Merge 2293f40fbf into ea8f9b5109

Dockerfile

@@ -0,0 +1,22 @@
+FROM golang:1.17
+
+WORKDIR $GOPATH/src/github.com/amitbet/vncproxy
+
+RUN mkdir -p $GOPATH/src/github.com/amitbet/vncproxy
+COPY . .
+
+RUN cd $GOPATH/src/github.com/amitbet/vncproxy/recorder/cmd && \
+  CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o /recorder .
+RUN cd $GOPATH/src/github.com/amitbet/vncproxy/proxy/cmd && \
+  CGO_ENABLED=0 GOOS=linux GOARCH=amd64  go build -ldflags="-s -w" -o /proxy .
+RUN cd $GOPATH/src/github.com/amitbet/vncproxy/player/cmd && \
+  CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o /player .
+
+FROM scratch
+COPY --from=0 /recorder /recorder
+COPY --from=0 /proxy /proxy
+COPY --from=0 /player /player
+
+EXPOSE 5900
+
+ENTRYPOINT ["/proxy"]

README.md

@@ -8,6 +8,7 @@ An RFB proxy, written in go that can save and replay FBS files
 * Can also be used as:
     * A screen recorder vnc-client
     * A replay server to show fbs recordings to connecting clients
+    * Authentication proxy for reMarkable tablet (2.10+)
 
 - Tested on tight encoding with:
     - Tightvnc (client + java client + server)
@@ -40,6 +41,21 @@ An RFB proxy, written in go that can save and replay FBS files
     * Listens to Tcp & WS ports
     * Replays a hard-coded FBS file in normal speed to all connecting vnc clients
 
+### Examples of using with reMarkable
+* Simply run the proxy with the `-reMarkable DEVICE_ID` flag
+* To get the `DEVICE_ID`:
+    * Log into reMarkable via SSH
+    * Extract the `devicetoken` string (exclude the `@ByteArray` wrapper) the string from `/etc/remarkable.conf`
+    * Run the following Python snippet to decrypt the `devicetoken`:
+      ```
+      pip3 install --user PyJWT
+      python3 -c 'import sys,jwt;t=jwt.decode(sys.argv[1],options={"verify_signature":False});print(t)' '(DEVICE TOKEN HERE)'
+      ```
+    * In output, you should get a string starting with `auth0|`. The whole string is your device ID which should 
+      be passed to be `-reMarkable` flag.
+* After you should be able to connect to the reMarkable via the proxy with a normal
+  VNC client (tested with TightVNC)
+
 ## **Architecture**
 
 ![Image of Arch](https://github.com/amitbet/vncproxy/blob/master/architecture/proxy-arch.png?raw=true)

client/client-conn.go

@@ -4,11 +4,12 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
-	"github.com/amitbet/vncproxy/common"
-	"github.com/amitbet/vncproxy/logger"
 	"io"
 	"net"
 	"unicode"
+
+	"github.com/amitbet/vncproxy/common"
+	"github.com/amitbet/vncproxy/logger"
 )
 
 // A ServerMessage implements a message sent from the server to the client.

client/client_auth.go

@@ -1,9 +1,13 @@
 package client
 
 import (
+	"bytes"
 	"crypto/des"
+	"crypto/sha256"
 	"encoding/binary"
 	"io"
+
+	"github.com/amitbet/vncproxy/logger"
 )
 
 // ClientAuthNone is the "none" authentication. See 7.2.1
@@ -110,3 +114,46 @@ func (p *PasswordAuth) encrypt(key string, bytes []byte) ([]byte, error) {
 
 	return crypted, nil
 }
+
+// RemarkableAuth is the authentication method used by reMarkable tablet's
+// Screen Sharing feature
+type RemarkableAuth struct {
+	RemarkableTimestamp uint64
+	RemarkableDeviceId  string
+}
+
+func (p *RemarkableAuth) SecurityType() uint8 {
+	return 100
+}
+
+func (p *RemarkableAuth) Handshake(c io.ReadWriteCloser) error {
+	userIdHash := sha256.Sum256([]byte(p.RemarkableDeviceId))
+
+	var tsBuf []byte
+	pb := bytes.NewBuffer(tsBuf)
+	err := binary.Write(pb, binary.BigEndian, p.RemarkableTimestamp)
+	if err != nil {
+		return err
+	}
+	logger.Debugf("Hash with timestamp: %x", pb.Bytes())
+	userIdAndTs := append(pb.Bytes(), userIdHash[:]...)
+	logger.Debugf("Hash with timestamp and user ID hash: %x", userIdAndTs)
+
+	challenge := sha256.Sum256(userIdAndTs)
+	var challengeLength uint32 = uint32(len(challenge))
+	logger.Debugf("Writing challenge length: %v", challengeLength)
+	if err := binary.Write(c, binary.BigEndian, challengeLength); err != nil {
+		return err
+	}
+	logger.Debugf("Writing challenge: %x", challenge)
+	if err := binary.Write(c, binary.BigEndian, challenge); err != nil {
+		return err
+	}
+
+	// Some reason there is another security result... we're just gonna ignore this.
+	var securityResult uint8
+	if err = binary.Read(c, binary.BigEndian, &securityResult); err != nil {
+		return err
+	}
+	return nil
+}

go.mod

@@ -1,3 +1,5 @@
 module github.com/amitbet/vncproxy
 
 require golang.org/x/net v0.0.0-20181129055619-fae4c4e3ad76
+
+go 1.13

proxy/cmd/main.go

@@ -4,6 +4,8 @@ import (
 	"flag"
 	"os"
 	"path/filepath"
+	"strconv"
+	"strings"
 
 	"github.com/amitbet/vncproxy/logger"
 	vncproxy "github.com/amitbet/vncproxy/proxy"
@@ -20,7 +22,9 @@ func main() {
 	var targetVncHost = flag.String("targHost", "", "target vnc server host (deprecated, use -target)")
 	var targetVncPass = flag.String("targPass", "", "target vnc password")
 	var logLevel = flag.String("logLevel", "info", "change logging level")
-
+	var reMarkable = flag.String("reMarkable", "", "reMarkable device ID (enable reMarkable 2.10+ support)")
+	var overrideEncodings = flag.String("overrideEncodings", "", "force a specific set of encodings to be sent to the target vnc server (encoding types separated by comma)")
+	var tls = flag.Bool("tls", false, "use TLS connection (turned on automatically if reMarkable)")
 	flag.Parse()
 	logger.SetLogLevel(*logLevel)
 
@@ -48,6 +52,16 @@ func main() {
 	if *wsPort != "" {
 		wsURL = "http://0.0.0.0:" + string(*wsPort) + "/"
 	}
+	var overrideEncodingsList []uint32
+	if *overrideEncodings != "" {
+		for _, enc := range strings.Split(*overrideEncodings, ",") {
+			encI, err := strconv.Atoi(enc)
+			if err != nil {
+				panic(err)
+			}
+			overrideEncodingsList = append(overrideEncodingsList, uint32(encI))
+		}
+	}
 	proxy := &vncproxy.VncProxy{
 		WsListeningURL:   wsURL, // empty = not listening on ws
 		TCPListeningURL:  tcpURL,
@@ -60,6 +74,9 @@ func main() {
 			ID:                 "dummySession",
 			Status:             vncproxy.SessionStatusInit,
 			Type:               vncproxy.SessionTypeProxyPass,
+			RemarkableDeviceId: *reMarkable,
+			TLS:                *reMarkable != "" || *tls,
+			OverrideEncodings:  overrideEncodingsList,
 		}, // to be used when not using sessions
 		UsingSessions: false, //false = single session - defined in the var above
 	}
@@ -75,6 +92,10 @@ func main() {
 	} else {
 		logger.Info("FBS recording is turned off")
 	}
+	if *reMarkable != "" {
+		logger.Info("reMarkable 2.10+ support turned on")
+		proxy.Remarkable = true
+	}
 
 	proxy.StartListening()
 }

proxy/message-listeners.go

@@ -9,6 +9,8 @@ import (
 
 type ClientUpdater struct {
 	conn                   *client.ClientConn
+	suppressedMessageTypes []common.ClientMessageType
+	overrideEncodings      []common.EncodingType
 }
 
 // Consume recieves vnc-server-bound messages (Client messages) and updates the server part of the proxy
@@ -19,8 +21,15 @@ func (cc *ClientUpdater) Consume(seg *common.RfbSegment) error {
 	case common.SegmentFullyParsedClientMessage:
 		clientMsg := seg.Message.(common.ClientMessage)
 		logger.Debugf("ClientUpdater.Consume:(vnc-server-bound) got ClientMessage type=%s", clientMsg.Type())
-		switch clientMsg.Type() {
 
+		switch clientMsg.Type() {
+		case common.SetEncodingsMsgType:
+			if len(cc.overrideEncodings) > 0 {
+				logger.Debugf("ClientUpdater.Consume:(vnc-server-bound) overriding supported encodings with %v", cc.overrideEncodings)
+				encodingsMsg := clientMsg.(*server.MsgSetEncodings)
+				encodingsMsg.EncNum = uint16(len(cc.overrideEncodings))
+				encodingsMsg.Encodings = cc.overrideEncodings
+			}
 		case common.SetPixelFormatMsgType:
 			// update pixel format
 			logger.Debugf("ClientUpdater.Consume: updating pixel format")
@@ -28,6 +37,18 @@ func (cc *ClientUpdater) Consume(seg *common.RfbSegment) error {
 			cc.conn.PixelFormat = pixFmtMsg.PF
 		}
 
+		suppressMessage := false
+		for _, suppressed := range cc.suppressedMessageTypes {
+			if suppressed == clientMsg.Type() {
+				suppressMessage = true
+				break
+			}
+		}
+		if suppressMessage {
+			logger.Infof("ClientUpdater.Consume:(vnc-server-bound) Suppressing client message type=%s", clientMsg.Type())
+			return nil
+		}
+
 		err := clientMsg.Write(cc.conn)
 		if err != nil {
 			logger.Errorf("ClientUpdater.Consume (vnc-server-bound, SegmentFullyParsedClientMessage): problem writing to port: %s", err)

proxy/proxy.go

@@ -1,6 +1,9 @@
 package proxy
 
 import (
+	"bytes"
+	"crypto/tls"
+	"encoding/binary"
 	"net"
 	"path"
 	"strconv"
@@ -22,10 +25,11 @@ type VncProxy struct {
 	ProxyVncPassword string      //empty = no auth
 	SingleSession    *VncSession // to be used when not using sessions
 	UsingSessions    bool        //false = single session - defined in the var above
+	Remarkable       bool
 	sessionManager   *SessionManager
 }
 
-func (vp *VncProxy) createClientConnection(target string, vncPass string) (*client.ClientConn, error) {
+func (vp *VncProxy) createClientConnection(target string, vncPass string, tlsEnabled bool, reMarkableDeviceId string) (*client.ClientConn, error) {
 	var (
 		nc  net.Conn
 		err error
@@ -35,6 +39,19 @@ func (vp *VncProxy) createClientConnection(target string, vncPass string) (*clie
 		nc, err = net.Dial("unix", target)
 	} else {
 		nc, err = net.Dial("tcp", target)
+		if tlsEnabled {
+			logger.Info("Upgrading to TLS connection...")
+			config := tls.Config{
+				InsecureSkipVerify: true,
+			}
+			tc := tls.Client(nc, &config)
+			err = tc.Handshake()
+			if err != nil {
+				return nil, err
+			}
+
+			nc = tc
+		}
 	}
 
 	if err != nil {
@@ -44,6 +61,31 @@ func (vp *VncProxy) createClientConnection(target string, vncPass string) (*clie
 
 	var noauth client.ClientAuthNone
 	authArr := []client.ClientAuth{&client.PasswordAuth{Password: vncPass}, &noauth}
+	var rmTimestamp uint64
+	if reMarkableDeviceId != "" {
+		logger.Info("Enabling reMarkable 2.10+ support")
+
+		authC, err := net.ListenPacket("udp", ":5901")
+		if err != nil {
+			return nil, err
+		}
+		defer authC.Close()
+
+		buffer := make([]byte, 128) // datagram size 51 bytes
+		n, addr, err := authC.ReadFrom(buffer)
+		logger.Debugf("Received datagram from reMarkable (%v, %v bytes)", addr, n)
+
+		pb := bytes.NewBuffer(buffer)
+		err = binary.Read(pb, binary.BigEndian, &rmTimestamp)
+		if err != nil {
+			return nil, err
+		}
+		logger.Debugf("reMarkable timestamp is %v", rmTimestamp)
+		authArr = append(authArr, &client.RemarkableAuth{
+			RemarkableTimestamp: rmTimestamp,
+			RemarkableDeviceId:  reMarkableDeviceId,
+		})
+	}
 
 	clientConn, err := client.NewClientConn(nc,
 		&client.ClientConfig{
@@ -100,7 +142,7 @@ func (vp *VncProxy) newServerConnHandler(cfg *server.ServerConfig, sconn *server
 			target = session.TargetHostname + ":" + session.TargetPort
 		}
 
-		cconn, err := vp.createClientConnection(target, session.TargetPassword)
+		cconn, err := vp.createClientConnection(target, session.TargetPassword, session.TLS, session.RemarkableDeviceId)
 		if err != nil {
 			session.Status = SessionStatusError
 			logger.Errorf("Proxy.newServerConnHandler error creating connection: %s", err)
@@ -119,7 +161,16 @@ func (vp *VncProxy) newServerConnHandler(cfg *server.ServerConfig, sconn *server
 
 		// gets the messages from the server part (from vnc-client),
 		// and write through the client to the actual vnc-server
-		clientUpdater := &ClientUpdater{cconn}
+		var clientUpdater *ClientUpdater
+		clientUpdater = &ClientUpdater{conn: cconn}
+		if session.RemarkableDeviceId != "" {
+			clientUpdater.suppressedMessageTypes = []common.ClientMessageType{common.SetPixelFormatMsgType}
+		}
+		if len(session.OverrideEncodings) > 0 {
+			for _, enc := range session.OverrideEncodings {
+				clientUpdater.overrideEncodings = append(clientUpdater.overrideEncodings, common.EncodingType(enc))
+			}
+		}
 		sconn.Listeners.AddListener(clientUpdater)
 
 		err = cconn.Connect()
@@ -185,6 +236,9 @@ func (vp *VncProxy) StartListening() {
 		NewConnHandler:   vp.newServerConnHandler,
 		UseDummySession:  !vp.UsingSessions,
 	}
+	if vp.Remarkable {
+		cfg.DesktopName = []byte("reMarkable rfb")
+	}
 
 	if vp.TCPListeningURL != "" && vp.WsListeningURL != "" {
 		logger.Infof("running two listeners: tcp port: %s, ws url: %s", vp.TCPListeningURL, vp.WsListeningURL)

proxy/vnc-session.go

@@ -24,4 +24,7 @@ type VncSession struct {
 	Status             SessionStatus
 	Type               SessionType
 	ReplayFilePath     string
+	RemarkableDeviceId string
+	TLS                bool
+	OverrideEncodings  []uint32
 }

server/client-messages.go

@@ -3,6 +3,7 @@ package server
 import (
 	"encoding/binary"
 	"io"
+
 	"github.com/amitbet/vncproxy/common"
 )