/*
    * Copyright (C) 2018, Sasa Zivkov <sasa.zivkov@sap.com>
    * Copyright (C) 2016, Mark Ingram <markdingram@gmail.com>
    * Copyright (C) 2009, Constantine Plotnikov <constantine.plotnikov@gmail.com>
    * Copyright (C) 2008-2009, Google Inc.
    * Copyright (C) 2009, Google, Inc.
    * Copyright (C) 2009, JetBrains s.r.o.
    * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
    * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> and others
   *
   * This program and the accompanying materials are made available under the
   * terms of the Eclipse Distribution License v. 1.0 which is available at
   * https://www.eclipse.org/org/documents/edl-v10.php.
   *
   * SPDX-License-Identifier: BSD-3-Clause
   */
  
  package org.eclipse.jgit.transport;
  
  import static java.util.stream.Collectors.joining;
  import static java.util.stream.Collectors.toList;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.net.ConnectException;
  import java.net.UnknownHostException;
  import java.text.MessageFormat;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  import java.util.concurrent.TimeUnit;
  import java.util.stream.Stream;
  
  import org.eclipse.jgit.errors.TransportException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.util.FS;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.jcraft.jsch.ConfigRepository;
  import com.jcraft.jsch.ConfigRepository.Config;
  import com.jcraft.jsch.HostKey;
  import com.jcraft.jsch.HostKeyRepository;
  import com.jcraft.jsch.JSch;
  import com.jcraft.jsch.JSchException;
  import com.jcraft.jsch.Session;
  
  /**
   * The base session factory that loads known hosts and private keys from
   * <code>$HOME/.ssh</code>.
   * <p>
   * This is the default implementation used by JGit and provides most of the
   * compatibility necessary to match OpenSSH, a popular implementation of SSH
   * used by C Git.
   * <p>
   * The factory does not provide UI behavior. Override the method
   * {@link #configure(org.eclipse.jgit.transport.OpenSshConfig.Host, Session)} to
   * supply appropriate {@link com.jcraft.jsch.UserInfo} to the session.
   */
  public abstract class JschConfigSessionFactory extends SshSessionFactory {
  
  	private static final Logger LOG = LoggerFactory
  			.getLogger(JschConfigSessionFactory.class);
  
  	/**
  	 * We use different Jsch instances for hosts that have an IdentityFile
  	 * configured in ~/.ssh/config. Jsch by default would cache decrypted keys
  	 * only per session, which results in repeated password prompts. Using
  	 * different Jsch instances, we can cache the keys on these instances so
  	 * that they will be re-used for successive sessions, and thus the user is
  	 * prompted for a key password only once while Eclipse runs.
  	 */
  	private final Map<String, JSch> byIdentityFile = new HashMap<>();
  
  	private JSch defaultJSch;
  
  	private OpenSshConfig config;
  
  	/** {@inheritDoc} */
  	@Override
  	public synchronized RemoteSession getSession(URIish uri,
  			CredentialsProvider credentialsProvider, FS fs, int tms)
  			throws TransportException {
  
  		String user = uri.getUser();
  		final String pass = uri.getPass();
  		String host = uri.getHost();
  		int port = uri.getPort();
  
  		try {
  			if (config == null)
  				config = OpenSshConfig.get(fs);
  
  			final OpenSshConfig.Host hc = config.lookup(host);
 			if (port <= 0)
 				port = hc.getPort();
 			if (user == null)
 				user = hc.getUser();
 
 			Session session = createSession(credentialsProvider, fs, user,
 					pass, host, port, hc);
 
 			int retries = 0;
 			while (!session.isConnected()) {
 				try {
 					retries++;
 					session.connect(tms);
 				} catch (JSchException e) {
 					session.disconnect();
 					session = null;
 					// Make sure our known_hosts is not outdated
 					knownHosts(getJSch(hc, fs), fs);
 
 					if (isAuthenticationCanceled(e)) {
 						throw e;
 					} else if (isAuthenticationFailed(e)
 							&& credentialsProvider != null) {
 						// if authentication failed maybe credentials changed at
 						// the remote end therefore reset credentials and retry
 						if (retries < 3) {
 							credentialsProvider.reset(uri);
 							session = createSession(credentialsProvider, fs,
 									user, pass, host, port, hc);
 						} else
 							throw e;
 					} else if (retries >= hc.getConnectionAttempts()) {
 						throw e;
 					} else {
 						try {
 							Thread.sleep(1000);
 							session = createSession(credentialsProvider, fs,
 									user, pass, host, port, hc);
 						} catch (InterruptedException e1) {
 							throw new TransportException(
 									JGitText.get().transportSSHRetryInterrupt,
 									e1);
 						}
 					}
 				}
 			}
 
 			return new JschSession(session, uri);
 
 		} catch (JSchException je) {
 			final Throwable c = je.getCause();
 			if (c instanceof UnknownHostException) {
 				throw new TransportException(uri, JGitText.get().unknownHost,
 						je);
 			}
 			if (c instanceof ConnectException) {
 				throw new TransportException(uri, c.getMessage(), je);
 			}
 			throw new TransportException(uri, je.getMessage(), je);
 		}
 
 	}
 
 	private static boolean isAuthenticationFailed(JSchException e) {
 		return e.getCause() == null && e.getMessage().equals("Auth fail"); //$NON-NLS-1$
 	}
 
 	private static boolean isAuthenticationCanceled(JSchException e) {
 		return e.getCause() == null && e.getMessage().equals("Auth cancel"); //$NON-NLS-1$
 	}
 
 	// Package visibility for tests
 	Session createSession(CredentialsProvider credentialsProvider,
 			FS fs, String user, final String pass, String host, int port,
 			final OpenSshConfig.Host hc) throws JSchException {
 		final Session session = createSession(hc, user, host, port, fs);
 		// Jsch will have overridden the explicit user by the one from the SSH
 		// config file...
 		setUserName(session, user);
 		// Jsch will also have overridden the port.
 		if (port > 0 && port != session.getPort()) {
 			session.setPort(port);
 		}
 		// We retry already in getSession() method. JSch must not retry
 		// on its own.
 		session.setConfig("MaxAuthTries", "1"); //$NON-NLS-1$ //$NON-NLS-2$
 		if (pass != null)
 			session.setPassword(pass);
 		final String strictHostKeyCheckingPolicy = hc
 				.getStrictHostKeyChecking();
 		if (strictHostKeyCheckingPolicy != null)
 			session.setConfig("StrictHostKeyChecking", //$NON-NLS-1$
 					strictHostKeyCheckingPolicy);
 		final String pauth = hc.getPreferredAuthentications();
 		if (pauth != null)
 			session.setConfig("PreferredAuthentications", pauth); //$NON-NLS-1$
 		if (credentialsProvider != null
 				&& (!hc.isBatchMode() || !credentialsProvider.isInteractive())) {
 			session.setUserInfo(new CredentialsProviderUserInfo(session,
 					credentialsProvider));
 		}
 		safeConfig(session, hc.getConfig());
 		if (hc.getConfig().getValue("HostKeyAlgorithms") == null) { //$NON-NLS-1$
 			setPreferredKeyTypesOrder(session);
 		}
 		configure(hc, session);
 		return session;
 	}
 
 	private void safeConfig(Session session, Config cfg) {
 		// Ensure that Jsch checks all configured algorithms, not just its
 		// built-in ones. Otherwise it may propose an algorithm for which it
 		// doesn't have an implementation, and then run into an NPE if that
 		// algorithm ends up being chosen.
 		copyConfigValueToSession(session, cfg, "Ciphers", "CheckCiphers"); //$NON-NLS-1$ //$NON-NLS-2$
 		copyConfigValueToSession(session, cfg, "KexAlgorithms", "CheckKexes"); //$NON-NLS-1$ //$NON-NLS-2$
 		copyConfigValueToSession(session, cfg, "HostKeyAlgorithms", //$NON-NLS-1$
 				"CheckSignatures"); //$NON-NLS-1$
 	}
 
 	private static void setPreferredKeyTypesOrder(Session session) {
 		HostKeyRepository hkr = session.getHostKeyRepository();
 		HostKey[] hostKeys = hkr.getHostKey(hostName(session), null);
 
 		if (hostKeys == null) {
 			return;
 		}
 
 		List<String> known = Stream.of(hostKeys)
 				.map(HostKey::getType)
 				.collect(toList());
 
 		if (!known.isEmpty()) {
 			String serverHostKey = "server_host_key"; //$NON-NLS-1$
 			String current = session.getConfig(serverHostKey);
 			if (current == null) {
 				session.setConfig(serverHostKey, String.join(",", known)); //$NON-NLS-1$
 				return;
 			}
 
 			String knownFirst = Stream.concat(
 							known.stream(),
 							Stream.of(current.split(",")) //$NON-NLS-1$
 									.filter(s -> !known.contains(s)))
 					.collect(joining(",")); //$NON-NLS-1$
 			session.setConfig(serverHostKey, knownFirst);
 		}
 	}
 
 	private static String hostName(Session s) {
 		if (s.getPort() == SshConstants.SSH_DEFAULT_PORT) {
 			return s.getHost();
 		}
 		return String.format("[%s]:%d", s.getHost(), //$NON-NLS-1$
 				Integer.valueOf(s.getPort()));
 	}
 
 	private void copyConfigValueToSession(Session session, Config cfg,
 			String from, String to) {
 		String value = cfg.getValue(from);
 		if (value != null) {
 			session.setConfig(to, value);
 		}
 	}
 
 	private void setUserName(Session session, String userName) {
 		// Jsch 0.1.54 picks up the user name from the ssh config, even if an
 		// explicit user name was given! We must correct that if ~/.ssh/config
 		// has a different user name.
 		if (userName == null || userName.isEmpty()
 				|| userName.equals(session.getUserName())) {
 			return;
 		}
 		try {
 			Class<?>[] parameterTypes = { String.class };
 			Method method = Session.class.getDeclaredMethod("setUserName", //$NON-NLS-1$
 					parameterTypes);
 			method.setAccessible(true);
 			method.invoke(session, userName);
 		} catch (NullPointerException | IllegalAccessException
 				| IllegalArgumentException | InvocationTargetException
 				| NoSuchMethodException | SecurityException e) {
 			LOG.error(MessageFormat.format(JGitText.get().sshUserNameError,
 					userName, session.getUserName()), e);
 		}
 	}
 
 	/**
 	 * Create a new remote session for the requested address.
 	 *
 	 * @param hc
 	 *            host configuration
 	 * @param user
 	 *            login to authenticate as.
 	 * @param host
 	 *            server name to connect to.
 	 * @param port
 	 *            port number of the SSH daemon (typically 22).
 	 * @param fs
 	 *            the file system abstraction which will be necessary to
 	 *            perform certain file system operations.
 	 * @return new session instance, but otherwise unconfigured.
 	 * @throws com.jcraft.jsch.JSchException
 	 *             the session could not be created.
 	 */
 	protected Session createSession(final OpenSshConfig.Host hc,
 			final String user, final String host, final int port, FS fs)
 			throws JSchException {
 		return getJSch(hc, fs).getSession(user, host, port);
 	}
 
 	/**
 	 * Provide additional configuration for the JSch instance. This method could
 	 * be overridden to supply a preferred
 	 * {@link com.jcraft.jsch.IdentityRepository}.
 	 *
 	 * @param jsch
 	 *            jsch instance
 	 * @since 4.5
 	 */
 	protected void configureJSch(JSch jsch) {
 		// No additional configuration required.
 	}
 
 	/**
 	 * Provide additional configuration for the session based on the host
 	 * information. This method could be used to supply
 	 * {@link com.jcraft.jsch.UserInfo}.
 	 *
 	 * @param hc
 	 *            host configuration
 	 * @param session
 	 *            session to configure
 	 */
 	protected abstract void configure(OpenSshConfig.Host hc, Session session);
 
 	/**
 	 * Obtain the JSch used to create new sessions.
 	 *
 	 * @param hc
 	 *            host configuration
 	 * @param fs
 	 *            the file system abstraction which will be necessary to
 	 *            perform certain file system operations.
 	 * @return the JSch instance to use.
 	 * @throws com.jcraft.jsch.JSchException
 	 *             the user configuration could not be created.
 	 */
 	protected JSch getJSch(OpenSshConfig.Host hc, FS fs) throws JSchException {
 		if (defaultJSch == null) {
 			defaultJSch = createDefaultJSch(fs);
 			if (defaultJSch.getConfigRepository() == null) {
 				defaultJSch.setConfigRepository(
 						new JschBugFixingConfigRepository(config));
 			}
 			for (Object name : defaultJSch.getIdentityNames())
 				byIdentityFile.put((String) name, defaultJSch);
 		}
 
 		final File identityFile = hc.getIdentityFile();
 		if (identityFile == null)
 			return defaultJSch;
 
 		final String identityKey = identityFile.getAbsolutePath();
 		JSch jsch = byIdentityFile.get(identityKey);
 		if (jsch == null) {
 			jsch = new JSch();
 			configureJSch(jsch);
 			if (jsch.getConfigRepository() == null) {
 				jsch.setConfigRepository(defaultJSch.getConfigRepository());
 			}
 			jsch.setHostKeyRepository(defaultJSch.getHostKeyRepository());
 			jsch.addIdentity(identityKey);
 			byIdentityFile.put(identityKey, jsch);
 		}
 		return jsch;
 	}
 
 	/**
 	 * Create default instance of jsch
 	 *
 	 * @param fs
 	 *            the file system abstraction which will be necessary to perform
 	 *            certain file system operations.
 	 * @return the new default JSch implementation.
 	 * @throws com.jcraft.jsch.JSchException
 	 *             known host keys cannot be loaded.
 	 */
 	protected JSch createDefaultJSch(FS fs) throws JSchException {
 		final JSch jsch = new JSch();
 		JSch.setConfig("ssh-rsa", JSch.getConfig("signature.rsa")); //$NON-NLS-1$ //$NON-NLS-2$
 		JSch.setConfig("ssh-dss", JSch.getConfig("signature.dss")); //$NON-NLS-1$ //$NON-NLS-2$
 		configureJSch(jsch);
 		knownHosts(jsch, fs);
 		identities(jsch, fs);
 		return jsch;
 	}
 
 	private static void knownHosts(JSch sch, FS fs) throws JSchException {
 		final File home = fs.userHome();
 		if (home == null)
 			return;
 		final File known_hosts = new File(new File(home, ".ssh"), "known_hosts"); //$NON-NLS-1$ //$NON-NLS-2$
 		try (FileInputStream in = new FileInputStream(known_hosts)) {
 			sch.setKnownHosts(in);
 		} catch (FileNotFoundException none) {
 			// Oh well. They don't have a known hosts in home.
 		} catch (IOException err) {
 			// Oh well. They don't have a known hosts in home.
 		}
 	}
 
 	private static void identities(JSch sch, FS fs) {
 		final File home = fs.userHome();
 		if (home == null)
 			return;
 		final File sshdir = new File(home, ".ssh"); //$NON-NLS-1$
 		if (sshdir.isDirectory()) {
 			loadIdentity(sch, new File(sshdir, "identity")); //$NON-NLS-1$
 			loadIdentity(sch, new File(sshdir, "id_rsa")); //$NON-NLS-1$
 			loadIdentity(sch, new File(sshdir, "id_dsa")); //$NON-NLS-1$
 		}
 	}
 
 	private static void loadIdentity(JSch sch, File priv) {
 		if (priv.isFile()) {
 			try {
 				sch.addIdentity(priv.getAbsolutePath());
 			} catch (JSchException e) {
 				// Instead, pretend the key doesn't exist.
 			}
 		}
 	}
 
 	private static class JschBugFixingConfigRepository
 			implements ConfigRepository {
 
 		private final ConfigRepository base;
 
 		public JschBugFixingConfigRepository(ConfigRepository base) {
 			this.base = base;
 		}
 
 		@Override
 		public Config getConfig(String host) {
 			return new JschBugFixingConfig(base.getConfig(host));
 		}
 
 		/**
 		 * A {@link com.jcraft.jsch.ConfigRepository.Config} that transforms
 		 * some values from the config file into the format Jsch 0.1.54 expects.
 		 * This is a work-around for bugs in Jsch.
 		 * <p>
 		 * Additionally, this config hides the IdentityFile config entries from
 		 * Jsch; we manage those ourselves. Otherwise Jsch would cache passwords
 		 * (or rather, decrypted keys) only for a single session, resulting in
 		 * multiple password prompts for user operations that use several Jsch
 		 * sessions.
 		 */
 		private static class JschBugFixingConfig implements Config {
 
 			private static final String[] NO_IDENTITIES = {};
 
 			private final Config real;
 
 			public JschBugFixingConfig(Config delegate) {
 				real = delegate;
 			}
 
 			@Override
 			public String getHostname() {
 				return real.getHostname();
 			}
 
 			@Override
 			public String getUser() {
 				return real.getUser();
 			}
 
 			@Override
 			public int getPort() {
 				return real.getPort();
 			}
 
 			@Override
 			public String getValue(String key) {
 				String k = key.toUpperCase(Locale.ROOT);
 				if ("IDENTITYFILE".equals(k)) { //$NON-NLS-1$
 					return null;
 				}
 				String result = real.getValue(key);
 				if (result != null) {
 					if ("SERVERALIVEINTERVAL".equals(k) //$NON-NLS-1$
 							|| "CONNECTTIMEOUT".equals(k)) { //$NON-NLS-1$
 						// These values are in seconds. Jsch 0.1.54 passes them
 						// on as is to java.net.Socket.setSoTimeout(), which
 						// expects milliseconds. So convert here to
 						// milliseconds.
 						try {
 							int timeout = Integer.parseInt(result);
 							result = Long.toString(
 									TimeUnit.SECONDS.toMillis(timeout));
 						} catch (NumberFormatException e) {
 							// Ignore
 						}
 					}
 				}
 				return result;
 			}
 
 			@Override
 			public String[] getValues(String key) {
 				String k = key.toUpperCase(Locale.ROOT);
 				if ("IDENTITYFILE".equals(k)) { //$NON-NLS-1$
 					return NO_IDENTITIES;
 				}
 				return real.getValues(key);
 			}
 		}
 	}
 
 	/**
 	 * Set the {@link OpenSshConfig} to use. Intended for use in tests.
 	 *
 	 * @param config
 	 *            to use
 	 */
 	synchronized void setConfig(OpenSshConfig config) {
 		this.config = config;
 	}
 }