How to get Google OAuth 2.0 Access token directly using curl? (without using Google Libraries)

Question

I'm trying to follow this tutorial to authenticate with Google using their OAuth 2.0 API. However, I would like to make straight curl calls rather than use their libraries.

I have obtained my Client ID and Client Secret Key. Now I'm trying to get the access token like this:

curl \
--request POST \
--header "Content-Type: application/json" \
--data '{
  "client_id":"MY_CLIENT_ID",
  "client_secret":"MY_SECRET_KEY",
  "redirect_uri": "http://localhost/etc",
  "grant_type":"authorization_code"
}' \
"https://accounts.google.com/o/oauth2/token"

However, it is not working. It gives me the following error:

{
  "error" : "invalid_request",
  "error_description" : "Required parameter is missing: grant_type"
}

Can someone please provide me sample curl call to obtain the access token (and refresh token)?

Take a look at: stackoverflow.com/a/18260206/1503886

Jay Lee
– Jay Lee

2016-05-09 12:02:34 +00:00
Commented May 9, 2016 at 12:02 — Jay Lee
– Jay Lee, Commented May 9, 2016 at 12:02

Hans Z. · Accepted Answer · 2019-03-24 19:42:04Z

18

a) the data you provide should be form-encoded instead of presented as a JSON object and b) you should also provide an authorization code value in the "code" parameter. E.g.:

curl -d "client_id=MY_CLIENT_ID&\
  client_secret=MY_SECRET_KEY&\
  redirect_uri=http://localhost/etc&\
  grant_type=authorization_code&\
  code=CODE" https://oauth2.googleapis.com/token

edited Mar 24, 2019 at 19:42

answered May 9, 2016 at 9:23

Hans Z.

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5 Comments

Saqib Ali Over a year ago

Is this a get or a post?

Hans Z. Over a year ago

Using -d automatically turns it in to a POST and sets the desired content type

Wheezil Over a year ago

Can this technique be extended to cover two-legged OAuth2?

Tad Over a year ago

The code parameter comes from the original auth request: developers.google.com/android-publisher/authorization

Michael IV Over a year ago

what is "code"? Where do I get it from?

Tad · Accepted Answer · 2019-11-07 13:02:07Z

9

While not directly using CURL, you can also get and test OAuth tokens using the Google OAuth Playground: https://developers.google.com/oauthplayground/

answered Nov 7, 2019 at 13:02

Tad

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Comments

Isha Firani · Accepted Answer · 2023-10-16 10:22:53Z

create and execute a python script file to obtain JWT assertion key which will be further used in curl command :

python script for generating jwt assertion key :
import jwt
import os
import json
import sys

# Load the service account key JSON
service_account_key = json.loads(open("name of your service account key file").read())

# Extract necessary information from the service account key JSON
client_email = service_account_key["client_email"]



# Create the payload with necessary claims
payload = {
    "iss": client_email,
    "sub": client_email,
    "aud": "https://oauth2.googleapis.com/token",
    "exp": expired timestamp,  # Replace with the expiration timestamp
    "iat": current timestamp,  # Replace with the issuance timestamp
    "scope": "https://www.googleapis.com/auth/cloud-platform"
}

# Sign the payload with the service account's private key
#with open(os.path.join(sys.path[0], 'privatekey.pem'), "r") as private_key_file:
#    private_key = private_key_file.read()

private_key = "mention your private key present in service account key file"

jwt_assertion = jwt.encode(payload, private_key, algorithm="RS256")


print(jwt_assertion)


______________________________________________________________________

assertion key will be obtained after executing the above python script , paste that in below curl command ,

Now, curl -X POST "https://oauth2.googleapis.com/token" \
     -d "scope=read&grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer" \
     -d "assertion=(your jwt_assertion key)"

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