sphinx: add minPaddedOnionErrorLength constant

Author: joostjager

crypto.go

@@ -311,10 +311,14 @@ func onionEncrypt(sharedSecret *Hash256, data []byte) []byte {
 	return p
 }
 
-// minOnionErrorLength is the minimally expected length of the onion error
-// message. Including padding, all messages on the wire should be at least 256
-// bytes. We then add the size of the sha256 HMAC as well.
-const minOnionErrorLength = 2 + 2 + 256 + sha256.Size
+// minPaddedOnionErrorLength is the minimally expected length of the padded
+// onion error message including two uint16s for the length of the message and
+// the length of the padding.
+const minPaddedOnionErrorLength = 2 + 2 + 256
+
+// minOnionErrorLength is the minimally expected length of the complete onion
+// error message including the HMAC.
+const minOnionErrorLength = minPaddedOnionErrorLength + sha256.Size
 
 // DecryptError attempts to decrypt the passed encrypted error response. The
 // onion failure is encrypted in backward manner, starting from the node where