etw: Add test for provider name to GUID conversion

Also simplified the name to GUID conversion code, and improved the
comments.

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

pkg/etw/provider.go

@@ -94,26 +94,27 @@ func providerCallbackAdapter(sourceID *guid.GUID, state uintptr, level uintptr,
 // uses the same algorithm as used by .NET's EventSource class, which is based
 // on RFC 4122. More information on the algorithm can be found here:
 // https://blogs.msdn.microsoft.com/dcook/2015/09/08/etw-provider-names-and-guids/
-// The algorithm is roughly:
-// Hash = Sha1(namespace + arg.ToUpper().ToUtf16be())
-// Guid = Hash[0..15], with Hash[7] tweaked according to RFC 4122
+//
+// The algorithm is roughly the RFC 4122 algorithm for a V5 UUID, but differs in
+// the following ways:
+// - The input name is first upper-cased, UTF16-encoded, and converted to
+//   big-endian.
+// - No variant is set on the result UUID.
+// - The result UUID is treated as being in little-endian format, rather than
+//   big-endian.
 func providerIDFromName(name string) guid.GUID {
 	buffer := sha1.New()
-
-	namespace := []byte{0x48, 0x2C, 0x2D, 0xB2, 0xC3, 0x90, 0x47, 0xC8, 0x87, 0xF8, 0x1A, 0x15, 0xBF, 0xC1, 0x30, 0xFB}
-	buffer.Write(namespace)
-
+	namespace := guid.GUID{0x482C2DB2, 0xC390, 0x47C8, [8]byte{0x87, 0xF8, 0x1A, 0x15, 0xBF, 0xC1, 0x30, 0xFB}}
+	namespaceBytes := namespace.ToArray()
+	buffer.Write(namespaceBytes[:])
 	binary.Write(buffer, binary.BigEndian, utf16.Encode([]rune(strings.ToUpper(name))))
 
 	sum := buffer.Sum(nil)
 	sum[7] = (sum[7] & 0xf) | 0x50
 
-	return guid.GUID{
-		Data1: binary.LittleEndian.Uint32(sum[0:4]),
-		Data2: binary.LittleEndian.Uint16(sum[4:6]),
-		Data3: binary.LittleEndian.Uint16(sum[6:8]),
-		Data4: [8]byte{sum[8], sum[9], sum[10], sum[11], sum[12], sum[13], sum[14], sum[15]},
-	}
+	a := [16]byte{}
+	copy(a[:], sum)
+	return guid.FromWindowsArray(a)
 }
 
 // NewProvider creates and registers a new ETW provider. The provider ID is

pkg/etw/provider_test.go

@@ -0,0 +1,34 @@
+package etw
+
+import (
+	"testing"
+
+	"github.com/Microsoft/go-winio/pkg/guid"
+)
+
+func mustGUIDFromString(t *testing.T, s string) guid.GUID {
+	g, err := guid.FromString(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return g
+}
+
+func Test_ProviderIDFromName(t *testing.T) {
+	type testCase struct {
+		name string
+		g    guid.GUID
+	}
+	testCases := []testCase{
+		{"wincni", mustGUIDFromString(t, "c822b598-f4cc-5a72-7933-ce2a816d033f")},
+		{"Moby", mustGUIDFromString(t, "6996f090-c5de-5082-a81e-5841acc3a635")},
+		{"ContainerD", mustGUIDFromString(t, "2acb92c0-eb9b-571a-69cf-8f3410f383ad")},
+		{"Microsoft.Virtualization.RunHCS", mustGUIDFromString(t, "0B52781F-B24D-5685-DDF6-69830ED40EC3")},
+	}
+	for _, tc := range testCases {
+		g := providerIDFromName(tc.name)
+		if g != tc.g {
+			t.Fatalf("Incorrect provider GUID.\nExpected: %s\nActual: %s", tc.g, g)
+		}
+	}
+}