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tsaitgaist, 09/10/2019 04:21 PM
add limitations


Cardem

Card emulation (cardem for short) is a firmware for the SIMtrace v2 board allowing to emulate cards (e.g. SIM).
You then can leave the card adapter cable in the reader (e.g. phone), and have the actual card outside.
This allows to easily change or reprogram the card without having to touch the phone.

This functionality is already implemented and working on sysmoQMOD board.
It is not also available for SIMtrace v2 boards.
This is a beta firmware and still in development.
See limitations for known limitations and issues.

Flashing

You can download the beta firmware for the SIMtrace v2 board here: simtrace-cardem-flash.bin.

To flash the firmware on the board:

dfu-util --device 1d50:60e3 --cfg 1 --alt 1 --reset --download simtrace-cardem-flash.bin

For more details about the flashing procedure, read this article.

Software

With the cardem firmware, the SIMtrace v2 board mainly forwards the ISO 7816 card communication over USB.
A software on the host must receive the APDU requests and send the corresponding APDU response.
There are several software available to do that.
Since the USB messages are specified and the software is open source, you could implement your own APDU handler.

simtrace2-remsim

simtrace2-remsim is the simplest solution.
If forwards the APDU request/response to/from a PCSC card reader.

To get simtrace2-remsim:
  • Install required packages to compile the software:
    sudo apt-get install libusb-1.0-0-dev libosmocore-dev libpcsclite-dev
    
  • Get and compile the software:
    git clone git://git.osmocom.org/simtrace2.git
    cd simtrace2/host/
    make
    
To use simtrace2-remsim:
  1. power of phone
  2. insert card adapter cable into phone
  3. insert card adapter cable SIMtrace v2 board
  4. plug SIMtrace v2 board in host computer USB port
  5. connect external card reader to host (any USB CCID reader should do the job)
  6. install PCSC daemon (only need to be done once)
    sudo apt install pcscd
    
  7. ensure the PCSC daemon is started
    sudo systemctl start pcscd
    
  8. install tool to check reader status
    sudo systemctl start pcsc-tools
    
  9. check if the card is detected by the reader (use CTRL-C to exit)
    pcsc_scan 
    
    Using reader plug'n play mechanism
    Scanning present readers...
    0: OMNIKEY 6321 CLi USB (OKCM0030506091345044320140749730) 00 00
    
    Tue Sep 10 16:03:49 2019
     Reader 0: OMNIKEY 6321 CLi USB (OKCM0030506091345044320140749730) 00 00
      Event number: 0
      Card state: Card inserted, 
      ATR: 3B 9F 94 80 1F C7 80 31 E0 73 FE 21 1B 67 01 00 00 04 4D 02 01 99
    
  10. get SIMtrace USB path (this step will soon be not required anymore)
    dfu-util -l
    
    ...
    Found Runtime: [1d50:60e3] ver=0002, devnum=59, cfg=1, intf=1, path="1-2.2", alt=0, name="UNKNOWN", serial="UNKNOWN" 
    
  11. start simtrace2-remsim with corresponding USB path (here 1-2.2)
    ./simtrace2-remsim --usb-vendor 1d50 --usb-product 60e3 --usb-path 1-2.2 --usb-config 1
    
    (C) 2010-2017, Harald Welte <laforge@gnumonks.org>
    (C) 2018, sysmocom -s.f.m.c. GmbH, Author: Kevin Redon <kredon@sysmocom.de>
    
    SCardEstablishContext: OK
    
    SCardListReaders: OK
    
    SCardConnect: OK
    
    <- 01 05 00 00 00 00 09 00 01 
    <- 02 02 00 00 00 00 09 00 01 
    <= cardem_request_set_atr(3b 00 )
    <- 01 02 00 00 00 00 0b 00 02 3b 00 
    <- 02 01 00 00 00 00 0b 00 02 2c 01 
    Entering main loop
    
  12. now you can power on the phone (only after simtrace2-remsim is started since simtrace2-remsim can't tell the phone a card has been inserted). you should also see some APDU traffic
    URB: 01 06 00 00 00 00 13 00 01 00 00 00 05 00 a0 a4 00 00 02 
    -> 01 06 00 00 00 00 13 00 01 00 00 00 05 00 a0 a4 00 00 02 
    => DATA: flags=1, a0 a4 00 00 02 : CLA=a0 INS=a4 P1=00 P2=00 P3=02; case=4, lc=2(0), le=0(0)
    <= cardem_request_pb_and_rx(a4, 2)
    <- 01 01 00 00 00 00 0f 00 08 00 00 00 01 00 a4 
    URB: 01 06 00 00 00 00 10 00 02 00 00 00 02 00 7f 20 
    -> 01 06 00 00 00 00 10 00 02 00 00 00 02 00 7f 20 
    => DATA: flags=2, 7f 20 : CLA=a0 INS=a4 P1=00 P2=00 P3=02; case=4, lc=2(2), le=0(0)
    TX: a0 a4 00 00 02 7f 20 
    SCardEndTransaction: OK
    
    RX: 9f 17 
    SW=0x9f17, len_rx=0
    <= cardem_request_sw_tx(9f 17)
    <- 01 01 00 00 00 00 10 00 06 00 00 00 02 00 9f 17 
    URB: 01 06 00 00 00 00 13 00 01 00 00 00 05 00 a0 f2 00 00 17 
    -> 01 06 00 00 00 00 13 00 01 00 00 00 05 00 a0 f2 00 00 17 
    => DATA: flags=1, a0 f2 00 00 17 : CLA=a0 INS=f2 P1=00 P2=00 P3=17; case=2, lc=0(0), le=23(0)
    TX: a0 f2 00 00 17 
    SCardEndTransaction: OK
    

Limitations

Here are the known limitations:
  • there is no way for SIMtrace to tell the reader that a new card has been inserted. There is no specified way to do it (e.g. in ISO 7816 standard). This is generally done inside the reader hardware by a mechanical switch. The only way around is to restarted the reader (e.g. phone).
  • the cardem is currently a separate firmware. it is planned to combine it with the trace firmware (the software will then select the right functionality)
  • the firmware ignores the sent ATR (sent by the software, from the card to forward). this is to prevent the reader from switching to a yet untested baud rate
  • the error messages returned by simtrace2-remsim are not very useful
  • simtrace2-remsim does not automatically reconnect to the SIMtrace board when the hardware is reset
  • you have to specify the USB path to simtrace2-remsim
  • no long term tests have been performed (this is already planned)
  • you can't use the card reader built in SIMtrace
  • simtrace2-remsim does not send the APDU over network so you can trace the traffic using wireshark
  • simtrace2-remsim-udp does not connect to SIMtrace v2 boards

We are currently working on resolving these issues.
If you found yet unknown issues, you can report them to the main developer at kredon AT sysmocom DOT de.
If possible, please also attach the corresponding debug serial output. To get the serial output, connect a USB to UART cable either to the 2.5 mm stereo headphone connector (tip = TX, ring = RX, sleeve = GND) or the nearby DEBUG port (pin 1 = GND, pin 4 = TX, pin 5 = RX). Open the serial port with the following configuration: 921600 8N1.

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