Visual FoxPro

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. Visual FoxPro

LOCAL lnSuccess
LOCAL loSocket
LOCAL lnMaxWaitMs
LOCAL lnUseTls
LOCAL lnBigEndian
LOCAL loDt
LOCAL lnBLocalTime
LOCAL loFac
LOCAL lcJsonKey
LOCAL loGAuth
LOCAL lnUnixTime
LOCAL loTlsSock

lnSuccess = 0

* 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
loSocket = CreateObject('Chilkat.Socket')

* Connect to an NIST time server and read the current date/time
lnMaxWaitMs = 8000
lnUseTls = 0
lnSuccess = loSocket.Connect("time-c.nist.gov",37,lnUseTls,lnMaxWaitMs)
IF (lnSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

* 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
* 1 or 0 to indicate success.  If successful, the integer
* is obtained via the ReceivedInt property.
lnBigEndian = 1
lnSuccess = loSocket.ReceiveInt32(lnBigEndian)
IF (lnSuccess <> 1) THEN
    ? loSocket.LastErrorText
    RELEASE loSocket
    CANCEL
ENDIF

loDt = CreateObject('Chilkat.CkDateTime')
loDt.SetFromNtpTime(loSocket.ReceivedInt)

* Show the current local date/time
lnBLocalTime = 1
? "Current local date/time: " + loDt.GetAsRfc822(lnBLocalTime)

lnMaxWaitMs = 10
loSocket.Close(lnMaxWaitMs)

* ------------------------------------------------------------------------
* 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.
loFac = CreateObject('Chilkat.FileAccess')
lcJsonKey = loFac.ReadEntireTextFile("qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json","utf-8")
IF (loFac.LastMethodSuccess <> 1) THEN
    ? loFac.LastErrorText
    RELEASE loSocket
    RELEASE loDt
    RELEASE loFac
    CANCEL
ENDIF

* 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"
* 	}

loGAuth = CreateObject('Chilkat.AuthGoogle')
loGAuth.JsonKey = lcJsonKey

* Choose a scope.
loGAuth.Scope = "https://www.googleapis.com/auth/cloud-platform"

* Request an access token that is valid for this many seconds.
loGAuth.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.)
loGAuth.SubEmailAddress = ""

* ------------------------------------------------------------------------
* Set the IAT using the date/time from the NIST time server.
lnUnixTime = loDt.GetAsUnixTime(0)
? "unixTime = " + STR(lnUnixTime)
loGAuth.Iat = lnUnixTime

* 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.
loTlsSock = CreateObject('Chilkat.Socket')
lnSuccess = loTlsSock.Connect("www.googleapis.com",443,1,5000)
IF (lnSuccess <> 1) THEN
    ? loTlsSock.LastErrorText
    RELEASE loSocket
    RELEASE loDt
    RELEASE loFac
    RELEASE loGAuth
    RELEASE loTlsSock
    CANCEL
ENDIF

* Send the request to obtain the access token.
lnSuccess = loGAuth.ObtainAccessToken(loTlsSock)
IF (lnSuccess <> 1) THEN
    ? loGAuth.LastErrorText
    RELEASE loSocket
    RELEASE loDt
    RELEASE loFac
    RELEASE loGAuth
    RELEASE loTlsSock
    CANCEL
ENDIF

* Examine the access token:
? "Access Token: " + loGAuth.AccessToken

RELEASE loSocket
RELEASE loDt
RELEASE loFac
RELEASE loGAuth
RELEASE loTlsSock