and wire up the inputStreams/outputStreams from that instead.
+    	*/
+    	
+    	
+    	// for testing only
+    	String jumpBox = "localhost";   // this would typically be something remote
+    	String targetBox = "localhost"; // this would typically be something even more remote    	
+    	ProcessBuilder pb = new ProcessBuilder("ssh", jumpBox, "-W", targetBox + ":22");
+    	Process proc = pb.start();
+    	InputStream recvStream = proc.getInputStream();
+    	OutputStream xmitStream = proc.getOutputStream();
+    	
+        SSHClient ssh = new SSHClient();
+        ssh.addHostKeyVerifier(new PromiscuousVerifier());
+        ssh.connectVia(recvStream, xmitStream);
+        
+        try {
+            ssh.authPublickey(System.getProperty("user.name"));
+            final Session session = ssh.startSession();
+            try {
+                final Session.Command cmd = session.exec("ping -c 1 google.com");
+                System.out.println(IOUtils.readFully(cmd.getInputStream()).toString());
+                cmd.join(5, TimeUnit.SECONDS);
+                System.out.println("\n** exit status: " + cmd.getExitStatus());
+            } finally {
+                session.close();
+            }
+        } finally {
+        	ssh.disconnect();
+        	ssh.close();
+        }
+    }
+}

src/main/java/net/schmizz/sshj/SocketClient.java

@@ -94,6 +94,16 @@ public void connectVia(Channel channel, String hostname, int port) throws IOExce
         onConnect();
     }
 
+    /** Connect using the supplied InputStream and OutputStream. */
+    public void connectVia(InputStream input, OutputStream output) throws IOException {
+        this.hostname = "localhost"; 
+        this.port = 65535;
+        this.input = input;
+        this.output = output;
+        this.tunneled = true;
+        onConnect();
+    }
+
     /** Connect to a remote address via a direct TCP/IP connection from the server. */
     public void connectVia(DirectConnection directConnection) throws IOException {
         connectVia(directConnection, directConnection.getRemoteHost(), directConnection.getRemotePort());