Google Smart home report state error 403 - google-api

Question

I'm reporting states for devices using http post with a jwt generated using service account. Below is the payload for jwt
{
"iss": "<service-account-email>",
"scope": "https://www.googleapis.com/auth/homegraph",
"aud": "https://accounts.google.com/o/oauth2/token",
"iat": <current-time>,
"exp": <current-time-plus-one-hour>
}
after this I sign the jwt using the private key for my service account using the python library google.auth.crypt.RSASigner.from_service_account_file(path)
and generate the jwt token. I am further using this token to obtain the access token from https://accounts.google.com/o/oauth/token, which is also successful.
After obtaining the access token I am making a post request to
https://homegraph.googleapis.com/v1/devices:reportStateAndNotification?key=api_key
with headers
{"Authorization": "Bearer <token>", "X-GFE-SSL": "yes", "Content-Type": "application/json"}
and json data
{ "requestId": "ff36a3cc-ec34-11e6-b1a0-64510650abcf", "agent_user_id": "1234", "payload": { "devices": { "states": { "1458765": { "on": true }, "4578964": { "on": true, "isLocked": true } } } } }
But this gives me
{'error': {'code': 403, 'message': 'The request is missing a valid API key.', 'status': 'PERMISSION_DENIED'}}
I followed the steps from
https://developers.google.com/actions/smarthome/report-state
is there anything i'm doing wrong? or am I missing any steps?
UPDATE:
I added the api key to the uri now it gives me another error in response
{'error': {'code': 403, 'message': 'The caller does not have permission', 'status': 'PERMISSION_DENIED'}}
how do I resolve this issue?

Answer 1

In order to report the state to the Home Graph you have to:
Create a Service Account for the token creation from your SmartHomeApp project:
Go to APIs & Services => Click on Credentials
Click on Create credentials => Click on Service account key
Fill with your data creating a new New service account => Select the role Service Accounts > Service Account Token Creator
Download the JSON file with your keys and certificate
Get a valid signed JWT token:
credentials = service_account.Credentials.from_service_account_file(service_account_file, scopes="https://www.googleapis.com/auth/homegraph")
now = int(time.time())
expires = now + 3600 # One hour in seconds
payload = {
'iat': now,
'exp': expires,
'aud': "https://accounts.google.com/o/oauth2/token",
'scope': SCOPE,
'iss': credentials.service_account_email
}
signed_jwt = google.auth.jwt.encode(credentials.signer, payload)
Obtain a valid Access token:
headers = {"Authorization": "Bearer {}".format(signed_jwt.decode("utf-8")), "Content-Type": "application/x-www-form-urlencoded"}
data = {"grant_type": "urn:ietf:params:oauth:grant-type:jwt-bearer", "assertion": signed_jwt}
access_token = requests.post("https://accounts.google.com/o/oauth2/token", data=data, headers=headers).get("access_token")
Send the reported states:
headers = {"Authorization": "Bearer {}".format(access_token), "X-GFE-SSL": "yes"}
data = {"requestId": request_id, "agent_user_id": agent_user_id, "payload": {"devices": {"states": states}}}
requests.post("https://homegraph.googleapis.com/v1/devices:reportStateAndNotification", data=json.dumps(data), headers=headers)
NOTE: in order to work these snippets require to import google.auth.jwt, from google.oauth2 import service_accountand import requests from google-auth, google-auth-httplib2 and requests packages.