Using SCardControl under Linux and from a Java program

SCardControl is the PC/SC function that makes it possible for the application to invoke ‘proprietary’ functions, implemented either in the PC/SC reader itself (CSB6, Prox’N’Roll PC/SC, EasyFinger or CrazyWriter) , or in its driver running on the PC, or in the PC/SC middleware.

The prototype is:

LONG SCardControl(
  SCARDHANDLE hCard,
  DWORD dwControlCode,
  LPCVOID lpInBuffer,
  DWORD nInBufferSize,
  LPVOID lpOutBuffer,
  DWORD nOutBufferSize,
  LPDWORD lpBytesReturned
);

(see http://pcsclite.alioth.debian.org/api/group__API.html for the PCSC-Lite documentation, and http://msdn.microsoft.com/en-us/library/windows/desktop/aa379474%28v=vs.85%29.aspx for Microsoft’s version).

The lpInbuffer / nInBufferSize parameters hold the command buffer that will be processed by either target -reader, driver, or PC/SC middleware-.

SpringCard PC/SC Readers do provide a few ‘proprietary’ functions (called ‘Escape commands’ in the USB CCID specification). For instance, an application would send the command 58 1E 01 00 to switch the reader’s red LED ON. A question remains: what must the value of dwControlCode be, when the application wants to send the command right to the reader, bypassing both the PC/SC middleware and the driver? The answer varies with the operating system, which doesn’t help implementing portable code.

Differences between Windows and PCSC-Lite implementations

Windows

In Microsoft’s CCID driver (http://msdn.microsoft.com/en-us/library/windows/hardware/gg487509.aspx), the dwControlCode for the Escape command is defined as follows:

#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(3500)

SpringCard PC/SC Readers follow the CCID specification. SpringCard’s CCID driver (SDD480) uses the same dwControlCode as Microsoft’s.

Therefore, on Windows, the application would switch the red LED on this way:

#include <windows.h>
#include <winscard.h>

#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(3500)

(...)

const BYTE SET_RED_LED_ON[4] = { 0x58, 0x1E, 0x01, 0x00 };

SCARDCONTEXT hContext;
SCARDHANDLE hCard;
DWORD dwProtocol;
BYTE abResponse[256];
DWORD dwRespLen;
LONG rc;

(...)

/* Instanciate the winscard.dll library */
rc = SCardEstablishContext(SCARD_SCOPE_SYSTEM, NULL, NULL, &amp;hContext);
if (rc != SCARD_S_SUCCESS) { /* TODO: handle error */ }

/* Get a direct connection to the reader (we don't need a card to send Escape commands) */
rc = SCardConnect(hContext, szReader, SCARD_SHARE_DIRECT, 0, &amp;hCard, &amp;dwProtocol);
if (rc != SCARD_S_SUCCESS) { /* TODO: handle error */ }

/* Send the command */
rc = SCardControl(hCard, IOCTL_CCID_ESCAPE, SET_RED_LED_ON, sizeof(SET_RED_LED_ON), abResponse, sizeof(abResponse), &amp;dwRespLen);
if (rc != SCARD_S_SUCCESS) { /* TODO: handle error */ }

SCardDisconnect(hCard, SCARD_LEAVE_CARD);
SCardReleaseContext(hContext);

Important notes:

Working with MS’ CCID driver

With Microsoft’s CCID driver, the Escape feature is disabled by default.

In order to send or receive an Escape command to a reader, the DWORD registry value EscapeCommandEnable must be added and set to a non-zero value under one of the following keys.

HKLM\SYSTEM\CCS\Enum\USB\Vid*Pid*\*\Device Parameters (prior to Windows 7).

HKLM\SYSTEM\CCS\Enum\USB\Vid*Pid*\*\Device Parameters\WUDFUsbccidDriver (Windows 7 and later).

This is clearly explained in the Developer’s Manual for every PC/SC reader.

Using SpringCard’s SDD480 CCID driver shall be preferred.

Early versions of SDD480

Branch -Ax of SpringCard’s SDD480 CCID driver uses a different value for the dwControlCode parameter.

#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(2048)

Switching to the latest version of SpringCard’s SDD480 CCID driver (branch -Bx and onwards) shall be preferred.

Linux, MacOS and other Unix*

In Ludovic Rousseau’s open-source CCID driver (http://pcsclite.alioth.debian.org/ccid.html), the dwControlCode for the Escape command is defined as follows:

#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(1)

(See http://anonscm.debian.org/viewvc/pcsclite/trunk/Drivers/ccid/SCARDCONTOL.txt?view=markup for details)

Therefore, when working with PCSC-Lite, the application would switch the red LED on this way:

#ifdef __APPLE__
#include <pcsc/winscard.h>
#include <pcsc/wintypes.h>
#else
#include <winscard.h>
#endif

#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(1)

(...)

const BYTE SET_RED_LED_ON[4] = { 0x58, 0x1E, 0x01, 0x00 };

SCARDCONTEXT hContext;
SCARDHANDLE hCard;
DWORD dwProtocol;
BYTE abResponse[256];
DWORD dwRespLen;
LONG rc;

(...)

/* Instanciate the winscard.dll library */
rc = SCardEstablishContext(SCARD_SCOPE_SYSTEM, NULL, NULL, &hContext);
if (rc != SCARD_S_SUCCESS) { /* TODO: handle error */ }

/* Get a direct connection to the reader (we don't need a card to send Escape commands) */
rc = SCardConnect(hContext, szReader, SCARD_SHARE_DIRECT, 0, &hCard, &dwProtocol);
if (rc != SCARD_S_SUCCESS) { /* TODO: handle error */ }

/* Send the command */
rc = SCardControl(hCard, IOCTL_CCID_ESCAPE, SET_RED_LED_ON, sizeof(SET_RED_LED_ON), abResponse, sizeof(abResponse), &dwRespLen);
if (rc != SCARD_S_SUCCESS) { /* TODO: handle error */ }

SCardDisconnect(hCard, SCARD_LEAVE_CARD);
SCardReleaseContext(hContext);

Enabling the Escape commands

With this CCID driver, the Escape feature is also disabled by default.

You’ll have to edit the CCID driver’s Info.plist file to enable this feature:

Open /usr/local/lib/pcsc/drivers/ccid/Info.plist in edit mode with root priviledge,
Locate the line <key>ifdDriverOptions</key>,
The following line is typically <string>0000</string>,
Define the new value: <string>0001</string>,
Save the file and restard pcscd.

(More details on http://ludovicrousseau.blogspot.fr/2011/10/featureccidesccommand.html)

Writing portable code

The idea is only to use a #ifdef to compile the correct value:

#ifdef WIN32
#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(3500)
#else
#define IOCTL_CCID_ESCAPE SCARD_CTL_CODE(1)
#endif

Java

The javax.smartcardio API provides Java methods that are stricly bound to the underlying PC/SC subsystem. The Card.transmitControlCommand method is the wrapper for SCardControl. The prototype is coherent:

public abstract byte[] transmitControlCommand(
  int controlCode,
  byte[] command)
    throws CardException

Now the same question: what must the value of controlCode be? The answer is short: it depends on the PC/SC stack! SCARD_CTL_CODE(3500) for Windows, and SCARD_CTL_CODE(1) for PCSC-Lite. But with another difference: the macro SCARD_CTL_CODE is not computed the same way between both systems!

As a consequence, the Java application must detect the OS, and compute the controlCode parameter accordingly.

Same example to switch the red LED on:

import javax.smartcardio.*;

(...)

static boolean isWindows()
{
  String os_name = System.getProperty("os.name").toLowerCase();
  if (os_name.indexOf("windows") > -1) return true;
  return false;
}

static int SCARD_CTL_CODE(int code)
{
  int ioctl;
  if (isWindows())
  {
    ioctl = (0x31 < < 16 | (code) << 2);
  } else
  {
    ioctl = 0x42000000 + (code);
  }
  return ioctl;
}

static int IOCTL_CCID_ESCAPE()
{
  if (isWindows())
  {
    return SCARD_CTL_CODE(3500);
  } else
  {
    return SCARD_CTL_CODE(1);
  }
}

static final byte[] SET_RED_LED_ON = { (byte) 0x58, (byte) 0x1E, (byte) 0x01, (byte) 0x00 };

(...)

String readerName;

/* Note that the reader's name vary with the OS too!!! */
if (isWindows())
  readerName = "SpringCard Prox'N'Roll Contactless 0";
else
  readerName = "SpringCard Prox'N'Roll (00000000) 00 00";

CardTerminal terminal = CardTerminals.getTerminal(readerName);

Card virtualCard = terminal.connect("DIRECT");

virtualCard.transmitControlCommand(IOCTL_CCID_ESCAPE(), SET_RED_LED_ON);

virtualCard.disconnect(false);

Of course this code works only if the Escape feature is enable by the underlying CCID driver, as seen above.