rework ssh 'init' command

Dockerfile

@@ -16,9 +16,10 @@ from alpine:3.19.0 as initrd
 run apk add --no-cache xz
 
 workdir /layer
-run wget -O- https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-minirootfs-3.18.4-x86_64.tar.gz |tar zxv
+run . /etc/os-release \
+ && wget -O- https://dl-cdn.alpinelinux.org/alpine/v${VERSION_ID%.*}/releases/x86_64/alpine-minirootfs-${VERSION_ID}-x86_64.tar.gz |tar zxv
 
-run apk add --no-cache -p . musl lvm2 lvm2-dmeventd udev cryptsetup e2fsprogs btrfs-progs lsblk
+run apk add --no-cache -p . musl lvm2 lvm2-extra lvm2-dmeventd udev cryptsetup e2fsprogs btrfs-progs lsblk
 run rm -rf usr/share/apk var/cache/apk
 
 copy --from=build /go/bin/init .

ask-secret.go

@@ -6,41 +6,51 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"sync"
+	"sync/atomic"
 )
 
-func askSecret(prompt string) []byte {
+var (
-	stdinTTY.EchoOff()
+	inputTTYs    = new(sync.Map)
+	askingSecret atomic.Bool
+)
 
-	var (
+func registerInput(in *tty)  { inputTTYs.Store(in, in) }
-		in  io.Reader = stdin
+func unregiterInput(in *tty) { inputTTYs.Delete(in) }
-		out io.Writer = stdout
-	)
 
-	if stdin == nil {
+func askSecret(prompt string) (s []byte) {
-		in = os.Stdin
+	err := func() (err error) {
-		out = os.Stdout
+		askingSecret.Store(true)
-	}
+		defer askingSecret.Store(false)
 
-	out.Write([]byte(prompt + ": "))
+		inputTTYs.Range(func(k, v any) (con bool) { v.(*tty).EchoOff(); return true })
+		defer inputTTYs.Range(func(k, v any) (con bool) { v.(*tty).Restore(); return true })
 
-	if stdin != nil {
+		var (
-		stdout.HideInput()
+			in  io.Reader = stdin
-	}
+			out io.Writer = stdout
+		)
 
-	s, err := bufio.NewReader(in).ReadBytes('\n')
+		if stdin == nil {
+			in = os.Stdin
+			out = os.Stdout
+		}
 
-	if stdin != nil {
+		out.Write([]byte(prompt + ": "))
-		stdout.ShowInput()
-	}
 
-	stdinTTY.Restore()
+		s, err = bufio.NewReader(in).ReadBytes('\n')
+		if err != nil {
+			return
+		}
+
+		fmt.Println()
+		s = bytes.TrimRight(s, "\r\n")
+		return
+	}()
 
 	if err != nil {
 		fatalf("failed to read from stdin: %v", err)
 	}
 
-	fmt.Println()
+	return
-
-	s = bytes.TrimRight(s, "\r\n")
-	return s
 }

go.mod

@@ -1,8 +1,8 @@
 module novit.tech/direktil/initrd
 
 require (
+	github.com/creack/pty v1.1.21
 	github.com/freddierice/go-losetup/v2 v2.0.1
-	github.com/kr/pty v1.1.8
 	github.com/pkg/term v1.1.0
 	github.com/rs/zerolog v1.31.0
 	golang.org/x/crypto v0.18.0
@@ -16,7 +16,6 @@ require (
 
 require (
 	github.com/cavaliergopher/cpio v1.0.1 // indirect
-	github.com/creack/pty v1.1.21 // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/josharian/native v1.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect

go.sum

@@ -1,7 +1,6 @@
 github.com/cavaliergopher/cpio v1.0.1 h1:KQFSeKmZhv0cr+kawA3a0xTQCU4QxXF1vhU7P7av2KM=
 github.com/cavaliergopher/cpio v1.0.1/go.mod h1:pBdaqQjnvXxdS/6CvNDwIANIFSP0xRKI16PX4xejRQc=
 github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
-github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7DoTY=
 github.com/creack/pty v1.1.21 h1:1/QdRyBaHHJP61QkWMXlOIBfsgdDeeKfK8SYVUWJKf0=
 github.com/creack/pty v1.1.21/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
 github.com/freddierice/go-losetup/v2 v2.0.1 h1:wPDx/Elu9nDV8y/CvIbEDz5Xi5Zo80y4h7MKbi3XaAI=
@@ -11,8 +10,6 @@ github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/josharian/native v1.1.0 h1:uuaP0hAbW7Y4l0ZRQ6C9zfb7Mg1mbFKry/xzDAfmtLA=
 github.com/josharian/native v1.1.0/go.mod h1:7X/raswPFr05uY3HiLlYeyQntB6OO7E/d2Cu7qoaN2w=
-github.com/kr/pty v1.1.8 h1:AkaSdXYQOWeaO3neb8EM634ahkXXe3jYbVh/F9lq+GI=
-github.com/kr/pty v1.1.8/go.mod h1:O1sed60cT9XZ5uDucP5qwvh+TE3NnUj51EiZO/lmSfw=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
 github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=

main.go

@@ -44,6 +44,8 @@ func newPipe() (io.ReadCloser, io.WriteCloser) {
 func main() {
 	log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
 
+	registerInput(newTTY(os.Stdin.Fd()))
+
 	switch baseName := filepath.Base(os.Args[0]); baseName {
 	case "init":
 		runInit()

ssh.go

@@ -9,9 +9,10 @@ import (
 	"os/exec"
 	"sync"
 	"syscall"
+	"time"
 	"unsafe"
 
-	"github.com/kr/pty"
+	"github.com/creack/pty"
 	"github.com/rs/zerolog/log"
 	"golang.org/x/crypto/ssh"
 
@@ -142,14 +143,35 @@ func sshHandleChannel(remoteAddr string, channel ssh.Channel, requests <-chan *s
 			command := string(req.Payload[4 : req.Payload[3]+4])
 			switch command {
 			case "init":
-				go func() {
+				if ptyF == nil {
-					io.Copy(channel, stdout.NewReader())
+					go func() {
-					once.Do(closeCh)
+						channel.Stderr().Write([]byte("\033[5m\033[31;1m\n\nWARNING: no TTY requested, passwords will be echoed!\n\n\033[0m"))
-				}()
+						time.Sleep(3 * time.Second)
-				go func() {
+						io.Copy(channel, stdout.NewReader())
-					io.Copy(stdinPipe, channel)
+						once.Do(closeCh)
-					once.Do(closeCh)
+					}()
-				}()
+					go func() {
+						io.Copy(stdinPipe, channel)
+						once.Do(closeCh)
+					}()
+
+				} else {
+					stdinTTY := newTTY(ptyF.Fd())
+					if askingSecret.Load() {
+						stdinTTY.EchoOff()
+					}
+					registerInput(stdinTTY)
+					defer unregiterInput(stdinTTY)
+
+					go func() {
+						io.Copy(ttyF, stdout.NewReader())
+						once.Do(closeCh)
+					}()
+					go func() {
+						io.Copy(stdinPipe, ttyF)
+						once.Do(closeCh)
+					}()
+				}
 
 				req.Reply(true, nil)
 
@@ -195,15 +217,6 @@ func sshHandleChannel(remoteAddr string, channel ssh.Channel, requests <-chan *s
 				ttyF = nil
 			}()
 
-			go func() {
-				io.Copy(channel, ptyF)
-				once.Do(closeCh)
-			}()
-			go func() {
-				io.Copy(ptyF, channel)
-				once.Do(closeCh)
-			}()
-
 			req.Reply(true, nil)
 
 		case "pty-req":
@@ -227,6 +240,15 @@ func sshHandleChannel(remoteAddr string, channel ssh.Channel, requests <-chan *s
 
 			req.Reply(true, nil)
 
+			go func() {
+				io.Copy(channel, ptyF)
+				once.Do(closeCh)
+			}()
+			go func() {
+				io.Copy(ptyF, channel)
+				once.Do(closeCh)
+			}()
+
 		case "window-change":
 			w, h := sshParseDims(req.Payload)
 			sshSetWinsize(ptyF.Fd(), w, h)

test-initrd/config.yaml

@@ -26,9 +26,9 @@ networks:
     - eno.*
     - enp.*
   script: |
-    ip a add 2001:41d0:306:168f::1337:2eed/64 dev $iface
     ip li set $iface up
-    #udhcpc $iface
+    udhcpc -i $iface -b -t1 -T1 -A5 ||
+    ip a add 2001:41d0:306:168f::1337:2eed/64 dev $iface
 
 pre_lvm_crypt:
 - dev: /dev/vda

tty.go

@@ -1,29 +1,25 @@
 package main
 
 import (
-	"os"
-
 	"golang.org/x/sys/unix"
 )
 
-var (
-	stdinTTY = &tty{int(os.Stdin.Fd()), nil}
-)
-
 type tty struct {
 	fd      int
 	termios *unix.Termios
 }
 
+func newTTY(fd uintptr) *tty {
+	termios, _ := unix.IoctlGetTermios(int(fd), unix.TCGETS)
+	return &tty{int(fd), termios}
+}
+
 func (t *tty) EchoOff() {
-	termios, err := unix.IoctlGetTermios(t.fd, unix.TCGETS)
+	if t.termios == nil {
-	if err != nil {
 		return
 	}
 
-	t.termios = termios
+	newState := *t.termios
-
-	newState := *termios
 	newState.Lflag &^= unix.ECHO
 	newState.Lflag |= unix.ICANON | unix.ISIG
 	newState.Iflag |= unix.ICRNL
@@ -31,8 +27,9 @@ func (t *tty) EchoOff() {
 }
 
 func (t *tty) Restore() {
-	if t.termios != nil {
+	if t.termios == nil {
-		unix.IoctlSetTermios(t.fd, unix.TCSETS, t.termios)
+		return
-		t.termios = nil
 	}
+
+	unix.IoctlSetTermios(t.fd, unix.TCSETS, t.termios)
 }