+/// Note that we always decrypt `packet` in-place here even if the deserialization into
+/// [`msgs::DecodedOnionErrorPacket`] ultimately fails.
+fn decrypt_onion_error_packet(
+ packet: &mut Vec<u8>, shared_secret: SharedSecret
+) -> Result<msgs::DecodedOnionErrorPacket, msgs::DecodeError> {
+ let ammag = gen_ammag_from_shared_secret(shared_secret.as_ref());
+ let mut chacha = ChaCha20::new(&ammag, &[0u8; 8]);
+ chacha.process_in_place(packet);
+ msgs::DecodedOnionErrorPacket::read(&mut Cursor::new(packet))
+}
+