Monday, December 21, 2015

Remove and/or customize PC/SC reader names

The need

In some cases you need to control the smart card reader names reported by PC/SC.

For real examples see some requests sent on the Pcsclite-muscle mailing list: "Possibility to disable Reader Interface?", "Deny card access for one application" and "Dynamically disable/enable specific card reader".

Ignore some readers

For example imagine you have a laptop with 2 integrated smart card readers:
  • Broadcom Corp 5880 [Contacted SmartCard] (0123456789ABCD)
  • Broadcom Corp 5880 [Contactless SmartCard] (0123456789ABCD)
One reader is contactless but you do not use it. The other is a contact reader and should be the only one used but the users of the laptop.
To ease the life of the users you do not want them to have to select the contact reader each time an application has to use a reader and ask the user to select one.

Since the readers are integrated into the laptop you can't easily unplug the reader you don't want to use. You need a solution to ignore unwanted readers at the PC/SC level.

Extend reader names

In this use case you use a remote desktop solution (RDP) to access a Windows server from your GNU/Linux laptop. Your company has equipped users with the same laptop model. So at the PC/SC level all the readers have the same name and this PC/SC name is forwarded to Windows through RDP.

Now imagine a bogus application on the Windows server (not too hard to imagine a bogus application on Windows ☺) that uses the PC/SC reader name to identify a user. Since every user is using the same laptop model they will all have the same PC/SC reader name in Windows. And the bogus Windows application is broken ☹ and can't be used.

The proposed solution

To enable these two features you need to configure pcsc-lite with --enable-filter.

Ignore some readers

If the environment variable PCSCLITE_FILTER_IGNORE_READER_NAMES is defined then it contains a list of patterns separated by the character ":".
If a pattern is found in a PC/SC reader name then this reader is ignored and will not be reported by SCardListReaders() or any other PC/SC calls.

In the example described above you would define PCSCLITE_FILTER_IGNORE_READER_NAMES as: "Contactless".

Extend reader names

To differentiate the PC/SC reader names one idea is to use the host name of the system. If the IT department is doing correctly his job every laptop should have a different host name.

If the environment variable PCSCLITE_FILTER_EXTEND_READER_NAMES is defined then it contains a string that will be added at the end of the PC/SC reader names.
The computer host name is available in the variable $HOSTNAME. If you want to have a space character between the PC/SC reader name and host name you define PCSCLITE_FILTER_EXTEND_READER_NAMES as:


The Debian init script for pcscd contains:

# Read configuration variable file if it is present
[ -r /etc/default/$NAME ] && . /etc/default/$NAME

You then just have to create a file /etc/default/pcscd containing:
And you are good to go.

GNU/Linux systems using systemd will need a different configuration. The systemd configuration is left as an exercise for the reader.


These new features will be provided in the next version of pcsc-lite.

If you have another special feature request for pcsc-lite, please do not hesitate to contact me.


Thanks to Sparkasse Pforzheim Calw for the patch.