guid: Add V5 GUID support

Signed-off-by: Kevin Parsons <kevpar@microsoft.com>

pkg/guid/guid.go

@@ -7,6 +7,7 @@ package guid
 
 import (
 	"crypto/rand"
+	"crypto/sha1"
 	"encoding"
 	"encoding/binary"
 	"fmt"
@@ -59,6 +60,29 @@ func NewV4() (GUID, error) {
 	return g, nil
 }
 
+// NewV5 returns a new version 5 (generated from a string via SHA-1 hashing)
+// GUID, as defined by RFC 4122. The RFC is unclear on the encoding of the name,
+// and the sample code treats it as a series of bytes, so we do the same here.
+//
+// Some implementations, such as those found on Windows, treat the name as a
+// big-endian UTF16 stream of bytes. If that is desired, the string can be
+// encoded as such before being passed to this function.
+func NewV5(namespace GUID, name []byte) (GUID, error) {
+	b := sha1.New()
+	namespaceBytes := namespace.ToArray()
+	b.Write(namespaceBytes[:])
+	b.Write(name)
+
+	a := [16]byte{}
+	copy(a[:], b.Sum(nil))
+
+	g := FromArray(a)
+	g.setVersion(5) // Version 5 means generated from a string.
+	g.setVariant(VariantRFC4122)
+
+	return g, nil
+}
+
 func fromArray(b [16]byte, order binary.ByteOrder) GUID {
 	var g GUID
 	g.Data1 = order.Uint32(b[0:4])

pkg/guid/guid_test.go

@@ -14,6 +14,14 @@ func mustNewV4(t *testing.T) GUID {
 	return g
 }
 
+func mustNewV5(t *testing.T, namespace GUID, name []byte) GUID {
+	g, err := NewV5(namespace, name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return g
+}
+
 func mustFromString(t *testing.T, s string) GUID {
 	g, err := FromString(s)
 	if err != nil {
@@ -112,6 +120,53 @@ func Test_V4HasCorrectVersionAndVariant(t *testing.T) {
 	}
 }
 
+func Test_V5HasCorrectVersionAndVariant(t *testing.T) {
+	namespace := mustFromString(t, "f5cbc1a9-4cba-45a0-bfdd-b6761fc7dcc0")
+	g := mustNewV5(t, namespace, []byte("Foo"))
+	if g.Version() != 5 {
+		t.Fatalf("Version is not 5: %s", g)
+	}
+	if g.Variant() != VariantRFC4122 {
+		t.Fatalf("Variant is not RFC4122: %s", g)
+	}
+}
+
+func Test_V5KnownValues(t *testing.T) {
+	type testCase struct {
+		ns   GUID
+		name string
+		g    GUID
+	}
+	testCases := []testCase{
+		{
+			mustFromString(t, "6ba7b810-9dad-11d1-80b4-00c04fd430c8"),
+			"www.sample.com",
+			mustFromString(t, "4e4463eb-b0e8-54fa-8c28-12d1ab1d45b3"),
+		},
+		{
+			mustFromString(t, "6ba7b811-9dad-11d1-80b4-00c04fd430c8"),
+			"https://www.sample.com/test",
+			mustFromString(t, "9e44625a-0d85-5e0a-99bc-8e8a77df5ea2"),
+		},
+		{
+			mustFromString(t, "6ba7b812-9dad-11d1-80b4-00c04fd430c8"),
+			"1.3.6.1.4.1.343",
+			mustFromString(t, "6aab0456-7392-582a-b92a-ba5a7096945d"),
+		},
+		{
+			mustFromString(t, "6ba7b814-9dad-11d1-80b4-00c04fd430c8"),
+			"CN=John Smith, ou=People, o=FakeCorp, L=Seattle, S=Washington, C=US",
+			mustFromString(t, "badff8dd-c869-5b64-a260-00092e66be00"),
+		},
+	}
+	for _, tc := range testCases {
+		g := mustNewV5(t, tc.ns, []byte(tc.name))
+		if g != tc.g {
+			t.Fatalf("GUIDs are not equal.\nExpected: %s\nActual: %s", tc.g, g)
+		}
+	}
+}
+
 func Test_ToArray(t *testing.T) {
 	g := mustFromString(t, "73c39589-192e-4c64-9acf-6c5d0aa18528")
 	b := g.ToArray()