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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2017 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package sys
import (
"os"
"syscall"
"unsafe"
)
// FlagID can be passed to chown-ish functions to mean "no change",
// and can be returned from getuid-ish functions to mean "not found".
const FlagID = 1<<32 - 1
// UserID is the type of the system's user identifiers (in C, uid_t).
//
// We give it its own explicit type so you don't have to remember that
// it's a uint32 (which lead to the bug this package fixes in the
// first place)
type UserID uint32
// GroupID is the type of the system's group identifiers (in C, gid_t).
type GroupID uint32
// uid_t is an unsigned 32-bit integer in linux right now.
// so syscall.Gete?[ug]id are wrong, and break in 32 bits
// (see https://github.com/golang/go/issues/22739)
func Getuid() UserID {
return UserID(getid(_SYS_GETUID))
}
func Geteuid() UserID {
return UserID(getid(_SYS_GETEUID))
}
func Getgid() GroupID {
return GroupID(getid(_SYS_GETGID))
}
func Getegid() GroupID {
return GroupID(getid(_SYS_GETEGID))
}
func getid(id uintptr) uint32 {
// these are documented as not failing, but see golang#22924
r0, _, errno := syscall.RawSyscall(id, 0, 0, 0)
if errno != 0 {
return uint32(-errno)
}
return uint32(r0)
}
func Chown(f *os.File, uid UserID, gid GroupID) error {
return Fchown(int(f.Fd()), uid, gid)
}
func Fchown(fd int, uid UserID, gid GroupID) error {
_, _, errno := syscall.Syscall(syscall.SYS_FCHOWN, uintptr(fd), uintptr(uid), uintptr(gid))
if errno == 0 {
return nil
}
return errno
}
func ChownPath(path string, uid UserID, gid GroupID) error {
AT_FDCWD := -100 // also written as -0x64 in ztypes_linux_*.go (but -100 in sys_linux_*.s, and /usr/include/linux/fcntl.h)
return FchownAt(uintptr(AT_FDCWD), path, uid, gid, 0)
}
func FchownAt(dirfd uintptr, path string, uid UserID, gid GroupID, flags int) error {
p0, err := syscall.BytePtrFromString(path)
if err != nil {
return err
}
_, _, errno := syscall.Syscall6(_SYS_FCHOWNAT, dirfd, uintptr(unsafe.Pointer(p0)), uintptr(uid), uintptr(gid), uintptr(flags), 0)
if errno == 0 {
return nil
}
return errno
}
// As of Go 1.9, the O_PATH constant does not seem to be declared
// uniformly over all archtiectures.
const O_PATH = 0x200000
func FcntlGetFl(fd int) (int, error) {
flags, _, errno := syscall.Syscall(syscall.SYS_FCNTL, uintptr(fd), uintptr(syscall.F_GETFL), 0)
if errno != 0 {
return 0, errno
}
return int(flags), nil
}
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