Osmocom SIMtrace

Osmocom SIMtrace is a software and hardware system for passively tracing SIM-ME communication between the SIM card and the mobile phone.

It looks a bit like this:

When connected to a phone, it looks like this:

It works by utilizing the T=0 capable USART of the USB-attached AT91SAM7 microcontroller.

The USART passively receives the bytes as they are exchanged on the ISO 7816-3 / TS 11.11 interface between SIM and phone. The received bytes are sent via USB to the PC, where a program called simtrace on the PC gathers data from the USB device, parses the APDUs and forwards them via GSMTAP to the wireshark protocol analyzer.

Features

• Completely passive scanner
• RST and ATR detection
• Auto-bauding with PPS / PTS support
• Segmentation of APDUs

TODO

• Check for parity errors
• Verify TCK / PCK check-bytes
• Implement MITM

Hardware

The first implementations used an Olimex SAM7-P64 development board with some of the I/O lines hooked up to the mechanical SIM card adapters from RebelSIM_Scanner. If the RebelSIM scanner is used, connect the USB even if just the lines are used. It needs to be powered, else the real reader will often fail to initialize the card.

Now we have a dedicated PCB design. The schematics and Gerber files are released as open source hardware and can be produced by everyone.

However, those of you who are not interested in building it from scratch can buy a complete factory-produced, tested and flashed PCB assembly from  http://shop.sysmocom.de/products/simtrace

More details are available at SIMtrace/Hardware

Firmware

The firmware for the AT91SAM7S device was written by reusing a lot of the code for the  OpenPCD RFID reader. Details are available at SIMtrace/Firmware.

Host PC Software

The simtrace program is part of the  git://git.osmocom.org/simtrace.git repository. It will bind to the USB device and send GSMTAP frames using UDP/IPv4 to localhost:4729.

Preconditions

libosmocore and headers (simtrace_usb.h) from the firmware.

additional packages :

sudo apt-get install libusb-1.0-0-dev

Compiling it

git clone git://git.osmocom.org/simtrace.git
cd simtrace/host/
make

Using it

Simply start simtrace. It will send the GSMTAP frames to UDP/IPv4 localhost:4729.

It will also print hexdumps of the frames to the console, looking like this:

sudo ./simtrace
APDU: (9):  a0 a4 00 00 02 6f 07 9f 0f
APDU: (22):  a0 c0 00 00 0f 00 00 00 09 6f 07 04 00 15 00 15 01 02 00 00 91 78
APDU: (9):  a0 a4 00 00 02 6f 38 9f 0f
APDU: (22):  a0 c0 00 00 0f 00 00 00 09 6f 38 04 00 15 00 55 01 02 00 00 91 78
APDU: (16):  a0 b0 00 00 09 ff 3f ff ff 00 00 3f 03 00 91 78
APDU: (9):  a0 a4 00 00 02 6f ad 9f 0f
APDU: (8):  a0 b0 00 00 01 00 91 78
APDU: (9):  a0 a4 00 00 02 6f 07 9f 0f
APDU: (16):  a0 b0 00 00 09 08 49 06 20 11 49 00 11 06 91 78
APDU: (9):  a0 a4 00 00 02 6f 7e 9f 0f
APDU: (18):  a0 b0 00 00 0b ff ff ff ff 64 f0 00 ff fe 00 03 91 78
APDU: (9):  a0 a4 00 00 02 6f 78 9f 0f
APDU: (9):  a0 b0 00 00 02 00 01 91 78
APDU: (9):  a0 a4 00 00 02 6f 74 9f 0f
APDU: (23):  a0 b0 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 91 78
APDU: (9):  a0 a4 00 00 02 6f 20 9f 0f
APDU: (16):  a0 b0 00 00 09 ff ff ff ff ff ff ff ff 07 91 78
APDU: (9):  a0 a4 00 00 02 6f 30 9f 0f
APDU: (22):  a0 c0 00 00 0f 00 00 00 f0 6f 30 04 00 11 00 55 01 02 00 00 91 78

Wireshark integration

There is an experimental patch, also part of the simtrace.git package. You will have to apply this against the latest wireshark developer version.

Protocol parsing is far from being complete, patches are always welcome!

Contact / Mailing List

For any development or usage related questions, there is a mailinglist  simtrace@lists.osmocom.org, you can subscribe/unsubscribe to it at  http://lists.osmocom.org/mailman/listinfo/simtrace and read the archives at  http://lists.osmocom.org/pipermail/simtrace/

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