// LoadConfig loads and validates a JSON encoded server config.
func LoadConfig(configJSON []byte) (*Config, error) {

	var config Config
	err := json.Unmarshal(configJSON, &config)
	if err != nil {
		return nil, psiphon.ContextError(err)
	}

	if config.Fail2BanFormat != "" && strings.Count(config.Fail2BanFormat, "%s") != 1 {
		return nil, errors.New("Fail2BanFormat must have one '%%s' placeholder")
	}

	if config.ServerIPAddress == "" {
		return nil, errors.New("ServerIPAddress is missing from config file")
	}

	if config.WebServerPort > 0 && (config.WebServerSecret == "" || config.WebServerCertificate == "" ||
		config.WebServerPrivateKey == "") {

		return nil, errors.New(
			"Web server requires WebServerSecret, WebServerCertificate, WebServerPrivateKey")
	}

	for tunnelProtocol, _ := range config.TunnelProtocolPorts {
		if psiphon.TunnelProtocolUsesSSH(tunnelProtocol) ||
			psiphon.TunnelProtocolUsesObfuscatedSSH(tunnelProtocol) {
			if config.SSHPrivateKey == "" || config.SSHServerVersion == "" ||
				config.SSHUserName == "" || config.SSHPassword == "" {
				return nil, fmt.Errorf(
					"Tunnel protocol %s requires SSHPrivateKey, SSHServerVersion, SSHUserName, SSHPassword",
					tunnelProtocol)
			}
		}
		if psiphon.TunnelProtocolUsesObfuscatedSSH(tunnelProtocol) {
			if config.ObfuscatedSSHKey == "" {
				return nil, fmt.Errorf(
					"Tunnel protocol %s requires ObfuscatedSSHKey",
					tunnelProtocol)
			}
		}
		if psiphon.TunnelProtocolUsesMeekHTTP(tunnelProtocol) ||
			psiphon.TunnelProtocolUsesMeekHTTPS(tunnelProtocol) {
			if config.MeekCookieEncryptionPrivateKey == "" || config.MeekObfuscatedKey == "" {
				return nil, fmt.Errorf(
					"Tunnel protocol %s requires MeekCookieEncryptionPrivateKey, MeekObfuscatedKey",
					tunnelProtocol)
			}
		}
		if psiphon.TunnelProtocolUsesMeekHTTPS(tunnelProtocol) {
			if config.MeekCertificateCommonName == "" {
				return nil, fmt.Errorf(
					"Tunnel protocol %s requires MeekCertificateCommonName",
					tunnelProtocol)
			}
		}
	}

	validateNetworkAddress := func(address string) error {
		host, port, err := net.SplitHostPort(address)
		if err == nil && net.ParseIP(host) == nil {
			err = errors.New("Host must be an IP address")
		}
		if err == nil {
			_, err = strconv.Atoi(port)
		}
		return err
	}

	if config.UDPForwardDNSServerAddress != "" {
		if err := validateNetworkAddress(config.UDPForwardDNSServerAddress); err != nil {
			return nil, fmt.Errorf("UDPForwardDNSServerAddress is invalid: %s", err)
		}
	}

	if config.UDPInterceptUdpgwServerAddress != "" {
		if err := validateNetworkAddress(config.UDPInterceptUdpgwServerAddress); err != nil {
			return nil, fmt.Errorf("UDPInterceptUdpgwServerAddress is invalid: %s", err)
		}
	}

	return &config, nil
}
// GenerateConfig creates a new Psiphon server config. It returns JSON
// encoded configs and a client-compatible "server entry" for the server. It
// generates all necessary secrets and key material, which are emitted in
// the config file and server entry as necessary.
// GenerateConfig uses sample values for many fields. The intention is for
// generated configs to be used for testing or as a template for production
// setup, not to generate production-ready configurations.
func GenerateConfig(params *GenerateConfigParams) ([]byte, []byte, []byte, error) {

	// Input validation

	if net.ParseIP(params.ServerIPAddress) == nil {
		return nil, nil, nil, psiphon.ContextError(errors.New("invalid IP address"))
	}

	if len(params.TunnelProtocolPorts) == 0 {
		return nil, nil, nil, psiphon.ContextError(errors.New("no tunnel protocols"))
	}

	usedPort := make(map[int]bool)
	if params.WebServerPort != 0 {
		usedPort[params.WebServerPort] = true
	}

	usingMeek := false

	for protocol, port := range params.TunnelProtocolPorts {

		if !psiphon.Contains(psiphon.SupportedTunnelProtocols, protocol) {
			return nil, nil, nil, psiphon.ContextError(errors.New("invalid tunnel protocol"))
		}

		if usedPort[port] {
			return nil, nil, nil, psiphon.ContextError(errors.New("duplicate listening port"))
		}
		usedPort[port] = true

		if psiphon.TunnelProtocolUsesMeekHTTP(protocol) ||
			psiphon.TunnelProtocolUsesMeekHTTPS(protocol) {
			usingMeek = true
		}
	}

	// Web server config

	var webServerSecret, webServerCertificate, webServerPrivateKey string

	if params.WebServerPort != 0 {
		var err error
		webServerSecret, err = psiphon.MakeRandomStringHex(WEB_SERVER_SECRET_BYTE_LENGTH)
		if err != nil {
			return nil, nil, nil, psiphon.ContextError(err)
		}

		webServerCertificate, webServerPrivateKey, err = GenerateWebServerCertificate("")
		if err != nil {
			return nil, nil, nil, psiphon.ContextError(err)
		}
	}

	// SSH config

	// TODO: use other key types: anti-fingerprint by varying params
	rsaKey, err := rsa.GenerateKey(rand.Reader, SSH_RSA_HOST_KEY_BITS)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	sshPrivateKey := pem.EncodeToMemory(
		&pem.Block{
			Type:  "RSA PRIVATE KEY",
			Bytes: x509.MarshalPKCS1PrivateKey(rsaKey),
		},
	)

	signer, err := ssh.NewSignerFromKey(rsaKey)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	sshPublicKey := signer.PublicKey()

	sshUserNameSuffix, err := psiphon.MakeRandomStringHex(SSH_USERNAME_SUFFIX_BYTE_LENGTH)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	sshUserName := "******" + sshUserNameSuffix

	sshPassword, err := psiphon.MakeRandomStringHex(SSH_PASSWORD_BYTE_LENGTH)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	// TODO: vary version string for anti-fingerprint
	sshServerVersion := "SSH-2.0-Psiphon"

	// Obfuscated SSH config

	obfuscatedSSHKey, err := psiphon.MakeRandomStringHex(SSH_OBFUSCATED_KEY_BYTE_LENGTH)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	// Meek config

	var meekCookieEncryptionPublicKey, meekCookieEncryptionPrivateKey, meekObfuscatedKey string

	if usingMeek {
		rawMeekCookieEncryptionPublicKey, rawMeekCookieEncryptionPrivateKey, err :=
			box.GenerateKey(rand.Reader)
		if err != nil {
			return nil, nil, nil, psiphon.ContextError(err)
		}

		meekCookieEncryptionPublicKey = base64.StdEncoding.EncodeToString(rawMeekCookieEncryptionPublicKey[:])
		meekCookieEncryptionPrivateKey = base64.StdEncoding.EncodeToString(rawMeekCookieEncryptionPrivateKey[:])

		meekObfuscatedKey, err = psiphon.MakeRandomStringHex(SSH_OBFUSCATED_KEY_BYTE_LENGTH)
		if err != nil {
			return nil, nil, nil, psiphon.ContextError(err)
		}
	}

	// Other config

	discoveryValueHMACKey, err := psiphon.MakeRandomStringBase64(DISCOVERY_VALUE_KEY_BYTE_LENGTH)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	// Assemble configs and server entry

	// Note: this config is intended for either testing or as an illustrative
	// example or template and is not intended for production deployment.

	config := &Config{
		LogLevel:                       "info",
		Fail2BanFormat:                 "Authentication failure for psiphon-client from %s",
		GeoIPDatabaseFilename:          "",
		HostID:                         "example-host-id",
		ServerIPAddress:                params.ServerIPAddress,
		DiscoveryValueHMACKey:          discoveryValueHMACKey,
		WebServerPort:                  params.WebServerPort,
		WebServerSecret:                webServerSecret,
		WebServerCertificate:           webServerCertificate,
		WebServerPrivateKey:            webServerPrivateKey,
		SSHPrivateKey:                  string(sshPrivateKey),
		SSHServerVersion:               sshServerVersion,
		SSHUserName:                    sshUserName,
		SSHPassword:                    sshPassword,
		ObfuscatedSSHKey:               obfuscatedSSHKey,
		TunnelProtocolPorts:            params.TunnelProtocolPorts,
		UDPForwardDNSServerAddress:     "8.8.8.8:53",
		UDPInterceptUdpgwServerAddress: "127.0.0.1:7300",
		MeekCookieEncryptionPrivateKey: meekCookieEncryptionPrivateKey,
		MeekObfuscatedKey:              meekObfuscatedKey,
		MeekCertificateCommonName:      "www.example.org",
		MeekProhibitedHeaders:          nil,
		MeekProxyForwardedForHeaders:   []string{"X-Forwarded-For"},
		LoadMonitorPeriodSeconds:       300,
		TrafficRulesFilename:           params.TrafficRulesFilename,
		LogFilename:                    params.LogFilename,
		Fail2BanLogFilename:            params.Fail2BanLogFilename,
	}

	encodedConfig, err := json.MarshalIndent(config, "\n", "    ")
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	trafficRulesSet := &TrafficRulesSet{
		DefaultRules: TrafficRules{
			DefaultLimits: RateLimits{
				DownstreamUnlimitedBytes: 0,
				DownstreamBytesPerSecond: 0,
				UpstreamUnlimitedBytes:   0,
				UpstreamBytesPerSecond:   0,
			},
			IdleTCPPortForwardTimeoutMilliseconds: 30000,
			IdleUDPPortForwardTimeoutMilliseconds: 30000,
			MaxTCPPortForwardCount:                1024,
			MaxUDPPortForwardCount:                32,
			AllowTCPPorts:                         nil,
			AllowUDPPorts:                         nil,
			DenyTCPPorts:                          nil,
			DenyUDPPorts:                          nil,
		},
	}

	encodedTrafficRulesSet, err := json.MarshalIndent(trafficRulesSet, "\n", "    ")
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	capabilities := []string{}

	if params.EnableSSHAPIRequests {
		capabilities = append(capabilities, psiphon.CAPABILITY_SSH_API_REQUESTS)
	}

	if params.WebServerPort != 0 {
		capabilities = append(capabilities, psiphon.CAPABILITY_UNTUNNELED_WEB_API_REQUESTS)
	}

	for protocol, _ := range params.TunnelProtocolPorts {
		capabilities = append(capabilities, psiphon.GetCapability(protocol))
	}

	sshPort := params.TunnelProtocolPorts["SSH"]
	obfuscatedSSHPort := params.TunnelProtocolPorts["OSSH"]

	// Meek port limitations
	// - fronted meek protocols are hard-wired in the client to be port 443 or 80.
	// - only one other meek port may be specified.
	meekPort := params.TunnelProtocolPorts["UNFRONTED-MEEK-OSSH"]
	if meekPort == 0 {
		meekPort = params.TunnelProtocolPorts["UNFRONTED-MEEK-HTTPS-OSSH"]
	}

	// Note: fronting params are a stub; this server entry will exercise
	// client and server fronting code paths, but not actually traverse
	// a fronting hop.

	serverEntryWebServerPort := ""
	strippedWebServerCertificate := ""

	if params.WebServerPort != 0 {
		serverEntryWebServerPort = fmt.Sprintf("%d", params.WebServerPort)

		// Server entry format omits the BEGIN/END lines and newlines
		lines := strings.Split(webServerCertificate, "\n")
		strippedWebServerCertificate = strings.Join(lines[1:len(lines)-2], "")
	}

	serverEntry := &psiphon.ServerEntry{
		IpAddress:                     params.ServerIPAddress,
		WebServerPort:                 serverEntryWebServerPort,
		WebServerSecret:               webServerSecret,
		WebServerCertificate:          strippedWebServerCertificate,
		SshPort:                       sshPort,
		SshUsername:                   sshUserName,
		SshPassword:                   sshPassword,
		SshHostKey:                    base64.RawStdEncoding.EncodeToString(sshPublicKey.Marshal()),
		SshObfuscatedPort:             obfuscatedSSHPort,
		SshObfuscatedKey:              obfuscatedSSHKey,
		Capabilities:                  capabilities,
		Region:                        "US",
		MeekServerPort:                meekPort,
		MeekCookieEncryptionPublicKey: meekCookieEncryptionPublicKey,
		MeekObfuscatedKey:             meekObfuscatedKey,
		MeekFrontingHosts:             []string{params.ServerIPAddress},
		MeekFrontingAddresses:         []string{params.ServerIPAddress},
		MeekFrontingDisableSNI:        false,
	}

	encodedServerEntry, err := psiphon.EncodeServerEntry(serverEntry)
	if err != nil {
		return nil, nil, nil, psiphon.ContextError(err)
	}

	return encodedConfig, encodedTrafficRulesSet, []byte(encodedServerEntry), nil
}
// runListener is intended to run an a goroutine; it blocks
// running a particular listener. If an unrecoverable error
// occurs, it will send the error to the listenerError channel.
func (sshServer *sshServer) runListener(
	listener net.Listener,
	listenerError chan<- error,
	tunnelProtocol string) {

	handleClient := func(clientConn net.Conn) {
		// process each client connection concurrently
		go sshServer.handleClient(tunnelProtocol, clientConn)
	}

	// Note: when exiting due to a unrecoverable error, be sure
	// to try to send the error to listenerError so that the outer
	// TunnelServer.Run will properly shut down instead of remaining
	// running.

	if psiphon.TunnelProtocolUsesMeekHTTP(tunnelProtocol) ||
		psiphon.TunnelProtocolUsesMeekHTTPS(tunnelProtocol) {

		meekServer, err := NewMeekServer(
			sshServer.support,
			listener,
			psiphon.TunnelProtocolUsesMeekHTTPS(tunnelProtocol),
			handleClient,
			sshServer.shutdownBroadcast)
		if err != nil {
			select {
			case listenerError <- psiphon.ContextError(err):
			default:
			}
			return
		}

		meekServer.Run()

	} else {

		for {
			conn, err := listener.Accept()

			select {
			case <-sshServer.shutdownBroadcast:
				if err == nil {
					conn.Close()
				}
				return
			default:
			}

			if err != nil {
				if e, ok := err.(net.Error); ok && e.Temporary() {
					log.WithContextFields(LogFields{"error": err}).Error("accept failed")
					// Temporary error, keep running
					continue
				}

				select {
				case listenerError <- psiphon.ContextError(err):
				default:
				}
				return
			}

			handleClient(conn)
		}
	}
}