argument to change uid/gid (#927)

different from
https://github.com/yggdrasil-network/yggdrasil-go/pull/817 in that it
can resolve user names, automatically use user's primary gid & allows
specifying gid in the same argument, with `:` eg `username:groupname`.
feel free to criticize & suggest different argument name & description
because i didn't put much of thought to that.

---------

Co-authored-by: Neil <git@neilalexander.dev>
Co-authored-by: VNAT <xepjk@protonmail.com>
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>
This commit is contained in:
cathugger 2024-09-22 15:46:54 +00:00 committed by GitHub
parent c4b29b735c
commit 34f087de1c
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3 changed files with 106 additions and 0 deletions

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@ -0,0 +1,10 @@
//go:build !aix && !darwin && !dragonfly && !freebsd && !linux && !netbsd && !openbsd && !solaris
// +build !aix,!darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris
package main
import "errors"
func chuser(user string) error {
return errors.New("setting uid/gid is not supported on this platform")
}

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@ -0,0 +1,87 @@
//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
package main
import (
"errors"
"fmt"
"math"
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)
var err error
if gid < math.MaxInt {
err = syscall.Setgid(int(gid))
} else {
err = errors.New("gid too big")
}
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(uint32(gid)))
if err != nil {
return fmt.Errorf("failed to setgid %d: %v", gid, err)
}
}
if u != nil {
uid, _ := strconv.ParseUint(u.Uid, 10, 32)
var err error
if uid < math.MaxInt {
err = syscall.Setuid(int(uid))
} else {
err = errors.New("uid too big")
}
if err != nil {
return fmt.Errorf("failed to setuid %d: %v", uid, err)
}
}
return nil
}

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@ -52,6 +52,7 @@ func main() {
getsnet := flag.Bool("subnet", false, "use in combination with either -useconf or -useconffile, outputs your IPv6 subnet") getsnet := flag.Bool("subnet", false, "use in combination with either -useconf or -useconffile, outputs your IPv6 subnet")
getpkey := flag.Bool("publickey", false, "use in combination with either -useconf or -useconffile, outputs your public key") getpkey := flag.Bool("publickey", false, "use in combination with either -useconf or -useconffile, outputs your public key")
loglevel := flag.String("loglevel", "info", "loglevel to enable") loglevel := flag.String("loglevel", "info", "loglevel to enable")
chuserto := flag.String("user", "", "user (and, optionally, group) to set UID/GID to")
flag.Parse() flag.Parse()
done := make(chan struct{}) done := make(chan struct{})
@ -280,6 +281,14 @@ func main() {
<-done <-done
}) })
// Change user if requested
if *chuserto != "" {
err = chuser(*chuserto)
if err != nil {
panic(err)
}
}
// Block until we are told to shut down. // Block until we are told to shut down.
<-ctx.Done() <-ctx.Done()