scd: Add code to check whether app switching is possible.

* scd/app.c (check_conflict): Fold into ...
(check_application_conflict): this and adjust callers.  Return a
different error code if it is possible to switch apps.
--

Right now this change does nothing visible.

Signed-off-by: Werner Koch <wk@gnupg.org>

scd/app-common.h

@@ -228,7 +228,7 @@ char *app_get_serialno (app_t app);
 
 void app_dump_state (void);
 void application_notify_card_reset (int slot);
-gpg_error_t check_application_conflict (const char *name, card_t card);
+gpg_error_t check_application_conflict (card_t card, const char *name);
 gpg_error_t card_reset (card_t card, ctrl_t ctrl, int send_reset);
 gpg_error_t select_application (ctrl_t ctrl, const char *name, card_t *r_app,
                                 int scan, const unsigned char *serialno_bin,

scd/app.c

@@ -235,15 +235,23 @@ is_app_allowed (const char *name)
 }
 
 
-static gpg_error_t
+/* This function is mainly used by the serialno command to check for
-check_conflict (card_t card, const char *name)
+ * an application conflict which may appear if the serialno command is
+ * used to request a specific application and the connection has
+ * already done a select_application.   Return values are:
+ *   0              - No conflict
+ *   GPG_ERR_FALSE  - Another application is in use but it is possible
+ *                    to switch to the requested application.
+ *   other code     - Switching is not possible.
+ */
+gpg_error_t
+check_application_conflict (card_t card, const char *name)
 {
   if (!card || !name)
     return 0;
   if (!card->app)
     return gpg_error (GPG_ERR_CARD_NOT_INITIALIZED); /* Should not happen.  */
 
-  /* FIXME:  Needs changes for app switching.  */
   if (!card->app->apptype
       || !ascii_strcasecmp (strapptype (card->app->apptype), name))
     return 0;
@@ -251,6 +259,22 @@ check_conflict (card_t card, const char *name)
   if (card->app->apptype == APPTYPE_UNDEFINED)
     return 0;
 
+  if (card->cardtype == CARDTYPE_YUBIKEY)
+    {
+      if (card->app->apptype == APPTYPE_OPENPGP)
+        {
+          /* Current app is OpenPGP.  */
+          if (!ascii_strcasecmp (name, "piv"))
+            return gpg_error (GPG_ERR_FALSE);  /* Switching allowed.  */
+        }
+      else if (card->app->apptype == APPTYPE_PIV)
+        {
+          /* Current app is PIV.  */
+          if (!ascii_strcasecmp (name, "openpgp"))
+            return gpg_error (GPG_ERR_FALSE);  /* Switching allowed.  */
+        }
+    }
+
   log_info ("application '%s' in use - can't switch\n",
             strapptype (card->app->apptype));
 
@@ -258,17 +282,6 @@ check_conflict (card_t card, const char *name)
 }
 
 
-/* This function is used by the serialno command to check for an
-   application conflict which may appear if the serialno command is
-   used to request a specific application and the connection has
-   already done a select_application. */
-gpg_error_t
-check_application_conflict (const char *name, card_t card)
-{
-  return check_conflict (card, name);
-}
-
-
 gpg_error_t
 card_reset (card_t card, ctrl_t ctrl, int send_reset)
 {
@@ -607,7 +620,7 @@ select_application (ctrl_t ctrl, const char *name, card_t *r_card,
 
   if (card)
     {
-      err = check_conflict (card, name);
+      err = check_application_conflict (card, name);
       if (!err)
         {
           /* Note: We do not use card_ref as we are already locked.  */

scd/command.c

@@ -220,7 +220,8 @@ open_card (ctrl_t ctrl)
 
 /* Explicitly open a card for a specific use of APPTYPE or SERIALNO.  */
 static gpg_error_t
-open_card_with_request (ctrl_t ctrl, const char *apptype, const char *serialno)
+open_card_with_request (ctrl_t ctrl,
+                        const char *apptypestr, const char *serialno)
 {
   gpg_error_t err;
   unsigned char *serialno_bin = NULL;
@@ -231,8 +232,8 @@ open_card_with_request (ctrl_t ctrl, const char *apptype, const char *serialno)
      need to check that the client didn't requested a specific
      application different from the one in use before we continue. */
   /* FIXME: Extend to allow switching between apps.  */
-  if (apptype && ctrl->card_ctx)
+  if (apptypestr && ctrl->card_ctx)
-    return check_application_conflict (apptype, ctrl->card_ctx);
+    return check_application_conflict (ctrl->card_ctx, apptypestr);
 
   /* Re-scan USB devices.  Release CARD, before the scan.  */
   /* FIXME: Is a card_unref sufficient or do we need to deallocate?  */
@@ -242,7 +243,7 @@ open_card_with_request (ctrl_t ctrl, const char *apptype, const char *serialno)
   if (serialno)
     serialno_bin = hex_to_buffer (serialno, &serialno_bin_len);
 
-  err = select_application (ctrl, apptype, &ctrl->card_ctx, 1,
+  err = select_application (ctrl, apptypestr, &ctrl->card_ctx, 1,
                             serialno_bin, serialno_bin_len);
   xfree (serialno_bin);