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cmd/yggdrasil/chuser_unix.go

@@ -0,0 +1,62 @@
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+
+package main
+
+import (
+	"fmt"
+	"os/user"
+	"strconv"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+func chuser(input string) error {
+	givenUser, givenGroup, _ := strings.Cut(input, ":")
+	if givenUser == "" {
+		return fmt.Errorf("user is empty")
+	}
+	if strings.Contains(input, ":") && givenGroup == "" {
+		return fmt.Errorf("group is empty")
+	}
+
+	var (
+		err      error
+		usr      *user.User
+		grp      *user.Group
+		uid, gid int
+	)
+
+	if usr, err = user.LookupId(givenUser); err != nil {
+		if usr, err = user.Lookup(givenUser); err != nil {
+			return err
+		}
+	}
+	if uid, err = strconv.Atoi(usr.Uid); err != nil {
+		return err
+	}
+
+	if givenGroup != "" {
+		if grp, err = user.LookupGroupId(givenGroup); err != nil {
+			if grp, err = user.LookupGroup(givenGroup); err != nil {
+				return err
+			}
+		}
+
+		gid, _ = strconv.Atoi(grp.Gid)
+	} else {
+		gid, _ = strconv.Atoi(usr.Gid)
+	}
+
+	if err := unix.Setgroups([]int{gid}); err != nil {
+		return fmt.Errorf("setgroups: %d: %v", gid, err)
+	}
+	if err := unix.Setgid(gid); err != nil {
+		return fmt.Errorf("setgid: %d: %v", gid, err)
+	}
+	if err := unix.Setuid(uid); err != nil {
+		return fmt.Errorf("setuid: %d: %v", uid, err)
+	}
+
+	return nil
+}