🎉 Import source

Author: x1unix

.gitignore

@@ -0,0 +1,4 @@
+.idea/
+vendor/
+.vscode/
+build/

Makefile

@@ -0,0 +1,6 @@
+ADDR ?= :1000
+APP_SH ?= /bin/bash
+
+.PHONY: run
+run:
+	@go run ./cmd/telshell -addr=$(ADDR) -shell=$(APP_SH)

cmd/telshell/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"flag"
+	"github.com/x1unix/telshell"
+	"github.com/x1unix/telshell/internal/app"
+	"go.uber.org/zap"
+)
+
+func init() {
+	l, err := zap.NewDevelopment()
+	if err != nil {
+		panic(err)
+	}
+
+	zap.ReplaceGlobals(l)
+}
+
+
+func main() {
+	shellFlags := telshell.ShellArgs[:]
+	addr := flag.String("addr", ":1000", "Address to listen")
+	shell := flag.String("shell", telshell.DefaultShell, "Shell to use")
+	flag.Var(&shellFlags, "shellarg", "Shell args")
+	flag.Parse()
+	if err := start(*addr, *shell, shellFlags); err != nil {
+		zap.S().Fatal(err)
+	}
+}
+
+func start(addr, shell string, shellArgs []string) error {
+	ctx, _ := app.GetApplicationContext()
+	h := telshell.NewShellHandler(shell, shellArgs...)
+	srv := telshell.NewServer(h)
+
+	/*go func() {
+		zap.S().Info("listening to ctx")
+		for {
+			select {
+			case <-ctx.Done():
+				zap.S().Info("ctx.Done()")
+			default:
+			}
+		}
+	}()*/
+
+	return srv.Start(ctx, addr)
+}

go.mod

@@ -0,0 +1,12 @@
+module github.com/x1unix/telshell
+
+go 1.13
+
+require (
+	github.com/pkg/errors v0.8.1
+	go.uber.org/atomic v1.5.1 // indirect
+	go.uber.org/multierr v1.4.0 // indirect
+	go.uber.org/zap v1.13.0
+	golang.org/x/lint v0.0.0-20191125180803-fdd1cda4f05f // indirect
+	golang.org/x/tools v0.0.0-20200102200121-6de373a2766c // indirect
+)

go.sum

@@ -0,0 +1,60 @@
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
+github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
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+go.uber.org/multierr v1.3.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=
+go.uber.org/multierr v1.4.0 h1:f3WCSC2KzAcBXGATIxAB1E2XuCpNU255wNKZ505qi3E=
+go.uber.org/multierr v1.4.0/go.mod h1:VgVr7evmIr6uPjLBxg28wmKNXyqE9akIJ5XnfpiKl+4=
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+go.uber.org/zap v1.13.0/go.mod h1:zwrFLgMcdUuIBviXEYEH1YKNaOBnKXsx2IPda5bBwHM=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
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+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/lint v0.0.0-20190930215403-16217165b5de h1:5hukYrvBGR8/eNkX5mdUezrA6JiaEZDtJb9Ei+1LlBs=
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+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
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handler.go

@@ -0,0 +1,50 @@
+package telshell
+
+import (
+	"context"
+	"fmt"
+	"github.com/pkg/errors"
+	"go.uber.org/zap"
+	"io"
+	"os"
+	"os/exec"
+)
+
+const bufferSize = 4
+
+type Handler interface {
+	Handle(ctx context.Context, rw io.ReadWriter) error
+}
+
+type ShellHandler struct {
+	shellPath string
+	shellArgs []string
+	log *zap.SugaredLogger
+}
+
+func NewShellHandler(shell string, args ...string) ShellHandler {
+	return ShellHandler{
+		shellPath: shell,
+		shellArgs: args,
+		log: zap.S().Named("shell"),
+	}
+}
+
+func (s ShellHandler) Handle(ctx context.Context, rw io.ReadWriter) error {
+	fmt.Fprintf(rw, "Current shell is %q\n", s.shellPath)
+
+	wrapCtx, cancelFn := context.WithCancel(ctx)
+	wrapper := NewTerminalWrapper(s.log, rw, bufferSize)
+	cmd := exec.CommandContext(ctx, s.shellPath, "-i")
+	cmd.Env = os.Environ()
+	if err := wrapper.Listen(wrapCtx, cmd); err != nil {
+		return err
+	}
+
+	if err := cmd.Start(); err != nil {
+		return errors.Wrap(err, "failed to start shell instance")
+	}
+
+	defer cancelFn()
+	return cmd.Wait()
+}

internal/app/array_flags.go

@@ -0,0 +1,12 @@
+package app
+
+type FlagsArray []string
+
+func (i *FlagsArray) String() string {
+	return "my string representation"
+}
+
+func (i *FlagsArray) Set(value string) error {
+	*i = append(*i, value)
+	return nil
+}

internal/app/context.go

@@ -0,0 +1,34 @@
+package app
+
+import (
+	"context"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+)
+
+var once = &sync.Once{}
+
+var (
+	ctx        context.Context
+	cancelFunc context.CancelFunc
+)
+
+// GetApplicationContext returns application context for graceful shutdown
+func GetApplicationContext() (context.Context, context.CancelFunc) {
+	once.Do(func() {
+		ctx, cancelFunc = context.WithCancel(context.Background())
+
+		go func() {
+			signals := []os.Signal{syscall.SIGTERM, syscall.SIGINT, os.Interrupt}
+			sigChan := make(chan os.Signal, 1)
+			signal.Notify(sigChan, signals...)
+			defer signal.Reset(signals...)
+			<-sigChan
+			cancelFunc()
+		}()
+	})
+
+	return ctx, cancelFunc
+}

internal/helpers/hexdump.go

@@ -0,0 +1,28 @@
+package helpers
+
+import (
+	"strconv"
+	"strings"
+)
+
+const cols = 8
+
+func BytesToMessage(data []byte) string {
+	str := strings.Builder{}
+	for _, b := range data {
+		str.WriteByte(b)
+		str.WriteString("  0x" + strconv.FormatInt(int64(b), 16))
+		str.WriteRune('\n')
+	}
+
+	return str.String()
+}
+
+func BytesToHex(data []byte) string {
+	str := strings.Builder{}
+	for _, b := range data {
+		str.WriteString(" 0x" + strconv.FormatInt(int64(b), 16))
+	}
+
+	return str.String()
+}

internal/helpers/net.go

@@ -0,0 +1,16 @@
+package helpers
+
+import (
+	"strings"
+)
+
+// IsErrClosing is workaround for detecting usage of closed TCP connection.
+// Required, since poll.ErrClosing is private and wrapped in net.OpError.
+//
+// See:	https://github.com/golang/go/issues/10176
+func IsErrClosing(err error) bool {
+	if err == nil {
+		return false
+	}
+	return strings.Contains(err.Error(), "use of closed network connection")
+}

iowrapper.go

@@ -0,0 +1,103 @@
+package telshell
+
+import (
+	"context"
+	"github.com/x1unix/telshell/internal/helpers"
+	"go.uber.org/zap"
+	"io"
+	"os/exec"
+)
+
+const (
+	charCr = 0xD
+	charNul = 0x0
+)
+
+type TerminalWrapper struct {
+	buffSize int
+	client io.ReadWriter
+	log *zap.SugaredLogger
+}
+
+func NewTerminalWrapper(log *zap.SugaredLogger, client io.ReadWriter, buffSize int) TerminalWrapper {
+	return TerminalWrapper{client: client, log: log, buffSize: buffSize}
+}
+
+func (w TerminalWrapper) Listen(ctx context.Context, cmd *exec.Cmd) error {
+	return w.listenHost(ctx, cmd)
+}
+
+func (w TerminalWrapper) listenHost(ctx context.Context, cmd *exec.Cmd) error {
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return err
+	}
+
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return err
+	}
+
+	go w.readFromHost(ctx, stdout)
+	go w.readFromHost(ctx, stderr)
+	go w.writeToHost(ctx, stdin)
+
+	return nil
+}
+
+func (w TerminalWrapper) readFromHost(ctx context.Context, r io.Reader) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		buff := make([]byte, w.buffSize)
+		_, _ = r.Read(buff)
+		w.client.Write(buff)
+	}
+}
+
+func (w TerminalWrapper) writeToHost(ctx context.Context, dest io.Writer) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+		arr := make([]byte, w.buffSize)
+		_, err := w.client.Read(arr)
+		if err == io.EOF || helpers.IsErrClosing(err) {
+			return
+		}
+		if err != nil {
+			w.log.Error(err)
+			continue
+		}
+
+		//w.log.Infof("got data (%d bytes):\n%s", c, helpers.BytesToMessage(arr))
+		filtered := w.filterChars(arr)
+		dest.Write(filtered)
+	}
+}
+
+func (w TerminalWrapper) filterChars(msg []byte) []byte {
+	filtered := make([]byte, 0, len(msg))
+	for _, b := range msg {
+		switch b {
+		case charCr, charNul:
+			continue
+		default:
+		}
+
+		filtered = append(filtered, b)
+	}
+
+	return filtered
+}

platform_posix.go

@@ -0,0 +1,10 @@
+// +build !windows,!js,!nacl
+
+package telshell
+
+import "github.com/x1unix/telshell/internal/app"
+
+var (
+	DefaultShell = "/bin/sh"
+	ShellArgs = app.FlagsArray{"-i"}
+)