(C++) Get Google Cloud SQL Access Token using Service Account JSON Private Key

Demonstrates how to get a Google Cloud SQL access token using a JSON service account private key. Obtaining an access token for a service account requires no user interaction (it does not require a browser, nor callback URI's, etc.).

When an access token expires, an application can be (and should be) designed to automatically fetch a new access token.

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

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

    // First load the JSON key into a string.
    CkFileAccess fac;
    const char *jsonKey = fac.readEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json","utf-8");
    if (fac.get_LastMethodSuccess() != true) {
        std::cout << fac.lastErrorText() << "\r\n";
        return;
    }

    // A JSON private key should look something 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.
    // Here's the OAuth 2.0 scope information for the Cloud SQL Admin API:
    // https://www.googleapis.com/auth/sqlservice.admin 	(Read/write access to Cloud SQL.)
    // https://www.googleapis.com/auth/cloud-platform 	(Instances.import and Instances.export need this additional scope.)
    gAuth.put_Scope("https://www.googleapis.com/auth/sqlservice.admin");

    // 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("");

    // 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";

    // Access token looks like this:  ya29.c.Ko4Bwwe3nG5rUvoBmJwadi ... Br4Ogz0B6qLAjg

    // We're going to save this access token to a file to be used
    // by other examples.
    CkStringBuilder sbToken;
    sbToken.Append(gAuth.accessToken());
    sbToken.WriteFile("qa_data/tokens/google_cloud_sql_access_token.txt","utf-8",false);
    }