helper/resource: ok let's actually use RFC4122

helper/resource/id.go

@@ -12,14 +12,30 @@ const UniqueIdPrefix = `terraform-`
 // Helper for a resource to generate a unique identifier
 //
 // This uses a simple RFC 4122 v4 UUID with some basic cosmetic filters
-// applied (remove padding, downcase) to help distinguishing visually between
-// identifiers.
+// applied (base32, remove padding, downcase) to make visually distinguishing
+// identifiers easier.
 func UniqueId() string {
-	var uuid [16]byte
-	rand.Read(uuid[:])
 	return fmt.Sprintf("%s%s", UniqueIdPrefix,
 		strings.ToLower(
 			strings.Replace(
-				base32.StdEncoding.EncodeToString(uuid[:]),
+				base32.StdEncoding.EncodeToString(uuidV4()),
 				"=", "", -1)))
 }
+
+func uuidV4() []byte {
+	var uuid [16]byte
+
+	// Set all the other bits to randomly (or pseudo-randomly) chosen
+	// values.
+	rand.Read(uuid[:])
+
+	// Set the two most significant bits (bits 6 and 7) of the
+	// clock_seq_hi_and_reserved to zero and one, respectively.
+	uuid[8] = (uuid[8] | 0x80) & 0x8f
+
+	// Set the four most significant bits (bits 12 through 15) of the
+	// time_hi_and_version field to the 4-bit version number from Section 4.1.3.
+	uuid[6] = (uuid[6] | 0x40) & 0x4f
+
+	return uuid[:]
+}