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xs/xs/xs.go

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// xs client
//
// Copyright (c) 2017-2020 Russell Magee
// Licensed under the terms of the MIT license (see LICENSE.mit in this
// distribution)
//
// golang implementation by Russ Magee (rmagee_at_gmail.com)
package main
import (
"bytes"
"encoding/binary"
"errors"
"flag"
"fmt"
"io"
"log"
"math/rand"
"os"
"os/exec"
"os/user"
"path"
"path/filepath"
"runtime"
"runtime/pprof"
"strings"
"sync"
"syscall"
"time"
"net/http"
_ "net/http/pprof" //nolint:gosec
xs "blitter.com/go/xs"
"blitter.com/go/xs/logger"
"blitter.com/go/xs/spinsult"
"blitter.com/go/xs/xsnet"
isatty "github.com/mattn/go-isatty"
)
var (
version string
gitCommit string // set in -ldflags by build
// wg controls when the goroutines handling client I/O complete
wg sync.WaitGroup
kcpMode string // set to a valid KCP BlockCrypt alg tag to use rather than TCP
// Log defaults to regular syslog output (no -d)
Log *logger.Writer
cpuprofile string
memprofile string
)
////////////////////////////////////////////////////
const (
CmdExitedEarly = 2
XSNetDialFailed = 3
ErrReadingAuthReply = 253
ServerRejectedSecureProposal = 254
GeneralProtocolErr = 255
)
const (
DeadCharPrefix = 0x1d
)
// Praise Bob. Do not remove, lest ye lose Slack.
const bob = string("\r\n\r\n" +
"@@@@@@@^^~~~~~~~~~~~~~~~~~~~~^@@@@@@@@@\r\n" +
"@@@@@@^ ~^ @ @@ @ @ @ I ~^@@@@@@\r\n" +
"@@@@@ ~ ~~ ~I @@@@@\r\n" +
"@@@@' ' _,w@< @@@@ .\r\n" +
"@@@@ @@@@@@@@w___,w@@@@@@@@ @ @@@\r\n" +
"@@@@ @@@@@@@@@@@@@@@@@@@@@@ I @@@ Bob\r\n" +
"@@@@ @@@@@@@@@@@@@@@@@@@@*@[ i @@@\r\n" +
"@@@@ @@@@@@@@@@@@@@@@@@@@[][ | ]@@@ bOb\r\n" +
"@@@@ ~_,,_ ~@@@@@@@~ ____~ @ @@@\r\n" +
"@@@@ _~ , , `@@@~ _ _`@ ]L J@@@ o\r\n" +
"@@@@ , @@w@ww+ @@@ww``,,@w@ ][ @@@@\r\n" +
"@@@@, @@@@www@@@ @@@@@@@ww@@@@@[ @@@@ BOB\r\n" +
"@@@@@_|| @@@@@@P' @@P@@@@@@@@@@@[|c@@@@\r\n" +
"@@@@@@w| '@@P~ P]@@@-~, ~Y@@^'],@@@@@@ . o\r\n" +
"@@@@@@@[ _ _J@@Tk ]]@@@@@@\r\n" +
"@@@@@@@@,@ @@, c,,,,,,,y ,w@@[ ,@@@@@@@\r\n" +
"@@@@@@@@@ i @w ====--_@@@@@ @@@@@@@@ o .\r\n" +
"@@@@@@@@@@`,P~ _ ~^^^^Y@@@@@ @@@@@@@@@\r\n" +
"@@@@^^=^@@^ ^' ,ww,w@@@@@ _@@@@@@@@@@ B o B\r\n" +
"@@@_xJ~ ~ , @@@@@@@P~_@@@@@@@@@@@@\r\n" +
"@@ @, ,@@@,_____ _,J@@@@@@@@@@@@@\r\n" +
"@@L `' ,@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\r\n" +
"@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\r\n" +
"\r\n")
type (
// Handler for special functions invoked by escSeqs
escHandler func(io.Writer)
// escSeqs is a map of special keystroke sequences to trigger escHandlers
escSeqs map[byte]escHandler
)
var (
escs = escSeqs{
'i': func(io.Writer) { os.Stdout.Write([]byte("\x1b[s\x1b[2;1H\x1b[1;31m[HKEXSH]\x1b[39;49m\x1b[u")) },
't': func(io.Writer) { os.Stdout.Write([]byte("\x1b[1;32m[HKEXSH]\x1b[39;49m")) },
'B': func(io.Writer) { os.Stdout.Write([]byte("\x1b[1;32m" + bob + "\x1b[39;49m")) },
}
)
// Copy copies from src to dst until either EOF is reached
// on src or an error occurs. It returns the number of bytes
// copied and the first error encountered while copying, if any.
//
// A successful Copy returns err == nil, not err == EOF.
// Because Copy is defined to read from src until EOF, it does
// not treat an EOF from Read as an error to be reported.
//
// If src implements the WriterTo interface,
// the copy is implemented by calling src.WriteTo(dst).
// Otherwise, if dst implements the ReaderFrom interface,
// the copy is implemented by calling dst.ReadFrom(src).
//
// This is identical to stdlib pkg/io.Copy save that it
// calls a client-custom version of copyBuffer(), which allows
// some client escape sequences to trigger special actions during
// interactive sessions.
//
// (See go doc xs/xs.{escSeqs,escHandler})
func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
written, err = copyBuffer(dst, src, nil)
return
}
// copyBuffer is the actual implementation of Copy and CopyBuffer.
// if buf is nil, one is allocated.
//
// This private version of copyBuffer is derived from the
// go stdlib pkg/io, with escape sequence interpretation to trigger
// some special client-side actions.
//
// (See go doc xs/xs.{escSeqs,escHandler})
func copyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err error) {
// NOTE: using dst.Write() in these esc funcs will cause the output
// to function as a 'macro', outputting as if user typed the sequence
// (that is, the client 'sees' the user type it, and the server 'sees'
// it as well).
//
// Using os.Stdout outputs to the client's term w/o it or the server
// 'seeing' the output.
//
// TODO: Devise a way to signal to main client thread that
// a goroutine should be spawned to do long-lived tasks for
// some esc sequences (eg., a time ticker in the corner of terminal,
// or tunnel traffic indicator - note we cannot just spawn a goroutine
// here, as copyBuffer() returns after each burst of data. Scope must
// outlive individual copyBuffer calls).
/*
// If the reader has a WriteTo method, use it to do the copy.
// Avoids an allocation and a copy.
if wt, ok := src.(io.WriterTo); ok {
return wt.WriteTo(dst)
}
// Similarly, if the writer has a ReadFrom method, use it to do the copy.
if rt, ok := dst.(io.ReaderFrom); ok {
return rt.ReadFrom(src)
}
*/ //nolint:gocritic,nolintlint
if buf == nil {
size := 32 * 1024
if l, ok := src.(*io.LimitedReader); ok && int64(size) > l.N {
if l.N < 1 {
size = 1
} else {
size = int(l.N)
}
}
buf = make([]byte, size)
}
var seqPos int
for {
nr, er := src.Read(buf)
if nr > 0 {
// Look for sequences to trigger client-side diags
// A repeat of 4 keys (conveniently 'dead' chars for most
// interactive shells; here CTRL-]) shall introduce
// some special responses or actions on the client side.
if seqPos < 4 { //nolint:gomnd
if buf[0] == DeadCharPrefix {
seqPos++
}
} else {
if v, ok := escs[buf[0]]; ok {
v(dst)
nr--
buf = buf[1:]
}
seqPos = 0
}
nw, ew := dst.Write(buf[0:nr])
if nw > 0 {
written += int64(nw)
}
if ew != nil {
err = ew
break
}
if nr != nw {
err = io.ErrShortWrite
break
}
}
if er != nil {
if er != io.EOF {
err = er
}
break
}
}
return written, err
}
////////////////////////////////////////////////////
// GetSize gets the terminal size using 'stty' command
//
// TODO: do in code someday instead of using external 'stty'
func GetSize() (cols, rows int, err error) {
cmd := exec.Command("stty", "size") // #nosec
cmd.Stdin = os.Stdin
out, err := cmd.Output()
if err != nil {
log.Println(err)
cols, rows = 80, 24 // failsafe
} else {
n, err := fmt.Sscanf(string(out), "%d %d\n", &rows, &cols)
if n < 2 ||
rows < 0 ||
cols < 0 ||
rows > 9000 ||
cols > 9000 ||
err != nil {
log.Printf("GetSize error: rows:%d cols:%d; %v\n",
rows, cols, err)
}
}
return
}
func buildCmdRemoteToLocal(copyQuiet bool, copyLimitBPS uint, destPath string) (captureStderr bool, cmd string, args []string) {
// Detect if we have 'pv'
// pipeview http://www.ivarch.com/programs/pv.shtml
// and use it for nice client progress display.
_, pverr := os.Stat("/usr/bin/pv")
if pverr != nil {
_, pverr = os.Stat("/usr/local/bin/pv")
}
if copyQuiet || pverr != nil {
// copyQuiet and copyLimitBPS are not applicable in dumb copy mode
captureStderr = true
cmd = xs.GetTool("tar")
args = []string{"-xz", "-C", destPath}
} else {
// TODO: Query remote side for total file/dir size
bandwidthInBytesPerSec := " -L " + fmt.Sprintf("%d ", copyLimitBPS)
displayOpts := " -pre " //nolint:goconst
cmd = xs.GetTool("bash")
args = []string{"-c", "pv " + displayOpts + bandwidthInBytesPerSec + "| tar -xz -C " + destPath}
}
log.Printf("[%v %v]\n", cmd, args)
return
}
func buildCmdLocalToRemote(copyQuiet bool, copyLimitBPS uint, files string) (captureStderr bool, cmd string, args []string) {
// Detect if we have 'pv'
// pipeview http://www.ivarch.com/programs/pv.shtml
// and use it for nice client progress display.
_, pverr := os.Stat("/usr/bin/pv")
if pverr != nil {
_, pverr = os.Stat("/usr/local/bin/pv")
}
if pverr != nil {
// copyQuiet and copyLimitBPS are not applicable in dumb copy mode
captureStderr = true
cmd = xs.GetTool("tar")
args = []string{"-cz", "-f", "/dev/stdout"}
files = strings.TrimSpace(files)
// Awesome fact: tar actually can take multiple -C args, and
// changes to the dest dir *as it sees each one*. This enables
// its use below, where clients can send scattered sets of source
// files and dirs to be extracted to a single dest dir server-side,
// whilst preserving the subtrees of dirs on the other side.
// Eg., tar -c -f /dev/stdout -C /dirA fileInA -C /some/where/dirB fileInB /foo/dirC
// packages fileInA, fileInB, and dirC at a single toplevel in the tar.
// The tar authors are/were real smarties :)
//
// This is the 'scatter/gather' logic to allow specification of
// files and dirs in different trees to be deposited in a single
// remote destDir.
for _, v := range strings.Split(files, " ") {
v, _ = filepath.Abs(v) // #nosec
dirTmp, fileTmp := path.Split(v)
if dirTmp == "" {
args = append(args, fileTmp)
} else {
args = append(args, "-C", dirTmp, fileTmp)
}
}
} else {
captureStderr = copyQuiet
bandwidthInBytesPerSec := " -L " + fmt.Sprintf("%d", copyLimitBPS)
displayOpts := " -pre " //nolint:goconst,nolintlint
cmd = xs.GetTool("bash")
args = []string{"-c", xs.GetTool("tar") + " -cz -f /dev/stdout "}
files = strings.TrimSpace(files)
// Awesome fact: tar actually can take multiple -C args, and
// changes to the dest dir *as it sees each one*. This enables
// its use below, where clients can send scattered sets of source
// files and dirs to be extracted to a single dest dir server-side,
// whilst preserving the subtrees of dirs on the other side.
// Eg., tar -c -f /dev/stdout -C /dirA fileInA -C /some/where/dirB fileInB /foo/dirC
// packages fileInA, fileInB, and dirC at a single toplevel in the tar.
// The tar authors are/were real smarties :)
//
// This is the 'scatter/gather' logic to allow specification of
// files and dirs in different trees to be deposited in a single
// remote destDir.
for _, v := range strings.Split(files, " ") {
v, _ = filepath.Abs(v) // #nosec
dirTmp, fileTmp := path.Split(v)
if dirTmp == "" {
args[1] = args[1] + fileTmp + " "
} else {
args[1] = args[1] + " -C " + dirTmp + " " + fileTmp + " "
}
}
args[1] = args[1] + "| pv" + displayOpts + bandwidthInBytesPerSec + " -s " + getTreeSizeSubCmd(files) + " -c"
}
log.Printf("[%v %v]\n", cmd, args)
return
}
func getTreeSizeSubCmd(paths string) (c string) {
if runtime.GOOS == "linux" {
c = " $(du -cb " + paths + " | tail -1 | cut -f 1) "
} else {
c = " $(expr $(du -c " + paths + ` | tail -1 | cut -f 1) \* 1024) `
}
return c
}
// doCopyMode begins a secure xs local<->remote file copy operation.
//
// TODO: reduce gocyclo
func doCopyMode(conn *xsnet.Conn, remoteDest bool, files string, copyQuiet bool, copyLimitBPS uint, rec *xs.Session) (exitStatus uint32, err error) {
if remoteDest {
log.Println("local files:", files, "remote filepath:", string(rec.Cmd()))
var c *exec.Cmd
// os.Clearenv()
// os.Setenv("HOME", u.HomeDir)
// os.Setenv("TERM", "vt102") // TODO: server or client option?
captureStderr, cmdName, cmdArgs := buildCmdLocalToRemote(copyQuiet, copyLimitBPS, strings.TrimSpace(files))
c = exec.Command(cmdName, cmdArgs...) // #nosec
c.Dir, _ = os.Getwd() // #nosec
log.Println("[wd:", c.Dir, "]")
c.Stdout = conn
stdErrBuffer := new(bytes.Buffer)
if captureStderr {
c.Stderr = stdErrBuffer
} else {
c.Stderr = os.Stderr
}
// Start the command (no pty)
err = c.Start() // returns immediately
/////////////
// NOTE: There is, apparently, a bug in Go stdlib here. Start()
// can actually return immediately, on a command which *does*
// start but exits quickly, with c.Wait() error
// "c.Wait status: exec: not started".
// As in this example, attempting a client->server copy to
// a nonexistent remote dir (it's tar exiting right away, exitStatus
// 2, stderr
// /bin/tar -xz -C /home/someuser/nosuchdir
// stderr: fork/exec /bin/tar: no such file or directory
//
// In this case, c.Wait() won't give us the real
// exit status (is it lost?).
/////////////
if err != nil {
fmt.Println("cmd exited immediately. Cannot get cmd.Wait().ExitStatus()")
err = errors.New("cmd exited prematurely")
exitStatus = uint32(CmdExitedEarly)
} else {
if err = c.Wait(); err != nil {
if exiterr, ok := err.(*exec.ExitError); ok {
// The program has exited with an exit code != 0
// This works on both Unix and Windows. Although package
// syscall is generally platform dependent, WaitStatus is
// defined for both Unix and Windows and in both cases has
// an ExitStatus() method with the same signature.
if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
exitStatus = uint32(status.ExitStatus())
if captureStderr {
fmt.Print(stdErrBuffer)
}
}
}
}
// send CSOExitStatus to inform remote (server) end cp is done
log.Println("Sending local exitStatus:", exitStatus)
r := make([]byte, 4) //nolint:gomnd
binary.BigEndian.PutUint32(r, exitStatus)
_, we := conn.WritePacket(r, xsnet.CSOExitStatus)
if we != nil {
fmt.Println("Error:", we)
}
// Do a final read for remote's exit status
s := make([]byte, 4) //nolint:gomnd
_, remErr := conn.Read(s)
if remErr != io.EOF &&
!strings.Contains(remErr.Error(), "use of closed network") &&
!strings.Contains(remErr.Error(), "connection reset by peer") {
fmt.Printf("*** remote status Read() failed: %v\n", remErr)
} else {
conn.SetStatus(0) // cp finished OK
}
// If local side status was OK, use remote side's status
if exitStatus == 0 {
exitStatus = uint32(conn.GetStatus())
log.Println("Received remote exitStatus:", exitStatus)
}
log.Printf("*** client->server cp finished , status %d ***\n", conn.GetStatus())
}
} else {
log.Println("remote filepath:", string(rec.Cmd()), "local files:", files)
destPath := files
_, cmdName, cmdArgs := buildCmdRemoteToLocal(copyQuiet, copyLimitBPS, destPath)
c := exec.Command(cmdName, cmdArgs...) // #nosec
c.Stdin = conn
c.Stdout = os.Stdout
c.Stderr = os.Stderr
// Start the command (no pty)
err = c.Start() // returns immediately
if err != nil {
fmt.Println(err)
} else {
if err = c.Wait(); err != nil {
if exiterr, ok := err.(*exec.ExitError); ok {
// The program has exited with an exit code != 0
// This works on both Unix and Windows. Although package
// syscall is generally platform dependent, WaitStatus is
// defined for both Unix and Windows and in both cases has
// an ExitStatus() method with the same signature.
if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
exitStatus = uint32(status.ExitStatus())
}
}
}
// return local status, if nonzero;
// otherwise, return remote status if nonzero
if exitStatus == 0 {
exitStatus = uint32(conn.GetStatus())
}
log.Printf("*** server->client cp finished, status %d ***\n", conn.GetStatus())
}
}
return
}
// doShellMode begins an xs shell session (one-shot command or
// interactive).
func doShellMode(isInteractive bool, conn *xsnet.Conn, oldState *xs.State, rec *xs.Session) {
// Client reader (from server) goroutine
// Read remote end's stdout
wg.Add(1)
// #gv:s/label=\"doShellMode\$1\"/label=\"shellRemoteToStdin\"/
// TODO:.gv:doShellMode:1:shellRemoteToStdin
shellRemoteToStdin := func() {
defer func() {
wg.Done()
}()
// By deferring a call to wg.Done(),
// each goroutine guarantees that it marks
// its direction's stream as finished.
// pkg io/Copy expects EOF so normally this will
// exit with inerr == nil
_, inerr := io.Copy(os.Stdout, conn)
if inerr != nil {
restoreTermState(oldState)
// Copy operations and user logging off will cause
// a "use of closed network connection" so handle that
// gracefully here
if !strings.HasSuffix(inerr.Error(), "use of closed network connection") {
log.Println(inerr)
exitWithStatus(1)
}
}
rec.SetStatus(uint32(conn.GetStatus()))
log.Println("rec.status:", rec.Status())
if isInteractive {
log.Println("[* Got EOF *]")
restoreTermState(oldState)
exitWithStatus(int(rec.Status()))
}
}
go shellRemoteToStdin()
// Only look for data from stdin to send to remote end
// for interactive sessions.
if isInteractive {
handleTermResizes(conn)
// client writer (to server) goroutine
// Write local stdin to remote end
wg.Add(1)
// #gv:s/label=\"doShellMode\$2\"/label=\"shellStdinToRemote\"/
// TODO:.gv:doShellMode:2:shellStdinToRemote
shellStdinToRemote := func() {
defer wg.Done()
_, outerr := func(conn *xsnet.Conn, r io.Reader) (w int64, e error) {
// Copy() expects EOF so this will
// exit with outerr == nil
// NOTE we use a local implementation of Copy() to allow
// for custom key sequences to trigger local actions
w, e = Copy(conn, r)
return w, e
}(conn, os.Stdin)
if outerr != nil {
log.Println(outerr)
fmt.Println(outerr)
restoreTermState(oldState)
log.Println("[Hanging up]")
exitWithStatus(0)
}
}
go shellStdinToRemote()
}
// Wait until both stdin and stdout goroutines finish before returning
// (ensure client gets all data from server before closing)
wg.Wait()
}
func usageShell() {
fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
fmt.Fprintf(os.Stderr, "%s [opts] [user]@server\n", os.Args[0])
flag.PrintDefaults()
}
func usageCp() {
fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
fmt.Fprintf(os.Stderr, "%s [opts] srcFileOrDir [...] [user]@server[:dstpath]\n", os.Args[0])
fmt.Fprintf(os.Stderr, "%s [opts] [user]@server[:srcFileOrDir] dstPath\n", os.Args[0])
flag.PrintDefaults()
}
// rejectUserMsg snarkily rebukes users giving incorrect
// credentials.
//
// TODO: do this from the server side and have client just emit that
func rejectUserMsg() string {
return "Begone, " + spinsult.GetSentence() + "\r\n"
}
// Transmit request to server for it to set up the remote end of a tunnel
//
// Server responds with [CSOTunAck:rport] or [CSOTunRefused:rport]
// (handled in xsnet.Read())
func reqTunnel(hc *xsnet.Conn, lp uint16 /*, p string*/ /*net.Addr*/, rp uint16) {
// Write request to server so it can attempt to set up its end
var bTmp bytes.Buffer
if e := binary.Write(&bTmp, binary.BigEndian, lp); e != nil {
fmt.Fprintln(os.Stderr, "reqTunnel:", e)
}
if e := binary.Write(&bTmp, binary.BigEndian, rp); e != nil {
fmt.Fprintln(os.Stderr, "reqTunnel:", e)
}
_ = logger.LogDebug(fmt.Sprintln("[Client sending CSOTunSetup]"))
if n, e := hc.WritePacket(bTmp.Bytes(), xsnet.CSOTunSetup); e != nil || n != len(bTmp.Bytes()) {
fmt.Fprintln(os.Stderr, "reqTunnel:", e)
}
}
func parseNonSwitchArgs(a []string) (user, host, path string, isDest bool, otherArgs []string) {
// Whether fancyArg is src or dst file depends on flag.Args() index;
// fancyArg as last flag.Args() element denotes dstFile
// fancyArg as not-last flag.Args() element denotes srcFile
var fancyUser, fancyHost, fancyPath string
for i, arg := range a {
if strings.Contains(arg, ":") || strings.Contains(arg, "@") {
fancyArg := strings.Split(flag.Arg(i), "@")
var fancyHostPath []string
if len(fancyArg) < 2 { //nolint:gomnd
//TODO: no user specified, use current
fancyUser = "[default:getUser]"
fancyHostPath = strings.Split(fancyArg[0], ":")
} else {
// user@....
fancyUser = fancyArg[0]
fancyHostPath = strings.Split(fancyArg[1], ":")
}
// [...@]host[:path]
if len(fancyHostPath) > 1 {
fancyPath = fancyHostPath[1]
}
fancyHost = fancyHostPath[0]
if i == len(a)-1 {
isDest = true
}
} else {
otherArgs = append(otherArgs, a[i])
}
}
return fancyUser, fancyHost, fancyPath, isDest, otherArgs
}
func launchTuns(conn *xsnet.Conn /*remoteHost string,*/, tuns string) {
/*remAddrs, _ := net.LookupHost(remoteHost)*/ //nolint:gocritic,nolintlint
if tuns == "" {
return
}
tunSpecs := strings.Split(tuns, ",")
for _, tunItem := range tunSpecs {
var lPort, rPort uint16
_, _ = fmt.Sscanf(tunItem, "%d:%d", &lPort, &rPort)
reqTunnel(conn, lPort /*remAddrs[0],*/, rPort)
}
}
func sendSessionParams(conn io.Writer /* *xsnet.Conn*/, rec *xs.Session) (e error) {
_, e = fmt.Fprintf(conn, "%d %d %d %d %d %d\n",
len(rec.Op()), len(rec.Who()), len(rec.ConnHost()), len(rec.TermType()), len(rec.Cmd()), len(rec.AuthCookie(true)))
if e != nil {
return
}
_, e = conn.Write(rec.Op())
if e != nil {
return
}
_, e = conn.Write(rec.Who())
if e != nil {
return
}
_, e = conn.Write(rec.ConnHost())
if e != nil {
return
}
_, e = conn.Write(rec.TermType())
if e != nil {
return
}
_, e = conn.Write(rec.Cmd())
if e != nil {
return
}
_, e = conn.Write(rec.AuthCookie(true))
return e
}
// TODO: reduce gocyclo
func main() { //nolint: funlen, gocyclo
var (
isInteractive bool
vopt bool
gopt bool // true: login via password, asking server to generate authToken
dbg bool
shellMode bool // true: act as shell, false: file copier
cipherAlg string
hmacAlg string
kexAlg string
server string
port uint
cmdStr string
tunSpecStr string // lport1:rport1[,lport2:rport2,...]
rekeySecs uint
remodRequested bool // true: when rekeying, switch to random cipher/hmac alg
copySrc []byte
copyDst string
copyQuiet bool
copyLimitBPS uint
authCookie string
chaffEnabled bool
chaffFreqMin uint
chaffFreqMax uint
chaffBytesMax uint
op []byte
)
// === Common (xs and xc) option parsing
flag.BoolVar(&vopt, "v", false, "show version")
flag.BoolVar(&dbg, "d", false, "debug logging")
flag.StringVar(&cipherAlg, "c", "C_AES_256", "session `cipher`"+`
C_AES_256
C_TWOFISH_128
C_BLOWFISH_64
C_CRYPTMT1
C_HOPSCOTCH
C_CHACHA20_12`)
flag.StringVar(&hmacAlg, "m", "H_SHA256", "session `HMAC`"+`
H_SHA256
H_SHA512`)
flag.StringVar(&kexAlg, "k", "KEX_HERRADURA512", "KEx `alg`"+`
KEX_HERRADURA256
KEX_HERRADURA512
KEX_HERRADURA1024
KEX_HERRADURA2048
KEX_KYBER512
KEX_KYBER768
KEX_KYBER1024
KEX_NEWHOPE
KEX_NEWHOPE_SIMPLE
KEX_FRODOKEM_1344AES
KEX_FRODOKEM_1344SHAKE
KEX_FRODOKEM_976AES
KEX_FRODOKEM_976SHAKE`)
flag.StringVar(&kcpMode, "K", "unused", "KCP `alg`, one of [KCP_NONE | KCP_AES | KCP_BLOWFISH | KCP_CAST5 | KCP_SM4 | KCP_SALSA20 | KCP_SIMPLEXOR | KCP_TEA | KCP_3DES | KCP_TWOFISH | KCP_XTEA] to use KCP (github.com/xtaci/kcp-go) reliable UDP instead of TCP") //nolint:lll
flag.UintVar(&port, "p", 2000, "``port") //nolint:gomnd,lll
flag.UintVar(&rekeySecs, "r", 300, "rekey interval in `secs`")
flag.BoolVar(&remodRequested, "R", false, "Borg Countermeasures (remodulate cipher/hmac alg on each rekey)")
//nolint:gocritic,nolintlint // flag.StringVar(&authCookie, "a", "", "auth cookie")
flag.BoolVar(&chaffEnabled, "e", true, "enable chaff pkts")
flag.UintVar(&chaffFreqMin, "f", 100, "chaff pkt freq min `msecs`") //nolint:gomnd
flag.UintVar(&chaffFreqMax, "F", 5000, "chaff pkt freq max `msecs`") //nolint:gomnd
flag.UintVar(&chaffBytesMax, "B", 64, "chaff pkt size max `bytes`") //nolint:gomnd
flag.StringVar(&cpuprofile, "cpuprofile", "", "write cpu profile to <`file`>")
flag.StringVar(&memprofile, "memprofile", "", "write memory profile to <`file`>")
// === xc vs. xs option parsing
// Find out what program we are (shell or copier)
myPath := strings.Split(os.Args[0], string(os.PathSeparator))
if myPath[len(myPath)-1] != "xc" &&
myPath[len(myPath)-1] != "_xc" &&
myPath[len(myPath)-1] != "xc.exe" &&
myPath[len(myPath)-1] != "_xc.exe" {
// xs accepts a command (-x) but not
// a srcpath (-r) or dstpath (-t)
flag.StringVar(&cmdStr, "x", "", "run <`command`> (if not specified, run interactive shell)")
flag.StringVar(&tunSpecStr, "T", "", "``tunnelspec - localPort:remotePort[,localPort:remotePort,...]")
flag.BoolVar(&gopt, "g", false, "ask server to generate authtoken")
shellMode = true
flag.Usage = usageShell
} else {
flag.BoolVar(&copyQuiet, "q", false, "do not output progress bar during copy")
flag.UintVar(&copyLimitBPS, "L", 8589934592, "copy max rate in bytes per sec") //nolint:gomnd
flag.Usage = usageCp
}
flag.Parse()
if vopt {
fmt.Printf("version %s (%s)\n", version, gitCommit)
exitWithStatus(0)
}
// === Profiling instrumentation
if cpuprofile != "" {
f, err := os.Create(cpuprofile)
if err != nil {
log.Fatal("could not create CPU profile: ", err)
}
defer f.Close()
fmt.Println("StartCPUProfile()")
if err := pprof.StartCPUProfile(f); err != nil {
log.Fatal("could not start CPU profile: ", err) //nolint:gocritic
} else {
defer pprof.StopCPUProfile()
}
go func() { http.ListenAndServe("localhost:6060", nil) }() //nolint:errcheck,gosec
}
// === User, host, port and path args for file operations, if applicable
remoteUser, remoteHost, tmpPath, pathIsDest, otherArgs :=
parseNonSwitchArgs(flag.Args())
//nolint:gocritic,nolintlint // fmt.Println("otherArgs:", otherArgs)
// Set defaults if user doesn't specify user, path or port
var uname string
if remoteUser == "" {
u, _ := user.Current()
uname = localUserName(u)
} else {
uname = remoteUser
}
if remoteHost != "" {
server = remoteHost + ":" + fmt.Sprintf("%d", port)
}
if tmpPath == "" {
tmpPath = "."
}
// === Copy mode arg and copy src/dest setup
var fileArgs string
if !shellMode /*&& tmpPath != ""*/ {
// -if pathIsSrc && len(otherArgs) > 1 ERROR
// -else flatten otherArgs into space-delim list => copySrc
if pathIsDest {
if len(otherArgs) == 0 {
log.Fatal("ERROR: Must specify at least one dest path for copy")
} else {
for _, v := range otherArgs {
copySrc = append(copySrc, ' ')
copySrc = append(copySrc, v...)
}
copyDst = tmpPath
fileArgs = string(copySrc)
}
} else {
if len(otherArgs) == 0 {
log.Fatal("ERROR: Must specify src path for copy")
} else if len(otherArgs) == 1 {
copyDst = otherArgs[0]
if strings.Contains(copyDst, "*") || strings.Contains(copyDst, "?") {
log.Fatal("ERROR: wildcards not allowed in dest path for copy")
}
} else {
log.Fatal("ERROR: cannot specify more than one dest path for copy")
}
copySrc = []byte(tmpPath)
fileArgs = copyDst
}
}
// === Do some final option consistency checks
//nolint:gocritic,nolintlint // fmt.Println("server finally is:", server)
if flag.NFlag() == 0 && server == "" {
flag.Usage()
exitWithStatus(0)
}
if cmdStr != "" && (len(copySrc) != 0 || copyDst != "") {
log.Fatal("incompatible options -- either cmd (-x) or copy ops but not both")
}
// Here we have parsed all options and can now carry out
// either the shell session or copy operation.
_ = shellMode
Log, _ = logger.New(logger.LOG_USER|logger.LOG_DEBUG|logger.LOG_NOTICE|logger.LOG_ERR, "xs")
xsnet.Init(dbg, "xs", logger.LOG_USER|logger.LOG_DEBUG|logger.LOG_NOTICE|logger.LOG_ERR)
if dbg {
log.SetOutput(Log)
} else {
log.SetOutput(io.Discard)
}
// === Auth token fetch for login
if !gopt {
// See if we can log in via an auth token
u, _ := user.Current()
ab, aerr := os.ReadFile(fmt.Sprintf("%s/%s", u.HomeDir, xsnet.XS_ID_AUTHTOKFILE))
if aerr == nil {
for _, line := range strings.Split(string(ab), "\n") {
line += "\n"
idx := strings.Index(line, remoteHost+":"+uname)
if idx >= 0 {
line = line[idx:]
entries := strings.SplitN(line, "\n", -1)
authCookie = strings.TrimSpace(entries[0])
// Security scrub
line = ""
break
}
}
if authCookie == "" {
_, _ = fmt.Fprintln(os.Stderr, "[no authtoken, use -g to request one from server]")
}
} else {
log.Printf("[cannot read %s/%s]\n", u.HomeDir, xsnet.XS_ID_AUTHTOKFILE)
}
}
runtime.GC()
// === Enforce some sane min/max vals on chaff flags
if chaffFreqMin < 2 { //nolint:gomnd
chaffFreqMin = 2
}
if chaffFreqMax == 0 {
chaffFreqMax = chaffFreqMin + 1
}
if chaffBytesMax == 0 || chaffBytesMax > 4096 {
chaffBytesMax = 64
}
// === Shell vs. Copy mode chaff and cmd setup
if shellMode {
// We must make the decision about interactivity before Dial()
// as it affects chaffing behaviour. 20180805
if gopt {
fmt.Fprintln(os.Stderr, "[requesting authtoken from server]")
op = []byte{'A'}
chaffFreqMin = 2
chaffFreqMax = 10
} else if cmdStr == "" {
op = []byte{'s'}
isInteractive = true
} else {
op = []byte{'c'}
// non-interactive cmds may complete quickly, so chaff earlier/faster
// to help ensure there's some cover to the brief traffic.
// (ignoring cmdline values)
chaffFreqMin = 2
chaffFreqMax = 10
}
} else {
// as copy mode is also non-interactive, set up chaffing
// just like the 'c' mode above
chaffFreqMin = 2
chaffFreqMax = 10
if pathIsDest {
// client->server file copy
// src file list is in copySrc
op = []byte{'D'}
//nolint:gocritic,nolintlint // fmt.Println("client->server copy:", string(copySrc), "->", copyDst)
cmdStr = copyDst
} else {
// server->client file copy
// remote src file(s) in copyDsr
op = []byte{'S'}
//nolint:gocritic,nolintlint // fmt.Println("server->client copy:", string(copySrc), "->", copyDst)
cmdStr = string(copySrc)
}
}
// === TCP / KCP Dial setup
proto := "tcp"
if kcpMode != "unused" {
proto = "kcp"
}
remodExtArg := ""
if remodRequested {
remodExtArg = "OPT_REMOD"
}
// Pass opt to Dial() via extensions arg
conn, err := xsnet.Dial(proto, server, cipherAlg, hmacAlg, kexAlg, kcpMode, remodExtArg)
if err != nil {
fmt.Println(err)
exitWithStatus(XSNetDialFailed)
}
conn.RekeyHelper(rekeySecs)
defer conn.ShutdownRekey()
// === Shell terminal mode (Shell vs. Copy) setup
// Set stdin in raw mode if it's an interactive session
// TODO: send flag to server side indicating this
// affects shell command used
var oldState *xs.State
defer conn.Close()
// === From this point on, conn is a secure encrypted channel
if shellMode {
if isatty.IsTerminal(os.Stdin.Fd()) {
oldState, err = xs.MakeRaw(os.Stdin.Fd())
if err != nil {
panic(err)
}
// #gv:s/label=\"main\$1\"/label=\"deferRestore\"/
// TODO:.gv:main:1:deferRestore
defer restoreTermState(oldState)
} else {
log.Println("NOT A TTY")
}
}
// === Login phase
// Start login timeout here and disconnect if user/pass phase stalls
// iloginImpatience := time.AfterFunc(20*time.Second, func() {
// i fmt.Printf(" .. [you still there? Waiting for a password.]")
// i})
loginTimeout := time.AfterFunc(30*time.Second, func() { //nolint:gomnd
restoreTermState(oldState)
fmt.Printf(" .. [login timeout]\n")
exitWithStatus(xsnet.CSELoginTimeout)
})
if authCookie == "" {
if !gopt {
// No auth token, prompt for password
fmt.Printf("Gimme cookie:")
}
ab, e := xs.ReadPassword(os.Stdin.Fd())
if !gopt {
fmt.Printf("\r\n")
}
if e != nil {
panic(e)
}
authCookie = string(ab)
}
//nolint:gocritic,nolintlint // i_ = loginImpatience.Stop()
_ = loginTimeout.Stop()
// Security scrub
runtime.GC()
// === Session param and TERM setup
// Set up session params and send over to server
rec := xs.NewSession(op, []byte(uname), []byte(remoteHost), []byte(os.Getenv("TERM")), []byte(cmdStr), []byte(authCookie), 0)
sendErr := sendSessionParams(&conn, rec)
if sendErr != nil {
restoreTermState(oldState)
rec.SetStatus(ServerRejectedSecureProposal)
fmt.Fprintln(os.Stderr, "Error: server rejected secure proposal params or login timed out")
exitWithStatus(int(rec.Status()))
//nolint:gocritic,nolintlint // log.Fatal(sendErr)
}
// Security scrub
authCookie = "" //nolint: ineffassign
runtime.GC()
// === Login Auth
// === Read auth reply from server
authReply := make([]byte, 1) // bool: 0 = fail, 1 = pass
_, err = conn.Read(authReply)
if err != nil {
// === Exit if auth reply not received
fmt.Fprintln(os.Stderr, "Error reading auth reply")
rec.SetStatus(ErrReadingAuthReply)
} else if authReply[0] == 0 {
// === .. or if auth failed
fmt.Fprintln(os.Stderr, rejectUserMsg())
rec.SetStatus(GeneralProtocolErr)
} else {
// === Set up connection keepalive to server
conn.StartupKeepAlive() // goroutine, returns immediately
defer conn.ShutdownKeepAlive()
// === Set up chaffing to server
conn.SetupChaff(chaffFreqMin, chaffFreqMax, chaffBytesMax) // enable client->server chaffing
if chaffEnabled {
// #gv:s/label=\"main\$2\"/label=\"deferCloseChaff\"/
// TODO:.gv:main:2:deferCloseChaff
conn.StartupChaff() // goroutine, returns immediately
defer conn.ShutdownChaff()
}
// === (goroutine) Start keepAliveWorker for tunnels
// #gv:s/label=\"main\$1\"/label=\"tunKeepAlive\"/
// TODO:.gv:main:1:tunKeepAlive
// [1]: better to always send tunnel keepAlives even if client didn't specify
// any, to prevent listeners from knowing this.
// [1] if tunSpecStr != "" {
keepAliveWorker := func() {
for {
// Add a bit of jitter to keepAlive so it doesn't stand out quite as much
time.Sleep(time.Duration(2000-rand.Intn(200)) * time.Millisecond) //nolint:gosec,gomnd
// FIXME: keepAlives should probably have small random packet len/data as well
// to further obscure them vs. interactive or tunnel data
// keepAlives must be >=2 bytes, due to processing elsewhere
conn.WritePacket([]byte{0, 0}, xsnet.CSOTunKeepAlive) //nolint: errcheck
}
}
go keepAliveWorker()
// [1]}
// === Session entry (shellMode or copyMode)
if shellMode {
// === (shell) launch tunnels
launchTuns(&conn /*remoteHost,*/, tunSpecStr)
doShellMode(isInteractive, &conn, oldState, rec)
} else {
// === (.. or file copy)
s, _ := doCopyMode(&conn, pathIsDest, fileArgs, copyQuiet, copyLimitBPS, rec)
rec.SetStatus(s)
}
if rec.Status() != 0 {
restoreTermState(oldState)
fmt.Fprintln(os.Stderr, "Session exited with status:", rec.Status())
}
}
if oldState != nil {
restoreTermState(oldState)
oldState = nil
}
// === Exit
exitWithStatus(int(rec.Status()))
}
// currentUser returns the current username minus any OS-specific prefixes
// such as MS Windows workgroup prefixes (eg. workgroup\user).
func localUserName(u *user.User) string {
if u == nil {
log.Fatal("null User?!")
}
// WinAPI: username may have CIFS prefix %USERDOMAIN%\
userspec := strings.Split(u.Username, `\`)
username := userspec[len(userspec)-1]
return username
}
func restoreTermState(oldState *xs.State) {
_ = xs.Restore(os.Stdin.Fd(), oldState)
}
// exitWithStatus wraps os.Exit() plus does any required pprof housekeeping
func exitWithStatus(status int) {
if cpuprofile != "" {
pprof.StopCPUProfile()
}
if memprofile != "" {
f, err := os.Create(memprofile)
if err != nil {
log.Fatal("could not create memory profile: ", err)
}
defer f.Close()
runtime.GC() // get up-to-date statistics
if err := pprof.WriteHeapProfile(f); err != nil {
log.Fatal("could not write memory profile: ", err) //nolint:gocritic
}
}
os.Exit(status)
}
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