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Panda Core is the core module of Panda Framework, it contains commonly used utility classes similar to apache-commons.

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package panda.net.smtp;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.KeyManager;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLHandshakeException;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;

import panda.net.io.CRLFLineReader;
import panda.net.ssl.SSLContexts;
import panda.net.ssl.SSLSockets;

/**
 * SMTP over SSL processing. Copied from FTPSClient.java and modified to suit SMTP. If implicit mode
 * is selected (NOT the default), SSL/TLS negotiation starts right after the connection has been
 * established. In explicit mode (the default), SSL/TLS negotiation starts when the user calls
 * execTLS() and the server accepts the command. Implicit usage: SMTPSClient c = new
 * SMTPSClient(true); c.connect("127.0.0.1", 465); Explicit usage: SMTPSClient c = new
 * SMTPSClient(); c.connect("127.0.0.1", 25); if (c.execTLS()) { /rest of the commands here/ }
 * Warning: the hostname is not verified against the certificate by default, use
 * {@link #setHostnameVerifier(HostnameVerifier)} or {@link #setEndpointCheckingEnabled(boolean)}
 * (on Java 1.7+) to enable verification.
 */
public class SMTPSClient extends SMTPClient {
	/** Default secure socket protocol name, like TLS */
	public static final String DEFAULT_PROTOCOL = SSLContexts.PROTO_TLS;

	/** The security mode. True - Implicit Mode / False - Explicit Mode. */
	private final boolean isImplicit;
	/** The secure socket protocol to be used, like SSL/TLS. */
	private final String protocol;
	/** The context object. */
	private SSLContext context = null;
	/**
	 * The cipher suites. SSLSockets have a default set of these anyway, so no initialization
	 * required.
	 */
	private String[] suites = null;
	/** The protocol versions. */
	private String[] protocols = null;

	/** The {@link TrustManager} implementation, default null (i.e. use system managers). */
	private TrustManager trustManager = null;

	/** The {@link KeyManager}, default null (i.e. use system managers). */
	private KeyManager keyManager = null; // seems not to be required

	/** The {@link HostnameVerifier} to use post-TLS, default null (i.e. no verification). */
	private HostnameVerifier hostnameVerifier = null;

	/** Use Java 1.7+ HTTPS Endpoint Identification Algorithim. */
	private boolean tlsEndpointChecking;

	/**
	 * Constructor for SMTPSClient, using {@link #DEFAULT_PROTOCOL} i.e. TLS Sets security mode to
	 * explicit (isImplicit = false).
	 */
	public SMTPSClient() {
		this(DEFAULT_PROTOCOL, false);
	}

	/**
	 * Constructor for SMTPSClient, using {@link #DEFAULT_PROTOCOL} i.e. TLS
	 * 
	 * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
	 */
	public SMTPSClient(boolean implicit) {
		this(DEFAULT_PROTOCOL, implicit);
	}

	/**
	 * Constructor for SMTPSClient, using explicit security mode.
	 * 
	 * @param proto the protocol.
	 */
	public SMTPSClient(String proto) {
		this(proto, false);
	}

	/**
	 * Constructor for SMTPSClient.
	 * 
	 * @param proto the protocol.
	 * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
	 */
	public SMTPSClient(String proto, boolean implicit) {
		protocol = proto;
		isImplicit = implicit;
	}

	/**
	 * Constructor for SMTPSClient.
	 * 
	 * @param proto the protocol.
	 * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
	 * @param encoding the encoding
	 */
	public SMTPSClient(String proto, boolean implicit, String encoding) {
		super(encoding);
		protocol = proto;
		isImplicit = implicit;
	}

	/**
	 * Constructor for SMTPSClient, using {@link #DEFAULT_PROTOCOL} i.e. TLS
	 * 
	 * @param implicit The security mode, {@code true} for implicit, {@code false} for explicit
	 * @param ctx A pre-configured SSL Context.
	 */
	public SMTPSClient(boolean implicit, SSLContext ctx) {
		isImplicit = implicit;
		context = ctx;
		protocol = DEFAULT_PROTOCOL;
	}

	/**
	 * Constructor for SMTPSClient.
	 * 
	 * @param context A pre-configured SSL Context.
	 * @see #SMTPSClient(boolean, SSLContext)
	 */
	public SMTPSClient(SSLContext context) {
		this(false, context);
	}

	/**
	 * Because there are so many connect() methods, the _connectAction_() method is provided as a
	 * means of performing some action immediately after establishing a connection, rather than
	 * reimplementing all of the connect() methods.
	 * 
	 * @throws IOException If it is thrown by _connectAction_().
	 * @see panda.net.SocketClient#_connectAction_()
	 */
	@Override
	protected void _connectAction_() throws IOException {
		// Implicit mode.
		if (isImplicit) {
			performSSLNegotiation();
		}
		super._connectAction_();
		// Explicit mode - don't do anything. The user calls execTLS()
	}

	/**
	 * Performs a lazy init of the SSL context.
	 * 
	 * @throws IOException When could not initialize the SSL context.
	 */
	private void initSSLContext() throws IOException {
		if (context == null) {
			context = SSLContexts.createSSLContext(protocol, getKeyManager(), getTrustManager());
		}
	}

	/**
	 * SSL/TLS negotiation. Acquires an SSL socket of a connection and carries out handshake
	 * processing.
	 * 
	 * @throws IOException If server negotiation fails.
	 */
	private void performSSLNegotiation() throws IOException {
		initSSLContext();

		SSLSocketFactory ssf = context.getSocketFactory();
		String host = (_hostname_ != null) ? _hostname_ : getRemoteAddress().getHostAddress();
		int port = getRemotePort();
		SSLSocket socket = (SSLSocket)ssf.createSocket(_socket_, host, port, true);
		socket.setEnableSessionCreation(true);
		socket.setUseClientMode(true);

		if (tlsEndpointChecking) {
			SSLSockets.enableEndpointNameVerification(socket);
		}
		if (protocols != null) {
			socket.setEnabledProtocols(protocols);
		}
		if (suites != null) {
			socket.setEnabledCipherSuites(suites);
		}
		socket.startHandshake();

		// TODO the following setup appears to duplicate that in the super class methods
		_socket_ = socket;
		_input_ = socket.getInputStream();
		_output_ = socket.getOutputStream();
		_reader = new CRLFLineReader(new InputStreamReader(_input_, encoding));
		_writer = new BufferedWriter(new OutputStreamWriter(_output_, encoding));

		if (hostnameVerifier != null && !hostnameVerifier.verify(host, socket.getSession())) {
			throw new SSLHandshakeException("Hostname doesn't match certificate");
		}
	}

	/**
	 * Get the {@link KeyManager} instance.
	 * 
	 * @return The current {@link KeyManager} instance.
	 */
	public KeyManager getKeyManager() {
		return keyManager;
	}

	/**
	 * Set a {@link KeyManager} to use.
	 * 
	 * @param newKeyManager The KeyManager implementation to set.
	 * @see panda.net.ssl.KeyManagers
	 */
	public void setKeyManager(KeyManager newKeyManager) {
		keyManager = newKeyManager;
	}

	/**
	 * Controls which particular cipher suites are enabled for use on this connection. Called before
	 * server negotiation.
	 * 
	 * @param cipherSuites The cipher suites.
	 */
	public void setEnabledCipherSuites(String[] cipherSuites) {
		suites = new String[cipherSuites.length];
		System.arraycopy(cipherSuites, 0, suites, 0, cipherSuites.length);
	}

	/**
	 * Returns the names of the cipher suites which could be enabled for use on this connection.
	 * When the underlying {@link java.net.Socket Socket} is not an {@link SSLSocket} instance,
	 * returns null.
	 * 
	 * @return An array of cipher suite names, or null.
	 */
	public String[] getEnabledCipherSuites() {
		if (_socket_ instanceof SSLSocket) {
			return ((SSLSocket)_socket_).getEnabledCipherSuites();
		}
		return null;
	}

	/**
	 * Controls which particular protocol versions are enabled for use on this connection. I perform
	 * setting before a server negotiation.
	 * 
	 * @param protocolVersions The protocol versions.
	 */
	public void setEnabledProtocols(String[] protocolVersions) {
		protocols = new String[protocolVersions.length];
		System.arraycopy(protocolVersions, 0, protocols, 0, protocolVersions.length);
	}

	/**
	 * Returns the names of the protocol versions which are currently enabled for use on this
	 * connection. When the underlying {@link java.net.Socket Socket} is not an {@link SSLSocket}
	 * instance, returns null.
	 * 
	 * @return An array of protocols, or null.
	 */
	public String[] getEnabledProtocols() {
		if (_socket_ instanceof SSLSocket) {
			return ((SSLSocket)_socket_).getEnabledProtocols();
		}
		return null;
	}

	/**
	 * The TLS command execution.
	 * 
	 * @throws IOException If an I/O error occurs while sending the command or performing the
	 *             negotiation.
	 * @return TRUE if the command and negotiation succeeded.
	 */
	public boolean execTLS() throws IOException {
		if (!SMTPReply.isPositiveCompletion(sendCommand("STARTTLS"))) {
			return false;
			// throw new SSLException(getReplyString());
		}
		performSSLNegotiation();
		return true;
	}

	/**
	 * Get the currently configured {@link TrustManager}.
	 * 
	 * @return A TrustManager instance.
	 */
	public TrustManager getTrustManager() {
		return trustManager;
	}

	/**
	 * Override the default {@link TrustManager} to use.
	 * 
	 * @param newTrustManager The TrustManager implementation to set.
	 * @see panda.net.ssl.TrustManagers
	 */
	public void setTrustManager(TrustManager newTrustManager) {
		trustManager = newTrustManager;
	}

	/**
	 * Get the currently configured {@link HostnameVerifier}.
	 * 
	 * @return A HostnameVerifier instance.
	 */
	public HostnameVerifier getHostnameVerifier() {
		return hostnameVerifier;
	}

	/**
	 * Override the default {@link HostnameVerifier} to use.
	 * 
	 * @param newHostnameVerifier The HostnameVerifier implementation to set or null to
	 *            disable.
	 */
	public void setHostnameVerifier(HostnameVerifier newHostnameVerifier) {
		hostnameVerifier = newHostnameVerifier;
	}

	/**
	 * Return whether or not endpoint identification using the HTTPS algorithm on Java 1.7+ is
	 * enabled. The default behaviour is for this to be disabled.
	 * 
	 * @return True if enabled, false if not.
	 */
	public boolean isEndpointCheckingEnabled() {
		return tlsEndpointChecking;
	}

	/**
	 * Automatic endpoint identification checking using the HTTPS algorithm is supported on Java
	 * 1.7+. The default behaviour is for this to be disabled.
	 * 
	 * @param enable Enable automatic endpoint identification checking using the HTTPS algorithm on
	 *            Java 1.7+.
	 */
	public void setEndpointCheckingEnabled(boolean enable) {
		tlsEndpointChecking = enable;
	}
}

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