Add Time-based Onetime Password Multi-factor Authentication Module (#16129)

* Add Time-based Onetime Password Multi-factor Auth

Add TOTP setup flow, generate QR code

* Resolve rebase issue

* Use svg instead png for QR code

* Lint and typing

* Fix translation

* Load totp auth module by default

* use <svg> tag instead markdown image

* Update strings

* Cleanup

homeassistant/auth/mfa_modules/totp.py

@@ -0,0 +1,212 @@
+"""Time-based One Time Password auth module."""
+import logging
+from io import BytesIO
+from typing import Any, Dict, Optional, Tuple  # noqa: F401
+
+import voluptuous as vol
+
+from homeassistant.auth.models import User
+from homeassistant.core import HomeAssistant
+
+from . import MultiFactorAuthModule, MULTI_FACTOR_AUTH_MODULES, \
+    MULTI_FACTOR_AUTH_MODULE_SCHEMA, SetupFlow
+
+REQUIREMENTS = ['pyotp==2.2.6', 'PyQRCode==1.2.1']
+
+CONFIG_SCHEMA = MULTI_FACTOR_AUTH_MODULE_SCHEMA.extend({
+}, extra=vol.PREVENT_EXTRA)
+
+STORAGE_VERSION = 1
+STORAGE_KEY = 'auth_module.totp'
+STORAGE_USERS = 'users'
+STORAGE_USER_ID = 'user_id'
+STORAGE_OTA_SECRET = 'ota_secret'
+
+INPUT_FIELD_CODE = 'code'
+
+DUMMY_SECRET = 'FPPTH34D4E3MI2HG'
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def _generate_qr_code(data: str) -> str:
+    """Generate a base64 PNG string represent QR Code image of data."""
+    import pyqrcode
+
+    qr_code = pyqrcode.create(data)
+
+    with BytesIO() as buffer:
+        qr_code.svg(file=buffer, scale=4)
+        return '{}'.format(
+            buffer.getvalue().decode("ascii").replace('\n', '')
+            .replace('<?xml version="1.0" encoding="UTF-8"?>'
+                     '<svg xmlns="http://www.w3.org/2000/svg"', '<svg')
+        )
+
+
+def _generate_secret_and_qr_code(username: str) -> Tuple[str, str, str]:
+    """Generate a secret, url, and QR code."""
+    import pyotp
+
+    ota_secret = pyotp.random_base32()
+    url = pyotp.totp.TOTP(ota_secret).provisioning_uri(
+        username, issuer_name="Home Assistant")
+    image = _generate_qr_code(url)
+    return ota_secret, url, image
+
+
+@MULTI_FACTOR_AUTH_MODULES.register('totp')
+class TotpAuthModule(MultiFactorAuthModule):
+    """Auth module validate time-based one time password."""
+
+    DEFAULT_TITLE = 'Time-based One Time Password'
+
+    def __init__(self, hass: HomeAssistant, config: Dict[str, Any]) -> None:
+        """Initialize the user data store."""
+        super().__init__(hass, config)
+        self._users = None  # type: Optional[Dict[str, str]]
+        self._user_store = hass.helpers.storage.Store(
+            STORAGE_VERSION, STORAGE_KEY)
+
+    @property
+    def input_schema(self) -> vol.Schema:
+        """Validate login flow input data."""
+        return vol.Schema({INPUT_FIELD_CODE: str})
+
+    async def _async_load(self) -> None:
+        """Load stored data."""
+        data = await self._user_store.async_load()
+
+        if data is None:
+            data = {STORAGE_USERS: {}}
+
+        self._users = data.get(STORAGE_USERS, {})
+
+    async def _async_save(self) -> None:
+        """Save data."""
+        await self._user_store.async_save({STORAGE_USERS: self._users})
+
+    def _add_ota_secret(self, user_id: str,
+                        secret: Optional[str] = None) -> str:
+        """Create a ota_secret for user."""
+        import pyotp
+
+        ota_secret = secret or pyotp.random_base32()  # type: str
+
+        self._users[user_id] = ota_secret   # type: ignore
+        return ota_secret
+
+    async def async_setup_flow(self, user_id: str) -> SetupFlow:
+        """Return a data entry flow handler for setup module.
+
+        Mfa module should extend SetupFlow
+        """
+        user = await self.hass.auth.async_get_user(user_id)   # type: ignore
+        return TotpSetupFlow(self, self.input_schema, user)
+
+    async def async_setup_user(self, user_id: str, setup_data: Any) -> str:
+        """Set up auth module for user."""
+        if self._users is None:
+            await self._async_load()
+
+        result = await self.hass.async_add_executor_job(
+            self._add_ota_secret, user_id, setup_data.get('secret'))
+
+        await self._async_save()
+        return result
+
+    async def async_depose_user(self, user_id: str) -> None:
+        """Depose auth module for user."""
+        if self._users is None:
+            await self._async_load()
+
+        if self._users.pop(user_id, None):   # type: ignore
+            await self._async_save()
+
+    async def async_is_user_setup(self, user_id: str) -> bool:
+        """Return whether user is setup."""
+        if self._users is None:
+            await self._async_load()
+
+        return user_id in self._users   # type: ignore
+
+    async def async_validation(
+            self, user_id: str, user_input: Dict[str, Any]) -> bool:
+        """Return True if validation passed."""
+        if self._users is None:
+            await self._async_load()
+
+        # user_input has been validate in caller
+        return await self.hass.async_add_executor_job(
+            self._validate_2fa, user_id, user_input[INPUT_FIELD_CODE])
+
+    def _validate_2fa(self, user_id: str, code: str) -> bool:
+        """Validate two factor authentication code."""
+        import pyotp
+
+        ota_secret = self._users.get(user_id)  # type: ignore
+        if ota_secret is None:
+            # even we cannot find user, we still do verify
+            # to make timing the same as if user was found.
+            pyotp.TOTP(DUMMY_SECRET).verify(code)
+            return False
+
+        return bool(pyotp.TOTP(ota_secret).verify(code))
+
+
+class TotpSetupFlow(SetupFlow):
+    """Handler for the setup flow."""
+
+    def __init__(self, auth_module: TotpAuthModule,
+                 setup_schema: vol.Schema,
+                 user: User) -> None:
+        """Initialize the setup flow."""
+        super().__init__(auth_module, setup_schema, user.id)
+        # to fix typing complaint
+        self._auth_module = auth_module  # type: TotpAuthModule
+        self._user = user
+        self._ota_secret = None  # type: Optional[str]
+        self._url = None  # type Optional[str]
+        self._image = None  # type Optional[str]
+
+    async def async_step_init(
+            self, user_input: Optional[Dict[str, str]] = None) \
+            -> Dict[str, Any]:
+        """Handle the first step of setup flow.
+
+        Return self.async_show_form(step_id='init') if user_input == None.
+        Return self.async_create_entry(data={'result': result}) if finish.
+        """
+        import pyotp
+
+        errors = {}  # type: Dict[str, str]
+
+        if user_input:
+            verified = await self.hass.async_add_executor_job(  # type: ignore
+                pyotp.TOTP(self._ota_secret).verify, user_input['code'])
+            if verified:
+                result = await self._auth_module.async_setup_user(
+                    self._user_id, {'secret': self._ota_secret})
+                return self.async_create_entry(
+                    title=self._auth_module.name,
+                    data={'result': result}
+                )
+
+            errors['base'] = 'invalid_code'
+
+        else:
+            hass = self._auth_module.hass
+            self._ota_secret, self._url, self._image = \
+                await hass.async_add_executor_job(  # type: ignore
+                    _generate_secret_and_qr_code, str(self._user.name))
+
+        return self.async_show_form(
+            step_id='init',
+            data_schema=self._setup_schema,
+            description_placeholders={
+                'code': self._ota_secret,
+                'url': self._url,
+                'qr_code': self._image
+            },
+            errors=errors
+        )