(Unicode C) Get Firebase Access Token from JSON Service Account Private Key

Demonstrates how to get a Firebase access token using a JSON service account private key. Your Firebase service account can be used to authenticate multiple Firebase features, such as Database, Storage and Auth, programmatically.

A Firebase JSON service account private key can be created in the Firebase settings/admin portion of the console.firebase.google.com site as shown here:

Scroll down to see the example code...

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#include <C_CkFileAccessW.h>
#include <C_CkAuthGoogleW.h>
#include <C_CkSocketW.h>

void ChilkatSample(void)
    {
    HCkFileAccessW fac;
    const wchar_t *jsonKey;
    HCkAuthGoogleW gAuth;
    HCkSocketW tlsSock;
    BOOL success;

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

    // First load the Firebase JSON private key into a string.
    fac = CkFileAccessW_Create();
    jsonKey = CkFileAccessW_readEntireTextFile(fac,L"qa_data/firebase/firebase-chilkat-firebase-adminsdk-n28n4-1b664ee163.json",L"utf-8");
    if (CkFileAccessW_getLastMethodSuccess(fac) != TRUE) {
        wprintf(L"%s\n",CkFileAccessW_lastErrorText(fac));
        CkFileAccessW_Dispose(fac);
        return;
    }

    // A Firebase JSON private key should look something like this:

    // { 
    //   "type": "service_account",
    //   "project_id": "firebase-chilkat",
    //   "private_key_id": "1c664ee164907413c91ddefcf5b765ecba8779e2",
    //   "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQIBA ... Ya2UZii/lXn73/ZOK8=\n-----END PRIVATE KEY-----\n",
    //   "client_email": "firebase-adminsdk-n28n4@firebase-chilkat.iam.gserviceaccount.com",
    //   "client_id": "134846322329335418431",
    //   "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/firebase-adminsdk-n28n4%40firebase-chilkat.iam.gserviceaccount.com"
    // } 
    // 

    gAuth = CkAuthGoogleW_Create();
    CkAuthGoogleW_putJsonKey(gAuth,jsonKey);

    // Choose a scope.
    // The scope could be "https://www.googleapis.com/auth/firebase.database"
    // or a space-delimited list of scopes:
    // "https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email"

    CkAuthGoogleW_putScope(gAuth,L"https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email");

    // Request an access token that is valid for this many seconds.
    CkAuthGoogleW_putExpireNumSeconds(gAuth,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.)
    CkAuthGoogleW_putSubEmailAddress(gAuth,L"");

    // 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.
    tlsSock = CkSocketW_Create();
    success = CkSocketW_Connect(tlsSock,L"www.googleapis.com",443,TRUE,5000);
    if (success != TRUE) {
        wprintf(L"%s\n",CkSocketW_lastErrorText(tlsSock));
        CkFileAccessW_Dispose(fac);
        CkAuthGoogleW_Dispose(gAuth);
        CkSocketW_Dispose(tlsSock);
        return;
    }

    // Send the request to obtain the access token.
    success = CkAuthGoogleW_ObtainAccessToken(gAuth,tlsSock);
    if (success != TRUE) {
        wprintf(L"%s\n",CkAuthGoogleW_lastErrorText(gAuth));
        CkFileAccessW_Dispose(fac);
        CkAuthGoogleW_Dispose(gAuth);
        CkSocketW_Dispose(tlsSock);
        return;
    }

    // Examine the access token:
    wprintf(L"Firebase Access Token: %s\n",CkAuthGoogleW_accessToken(gAuth));

    // Save the token to a file (or wherever desired).  This token is valid for 1 hour.
    CkFileAccessW_WriteEntireTextFile(fac,L"qa_data/tokens/firebaseToken.txt",CkAuthGoogleW_accessToken(gAuth),L"utf-8",FALSE);


    CkFileAccessW_Dispose(fac);
    CkAuthGoogleW_Dispose(gAuth);
    CkSocketW_Dispose(tlsSock);

    }