threshold/internal/cmd/commands/proxy/proxy.go

package proxy

import (
	"context"
	"crypto/ed25519"
	"crypto/tls"
	"crypto/x509"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/btcsuite/btcutil/base58"
	"github.com/hashicorp/boundary/api/targets"
	"github.com/hashicorp/boundary/globals"
	"github.com/hashicorp/boundary/internal/cmd/base"
	targetspb "github.com/hashicorp/boundary/internal/gen/controller/api/resources/targets"
	"github.com/hashicorp/boundary/internal/proxy"
	"github.com/hashicorp/go-cleanhttp"
	"github.com/hashicorp/vault/sdk/helper/base62"
	"github.com/kr/pretty"
	"github.com/mitchellh/cli"
	"github.com/posener/complete"
	"go.uber.org/atomic"
	"google.golang.org/protobuf/proto"
	"nhooyr.io/websocket"
	"nhooyr.io/websocket/wspb"
)

type SessionInfo struct {
	Address         string    `json:"address"`
	Port            int       `json:"port"`
	Protocol        string    `json:"protocol"`
	Expiration      time.Time `json:"expiration"`
	ConnectionLimit int32     `json:"connection_limit"`
	SessionId       string    `json:"session_id"`
}

type ConnectionInfo struct {
	ConnectionsLeft int32 `json:"connections_left"`
}

type TerminationInfo struct {
	Reason string `json:"termination_reason"`
}

var _ cli.Command = (*Command)(nil)
var _ cli.CommandAutocomplete = (*Command)(nil)

type Command struct {
	*base.Command

	flagAuthz      string
	flagListenAddr string
	flagListenPort int
	flagVerbose    bool
	flagTargetId   string
	flagHostId     string

	Func string

	connWg            *sync.WaitGroup
	listenerCloseOnce sync.Once
	listener          *net.TCPListener
	connsLeftCh       chan int32
	connectionsLeft   atomic.Int32
	expiration        time.Time
}

func (c *Command) Synopsis() string {
	switch c.Func {
	case "proxy":
		return "Launch the Boundary CLI in proxy mode"
	case "connect":
		return "Authorize a session against a target and launch a proxied connection"
	}
	return ""
}

func (c *Command) Help() string {
	switch c.Func {
	case "proxy":
		return base.WrapForHelpText([]string{
			"Usage: boundary proxy [options] [args]",
			"",
			"  This command allows launching the Boundary CLI in proxy mode. In this mode, the CLI expects to take in an authorization string returned from a Boundary controller. The CLI will then create a connection to a Boundary worker and ready a listening port for a local connection.",
			"",
			"  Example:",
			"",
			`      $ boundary proxy -auth "UgxzX29mVEpwNUt6QlGiAQ..."`,
		}) + c.Flags().Help()

	case "connect":
		return base.WrapForHelpText([]string{
			"Usage: boundary connect [options] [args]",
			"",
			`  This command performs a target authorization and proxy launch in one command; it is equivalent to sending the output of "boundary targets authorize" into "boundary proxy". See the help output for those commands for more information.`,
			"",
			"  Example:",
			"",
			`      $ boundary connect -target-id ttcp_1234567890"`,
		}) + c.Flags().Help()
	}
	return ""
}

func (c *Command) Flags() *base.FlagSets {
	bits := base.FlagSetOutputFormat
	if c.Func == "connect" {
		bits = base.FlagSetHTTP | base.FlagSetClient | bits
	}
	set := c.FlagSet(bits)

	f := set.NewFlagSet("Proxy Options")

	switch c.Func {
	case "proxy":
		f.StringVar(&base.StringVar{
			Name:       "authz",
			Target:     &c.flagAuthz,
			EnvVar:     "BOUNDARY_PROXY_AUTHZ",
			Completion: complete.PredictAnything,
			Usage:      `The authorization string returned from the Boundary controller. If set to "-", the command will attempt to read in the authorization string from standard input.`,
		})
	case "connect":
		f.StringVar(&base.StringVar{
			Name:   "target-id",
			Target: &c.flagTargetId,
			Usage:  "The ID of the target to authorize against.",
		})
		f.StringVar(&base.StringVar{
			Name:   "host-id",
			Target: &c.flagHostId,
			Usage:  "The ID of a specific host to connect to out of the hosts from the target's host sets. If not specified, one is chosen at random.",
		})
	}

	f.StringVar(&base.StringVar{
		Name:       "listen-addr",
		Target:     &c.flagListenAddr,
		EnvVar:     "BOUNDARY_PROXY_LISTEN_ADDR",
		Completion: complete.PredictAnything,
		Usage:      `If set, the CLI will attempt to bind its listening address to the given value, which must be an IP address. If it cannot, the command will error. If not set, defaults to the most common IPv4 loopback address (127.0.0.1)."`,
	})

	f.IntVar(&base.IntVar{
		Name:       "listen-port",
		Target:     &c.flagListenPort,
		EnvVar:     "BOUNDARY_PROXY_LISTEN_PORT",
		Completion: complete.PredictAnything,
		Usage:      `If set, the CLI will attempt to bind its listening port to the given value. If it cannot, the command will error."`,
	})

	f.BoolVar(&base.BoolVar{
		Name:       "verbose",
		Target:     &c.flagVerbose,
		Completion: complete.PredictAnything,
		Usage:      "Turns on some extra verbosity in the command output.",
	})

	return set
}

func (c *Command) AutocompleteArgs() complete.Predictor {
	return complete.PredictAnything
}

func (c *Command) AutocompleteFlags() complete.Flags {
	return c.Flags().Completions()
}

func (c *Command) Run(args []string) (retCode int) {
	f := c.Flags()

	if err := f.Parse(args); err != nil {
		c.UI.Error(err.Error())
		return 1
	}

	tofuToken, err := base62.Random(20)
	if err != nil {
		c.UI.Error(fmt.Errorf("Could not derive random bytes for tofu token: %w", err).Error())
		return 1
	}

	c.connsLeftCh = make(chan int32)

	if c.flagListenAddr == "" {
		c.flagListenAddr = "127.0.0.1"
	}
	listenAddr := net.ParseIP(c.flagListenAddr)
	if listenAddr == nil {
		c.UI.Error(fmt.Sprintf("Could not successfully parse listen address of %s", c.flagListenAddr))
		return 1
	}

	authzString := c.flagAuthz
	switch c.Func {
	case "proxy":
		if authzString == "-" {
			authBytes, err := ioutil.ReadAll(os.Stdin)
			if err != nil {
				c.UI.Error(fmt.Errorf("No authorization string was provided and encountered the following error attempting to read it from stdin: %w", err).Error())
				return 1
			}
			if len(authBytes) == 0 {
				c.UI.Error("No authorization data read from stdin")
				return 1
			}
			authzString = string(authBytes)
		}

		if authzString == "" {
			c.UI.Error("Authorization data was empty")
			return 1
		}

		if authzString[0] == '{' {
			// Attempt to decode the JSON output of an authorize call and pull the
			// token out of there
			var sa targets.SessionAuthorization
			if err := json.Unmarshal([]byte(authzString), &sa); err == nil {
				authzString = sa.AuthorizationToken
			}
		}

	case "connect":
		if c.flagTargetId == "" {
			c.UI.Error("Target ID must be provided")
			return 1
		}

		client, err := c.Client()
		if err != nil {
			c.UI.Error(fmt.Sprintf("Error creating API client: %s", err.Error()))
			return 2
		}
		targetClient := targets.NewClient(client)

		var opts []targets.Option
		if len(c.flagHostId) != 0 {
			opts = append(opts, targets.WithHostId(c.flagHostId))
		}

		sar, apiErr, err := targetClient.Authorize(c.Context, c.flagTargetId, opts...)
		if err != nil {
			c.UI.Error(fmt.Sprintf("Error trying to authorize a session against target: %s", err.Error()))
			return 2
		}
		if apiErr != nil {
			c.UI.Error(fmt.Sprintf("Error from controller when performing authorize on a session against target: %s", pretty.Sprint(apiErr)))
			return 1
		}
		sa := sar.GetItem().(*targets.SessionAuthorization)
		authzString = sa.AuthorizationToken
	}

	marshaled := base58.Decode(authzString)
	if len(marshaled) == 0 {
		c.UI.Error("Zero length authorization information after decoding")
		return 1
	}

	data := new(targetspb.SessionAuthorizationData)
	if err := proto.Unmarshal(marshaled, data); err != nil {
		c.UI.Error(fmt.Errorf("Unable to proto-decode authorization data: %w", err).Error())
		return 1
	}

	if len(data.GetWorkerInfo()) == 0 {
		c.UI.Error("No workers found in authorization string")
		return 1
	}

	c.connectionsLeft.Store(data.ConnectionLimit)
	workerAddr := data.GetWorkerInfo()[0].GetAddress()

	parsedCert, err := x509.ParseCertificate(data.Certificate)
	if err != nil {
		c.UI.Error(fmt.Errorf("Unable to decode mTLS certificate: %w", err).Error())
		return 1
	}

	if len(parsedCert.DNSNames) != 1 {
		c.UI.Error(fmt.Errorf("mTLS certificate has invalid parameters: %w", err).Error())
		return 1
	}

	c.expiration = parsedCert.NotAfter

	certPool := x509.NewCertPool()
	certPool.AddCert(parsedCert)

	tlsConf := &tls.Config{
		Certificates: []tls.Certificate{
			{
				Certificate: [][]byte{data.Certificate},
				PrivateKey:  ed25519.PrivateKey(data.PrivateKey),
				Leaf:        parsedCert,
			},
		},
		RootCAs:    certPool,
		ServerName: parsedCert.DNSNames[0],
		MinVersion: tls.VersionTLS13,
	}

	transport := cleanhttp.DefaultTransport()
	transport.DisableKeepAlives = false
	transport.TLSClientConfig = tlsConf
	// This isn't/shouldn't used anyways really because the connection is
	// hijacked, just setting for completeness
	transport.IdleConnTimeout = 0

	c.listener, err = net.ListenTCP("tcp", &net.TCPAddr{
		IP:   listenAddr,
		Port: c.flagListenPort,
	})
	if err != nil {
		c.UI.Error(fmt.Errorf("Error starting listening port: %w", err).Error())
		return 1
	}

	listenerCloseFunc := func() {
		// Forces the for loop to exist instead of spinning on errors
		c.connectionsLeft.Store(0)
		if err := c.listener.Close(); err != nil {
			c.UI.Error(fmt.Errorf("Error closing listener on shutdown: %w", err).Error())
			retCode = 1
		}
	}

	// Ensure it runs on any other return condition
	defer func() {
		c.listenerCloseOnce.Do(listenerCloseFunc)
	}()

	listenerAddr := c.listener.Addr().(*net.TCPAddr)

	sessInfo := SessionInfo{
		Protocol:        "tcp",
		Address:         listenerAddr.IP.String(),
		Port:            listenerAddr.Port,
		Expiration:      c.expiration,
		ConnectionLimit: data.GetConnectionLimit(),
		SessionId:       data.GetSessionId(),
	}

	switch base.Format(c.UI) {
	case "table":
		c.UI.Output(generateSessionInfoTableOutput(sessInfo))
	case "json":
		out, err := json.Marshal(&sessInfo)
		if err != nil {
			c.UI.Error(fmt.Errorf("error marshaling session information: %w", err).Error())
			return 1
		}
		c.UI.Output(string(out))
	}

	c.connWg = new(sync.WaitGroup)

	c.connWg.Add(1)
	go func() {
		defer c.connWg.Done()
		for {
			listeningConn, err := c.listener.AcceptTCP()
			if err != nil {
				select {
				case <-c.Context.Done():
					return
				default:
					// When this hits zero we tigger listener close so this
					// isn't actually an error condition
					if c.connectionsLeft.Load() == 0 {
						return
					}
					c.UI.Error(fmt.Errorf("Error accepting connection: %w", err).Error())
					continue
				}
			}
			c.connWg.Add(1)
			go func() {
				defer listeningConn.Close()
				if err := c.handleConnection(
					listeningConn,
					workerAddr,
					tofuToken,
					transport); err != nil {
					c.UI.Error(err.Error())
				}
			}()
		}
	}()

	timer := time.NewTimer(time.Until(c.expiration))
	var termInfo TerminationInfo
Wait:
	for {
		select {
		case <-c.Context.Done():
			termInfo.Reason = "Received shutdown signal"
			timer.Stop()
			break Wait
		case <-timer.C:
			termInfo.Reason = "Session has expired"
			break Wait
		case connsLeft := <-c.connsLeftCh:
			c.updateConnsLeft(connsLeft)
			if connsLeft == 0 {
				termInfo.Reason = "No connections left in session"
				break Wait
			}
		}
	}
	c.listenerCloseOnce.Do(listenerCloseFunc)

	c.connWg.Wait()

	switch base.Format(c.UI) {
	case "table":
		c.UI.Output(generateTerminationInfoTableOutput(termInfo))
	case "json":
		out, err := json.Marshal(&termInfo)
		if err != nil {
			c.UI.Error(fmt.Errorf("error marshaling termination information: %w", err).Error())
			return 1
		}
		c.UI.Output(string(out))
	}

	return 0
}

func (c *Command) handleConnection(
	listeningConn *net.TCPConn,
	workerAddr string,
	tofuToken string,
	transport *http.Transport) error {

	defer c.connWg.Done()

	conn, resp, err := websocket.Dial(
		c.Context,
		fmt.Sprintf("wss://%s/v1/proxy", workerAddr),
		&websocket.DialOptions{
			HTTPClient: &http.Client{
				Transport: transport,
			},
			Subprotocols: []string{globals.TcpProxyV1},
		},
	)
	if err != nil {
		switch {
		case strings.Contains(err.Error(), "tls: internal error"):
			return errors.New("Session is unauthorized")
		case strings.Contains(err.Error(), "connect: connection refused"):
			return fmt.Errorf("Unable to connect to worker at %s", workerAddr)
		default:
			return fmt.Errorf("Error dialing the worker: %w", err)
		}
	}

	if resp == nil {
		return errors.New("Response from worker is nil")
	}
	if resp.Header == nil {
		return errors.New("Response header is nil")
	}
	negProto := resp.Header.Get("Sec-WebSocket-Protocol")
	if negProto != globals.TcpProxyV1 {
		return fmt.Errorf("Unexpected negotiated protocol: %s", negProto)
	}

	handshake := proxy.ClientHandshake{TofuToken: tofuToken}
	if err := wspb.Write(c.Context, conn, &handshake); err != nil {
		return fmt.Errorf("error sending handshake to worker: %w", err)
	}
	var handshakeResult proxy.HandshakeResult
	if err := wspb.Read(c.Context, conn, &handshakeResult); err != nil {
		switch {
		case strings.Contains(err.Error(), "unable to authorize connection"):
			// There's no reason to think we'd be able to authorize any more
			// connections after the first has failed
			c.connsLeftCh <- 0
			return errors.New("Unable to authorize connection")
		}
		return fmt.Errorf("error reading handshake result: %w", err)
	}

	if handshakeResult.GetConnectionsLeft() != -1 {
		c.connsLeftCh <- handshakeResult.GetConnectionsLeft()
	}

	// We don't _rely_ on client-side timeout verification but this prevents us
	// seeming to be ready for a connection that will immediately fail when we
	// try to actually make it
	expiringCtx, cancel := context.WithDeadline(c.Context, handshakeResult.GetExpiration().AsTime())
	defer cancel()

	// Get a wrapped net.Conn so we can use io.Copy
	netConn := websocket.NetConn(expiringCtx, conn, websocket.MessageBinary)

	localWg := new(sync.WaitGroup)
	localWg.Add(2)

	go func() {
		defer localWg.Done()
		io.Copy(netConn, listeningConn)
		netConn.Close()
		listeningConn.Close()
	}()
	go func() {
		defer localWg.Done()
		io.Copy(listeningConn, netConn)
		listeningConn.Close()
		netConn.Close()
	}()
	localWg.Wait()

	return nil
}

func (c *Command) updateConnsLeft(connsLeft int32) {
	c.connectionsLeft.Store(connsLeft)

	connInfo := ConnectionInfo{
		ConnectionsLeft: connsLeft,
	}

	switch base.Format(c.UI) {
	case "table":
		c.UI.Output(generateConnectionInfoTableOutput(connInfo))
	case "json":
		out, err := json.Marshal(&connInfo)
		if err != nil {
			c.UI.Error(fmt.Errorf("error marshaling connection information: %w", err).Error())
		}
		c.UI.Output(string(out))
	}
}