There has been some bug reports in upstream rdesktop about issues with SCardControl() not behaving properly:
This mainly affects secure pin entry, but could cause issues with other features that use SCardControl().
A fix was merged upstream here:
However this undid parts of the work we did for bug 3517. It also means that pcsctun and rdesktop are most likely out of sync as pcsctun needs to solve the same problem.
We need to have a look why upstream rdesktop and we came to different conclusions on how to handle this and what the proper way should be.
If we start changing things we also need to consider how that affects compatibility when mixing servers and clients of different versions.