initial commit

internal/serve/serve.go

@@ -0,0 +1,100 @@
+package serve
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/charmbracelet/log"
+	"github.com/charmbracelet/ssh"
+	"github.com/charmbracelet/wish"
+	"github.com/charmbracelet/wish/activeterm"
+	"github.com/charmbracelet/wish/logging"
+)
+
+// Setup default logger to append or create a new log file `log` in the current
+// working directory containing all the logs reported by the ssh server.
+func setupLogging() {
+	file, err := os.OpenFile("log", os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
+	if err != nil {
+		panic(fmt.Errorf("Could not create or open log file. err: %w", err))
+	}
+	log.SetDefault(log.NewWithOptions(file, log.Options{ReportTimestamp: true}))
+}
+
+// Configure ssh server with the provided arguments. An empty `users` map
+// will disable user authentication. At least one user is required for user
+// authentication via ssh-public keys. Each map entry has a pair of *username*
+// and *pub-key value*. The ssh server will serve every authenticated user (or
+// all if no user is given) the application `name` with the provided arguments
+// `args` as the ssh session. The ssh session will always allocate an pty
+// (necessary for tui applications).
+func setupSshServer(host string, port string, users map[string]string, name string, args []string) (*ssh.Server, error) {
+	return wish.NewServer(
+		wish.WithAddress(net.JoinHostPort(host, port)),
+		wish.WithHostKeyPath(".ssh/ssh_host_ed25519_key"),
+		wish.WithPublicKeyAuth(func(_ ssh.Context, key ssh.PublicKey) bool {
+			if len(users) == 0 {
+				// no users provided, meaning there is no user authentication, everyone is allowed to connect
+				return true
+			}
+			for _, pubkey := range users {
+				parsed, _, _, _, _ := ssh.ParseAuthorizedKey([]byte(pubkey))
+				if ssh.KeysEqual(key, parsed) {
+					return true
+				}
+			}
+			return false
+		}),
+		ssh.AllocatePty(),
+		wish.WithMiddleware(
+			func(next ssh.Handler) ssh.Handler {
+				return func(s ssh.Session) {
+					cmd := wish.Command(s, name, args...)
+					if err := cmd.Run(); err != nil {
+						wish.Fatalln(s, err)
+					}
+					next(s)
+				}
+			},
+			activeterm.Middleware(),
+			logging.Middleware(),
+		),
+	)
+}
+
+// Serve an ssh application using the provided arguments.
+func Serve(host string, port string, users map[string]string, name string, args []string) {
+	setupLogging()
+	srv, err := setupSshServer(host, port, users, name, args)
+	if err != nil {
+		log.Error("Could not start server", "error", err)
+	}
+
+	done := make(chan os.Signal, 1)
+	signal.Notify(done, os.Interrupt, syscall.SIGINT, syscall.SIGTERM)
+
+	go func() {
+		log.Info("Starting SSH server...")
+		if err = srv.ListenAndServe(); err != nil && !errors.Is(err, ssh.ErrServerClosed) {
+			// We ignore ErrServerClosed because it is expected.
+			log.Error("Could not start server", "error", err)
+			done <- nil
+		}
+	}()
+
+	<-done
+
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer func() { cancel() }()
+
+	log.Info("Stopping SSH server...")
+	if err := srv.Shutdown(ctx); err != nil && !errors.Is(err, ssh.ErrServerClosed) {
+		log.Error("Could not stop server", "error", err)
+	}
+}