Objective-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. Objective-C

#import <CkoSocket.h>
#import <CkoDateTime.h>
#import <CkoFileAccess.h>
#import <NSString.h>
#import <CkoAuthGoogle.h>

BOOL success = NO;

//  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
CkoSocket *socket = [[CkoSocket alloc] init];

//  Connect to an NIST time server and read the current date/time
int maxWaitMs = 8000;
BOOL useTls = NO;
success = [socket Connect: @"time-c.nist.gov" port: [NSNumber numberWithInt: 37] ssl: useTls maxWaitMs: [NSNumber numberWithInt: maxWaitMs]];
if (success != YES) {
    NSLog(@"%@",socket.LastErrorText);
    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 = YES;
success = [socket ReceiveInt32: bigEndian];
if (success != YES) {
    NSLog(@"%@",socket.LastErrorText);
    return;
}

CkoDateTime *dt = [[CkoDateTime alloc] init];
[dt SetFromNtpTime: socket.ReceivedInt];

//  Show the current local date/time
BOOL bLocalTime = YES;
NSLog(@"%@%@",@"Current local date/time: ",[dt GetAsRfc822: bLocalTime]);

maxWaitMs = 10;
[socket Close: [NSNumber numberWithInt: 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.
CkoFileAccess *fac = [[CkoFileAccess alloc] init];
NSString *jsonKey = [fac ReadEntireTextFile: @"qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json" charset: @"utf-8"];
if (fac.LastMethodSuccess != YES) {
    NSLog(@"%@",fac.LastErrorText);
    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"
//  	}

CkoAuthGoogle *gAuth = [[CkoAuthGoogle alloc] init];
gAuth.JsonKey = jsonKey;

//  Choose a scope.
gAuth.Scope = @"https://www.googleapis.com/auth/cloud-platform";

//  Request an access token that is valid for this many seconds.
gAuth.ExpireNumSeconds = [NSNumber numberWithInt: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.SubEmailAddress = @"";

//  ------------------------------------------------------------------------
//  Set the IAT using the date/time from the NIST time server.
int unixTime = [dt GetAsUnixTime: NO];
NSLog(@"%@%d",@"unixTime = ",unixTime);
gAuth.Iat = [NSNumber numberWithInt: 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.
CkoSocket *tlsSock = [[CkoSocket alloc] init];
success = [tlsSock Connect: @"www.googleapis.com" port: [NSNumber numberWithInt: 443] ssl: YES maxWaitMs: [NSNumber numberWithInt: 5000]];
if (success != YES) {
    NSLog(@"%@",tlsSock.LastErrorText);
    return;
}

//  Send the request to obtain the access token.
success = [gAuth ObtainAccessToken: tlsSock];
if (success != YES) {
    NSLog(@"%@",gAuth.LastErrorText);
    return;
}

//  Examine the access token:
NSLog(@"%@%@",@"Access Token: ",gAuth.AccessToken);