(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

Chilkat C/C++ Library Downloads
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#include <C_CkHttp.h>
#include <C_CkHttpRequest.h>
#include <C_CkHttpResponse.h>
#include <C_CkJsonObject.h>

void ChilkatSample(void)
    {
    HCkHttp http;
    HCkHttpRequest req;
    const char *url;
    HCkHttpResponse resp;
    int statusCode;
    HCkJsonObject json;

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

    http = CkHttp_Create();

    req = CkHttpRequest_Create();
    CkHttpRequest_AddParam(req,"client_secret","CLIENT_SECRET");
    CkHttpRequest_AddParam(req,"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...
    CkHttpRequest_AddParam(req,"scope","https://graph.microsoft.com/.default");
    CkHttpRequest_AddParam(req,"grant_type","client_credentials");

    // Use your own tenant ID, for example 4d8fdd66-66d1-43b0-ae5c-e31b4b7de5cd
    url = "https://login.microsoftonline.com/TENANT_ID/oauth2/v2.0/token";
    resp = CkHttp_PostUrlEncoded(http,url,req);
    if (CkHttp_getLastMethodSuccess(http) != TRUE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkHttp_Dispose(http);
        CkHttpRequest_Dispose(req);
        return;
    }

    statusCode = CkHttpResponse_getStatusCode(resp);
    printf("Response status code = %d\n",statusCode);

    json = CkJsonObject_Create();
    CkJsonObject_Load(json,CkHttpResponse_bodyStr(resp));
    CkHttpResponse_Dispose(resp);

    CkJsonObject_putEmitCompact(json,FALSE);
    printf("%s\n",CkJsonObject_emit(json));

    // Sample successful output:

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

    if (statusCode == 200) {
        CkJsonObject_WriteFile(json,"qa_data/tokens/msGraphClientCredentialsToken.json");
        printf("Success.\n");
    }
    else {
        printf("Failed.\n");
    }



    CkHttp_Dispose(http);
    CkHttpRequest_Dispose(req);
    CkJsonObject_Dispose(json);

    }