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cap_freebsd.go
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cap_freebsd.go
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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build freebsd
// +build freebsd
package unix
import (
"errors"
"fmt"
)
// Go implementation of C mostly found in /usr/src/sys/kern/subr_capability.c
const (
// This is the version of CapRights this package understands. See C implementation for parallels.
capRightsGoVersion = CAP_RIGHTS_VERSION_00
capArSizeMin = CAP_RIGHTS_VERSION_00 + 2
capArSizeMax = capRightsGoVersion + 2
)
var (
bit2idx = []int{
-1, 0, 1, -1, 2, -1, -1, -1, 3, -1, -1, -1, -1, -1, -1, -1,
4, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
}
)
func capidxbit(right uint64) int {
return int((right >> 57) & 0x1f)
}
func rightToIndex(right uint64) (int, error) {
idx := capidxbit(right)
if idx < 0 || idx >= len(bit2idx) {
return -2, fmt.Errorf("index for right 0x%x out of range", right)
}
return bit2idx[idx], nil
}
func caprver(right uint64) int {
return int(right >> 62)
}
func capver(rights *CapRights) int {
return caprver(rights.Rights[0])
}
func caparsize(rights *CapRights) int {
return capver(rights) + 2
}
// CapRightsSet sets the permissions in setrights in rights.
func CapRightsSet(rights *CapRights, setrights []uint64) error {
// This is essentially a copy of cap_rights_vset()
if capver(rights) != CAP_RIGHTS_VERSION_00 {
return fmt.Errorf("bad rights version %d", capver(rights))
}
n := caparsize(rights)
if n < capArSizeMin || n > capArSizeMax {
return errors.New("bad rights size")
}
for _, right := range setrights {
if caprver(right) != CAP_RIGHTS_VERSION_00 {
return errors.New("bad right version")
}
i, err := rightToIndex(right)
if err != nil {
return err
}
if i >= n {
return errors.New("index overflow")
}
if capidxbit(rights.Rights[i]) != capidxbit(right) {
return errors.New("index mismatch")
}
rights.Rights[i] |= right
if capidxbit(rights.Rights[i]) != capidxbit(right) {
return errors.New("index mismatch (after assign)")
}
}
return nil
}
// CapRightsClear clears the permissions in clearrights from rights.
func CapRightsClear(rights *CapRights, clearrights []uint64) error {
// This is essentially a copy of cap_rights_vclear()
if capver(rights) != CAP_RIGHTS_VERSION_00 {
return fmt.Errorf("bad rights version %d", capver(rights))
}
n := caparsize(rights)
if n < capArSizeMin || n > capArSizeMax {
return errors.New("bad rights size")
}
for _, right := range clearrights {
if caprver(right) != CAP_RIGHTS_VERSION_00 {
return errors.New("bad right version")
}
i, err := rightToIndex(right)
if err != nil {
return err
}
if i >= n {
return errors.New("index overflow")
}
if capidxbit(rights.Rights[i]) != capidxbit(right) {
return errors.New("index mismatch")
}
rights.Rights[i] &= ^(right & 0x01FFFFFFFFFFFFFF)
if capidxbit(rights.Rights[i]) != capidxbit(right) {
return errors.New("index mismatch (after assign)")
}
}
return nil
}
// CapRightsIsSet checks whether all the permissions in setrights are present in rights.
func CapRightsIsSet(rights *CapRights, setrights []uint64) (bool, error) {
// This is essentially a copy of cap_rights_is_vset()
if capver(rights) != CAP_RIGHTS_VERSION_00 {
return false, fmt.Errorf("bad rights version %d", capver(rights))
}
n := caparsize(rights)
if n < capArSizeMin || n > capArSizeMax {
return false, errors.New("bad rights size")
}
for _, right := range setrights {
if caprver(right) != CAP_RIGHTS_VERSION_00 {
return false, errors.New("bad right version")
}
i, err := rightToIndex(right)
if err != nil {
return false, err
}
if i >= n {
return false, errors.New("index overflow")
}
if capidxbit(rights.Rights[i]) != capidxbit(right) {
return false, errors.New("index mismatch")
}
if (rights.Rights[i] & right) != right {
return false, nil
}
}
return true, nil
}
func capright(idx uint64, bit uint64) uint64 {
return ((1 << (57 + idx)) | bit)
}
// CapRightsInit returns a pointer to an initialised CapRights structure filled with rights.
// See man cap_rights_init(3) and rights(4).
func CapRightsInit(rights []uint64) (*CapRights, error) {
var r CapRights
r.Rights[0] = (capRightsGoVersion << 62) | capright(0, 0)
r.Rights[1] = capright(1, 0)
err := CapRightsSet(&r, rights)
if err != nil {
return nil, err
}
return &r, nil
}
// CapRightsLimit reduces the operations permitted on fd to at most those contained in rights.
// The capability rights on fd can never be increased by CapRightsLimit.
// See man cap_rights_limit(2) and rights(4).
func CapRightsLimit(fd uintptr, rights *CapRights) error {
return capRightsLimit(int(fd), rights)
}
// CapRightsGet returns a CapRights structure containing the operations permitted on fd.
// See man cap_rights_get(3) and rights(4).
func CapRightsGet(fd uintptr) (*CapRights, error) {
r, err := CapRightsInit(nil)
if err != nil {
return nil, err
}
err = capRightsGet(capRightsGoVersion, int(fd), r)
if err != nil {
return nil, err
}
return r, nil
}

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