Add ssh public key support to the asuswrt component (#2287)

The pexpect.pxssh module has support for using public key
authentication. [1] This commit adds support for leveraging that and
establishing a ssh connection with a public key instead of a password.

[1] http://pexpect.readthedocs.io/en/stable/api/pxssh.html#pexpect.pxssh.pxssh.login

homeassistant/components/device_tracker/asuswrt.py

@@ -56,9 +56,13 @@ _IP_NEIGH_REGEX = re.compile(
 def get_scanner(hass, config):
     """Validate the configuration and return an ASUS-WRT scanner."""
     if not validate_config(config,
-                           {DOMAIN: [CONF_HOST, CONF_USERNAME, CONF_PASSWORD]},
+                           {DOMAIN: [CONF_HOST, CONF_USERNAME]},
                            _LOGGER):
         return None
+    elif CONF_PASSWORD not in config[DOMAIN] and \
+            'pub_key' not in config[DOMAIN]:
+        _LOGGER.error("Either a public key or password must be provided")
+        return None
 
     scanner = AsusWrtDeviceScanner(config[DOMAIN])
 
@@ -75,7 +79,8 @@ class AsusWrtDeviceScanner(object):
         """Initialize the scanner."""
         self.host = config[CONF_HOST]
         self.username = str(config[CONF_USERNAME])
-        self.password = str(config[CONF_PASSWORD])
+        self.password = str(config.get(CONF_PASSWORD))
+        self.pub_key = str(config.get('pub_key'))
         self.protocol = config.get('protocol')
         self.mode = config.get('mode')
 
@@ -126,9 +131,16 @@ class AsusWrtDeviceScanner(object):
     def ssh_connection(self):
         """Retrieve data from ASUSWRT via the ssh protocol."""
         from pexpect import pxssh
+
         try:
             ssh = pxssh.pxssh()
-            ssh.login(self.host, self.username, self.password)
+            if self.pub_key:
+                ssh.login(self.host, self.username, ssh_key=self.pub_key)
+            elif self.password:
+                ssh.login(self.host, self.username, self.password)
+            else:
+                _LOGGER.error('No password or public key specified')
+                return('', '', '')
             ssh.sendline(_IP_NEIGH_CMD)
             ssh.prompt()
             neighbors = ssh.before.split(b'\n')[1:-1]

tests/components/device_tracker/test_asuswrt.py

@@ -0,0 +1,69 @@
+"""The tests for the ASUSWRT device tracker platform."""
+
+import os
+import unittest
+from unittest import mock
+
+from homeassistant.components import device_tracker
+from homeassistant.const import (CONF_PLATFORM, CONF_PASSWORD, CONF_USERNAME,
+                                 CONF_HOST)
+
+from tests.common import get_test_home_assistant
+
+
+class TestComponentsDeviceTrackerASUSWRT(unittest.TestCase):
+    """Tests for the ASUSWRT device tracker platform."""
+
+    def setUp(self):  # pylint: disable=invalid-name
+        """Setup things to be run when tests are started."""
+        self.hass = get_test_home_assistant()
+
+    def tearDown(self):  # pylint: disable=invalid-name
+        """Stop everything that was started."""
+        try:
+            os.remove(self.hass.config.path(device_tracker.YAML_DEVICES))
+        except FileNotFoundError:
+            pass
+
+    def test_password_or_pub_key_required(self):
+        """Test creating an AsusWRT scanner without a pass or pubkey."""
+        self.assertIsNone(device_tracker.asuswrt.get_scanner(
+            self.hass, {device_tracker.DOMAIN: {
+                CONF_PLATFORM: 'asuswrt',
+                CONF_HOST: 'fake_host',
+                CONF_USERNAME: 'fake_user'
+            }}))
+
+    @mock.patch(
+        'homeassistant.components.device_tracker.asuswrt.AsusWrtDeviceScanner',
+        return_value=mock.MagicMock())
+    def test_get_scanner_with_password_no_pubkey(self, asuswrt_mock):
+        """Test creating an AsusWRT scanner with a password and no pubkey."""
+        conf_dict = {
+            device_tracker.DOMAIN: {
+                CONF_PLATFORM: 'asuswrt',
+                CONF_HOST: 'fake_host',
+                CONF_USERNAME: 'fake_user',
+                CONF_PASSWORD: 'fake_pass'
+            }
+        }
+        self.assertIsNotNone(device_tracker.asuswrt.get_scanner(
+            self.hass, conf_dict))
+        asuswrt_mock.assert_called_once_with(conf_dict[device_tracker.DOMAIN])
+
+    @mock.patch(
+        'homeassistant.components.device_tracker.asuswrt.AsusWrtDeviceScanner',
+        return_value=mock.MagicMock())
+    def test_get_scanner_with_pubkey_no_password(self, asuswrt_mock):
+        """Test creating an AsusWRT scanner with a pubkey and no password."""
+        conf_dict = {
+            device_tracker.DOMAIN: {
+                CONF_PLATFORM: 'asuswrt',
+                CONF_HOST: 'fake_host',
+                CONF_USERNAME: 'fake_user',
+                'pub_key': '/fake_path'
+            }
+        }
+        self.assertIsNotNone(device_tracker.asuswrt.get_scanner(
+            self.hass, conf_dict))
+        asuswrt_mock.assert_called_once_with(conf_dict[device_tracker.DOMAIN])