From 0fa3331b8c7cb6b1bd4476f112cd5d77b9694301 Mon Sep 17 00:00:00 2001
From: Alex Stokes <r.alex.stokes@gmail.com>
Date: Fri, 23 Aug 2019 23:02:53 +0200
Subject: [PATCH] Add clearer indication of "self encryption"

---
 libp2p/security/secio/exceptions.py | 9 +++++++++
 libp2p/security/secio/transport.py  | 6 +++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/libp2p/security/secio/exceptions.py b/libp2p/security/secio/exceptions.py
index a5f7464..1461be9 100644
--- a/libp2p/security/secio/exceptions.py
+++ b/libp2p/security/secio/exceptions.py
@@ -2,6 +2,15 @@ class SecioException(Exception):
     pass
 
 
+class SelfEncryption(SecioException):
+    """
+    Raised to indicate that a host is attempting to encrypt communications
+    with itself.
+    """
+
+    pass
+
+
 class PeerMismatchException(SecioException):
     pass
 
diff --git a/libp2p/security/secio/transport.py b/libp2p/security/secio/transport.py
index 955c906..f77f353 100644
--- a/libp2p/security/secio/transport.py
+++ b/libp2p/security/secio/transport.py
@@ -28,6 +28,7 @@ from .exceptions import (
     InvalidSignatureOnExchange,
     PeerMismatchException,
     SecioException,
+    SelfEncryption,
 )
 from .pb.spipe_pb2 import Exchange, Propose
 
@@ -195,9 +196,8 @@ def _select_encryption_parameters(
     elif second_score < first_score:
         order = 1
 
-    # NOTE: if order is 0, "talking to self"
-    # TODO(ralexstokes) nicer error handling here...
-    assert order != 0
+    if order == 0:
+        raise SelfEncryption()
 
     return (
         _select_parameter_from_order(