WIP / RFC for pysim 'next generation;' aka pysim-shell

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Harald Welte laforge at gnumonks.org
Fri Jan 8 22:53:51 UTC 2021

Dear Osmocom community,

pySim-prog was nice when there were only 5 parameters on a SIM that we
could program, and where the use case was pretty limited.  Today, we
have SIM/USIM/ISIM cards with hundreds of files and even more parameters
to program.  We cannot add a command line argument for each file to

Instead, this introduces an interactive command-line shell / REPL,
in which one can navigate the file system of the card, read and update
files both in raw format and in decoded/parsed format.

The idea is primarily inspired by Henryk Ploetz' venerable
cyberflex-shell, but implemented on a more modern basis using
the cmd2 python module.

You can see the very first prototype in the laforge/shell branch of pysim.git

You can do things with it like this:

===> Start-up and authenticate with adm pin
$ ./pysim-shell.py -p 0
Using PC/SC reader interface
Autodetected card type: sysmoISIM-SJA2
AIDs on card: ['a0000000871002ffffffff8907090000', 'a0000000871004ffffffff8907090000']
Welcome to pySim-shell!
pySIM-shell (3f00)> verify_adm 92990895

===> interactive help
pySIM-shell (3f00)> help

Documented commands (use 'help -v' for verbose/'help <topic>' for details):

ISO7816 Commands
read_binary  select_adf  select_file  update_binary  update_record  verify_chv

pySim Commands
intro  verify_adm

USIM Commands
read_ehplmn  ust_service_activate  ust_service_deactivate

pySim-shell built-in commands
alias  help     macro  quit          run_script  shell
edit   history  py     run_pyscript  set         shortcuts


===> more interactive help
pySIM-shell (3f00)> help read_binary
usage: read_binary [-h] [--file-id FILE_ID] [--offset OFFSET] [--length LENGTH] [--record-nr RECORD_NR]

Read binary data from a transparent EF

optional arguments:
  -h, --help            show this help message and exit
  --file-id FILE_ID     File ID
  --offset OFFSET       Byte offset for start of read
  --length LENGTH       Number of bytes to read
  --record-nr RECORD_NR
                        Number of record to read

===> navigating the FS and reading files
pySIM-shell (3f00)> select_file 7f20
pySIM-shell (3f00/7f20)> read_binary --file-id 6f07

===> interaction with local filesystem, i.e. I/O redirect + shell commands
pySIM-shell (3f00)> select_adf a0000000871002
pySIM-shell (a0000000871002)> select_file 5f3b
pySIM-shell (a0000000871002/5f3b)> read_binary --file-id 4f20 > /tmp/f
pySIM-shell (a0000000871002/5f3b)> !cat /tmp/f

===> piping output through shell tools like grep
pySIM-shell (3f00)> read_ust  | grep 86
        Service 86 - Allowed CSG Lists and corresponding indications

===> enabling/disabling services
pySIM-shell (3f00/7f20)> ust_service_activate 123
pySIM-shell (3f00/7f20)> ust_service_deactivate 123

It's a very first prototype, but it is really promising.

The major tasks I see to make this go anywhere is:

* have "File" class with encoder/decoder methods, which are registered
  automatically with a 'file system' layer that knows about the DF/ADF
** this allows us to have a "read-decoded" command, which will
   call the decode method of the file, automatically resolved by the
   selected FID/path
* automatic mapping of file-name -> FID and FID -> file name
** when printing (like in the path), use the human-readable names
** allow users to use human-readable names in SELECT
* decode + display the TLVs / FCPs after a SELECT (like cyberflex-shell
* ability to enable/disable APDU trace
* dynamically register/deregster commands based on the path, i.e. offer
  USIM commands only when in ADF_USIM

We have quite a bit of that infrastructure in the c-language libosmosim,
(part of libosmocore.git), but unfortunately not in python :/

Let me know if anyone is interested in joining this effort.

- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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