Rust

Get GMail IMAP OAuth2 Access Token for Desktop App

See more GMail SMTP/IMAP/POP Examples

Demonstrates how to get a GMail IMAP OAuth2 access token from a desktop application or script, which can be used with the XOAUTH2 authentication method.

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. You'll need to find out how to display a web browser and navigate to the URL returned by the call to oauth2.StartAuth.

Rust

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

let 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:3017/
// Your app should choose a port not likely not used by any other application.
oauth2.set_listen_port(3017);

oauth2.set_authorization_endpoint("https://accounts.google.com/o/oauth2/v2/auth");
oauth2.set_token_endpoint("https://www.googleapis.com/oauth2/v4/token");

// Replace these with actual values.
oauth2.set_client_id("GOOGLE-CLIENT-ID");
oauth2.set_client_secret("GOOGLE-CLIENT-SECRET");

oauth2.set_code_challenge(true);
oauth2.set_code_challenge_method("S256");

// This is the full-permissions scope for GMail, which would allow full IMAP read/write access.
oauth2.set_scope("https://mail.google.com/");

// Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
let Ok(url) = oauth2.start_auth() else {
    println!("{}", oauth2.last_error_text());
    return;
};

// Launch the system's default browser navigated to the URL.
if oauth2.launch_browser(&url).is_err() {
    println!("{}", oauth2.last_error_text());
    return;
}

// Now wait for the authorization.
// We'll wait for a max of 30 seconds.
let mut num_ms_waited = 0;
while (num_ms_waited < 30000) && (oauth2.auth_flow_state() < 3) {
    oauth2.sleep_ms(100);
    num_ms_waited = num_ms_waited + 100;
}

// 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 {
    let _ = oauth2.cancel();
    println!("No response from the browser!");
    return;
}

// 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 {
    println!("OAuth2 failed to complete.");
    println!("{}", oauth2.failure_info());
    return;
}

if oauth2.auth_flow_state() == 4 {
    println!("OAuth2 authorization was denied.");
    println!("{}", oauth2.access_token_response());
    return;
}

if oauth2.auth_flow_state() != 3 {
    println!("Unexpected AuthFlowState:{}", oauth2.auth_flow_state());
    return;
}

// Save the full JSON access token response to a file.
let sb_json = chilkat::StringBuilder::new();
let _ = sb_json.append(&oauth2.access_token_response());
let _ = sb_json.write_file("qa_data/tokens/_gmailFullAccess.json", "utf-8", false);

// The saved JSON response looks like this:

// 	{
// 	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtABCHkZzrwlARkwX6R3O0PCDEzRlfaQ",
// 	 "token_type": "Bearer",
// 	 "expires_in": 3600,
// 	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
// 	}
// 
println!("OAuth2 authorization granted!");
println!("Access Token: {}", oauth2.access_token());