android - KitKat: How to route APDUs to the SIM

Question

I want to route APDUs I get from an NFC Reader to the SIM Card. According to the HCE documentation I thought it would be possible simply by creating an OffHostApduService with the according routing-entries (which I did).

Sadly, the SIM does not seem to get any APDUs. SELECT-Commands that work when the SIM is directly attached to my workstation by a SIM-Reader return with 6a82 (File not found).

In LogCat I found two interesting bits of information:

Every time I shoot a select command which should be routed to the SIM, I get these entries:

01-14 10:44:18.501: D/BrcmNfcJni(1009): RoutingManager::stackCallback: event=0x17
01-14 10:44:18.501: D/BrcmNfcJni(1009): RoutingManager::stackCallback: NFA_CE_DATA_EVT; h=0x302; data len=12
01-14 10:44:18.501: D/HostEmulationManager(1009): notifyHostEmulationData

I think that this is a clue that the routing is not set correctly, since I think the Android OS should not be aware when the routing to the SIM is active, and a select or another command is sent to the SIM.

Every time I remove the phone from the NFC field of the reader, I receive the following error:

01-14 10:46:48.791: E/BrcmNfcNfa(1009): UICC[0x0] is not activated

I tried to track the cause of this error down and found the file external/libnfc-nci/src/nfa/ce/nfa_ce_act.chere which seems to belong to the Broadcom NFC Driver.

I think that the mistake is that the application cannot set the correct routing for the APDUs since the driver thinks that the SIM is not activated. In the moment I send the commands, the SIM is unlocked (PIN-Entry), but I doubt that this has anything to do with it since I don't have to unlock the SIM before using it in the card reader.

I use a Nexus 5 for testing. Does anybody have experience and / or a working example where the APDUs can be routed to the SIM instead of the CPU?

Answer 1

A quick check (analyzing the signals on the SWP pin of a UICC inserted into the device) revealed that the Nexus 5 is not activating the SIM as an NFC secure element (neither at boot nor when putting the phone on a smartcard reader).

However, I found two interesting files on the device's system partition:

• /system/etc/libnfc-brcm-20791b05.conf and
• /system/etc/libnfc-brcm.conf.

These two files seem to provide the configuration for the NFC controller (the first one a chip-sepecific configuration and the second one a chip-family specific one?).

After unlocking the bootloader, I was able to modify those files through adb by booting a clockworkmod recovery image, so I did some experimenting with the configuration parameters.

The result is that I managed to let the device activate the UICC (UICC was activated and registered its CE gates through SWP?), the device sometimes even notified the UICC about field status changes. However, with none of my modified configurations, I was able to get the reader to smoothly discover card emulation (this was working before, when only HCE was available on the device) nor to communicate with the UICC.

The interesting parameters in /system/etc/libnfc-brcm.conf seem to be:

• NFA_MAX_EE_SUPPORTED: This is currently set to 0. I tried a value of 3, which seems to be the default.
• ACTIVE_SE: This is currently set to 0 (no active SE). I tried to uncomment that line to let the device use the first SE detected.
• NFA_HCI_STATIC_PIPE_ID_??: Should not be necessary but on out GS4 this is set to 0x71 for ?? = F3 and F4.
• UICC_LISTEN_TECH_MASK: This is set to 0x00 on our GS4.
• REGISTER_VIRTUAL_SE: I left this as it was (== commented out).
• SCREEN_OFF_POWER_STATE: I did not experiment with this, but on our GS4 this is set to 3 (screen-off CE).

The interesting parameters in /system/etc/libnfc-brcm-20791b05.conf seem to be:

• NFA_DM_START_UP_CFG: I've tried the commented-out parameters for UICC and I tried to use the configuration from our GS4. The value starts with a length byte and is structured in TLV format (one tag byte, one length byte, parameter data). The relevant tag for UICC activation seems to be C2, where the upper two bits in the second parameter byte disable the SWP interfaces of the NFC controller if set.
• NFA_DM_PRE_DISCOVERY_CFG: The comments suggest that this need to be uncommented for UICC support.