How to get new refresh Google OAuth token - google-oauth

Question

I've got some code (a script on a server) that tries to send an OAuth2 request to get a token from an API. I have a client id, and client secret from the "OAuth 2.0 Client Ids" section of the "Credentials" tab in the Google Cloud Platform > APIs and Services. I also have a refresh token that I originally obtained somehow.
The URL I am POSTing to is:
https://www.googleapis.com/oauth2/v4/token
I'm sending the header
Content-Type: application/x-www-form-urlencoded
In the body of my post I have the following information:
grant_type=refresh_token&client_id=${encodeURIComponent(client_id)}&client_secret=${encodeURIComponent(client_secret)}&refresh_token=${encodeURIComponent(refresh_token)}
However, it has been a long time since I last ran this code and now it returns an error "bad grant". On this page it says that a refresh token will stop working if it has not been used for six months, which explains why I am getting the error. However, it does not say how to get another refresh token using the client id and client secret similar to how I am now creating a post to get an access token. How do I do this?

Answer 1

I believe your goal and your current situation as follows.
You want to retrieve new refresh token from the current client ID and client secret.
Your client ID and client secret are the valid values.
In this case, in order to retrieve new refresh token, it is required to use the additinal 2 parameters of scope and redirect_uri. These parameters can be confirmed at your created client ID of "OAuth 2.0 Client IDs" of "Credensials" tab in the Google Cloud Platform. When the parameters including client_id, client_secret, scope and redirect_uri are used, new refresh token can be retrieved. The flow for this is as follows.
1. Retrieve authorization code.
Please create the following endpoint using client_id, redirect_uri and scope.
https://accounts.google.com/o/oauth2/auth?client_id={your client ID}&redirect_uri={your redirect uri}&scope={your scopes}&response_type=code&approval_prompt=force&access_type=offline
When you created above endpoint, please access it to your browser. By this, the login screen is opened. When you logged in to Google account, the authorization screen is opened. When you permit the scopes, the authorization code can be retrieved.
When your credential is for the web application, you can retrieve the code at the URL on the browser like http://{your redirect uri}/?code={the authorization code}&scope={your scopes}.
Please copy the code.
2. Retrieve refresh token.
Using the retrieved authorization code, you can retrieve new refresh token. The sample curl command for this is as follows.
curl \
-d "client_id={your client ID}" \
-d "client_secret={your client secret}" \
-d "redirect_uri={your redirect uri}" \
-d "grant_type=authorization_code" \
-d "code={retrieved your authorization code}" \
"https://www.googleapis.com/oauth2/v4/token"
When above curl command is run, the following result is obtained.
{
"access_token": "###",
"expires_in": 3600,
"refresh_token": "###",
"scope": "{your scopes}",
"token_type": "Bearer"
}
Reference:
Using OAuth 2.0 to Access Google APIs