argument to change uid/gid

cmd/yggdrasil/chuser_unix.go

@@ -0,0 +1,73 @@
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package main
+
+import (
+	"fmt"
+	osuser "os/user"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+func chuser(user string) error {
+	group := ""
+	if i := strings.IndexByte(user, ':'); i >= 0 {
+		user, group = user[:i], user[i+1:]
+	}
+
+	u := (*osuser.User)(nil)
+	g := (*osuser.Group)(nil)
+
+	if user != "" {
+		if _, err := strconv.ParseUint(user, 10, 32); err == nil {
+			u, err = osuser.LookupId(user)
+			if err != nil {
+				return fmt.Errorf("failed to lookup user by id %q: %v", user, err)
+			}
+		} else {
+			u, err = osuser.Lookup(user)
+			if err != nil {
+				return fmt.Errorf("failed to lookup user by name %q: %v", user, err)
+			}
+		}
+	}
+	if group != "" {
+		if _, err := strconv.ParseUint(group, 10, 32); err == nil {
+			g, err = osuser.LookupGroupId(group)
+			if err != nil {
+				return fmt.Errorf("failed to lookup group by id %q: %v", user, err)
+			}
+		} else {
+			g, err = osuser.LookupGroup(group)
+			if err != nil {
+				return fmt.Errorf("failed to lookup group by name %q: %v", user, err)
+			}
+		}
+	}
+
+	if g != nil {
+		gid, _ := strconv.ParseUint(g.Gid, 10, 32)
+		err := syscall.Setgid(int(gid))
+		if err != nil {
+			return fmt.Errorf("failed to setgid %d: %v", gid, err)
+		}
+	} else if u != nil {
+		gid, _ := strconv.ParseUint(u.Gid, 10, 32)
+		err := syscall.Setgid(int(gid))
+		if err != nil {
+			return fmt.Errorf("failed to setgid %d: %v", gid, err)
+		}
+	}
+
+	if u != nil {
+		uid, _ := strconv.ParseUint(u.Uid, 10, 32)
+		err := syscall.Setuid(int(uid))
+		if err != nil {
+			return fmt.Errorf("failed to setuid %d: %v", uid, err)
+		}
+	}
+
+	return nil
+}