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