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// Copyright 2016 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.
package unix
import (
"errors"
"fmt"
"strconv"
"syscall"
"unsafe"
)
// Pledge implements the pledge syscall.
//
// The pledge syscall does not accept execpromises on OpenBSD releases
// before 6.3.
//
// execpromises must be empty when Pledge is called on OpenBSD
// releases predating 6.3, otherwise an error will be returned.
//
// For more information see pledge(2).
func Pledge(promises, execpromises string) error {
maj, min, err := majmin()
if err != nil {
return err
}
err = pledgeAvailable(maj, min, execpromises)
if err != nil {
return err
}
pptr, err := syscall.BytePtrFromString(promises)
if err != nil {
return err
}
// This variable will hold either a nil unsafe.Pointer or
// an unsafe.Pointer to a string (execpromises).
var expr unsafe.Pointer
// If we're running on OpenBSD > 6.2, pass execpromises to the syscall.
if maj > 6 || (maj == 6 && min > 2) {
exptr, err := syscall.BytePtrFromString(execpromises)
if err != nil {
return err
}
expr = unsafe.Pointer(exptr)
}
_, _, e := syscall.Syscall(SYS_PLEDGE, uintptr(unsafe.Pointer(pptr)), uintptr(expr), 0)
if e != 0 {
return e
}
return nil
}
// PledgePromises implements the pledge syscall.
//
// This changes the promises and leaves the execpromises untouched.
//
// For more information see pledge(2).
func PledgePromises(promises string) error {
maj, min, err := majmin()
if err != nil {
return err
}
err = pledgeAvailable(maj, min, "")
if err != nil {
return err
}
// This variable holds the execpromises and is always nil.
var expr unsafe.Pointer
pptr, err := syscall.BytePtrFromString(promises)
if err != nil {
return err
}
_, _, e := syscall.Syscall(SYS_PLEDGE, uintptr(unsafe.Pointer(pptr)), uintptr(expr), 0)
if e != 0 {
return e
}
return nil
}
// PledgeExecpromises implements the pledge syscall.
//
// This changes the execpromises and leaves the promises untouched.
//
// For more information see pledge(2).
func PledgeExecpromises(execpromises string) error {
maj, min, err := majmin()
if err != nil {
return err
}
err = pledgeAvailable(maj, min, execpromises)
if err != nil {
return err
}
// This variable holds the promises and is always nil.
var pptr unsafe.Pointer
exptr, err := syscall.BytePtrFromString(execpromises)
if err != nil {
return err
}
_, _, e := syscall.Syscall(SYS_PLEDGE, uintptr(pptr), uintptr(unsafe.Pointer(exptr)), 0)
if e != 0 {
return e
}
return nil
}
// majmin returns major and minor version number for an OpenBSD system.
func majmin() (major int, minor int, err error) {
var v Utsname
err = Uname(&v)
if err != nil {
return
}
major, err = strconv.Atoi(string(v.Release[0]))
if err != nil {
err = errors.New("cannot parse major version number returned by uname")
return
}
minor, err = strconv.Atoi(string(v.Release[2]))
if err != nil {
err = errors.New("cannot parse minor version number returned by uname")
return
}
return
}
// pledgeAvailable checks for availability of the pledge(2) syscall
// based on the running OpenBSD version.
func pledgeAvailable(maj, min int, execpromises string) error {
// If OpenBSD <= 5.9, pledge is not available.
if (maj == 5 && min != 9) || maj < 5 {
return fmt.Errorf("pledge syscall is not available on OpenBSD %d.%d", maj, min)
}
// If OpenBSD <= 6.2 and execpromises is not empty,
// return an error - execpromises is not available before 6.3
if (maj < 6 || (maj == 6 && min <= 2)) && execpromises != "" {
return fmt.Errorf("cannot use execpromises on OpenBSD %d.%d", maj, min)
}
return nil
}
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