Lua

Get POP3 GMail OAuth2 Access Token for Desktop App

See more GMail SMTP/IMAP/POP Examples

Demonstrates how to get a POP3 GMail OAuth2 access token from a desktop application or script.

This example requires a browser window to be displayed to allow the GMail account owner to authorize the access. The code for displaying the web browser is omitted. Suggestions for a few programming languages are provided in code comments. To complete this example, you will need to find out how to display a web browser and navigate to the URL returned by the call to oauth2.StartAuth.

Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

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"

oauth2.code_challenge = true
oauth2.code_challenge_method = "S256"

-- See https://developers.google.com/gmail/api/auth/scopes for a list of GMail scopes.
-- This is the full-permissions scope for GMail, which is sufficient for all POP3 operations to pop.gmail.com
oauth2.scope = "https://mail.google.com/"

-- Important note about GMail scope for sending email:
-- If the SMTP protocol is used for sending, then the full GMail scope is required: "https://mail.google.com/"
-- Here is an example that sends GMail via the SMTP protocol:  Send GMail using SMTP
-- If the GMail REST API is used, then the more restrictive Gmail scope can be used:  "https://www.googleapis.com/auth/gmail.send"
-- Here is an example that sends GMail using the GMail REST API: Send GMail using REST API

-- Begin the OAuth2 three-legged 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 system's default browser navigated to the URL.
local success = oauth2:launch_browser(url)
if not success then
    print(oauth2.last_error_text)
    return
end

-- Now wait for the authorization.
-- We'll wait for a max of 30 seconds.
local numMsWaited = 0
while (numMsWaited < 30000) and (oauth2.auth_flow_state < 3) do
    oauth2:sleep_ms(100)
    numMsWaited = numMsWaited + 100
end

-- If there was no response from the browser within 30 seconds, then
-- the AuthFlowState will be equal to 1 or 2.
-- 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
-- 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
-- In that case, cancel the background task started in the call to StartAuth.
if oauth2.auth_flow_state < 3 then
    oauth2:cancel()
    print("No response from the browser!")
    return
end

-- Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
-- The possible AuthFlowState values are:
-- 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
-- 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
-- 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
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/gmail_pop3.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)