feat(exec): initial

.gitignore

@@ -1,2 +1,3 @@
 /cmd/wingmate/wingmate
-/cmd/pidproxy/pidproxy
+/cmd/pidproxy/pidproxy
+/cmd/exec/exec

Makefile

@@ -8,6 +8,9 @@ wingmate:
 pidproxy:
 	$(MAKE) -C cmd/pidproxy all
 
+exec:
+	$(MAKE) -C cmd/exec all
+
 dummy:
 	$(MAKE) -C cmd/experiment/dummy all
 
@@ -23,6 +26,7 @@ starter:
 clean:
 	$(MAKE) -C cmd/wingmate clean
 	$(MAKE) -C cmd/pidproxy clean
+	$(MAKE) -C cmd/exec clean
 	$(MAKE) -C cmd/experiment/dummy clean
 	$(MAKE) -C cmd/experiment/oneshot clean
 	$(MAKE) -C cmd/experiment/spawner clean

cmd/exec/Makefile

@@ -0,0 +1,5 @@
+all:
+	go build -v
+
+clean:
+	go clean -i -cache -testcache

cmd/exec/ent.go

@@ -0,0 +1,11 @@
+//go:build !(cgo && linux)
+
+package main
+
+func getUid(user string) (uint64, error) {
+	panic("not implemented")
+}
+
+func getGid(group string) (uint64, error) {
+	panic("not implemented")
+}

cmd/exec/ent_lin.go

@@ -0,0 +1,15 @@
+//go:build cgo && linux
+
+package main
+
+import (
+	"errors"
+)
+
+func getUid(user string) (uint64, error) {
+	return 0, errors.New("not implemented")
+}
+
+func getGid(group string) (uint64, error) {
+	return 0, errors.New("not implemented")
+}

cmd/exec/exec.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"errors"
+	"log"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+
+	"gitea.suyono.dev/suyono/wingmate"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+	"golang.org/x/sys/unix"
+)
+
+const (
+	setsidFlag = "setsid"
+	EnvSetsid  = "SETSID"
+	userFlag   = "user"
+	EnvUser    = "USER"
+)
+
+var (
+	rootCmd = &cobra.Command{
+		Use:  "wmexec",
+		RunE: execCmd,
+	}
+
+	childArgs []string
+)
+
+func main() {
+	var (
+		found    bool
+		i        int
+		arg      string
+		selfArgs []string
+	)
+
+	rootCmd.PersistentFlags().BoolP(setsidFlag, "s", false, "set to true to run setsid() before exec")
+	viper.BindPFlag(EnvSetsid, rootCmd.PersistentFlags().Lookup(setsidFlag))
+
+	rootCmd.PersistentFlags().StringP(userFlag, "u", "", "\"user:[group]\"")
+	viper.BindPFlag(EnvUser, rootCmd.PersistentFlags().Lookup(userFlag))
+
+	viper.SetEnvPrefix(wingmate.EnvPrefix)
+	viper.BindEnv(EnvUser)
+	viper.BindEnv(EnvSetsid)
+	viper.SetDefault(EnvSetsid, false)
+	viper.SetDefault(EnvUser, "")
+
+	found = false
+	for i, arg = range os.Args {
+		if arg == "--" {
+			found = true
+			if len(os.Args) <= i+1 {
+				log.Println("invalid argument")
+				os.Exit(1)
+			}
+			selfArgs = os.Args[1:i]
+			childArgs = os.Args[i+1:]
+			break
+		}
+	}
+	if !found {
+		log.Println("invalid argument")
+		os.Exit(1)
+	}
+
+	if len(childArgs) == 0 {
+		log.Println("invalid argument")
+		os.Exit(1)
+	}
+
+	rootCmd.SetArgs(selfArgs)
+	if err := rootCmd.Execute(); err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+}
+
+func execCmd(cmd *cobra.Command, args []string) error {
+	if viper.GetBool(EnvSetsid) {
+		_, _ = unix.Setsid()
+	}
+
+	var (
+		uid  uint64
+		gid  uint64
+		err  error
+		path string
+	)
+
+	ug := viper.GetString(EnvUser)
+	if len(ug) > 0 {
+		user, group, ok := strings.Cut(ug, ":")
+		uid, err = strconv.ParseUint(user, 10, 32)
+		if err != nil {
+			if uid, err = getUid(user); err != nil {
+				return err
+			}
+		}
+		if err = unix.Setuid(int(uid)); err != nil {
+			return err
+		}
+
+		if ok {
+			if gid, err = strconv.ParseUint(group, 10, 32); err != nil {
+				if gid, err = getGid(group); err != nil {
+					return err
+				}
+			}
+			if err = unix.Setgid(int(gid)); err != nil {
+				return err
+			}
+		}
+	}
+
+	if path, err = exec.LookPath(childArgs[0]); err != nil {
+		if !errors.Is(err, exec.ErrDot) {
+			return err
+		}
+	}
+
+	if err = unix.Exec(path, childArgs, os.Environ()); err != nil {
+		return err
+	}
+
+	return nil
+}

cmd/pidproxy/pidproxy.go

@@ -42,11 +42,6 @@ func main() {
 	viper.BindEnv(EnvStartSecs)
 	viper.SetDefault(EnvStartSecs, EnvDefaultStartSecs)
 
-	if len(os.Args) <= 2 {
-		log.Println("invalid argument")
-		os.Exit(1)
-	}
-
 	rootCmd.PersistentFlags().StringP(pidFileFlag, "p", "", "location of pid file")
 	rootCmd.MarkFlagRequired(pidFileFlag)
 	viper.BindPFlag(pidFileFlag, rootCmd.PersistentFlags().Lookup(pidFileFlag))
@@ -55,11 +50,11 @@ func main() {
 	for i, arg = range os.Args {
 		if arg == "--" {
 			found = true
-			selfArgs = os.Args[1:i]
 			if len(os.Args) <= i+1 {
 				log.Println("invalid argument")
 				os.Exit(1)
 			}
+			selfArgs = os.Args[1:i]
 			childArgs = os.Args[i+1:]
 			break
 		}
@@ -69,6 +64,11 @@ func main() {
 		os.Exit(1)
 	}
 
+	if len(childArgs) == 0 {
+		log.Println("invalid argument")
+		os.Exit(1)
+	}
+
 	rootCmd.SetArgs(selfArgs)
 
 	if err := rootCmd.Execute(); err != nil {