Lua Requires Chilkat v10.1.2+

Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

This example show how to obtain a Gmail SMTP OAuth2 access token from a desktop application or script, enabling the use of XOAUTH2 authentication. Lua

local chilkat = require("chilkat")

-- To further clarify, see OAuth 2.0 Authorization Flow

local oauth2 = chilkat.OAuth2.new()

-- For Google OAuth2, set the listen port equal to the port used
-- in the Authorized Redirect URL for the Client ID.
-- For example, in this case the Authorized Redirect URL would be http://localhost:55568/
-- Your app should choose a port not likely not used by any other application.
oauth2.listen_port = 55568

oauth2.authorization_endpoint = "https://accounts.google.com/o/oauth2/v2/auth"
oauth2.token_endpoint = "https://www.googleapis.com/oauth2/v4/token"

-- Replace these with actual values.
oauth2.client_id = "GOOGLE-CLIENT-ID"
oauth2.client_secret = "GOOGLE-CLIENT-SECRET"

-- To use Gmail's OAuth2 for sending emails via the SMTP protocol, you need to request the https://mail.google.com/ scope.
-- See About GMail SMTP OAuth2 Scopes
oauth2.scope = "https://mail.google.com/"

-- Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
local url = oauth2:start_auth()
if not oauth2.last_method_success then
    print(oauth2.last_error_text)
    return
end

-- Launch the default browser on the system and navigate to the url.
local success = oauth2:launch_browser(url)
if not success then
    print(oauth2.last_error_text)
    return
end

-- Wait for the user to approve or deny authorization in the browser.
local numMsWaited = 0
while (numMsWaited < 90000) and (oauth2.auth_flow_state < 3) do
    oauth2:sleep_ms(100)
    numMsWaited = numMsWaited + 100
end

-- If the browser does not respond within the specified time, AuthFlowState will be:
--
-- 1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
-- 2: Waiting for Final Response – The thread is awaiting the final access token response.
-- In either case, cancel the background task initiated by StartAuth.

if oauth2.auth_flow_state < 3 then
    oauth2:cancel()
    print("No response from the browser!")
    return
end

-- Check AuthFlowState to determine if authorization was granted, denied, or failed:
--
-- 3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
-- 4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
-- 5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

if oauth2.auth_flow_state == 5 then
    print("OAuth2 failed to complete.")
    print(oauth2.failure_info)
    return
end

if oauth2.auth_flow_state == 4 then
    print("OAuth2 authorization was denied.")
    print(oauth2.access_token_response)
    return
end

if oauth2.auth_flow_state ~= 3 then
    print("Unexpected AuthFlowState:" .. oauth2.auth_flow_state)
    return
end

-- Save the full JSON access token response to a file.
local sbJson = chilkat.StringBuilder.new()
sbJson:append(oauth2.access_token_response)
sbJson:write_file("qa_data/tokens/_gmailSmtp.json", "utf-8", false)

-- The saved JSON response looks like this:

--     {
--      "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtBBBHkZzrwlARkwX6R3O0PCDEzRlfaQ",
--      "token_type": "Bearer",
--      "expires_in": 3600,
--      "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
--     }
--
print("OAuth2 authorization granted!")
print("Access Token = " .. oauth2.access_token)