add tor.IsValidHostname

tor/torUtils.go

@@ -35,3 +35,17 @@ func GetTorV3Hostname(pub ed25519.PublicKey) string {
 	serviceID := base32.StdEncoding.EncodeToString(combined)
 	return strings.ToLower(serviceID)
 }
+
+// IsValidHostname returns true if the given address is a valid onion v3 address
+func IsValidHostname(address string) bool {
+	if len(address) == V3HostnameLength {
+		data, err := base32.StdEncoding.DecodeString(strings.ToUpper(address))
+		if err == nil {
+			pubkey := data[0:ed25519.PublicKeySize]
+			if GetTorV3Hostname(ed25519.PublicKey(pubkey)) == address {
+				return true
+			}
+		}
+	}
+	return false
+}