1// Copyright (C) 2013-2018 by Maxim Bublis <b@codemonkey.ru>
2//
3// Permission is hereby granted, free of charge, to any person obtaining
4// a copy of this software and associated documentation files (the
5// "Software"), to deal in the Software without restriction, including
6// without limitation the rights to use, copy, modify, merge, publish,
7// distribute, sublicense, and/or sell copies of the Software, and to
8// permit persons to whom the Software is furnished to do so, subject to
9// the following conditions:
10//
11// The above copyright notice and this permission notice shall be
12// included in all copies or substantial portions of the Software.
13//
14// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
15// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
17// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
18// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
19// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
20// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
21
22package uuid
23
24import (
25	"crypto/md5"
26	"crypto/rand"
27	"crypto/sha1"
28	"encoding/binary"
29	"hash"
30	"net"
31	"os"
32	"sync"
33	"time"
34)
35
36// Difference in 100-nanosecond intervals between
37// UUID epoch (October 15, 1582) and Unix epoch (January 1, 1970).
38const epochStart = 122192928000000000
39
40var (
41	global = newDefaultGenerator()
42
43	epochFunc = unixTimeFunc
44	posixUID  = uint32(os.Getuid())
45	posixGID  = uint32(os.Getgid())
46)
47
48// NewV1 returns UUID based on current timestamp and MAC address.
49func NewV1() UUID {
50	return global.NewV1()
51}
52
53// NewV2 returns DCE Security UUID based on POSIX UID/GID.
54func NewV2(domain byte) UUID {
55	return global.NewV2(domain)
56}
57
58// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
59func NewV3(ns UUID, name string) UUID {
60	return global.NewV3(ns, name)
61}
62
63// NewV4 returns random generated UUID.
64func NewV4() UUID {
65	return global.NewV4()
66}
67
68// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
69func NewV5(ns UUID, name string) UUID {
70	return global.NewV5(ns, name)
71}
72
73// Generator provides interface for generating UUIDs.
74type Generator interface {
75	NewV1() UUID
76	NewV2(domain byte) UUID
77	NewV3(ns UUID, name string) UUID
78	NewV4() UUID
79	NewV5(ns UUID, name string) UUID
80}
81
82// Default generator implementation.
83type generator struct {
84	storageOnce  sync.Once
85	storageMutex sync.Mutex
86
87	lastTime      uint64
88	clockSequence uint16
89	hardwareAddr  [6]byte
90}
91
92func newDefaultGenerator() Generator {
93	return &generator{}
94}
95
96// NewV1 returns UUID based on current timestamp and MAC address.
97func (g *generator) NewV1() UUID {
98	u := UUID{}
99
100	timeNow, clockSeq, hardwareAddr := g.getStorage()
101
102	binary.BigEndian.PutUint32(u[0:], uint32(timeNow))
103	binary.BigEndian.PutUint16(u[4:], uint16(timeNow>>32))
104	binary.BigEndian.PutUint16(u[6:], uint16(timeNow>>48))
105	binary.BigEndian.PutUint16(u[8:], clockSeq)
106
107	copy(u[10:], hardwareAddr)
108
109	u.SetVersion(V1)
110	u.SetVariant(VariantRFC4122)
111
112	return u
113}
114
115// NewV2 returns DCE Security UUID based on POSIX UID/GID.
116func (g *generator) NewV2(domain byte) UUID {
117	u := UUID{}
118
119	timeNow, clockSeq, hardwareAddr := g.getStorage()
120
121	switch domain {
122	case DomainPerson:
123		binary.BigEndian.PutUint32(u[0:], posixUID)
124	case DomainGroup:
125		binary.BigEndian.PutUint32(u[0:], posixGID)
126	}
127
128	binary.BigEndian.PutUint16(u[4:], uint16(timeNow>>32))
129	binary.BigEndian.PutUint16(u[6:], uint16(timeNow>>48))
130	binary.BigEndian.PutUint16(u[8:], clockSeq)
131	u[9] = domain
132
133	copy(u[10:], hardwareAddr)
134
135	u.SetVersion(V2)
136	u.SetVariant(VariantRFC4122)
137
138	return u
139}
140
141// NewV3 returns UUID based on MD5 hash of namespace UUID and name.
142func (g *generator) NewV3(ns UUID, name string) UUID {
143	u := newFromHash(md5.New(), ns, name)
144	u.SetVersion(V3)
145	u.SetVariant(VariantRFC4122)
146
147	return u
148}
149
150// NewV4 returns random generated UUID.
151func (g *generator) NewV4() UUID {
152	u := UUID{}
153	g.safeRandom(u[:])
154	u.SetVersion(V4)
155	u.SetVariant(VariantRFC4122)
156
157	return u
158}
159
160// NewV5 returns UUID based on SHA-1 hash of namespace UUID and name.
161func (g *generator) NewV5(ns UUID, name string) UUID {
162	u := newFromHash(sha1.New(), ns, name)
163	u.SetVersion(V5)
164	u.SetVariant(VariantRFC4122)
165
166	return u
167}
168
169func (g *generator) initStorage() {
170	g.initClockSequence()
171	g.initHardwareAddr()
172}
173
174func (g *generator) initClockSequence() {
175	buf := make([]byte, 2)
176	g.safeRandom(buf)
177	g.clockSequence = binary.BigEndian.Uint16(buf)
178}
179
180func (g *generator) initHardwareAddr() {
181	interfaces, err := net.Interfaces()
182	if err == nil {
183		for _, iface := range interfaces {
184			if len(iface.HardwareAddr) >= 6 {
185				copy(g.hardwareAddr[:], iface.HardwareAddr)
186				return
187			}
188		}
189	}
190
191	// Initialize hardwareAddr randomly in case
192	// of real network interfaces absence
193	g.safeRandom(g.hardwareAddr[:])
194
195	// Set multicast bit as recommended in RFC 4122
196	g.hardwareAddr[0] |= 0x01
197}
198
199func (g *generator) safeRandom(dest []byte) {
200	if _, err := rand.Read(dest); err != nil {
201		panic(err)
202	}
203}
204
205// Returns UUID v1/v2 storage state.
206// Returns epoch timestamp, clock sequence, and hardware address.
207func (g *generator) getStorage() (uint64, uint16, []byte) {
208	g.storageOnce.Do(g.initStorage)
209
210	g.storageMutex.Lock()
211	defer g.storageMutex.Unlock()
212
213	timeNow := epochFunc()
214	// Clock changed backwards since last UUID generation.
215	// Should increase clock sequence.
216	if timeNow <= g.lastTime {
217		g.clockSequence++
218	}
219	g.lastTime = timeNow
220
221	return timeNow, g.clockSequence, g.hardwareAddr[:]
222}
223
224// Returns difference in 100-nanosecond intervals between
225// UUID epoch (October 15, 1582) and current time.
226// This is default epoch calculation function.
227func unixTimeFunc() uint64 {
228	return epochStart + uint64(time.Now().UnixNano()/100)
229}
230
231// Returns UUID based on hashing of namespace UUID and name.
232func newFromHash(h hash.Hash, ns UUID, name string) UUID {
233	u := UUID{}
234	h.Write(ns[:])
235	h.Write([]byte(name))
236	copy(u[:], h.Sum(nil))
237
238	return u
239}
240