[PATCH gnupg] scd: Add Nitrokey 3 to pcsc-shared interference detection

[NIIBE Yutaka]

Hello,

For merging your work, I think that there are two things:

(1) PC/SC shared option and change of maybe_switch_app

IIUC, you suggest to modify the maybe_switch_app function so that it can
call fnc.reselect method when PC/SC shared is enabled and device is
Yubikey/Nitrokey.

(2) Nitrokey specific things

That is: detecting Nitrokey and scdaemon's behavior tweaks when it's
Nitrokey.


For (1), let me confirm with no consideration of Nitrokey, firstly.
The changes are like following.

==========================
diff --git a/scd/app.c b/scd/app.c
index 63eb84190..6f74e8c42 100644
--- a/scd/app.c
+++ b/scd/app.c
@@ -1792,12 +1792,15 @@ maybe_switch_app (ctrl_t ctrl, card_t card, const char *keyref)
   if (!card->app)
     return gpg_error (GPG_ERR_CARD_NOT_INITIALIZED);
 
-  if (card->maybe_check_aid && card->app->fnc.reselect
+  if ((card->maybe_check_aid
+       || (opt.pcsc_shared && card->cardtype == CARDTYPE_YUBIKEY))
+      && card->app->fnc.reselect
       && check_external_interference (card->app, ctrl))
     {
       if (DBG_APP)
-        log_debug ("slot %d, app %s: forced re-select due to direct APDU use\n",
-                   card->slot, xstrapptype (card->app));
+        log_debug ("slot %d, app %s: forced re-select due to %s\n",
+                   card->slot, xstrapptype (card->app),
+                   card->maybe_check_aid? "direct APDU use" : "pcsc-shared");
       err = card->app->fnc.reselect (card->app, ctrl);
       if (err)
         log_error ("slot %d, app %s: forced re-select failed: %s - ignored\n",
==========================

I wonder if the condition

	card->cardtype == CARDTYPE_YUBIKEY

is really needed or not.  If it's not strictly required, I'd prefer to
change without this condition.  (Or else, we will need to add Nitrokey
condition here.)

If it is OK with no-cardtype condition, I will push the change firstly.
Then, focus on (2).


I struggle with (2), using USBIP emulation (found it's not exact
emulation, at least ATR is different).  Tentative work is in
https://dev.gnupg.org/T8331
--