(C++) Get Google API Access Token using JSON Private Key using NIST Time Server Date/Time

Demonstrates how to get a Google API access token using a JSON service account private key, using the NIST time server date/time rather than the local system date/time.

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#include <CkSocket.h>
#include <CkDateTime.h>
#include <CkFileAccess.h>
#include <CkAuthGoogle.h>

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

    // First, let's get the current date/time from time-c.nist.gov
    CkSocket socket;

    // Connect to an NIST time server and read the current date/time
    int maxWaitMs = 8000;
    bool useTls = false;
    bool success = socket.Connect("time-c.nist.gov",37,useTls,maxWaitMs);
    if (success != true) {
        std::cout << socket.lastErrorText() << "\r\n";
        return;
    }

    // The time server will send a big-endian 32-bit integer representing
    // the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
    // The ReceiveInt32 method will receive a 4-byte integer, but returns
    // true or false to indicate success.  If successful, the integer
    // is obtained via the ReceivedInt property.
    bool bigEndian = true;
    success = socket.ReceiveInt32(bigEndian);
    if (success != true) {
        std::cout << socket.lastErrorText() << "\r\n";
        return;
    }

    CkDateTime dt;
    dt.SetFromNtpTime(socket.get_ReceivedInt());

    // Show the current local date/time
    bool bLocalTime = true;
    std::cout << "Current local date/time: " << dt.getAsRfc822(bLocalTime) << "\r\n";

    maxWaitMs = 10;
    socket.Close(maxWaitMs);

    // ------------------------------------------------------------------------
    // OK, we have the current date/time.  We'll use it to set the IAT property
    // in the code below.

    // First load the JSON key into a string.
    CkFileAccess fac;
    const char *jsonKey = fac.readEntireTextFile("qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json","utf-8");
    if (fac.get_LastMethodSuccess() != true) {
        std::cout << fac.lastErrorText() << "\r\n";
        return;
    }

    // A JSON private key should look like this:

    // 	{
    // 	  "type": "service_account",
    // 	  "project_id": "chilkattest-1350",
    // 	  "private_key_id": "fa2e36ee26986eab628b59868af8bec1d1c64c38",
    // 	  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIjFa...28N64N2n1E4FYzBZjSdy\n-----END PRIVATE KEY-----\n",
    // 	  "client_email": "598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a@developer.gserviceaccount.com",
    // 	  "client_id": "598922945226-00rb0ppfg0snd9jo7bhvd4v17jtj2d3a.apps.googleusercontent.com",
    // 	  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
    // 	  "token_uri": "https://accounts.google.com/o/oauth2/token",
    // 	  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
    // 	  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a%40developer.gserviceaccount.com"
    // 	}

    CkAuthGoogle gAuth;
    gAuth.put_JsonKey(jsonKey);

    // Choose a scope.
    gAuth.put_Scope("https://www.googleapis.com/auth/cloud-platform");

    // Request an access token that is valid for this many seconds.
    gAuth.put_ExpireNumSeconds(3600);

    // If the application is requesting delegated access:
    // The email address of the user for which the application is requesting delegated access,
    // then set the email address here. (Otherwise leave it empty.)
    gAuth.put_SubEmailAddress("");

    // ------------------------------------------------------------------------
    // Set the IAT using the date/time from the NIST time server.
    int unixTime = dt.GetAsUnixTime(false);
    std::cout << "unixTime = " << unixTime << "\r\n";
    gAuth.put_Iat(unixTime);

    // Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
    // The Chilkat socket object is used so that the connection can be established
    // through proxies or an SSH tunnel if desired.
    CkSocket tlsSock;
    bool success = tlsSock.Connect("www.googleapis.com",443,true,5000);
    if (success != true) {
        std::cout << tlsSock.lastErrorText() << "\r\n";
        return;
    }

    // Send the request to obtain the access token.
    success = gAuth.ObtainAccessToken(tlsSock);
    if (success != true) {
        std::cout << gAuth.lastErrorText() << "\r\n";
        return;
    }

    // Examine the access token:
    std::cout << "Access Token: " << gAuth.accessToken() << "\r\n";
    }