(Objective-C) Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

Note: This example requires Chilkat v10.1.2 or greater.

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <CkoOAuth2.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

// To further clarify, see OAuth 2.0 Authorization Flow

CkoOAuth2 *oauth2 = [[CkoOAuth2 alloc] init];

// 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.ListenPort = [NSNumber numberWithInt:55568];

oauth2.AuthorizationEndpoint = @"https://accounts.google.com/o/oauth2/v2/auth";
oauth2.TokenEndpoint = @"https://www.googleapis.com/oauth2/v4/token";

// Replace these with actual values.
oauth2.ClientId = @"GOOGLE-CLIENT-ID";
oauth2.ClientSecret = @"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.
NSString *url = [oauth2 StartAuth];
if (oauth2.LastMethodSuccess != YES) {
    NSLog(@"%@",oauth2.LastErrorText);
    return;
}

// Launch the default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
BOOL success = [oauth2 LaunchBrowser: url];
if (success == NO) {
    NSLog(@"%@",oauth2.LastErrorText);
    return;
}

// Wait for the user to approve or deny authorization in the browser.
int numMsWaited = 0;
while ((numMsWaited < 90000) && ([oauth2.AuthFlowState intValue] < 3)) {
    [oauth2 SleepMs: [NSNumber numberWithInt: 100]];
    numMsWaited = numMsWaited + 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.AuthFlowState intValue] < 3) {
    [oauth2 Cancel];
    NSLog(@"%@",@"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.AuthFlowState intValue] == 5) {
    NSLog(@"%@",@"OAuth2 failed to complete.");
    NSLog(@"%@",oauth2.FailureInfo);
    return;
}

if ([oauth2.AuthFlowState intValue] == 4) {
    NSLog(@"%@",@"OAuth2 authorization was denied.");
    NSLog(@"%@",oauth2.AccessTokenResponse);
    return;
}

if ([oauth2.AuthFlowState intValue] != 3) {
    NSLog(@"%@%d",@"Unexpected AuthFlowState:",[oauth2.AuthFlowState intValue]);
    return;
}

// Save the full JSON access token response to a file.
CkoStringBuilder *sbJson = [[CkoStringBuilder alloc] init];
[sbJson Append: oauth2.AccessTokenResponse];
[sbJson WriteFile: @"qa_data/tokens/_gmailSmtp.json" charset: @"utf-8" emitBom: NO];

// 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"
// 	}
// 
NSLog(@"%@",@"OAuth2 authorization granted!");
NSLog(@"%@%@",@"Access Token = ",oauth2.AccessToken);