Add https certificate expiry sensor (#7272)

* fixing rebase issues

* cert_expiry: added .coveragerc entry

* cert_expiry: renamed to SCAN_INTERVAL, removed Throttle

* cert_expiry: better socket exception management

* cert_expiry: splitted line too long

* Update cert_expiry.py

* Fix hass style

.coveragerc

@@ -335,6 +335,7 @@ omit =
     homeassistant/components/sensor/broadlink.py
     homeassistant/components/sensor/dublin_bus_transport.py
     homeassistant/components/sensor/coinmarketcap.py
+    homeassistant/components/sensor/cert_expiry.py
     homeassistant/components/sensor/comed_hourly_pricing.py
     homeassistant/components/sensor/cpuspeed.py
     homeassistant/components/sensor/crimereports.py

homeassistant/components/sensor/cert_expiry.py

@@ -0,0 +1,97 @@
+"""Counts the days an HTTPS (TLS) certificate will expire (days).
+
+For more details about this sensor please refer to the
+documentation at https://home-assistant.io/components/sensor.cert_expiry
+"""
+import logging
+import ssl
+import socket
+import datetime
+import voluptuous as vol
+
+import homeassistant.helpers.config_validation as cv
+from homeassistant.components.sensor import PLATFORM_SCHEMA
+from homeassistant.helpers.entity import Entity
+from homeassistant.const import (CONF_NAME, CONF_HOST, CONF_PORT)
+
+_LOGGER = logging.getLogger(__name__)
+
+DEFAULT_NAME = 'SSL Certificate Expiry'
+DEFAULT_PORT = 443
+
+SCAN_INTERVAL = datetime.timedelta(hours=12)
+TIMEOUT = 10.0
+
+PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
+    vol.Required(CONF_HOST): cv.string,
+    vol.Optional(CONF_PORT, default=DEFAULT_PORT): cv.port,
+    vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
+})
+
+
+def setup_platform(hass, config, add_devices, discovery_info=None):
+    """Setup certificate expiry sensor."""
+    server_name = config.get(CONF_HOST)
+    server_port = config.get(CONF_PORT)
+    sensor_name = config.get(CONF_NAME)
+    add_devices([SSLCertificate(sensor_name, server_name, server_port)])
+
+
+class SSLCertificate(Entity):
+    """Implements certificate expiry sensor."""
+
+    def __init__(self, sensor_name, server_name, server_port):
+        """Initialize the sensor."""
+        self.server_name = server_name
+        self.server_port = server_port
+        self._name = sensor_name
+        self._state = None
+
+    @property
+    def name(self):
+        """Return the name of the sensor."""
+        return self._name
+
+    @property
+    def unit_of_measurement(self):
+        """Return the unit this state is expressed in."""
+        return 'days'
+
+    @property
+    def state(self):
+        """Return the state of the sensor."""
+        return self._state
+
+    @property
+    def icon(self):
+        """Icon to use in the frontend, if any."""
+        return 'mdi:certificate'
+
+    def update(self):
+        """Fetch certificate information."""
+        try:
+            ctx = ssl.create_default_context()
+            sock = ctx.wrap_socket(socket.socket(),
+                                   server_hostname=self.server_name)
+            sock.settimeout(TIMEOUT)
+            sock.connect((self.server_name, self.server_port))
+        except socket.gaierror:
+            _LOGGER.error('Cannot resolve name %s', self.server_name)
+        except socket.timeout:
+            _LOGGER.error('Connection timeout with server %s',
+                          self.server_name)
+        except OSError as excp:
+            _LOGGER.error('Cannot connect to %s', self.server_name)
+            raise excp
+
+        try:
+            cert = sock.getpeercert()
+        except OSError as excp:
+            _LOGGER.error('Cannot fetch certificate from %s',
+                          (self.server_name))
+            raise excp
+
+        ts_seconds = ssl.cert_time_to_seconds(cert['notAfter'])
+        timestamp = datetime.datetime.fromtimestamp(ts_seconds)
+        expiry = timestamp - datetime.datetime.today()
+        self._state = expiry.days