Adding methods to allow to get UUIDs with random MAC address

README.md

@@ -10,7 +10,9 @@ With 100% test coverage and benchmarks out of box.
 
 Supported versions:
 * Version 1, based on timestamp and MAC address (RFC 4122)
+* Version 1, based on timestamp and a random MAC address (RFC 4122)
 * Version 2, based on timestamp, MAC address and POSIX UID/GID (DCE 1.1)
+* Version 2, based on timestamp, random MAC address and POSIX UID/GID (DCE 1.1)
 * Version 3, based on MD5 hashing (RFC 4122)
 * Version 4, based on random numbers (RFC 4122)
 * Version 5, based on SHA-1 hashing (RFC 4122)

uuid.go

@@ -64,14 +64,16 @@ const dash byte = '-'
 
 // UUID v1/v2 storage.
 var (
-	storageMutex  sync.Mutex
-	storageOnce   sync.Once
-	epochFunc     = unixTimeFunc
-	clockSequence uint16
-	lastTime      uint64
-	hardwareAddr  [6]byte
-	posixUID      = uint32(os.Getuid())
-	posixGID      = uint32(os.Getgid())
+	storageMutex              sync.Mutex
+	storageOnce               sync.Once
+	storageRandomMACAddrMutex sync.Mutex
+	storageRandomMACAddrOnce  sync.Once
+	epochFunc                 = unixTimeFunc
+	clockSequence             uint16
+	lastTime                  uint64
+	hardwareAddr              [6]byte
+	posixUID                  = uint32(os.Getuid())
+	posixGID                  = uint32(os.Getgid())
 )
 
 // String parse helpers.
@@ -105,9 +107,12 @@ func initHardwareAddr() {
 	hardwareAddr[0] |= 0x01
 }
 
-func initStorage() {
-	initClockSequence()
-	initHardwareAddr()
+func initHardwareRandomAddr() {
+	// Initialize hardwareAddr randomly
+	safeRandom(hardwareAddr[:])
+
+	// Set multicast bit as recommended in RFC 4122
+	hardwareAddr[0] |= 0x01
 }
 
 func safeRandom(dest []byte) {
@@ -378,6 +383,16 @@ func FromStringOrNil(input string) UUID {
 	return uuid
 }
 
+func initStorage() {
+	initClockSequence()
+	initHardwareAddr()
+}
+
+func initStorageRandomAddr() {
+	initClockSequence()
+	initHardwareRandomAddr()
+}
+
 // Returns UUID v1/v2 storage state.
 // Returns epoch timestamp, clock sequence, and hardware address.
 func getStorage() (uint64, uint16, []byte) {
@@ -397,31 +412,63 @@ func getStorage() (uint64, uint16, []byte) {
 	return timeNow, clockSequence, hardwareAddr[:]
 }
 
+// Returns UUID v1/v2 storage state.
+// Returns epoch timestamp, clock sequence, and a random hardware address.
+func getStorageRandomAddr() (uint64, uint16, []byte) {
+	storageRandomMACAddrOnce.Do(initStorageRandomAddr)
+
+	storageRandomMACAddrMutex.Lock()
+	defer storageRandomMACAddrMutex.Unlock()
+
+	timeNow := epochFunc()
+	// Clock changed backwards since last UUID generation.
+	// Should increase clock sequence.
+	if timeNow <= lastTime {
+		clockSequence++
+	}
+	lastTime = timeNow
+
+	return timeNow, clockSequence, hardwareAddr[:]
+}
+
 // NewV1 returns UUID based on current timestamp and MAC address.
 func NewV1() UUID {
-	u := UUID{}
-
 	timeNow, clockSeq, hardwareAddr := getStorage()
+	return buildV1(timeNow, clockSeq, hardwareAddr)
+}
+
+// NewV1RandomMAC returns UUID based on current timestamp and a random MAC address.
+func NewV1RandomMAC() UUID {
+	timeNow, clockSeq, hardwareAddr := getStorageRandomAddr()
+	return buildV1(timeNow, clockSeq, hardwareAddr)
+}
 
+func buildV1(timeNow uint64, clockSeq uint16, hardwareAddr []byte) UUID {
+	u := UUID{}
 	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)
-
 	copy(u[10:], hardwareAddr)
-
 	u.SetVersion(1)
 	u.SetVariant()
-
 	return u
 }
 
 // NewV2 returns DCE Security UUID based on POSIX UID/GID.
 func NewV2(domain byte) UUID {
-	u := UUID{}
-
 	timeNow, clockSeq, hardwareAddr := getStorage()
+	return buildV2(domain, timeNow, clockSeq, hardwareAddr)
+}
+
+// NewV2RandomMAC returns DCE Security UUID based on POSIX UID/GID using a random MAC
+func NewV2RandomMAC(domain byte) UUID {
+	timeNow, clockSeq, hardwareAddr := getStorageRandomAddr()
+	return buildV2(domain, timeNow, clockSeq, hardwareAddr)
+}
 
+func buildV2(domain byte, timeNow uint64, clockSeq uint16, hardwareAddr []byte) UUID {
+	u := UUID{}
 	switch domain {
 	case DomainPerson:
 		binary.BigEndian.PutUint32(u[0:], posixUID)
@@ -438,7 +485,6 @@ func NewV2(domain byte) UUID {
 
 	u.SetVersion(2)
 	u.SetVariant()
-
 	return u
 }
 

uuid_test.go

@@ -23,6 +23,7 @@ package uuid
 
 import (
 	"bytes"
+	"net"
 	"testing"
 )
 
@@ -526,6 +527,45 @@ func TestNewV1(t *testing.T) {
 	epochFunc = oldFunc
 }
 
+func TestNewV1RandomMAC(t *testing.T) {
+	u := NewV1RandomMAC()
+
+	if u.Version() != 1 {
+		t.Errorf("UUIDv1 generated with incorrect version: %d", u.Version())
+	}
+
+	if u.Variant() != VariantRFC4122 {
+		t.Errorf("UUIDv1 generated with incorrect variant: %d", u.Variant())
+	}
+
+	u1 := NewV1RandomMAC()
+	u2 := NewV1RandomMAC()
+
+	if Equal(u1, u2) {
+		t.Errorf("UUIDv1 generated two equal UUIDs: %s and %s", u1, u2)
+	}
+
+	oldFunc := epochFunc
+	epochFunc = func() uint64 { return 0 }
+
+	u3 := NewV1RandomMAC()
+	u4 := NewV1RandomMAC()
+
+	if Equal(u3, u4) {
+		t.Errorf("UUIDv1 generated two equal UUIDs: %s and %s", u3, u4)
+	}
+
+	epochFunc = oldFunc
+
+	u5 := NewV1RandomMAC().Bytes()
+	u5MACAddr := u5[10:]
+	firstNetworkCardAddress := getNetworkCardAddress()
+
+	if bytes.Equal(u5MACAddr, firstNetworkCardAddress) {
+		t.Errorf("UUIDv1 generated two equal MAC addresses when should be random: %v and %v", u5MACAddr, firstNetworkCardAddress)
+	}
+}
+
 func TestNewV2(t *testing.T) {
 	u1 := NewV2(DomainPerson)
 
@@ -548,6 +588,36 @@ func TestNewV2(t *testing.T) {
 	}
 }
 
+func TestNewV2RandomMAC(t *testing.T) {
+	u1 := NewV2RandomMAC(DomainPerson)
+
+	if u1.Version() != 2 {
+		t.Errorf("UUIDv2 generated with incorrect version: %d", u1.Version())
+	}
+
+	if u1.Variant() != VariantRFC4122 {
+		t.Errorf("UUIDv2 generated with incorrect variant: %d", u1.Variant())
+	}
+
+	u2 := NewV2RandomMAC(DomainGroup)
+
+	if u2.Version() != 2 {
+		t.Errorf("UUIDv2 generated with incorrect version: %d", u2.Version())
+	}
+
+	if u2.Variant() != VariantRFC4122 {
+		t.Errorf("UUIDv2 generated with incorrect variant: %d", u2.Variant())
+	}
+
+	u3 := NewV2RandomMAC(DomainPerson).Bytes()
+	u3MACAddr := u3[10:]
+	firstNetworkCardAddress := getNetworkCardAddress()
+
+	if bytes.Equal(u3MACAddr, firstNetworkCardAddress) {
+		t.Errorf("UUIDv2 generated two equal MAC addresses when should be random: %v and %v", u3MACAddr, firstNetworkCardAddress)
+	}
+}
+
 func TestNewV3(t *testing.T) {
 	u := NewV3(NamespaceDNS, "www.example.com")
 
@@ -631,3 +701,15 @@ func TestNewV5(t *testing.T) {
 		t.Errorf("UUIDv3 generated same UUIDs for sane names in different namespaces: %s and %s", u1, u4)
 	}
 }
+
+func getNetworkCardAddress() []byte {
+	interfaces, err := net.Interfaces()
+	if err == nil {
+		for _, iface := range interfaces {
+			if len(iface.HardwareAddr) >= 6 {
+				return iface.HardwareAddr
+			}
+		}
+	}
+	return []byte{}
+}