Extract SSL context creation to helper (#15483)

* Extract SSL context creation to helper

* Lint

homeassistant/components/http/__init__.py

@@ -19,6 +19,7 @@ import homeassistant.helpers.config_validation as cv
 import homeassistant.remote as rem
 import homeassistant.util as hass_util
 from homeassistant.util.logging import HideSensitiveDataFilter
+from homeassistant.util import ssl as ssl_util
 
 from .auth import setup_auth
 from .ban import setup_bans
@@ -49,21 +50,6 @@ CONF_TRUSTED_NETWORKS = 'trusted_networks'
 CONF_LOGIN_ATTEMPTS_THRESHOLD = 'login_attempts_threshold'
 CONF_IP_BAN_ENABLED = 'ip_ban_enabled'
 
-# TLS configuration follows the best-practice guidelines specified here:
-# https://wiki.mozilla.org/Security/Server_Side_TLS
-# Modern guidelines are followed.
-SSL_VERSION = ssl.PROTOCOL_TLS  # pylint: disable=no-member
-SSL_OPTS = ssl.OP_NO_SSLv2 | ssl.OP_NO_SSLv3 | \
-           ssl.OP_NO_TLSv1 | ssl.OP_NO_TLSv1_1 | \
-           ssl.OP_CIPHER_SERVER_PREFERENCE
-if hasattr(ssl, 'OP_NO_COMPRESSION'):
-    SSL_OPTS |= ssl.OP_NO_COMPRESSION
-CIPHERS = "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:" \
-          "ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:" \
-          "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:" \
-          "ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:" \
-          "ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256"
-
 _LOGGER = logging.getLogger(__name__)
 
 DEFAULT_SERVER_HOST = '0.0.0.0'
@@ -300,9 +286,7 @@ class HomeAssistantHTTP(object):
 
         if self.ssl_certificate:
             try:
-                context = ssl.SSLContext(SSL_VERSION)
-                context.options |= SSL_OPTS
-                context.set_ciphers(CIPHERS)
+                context = ssl_util.server_context()
                 context.load_cert_chain(self.ssl_certificate, self.ssl_key)
             except OSError as error:
                 _LOGGER.error("Could not read SSL certificate from %s: %s",

homeassistant/helpers/aiohttp_client.py

@@ -1,6 +1,5 @@
 """Helper for aiohttp webclient stuff."""
 import asyncio
-import ssl
 import sys
 
 import aiohttp
@@ -8,11 +7,11 @@ from aiohttp.hdrs import USER_AGENT, CONTENT_TYPE
 from aiohttp import web
 from aiohttp.web_exceptions import HTTPGatewayTimeout, HTTPBadGateway
 import async_timeout
-import certifi
 
 from homeassistant.core import callback
 from homeassistant.const import EVENT_HOMEASSISTANT_CLOSE, __version__
 from homeassistant.loader import bind_hass
+from homeassistant.util import ssl as ssl_util
 
 DATA_CONNECTOR = 'aiohttp_connector'
 DATA_CONNECTOR_NOTVERIFY = 'aiohttp_connector_notverify'
@@ -154,9 +153,7 @@ def _async_get_connector(hass, verify_ssl=True):
         return hass.data[key]
 
     if verify_ssl:
-        ssl_context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-        ssl_context.load_verify_locations(cafile=certifi.where(),
-                                          capath=None)
+        ssl_context = ssl_util.client_context()
     else:
         ssl_context = False
 

homeassistant/util/ssl.py

@@ -0,0 +1,46 @@
+"""Helper to create SSL contexts."""
+import ssl
+
+import certifi
+
+
+def client_context():
+    """Return an SSL context for making requests."""
+    context = _get_context()
+    context.verify_mode = ssl.CERT_REQUIRED
+    context.check_hostname = True
+    context.load_verify_locations(cafile=certifi.where(), capath=None)
+    return context
+
+
+def server_context():
+    """Return an SSL context for being a server."""
+    context = _get_context()
+    context.options |= ssl.OP_CIPHER_SERVER_PREFERENCE
+    return context
+
+
+def _get_context():
+    """Return an SSL context following the Mozilla recommendations.
+
+    TLS configuration follows the best-practice guidelines specified here:
+    https://wiki.mozilla.org/Security/Server_Side_TLS
+    Modern guidelines are followed.
+    """
+    context = ssl.SSLContext(ssl.PROTOCOL_TLS)  # pylint: disable=no-member
+
+    context.options |= (
+        ssl.OP_NO_SSLv2 | ssl.OP_NO_SSLv3 |
+        ssl.OP_NO_TLSv1 | ssl.OP_NO_TLSv1_1
+    )
+    if hasattr(ssl, 'OP_NO_COMPRESSION'):
+        context.options |= ssl.OP_NO_COMPRESSION
+
+    context.set_ciphers(
+        "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:"
+        "ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:"
+        "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:"
+        "ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:"
+        "ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256"
+    )
+    return context