From 8a2821d542a13e5987eefb055d6f643dc58ea6c7 Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Sun, 9 Apr 2017 14:15:10 +0900
Subject: [PATCH] Reject invalid hostnames in Env

---
 lib/util.py     | 2 +-
 server/env.py   | 7 ++++---
 server/peers.py | 2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/util.py b/lib/util.py
index e6fdd9a..78006b9 100644
--- a/lib/util.py
+++ b/lib/util.py
@@ -249,6 +249,6 @@ def is_valid_hostname(hostname):
     if len(hostname) > 255:
         return False
     # strip exactly one dot from the right, if present
-    if hostname[-1] == ".":
+    if hostname and hostname[-1] == ".":
         hostname = hostname[:-1]
     return all(SEGMENT_REGEX.match(x) for x in hostname.split("."))
diff --git a/server/env.py b/server/env.py
index 600dc9d..c9f0b56 100644
--- a/server/env.py
+++ b/server/env.py
@@ -14,13 +14,13 @@ from ipaddress import ip_address
 from os import environ
 
 from lib.coins import Coin
-from lib.util import LoggedClass
+import lib.util as lib_util
 
 
 NetIdentity = namedtuple('NetIdentity', 'host tcp_port ssl_port nick_suffix')
 
 
-class Env(LoggedClass):
+class Env(lib_util.LoggedClass):
     '''Wraps environment configuration.'''
 
     class Error(Exception):
@@ -126,7 +126,8 @@ class Env(LoggedClass):
         try:
             ip = ip_address(host)
         except ValueError:
-            bad = host.lower().strip() in ('', 'localhost')
+            bad = (not lib_util.is_valid_hostname(host)
+                   or hostname.lower() == 'localhost')
         else:
             bad = (ip.is_multicast or ip.is_unspecified
                    or (ip.is_private and (self.irc or self.peer_announce)))
diff --git a/server/peers.py b/server/peers.py
index 9f5e651..51d6674 100644
--- a/server/peers.py
+++ b/server/peers.py
@@ -118,7 +118,7 @@ class PeerSession(JSONSession):
                 self.peer.update_features(features)
             else:
                 self.bad = True
-                self.log_warning('marking DNS alias bad')
+                self.log_warning('ignoring - not listed in features')
         self.close_if_done()
 
     def on_headers(self, result, error):