scd: New commands SWITCHCARD and SWITCHAPP.

* scd/app.c: Include membuf.h.
(app_switch_current_card): New.
(send_card_and_app_list): Factor code out to ...
(send_serialno_and_app_status): new.
(app_send_card_list): New.
(app_send_active_apps): New.
(app_switch_active_app): New.
* scd/command.c (cmd_switchcard): New.
(cmd_switchapp): New.
(register_commands): Register new commands.
(cmd_getinfo): New sub-commands "active_apps" and "all_active_apps".
--

These new commands allow to switch between known cards and are in
particular useful for the gpg-card tool.

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

scd/app-common.h

@@ -229,6 +229,7 @@ const char *strapptype (apptype_t t);
 
 void app_update_priority_list (const char *arg);
 gpg_error_t app_send_card_list (ctrl_t ctrl);
+gpg_error_t app_send_active_apps (card_t card, ctrl_t ctrl);
 char *card_get_serialno (card_t card);
 char *app_get_serialno (app_t app);
 
@@ -242,6 +243,13 @@ gpg_error_t select_application (ctrl_t ctrl, const char *name, card_t *r_app,
                                 int scan, const unsigned char *serialno_bin,
                                 size_t serialno_bin_len);
 gpg_error_t select_additional_application (ctrl_t ctrl, const char *name);
+
+gpg_error_t app_switch_current_card (ctrl_t ctrl,
+                                     const unsigned char *serialno,
+                                     size_t serialnolen);
+gpg_error_t app_switch_active_app (card_t card, ctrl_t ctrl,
+                                   const char *appname);
+
 char *get_supported_applications (void);
 
 card_t card_ref (card_t card);

scd/app.c

@@ -29,11 +29,14 @@
 #include "iso7816.h"
 #include "apdu.h"
 #include "../common/tlv.h"
+#include "../common/membuf.h"
 
 
 /* Forward declaration of internal function.  */
 static gpg_error_t
 select_additional_application_internal (card_t card, apptype_t req_apptype);
+static gpg_error_t
+send_serialno_and_app_status (card_t card, int with_apps, ctrl_t ctrl);
 
 /* Lock to protect the list of cards and its associated
  * applications.  */
@@ -730,6 +733,56 @@ select_application (ctrl_t ctrl, const char *name, card_t *r_card,
 }
 
 
+/* Switch the current card for the session CTRL and print a SERIALNO
+ * status line on success.  (SERIALNO, SERIALNOLEN) is the binary s/n
+ * of the card to switch to.  */
+gpg_error_t
+app_switch_current_card (ctrl_t ctrl,
+                         const unsigned char *serialno, size_t serialnolen)
+{
+  gpg_error_t err;
+  card_t card, cardtmp;
+
+  npth_mutex_lock (&card_list_lock);
+
+  if (!ctrl->card_ctx)
+    {
+      err = gpg_error (GPG_ERR_CARD_NOT_INITIALIZED);
+      goto leave;
+    }
+
+  if (serialno && serialnolen)
+    {
+      for (card = card_top; card; card = card->next)
+        {
+          if (card->serialnolen == serialnolen
+              && !memcmp (card->serialno, serialno, card->serialnolen))
+            break;
+        }
+      if (!card)
+        {
+          err = gpg_error (GPG_ERR_NOT_FOUND);
+          goto leave;
+        }
+
+      /* Note: We do not use card_ref here because we only swap the
+       * context of the current session and there is no chance of a
+       * context switch.  This also works if the card stays the same. */
+      cardtmp = ctrl->card_ctx;
+      ctrl->card_ctx = card;
+      card->ref_count++;
+      card_unref_locked (cardtmp);
+    }
+
+  /* Print the status line.  */
+  err = send_serialno_and_app_status (ctrl->card_ctx, 0, ctrl);
+
+ leave:
+  npth_mutex_unlock (&card_list_lock);
+  return err;
+}
+
+
 static gpg_error_t
 select_additional_application_internal (card_t card, apptype_t req_apptype)
 {
@@ -1975,13 +2028,58 @@ compare_card_list_items (const void *arg_a, const void *arg_b)
 }
 
 
-/* Send status lines with the serialno of all inserted cards.  */
+/* Helper for send_card_and_app_list and app_switch_active_app.  */
-gpg_error_t
+static gpg_error_t
-app_send_card_list (ctrl_t ctrl)
+send_serialno_and_app_status (card_t card, int with_apps, ctrl_t ctrl)
+{
+  gpg_error_t err;
+  app_t a;
+  char buf[65];
+  char *p;
+  membuf_t mb;
+
+  if (DIM (buf) < 2 * card->serialnolen + 1)
+    return 0; /* Oops.  */
+
+  bin2hex (card->serialno, card->serialnolen, buf);
+  if (with_apps)
+    {
+      /* Note that in case the additional applications have not yet been
+       * added to the card context (which is commonly done by means of
+       * "SERIALNO --all", we do that here.  */
+      err = select_all_additional_applications_internal (card);
+      if (err)
+        return err;
+
+      init_membuf (&mb, 256);
+      put_membuf_str (&mb, buf);
+      for (a = card->app; a; a = a->next)
+        {
+          if (!a->fnc.with_keygrip)
+            continue;
+          put_membuf (&mb, " ", 1);
+          put_membuf_str (&mb, xstrapptype (a));
+        }
+      put_membuf (&mb, "", 1);
+      p = get_membuf (&mb, NULL);
+      if (!p)
+        return gpg_error_from_syserror ();
+      send_status_direct (ctrl, "SERIALNO", p);
+      xfree (p);
+    }
+  else
+    send_status_direct (ctrl, "SERIALNO", buf);
+
+  return 0;
+}
+
+
+/* Common code for app_send_card_list and app_send_active_apps.  */
+static gpg_error_t
+send_card_and_app_list (ctrl_t ctrl, card_t wantcard, int with_apps)
 {
   gpg_error_t err;
   card_t c;
-  char buf[65];
   card_t *cardlist = NULL;
   int n, ncardlist;
 
@@ -2000,11 +2098,11 @@ app_send_card_list (ctrl_t ctrl)
 
   for (n=0; n < ncardlist; n++)
     {
-      if (DIM (buf) < 2 * cardlist[n]->serialnolen + 1)
+      if (wantcard && wantcard != cardlist[n])
         continue;
-
+      err = send_serialno_and_app_status (cardlist[n], with_apps, ctrl);
-      bin2hex (cardlist[n]->serialno, cardlist[n]->serialnolen, buf);
+      if (err)
-      send_status_direct (ctrl, "SERIALNO", buf);
+        goto leave;
     }
 
   err = 0;
@@ -2016,6 +2114,69 @@ app_send_card_list (ctrl_t ctrl)
 }
 
 
+/* Send status lines with the serialno of all inserted cards.  */
+gpg_error_t
+app_send_card_list (ctrl_t ctrl)
+{
+  return send_card_and_app_list (ctrl, NULL, 0);
+}
+
+
+/* Send status lines with the serialno and appname of the current card
+ * or of all cards if CARD is NULL.  */
+gpg_error_t
+app_send_active_apps (card_t card, ctrl_t ctrl)
+{
+  return send_card_and_app_list (ctrl, card, 1);
+}
+
+
+/* Switch to APPNAME and print a respective status line with that app
+ * listed first.  If APPNAME is NULL or the empty string no switching
+ * is done but the status line is printed anyway.  */
+gpg_error_t
+app_switch_active_app (card_t card, ctrl_t ctrl, const char *appname)
+{
+  gpg_error_t err;
+  apptype_t apptype;
+
+  if (!card)
+    return gpg_error (GPG_ERR_INV_VALUE);
+  err = lock_card (card, ctrl);
+  if (err)
+    return err;
+
+  /* Note that in case the additional applications have not yet been
+   * added to the card context (which is commonly done by means of
+   * "SERIALNO --all", we do that here.  */
+  err = select_all_additional_applications_internal (card);
+  if (err)
+    goto leave;
+
+  if (appname && *appname)
+    {
+      apptype = apptype_from_name (appname);
+      if (!apptype)
+        {
+          err = gpg_error (GPG_ERR_NOT_FOUND);
+          goto leave;
+        }
+
+      ctrl->current_apptype = apptype;
+      err = maybe_switch_app (ctrl, card, NULL);
+      if (err)
+        goto leave;
+    }
+
+  /* Print the status line.  */
+  err = send_serialno_and_app_status (card, 1, ctrl);
+
+ leave:
+  unlock_card (card);
+  return err;
+}
+
+
 /* Execute an action for each app.  ACTION can be one of:
  *
  * - KEYGRIP_ACTION_SEND_DATA

scd/command.c

@@ -287,8 +287,7 @@ static const char hlp_serialno[] =
   "If APPTYPE is given, an application of that type is selected and an\n"
   "error is returned if the application is not supported or available.\n"
   "The default is to auto-select the application using a hardwired\n"
-  "preference system.  Note, that a future extension to this function\n"
+  "preference system.\n"
-  "may enable specifying a list and order of applications to try.\n"
   "\n"
   "This function is special in that it can be used to reset the card.\n"
   "Most other functions will return an error when a card change has\n"
@@ -354,6 +353,70 @@ cmd_serialno (assuan_context_t ctx, char *line)
 }
 
 
+
+static const char hlp_switchcard[] =
+  "SWITCHCARD [<serialno>]\n"
+  "\n"
+  "Make the card with SERIALNO the current card.\n"
+  "The command \"getinfo card_list\" can be used to list\n"
+  "the serial numbers of inserted and known cards.  Note\n"
+  "that the command \"SERIALNO\" can be used to refresh\n"
+  "the list of known cards.  A simple SERIALNO status\n"
+  "is printed on success.";
+static gpg_error_t
+cmd_switchcard (assuan_context_t ctx, char *line)
+{
+  ctrl_t ctrl = assuan_get_pointer (ctx);
+  gpg_error_t err = 0;
+  unsigned char *sn_bin = NULL;
+  size_t sn_bin_len = 0;
+
+  if ((err = open_card (ctrl)))
+    return err;
+
+  line = skip_options (line);
+
+  if (*line)
+    {
+      sn_bin = hex_to_buffer (line, &sn_bin_len);
+      if (!sn_bin)
+        {
+          err = gpg_error_from_syserror ();
+          goto leave;
+        }
+    }
+
+  /* Note that an SN_BIN of NULL will only print the status.  */
+  err = app_switch_current_card (ctrl, sn_bin, sn_bin_len);
+
+ leave:
+  xfree (sn_bin);
+  return err;
+}
+
+
+static const char hlp_switchapp[] =
+  "SWITCHAPP [<appname>]\n"
+  "\n"
+  "Make APPNAME the active application for the current card.\n"
+  "Only some cards support switching between application; the\n"
+  "command \"getinfo active_app\" can be used to get a list of\n"
+  "applications which can be switched to.  A SERIALNO status\n"
+  "including the active appname is printed on success.";
+static gpg_error_t
+cmd_switchapp (assuan_context_t ctx, char *line)
+{
+  ctrl_t ctrl = assuan_get_pointer (ctx);
+  gpg_error_t err = 0;
+
+  if ((err = open_card (ctrl)))
+    return err;
+
+  line = skip_options (line);
+  return app_switch_active_app (ctrl->card_ctx, ctrl, line);
+}
+
+
 static const char hlp_learn[] =
   "LEARN [--force] [--keypairinfo] [--multi]\n"
   "\n"
@@ -1641,10 +1704,12 @@ static const char hlp_getinfo[] =
   "  app_list    - Return a list of supported applications.  One\n"
   "                application per line, fields delimited by colons,\n"
   "                first field is the name.\n"
-  "  card_list   - Return a list of serial numbers of active cards,\n"
+  "  card_list   - Return a list of serial numbers of all inserted cards.\n"
-  "                using a status response.\n"
+  "  active_apps - Return a list of active apps on the current card.\n"
+  "  all_active_apps\n"
+  "              - Return a list of active apps on all inserted cards.\n"
   "  cmd_has_option CMD OPT\n"
-  "                  - Returns OK if command CMD has option OPT.\n";
+  "               - Returns OK if command CMD has option OPT.\n";
 static gpg_error_t
 cmd_getinfo (assuan_context_t ctx, char *line)
 {
@@ -1753,6 +1818,19 @@ cmd_getinfo (assuan_context_t ctx, char *line)
 
       rc = app_send_card_list (ctrl);
     }
+  else if (!strcmp (line, "active_apps"))
+    {
+      ctrl_t ctrl = assuan_get_pointer (ctx);
+      if (!ctrl->card_ctx)
+        rc = 0; /* No current card - no active apps.  */
+      else
+        rc = app_send_active_apps (ctrl->card_ctx, ctrl);
+    }
+  else if (!strcmp (line, "all_active_apps"))
+    {
+      ctrl_t ctrl = assuan_get_pointer (ctx);
+      rc = app_send_active_apps (NULL, ctrl);
+    }
   else
     rc = set_error (GPG_ERR_ASS_PARAMETER, "unknown value for WHAT");
   return rc;
@@ -2069,6 +2147,8 @@ register_commands (assuan_context_t ctx)
     const char * const help;
   } table[] = {
     { "SERIALNO",     cmd_serialno, hlp_serialno },
+    { "SWITCHCARD",   cmd_switchcard,hlp_switchcard },
+    { "SWITCHAPP",    cmd_switchapp,hlp_switchapp },
     { "LEARN",        cmd_learn,    hlp_learn },
     { "READCERT",     cmd_readcert, hlp_readcert },
     { "READKEY",      cmd_readkey,  hlp_readkey },