"PC/SC" sample in Objective-C (synchronous)

To continue the list of PC/SC wrappers initiated in 2010 with "PC/SC sample in different languages" I now present a new sample in Objective-C using the Apple Crypto Token Kit API.

I already proposed a sample code in Objective-C in "PCSC sample in Objective-C". This code used the asynchronous version of sendIns. The API is:

- (void)sendIns:(UInt8)ins 
             p1:(UInt8)p1 
             p2:(UInt8)p2 
           data:(NSData *)requestData 
             le:(NSNumber *)le 
          reply:(void (^)(NSData *replyData, UInt16 sw, NSError *error))reply;

The method returns immediately and a callback reply block is executed when the card response is received.

We will now use the synchronous version of sendIns. The API is:

- (NSData *)sendIns:(UInt8)ins 
                 p1:(UInt8)p1 
                 p2:(UInt8)p2 
               data:(NSData *)requestData 
                 le:(NSNumber *)le 
                 sw:(UInt16 *)sw 
              error:(NSError * _Nullable *)error;

Crypto Token Kit API

In Yosemite (Mac OS X 10.10) Apple introduced a new API to access smart cards. See OS X Yosemite and smart cards status.
This API is not a wrapper above PC/SC. It is the native API to be used on macOS. You do not need to install it, it comes with the OS.

Since PC/SC is not used here the blog title may be misleading. So I used " " around PC/SC this time.

Source code

Create a new Cocoa application in Xcode. You need to enable the App Sandbox and add/set the com.apple.security.smartcard entitlement to yes.

My sample HellloWorld application does not use Cocoa. It is a text only application.

#import <CryptoTokenKit/CryptoTokenKit.h>

int main(int argc, const char * argv[])
{
    TKSmartCardSlotManager * mngr;
    mngr = [TKSmartCardSlotManager defaultManager];

    // Use the first reader/slot found
    NSString *slotName = (NSString *)mngr.slotNames[0];
    NSLog(@"slotName: %@", slotName);

    dispatch_semaphore_t sem = dispatch_semaphore_create(0);

    // connect to the slot
    [mngr getSlotWithName:slotName reply:^(TKSmartCardSlot *slot)
     {
         // connect to the card
         TKSmartCard *card = [slot makeSmartCard];
         if (nil == card)
         {
             NSLog(@"No card found");

             // signals end of getSlotWithName block
             dispatch_semaphore_signal(sem);

             return;
         }

         // begin a session
         [card beginSessionWithReply:^(BOOL success, NSError *error)
          {
              if (success)
              {
                  NSData *response;
                  UInt16 sw;
                  NSString *newString;

                  // explicitly set the CLA byte even if 0 is already the default value
                  card.cla = 0x00;

                  // send 1st APDU
                  uint8_t aid[] = {0xA0, 0x00, 0x00, 0x00, 0x62, 0x03, 0x01, 0x0C, 0x06, 0x01};
                  NSData *data = [NSData dataWithBytes:aid length:sizeof aid];

                  response = [card sendIns:0xA4 p1:0x04 p2:0x00 data:data le:nil sw:&sw error:&error];

                  if (nil == response)
                  {
                      NSLog(@"sendIns error: %@", error);
                      goto out;
                  }

                  NSLog(@"Response: %@ 0x%04X", response, sw);

                  // send 2nd APDU
                  response = [card sendIns:0x00 p1:0x00 p2:0x00 data:nil le:@0 sw:&sw error:&error];

                  if (nil == response)
                  {
                      NSLog(@"sendIns error: %@", error);
                      goto out;
                  }

                  NSLog(@"Response: %@ 0x%04X", response, sw);

                  newString = [[NSString alloc] initWithData:response encoding:NSASCIIStringEncoding];
                  NSLog(@"%@", newString);

out:
                  // end the session
                  [card endSession];
              }
              else
              {
                  NSLog(@"Session error: %@", error);
              }

              // signals end of beginSessionWithReply block
              dispatch_semaphore_signal(sem);
          }];
     }];

    // wait for the asynchronous blocks to finish
    dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);

    return 0;
}

Output

2017-03-31 10:54:24.990581+0200 HelloWorld[19931:85555] slotName: Gemalto PC Twin Reader
2017-03-31 10:54:25.103855+0200 HelloWorld[19931:85584] Response: <> 0x9000
2017-03-31 10:54:25.115946+0200 HelloWorld[19931:85584] Response: <48656c6c 6f20776f="" 726c6421=""> 0x9000
2017-03-31 10:54:25.115993+0200 HelloWorld[19931:85584] Hello world!

Comments

Compared to the previous Objective-C sample in "PCSC sample in Objective-C" this code has some improvements/bugs fixes:

• [card endSession]; is called.
  This is needed to close the session started by [card beginSessionWithReply:...].
• The main thread is waiting for the callbacks from [mngr getSlotWithName:...] and [card beginSessionWithReply:...] to finish using a semaphore (instead of a sleep()).

The CryptoTokenKit API provides a in​Session​With​Error:​execute​Block: to synchronously begin a session instead of using begin​Session​With​Reply:​ and end​Session. But this method has some limitations/bugs and is not (yet) easy to use. I may use it in a next sample code when it will be fixed (in macOS 10.13?).

Conclusion

In general, I prefer to use synchronous calls. So the possibility to use a synchronous sendIns: method is nice.
Depending on your needs, the CryptoTokenKit TKSmart​Card API offers you the choice between a synchronous or asynchronous version.