ISO15693 NXP SLIX-L features

[g3gg0]

This PR adds advanced ISO15693 emulation features to the proxmark3.
The chosen tag to emulate was a NXP SLIX-L. The emulation code does not
implement all functionalities the tag has, it merely focuses on privacy mode
and the password feature.
This blocking simulator code now exits whenever there is some USB communication.

It also adds some advanced features for SLIX-L tags, like locking or changing the password,
revealing the tag from privacy mode and a ISO15693 command scanner.

Porting these features to the latest commits caused some trouble, but it looks like
i got everything working again.

The simulator was tested with a closed source children audio system of a german manufacturer
which uses the SLIX-L tags in privacy mode in their system.

[pwpiwi]

Thank you very much for your contribution. Good work!

However, this adds a lot of code at the ARM side (appmain.c, iso15693.c) which should be avoided because space is very limited there. Specifically:

• why did you implement a standalone mode for card only functions?
• why did you implement specific commands CMD_ISO_15693_SLIX_L_DISABLE_PRIVACY, CMD_ISO_15693_SLIX_L_CHANGE_PASS, CMD_ISO_15693_SLIX_L_LOCK_PASS, CMD_ISO_15693_BRUTE_FORCE instead of using the generic CMD_ISO_15693_COMMAND?
• what is the purpose of StressSlixLIso15693()?

I would think that most of the functionality can be implemented in cmdhf15.c instead?

[g3gg0]

Thanks for your feedback.

When implementing this, I didn't have resources as primary goal.
Goal was to emulate SLIX-L tags for experiments with a closed ecosystem for children to play audio files from the cloud.

• The standalone mode is an optional thing to execute certain functions with a button press only
  i agree that this might be "too much" for most of the users, but it is not enabled by default.
  can remove this - or keep as a reference (like the other standalone modes were for me)

• the SLIX-L tags must not get powered off between the commands "get random" and other password related commands.
  disabling the field causes the random value in the tag to get dropped and authentication wont work
  i see these functions as "atomic" functions for NXP SLIX-L and would like to keep them.
  also the somewhat modular function design is smth i like personally. If resources are too low,
  having them static will even improve the flash usage compared to "hand-implement" those manually

• this is quite helpful to debunk the cheap chinese "yes yes its original NXP!" clones.
  had one of those which fail immediately when running a stress test.
  this is also something very optional and does not have to go into mainline

Thanks again for checking and your feedback on this.

[pwpiwi]

I am currently quite busy and cannot spend time on code reviews. If anybode else wants to step in...

At a first glance I see

• some hard coded passwords
• not using emulator memory
• functions implemented on device instead on client
• standalone mode for card only function. I am questioning standalone modes in general, but for card only functions (i.e. you don't need to approach a reader) they are definitely not required.