在没有SDK的Google上的Actions中发送通知

Question

I am implementing notifications within an action. I am able to register users. However, I am not able to figure out how to do the push notification.

As the sample code uses the SDK, I am now stuck at the part "Exchange key for an access token" found in this documentation .

Is it possible to do this without the SDK? using a rest service?

Answer 1

Yes... but...

There is a REST service that does this, in fact, the library ultimately calls it. It is the standard OAuth2 token exchange endpoint at https://www.googleapis.com/oauth2/v4/token . The catch is building the JWT that you can pass to this service. To quote Google's page on the subject :

Although your application can complete these tasks by directly interacting with the OAuth 2.0 system using HTTP, the mechanics of server-to-server authentication interactions require applications to create and cryptographically sign JSON Web Tokens (JWTs), and it's easy to make serious errors that can have a severe impact on the security of your application.

For this reason, we strongly encourage you to use libraries, such as the Google APIs client libraries, that abstract the cryptography away from your application code.

In short, if you want to do this, you need to:

1. Create a JSON Web Token (JWT) which includes a header, a claim set, and a signature.
2. Request an access token from the Google OAuth 2.0 Authorization Server.
3. Handle the JSON response to get the access token.
4. Keep track of the lifespan of the access token and, when it expires and you need an access token, repeat steps 1-4.

Details are at Using OAuth 2.0 for Server to Server Applications

I'm not familiar with C# libraries, however I've been told that Google's C# Client Library seems to support it, and the high level documentation for ServiceAccountCredential appears to be able to generate auth tokens from the credentials.