yggdrasil-go/cmd/yggdrasil/chuser_unix.go
Klemens Nanni a0bfd9da44
Rewrite chuser() for simplicity and correctness
- Use unambiguous variable names (w/o package name conflict).
- Fail on invalid input such as the empty string or `:`.
- Do not change group without user, i.e. fail on `:group`.
- Parse input using mnemonic APIs.
- Do not juggle between integer types.
- Unset supplementary groups.
- Use setres[ug]id(2) to match the idiom of OpenBSD base programs.

Includes/Supersedes #1202.
Fixes #927.

I only tested on OpenBSD (so far), hence the split, but other systems
should just work.
2024-11-11 23:02:19 +03:00

93 lines
2.1 KiB
Go

//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || solaris
// +build aix darwin dragonfly freebsd linux netbsd 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 {
if err := syscall.Setgroups([]int{int(gid)}); err != nil {
return fmt.Errorf("failed to setgroups %d: %v", gid, err)
}
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)
if err := syscall.Setgroups([]int{int(uint32(gid))}); err != nil {
return fmt.Errorf("failed to setgroups %d: %v", gid, err)
}
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
}