(C++) Microsoft Graph OAuth2 Client Credentials Grant Flow

Demonstrates how to get a Microsoft Graph access token using the Client Credentials Grant Flow.

You can use the OAuth 2.0 client credentials grant specified in RFC 6749, sometimes called two-legged OAuth, to access web-hosted resources by using the identity of an application. This type of grant is commonly used for server-to-server interactions that must run in the background, without immediate interaction with a user. These types of applications are often referred to as daemons or service accounts.

For more information, see https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-client-creds-grant-flow

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#include <CkHttp.h>
#include <CkHttpRequest.h>
#include <CkHttpResponse.h>
#include <CkJsonObject.h>

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

    CkHttp http;

    CkHttpRequest req;
    req.AddParam("client_secret","CLIENT_SECRET");
    req.AddParam("client_id","CLIENT_ID");
    // Don't know if the scopes valid for the client credentials grant are different than the scopes for the 3-legged Authorization Code Grant...
    req.AddParam("scope","https://graph.microsoft.com/.default");
    req.AddParam("grant_type","client_credentials");

    // Use your own tenant ID, for example 4d8fdd66-66d1-43b0-ae5c-e31b4b7de5cd
    const char *url = "https://login.microsoftonline.com/TENANT_ID/oauth2/v2.0/token";
    CkHttpResponse *resp = http.PostUrlEncoded(url,req);
    if (http.get_LastMethodSuccess() != true) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    int statusCode = resp->get_StatusCode();
    std::cout << "Response status code = " << statusCode << "\r\n";

    CkJsonObject json;
    json.Load(resp->bodyStr());
    delete resp;

    json.put_EmitCompact(false);
    std::cout << json.emit() << "\r\n";

    // Sample successful output:

    // {
    //   "token_type": "Bearer",
    //   "expires_in": 3599,
    //   "ext_expires_in": 3599,
    //   "access_token": "eyJ0eX...K0jOERg"
    // }

    if (statusCode == 200) {
        json.WriteFile("qa_data/tokens/msGraphClientCredentialsToken.json");
        std::cout << "Success." << "\r\n";
    }
    else {
        std::cout << "Failed." << "\r\n";
    }
    }