unix/unveil_openbsd.go

// Copyright 2018 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 (
	"fmt"
	"syscall"
	"unsafe"
)

// Unveil implements the unveil syscall.
// For more information see unveil(2).
// Note that the special case of blocking further
// unveil calls is handled by UnveilBlock.
func Unveil(path string, flags string) error {
	if err := supportsUnveil(); err != nil {
		return err
	}
	pathPtr, err := syscall.BytePtrFromString(path)
	if err != nil {
		return err
	}
	flagsPtr, err := syscall.BytePtrFromString(flags)
	if err != nil {
		return err
	}
	_, _, e := syscall.Syscall(SYS_UNVEIL, uintptr(unsafe.Pointer(pathPtr)), uintptr(unsafe.Pointer(flagsPtr)), 0)
	if e != 0 {
		return e
	}
	return nil
}

// UnveilBlock blocks future unveil calls.
// For more information see unveil(2).
func UnveilBlock() error {
	if err := supportsUnveil(); err != nil {
		return err
	}
	// Both pointers must be nil.
	var pathUnsafe, flagsUnsafe unsafe.Pointer
	_, _, e := syscall.Syscall(SYS_UNVEIL, uintptr(pathUnsafe), uintptr(flagsUnsafe), 0)
	if e != 0 {
		return e
	}
	return nil
}

// supportsUnveil checks for availability of the unveil(2) system call based
// on the running OpenBSD version.
func supportsUnveil() error {
	maj, min, err := majmin()
	if err != nil {
		return err
	}

	// unveil is not available before 6.4
	if maj < 6 || (maj == 6 && min <= 3) {
		return fmt.Errorf("cannot call Unveil on OpenBSD %d.%d", maj, min)
	}

	return nil
}