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Authenticate with Google Cloud using service account json key and Elixir
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# https://developers.google.com/identity/protocols/OAuth2ServiceAccount | |
key_json = File.read!("some-service-account-key-file.json") | |
key_map = JOSE.decode(key_json) | |
jwk = JOSE.JWK.from_pem(key_map["private_key"]) | |
jws = %{"alg" => "RS256"} | |
header = %{ | |
"alg" => "RS256", | |
"typ" => "JWT" | |
} | |
iat = :os.system_time(:seconds) | |
exp = iat + 3600 | |
claims = %{ | |
"iss" => key_map["client_email"], | |
"scope" => "https://www.googleapis.com/auth/userinfo.email https://www.googleapis.com/auth/datastore", | |
"aud" => "https://www.googleapis.com/oauth2/v3/token", | |
"exp" => exp, | |
"iat" => iat | |
} | |
# ok we are finally going to put it altogether and sign it | |
{_, assertion} = JOSE.JWS.sign(jwk, JOSE.encode(claims), header, jws) |> JOSE.JWS.compact | |
# these come from the google auth docs, link at top | |
token_auth_uri = "https://www.googleapis.com/oauth2/v3/token" | |
headers = %{"Content-type" => "application/x-www-form-urlencoded"} | |
form = {:form, [assertion: assertion, grant_type: "urn:ietf:params:oauth:grant-type:jwt-bearer"]} | |
#IO.inspect token | |
HTTPoison.start | |
{:ok, response} = HTTPoison.post(token_auth_uri, form, headers) | |
body = JOSE.decode(response.body) | |
access_token = body["access_token"] |
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