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xs/xsd/xsd.go

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// xsd server
//
// 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"
"crypto/rand"
"encoding/binary"
"encoding/hex"
"errors"
"flag"
"fmt"
"io"
"log"
"net/http"
"os"
"os/exec"
"os/signal"
"os/user"
"path"
"runtime"
"runtime/pprof"
"strings"
"sync"
"syscall"
"time"
"unsafe"
"blitter.com/go/goutmp"
xs "blitter.com/go/xs"
"blitter.com/go/xs/logger"
"blitter.com/go/xs/xsnet"
"github.com/creack/pty"
)
var (
version string
gitCommit string // set in -ldflags by build
useSysLogin bool
kcpMode string // set to a valid KCP BlockCrypt alg tag to use rather than TCP
// Log - syslog output (with no -d)
Log *logger.Writer
cpuprofile string
memprofile string
)
const (
AuthTokenLen = 64
LoginTimeoutSecs = 30
)
func ioctl(fd, request, argp uintptr) error {
if _, _, e := syscall.Syscall6(syscall.SYS_IOCTL, fd, request, argp, 0, 0, 0); e != 0 {
return e
}
return nil
}
func ptsName(fd uintptr) (string, error) {
var n uintptr
err := ioctl(fd, syscall.TIOCGPTN, uintptr(unsafe.Pointer(&n)))
if err != nil {
return "", err
}
return fmt.Sprintf("/dev/pts/%d", n), nil
}
/* -------------------------------------------------------------- */
// Perform a client->server copy
func runClientToServerCopyAs(who, ttype string, conn *xsnet.Conn, fpath string, chaffing bool) (exitStatus uint32, err error) {
u, _ := user.Lookup(who)
var uid, gid uint32
fmt.Sscanf(u.Uid, "%d", &uid)
fmt.Sscanf(u.Gid, "%d", &gid)
log.Println("uid:", uid, "gid:", gid)
// Need to clear server's env and set key vars of the
// target user.
os.Clearenv()
os.Setenv("HOME", u.HomeDir)
os.Setenv("TERM", ttype)
os.Setenv("XS_SESSION", "1")
var c *exec.Cmd
cmdName := xs.GetTool("tar")
var destDir string
if path.IsAbs(fpath) {
destDir = fpath
} else {
destDir = path.Join(u.HomeDir, fpath)
}
cmdArgs := []string{"-xz", "-C", destDir}
// 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{"-x", "-C", destDir, `--xform=s#.*/\(.*\)#\1#`}
fmt.Println(cmdName, cmdArgs)
c = exec.Command(cmdName, cmdArgs...)
c.Dir = destDir
//If os.Clearenv() isn't called by server above these will be seen
//in the client's session env.
//c.Env = []string{"HOME=" + u.HomeDir, "SUDO_GID=", "SUDO_UID=",
// "SUDO_USER=", "SUDO_COMMAND=", "MAIL=", "LOGNAME="+who}
//c.Dir = u.HomeDir
c.SysProcAttr = &syscall.SysProcAttr{}
c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
c.Stdin = conn
c.Stdout = os.Stdout
c.Stderr = os.Stderr
// === Set up connection keepalive to client
conn.StartupKeepAlive() // goroutine, returns immediately
defer conn.ShutdownKeepAlive()
if chaffing {
conn.StartupChaff()
}
defer conn.ShutdownChaff()
// Start the command (no pty)
log.Printf("[%v %v]\n", cmdName, cmdArgs)
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 {
log.Println("cmd exited immediately. Cannot get cmd.Wait().ExitStatus()")
err = errors.New("cmd exited prematurely")
//exitStatus = uint32(254)
exitStatus = xsnet.CSEExecFail
} else {
if err := c.Wait(); err != nil {
//fmt.Println("*** c.Wait() done ***")
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())
//err = errors.New("cmd returned nonzero status")
log.Printf("Exit Status: %d\n", exitStatus)
}
}
}
log.Println("*** client->server cp finished ***")
}
return
}
// Perform a server->client copy
func runServerToClientCopyAs(who, ttype string, conn *xsnet.Conn, srcPath string, chaffing bool) (exitStatus uint32, err error) {
u, err := user.Lookup(who)
if err != nil {
exitStatus = 1
return
}
var uid, gid uint32
_, _ = fmt.Sscanf(u.Uid, "%d", &uid)
_, _ = fmt.Sscanf(u.Gid, "%d", &gid)
log.Println("uid:", uid, "gid:", gid)
// Need to clear server's env and set key vars of the
// target user.
os.Clearenv()
_ = os.Setenv("HOME", u.HomeDir)
_ = os.Setenv("TERM", ttype)
_ = os.Setenv("XS_SESSION", "1")
var c *exec.Cmd
cmdName := xs.GetTool("tar")
if !path.IsAbs(srcPath) {
srcPath = fmt.Sprintf("%s%c%s", u.HomeDir, os.PathSeparator, srcPath)
}
srcDir, srcBase := path.Split(srcPath)
cmdArgs := []string{"-cz", "-C", srcDir, "-f", "-", srcBase}
c = exec.Command(cmdName, cmdArgs...)
//If os.Clearenv() isn't called by server above these will be seen
//in the client's session env.
//c.Env = []string{"HOME=" + u.HomeDir, "SUDO_GID=", "SUDO_UID=", "SUDO_USER=",
// "SUDO_COMMAND=", "MAIL=", "LOGNAME="+who}
c.Dir = u.HomeDir
c.SysProcAttr = &syscall.SysProcAttr{}
c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
c.Stdout = conn
// Stderr sinkholing (or buffering to something other than stdout)
// is important. Any extraneous output to tarpipe messes up remote
// side as it's expecting pure tar data.
// (For example, if user specifies abs paths, tar outputs
// "Removing leading '/' from path names")
stdErrBuffer := new(bytes.Buffer)
c.Stderr = stdErrBuffer
//c.Stderr = nil
// === Set up connection keepalive to client
conn.StartupKeepAlive() // goroutine, returns immediately
defer conn.ShutdownKeepAlive()
if chaffing {
conn.StartupChaff()
}
//defer conn.Close()
defer conn.ShutdownChaff()
// Start the command (no pty)
log.Printf("[%v %v]\n", cmdName, cmdArgs)
err = c.Start() // returns immediately
if err != nil {
log.Printf("Command finished with error: %v", err)
return xsnet.CSEExecFail, err // !?
}
if err := c.Wait(); err != nil {
//fmt.Println("*** c.Wait() done ***")
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 len(stdErrBuffer.Bytes()) > 0 {
log.Print(stdErrBuffer)
}
log.Printf("Exit Status: %d", exitStatus)
}
}
}
//fmt.Println("*** server->client cp finished ***")
return
}
// Run a command (via default shell) as a specific user. Uses
// ptys to support commands which expect a terminal. //nolint:gofmt
func runShellAs(who, hname, ttype, cmd string, interactive bool, //nolint:funlen
conn *xsnet.Conn, chaffing bool) (exitStatus uint32, err error) {
var wg sync.WaitGroup
u, err := user.Lookup(who)
if err != nil {
exitStatus = 1
return
}
var uid, gid uint32
_, _ = fmt.Sscanf(u.Uid, "%d", &uid)
_, _ = fmt.Sscanf(u.Gid, "%d", &gid)
log.Println("uid:", uid, "gid:", gid)
// Need to clear server's env and set key vars of the
// target user.
os.Clearenv()
_ = os.Setenv("HOME", u.HomeDir)
_ = os.Setenv("TERM", ttype)
_ = os.Setenv("XS_SESSION", "1")
var c *exec.Cmd
if interactive {
if useSysLogin {
// Use the server's login binary (post-auth)
//
// Things UNIX login does, like print the 'motd',
// and use the shell specified by /etc/passwd, will be done
// automagically, at the cost of another external tool
// dependency.
//
// One drawback of using 'login' is that the remote side
// cannot give us back the shell's exit code, since it
// exits back to 'login', which usually returns its own
// 0 status back to us.
//
// Note login will drop privs to the intended user for us.
//
c = exec.Command(xs.GetTool("login"), "-f", "-p", who) //nolint:gosec
} else {
// Run shell directly (which allows nonzero exit codes back to
// the local system upon shell exit, whereas 'login' does not.)
//
// Note we must drop privs ourselves for the user shell since
// we aren't using 'login' on the remote end which would do it
// for us.
//
c = exec.Command(xs.GetTool("bash"), "-i", "-l") //nolint:gosec
c.SysProcAttr = &syscall.SysProcAttr{}
c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
}
} else {
c = exec.Command(xs.GetTool("bash"), "-c", cmd) //nolint:gosec
c.SysProcAttr = &syscall.SysProcAttr{}
c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
}
//If os.Clearenv() isn't called by server above these will be seen
//in the client's session env.
//c.Env = []string{"HOME=" + u.HomeDir, "SUDO_GID=", "SUDO_UID=",
// "SUDO_USER=", "SUDO_COMMAND=", "MAIL=", "LOGNAME="+who}
c.Dir = u.HomeDir
// Start the command with a pty.
ptmx, err := pty.Start(c) // returns immediately with ptmx file
if err != nil {
log.Println(err)
return xsnet.CSEPtyExecFail, err
}
// Make sure to close the pty at the end.
// #gv:s/label=\"runShellAs\$1\"/label=\"deferPtmxClose\"/
defer func() {
//logger.LogDebug(fmt.Sprintf("[Exited process was %d]", c.Process.Pid))
_ = ptmx.Close()
}()
// get pty info for system accounting (who, lastlog)
pts, pe := ptsName(ptmx.Fd())
if pe != nil {
return xsnet.CSEPtyGetNameFail, err
}
utmpx := goutmp.Put_utmp(who, pts, hname)
defer func() { goutmp.Unput_utmp(utmpx) }()
goutmp.Put_lastlog_entry("xs", who, pts, hname)
conn.Pproc = c.Process.Pid
//fmt.Printf("[process %d started]\n", c.Process.Pid)
log.Printf("[%s]\n", cmd)
if err != nil {
log.Printf("Command finished with error: %v", err)
} else {
// Watch for term resizes
// #gv:s/label=\"runShellAs\$2\"/label=\"termResizeWatcher\"/
go func() {
for sz := range conn.WinCh {
log.Printf("[Setting term size to: %v %v]\n", sz.Rows, sz.Cols)
pty.Setsize(ptmx, &pty.Winsize{Rows: sz.Rows, Cols: sz.Cols}) //nolint:errcheck
}
log.Println("*** WinCh goroutine done ***")
}()
// Copy stdin to the pty.. (bgnd goroutine)
// #gv:s/label=\"runShellAs\$3\"/label=\"stdinToPtyWorker\"/
go func() {
_, e := io.Copy(ptmx, conn)
if e != nil {
log.Println("** stdin->pty ended **:", e.Error())
} else {
log.Println("*** stdin->pty goroutine done ***")
}
}()
// === Set up connection keepalive to client
conn.StartupKeepAlive() // goroutine, returns immediately
defer conn.ShutdownKeepAlive()
if chaffing {
conn.StartupChaff()
}
// #gv:s/label=\"runShellAs\$4\"/label=\"deferChaffShutdown\"/
defer func() {
conn.ShutdownChaff()
}()
// ..and the pty to stdout.
// This may take some time exceeding that of the
// actual command's lifetime, so the c.Wait() below
// must synchronize with the completion of this goroutine
// to ensure all stdout data gets to the client before
// connection is closed.
wg.Add(1)
// #gv:s/label=\"runShellAs\$5\"/label=\"ptyToStdoutWorker\"/
go func() {
defer wg.Done()
_, e := io.Copy(conn, ptmx)
if e != nil {
log.Println("** pty->stdout ended **:", e.Error())
} else {
// The above io.Copy() will exit when the command attached
// to the pty exits
log.Println("*** pty->stdout goroutine done ***")
}
}()
if err := c.Wait(); err != nil {
//fmt.Println("*** c.Wait() done ***")
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)
}
}
conn.SetStatus(xsnet.CSOType(exitStatus))
} else {
logger.LogDebug(fmt.Sprintf("*** Main proc has exited (%d) ***", c.ProcessState.ExitCode())) //nolint:errcheck
// Background jobs still may be running; close the
// pty anyway, so the client can return before
// wg.Wait() below completes (Issue #18)
if interactive {
_ = ptmx.Close()
}
}
wg.Wait() // Wait on pty->stdout completion to client
}
return
}
// GenAuthToken generates a pseudorandom auth token for a specific
// user from a specific host to allow non-interactive logins.
func GenAuthToken(who string, connhost string) string {
//hname, e := os.Hostname()
//if e != nil {
// hname = "#badhost#"
//}
hname := connhost
token := make([]byte, AuthTokenLen)
_, _ = rand.Read(token)
return fmt.Sprintf("%s:%s:%s", hname, who, hex.EncodeToString(token))
}
var (
aKEXAlgs allowedKEXAlgs
aCipherAlgs allowedCipherAlgs
aHMACAlgs allowedHMACAlgs
)
type allowedKEXAlgs []string
type allowedCipherAlgs []string
type allowedHMACAlgs []string
func (a allowedKEXAlgs) allowed(k xsnet.KEXAlg) bool {
for i := 0; i < len(a); i++ {
if a[i] == "KEX_all" || a[i] == k.String() {
return true
}
}
return false
}
func (a *allowedKEXAlgs) String() string {
return fmt.Sprintf("allowedKEXAlgs: %v", *a)
}
func (a *allowedKEXAlgs) Set(value string) error {
*a = append(*a, strings.TrimSpace(value))
return nil
}
func (a allowedCipherAlgs) allowed(c xsnet.CSCipherAlg) bool {
for i := 0; i < len(a); i++ {
if a[i] == "C_all" || a[i] == c.String() {
return true
}
}
return false
}
func (a *allowedCipherAlgs) String() string {
return fmt.Sprintf("allowedCipherAlgs: %v", *a)
}
func (a *allowedCipherAlgs) Set(value string) error {
*a = append(*a, strings.TrimSpace(value))
return nil
}
func (a allowedHMACAlgs) allowed(h xsnet.CSHmacAlg) bool {
for i := 0; i < len(a); i++ {
if a[i] == "H_all" || a[i] == h.String() {
return true
}
}
return false
}
func (a *allowedHMACAlgs) String() string {
return fmt.Sprintf("allowedHMACAlgs: %v", *a)
}
func (a *allowedHMACAlgs) Set(value string) error {
*a = append(*a, strings.TrimSpace(value))
return nil
}
// Main server that listens and spawns goroutines for each
// connecting client to serve interactive or file copy sessions
// and any requested tunnels.
// Note that this server does not do UNIX forks of itself to give
// each client its own separate manager process, so if the main
// daemon dies, all clients will be rudely disconnected.
// Consider this when planning to restart or upgrade in-place an installation.
// TODO: reduce gocyclo
func main() { //nolint:funlen,gocyclo
var vopt bool
var chaffEnabled bool
var chaffFreqMin uint
var chaffFreqMax uint
var chaffBytesMax uint
var dbg bool
var laddr string
var rekeySecs uint
var remodSupported bool // true: when rekeying, switch to random cipher/hmac alg
var useSystemPasswd bool
flag.BoolVar(&vopt, "v", false, "show version")
flag.UintVar(&rekeySecs, "r", 300, "rekey interval in `secs`")
flag.BoolVar(&remodSupported, "R", false, "Borg Countermeasures (remodulate cipher/hmac alg on each rekey)")
flag.StringVar(&laddr, "l", ":2000", "interface[:port] to listen") //nolint:gomnd,lll
flag.StringVar(&kcpMode, "K", "unused", `set to 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.BoolVar(&useSysLogin, "L", false, "use system login")
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.BoolVar(&useSystemPasswd, "s", true, "use system shadow passwds")
flag.BoolVar(&dbg, "d", false, "debug logging")
flag.Var(&aKEXAlgs, "aK", "Allowed KEX `alg`s (eg. '-aK KEXAlgA -aK KEXAlgB ...')"+`
KEX_all
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.Var(&aCipherAlgs, "aC", "Allowed `cipher`s (eg. '-aC CAlgA -aC CAlgB ...')"+`
C_all
C_AES_256
C_TWOFISH_128
C_BLOWFISH_64
C_CRYPTMT1
C_HOPSCOTCH
C_CHACHA20_12`)
flag.Var(&aHMACAlgs, "aH", "Allowed `HMAC`s (eg. '-aH HMACAlgA -aH HMACAlgB ...')"+`
H_all
H_SHA256
H_SHA512`)
flag.StringVar(&cpuprofile, "cpuprofile", "", "write cpu profile to <`file`>")
flag.StringVar(&memprofile, "memprofile", "", "write memory profile to <`file`>")
flag.Parse()
if vopt {
fmt.Printf("version %s (%s)\n", version, gitCommit)
os.Exit(0)
}
{
me, e := user.Current()
if e != nil || me.Uid != "0" {
log.Fatal("Must run as root.")
}
}
// === 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
}
// 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
}
Log, _ = logger.New(logger.LOG_DAEMON|logger.LOG_DEBUG|logger.LOG_NOTICE|logger.LOG_ERR, "xsd")
xsnet.Init(dbg, "xsd", logger.LOG_DAEMON|logger.LOG_DEBUG|logger.LOG_NOTICE|logger.LOG_ERR)
if dbg {
log.SetOutput(Log)
} else {
log.SetOutput(io.Discard)
}
// Set up allowed algs, if specified (default allow all)
if len(aKEXAlgs) == 0 {
aKEXAlgs = []string{"none"}
}
logger.LogNotice(fmt.Sprintf("Allowed KEXAlgs: %v\n", aKEXAlgs)) //nolint:errcheck
if len(aCipherAlgs) == 0 {
aCipherAlgs = []string{"none"}
}
logger.LogNotice(fmt.Sprintf("Allowed CipherAlgs: %v\n", aCipherAlgs)) //nolint:errcheck
if len(aHMACAlgs) == 0 {
aHMACAlgs = []string{"none"}
}
logger.LogNotice(fmt.Sprintf("Allowed HMACAlgs: %v\n", aHMACAlgs)) //nolint:errcheck
// Set up handler for daemon signalling
exitCh := make(chan os.Signal, 1)
signal.Notify(exitCh, os.Signal(syscall.SIGTERM), os.Signal(syscall.SIGINT), os.Signal(syscall.SIGHUP), os.Signal(syscall.SIGUSR1), os.Signal(syscall.SIGUSR2)) //nolint:lll
go func() {
for {
sig := <-exitCh
switch sig {
case syscall.SIGTERM: //"terminated":
logger.LogNotice(fmt.Sprintf("[Got signal: %s]", sig.String())) //nolint:errcheck
signal.Reset()
syscall.Kill(0, syscall.SIGTERM) //nolint:errcheck
case syscall.SIGINT: //"interrupt":
logger.LogNotice(fmt.Sprintf("[Got signal: %s]", sig.String())) //nolint:errcheck
signal.Reset()
syscall.Kill(0, syscall.SIGINT) //nolint:errcheck
case syscall.SIGHUP: //"hangup":
logger.LogNotice(fmt.Sprintf("[Got signal: %s - nop]", sig.String())) //nolint:errcheck
if cpuprofile != "" || memprofile != "" {
dumpProf()
}
default:
logger.LogNotice(fmt.Sprintf("[Got signal: %s - ignored]", sig.String())) //nolint:errcheck
}
}
}()
proto := "tcp"
if kcpMode != "unused" {
proto = "kcp"
}
l, err := xsnet.Listen(proto, laddr, kcpMode)
if err != nil {
log.Fatal(err)
}
defer l.Close()
log.Println("Serving on", laddr)
for {
// Wait for a connection.
// Then check if client-proposed algs are allowed
conn, err := l.Accept()
//logger.LogDebug(fmt.Sprintf("l.Accept()\n"))
if err != nil {
log.Printf("Accept() got error(%v), hanging up.\n", err)
} else {
if !aKEXAlgs.allowed(conn.KEX()) {
log.Printf("Accept() rejected for banned KEX alg %d, hanging up.\n", conn.KEX())
conn.SetStatus(xsnet.CSEKEXAlgDenied)
conn.Close()
} else if !aCipherAlgs.allowed(conn.CAlg()) {
log.Printf("Accept() rejected for banned Cipher alg %d, hanging up.\n", conn.CAlg())
conn.SetStatus(xsnet.CSECipherAlgDenied)
conn.Close()
} else if !aHMACAlgs.allowed(conn.HAlg()) {
log.Printf("Accept() rejected for banned HMAC alg %d, hanging up.\n", conn.HAlg())
conn.SetStatus(xsnet.CSEHMACAlgDenied)
conn.Close()
} else {
log.Println("Accepted client")
// Only enable cipher alg changes on re-key if we were told
// to support it (launching xsd with -R), *and* the client
// proposes to use it.
if !remodSupported {
if (conn.Opts() & xsnet.CORemodulateShields) != 0 {
logger.LogDebug("[client proposed cipher/hmac remod, but we don't support it.]")
conn.Close()
continue
}
} else {
if conn.Opts()&xsnet.CORemodulateShields != 0 {
logger.LogDebug("[cipher/hmac remodulation active]")
} else {
logger.LogDebug("[cipher/hmac remodulation inactive]")
}
}
conn.RekeyHelper(rekeySecs)
// Set up chaffing to client
// Will only start when runShellAs() is called
// after stdin/stdout are hooked up
conn.SetupChaff(chaffFreqMin, chaffFreqMax, chaffBytesMax) // configure server->client chaffing
// Handle the connection in a new goroutine.
// The loop then returns to accepting, so that
// multiple connections may be served concurrently.
go func(hc *xsnet.Conn) (e error) {
defer hc.ShutdownRekey()
defer hc.Close()
// Start login timeout here and disconnect if user/pass phase stalls
loginTimeout := time.AfterFunc(LoginTimeoutSecs*time.Second, func() {
logger.LogNotice(fmt.Sprintln("Login timed out")) //nolint:errcheck
hc.Write([]byte{0}) //nolint:errcheck
hc.Close()
})
//We use io.ReadFull() here to guarantee we consume
//just the data we want for the xs.Session, and no more.
//Otherwise data will be sitting in the channel that isn't
//passed down to the command handlers.
var rec xs.Session
var len1, len2, len3, len4, len5, len6 uint32
n, err := fmt.Fscanf(hc, "%d %d %d %d %d %d\n", &len1, &len2, &len3, &len4, &len5, &len6)
log.Printf("xs.Session read:%d %d %d %d %d %d\n", len1, len2, len3, len4, len5, len6)
if err != nil || n < 6 {
log.Println("[Bad xs.Session fmt]")
return err
}
tmp := make([]byte, len1)
_, err = io.ReadFull(hc, tmp)
if err != nil {
log.Println("[Bad xs.Session.Op]")
return err
}
rec.SetOp(tmp)
tmp = make([]byte, len2)
_, err = io.ReadFull(hc, tmp)
if err != nil {
log.Println("[Bad xs.Session.Who]")
return err
}
rec.SetWho(tmp)
tmp = make([]byte, len3)
_, err = io.ReadFull(hc, tmp)
if err != nil {
log.Println("[Bad xs.Session.ConnHost]")
return err
}
rec.SetConnHost(tmp)
tmp = make([]byte, len4)
_, err = io.ReadFull(hc, tmp)
if err != nil {
log.Println("[Bad xs.Session.TermType]")
return err
}
rec.SetTermType(tmp)
tmp = make([]byte, len5)
_, err = io.ReadFull(hc, tmp)
if err != nil {
log.Println("[Bad xs.Session.Cmd]")
return err
}
rec.SetCmd(tmp)
tmp = make([]byte, len6)
_, err = io.ReadFull(hc, tmp)
if err != nil {
log.Println("[Bad xs.Session.AuthCookie]")
return err
}
rec.SetAuthCookie(tmp)
log.Printf("[xs.Session: op:%c who:%s connhost:%s cmd:%s auth:****]\n",
rec.Op()[0], string(rec.Who()), string(rec.ConnHost()), string(rec.Cmd()))
var valid bool
var allowedCmds string // Currently unused
if xs.AuthUserByToken(xs.NewAuthCtx(), string(rec.Who()), string(rec.ConnHost()), string(rec.AuthCookie(true))) {
valid = true
} else {
if useSystemPasswd {
//var passErr error
valid, _ /*passErr*/ = xs.VerifyPass(xs.NewAuthCtx(), string(rec.Who()), string(rec.AuthCookie(true)))
} else {
valid, allowedCmds = xs.AuthUserByPasswd(xs.NewAuthCtx(), string(rec.Who()), string(rec.AuthCookie(true)), "/etc/xs.passwd")
}
}
_ = loginTimeout.Stop()
// Security scrub
rec.ClearAuthCookie()
// Tell client if auth was valid
if valid {
hc.Write([]byte{1}) //nolint:errcheck
} else {
logger.LogNotice(fmt.Sprintln("Invalid user", string(rec.Who()))) //nolint:errcheck
hc.Write([]byte{0}) //nolint:errcheck
return
}
log.Printf("[allowedCmds:%s]\n", allowedCmds)
if rec.Op()[0] == 'A' {
// Generate automated login token
addr := hc.RemoteAddr()
hname := goutmp.GetHost(addr.String())
logger.LogNotice(fmt.Sprintf("[Generating autologin token for [%s@%s]]\n", rec.Who(), hname)) //nolint:errcheck
token := GenAuthToken(string(rec.Who()), string(rec.ConnHost()))
tokenCmd := fmt.Sprintf("echo %q | tee -a ~/.xs_id", token)
cmdStatus, runErr := runShellAs(string(rec.Who()), hname, string(rec.TermType()), tokenCmd, false, hc, chaffEnabled)
// Returned hopefully via an EOF or exit/logout;
// Clear current op so user can enter next, or EOF
rec.SetOp([]byte{0})
if runErr != nil {
logger.LogErr(fmt.Sprintf("[Error generating autologin token for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
} else {
log.Printf("[Autologin token generation completed for %s@%s, status %d]\n", rec.Who(), hname, cmdStatus)
hc.SetStatus(xsnet.CSOType(cmdStatus))
}
} else if rec.Op()[0] == 'c' {
// Non-interactive command
addr := hc.RemoteAddr()
hname := goutmp.GetHost(addr.String())
logger.LogNotice(fmt.Sprintf("[Running command for [%s@%s]]\n", rec.Who(), hname)) //nolint:errcheck
cmdStatus, runErr := runShellAs(string(rec.Who()), hname, string(rec.TermType()), string(rec.Cmd()), false, hc, chaffEnabled)
// Returned hopefully via an EOF or exit/logout;
// Clear current op so user can enter next, or EOF
rec.SetOp([]byte{0})
if runErr != nil {
logger.LogErr(fmt.Sprintf("[Error spawning cmd for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
} else {
logger.LogNotice(fmt.Sprintf("[Command completed for %s@%s, status %d]\n", rec.Who(), hname, cmdStatus)) //nolint:errcheck
hc.SetStatus(xsnet.CSOType(cmdStatus))
}
} else if rec.Op()[0] == 's' {
// Interactive session
addr := hc.RemoteAddr()
hname := goutmp.GetHost(addr.String())
logger.LogNotice(fmt.Sprintf("[Running shell for [%s@%s]]\n", rec.Who(), hname)) //nolint:errcheck
cmdStatus, runErr := runShellAs(string(rec.Who()), hname, string(rec.TermType()), string(rec.Cmd()), true, hc, chaffEnabled)
// Returned hopefully via an EOF or exit/logout;
// Clear current op so user can enter next, or EOF
rec.SetOp([]byte{0})
if runErr != nil {
Log.Err(fmt.Sprintf("[Error spawning shell for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
} else {
logger.LogNotice(fmt.Sprintf("[Shell completed for %s@%s, status %d]\n", rec.Who(), hname, cmdStatus)) //nolint:errcheck
hc.SetStatus(xsnet.CSOType(cmdStatus))
}
} else if rec.Op()[0] == 'D' {
// File copy (destination) operation - client copy to server
log.Printf("[Client->Server copy]\n")
addr := hc.RemoteAddr()
hname := goutmp.GetHost(addr.String())
logger.LogNotice(fmt.Sprintf("[c->s copy for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
cmdStatus, runErr := runClientToServerCopyAs(string(rec.Who()), string(rec.TermType()), hc, string(rec.Cmd()), chaffEnabled)
// Returned hopefully via an EOF or exit/logout;
// Clear current op so user can enter next, or EOF
rec.SetOp([]byte{0})
if runErr != nil {
logger.LogErr(fmt.Sprintf("[c->s copy error for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
} else {
logger.LogNotice(fmt.Sprintf("[c->s copy completed for %s@%s, status %d]\n", rec.Who(), hname, cmdStatus)) //nolint:errcheck
}
// TODO: Test this with huge files.. see Bug #22 - do we need to
// sync w/sender (client) that we've gotten all data?
hc.SetStatus(xsnet.CSOType(cmdStatus))
// Send CSOExitStatus *before* client closes channel
s := make([]byte, 4) //nolint:gomnd
binary.BigEndian.PutUint32(s, cmdStatus)
log.Printf("** cp writing closeStat %d at Close()\n", cmdStatus)
hc.WritePacket(s, xsnet.CSOExitStatus) //nolint:errcheck
} else if rec.Op()[0] == 'S' {
// File copy (src) operation - server copy to client
log.Printf("[Server->Client copy]\n")
addr := hc.RemoteAddr()
hname := goutmp.GetHost(addr.String())
logger.LogNotice(fmt.Sprintf("[s->c copy for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
cmdStatus, runErr := runServerToClientCopyAs(string(rec.Who()), string(rec.TermType()), hc, string(rec.Cmd()), chaffEnabled)
if runErr != nil {
logger.LogErr(fmt.Sprintf("[s->c copy error for %s@%s]\n", rec.Who(), hname)) //nolint:errcheck
} else {
// Returned hopefully via an EOF or exit/logout;
logger.LogNotice(fmt.Sprintf("[s->c copy completed for %s@%s, status %d]\n", rec.Who(), hname, cmdStatus)) //nolint:errcheck
}
// Clear current op so user can enter next, or EOF
rec.SetOp([]byte{0})
hc.SetStatus(xsnet.CSOType(cmdStatus))
//fmt.Println("Waiting for EOF from other end.")
//_, _ = hc.Read(nil /*ackByte*/)
//fmt.Println("Got remote end ack.")
} else {
logger.LogErr(fmt.Sprintln("[Bad xs.Session]")) //nolint:errcheck
}
return
}(&conn) //nolint:errcheck
} // algs valid and not blacklisted
} // Accept() success
} //endfor
//logger.LogNotice(fmt.Sprintln("[Exiting]")) //nolint:errcheck
}
func dumpProf() {
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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