SIM Application toolkit commands

[Ronald Franks]

Aleksander,

The Twilio Super SIM will send a Proactive Command NAA Initialization and
Full File Change Notification to the terminal on the IMSI change. Some
modems, like the Quectel BG95 or EC25 will send a URC if
+QUSIM: 1
if it is a USIM and
+QUSIM: 0
if it's a regular SIM
no idea about other modems however.

I can arrange to get you a SIM for testing if needed as this is an area I'm
interested in as well. I can also provide a SIMtrace2 pcap (or raw APDUs if
preferred) capture of the communications between the terminal and the SIM
if that would be helpful.

On Wed, May 3, 2023 at 6:24 AM Aleksander Morgado <aleksandermj at chromium.org>
wrote:

> > > Does ModemManager support SIM application tool kit with proactive SIM
> > > commands? My assumption is most of these SIM application tool kit
> > > commands should be handled by the modem but I'm unclear what is the
> > > role of host CPU / ModemManager in these commands? For example, many
> > > SIMs support multi-IMSI i.e. depending on the location, a particular
> > > IMSI is used for network connection. When a SIM changes its IMSI, the
> > > SIM application tool kit applet sends a REFRESH proactive command to
> > > the host device (or modem). This instructs the device to re-read the
> > > data on the SIM, including the new IMSI.
> >
> > Currently, ModemManager does not support any SIM application tool kit
> > commands. SIM toolkit apps displaying emergency numbers etc. are
> > currently not possible with ModemManager.
> >
> > >
> > > So how shall ModemManager know that IMSI has been changed and what it
> > > is supposed to do? What is the role of ModemManager in handling these
> > > commands?
> >
> > If the modem emits an AT URC / QMI / MBIM Indication, ModemManager
> > might be able to handle it, but I'm not sure.
> >
>
> This is right. As we don't support generic SIM STK operations in MM.
> We currently only support the multi-IMSI scenario on QMI modems when
> they send an explicit notification about the change (e.g. UIM Refresh
> indication, see 5c0db3743209b78d8c7b7558e337e6df25951bae).
>
> I actually need to investigate the IMSI switch procedure while in
> MBIM, it's in my TODO list for the next weeks. I assume that maybe
> using the STK service we could be notified of the same.
>
> --
> Aleksander
>
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