text: // 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.
  
  // +build openbsd
  // +build 386 amd64 arm
  
  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
  }
  