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// Copyright 2016 Luke Shumaker
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package sd_id128 provides functions for dealing with 128-bit IDs.
package sd_id128
import (
"crypto/rand"
"errors"
"os"
"strings"
)
var (
ErrInvalid = errors.New("Invalid ID")
ErrNone = errors.New("No Invocation ID set")
)
type ID128 [16]byte
// String formats the ID as a hexadecimal number.
func (id ID128) String() string {
var s [32]byte
for n := range id {
s[n*2] = hexchar(id[n] >> 4)
s[n*2+1] = hexchar(id[n] & 0xF)
}
return string(s[:])
}
// UUID formats the ID as a UUID string.
func (id ID128) UUID() string {
var s [36]byte
k := 0
for n := range id {
switch n {
case 4, 6, 8, 10:
s[k] = '-'
k++
}
s[k] = hexchar(id[n] >> 4)
k++
s[k] = hexchar(id[n] & 0xF)
k++
}
return string(s[:])
}
// Parse parses a 128-bit ID represented either as a hexadecimal
// number, or as a UUID string (that is, a hexadecimal number with
// hyphens inserted at positions 8, 12, 18, and 23).
func Parse(s string) (ID128, error) {
ret := ID128{}
isGuid := false
i := 0
n := 0
for n < 16 {
if s[i] == '-' {
if i == 8 {
isGuid = true
} else if i == 13 || i == 18 || i == 23 {
if !isGuid {
return ID128{}, ErrInvalid
}
} else {
return ID128{}, ErrInvalid
}
i++
} else {
if i+2 >= len(s) {
return ID128{}, ErrInvalid
}
a, err := unhexchar(s[i])
i++
if err != nil {
return ID128{}, err
}
b, err := unhexchar(s[i])
i++
if err != nil {
return ID128{}, err
}
ret[n] = (a << 4) | b
n++
}
}
if !((i == 36 && isGuid) || (i == 32 && !isGuid)) {
return ID128{}, ErrInvalid
}
if i != len(s) {
return ID128{}, ErrInvalid
}
return ret, nil
}
// ParsePlain is like Parse, but only accepts hexadecimal numbers, not
// UUID-formatted strings.
func ParsePlain(s string) (ID128, error) {
if len(s) != 32 {
return ID128{}, ErrInvalid
}
return Parse(s)
}
// ParseUUID is like Parse, but only accepts UUID-formatted strings,
// not hexadecimal numbers.
func ParseUUID(s string) (ID128, error) {
if len(s) != 36 {
return ID128{}, ErrInvalid
}
return Parse(s)
}
// GetRandomID generates a random v4 UUID (122 random bits).
func GetRandomID() (ID128, error) {
var id ID128
_, err := rand.Read(id[:])
if err != nil {
return ID128{}, err
}
// Turn this in to a valid v4 UUID, to be nice.
// Set UUID version to 4 --- truly random generation
id[6] = (id[6] & 0x0F) | 0x40
// Set the UUID variant to DCE
id[8] = (id[8] & 0x3F) | 0x80
return id, nil
}
var cachedMachineID ID128
// GetMachineID returns a unique identifier for this machine.
//
// This is read as a plain hexadecimal number (with an optional
// trailing newline) from "/etc/machine-id".
func GetMachineID() (ID128, error) {
if cachedMachineID == (ID128{}) {
str, err := readfile("/etc/machine-id")
if err != nil {
return ID128{}, err
}
id, err := ParsePlain(strings.TrimSuffix(str, "\n"))
if err != nil {
return ID128{}, err
}
if id == (ID128{}) {
return ID128{}, ErrInvalid
}
cachedMachineID = id
}
return cachedMachineID, nil
}
var cachedBootID ID128
// GetBootID returns a unique identifier for this boot.
//
// This is read as a UUID (with trailing newline) from
// "/proc/sys/kernel/random/boot_id".
func GetBootID() (ID128, error) {
if cachedBootID == (ID128{}) {
str, err := readfile("/proc/sys/kernel/random/boot_id")
if err != nil {
return ID128{}, err
}
id, err := ParseUUID(strings.TrimSuffix(str, "\n"))
if err != nil {
return ID128{}, err
}
cachedBootID = id
}
return cachedBootID, nil
}
var cachedInvocationID ID128
// GetInvocationID returns a unique identifier for this invocation of
// the currently executed service.
//
// This is read from the "INVOCATION_ID" environment variable, which
// is expected to be set by the service manager.
//
// The error returned is ErrNone if the service manager did not set
// INVOCATION_ID, or ErrInvalid if the value of INVOCATION_ID could
// not be parsed.
func GetInvocationID() (ID128, error) {
if cachedInvocationID == (ID128{}) {
// BUG(lukeshu): GetInvocationID should distrust the
// environment in certain situations, similarly to GNU
// libc secure_getenv.
str, have := os.LookupEnv("INVOCATION_ID")
if !have {
return ID128{}, ErrNone
}
t, err := Parse(str)
if err != nil {
return ID128{}, err
}
cachedInvocationID = t
}
return cachedInvocationID, nil
}
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