pledge_openbsd.go

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package unix
     6  
     7  import (
     8  	"errors"
     9  	"fmt"
    10  	"strconv"
    11  	"syscall"
    12  	"unsafe"
    13  )
    14  
    15  // Pledge implements the pledge syscall.
    16  //
    17  // The pledge syscall does not accept execpromises on OpenBSD releases
    18  // before 6.3.
    19  //
    20  // execpromises must be empty when Pledge is called on OpenBSD
    21  // releases predating 6.3, otherwise an error will be returned.
    22  //
    23  // For more information see pledge(2).
    24  func Pledge(promises, execpromises string) error {
    25  	maj, min, err := majmin()
    26  	if err != nil {
    27  		return err
    28  	}
    29  
    30  	err = pledgeAvailable(maj, min, execpromises)
    31  	if err != nil {
    32  		return err
    33  	}
    34  
    35  	pptr, err := syscall.BytePtrFromString(promises)
    36  	if err != nil {
    37  		return err
    38  	}
    39  
    40  	// This variable will hold either a nil unsafe.Pointer or
    41  	// an unsafe.Pointer to a string (execpromises).
    42  	var expr unsafe.Pointer
    43  
    44  	// If we're running on OpenBSD > 6.2, pass execpromises to the syscall.
    45  	if maj > 6 || (maj == 6 && min > 2) {
    46  		exptr, err := syscall.BytePtrFromString(execpromises)
    47  		if err != nil {
    48  			return err
    49  		}
    50  		expr = unsafe.Pointer(exptr)
    51  	}
    52  
    53  	_, _, e := syscall.Syscall(SYS_PLEDGE, uintptr(unsafe.Pointer(pptr)), uintptr(expr), 0)
    54  	if e != 0 {
    55  		return e
    56  	}
    57  
    58  	return nil
    59  }
    60  
    61  // PledgePromises implements the pledge syscall.
    62  //
    63  // This changes the promises and leaves the execpromises untouched.
    64  //
    65  // For more information see pledge(2).
    66  func PledgePromises(promises string) error {
    67  	maj, min, err := majmin()
    68  	if err != nil {
    69  		return err
    70  	}
    71  
    72  	err = pledgeAvailable(maj, min, "")
    73  	if err != nil {
    74  		return err
    75  	}
    76  
    77  	// This variable holds the execpromises and is always nil.
    78  	var expr unsafe.Pointer
    79  
    80  	pptr, err := syscall.BytePtrFromString(promises)
    81  	if err != nil {
    82  		return err
    83  	}
    84  
    85  	_, _, e := syscall.Syscall(SYS_PLEDGE, uintptr(unsafe.Pointer(pptr)), uintptr(expr), 0)
    86  	if e != 0 {
    87  		return e
    88  	}
    89  
    90  	return nil
    91  }
    92  
    93  // PledgeExecpromises implements the pledge syscall.
    94  //
    95  // This changes the execpromises and leaves the promises untouched.
    96  //
    97  // For more information see pledge(2).
    98  func PledgeExecpromises(execpromises string) error {
    99  	maj, min, err := majmin()
   100  	if err != nil {
   101  		return err
   102  	}
   103  
   104  	err = pledgeAvailable(maj, min, execpromises)
   105  	if err != nil {
   106  		return err
   107  	}
   108  
   109  	// This variable holds the promises and is always nil.
   110  	var pptr unsafe.Pointer
   111  
   112  	exptr, err := syscall.BytePtrFromString(execpromises)
   113  	if err != nil {
   114  		return err
   115  	}
   116  
   117  	_, _, e := syscall.Syscall(SYS_PLEDGE, uintptr(pptr), uintptr(unsafe.Pointer(exptr)), 0)
   118  	if e != 0 {
   119  		return e
   120  	}
   121  
   122  	return nil
   123  }
   124  
   125  // majmin returns major and minor version number for an OpenBSD system.
   126  func majmin() (major int, minor int, err error) {
   127  	var v Utsname
   128  	err = Uname(&v)
   129  	if err != nil {
   130  		return
   131  	}
   132  
   133  	major, err = strconv.Atoi(string(v.Release[0]))
   134  	if err != nil {
   135  		err = errors.New("cannot parse major version number returned by uname")
   136  		return
   137  	}
   138  
   139  	minor, err = strconv.Atoi(string(v.Release[2]))
   140  	if err != nil {
   141  		err = errors.New("cannot parse minor version number returned by uname")
   142  		return
   143  	}
   144  
   145  	return
   146  }
   147  
   148  // pledgeAvailable checks for availability of the pledge(2) syscall
   149  // based on the running OpenBSD version.
   150  func pledgeAvailable(maj, min int, execpromises string) error {
   151  	// If OpenBSD <= 5.9, pledge is not available.
   152  	if (maj == 5 && min != 9) || maj < 5 {
   153  		return fmt.Errorf("pledge syscall is not available on OpenBSD %d.%d", maj, min)
   154  	}
   155  
   156  	// If OpenBSD <= 6.2 and execpromises is not empty,
   157  	// return an error - execpromises is not available before 6.3
   158  	if (maj < 6 || (maj == 6 && min <= 2)) && execpromises != "" {
   159  		return fmt.Errorf("cannot use execpromises on OpenBSD %d.%d", maj, min)
   160  	}
   161  
   162  	return nil
   163  }
   164
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