SCardGetAttrib function (winscard.h)

Article
10/13/2021

The SCardGetAttrib function retrieves the current reader attributes for the given handle. It does not affect the state of the reader, driver, or card.

Syntax

LONG SCardGetAttrib(
  [in]      SCARDHANDLE hCard,
  [in]      DWORD       dwAttrId,
  [out]     LPBYTE      pbAttr,
  [in, out] LPDWORD     pcbAttrLen
);

Parameters

[in] hCard

Reference value returned from SCardConnect.

[in] dwAttrId

Identifier for the attribute to get. The following table lists possible values for dwAttrId. These values are read-only. Note that vendors may not support all attributes.

Value	Meaning
SCARD_ATTR_ATR_STRING	Answer to reset (ATR) string.
SCARD_ATTR_CHANNEL_ID	DWORD encoded as 0xDDDDCCCC, where DDDD = data channel type and CCCC = channel number: The following encodings are defined for DDDD: 0x01 serial I/O; CCCC is a port number. 0x02 parallel I/O; CCCC is a port number. 0x04 PS/2 keyboard port; CCCC is zero. 0x08 SCSI; CCCC is SCSI ID number. 0x10 IDE; CCCC is device number. 0x20 USB; CCCC is device number. 0xFy vendor-defined interface with y in the range zero through 15; CCCC is vendor defined.
SCARD_ATTR_CHARACTERISTICS	DWORD indicating which mechanical characteristics are supported. If zero, no special characteristics are supported. Note that multiple bits can be set: 0x00000001 Card swallowing mechanism 0x00000002 Card ejection mechanism 0x00000004 Card capture mechanism All other values are reserved for future use (RFU).
SCARD_ATTR_CURRENT_BWT	Current block waiting time.
SCARD_ATTR_CURRENT_CLK	Current clock rate, in kHz.
SCARD_ATTR_CURRENT_CWT	Current character waiting time.
SCARD_ATTR_CURRENT_D	Bit rate conversion factor.
SCARD_ATTR_CURRENT_EBC_ENCODING	Current error block control encoding. 0 = longitudinal redundancy check (LRC) 1 = cyclical redundancy check (CRC)
SCARD_ATTR_CURRENT_F	Clock conversion factor.
SCARD_ATTR_CURRENT_IFSC	Current byte size for information field size card.
SCARD_ATTR_CURRENT_IFSD	Current byte size for information field size device.
SCARD_ATTR_CURRENT_N	Current guard time.
SCARD_ATTR_CURRENT_PROTOCOL_TYPE	DWORD encoded as 0x0rrrpppp where rrr is RFU and should be 0x000. pppp encodes the current protocol type. Whichever bit has been set indicates which ISO protocol is currently in use. (For example, if bit zero is set, T=0 protocol is in effect.)
SCARD_ATTR_CURRENT_W	Current work waiting time.
SCARD_ATTR_DEFAULT_CLK	Default clock rate, in kHz.
SCARD_ATTR_DEFAULT_DATA_RATE	Default data rate, in bps.
SCARD_ATTR_DEVICE_FRIENDLY_NAME	Reader's display name.
SCARD_ATTR_DEVICE_IN_USE	Reserved for future use.
SCARD_ATTR_DEVICE_SYSTEM_NAME	Reader's system name.
SCARD_ATTR_DEVICE_UNIT	Instance of this vendor's reader attached to the computer. The first instance will be device unit 0, the next will be unit 1 (if it is the same brand of reader) and so on. Two different brands of readers will both have zero for this value.
SCARD_ATTR_ICC_INTERFACE_STATUS	Single byte. Zero if smart card electrical contact is not active; nonzero if contact is active.
SCARD_ATTR_ICC_PRESENCE	Single byte indicating smart card presence: 0 = not present 1 = card present but not swallowed (applies only if reader supports smart card swallowing) 2 = card present (and swallowed if reader supports smart card swallowing) 4 = card confiscated.
SCARD_ATTR_ICC_TYPE_PER_ATR	Single byte indicating smart card type: 0 = unknown type 1 = 7816 Asynchronous 2 = 7816 Synchronous Other values RFU.
SCARD_ATTR_MAX_CLK	Maximum clock rate, in kHz.
SCARD_ATTR_MAX_DATA_RATE	Maximum data rate, in bps.
SCARD_ATTR_MAX_IFSD	Maximum bytes for information file size device.
SCARD_ATTR_POWER_MGMT_SUPPORT	Zero if device does not support power down while smart card is inserted. Nonzero otherwise.
SCARD_ATTR_PROTOCOL_TYPES	DWORD encoded as 0x0rrrpppp where rrr is RFU and should be 0x000. pppp encodes the supported protocol types. A '1' in a given bit position indicates support for the associated ISO protocol, so if bits zero and one are set, both T=0 and T=1 protocols are supported.
SCARD_ATTR_VENDOR_IFD_SERIAL_NO	Vendor-supplied interface device serial number.
SCARD_ATTR_VENDOR_IFD_TYPE	Vendor-supplied interface device type (model designation of reader).
SCARD_ATTR_VENDOR_IFD_VERSION	Vendor-supplied interface device version (DWORD in the form 0xMMmmbbbb where MM = major version, mm = minor version, and bbbb = build number).
SCARD_ATTR_VENDOR_NAME	Vendor name.

[out] pbAttr

Pointer to a buffer that receives the attribute whose ID is supplied in dwAttrId. If this value is NULL, SCardGetAttrib ignores the buffer length supplied in pcbAttrLen, writes the length of the buffer that would have been returned if this parameter had not been NULL to pcbAttrLen, and returns a success code.

[in, out] pcbAttrLen

Length of the pbAttr buffer in bytes, and receives the actual length of the received attribute If the buffer length is specified as SCARD_AUTOALLOCATE, then pbAttr is converted to a pointer to a byte pointer, and receives the address of a block of memory containing the attribute. This block of memory must be deallocated with SCardFreeMemory.

Return value

This function returns different values depending on whether it succeeds or fails.

Return code	Description
Success	SCARD_S_SUCCESS.
Attribute value not supported.	ERROR_NOT_SUPPORTED.
Other Failure	An error code. For more information, see Smart Card Return Values.

Remarks

The SCardGetAttrib function is a direct card access function. For more information on other direct access functions, see Direct Card Access Functions.

Examples

The following example shows how to retrieve an attribute for a card reader. The example assumes that hCardHandle is a valid handle obtained from a previous call to the SCardConnect function.

LPBYTE   pbAttr = NULL;
DWORD    cByte = SCARD_AUTOALLOCATE;
DWORD    i;
LONG     lReturn;

lReturn = SCardGetAttrib(hCardHandle,
                         SCARD_ATTR_VENDOR_NAME,
                         (LPBYTE)&pbAttr,
                         &cByte);
if ( SCARD_S_SUCCESS != lReturn )
{
    if ( ERROR_NOT_SUPPORTED == lReturn )
        printf("Value not supported\n");
    else
    {
        // Some other error occurred.
        printf("Failed SCardGetAttrib - %x\n", lReturn);
        exit(1);  // Or other appropriate action
    }
}
else
{
    // Output the bytes.
    for (i = 0; i < cByte; i++)
        printf("%c", *(pbAttr+i));
    printf("\n");

    // Free the memory when done.
    // hContext was set earlier by SCardEstablishContext
    lReturn = SCardFreeMemory( hContext, pbAttr );
}

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	winscard.h
Library	Winscard.lib
DLL	Winscard.dll

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