Rust 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. Rust

// To further clarify, see OAuth 2.0 Authorization Flow

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:55568/
// Your app should choose a port not likely not used by any other application.
oauth2.set_listen_port(55568);

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");

// 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.set_scope("https://mail.google.com/");

// Begin the OAuth2 Authorization code 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 default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
if oauth2.launch_browser(&url).is_err() {
    println!("{}", oauth2.last_error_text());
    return;
}

// Wait for the user to approve or deny authorization in the browser.
let mut num_ms_waited = 0;
while (num_ms_waited < 90000) && (oauth2.auth_flow_state() < 3) {
    oauth2.sleep_ms(100);
    num_ms_waited = num_ms_waited + 100;
}

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

// 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 {
    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/_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"
// 	}
// 
println!("OAuth2 authorization granted!");
println!("Access Token = {}", oauth2.access_token());