xs/demo/server/server.go

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package main
import (
"flag"
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"fmt"
"log"
"os/exec"
"os/user"
"strings"
"syscall"
"time"
hkex "blitter.com/herradurakex"
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)
const (
OpR = 'r' // read(file) (binary mode)
OpW = 'w' // (over)write
OpA = 'a' // append
OpRm = 'd' // rm
OpRmD = 'D' // rmdir (rm -rf)
OpM = 'm' // mkdir (-p)
OpN = 'n' // re(n)ame (mv)
OpCm = 'c' // chmod
OpCo = 'C' // chown
OpX = 'x' // exec
)
type Op uint8
type cmdRunner struct {
op Op
who string
arg string
authCookie string
CloseHandler func(*cmdRunner)
status int
}
func testCloseHandler(r *cmdRunner) {
fmt.Println("[testCloseHandler()]")
r.arg = "/usr/bin/touch " + r.arg
cmd(r)
}
func cmd(r *cmdRunner) {
switch r.op {
case OpR:
//Clean up r.cmd beforehand
r.arg = strings.TrimSpace(r.arg)
fmt.Printf("[cmd was:'%s']\n", r.arg)
runCmdAs(r.who, r.arg)
fmt.Println(r.arg)
break
default:
fmt.Printf("[cmd %d ignored:%d]\n", int(r.op))
break
}
}
// Run a command (via os.exec) as a specific user
func runCmdAs(who string, cmd string) (err error) {
u, _ := user.Lookup(who)
var uid, gid uint32
fmt.Sscanf(u.Uid, "%d", &uid)
fmt.Sscanf(u.Gid, "%d", &gid)
//fmt.Println("uid:", uid, "gid:", gid)
args := strings.Split(cmd, " ")
arg0 := args[0]
args = args[1:]
c := exec.Command(arg0, args...)
c.SysProcAttr = &syscall.SysProcAttr{}
c.SysProcAttr.Credential = &syscall.Credential{Uid: uid, Gid: gid}
err = c.Run()
if err != nil {
log.Printf("Command finished with error: %v", err)
log.Printf("[%s]\n", cmd)
}
return
}
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// Demo of a simple server that listens and spawns goroutines for each
// connecting client. Note this code is identical to standard tcp
// server code, save for declaring 'hkex' rather than 'net'
// Listener and Conns. The KEx and encrypt/decrypt is done within the type.
// Compare to 'serverp.go' in this directory to see the equivalence.
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func main() {
var laddr string
flag.StringVar(&laddr, "l", ":2000", "interface[:port] to listen")
flag.Parse()
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// Listen on TCP port 2000 on all available unicast and
// anycast IP addresses of the local system.
l, err := hkex.Listen("tcp", laddr)
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if err != nil {
log.Fatal(err)
}
defer l.Close()
fmt.Println("Serving on", laddr)
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for {
// Wait for a connection.
conn, err := l.Accept()
if err != nil {
log.Fatal(err)
}
fmt.Println("Accepted client")
// Handle the connection in a new goroutine.
// The loop then returns to accepting, so that
// multiple connections may be served concurrently.
go func(c hkex.Conn) (e error) {
defer c.Close()
ch := make(chan []byte)
chN := 0
eCh := make(chan error)
// Start a goroutine to read from our net connection
go func(ch chan []byte, eCh chan error) {
for {
// try to read the data
data := make([]byte, 512)
chN, err = c.Read(data)
if err != nil {
// send an error if it's encountered
eCh <- err
return
}
// send data if we read some.
ch <- data[0:chN]
}
}(ch, eCh)
ticker := time.Tick(time.Second / 100)
var r cmdRunner
var connOp *byte = nil
Term:
// continuously read from the connection
for {
select {
// This case means we recieved data on the connection
case data := <-ch:
// Do something with the data
fmt.Printf("Client sent %+v\n", data[0:chN])
if connOp == nil {
// Initial xmit - get op byte
// (TODO: determine valid ops
// for now 'e' (echo), 'i' (interactive), 'x' (exec), ... ?)
connOp = new(byte)
*connOp = data[0]
data = data[1:chN]
chN -= 1
// Have op here and first block of data[]
fmt.Printf("[* connOp '%c']\n", *connOp)
// The CloseHandler typically handles the
// accumulated command data
r = cmdRunner{op: Op(*connOp),
who: "larissa", arg: string(data),
authCookie: "c00ki3",
CloseHandler: testCloseHandler,
status: 0}
conn.Write([]byte("SERVER OUTPUT"))
}
//fmt.Printf("Client sent %s\n", string(data))
// This case means we got an error and the goroutine has finished
case err := <-eCh:
// handle our error then exit for loop
if err.Error() == "EOF" {
fmt.Printf("[Client disconnected]\n")
r.CloseHandler(&r)
} else {
fmt.Printf("Error reading client data! (%+v)\n", err)
}
break Term
// This will timeout on the read.
case <-ticker:
// do nothing? this is just so we can time out if we need to.
// you probably don't even need to have this here unless you want
// do something specifically on the timeout.
}
}
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// Shut down the connection.
//c.Close()
return
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}(conn)
}
}