xs/hkexsh/hkexsh.go

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// hkexsh client
//
// Copyright (c) 2017-2018 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)
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package main
import (
"bytes"
"encoding/binary"
"errors"
"flag"
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"fmt"
"io"
"io/ioutil"
"log"
"os"
"os/exec"
"os/user"
"path"
"path/filepath"
"runtime"
"strings"
"sync"
"syscall"
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hkexsh "blitter.com/go/hkexsh"
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"blitter.com/go/hkexsh/hkexnet"
"blitter.com/go/hkexsh/spinsult"
isatty "github.com/mattn/go-isatty"
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)
var (
wg sync.WaitGroup
)
// Get terminal size using 'stty' command
func GetSize() (cols, rows int, err error) {
cmd := exec.Command("stty", "size")
cmd.Stdin = os.Stdin
out, err := cmd.Output()
if err != nil {
log.Println(err)
cols, rows = 80, 24 //failsafe
} else {
fmt.Sscanf(string(out), "%d %d\n", &rows, &cols)
}
return
}
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 {
//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 fancyPath == "" {
// fancyPath = "."
//}
if i == len(a)-1 {
isDest = true
//fmt.Println("remote path isDest")
}
//fmt.Println("fancyArgs: user:", fancyUser, "host:", fancyHost, "path:", fancyPath)
} else {
otherArgs = append(otherArgs, a[i])
}
}
return fancyUser, fancyHost, fancyPath, isDest, otherArgs
}
// doCopyMode begins a secure hkexsh local<->remote file copy operation.
func doCopyMode(conn *hkexnet.Conn, remoteDest bool, files string, rec *hkexsh.Session) (err error, exitStatus uint32) {
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?
cmdName := "/bin/tar"
cmdArgs := []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)
dirTmp, fileTmp := path.Split(v)
if dirTmp == "" {
cmdArgs = append(cmdArgs, fileTmp)
} else {
cmdArgs = append(cmdArgs, "-C", dirTmp, fileTmp)
}
}
log.Printf("[%v %v]\n", cmdName, cmdArgs)
// NOTE the lack of quotes around --xform option's sed expression.
// When args are passed in exec() format, no quoting is required
// (as this isn't input from a shell) (right? -rlm 20180823)
//cmdArgs := []string{"-xvz", "-C", files, `--xform=s#.*/\(.*\)#\1#`}
c = exec.Command(cmdName, cmdArgs...)
c.Dir, _ = os.Getwd()
log.Println("[wd:", c.Dir, "]")
c.Stdout = conn
stdErrBuffer := new(bytes.Buffer)
c.Stderr = stdErrBuffer
// 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(2)
} 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())
fmt.Print(stdErrBuffer)
fmt.Printf("Exit Status: %d\n", exitStatus) //#
}
}
}
// send CSOExitStatus to inform remote (server) end cp is done
log.Println("Sending local exitStatus:", exitStatus)
r := make([]byte, 4)
binary.BigEndian.PutUint32(r, exitStatus)
conn.WritePacket(r, hkexnet.CSOExitStatus)
// Do a final read for remote's exit status
s := make([]byte, 4)
_, remErr := conn.Read(s)
if remErr != io.EOF && !strings.Contains(remErr.Error(), "use of closed network") {
fmt.Printf("*** remote status Read() failed: %v\n", remErr)
}
// If local side status was OK, use remote side's status
if exitStatus == 0 {
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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)
var c *exec.Cmd
//os.Clearenv()
//os.Setenv("HOME", u.HomeDir)
//os.Setenv("TERM", "vt102") // TODO: server or client option?
cmdName := "/bin/tar"
destPath := files
cmdArgs := []string{"-xz", "-C", destPath}
log.Printf("[%v %v]\n", cmdName, cmdArgs)
// NOTE the lack of quotes around --xform option's sed expression.
// When args are passed in exec() format, no quoting is required
// (as this isn't input from a shell) (right? -rlm 20180823)
//cmdArgs := []string{"-xvz", "-C", destPath, `--xform=s#.*/\(.*\)#\1#`}
c = exec.Command(cmdName, cmdArgs...)
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)
//log.Fatal(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())
log.Printf("Exit Status: %d", exitStatus)
}
}
}
// return local status, if nonzero;
// otherwise, return remote status if nonzero
if exitStatus == 0 {
exitStatus = uint32(conn.GetStatus())
}
fmt.Printf("*** server->client cp finished, status %d ***\n", conn.GetStatus())
}
}
return
}
// doShellMode begins an hkexsh shell session (one-shot command or interactive).
func doShellMode(isInteractive bool, conn *hkexnet.Conn, oldState *hkexsh.State, rec *hkexsh.Session) {
//client reader (from server) goroutine
//Read remote end's stdout
wg.Add(1)
go func() {
defer wg.Done()
// By deferring a call to wg.Done(),
// each goroutine guarantees that it marks
// its direction's stream as finished.
// io.Copy() expects EOF so normally this will
// exit with inerr == nil
_, inerr := io.Copy(os.Stdout, conn)
if inerr != nil {
_ = hkexsh.Restore(int(os.Stdin.Fd()), oldState) // Best effort.
// 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)
os.Exit(1)
}
}
rec.SetStatus(uint32(conn.GetStatus()))
log.Println("rec.status:", rec.Status)
if isInteractive {
log.Println("[* Got EOF *]")
_ = hkexsh.Restore(int(os.Stdin.Fd()), oldState) // Best effort.
}
}()
// 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)
go func() {
defer wg.Done()
//!defer wg.Done()
// Copy() expects EOF so this will
// exit with outerr == nil
//!_, outerr := io.Copy(conn, os.Stdin)
_, outerr := func(conn *hkexnet.Conn, r io.Reader) (w int64, e error) {
w, e = io.Copy(conn, r)
return w, e
}(conn, os.Stdin)
if outerr != nil {
log.Println(outerr)
fmt.Println(outerr)
_ = hkexsh.Restore(int(os.Stdin.Fd()), oldState) // Best effort.
log.Println("[Hanging up]")
os.Exit(0)
}
}()
}
// 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()
}
func rejectUserMsg() string {
return "Begone, " + spinsult.GetSentence() + "\r\n"
}
// hkexsh - a client for secure shell and file copy operations.
//
// While conforming to the basic net.Conn interface HKex.Conn has extra
// capabilities designed to allow apps to define connection options,
// encryption/hmac settings and operations across the encrypted channel.
//
// Initial setup is the same as using plain net.Dial(), but one may
// specify extra extension tags (strings) to set the cipher and hmac
// setting desired; as well as the intended operation mode for the
// connection (app-specific, passed through to the server to use or
// ignore at its discretion).
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func main() {
version := hkexsh.Version
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var vopt bool
var gopt bool //login via password, asking server to generate authToken
var dbg bool
var shellMode bool // if true act as shell, else file copier
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var cAlg string //cipher alg
var hAlg string //hmac alg
var kAlg string //KEX/KEM alg
var server string
var port uint
var cmdStr string
var copySrc []byte
var copyDst string
var authCookie string
var chaffEnabled bool
var chaffFreqMin uint
var chaffFreqMax uint
var chaffBytesMax uint
var op []byte
isInteractive := false
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flag.BoolVar(&vopt, "v", false, "show version")
flag.BoolVar(&dbg, "d", false, "debug logging")
flag.StringVar(&cAlg, "c", "C_AES_256", "`cipher` [\"C_AES_256\" | \"C_TWOFISH_128\" | \"C_BLOWFISH_64\"]")
flag.StringVar(&hAlg, "m", "H_SHA256", "`hmac` [\"H_SHA256\"]")
flag.StringVar(&kAlg, "k", "KEX_HERRADURA256", "`kex` [\"KEX_HERRADURA{256/512/1024/2048}\" | \"KEX_KYBER{512/768/1024}\"]")
flag.UintVar(&port, "p", 2000, "`port`")
//flag.StringVar(&authCookie, "a", "", "auth cookie")
flag.BoolVar(&chaffEnabled, "e", true, "enabled chaff pkts (default true)")
flag.UintVar(&chaffFreqMin, "f", 100, "chaff pkt `freq` min (msecs)")
flag.UintVar(&chaffFreqMax, "F", 5000, "chaff pkt `freq` max (msecs)")
flag.UintVar(&chaffBytesMax, "B", 64, "chaff pkt `size` max (bytes)")
// Find out what program we are (shell or copier)
myPath := strings.Split(os.Args[0], string(os.PathSeparator))
if myPath[len(myPath)-1] != "hkexcp" && myPath[len(myPath)-1] != "hkexcp.exe" {
// hkexsh accepts a command (-x) but not
// a srcpath (-r) or dstpath (-t)
flag.StringVar(&cmdStr, "x", "", "`command` to run (if not specified run interactive shell)")
flag.BoolVar(&gopt, "g", false, "ask server to generate authtoken")
shellMode = true
flag.Usage = UsageShell
} else {
flag.Usage = UsageCp
}
flag.Parse()
remoteUser, remoteHost, tmpPath, pathIsDest, otherArgs :=
parseNonSwitchArgs(flag.Args())
//fmt.Println("otherArgs:", otherArgs)
// Set defaults if user doesn't specify user, path or port
var uname string
if remoteUser == "" {
u, _ := user.Current()
uname = u.Username
} else {
uname = remoteUser
}
if remoteHost != "" {
server = remoteHost + ":" + fmt.Sprintf("%d", port)
}
if tmpPath == "" {
tmpPath = "."
}
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 more option consistency checks
//fmt.Println("server finally is:", server)
if flag.NFlag() == 0 && server == "" {
flag.Usage()
os.Exit(0)
}
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if vopt {
fmt.Printf("version v%s\n", version)
os.Exit(0)
}
if len(cmdStr) != 0 && (len(copySrc) != 0 || len(copyDst) != 0) {
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
if dbg {
log.SetOutput(os.Stdout)
} else {
log.SetOutput(ioutil.Discard)
}
if !gopt {
// See if we can log in via an auth token
u, _ := user.Current()
ab, aerr := ioutil.ReadFile(fmt.Sprintf("%s/.hkexsh_id", u.HomeDir))
if aerr == nil {
//authCookie = string(ab)
idx := strings.Index(string(ab), remoteHost)
//fmt.Printf("auth entry idx:%d\n", idx)
if idx >= 0 {
fmt.Fprintln(os.Stderr, "[authtoken]")
ab = ab[idx:]
entries := strings.SplitN(string(ab), "\n", -1)
//if len(entries) > 0 {
//fmt.Println("entries[0]:", entries[0])
authCookie = strings.TrimSpace(entries[0])
//} else {
// fmt.Fprintln(os.Stderr, "ERROR: no matching authtoken")
// os.Exit(1)
//}
// Security scrub
ab = nil
runtime.GC()
} else {
fmt.Fprintln(os.Stderr, "[no authtoken, use -g to request one from server]")
}
} else {
log.Printf("[cannot read %s/.hkexsh_id]\n", u.HomeDir)
}
}
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 len(cmdStr) == 0 {
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'}
//fmt.Println("client->server copy:", string(copySrc), "->", copyDst)
cmdStr = copyDst
} else {
// server->client file copy
// remote src file(s) in copyDsr
op = []byte{'S'}
//fmt.Println("server->client copy:", string(copySrc), "->", copyDst)
cmdStr = string(copySrc)
}
}
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conn, err := hkexnet.Dial("tcp", server, cAlg, hAlg, kAlg)
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if err != nil {
fmt.Println(err)
panic(err)
}
defer conn.Close()
// From this point on, conn is a secure encrypted channel
// 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 *hkexsh.State
if shellMode {
if isatty.IsTerminal(os.Stdin.Fd()) {
oldState, err = hkexsh.MakeRaw(int(os.Stdin.Fd()))
if err != nil {
panic(err)
}
defer func() { _ = hkexsh.Restore(int(os.Stdin.Fd()), oldState) }() // Best effort.
} else {
log.Println("NOT A TTY")
}
}
if len(authCookie) == 0 {
//No auth token, prompt for password
fmt.Printf("Gimme cookie:")
ab, err := hkexsh.ReadPassword(int(os.Stdin.Fd()))
fmt.Printf("\r\n")
if err != nil {
panic(err)
}
authCookie = string(ab)
// Security scrub
ab = nil
runtime.GC()
}
// Set up session params and send over to server
rec := hkexsh.NewSession(op, []byte(uname), []byte(remoteHost), []byte(os.Getenv("TERM")), []byte(cmdStr), []byte(authCookie), 0)
_, err = 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)))
_, err = conn.Write(rec.Op())
_, err = conn.Write(rec.Who())
_, err = conn.Write(rec.ConnHost())
_, err = conn.Write(rec.TermType())
_, err = conn.Write(rec.Cmd())
_, err = conn.Write(rec.AuthCookie(true))
//Security scrub
authCookie = ""
runtime.GC()
// Read auth reply from server
authReply := make([]byte, 1) // bool: 0 = fail, 1 = pass
_, err = conn.Read(authReply)
if authReply[0] == 0 {
fmt.Fprintln(os.Stderr, rejectUserMsg())
rec.SetStatus(255)
} else {
// Set up chaffing to server
conn.SetupChaff(chaffFreqMin, chaffFreqMax, chaffBytesMax) // enable client->server chaffing
if chaffEnabled {
conn.EnableChaff()
defer conn.DisableChaff()
defer conn.ShutdownChaff()
}
if shellMode {
doShellMode(isInteractive, &conn, oldState, rec)
} else { // copyMode
_, s := doCopyMode(&conn, pathIsDest, fileArgs, rec)
rec.SetStatus(s)
}
if rec.Status() != 0 {
fmt.Fprintln(os.Stderr, "Session exited with status:", rec.Status())
}
}
if oldState != nil {
_ = hkexsh.Restore(int(os.Stdin.Fd()), oldState) // Best effort.
}
os.Exit(int(rec.Status()))
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}