mirror of https://gogs.blitter.com/RLabs/xs
254 lines
6.7 KiB
Go
254 lines
6.7 KiB
Go
package main
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import (
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"flag"
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"fmt"
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"io"
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"io/ioutil"
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"log"
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"os"
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"os/exec"
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"os/user"
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"syscall"
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hkex "blitter.com/hkexsh"
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"blitter.com/hkexsh/demo/spinsult"
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"github.com/kr/pty"
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)
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type cmdSpec struct {
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op []byte
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who []byte
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cmd []byte
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authCookie []byte
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status int
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}
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/* -------------------------------------------------------------- */
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/*
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// Run a command (via os.exec) as a specific user
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//
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// Uses ptys to support commands which expect a terminal.
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func runCmdAs(who string, cmd string, conn hkex.Conn) (err error) {
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u, _ := user.Lookup(who)
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var uid, gid uint32
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fmt.Sscanf(u.Uid, "%d", &uid)
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fmt.Sscanf(u.Gid, "%d", &gid)
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fmt.Println("uid:", uid, "gid:", gid)
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args := strings.Split(cmd, " ")
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arg0 := args[0]
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args = args[1:]
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c := exec.Command(arg0, args...)
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c.SysProcAttr = &syscall.SysProcAttr{}
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c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
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c.Stdin = conn
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c.Stdout = conn
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c.Stderr = conn
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// Start the command with a pty.
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ptmx, err := pty.Start(c) // returns immediately with ptmx file
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if err != nil {
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return err
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}
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// Make sure to close the pty at the end.
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defer func() { _ = ptmx.Close() }() // Best effort.
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// Copy stdin to the pty and the pty to stdout.
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go func() { _, _ = io.Copy(ptmx, conn) }()
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_, _ = io.Copy(conn, ptmx)
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//err = c.Run() // returns when c finishes.
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if err != nil {
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log.Printf("Command finished with error: %v", err)
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log.Printf("[%s]\n", cmd)
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}
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return
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}
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*/
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// Run a command (via default shell) as a specific user
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//
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// Uses ptys to support commands which expect a terminal.
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func runShellAs(who string, cmd string, interactive bool, conn hkex.Conn) (err error) {
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u, _ := user.Lookup(who)
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var uid, gid uint32
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fmt.Sscanf(u.Uid, "%d", &uid)
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fmt.Sscanf(u.Gid, "%d", &gid)
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log.Println("uid:", uid, "gid:", gid)
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// Need to clear server's env and set key vars of the
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// target user. This isn't perfect (TERM doesn't seem to
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// work 100%; ANSI/xterm colour isn't working even
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// if we set "xterm" or "ansi" here; and line count
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// reported by 'stty -a' defaults to 24 regardless
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// of client shell window used to run client.
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// Investigate -- rlm 2018-01-26)
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os.Clearenv()
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os.Setenv("HOME", u.HomeDir)
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os.Setenv("TERM", "vt102") // TODO: server or client option?
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var c *exec.Cmd
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if interactive {
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c = exec.Command("/bin/bash", "-i", "-l")
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} else {
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c = exec.Command("/bin/bash", "-c", cmd)
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}
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//If os.Clearenv() isn't called by server above these will be seen in the
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//client's session env.
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//c.Env = []string{"HOME=" + u.HomeDir, "SUDO_GID=", "SUDO_UID=", "SUDO_USER=", "SUDO_COMMAND=", "MAIL=", "LOGNAME="+who}
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c.Dir = u.HomeDir
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c.SysProcAttr = &syscall.SysProcAttr{}
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c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
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c.Stdin = conn
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c.Stdout = conn
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c.Stderr = conn
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// Start the command with a pty.
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ptmx, err := pty.Start(c) // returns immediately with ptmx file
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if err != nil {
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return err
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}
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// Make sure to close the pty at the end.
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defer func() { _ = ptmx.Close() }() // Best effort.
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// Copy stdin to the pty.. (bgnd goroutine)
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go func() {
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_, _ = io.Copy(ptmx, conn)
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}()
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// ..and the pty to stdout.
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_, _ = io.Copy(conn, ptmx)
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//err = c.Run() // returns when c finishes.
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if err != nil {
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log.Printf("Command finished with error: %v", err)
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log.Printf("[%s]\n", cmd)
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}
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return
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}
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func rejectUserMsg() string {
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return "Begone, " + spinsult.GetSentence() + "\r\n"
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}
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// Demo of a simple server that listens and spawns goroutines for each
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// connecting client. Note this code is identical to standard tcp
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// server code, save for declaring 'hkex' rather than 'net'
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// Listener and Conns. The KEx and encrypt/decrypt is done within the type.
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// Compare to 'serverp.go' in this directory to see the equivalence.
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func main() {
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var dbg bool
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var laddr string
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flag.StringVar(&laddr, "l", ":2000", "interface[:port] to listen")
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flag.BoolVar(&dbg, "d", false, "debug logging")
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flag.Parse()
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if dbg {
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log.SetOutput(os.Stdout)
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} else {
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log.SetOutput(ioutil.Discard)
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}
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// Listen on TCP port 2000 on all available unicast and
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// anycast IP addresses of the local system.
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l, err := hkex.Listen("tcp", laddr)
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if err != nil {
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log.Fatal(err)
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}
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defer l.Close()
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log.Println("Serving on", laddr)
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for {
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// Wait for a connection.
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conn, err := l.Accept()
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Accepted client")
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// Handle the connection in a new goroutine.
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// The loop then returns to accepting, so that
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// multiple connections may be served concurrently.
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go func(c hkex.Conn) (e error) {
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defer c.Close()
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//We use io.ReadFull() here to guarantee we consume
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//just the data we want for the cmdSpec, and no more.
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//Otherwise data will be sitting in the channel that isn't
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//passed down to the command handlers.
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var rec cmdSpec
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var len1, len2, len3, len4 uint32
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n, err := fmt.Fscanf(c, "%d %d %d %d\n", &len1, &len2, &len3, &len4)
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log.Printf("cmdSpec read:%d %d %d %d\n", len1, len2, len3, len4)
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if err != nil || n < 4 {
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log.Println("[Bad cmdSpec fmt]")
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return err
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}
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//fmt.Printf(" lens:%d %d %d %d\n", len1, len2, len3, len4)
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rec.op = make([]byte, len1, len1)
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_, err = io.ReadFull(c, rec.op)
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if err != nil {
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log.Println("[Bad cmdSpec.op]")
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return err
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}
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rec.who = make([]byte, len2, len2)
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_, err = io.ReadFull(c, rec.who)
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if err != nil {
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log.Println("[Bad cmdSpec.who]")
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return err
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}
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rec.cmd = make([]byte, len3, len3)
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_, err = io.ReadFull(c, rec.cmd)
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if err != nil {
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log.Println("[Bad cmdSpec.cmd]")
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return err
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}
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rec.authCookie = make([]byte, len4, len4)
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_, err = io.ReadFull(c, rec.authCookie)
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if err != nil {
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log.Println("[Bad cmdSpec.authCookie]")
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return err
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}
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log.Printf("[cmdSpec: op:%c who:%s cmd:%s auth:****]\n",
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rec.op[0], string(rec.who), string(rec.cmd))
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valid, allowedCmds := hkex.AuthUser(string(rec.who), string(rec.authCookie), "/etc/hkexsh.passwd")
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if !valid {
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log.Println("Invalid user", string(rec.who))
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c.Write([]byte(rejectUserMsg()))
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return
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}
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log.Printf("[allowedCmds:%s]\n", allowedCmds)
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if rec.op[0] == 'c' {
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// Non-interactive command
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log.Println("[Running command]")
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runShellAs(string(rec.who), string(rec.cmd), false, conn)
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// Returned hopefully via an EOF or exit/logout;
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// Clear current op so user can enter next, or EOF
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rec.op[0] = 0
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log.Println("[Command complete]")
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} else if rec.op[0] == 's' {
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log.Println("[Running shell]")
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runShellAs(string(rec.who), string(rec.cmd), true, conn)
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// Returned hopefully via an EOF or exit/logout;
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// Clear current op so user can enter next, or EOF
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rec.op[0] = 0
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log.Println("[Exiting shell]")
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} else {
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log.Println("[Bad cmdSpec]")
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}
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return
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}(conn)
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} //endfor
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log.Println("[Exiting]")
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}
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