Support interactive SSH sessions on Windows

.github/workflows/checks.yml

@@ -42,3 +42,16 @@ jobs:
           duration: 30m
           authorized-users: hugosantos,n-g,htr
           slack-announce-channel: "#ci"
+
+  windows-ssh:
+    name: Windows SSH
+    runs-on: windows-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Install Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: 'stable'
+      - name: Test Windows SSH
+        run: go test ./pkg/sshd

pkg/sshd/pty_windows.go

@@ -3,13 +3,15 @@
 package sshd
 
 import (
-	"errors"
 	"io"
 	"os/exec"
 
 	"github.com/gliderlabs/ssh"
 )
 
-func handlePty(session io.ReadWriter, ptyReq ssh.Pty, winCh <-chan ssh.Window, cmd *exec.Cmd) error {
-	return errors.New("pty not supported in windows")
+func handlePty(session io.ReadWriter, _ ssh.Pty, _ <-chan ssh.Window, cmd *exec.Cmd) error {
+	cmd.Stdin = session
+	cmd.Stdout = session
+	cmd.Stderr = session
+	return cmd.Start()
 }

pkg/sshd/pty_windows_test.go

@@ -0,0 +1,89 @@
+//go:build windows
+
+package sshd
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"net"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	gossh "golang.org/x/crypto/ssh"
+)
+
+func TestWindowsPTYSession(t *testing.T) {
+	clientKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	clientSigner, err := gossh.NewSignerFromKey(clientKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	server, err := MakeServer(context.Background(), SSHServerOpts{
+		AllowedUsers: []string{"runner"},
+		AuthorizedKeys: map[string]string{
+			string(gossh.MarshalAuthorizedKey(clientSigner.PublicKey())): "test",
+		},
+		Env:   os.Environ(),
+		Shell: []string{os.Getenv("COMSPEC")},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+	defer server.Server.Close()
+
+	go func() {
+		_ = server.Server.Serve(listener)
+	}()
+
+	client, err := gossh.Dial("tcp", listener.Addr().String(), &gossh.ClientConfig{
+		User:            "runner",
+		Auth:            []gossh.AuthMethod{gossh.PublicKeys(clientSigner)},
+		HostKeyCallback: gossh.InsecureIgnoreHostKey(),
+		Timeout:         10 * time.Second,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer client.Close()
+
+	session, err := client.NewSession()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer session.Close()
+
+	if err := session.RequestPty("xterm", 24, 80, gossh.TerminalModes{}); err != nil {
+		t.Fatal(err)
+	}
+
+	const marker = "breakpoint-windows-pty-ok"
+	var stdout, stderr bytes.Buffer
+	session.Stdin = strings.NewReader("echo " + marker + "\r\nexit\r\n")
+	session.Stdout = &stdout
+	session.Stderr = &stderr
+
+	if err := session.Shell(); err != nil {
+		t.Fatal(err)
+	}
+	if err := session.Wait(); err != nil {
+		t.Fatalf("Windows shell failed: %v\nstdout:\n%s\nstderr:\n%s", err, stdout.String(), stderr.String())
+	}
+	if !strings.Contains(stdout.String(), marker) {
+		t.Fatalf("Windows shell stdout did not contain %q:\n%s\nstderr:\n%s", marker, stdout.String(), stderr.String())
+	}
+}

pkg/sshd/sshd.go

@@ -106,6 +106,7 @@ func MakeServer(ctx context.Context, opts SSHServerOpts) (*SSHServer, error) {
 					return
 				}
 			} else {
+				cmd.Stdin = session
 				cmd.Stdout = session
 				cmd.Stderr = session
 				if err := cmd.Start(); err != nil {