Zack Williams | e940c7a | 2019-08-21 14:25:39 -0700 | [diff] [blame] | 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 | } |