C++

Get OAuth 2.0 Access Token using G_SvcOauthAccessToken2

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server using the G_SvcOauthAccessToken2 method. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount C++

#include <CkHttp.h>
#include <CkCert.h>
#include <CkHashtable.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    //  --------------------------------------------------------------------------------
    //  For a step-by-step guide for setting up your Google Workspace service account,
    //  see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
    //  --------------------------------------------------------------------------------

    CkHttp http;

    //  When a service account (Client ID) is created at https://code.google.com/apis/console/
    //  Google will generate a P12 key.  This is a PKCS12 (PFX) file that you will download
    //  and save.  The password to access the contents of this file is "notasecret".
    //  NOTE: The Chilkat Pfx API provides the ability to load a PFX/P12 and re-save
    //  with a different password.

    //  Begin by loading the downloaded .p12 into a Chilkat certificate object:
    CkCert cert;
    success = cert.LoadPfxFile("/myDir/API Project-1c43a291e2a1-notasecret.p12","notasecret");
    if (success != true) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    //  The next (and final) step is to request the access token.  Chilkat internally
    //  does all the work of forming the JWT header and JWT claim set, encoding and
    //  signing the JWT, and sending the access token request.
    //  The application need only provide the inputs: The iss, scope(s), sub, and the
    //  desired duration with a max of 3600 seconds (1 hour).
    //  
    //  Each of these inputs is defined as follows 
    //  (see https://developers.google.com/accounts/docs/OAuth2ServiceAccount
    //  iss: The email address of the service account.
    //  scope: A space-delimited list of the permissions that the application requests.
    //  sub: The email address of the user for which the application is requesting delegated access.
    //  numSec: The number of seconds for which the access token will be valid (max 3600).

    CkHashtable claimParams;

    //  The required claim parameters that must be provided by the application are
    //  the "iss" and "scope" params:
    success = claimParams.AddStr("iss","761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com");
    success = claimParams.AddStr("scope","https://mail.google.com/");

    //  The "sub" param is required if there is an email address, such as for a
    //  Google Apps domain—if you use Google Apps for Work, where the administrator of the Google Apps domain 
    //  can authorize an application to access user data on behalf of users in the Google Apps domain.
    //  
    //  Comment out this line if there is no such email address.
    success = claimParams.AddStr("sub","user@your-domain.com");

    //  The "aud" parameter is optional.  If not set, it defaults to the value shown here:
    success = claimParams.AddStr("aud","https://accounts.google.com/o/oauth2/token");

    int numSec = 3600;

    const char *accessToken = http.g_SvcOauthAccessToken2(claimParams,numSec,cert);
    if (http.get_LastMethodSuccess() != true) {
        std::cout << http.lastErrorText() << "\r\n";
    }
    else {
        std::cout << "access token: " << accessToken << "\r\n";
    }
    }