path: root/vendor/golang.org/x/sys/unix/openbsd_pledge.go

// 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
}