NetBird SSH (#361)

This PR adds support for SSH access through the NetBird network
without managing SSH skeys.
NetBird client app has an embedded SSH server (Linux/Mac only) 
and a netbird ssh command.

client/cmd/root.go

@@ -94,6 +94,7 @@ func init() {
 	rootCmd.AddCommand(statusCmd)
 	rootCmd.AddCommand(loginCmd)
 	rootCmd.AddCommand(versionCmd)
+	rootCmd.AddCommand(sshCmd)
 	serviceCmd.AddCommand(runCmd, startCmd, stopCmd, restartCmd) // service control commands are subcommands of service
 	serviceCmd.AddCommand(installCmd, uninstallCmd)              // service installer commands are subcommands of service
 }

client/cmd/ssh.go

@@ -0,0 +1,137 @@
+package cmd
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"github.com/netbirdio/netbird/client/internal"
+	"github.com/netbirdio/netbird/client/proto"
+	nbssh "github.com/netbirdio/netbird/client/ssh"
+	"github.com/netbirdio/netbird/util"
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+)
+
+var (
+	port int
+	user = "netbird"
+	host string
+)
+
+var sshCmd = &cobra.Command{
+	Use: "ssh",
+	Args: func(cmd *cobra.Command, args []string) error {
+		if len(args) < 1 {
+			return errors.New("requires a host argument")
+		}
+
+		split := strings.Split(args[0], "@")
+		if len(split) == 2 {
+			user = split[0]
+			host = split[1]
+		} else {
+			host = args[0]
+		}
+
+		return nil
+	},
+	Short: "connect to a remote SSH server",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		SetFlagsFromEnvVars()
+
+		cmd.SetOut(cmd.OutOrStdout())
+
+		err := util.InitLog(logLevel, "console")
+		if err != nil {
+			return fmt.Errorf("failed initializing log %v", err)
+		}
+
+		if !util.IsAdmin() {
+			cmd.Printf("error: you must have Administrator privileges to run this command\n")
+			return nil
+		}
+
+		ctx := internal.CtxInitState(cmd.Context())
+
+		conn, err := DialClientGRPCServer(ctx, daemonAddr)
+		if err != nil {
+			return fmt.Errorf("failed to connect to daemon error: %v\n"+
+				"If the daemon is not running please run: "+
+				"\nnetbird service install \nnetbird service start\n", err)
+		}
+
+		defer func() {
+			err := conn.Close()
+			if err != nil {
+				log.Warnf("failed closing dameon gRPC client connection %v", err)
+				return
+			}
+		}()
+		client := proto.NewDaemonServiceClient(conn)
+
+		status, err := client.Status(ctx, &proto.StatusRequest{})
+		if err != nil {
+			return fmt.Errorf("unable to get daemon status: %v", err)
+		}
+
+		if status.Status != string(internal.StatusConnected) {
+			// todo maybe automatically start it?
+			cmd.Printf("You are disconnected from the NetBird network. Please run the UP command first to connect: \n\n" +
+				" netbird up \n\n")
+			return nil
+		}
+
+		config, err := internal.ReadConfig("", "", configPath, nil)
+		if err != nil {
+			return err
+		}
+
+		sig := make(chan os.Signal, 1)
+		signal.Notify(sig, syscall.SIGTERM, syscall.SIGINT)
+		sshctx, cancel := context.WithCancel(ctx)
+
+		go func() {
+			if err := runSSH(sshctx, host, []byte(config.SSHKey)); err != nil {
+				log.Print(err)
+			}
+			cancel()
+		}()
+
+		select {
+		case <-sig:
+			cancel()
+		case <-sshctx.Done():
+		}
+
+		return nil
+	},
+}
+
+func runSSH(ctx context.Context, addr string, pemKey []byte) error {
+	c, err := nbssh.DialWithKey(fmt.Sprintf("%s:%d", addr, port), user, pemKey)
+	if err != nil {
+		return err
+	}
+	go func() {
+		<-ctx.Done()
+		err = c.Close()
+		if err != nil {
+			return
+		}
+	}()
+
+	err = c.OpenTerminal()
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func init() {
+	sshCmd.PersistentFlags().IntVarP(&port, "port", "p", nbssh.DefaultSSHPort, "Sets remote SSH port. Defaults to "+fmt.Sprint(nbssh.DefaultSSHPort))
+}

client/internal/config.go

@@ -3,16 +3,16 @@ package internal
 import (
 	"context"
 	"fmt"
+	"github.com/netbirdio/netbird/client/ssh"
+	"github.com/netbirdio/netbird/iface"
 	mgm "github.com/netbirdio/netbird/management/client"
+	"github.com/netbirdio/netbird/util"
+	log "github.com/sirupsen/logrus"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 	"net/url"
 	"os"
-
-	"github.com/netbirdio/netbird/iface"
-	"github.com/netbirdio/netbird/util"
-	log "github.com/sirupsen/logrus"
-	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
 )
 
 var managementURLDefault *url.URL
@@ -38,12 +38,18 @@ type Config struct {
 	AdminURL       *url.URL
 	WgIface        string
 	IFaceBlackList []string
+	// SSHKey is a private SSH key in a PEM format
+	SSHKey string
 }
 
 // createNewConfig creates a new config generating a new Wireguard key and saving to file
 func createNewConfig(managementURL, adminURL, configPath, preSharedKey string) (*Config, error) {
 	wgKey := generateKey()
-	config := &Config{PrivateKey: wgKey, WgIface: iface.WgInterfaceDefault, IFaceBlackList: []string{}}
+	pem, err := ssh.GeneratePrivateKey(ssh.ED25519)
+	if err != nil {
+		return nil, err
+	}
+	config := &Config{SSHKey: string(pem), PrivateKey: wgKey, WgIface: iface.WgInterfaceDefault, IFaceBlackList: []string{}}
 	if managementURL != "" {
 		URL, err := parseURL("Management URL", managementURL)
 		if err != nil {
@@ -61,7 +67,7 @@ func createNewConfig(managementURL, adminURL, configPath, preSharedKey string) (
 	config.IFaceBlackList = []string{iface.WgInterfaceDefault, "tun0", "zt", "ZeroTier", "utun", "wg", "ts",
 		"Tailscale", "tailscale"}
 
-	err := util.WriteJson(configPath, config)
+	err = util.WriteJson(configPath, config)
 	if err != nil {
 		return nil, err
 	}
@@ -126,6 +132,14 @@ func ReadConfig(managementURL, adminURL, configPath string, preSharedKey *string
 		config.PreSharedKey = *preSharedKey
 		refresh = true
 	}
+	if config.SSHKey == "" {
+		pem, err := ssh.GeneratePrivateKey(ssh.ED25519)
+		if err != nil {
+			return nil, err
+		}
+		config.SSHKey = string(pem)
+		refresh = true
+	}
 
 	if refresh {
 		// since we have new management URL, we need to update config file

client/internal/connect.go

@@ -2,6 +2,7 @@ package internal
 
 import (
 	"context"
+	"github.com/netbirdio/netbird/client/ssh"
 	"time"
 
 	"github.com/netbirdio/netbird/client/system"
@@ -63,8 +64,13 @@ func RunClient(ctx context.Context, config *Config) error {
 		engineCtx, cancel := context.WithCancel(ctx)
 		defer cancel()
 
+		publicSSHKey, err := ssh.GeneratePublicKey([]byte(config.SSHKey))
+		if err != nil {
+			return err
+		}
 		// connect (just a connection, no stream yet) and login to Management Service to get an initial global Wiretrustee config
-		mgmClient, loginResp, err := connectToManagement(engineCtx, config.ManagementURL.Host, myPrivateKey, mgmTlsEnabled)
+		mgmClient, loginResp, err := connectToManagement(engineCtx, config.ManagementURL.Host, myPrivateKey, mgmTlsEnabled,
+			publicSSHKey)
 		if err != nil {
 			log.Debug(err)
 			if s, ok := status.FromError(err); ok && s.Code() == codes.PermissionDenied {
@@ -147,6 +153,7 @@ func createEngineConfig(key wgtypes.Key, config *Config, peerConfig *mgmProto.Pe
 		IFaceBlackList: config.IFaceBlackList,
 		WgPrivateKey:   key,
 		WgPort:         iface.DefaultWgPort,
+		SSHKey:         []byte(config.SSHKey),
 	}
 
 	if config.PreSharedKey != "" {
@@ -179,7 +186,7 @@ func connectToSignal(ctx context.Context, wtConfig *mgmProto.WiretrusteeConfig,
 }
 
 // connectToManagement creates Management Services client, establishes a connection, logs-in and gets a global Wiretrustee config (signal, turn, stun hosts, etc)
-func connectToManagement(ctx context.Context, managementAddr string, ourPrivateKey wgtypes.Key, tlsEnabled bool) (*mgm.GrpcClient, *mgmProto.LoginResponse, error) {
+func connectToManagement(ctx context.Context, managementAddr string, ourPrivateKey wgtypes.Key, tlsEnabled bool, pubSSHKey []byte) (*mgm.GrpcClient, *mgmProto.LoginResponse, error) {
 	log.Debugf("connecting to Management Service %s", managementAddr)
 	client, err := mgm.NewClient(ctx, managementAddr, ourPrivateKey, tlsEnabled)
 	if err != nil {
@@ -193,7 +200,7 @@ func connectToManagement(ctx context.Context, managementAddr string, ourPrivateK
 	}
 
 	sysInfo := system.GetInfo(ctx)
-	loginResp, err := client.Login(*serverPublicKey, sysInfo)
+	loginResp, err := client.Login(*serverPublicKey, sysInfo, pubSSHKey)
 	if err != nil {
 		return nil, nil, err
 	}

client/internal/engine.go

@@ -3,8 +3,10 @@ package internal
 import (
 	"context"
 	"fmt"
+	nbssh "github.com/netbirdio/netbird/client/ssh"
 	"math/rand"
 	"net"
+	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -54,6 +56,9 @@ type EngineConfig struct {
 
 	// UDPMuxSrflxPort default value 0 - the system will pick an available port
 	UDPMuxSrflxPort int
+
+	// SSHKey is a private SSH key in a PEM format
+	SSHKey []byte
 }
 
 // Engine is a mechanism responsible for reacting on Signal and Management stream events and managing connections to the remote peers.
@@ -87,6 +92,9 @@ type Engine struct {
 
 	// networkSerial is the latest CurrentSerial (state ID) of the network sent by the Management service
 	networkSerial uint64
+
+	sshServerFunc func(hostKeyPEM []byte, addr string) (nbssh.Server, error)
+	sshServer     nbssh.Server
 }
 
 // Peer is an instance of the Connection Peer
@@ -111,6 +119,7 @@ func NewEngine(
 		STUNs:         []*ice.URL{},
 		TURNs:         []*ice.URL{},
 		networkSerial: 0,
+		sshServerFunc: nbssh.DefaultSSHServer,
 	}
 }
 
@@ -283,9 +292,14 @@ func (e *Engine) removeAllPeers() error {
 	return nil
 }
 
-// removePeer closes an existing peer connection and removes a peer
+// removePeer closes an existing peer connection, removes a peer, and clears authorized key of the SSH server
 func (e *Engine) removePeer(peerKey string) error {
 	log.Debugf("removing peer from engine %s", peerKey)
+
+	if e.sshServer != nil {
+		e.sshServer.RemoveAuthorizedKey(peerKey)
+	}
+
 	conn, exists := e.peerConns[peerKey]
 	if exists {
 		delete(e.peerConns, peerKey)
@@ -398,12 +412,6 @@ func (e *Engine) handleSync(update *mgmProto.SyncResponse) error {
 	}
 
 	if update.GetNetworkMap() != nil {
-		if update.GetNetworkMap().GetPeerConfig() != nil {
-			err := e.updateConfig(update.GetNetworkMap().GetPeerConfig())
-			if err != nil {
-				return err
-			}
-		}
 		// only apply new changes and ignore old ones
 		err := e.updateNetworkMap(update.GetNetworkMap())
 		if err != nil {
@@ -414,6 +422,49 @@ func (e *Engine) handleSync(update *mgmProto.SyncResponse) error {
 	return nil
 }
 
+func (e *Engine) updateSSH(sshConf *mgmProto.SSHConfig) error {
+	if sshConf.GetSshEnabled() {
+		if runtime.GOOS == "windows" {
+			log.Warnf("running SSH server on Windows is not supported")
+			return nil
+		}
+		// start SSH server if it wasn't running
+		if e.sshServer == nil {
+			//nil sshServer means it has not yet been started
+			var err error
+			e.sshServer, err = e.sshServerFunc(e.config.SSHKey,
+				fmt.Sprintf("%s:%d", e.wgInterface.Address.IP.String(), nbssh.DefaultSSHPort))
+			if err != nil {
+				return err
+			}
+			go func() {
+				// blocking
+				err = e.sshServer.Start()
+				if err != nil {
+					// will throw error when we stop it even if it is a graceful stop
+					log.Debugf("stopped SSH server with error %v", err)
+				}
+				e.syncMsgMux.Lock()
+				defer e.syncMsgMux.Unlock()
+				e.sshServer = nil
+				log.Infof("stopped SSH server")
+			}()
+		} else {
+			log.Debugf("SSH server is already running")
+		}
+	} else {
+		// Disable SSH server request, so stop it if it was running
+		if e.sshServer != nil {
+			err := e.sshServer.Stop()
+			if err != nil {
+				log.Warnf("failed to stop SSH server %v", err)
+			}
+			e.sshServer = nil
+		}
+	}
+	return nil
+}
+
 func (e *Engine) updateConfig(conf *mgmProto.PeerConfig) error {
 	if e.wgInterface.Address.String() != conf.Address {
 		oldAddr := e.wgInterface.Address.String()
@@ -422,9 +473,17 @@ func (e *Engine) updateConfig(conf *mgmProto.PeerConfig) error {
 		if err != nil {
 			return err
 		}
+		e.config.WgAddr = conf.Address
 		log.Infof("updated peer address from %s to %s", oldAddr, conf.Address)
 	}
 
+	if conf.GetSshConfig() != nil {
+		err := e.updateSSH(conf.GetSshConfig())
+		if err != nil {
+			log.Warnf("failed handling SSH server setup %v", e)
+		}
+	}
+
 	return nil
 }
 
@@ -486,6 +545,15 @@ func (e *Engine) updateTURNs(turns []*mgmProto.ProtectedHostConfig) error {
 }
 
 func (e *Engine) updateNetworkMap(networkMap *mgmProto.NetworkMap) error {
+
+	// intentionally leave it before checking serial because for now it can happen that peer IP changed but serial didn't
+	if networkMap.GetPeerConfig() != nil {
+		err := e.updateConfig(networkMap.GetPeerConfig())
+		if err != nil {
+			return err
+		}
+	}
+
 	serial := networkMap.GetSerial()
 	if e.networkSerial > serial {
 		log.Debugf("received outdated NetworkMap with serial %d, ignoring", serial)
@@ -515,6 +583,18 @@ func (e *Engine) updateNetworkMap(networkMap *mgmProto.NetworkMap) error {
 		if err != nil {
 			return err
 		}
+
+		// update SSHServer by adding remote peer SSH keys
+		if e.sshServer != nil {
+			for _, config := range networkMap.GetRemotePeers() {
+				if config.GetSshConfig() != nil && config.GetSshConfig().GetSshPubKey() != nil {
+					err := e.sshServer.AddAuthorizedKey(config.WgPubKey, string(config.GetSshConfig().GetSshPubKey()))
+					if err != nil {
+						log.Warnf("failed adding authroized key to SSH DefaultServer %v", err)
+					}
+				}
+			}
+		}
 	}
 
 	e.networkSerial = serial

client/internal/engine_test.go

@@ -3,6 +3,9 @@ package internal
 import (
 	"context"
 	"fmt"
+	"github.com/netbirdio/netbird/client/ssh"
+	"github.com/netbirdio/netbird/iface"
+	"github.com/stretchr/testify/assert"
 	"net"
 	"os"
 	"path/filepath"
@@ -40,6 +43,140 @@ var (
 	}
 )
 
+func TestEngine_SSH(t *testing.T) {
+
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping TestEngine_SSH on Windows")
+	}
+
+	key, err := wgtypes.GeneratePrivateKey()
+	if err != nil {
+		t.Fatal(err)
+		return
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	engine := NewEngine(ctx, cancel, &signal.MockClient{}, &mgmt.MockClient{}, &EngineConfig{
+		WgIfaceName:  "utun101",
+		WgAddr:       "100.64.0.1/24",
+		WgPrivateKey: key,
+		WgPort:       33100,
+	})
+
+	var sshKeysAdded []string
+	var sshPeersRemoved []string
+
+	sshCtx, cancel := context.WithCancel(context.Background())
+
+	engine.sshServerFunc = func(hostKeyPEM []byte, addr string) (ssh.Server, error) {
+		return &ssh.MockServer{
+			Ctx: sshCtx,
+			StopFunc: func() error {
+				cancel()
+				return nil
+			},
+			StartFunc: func() error {
+				<-ctx.Done()
+				return ctx.Err()
+			},
+			AddAuthorizedKeyFunc: func(peer, newKey string) error {
+				sshKeysAdded = append(sshKeysAdded, newKey)
+				return nil
+			},
+			RemoveAuthorizedKeyFunc: func(peer string) {
+				sshPeersRemoved = append(sshPeersRemoved, peer)
+			},
+		}, nil
+	}
+	err = engine.Start()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer func() {
+		err := engine.Stop()
+		if err != nil {
+			return
+		}
+	}()
+
+	peerWithSSH := &mgmtProto.RemotePeerConfig{
+		WgPubKey:   "MNHf3Ma6z6mdLbriAJbqhX7+nM/B71lgw2+91q3LfhU=",
+		AllowedIps: []string{"100.64.0.21/24"},
+		SshConfig: &mgmtProto.SSHConfig{
+			SshPubKey: []byte("ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFATYCqaQw/9id1Qkq3n16JYhDhXraI6Pc1fgB8ynEfQ"),
+		},
+	}
+
+	// SSH server is not enabled so SSH config of a remote peer should be ignored
+	networkMap := &mgmtProto.NetworkMap{
+		Serial:             6,
+		PeerConfig:         nil,
+		RemotePeers:        []*mgmtProto.RemotePeerConfig{peerWithSSH},
+		RemotePeersIsEmpty: false,
+	}
+
+	err = engine.updateNetworkMap(networkMap)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Nil(t, engine.sshServer)
+
+	// SSH server is enabled, therefore SSH config should be applied
+	networkMap = &mgmtProto.NetworkMap{
+		Serial: 7,
+		PeerConfig: &mgmtProto.PeerConfig{Address: "100.64.0.1/24",
+			SshConfig: &mgmtProto.SSHConfig{SshEnabled: true}},
+		RemotePeers:        []*mgmtProto.RemotePeerConfig{peerWithSSH},
+		RemotePeersIsEmpty: false,
+	}
+
+	err = engine.updateNetworkMap(networkMap)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	time.Sleep(250 * time.Millisecond)
+	assert.NotNil(t, engine.sshServer)
+	assert.Contains(t, sshKeysAdded, "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFATYCqaQw/9id1Qkq3n16JYhDhXraI6Pc1fgB8ynEfQ")
+
+	// now remove peer
+	networkMap = &mgmtProto.NetworkMap{
+		Serial:             8,
+		RemotePeers:        []*mgmtProto.RemotePeerConfig{},
+		RemotePeersIsEmpty: false,
+	}
+
+	err = engine.updateNetworkMap(networkMap)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	//time.Sleep(250 * time.Millisecond)
+	assert.NotNil(t, engine.sshServer)
+	assert.Contains(t, sshPeersRemoved, "MNHf3Ma6z6mdLbriAJbqhX7+nM/B71lgw2+91q3LfhU=")
+
+	// now disable SSH server
+	networkMap = &mgmtProto.NetworkMap{
+		Serial: 9,
+		PeerConfig: &mgmtProto.PeerConfig{Address: "100.64.0.1/24",
+			SshConfig: &mgmtProto.SSHConfig{SshEnabled: false}},
+		RemotePeers:        []*mgmtProto.RemotePeerConfig{peerWithSSH},
+		RemotePeersIsEmpty: false,
+	}
+
+	err = engine.updateNetworkMap(networkMap)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Nil(t, engine.sshServer)
+
+}
+
 func TestEngine_UpdateNetworkMap(t *testing.T) {
 	// test setup
 	key, err := wgtypes.GeneratePrivateKey()
@@ -52,11 +189,12 @@ func TestEngine_UpdateNetworkMap(t *testing.T) {
 	defer cancel()
 
 	engine := NewEngine(ctx, cancel, &signal.MockClient{}, &mgmt.MockClient{}, &EngineConfig{
-		WgIfaceName:  "utun100",
+		WgIfaceName:  "utun102",
 		WgAddr:       "100.64.0.1/24",
 		WgPrivateKey: key,
 		WgPort:       33100,
 	})
+	engine.wgInterface, err = iface.NewWGIFace("utun102", "100.64.0.1/24", iface.DefaultMTU)
 
 	type testCase struct {
 		name       string
@@ -231,7 +369,7 @@ func TestEngine_Sync(t *testing.T) {
 	}
 
 	engine := NewEngine(ctx, cancel, &signal.MockClient{}, &mgmt.MockClient{SyncFunc: syncFunc}, &EngineConfig{
-		WgIfaceName:  "utun100",
+		WgIfaceName:  "utun103",
 		WgAddr:       "100.64.0.1/24",
 		WgPrivateKey: key,
 		WgPort:       33100,
@@ -418,7 +556,7 @@ func createEngine(ctx context.Context, cancel context.CancelFunc, setupKey strin
 	}
 
 	info := system.GetInfo(ctx)
-	resp, err := mgmtClient.Register(*publicKey, setupKey, "", info)
+	resp, err := mgmtClient.Register(*publicKey, setupKey, "", info, nil)
 	if err != nil {
 		return nil, err
 	}

client/internal/login.go

@@ -2,8 +2,8 @@ package internal
 
 import (
 	"context"
-
 	"github.com/google/uuid"
+	"github.com/netbirdio/netbird/client/ssh"
 	"github.com/netbirdio/netbird/client/system"
 	mgm "github.com/netbirdio/netbird/management/client"
 	mgmProto "github.com/netbirdio/netbird/management/proto"
@@ -40,7 +40,11 @@ func Login(ctx context.Context, config *Config, setupKey string, jwtToken string
 		return err
 	}
 
-	_, err = loginPeer(ctx, *serverKey, mgmClient, setupKey, jwtToken)
+	pubSSHKey, err := ssh.GeneratePublicKey([]byte(config.SSHKey))
+	if err != nil {
+		return err
+	}
+	_, err = loginPeer(ctx, *serverKey, mgmClient, setupKey, jwtToken, pubSSHKey)
 	if err != nil {
 		log.Errorf("failed logging-in peer on Management Service : %v", err)
 		return err
@@ -56,13 +60,13 @@ func Login(ctx context.Context, config *Config, setupKey string, jwtToken string
 }
 
 // loginPeer attempts to login to Management Service. If peer wasn't registered, tries the registration flow.
-func loginPeer(ctx context.Context, serverPublicKey wgtypes.Key, client *mgm.GrpcClient, setupKey string, jwtToken string) (*mgmProto.LoginResponse, error) {
+func loginPeer(ctx context.Context, serverPublicKey wgtypes.Key, client *mgm.GrpcClient, setupKey string, jwtToken string, pubSSHKey []byte) (*mgmProto.LoginResponse, error) {
 	sysInfo := system.GetInfo(ctx)
-	loginResp, err := client.Login(serverPublicKey, sysInfo)
+	loginResp, err := client.Login(serverPublicKey, sysInfo, pubSSHKey)
 	if err != nil {
 		if s, ok := status.FromError(err); ok && s.Code() == codes.PermissionDenied {
 			log.Debugf("peer registration required")
-			return registerPeer(ctx, serverPublicKey, client, setupKey, jwtToken)
+			return registerPeer(ctx, serverPublicKey, client, setupKey, jwtToken, pubSSHKey)
 		} else {
 			return nil, err
 		}
@@ -75,7 +79,7 @@ func loginPeer(ctx context.Context, serverPublicKey wgtypes.Key, client *mgm.Grp
 
 // registerPeer checks whether setupKey was provided via cmd line and if not then it prompts user to enter a key.
 // Otherwise tries to register with the provided setupKey via command line.
-func registerPeer(ctx context.Context, serverPublicKey wgtypes.Key, client *mgm.GrpcClient, setupKey string, jwtToken string) (*mgmProto.LoginResponse, error) {
+func registerPeer(ctx context.Context, serverPublicKey wgtypes.Key, client *mgm.GrpcClient, setupKey string, jwtToken string, pubSSHKey []byte) (*mgmProto.LoginResponse, error) {
 	validSetupKey, err := uuid.Parse(setupKey)
 	if err != nil && jwtToken == "" {
 		return nil, status.Errorf(codes.InvalidArgument, "invalid setup-key or no sso information provided, err: %v", err)
@@ -83,7 +87,7 @@ func registerPeer(ctx context.Context, serverPublicKey wgtypes.Key, client *mgm.
 
 	log.Debugf("sending peer registration request to Management Service")
 	info := system.GetInfo(ctx)
-	loginResp, err := client.Register(serverPublicKey, validSetupKey.String(), jwtToken, info)
+	loginResp, err := client.Register(serverPublicKey, validSetupKey.String(), jwtToken, info, pubSSHKey)
 	if err != nil {
 		log.Errorf("failed registering peer %v,%s", err, validSetupKey.String())
 		return nil, err

client/ssh/client.go

@@ -0,0 +1,114 @@
+package ssh
+
+import (
+	"fmt"
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/term"
+	"net"
+	"os"
+)
+
+// Client wraps crypto/ssh Client to simplify usage
+type Client struct {
+	client *ssh.Client
+}
+
+// Close closes the wrapped SSH Client
+func (c *Client) Close() error {
+	return c.client.Close()
+}
+
+// OpenTerminal starts an interactive terminal session with the remote SSH server
+func (c *Client) OpenTerminal() error {
+	session, err := c.client.NewSession()
+	if err != nil {
+		return fmt.Errorf("failed to open new session: %v", err)
+	}
+	defer func() {
+		err := session.Close()
+		if err != nil {
+			return
+		}
+	}()
+
+	fd := int(os.Stdout.Fd())
+	state, err := term.MakeRaw(fd)
+	if err != nil {
+		return fmt.Errorf("failed to run raw terminal: %s", err)
+	}
+	defer func() {
+		err := term.Restore(fd, state)
+		if err != nil {
+			return
+		}
+	}()
+
+	w, h, err := term.GetSize(fd)
+	if err != nil {
+		return fmt.Errorf("terminal get size: %s", err)
+	}
+
+	modes := ssh.TerminalModes{
+		ssh.ECHO:          1,
+		ssh.TTY_OP_ISPEED: 14400,
+		ssh.TTY_OP_OSPEED: 14400,
+	}
+
+	terminal := os.Getenv("TERM")
+	if terminal == "" {
+		terminal = "xterm-256color"
+	}
+	if err := session.RequestPty(terminal, h, w, modes); err != nil {
+		return fmt.Errorf("failed requesting pty session with xterm: %s", err)
+	}
+
+	session.Stdout = os.Stdout
+	session.Stderr = os.Stderr
+	session.Stdin = os.Stdin
+
+	if err := session.Shell(); err != nil {
+		return fmt.Errorf("failed to start login shell on the remote host: %s", err)
+	}
+
+	if err := session.Wait(); err != nil {
+		if e, ok := err.(*ssh.ExitError); ok {
+			switch e.ExitStatus() {
+			case 130:
+				return nil
+			}
+		}
+		return fmt.Errorf("failed running SSH session: %s", err)
+	}
+
+	return nil
+}
+
+// DialWithKey connects to the remote SSH server with a provided private key file (PEM).
+func DialWithKey(addr, user string, privateKey []byte) (*Client, error) {
+
+	signer, err := ssh.ParsePrivateKey(privateKey)
+	if err != nil {
+		return nil, err
+	}
+
+	config := &ssh.ClientConfig{
+		User: user,
+		Auth: []ssh.AuthMethod{
+			ssh.PublicKeys(signer),
+		},
+		HostKeyCallback: ssh.HostKeyCallback(func(hostname string, remote net.Addr, key ssh.PublicKey) error { return nil }),
+	}
+
+	return Dial("tcp", addr, config)
+}
+
+// Dial connects to the remote SSH server.
+func Dial(network, addr string, config *ssh.ClientConfig) (*Client, error) {
+	client, err := ssh.Dial(network, addr, config)
+	if err != nil {
+		return nil, err
+	}
+	return &Client{
+		client: client,
+	}, nil
+}

client/ssh/server.go

@@ -0,0 +1,183 @@
+package ssh
+
+import (
+	"fmt"
+	"github.com/creack/pty"
+	"github.com/gliderlabs/ssh"
+	log "github.com/sirupsen/logrus"
+	"io"
+	"net"
+	"os"
+	"os/exec"
+	"sync"
+)
+
+// DefaultSSHPort is the default SSH port of the NetBird's embedded SSH server
+const DefaultSSHPort = 44338
+
+// DefaultSSHServer is a function that creates DefaultServer
+func DefaultSSHServer(hostKeyPEM []byte, addr string) (Server, error) {
+	return newDefaultServer(hostKeyPEM, addr)
+}
+
+// Server is an interface of SSH server
+type Server interface {
+	// Stop stops SSH server.
+	Stop() error
+	// Start starts SSH server. Blocking
+	Start() error
+	// RemoveAuthorizedKey removes SSH key of a given peer from the authorized keys
+	RemoveAuthorizedKey(peer string)
+	// AddAuthorizedKey add a given peer key to server authorized keys
+	AddAuthorizedKey(peer, newKey string) error
+}
+
+// DefaultServer is the embedded NetBird SSH server
+type DefaultServer struct {
+	listener net.Listener
+	// authorizedKeys is ssh pub key indexed by peer WireGuard public key
+	authorizedKeys map[string]ssh.PublicKey
+	mu             sync.Mutex
+	hostKeyPEM     []byte
+	sessions       []ssh.Session
+}
+
+// newDefaultServer creates new server with provided host key
+func newDefaultServer(hostKeyPEM []byte, addr string) (*DefaultServer, error) {
+	ln, err := net.Listen("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	allowedKeys := make(map[string]ssh.PublicKey)
+	return &DefaultServer{listener: ln, mu: sync.Mutex{}, hostKeyPEM: hostKeyPEM, authorizedKeys: allowedKeys, sessions: make([]ssh.Session, 0)}, nil
+}
+
+// RemoveAuthorizedKey removes SSH key of a given peer from the authorized keys
+func (srv *DefaultServer) RemoveAuthorizedKey(peer string) {
+	srv.mu.Lock()
+	defer srv.mu.Unlock()
+
+	delete(srv.authorizedKeys, peer)
+}
+
+// AddAuthorizedKey add a given peer key to server authorized keys
+func (srv *DefaultServer) AddAuthorizedKey(peer, newKey string) error {
+	srv.mu.Lock()
+	defer srv.mu.Unlock()
+
+	parsedKey, _, _, _, err := ssh.ParseAuthorizedKey([]byte(newKey))
+	if err != nil {
+		return err
+	}
+
+	srv.authorizedKeys[peer] = parsedKey
+	return nil
+}
+
+// Stop stops SSH server.
+func (srv *DefaultServer) Stop() error {
+	srv.mu.Lock()
+	defer srv.mu.Unlock()
+	err := srv.listener.Close()
+	if err != nil {
+		return err
+	}
+	for _, session := range srv.sessions {
+		err := session.Close()
+		if err != nil {
+			log.Warnf("failed closing SSH session from %v", err)
+		}
+	}
+
+	return nil
+}
+
+func (srv *DefaultServer) publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
+	srv.mu.Lock()
+	defer srv.mu.Unlock()
+
+	for _, allowed := range srv.authorizedKeys {
+		if ssh.KeysEqual(allowed, key) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func getShellType() string {
+	shell := os.Getenv("SHELL")
+	if shell == "" {
+		shell = "sh"
+	}
+	return shell
+}
+
+// sessionHandler handles SSH session post auth
+func (srv *DefaultServer) sessionHandler(session ssh.Session) {
+	srv.mu.Lock()
+	srv.sessions = append(srv.sessions, session)
+	srv.mu.Unlock()
+	ptyReq, winCh, isPty := session.Pty()
+	if isPty {
+		cmd := exec.Command(getShellType())
+		cmd.Env = append(cmd.Env, fmt.Sprintf("TERM=%session", ptyReq.Term))
+		file, err := pty.Start(cmd)
+		if err != nil {
+			log.Errorf("failed starting SSH server %v", err)
+		}
+		go func() {
+			for win := range winCh {
+				setWinSize(file, win.Width, win.Height)
+			}
+		}()
+
+		srv.stdInOut(file, session)
+
+		err = cmd.Wait()
+		if err != nil {
+			return
+		}
+	} else {
+		_, err := io.WriteString(session, "only PTY is supported.\n")
+		if err != nil {
+			return
+		}
+		err = session.Exit(1)
+		if err != nil {
+			return
+		}
+	}
+}
+
+func (srv *DefaultServer) stdInOut(file *os.File, session ssh.Session) {
+	go func() {
+		// stdin
+		_, err := io.Copy(file, session)
+		if err != nil {
+			return
+		}
+	}()
+
+	go func() {
+		// stdout
+		_, err := io.Copy(session, file)
+		if err != nil {
+			return
+		}
+	}()
+}
+
+// Start starts SSH server. Blocking
+func (srv *DefaultServer) Start() error {
+	log.Infof("starting SSH server on addr: %s", srv.listener.Addr().String())
+
+	publicKeyOption := ssh.PublicKeyAuth(srv.publicKeyHandler)
+	hostKeyPEM := ssh.HostKeyPEM(srv.hostKeyPEM)
+	err := ssh.Serve(srv.listener, srv.sessionHandler, publicKeyOption, hostKeyPEM)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

client/ssh/server_mock.go

@@ -0,0 +1,44 @@
+package ssh
+
+import "context"
+
+// MockServer mocks ssh.Server
+type MockServer struct {
+	Ctx                     context.Context
+	StopFunc                func() error
+	StartFunc               func() error
+	AddAuthorizedKeyFunc    func(peer, newKey string) error
+	RemoveAuthorizedKeyFunc func(peer string)
+}
+
+// RemoveAuthorizedKey removes SSH key of a given peer from the authorized keys
+func (srv *MockServer) RemoveAuthorizedKey(peer string) {
+	if srv.RemoveAuthorizedKeyFunc == nil {
+		return
+	}
+	srv.RemoveAuthorizedKeyFunc(peer)
+}
+
+// AddAuthorizedKey add a given peer key to server authorized keys
+func (srv *MockServer) AddAuthorizedKey(peer, newKey string) error {
+	if srv.AddAuthorizedKeyFunc == nil {
+		return nil
+	}
+	return srv.AddAuthorizedKeyFunc(peer, newKey)
+}
+
+// Stop stops SSH server.
+func (srv *MockServer) Stop() error {
+	if srv.StopFunc == nil {
+		return nil
+	}
+	return srv.StopFunc()
+}
+
+// Start starts SSH server. Blocking
+func (srv *MockServer) Start() error {
+	if srv.StartFunc == nil {
+		return nil
+	}
+	return srv.StartFunc()
+}

client/ssh/server_test.go

@@ -0,0 +1,121 @@
+package ssh
+
+import (
+	"fmt"
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/crypto/ssh"
+	"strings"
+	"testing"
+)
+
+func TestServer_AddAuthorizedKey(t *testing.T) {
+	key, err := GeneratePrivateKey(ED25519)
+	if err != nil {
+		t.Fatal(err)
+	}
+	server, err := newDefaultServer(key, "localhost:")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// add multiple keys
+	keys := map[string][]byte{}
+	for i := 0; i < 10; i++ {
+		peer := fmt.Sprintf("%s-%d", "remotePeer", i)
+		remotePrivKey, err := GeneratePrivateKey(ED25519)
+		if err != nil {
+			t.Fatal(err)
+		}
+		remotePubKey, err := GeneratePublicKey(remotePrivKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		err = server.AddAuthorizedKey(peer, string(remotePubKey))
+		if err != nil {
+			t.Error(err)
+		}
+		keys[peer] = remotePubKey
+	}
+
+	// make sure that all keys have been added
+	for peer, remotePubKey := range keys {
+		k, ok := server.authorizedKeys[peer]
+		assert.True(t, ok, "expecting remotePeer key to be found in authorizedKeys")
+
+		assert.Equal(t, string(remotePubKey), strings.TrimSpace(string(ssh.MarshalAuthorizedKey(k))))
+	}
+
+}
+
+func TestServer_RemoveAuthorizedKey(t *testing.T) {
+	key, err := GeneratePrivateKey(ED25519)
+	if err != nil {
+		t.Fatal(err)
+	}
+	server, err := newDefaultServer(key, "localhost:")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	remotePrivKey, err := GeneratePrivateKey(ED25519)
+	if err != nil {
+		t.Fatal(err)
+	}
+	remotePubKey, err := GeneratePublicKey(remotePrivKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = server.AddAuthorizedKey("remotePeer", string(remotePubKey))
+	if err != nil {
+		t.Error(err)
+	}
+
+	server.RemoveAuthorizedKey("remotePeer")
+
+	_, ok := server.authorizedKeys["remotePeer"]
+	assert.False(t, ok, "expecting remotePeer's SSH key to be removed")
+}
+
+func TestServer_PubKeyHandler(t *testing.T) {
+	key, err := GeneratePrivateKey(ED25519)
+	if err != nil {
+		t.Fatal(err)
+	}
+	server, err := newDefaultServer(key, "localhost:")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var keys []ssh.PublicKey
+	for i := 0; i < 10; i++ {
+		peer := fmt.Sprintf("%s-%d", "remotePeer", i)
+		remotePrivKey, err := GeneratePrivateKey(ED25519)
+		if err != nil {
+			t.Fatal(err)
+		}
+		remotePubKey, err := GeneratePublicKey(remotePrivKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		remoteParsedPubKey, _, _, _, err := ssh.ParseAuthorizedKey(remotePubKey)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		err = server.AddAuthorizedKey(peer, string(remotePubKey))
+		if err != nil {
+			t.Error(err)
+		}
+		keys = append(keys, remoteParsedPubKey)
+	}
+
+	for _, key := range keys {
+		accepted := server.publicKeyHandler(nil, key)
+
+		assert.Truef(t, accepted, "expecting SSH connection to be accepted for a given SSH key %s", string(ssh.MarshalAuthorizedKey(key)))
+	}
+
+}

client/ssh/util.go

@@ -0,0 +1,86 @@
+package ssh
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"golang.org/x/crypto/ed25519"
+	gossh "golang.org/x/crypto/ssh"
+	"strings"
+)
+
+// KeyType is a type of SSH key
+type KeyType string
+
+// ED25519 is key of type ed25519
+const ED25519 KeyType = "ed25519"
+
+// ECDSA is key of type ecdsa
+const ECDSA KeyType = "ecdsa"
+
+// RSA is key of type rsa
+const RSA KeyType = "rsa"
+
+// RSAKeySize is a size of newly generated RSA key
+const RSAKeySize = 2048
+
+// GeneratePrivateKey creates RSA Private Key of specified byte size
+func GeneratePrivateKey(keyType KeyType) ([]byte, error) {
+
+	var key crypto.Signer
+	var err error
+	switch keyType {
+	case ED25519:
+		_, key, err = ed25519.GenerateKey(rand.Reader)
+	case ECDSA:
+		key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	case RSA:
+		key, err = rsa.GenerateKey(rand.Reader, RSAKeySize)
+	default:
+		return nil, fmt.Errorf("unsupported ket type %s", keyType)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	pemBytes, err := EncodePrivateKeyToPEM(key)
+	if err != nil {
+		return nil, err
+	}
+
+	return pemBytes, nil
+}
+
+// GeneratePublicKey returns the public part of the private key
+func GeneratePublicKey(key []byte) ([]byte, error) {
+	signer, err := gossh.ParsePrivateKey(key)
+	if err != nil {
+		return nil, err
+	}
+
+	strKey := strings.TrimSpace(string(gossh.MarshalAuthorizedKey(signer.PublicKey())))
+	return []byte(strKey), nil
+}
+
+// EncodePrivateKeyToPEM encodes Private Key from RSA to PEM format
+func EncodePrivateKeyToPEM(privateKey crypto.Signer) ([]byte, error) {
+	mk, err := x509.MarshalPKCS8PrivateKey(privateKey)
+	if err != nil {
+		return nil, err
+	}
+
+	// pem.Block
+	privBlock := pem.Block{
+		Type:  "PRIVATE KEY",
+		Bytes: mk,
+	}
+
+	// Private key in PEM format
+	privatePEM := pem.EncodeToMemory(&privBlock)
+	return privatePEM, nil
+}

client/ssh/window_unix.go

@@ -0,0 +1,14 @@
+//go:build linux || darwin
+
+package ssh
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+func setWinSize(file *os.File, width, height int) {
+	syscall.Syscall(syscall.SYS_IOCTL, file.Fd(), uintptr(syscall.TIOCSWINSZ), //nolint
+		uintptr(unsafe.Pointer(&struct{ h, w, x, y uint16 }{uint16(height), uint16(width), 0, 0})))
+}

client/ssh/window_windows.go

@@ -0,0 +1,9 @@
+package ssh
+
+import (
+	"os"
+)
+
+func setWinSize(file *os.File, width, height int) {
+
+}