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google-drive-apigoogle-oauthactions-on-google

Using Actions on Google and Google Drive together?

I'm a hobbyist student developer playing around with the Actions on Google to create a simple "text adventure" game on Google Home. Since Google Home will be speaking to the player rather than the player reading the text, I'm hoping this will create an experience similar to the "Dungeons and Dragons" roleplaying game, with the computer working as the "Dungeon Master." With the natural language assistance offered by API.AI and Actions on Google, it seemed like a good fit, since the player can respond "naturally." Here's an example of an Amazon Alexa skill that does essentially what I'm going for.

However, every time I boot up the game, it's always a new game. I'd like to store a savegame with the user's previous state in a JSON file hosted on the user's Google Drive -- Since I'm just a student doing this for fun, I don't actually have an official website or anything beyond a free Heroku server I'm running the app from, making storing saves on my end pretty much out of the question.

I've walked through the Google Drive REST quickstart for Node.js, and I've gotten that working in the console just fine. The only problem is in that quickstart, the user has to click a link to authorize the application to read the stuff in their Google Drive account, and I'm not sure how I'd be able to "click a link" and give back an access token via voice on Google Home.

Is there a way to do this via Google Drive? Or is there a better way to provide persistent data between sessions? I don't normally work in web development, so any help would be appreciated.

Solution

  • You have a few problems that you need to solve here, and while they seem related, they're not as related as you might hope:

    1. You need to get authorization to access a user's Drive space
    2. You need to authenticate the user's Home (so you know this person has come back)
    3. You have to connect the two relationships - so you know what Drive space to use for the Home device that is talking to you

    You've found the answers to (1) already, and as noted, you'll need to use a browser for them to authorize you to access their Drive. You'll then store the refresh token and will be able to access it in the future.

    But that is only part of the problem. Home does not provide you access to the user's Google account directly, so you'll have to manage your own account mechanism and tie it to Home. There are a few solutions here:

    • Home provides anonymous user identity in the JSON sent to your webhook. You can access this using getUser().user_id if you're using the Actions API library, or access this in the data.user.user_id field in the JSON. While this is similar to a browser cookie, it only stores the user ID and can't store additional data. There is also no concept of "local storage". On the plus side, this ID is consistent across devices.
    • You can request user information such as their name and address. But it doesn't have anything unique or account information, so this probably isn't useful to you.
    • You can implement an OAuth2 server and do account linking. Note that this is the other side from what you need to do with Google Drive - you'll be providing the access and refresh tokens to authenticate and authorize access to your account and the Google Home device will send these tokens back to you so you can determine who the user is. You don't actually need to store account information - you can provide token information using JSON Web Tokens (JWT) or other methods and have them store account information in a secure way. Users will use the Google Home app to actually sign-in to your service as a one-time event.

    In order to handle (3), you may be thinking that (1) lets you get tokens and the OAuth solution for (2) requires you to hand out tokens. Can the two be combined? Well... probably, but it isn't as straightforward. You can't just give the Google OAuth2 endpoints to Home - they explicitly block that and you need to control your OAuth2 endpoints. You may, however, be able to build proxy endpoints - but I haven't explored the security implications of doing so.

    I think you're on the right track - using Drive is a good place to store users' information. Using Home's account linking gives you a place where they have to come to your web site to authenticate and authorize their Home, and you can use this to do the same for their Drive.