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Josselin Costanzi Fix potential non-random UUIDs 75cca53 Apr 4, 2018
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@satori @alexeykudinkin
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// Copyright (C) 2013-2018 by Maxim Bublis <b@codemonkey.ru>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
package uuid
import (
"crypto/md5"
"crypto/rand"
"crypto/sha1"
"encoding/binary"
"fmt"
"hash"
"io"
"net"
"os"
"sync"
"time"
)
// Difference in 100-nanosecond intervals between
// UUID epoch (October 15, 1582) and Unix epoch (January 1, 1970).
const epochStart = 122192928000000000
type epochFunc func() time.Time
type hwAddrFunc func() (net.HardwareAddr, error)
var (
global = newRFC4122Generator()
posixUID = uint32(os.Getuid())
posixGID = uint32(os.Getgid())
)
// NewV1 returns UUID based on current timestamp and MAC address.
func NewV1() (UUID, error) {
return global.NewV1()
}
// NewV2 returns DCE Security UUID based on POSIX UID/GID.
func NewV2(domain byte) (UUID, error) {
return global.NewV2(domain)
}
// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
func NewV3(ns UUID, name string) UUID {
return global.NewV3(ns, name)
}
// NewV4 returns random generated UUID.
func NewV4() (UUID, error) {
return global.NewV4()
}
// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
func NewV5(ns UUID, name string) UUID {
return global.NewV5(ns, name)
}
// Generator provides interface for generating UUIDs.
type Generator interface {
NewV1() (UUID, error)
NewV2(domain byte) (UUID, error)
NewV3(ns UUID, name string) UUID
NewV4() (UUID, error)
NewV5(ns UUID, name string) UUID
}
// Default generator implementation.
type rfc4122Generator struct {
clockSequenceOnce sync.Once
hardwareAddrOnce sync.Once
storageMutex sync.Mutex
rand io.Reader
epochFunc epochFunc
hwAddrFunc hwAddrFunc
lastTime uint64
clockSequence uint16
hardwareAddr [6]byte
}
func newRFC4122Generator() Generator {
return &rfc4122Generator{
epochFunc: time.Now,
hwAddrFunc: defaultHWAddrFunc,
rand: rand.Reader,
}
}
// NewV1 returns UUID based on current timestamp and MAC address.
func (g *rfc4122Generator) NewV1() (UUID, error) {
u := UUID{}
timeNow, clockSeq, err := g.getClockSequence()
if err != nil {
return Nil, err
}
binary.BigEndian.PutUint32(u[0:], uint32(timeNow))
binary.BigEndian.PutUint16(u[4:], uint16(timeNow>>32))
binary.BigEndian.PutUint16(u[6:], uint16(timeNow>>48))
binary.BigEndian.PutUint16(u[8:], clockSeq)
hardwareAddr, err := g.getHardwareAddr()
if err != nil {
return Nil, err
}
copy(u[10:], hardwareAddr)
u.SetVersion(V1)
u.SetVariant(VariantRFC4122)
return u, nil
}
// NewV2 returns DCE Security UUID based on POSIX UID/GID.
func (g *rfc4122Generator) NewV2(domain byte) (UUID, error) {
u, err := g.NewV1()
if err != nil {
return Nil, err
}
switch domain {
case DomainPerson:
binary.BigEndian.PutUint32(u[:], posixUID)
case DomainGroup:
binary.BigEndian.PutUint32(u[:], posixGID)
}
u[9] = domain
u.SetVersion(V2)
u.SetVariant(VariantRFC4122)
return u, nil
}
// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
func (g *rfc4122Generator) NewV3(ns UUID, name string) UUID {
u := newFromHash(md5.New(), ns, name)
u.SetVersion(V3)
u.SetVariant(VariantRFC4122)
return u
}
// NewV4 returns random generated UUID.
func (g *rfc4122Generator) NewV4() (UUID, error) {
u := UUID{}
if _, err := io.ReadFull(g.rand, u[:]); err != nil {
return Nil, err
}
u.SetVersion(V4)
u.SetVariant(VariantRFC4122)
return u, nil
}
// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
func (g *rfc4122Generator) NewV5(ns UUID, name string) UUID {
u := newFromHash(sha1.New(), ns, name)
u.SetVersion(V5)
u.SetVariant(VariantRFC4122)
return u
}
// Returns epoch and clock sequence.
func (g *rfc4122Generator) getClockSequence() (uint64, uint16, error) {
var err error
g.clockSequenceOnce.Do(func() {
buf := make([]byte, 2)
if _, err = io.ReadFull(g.rand, buf); err != nil {
return
}
g.clockSequence = binary.BigEndian.Uint16(buf)
})
if err != nil {
return 0, 0, err
}
g.storageMutex.Lock()
defer g.storageMutex.Unlock()
timeNow := g.getEpoch()
// Clock didn't change since last UUID generation.
// Should increase clock sequence.
if timeNow <= g.lastTime {
g.clockSequence++
}
g.lastTime = timeNow
return timeNow, g.clockSequence, nil
}
// Returns hardware address.
func (g *rfc4122Generator) getHardwareAddr() ([]byte, error) {
var err error
g.hardwareAddrOnce.Do(func() {
if hwAddr, err := g.hwAddrFunc(); err == nil {
copy(g.hardwareAddr[:], hwAddr)
return
}
// Initialize hardwareAddr randomly in case
// of real network interfaces absence.
if _, err = io.ReadFull(g.rand, g.hardwareAddr[:]); err != nil {
return
}
// Set multicast bit as recommended by RFC 4122
g.hardwareAddr[0] |= 0x01
})
if err != nil {
return []byte{}, err
}
return g.hardwareAddr[:], nil
}
// Returns difference in 100-nanosecond intervals between
// UUID epoch (October 15, 1582) and current time.
func (g *rfc4122Generator) getEpoch() uint64 {
return epochStart + uint64(g.epochFunc().UnixNano()/100)
}
// Returns UUID based on hashing of namespace UUID and name.
func newFromHash(h hash.Hash, ns UUID, name string) UUID {
u := UUID{}
h.Write(ns[:])
h.Write([]byte(name))
copy(u[:], h.Sum(nil))
return u
}
// Returns hardware address.
func defaultHWAddrFunc() (net.HardwareAddr, error) {
ifaces, err := net.Interfaces()
if err != nil {
return []byte{}, err
}
for _, iface := range ifaces {
if len(iface.HardwareAddr) >= 6 {
return iface.HardwareAddr, nil
}
}
return []byte{}, fmt.Errorf("uuid: no HW address found")
}
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