From c8e62965bc90eabff5c4b7cb349bd8e41584c01b Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Tue, 25 Jun 2019 09:23:38 +0200
Subject: [PATCH] scd: Return a stable list with "getinfo card_list".

* scd/app.c (compare_card_list_items): New.
(app_send_card_list): Sort the card objects by slot.
--

This is required so that in gpg-card a "list N" command always returns
the expected card.  Sorting by slot should be sufficient.

Signed-off-by: Werner Koch <wk@gnupg.org>
---
 scd/app-common.h |  2 +-
 scd/app.c        | 41 +++++++++++++++++++++++++++++++++++++----
 scd/command.c    |  2 +-
 3 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/scd/app-common.h b/scd/app-common.h
index 97b9b39ef..460046f89 100644
--- a/scd/app-common.h
+++ b/scd/app-common.h
@@ -223,7 +223,7 @@ const char *strcardtype (cardtype_t t);
 const char *strapptype (apptype_t t);
 
 void app_update_priority_list (const char *arg);
-void app_send_card_list (ctrl_t ctrl);
+gpg_error_t app_send_card_list (ctrl_t ctrl);
 char *card_get_serialno (card_t card);
 char *app_get_serialno (app_t app);
 
diff --git a/scd/app.c b/scd/app.c
index c568b636b..1ad6b9ed6 100644
--- a/scd/app.c
+++ b/scd/app.c
@@ -1601,22 +1601,55 @@ initialize_module_command (void)
 }
 
 
-void
+/* Sort helper for app_send_card_list.  */
+static int
+compare_card_list_items (const void *arg_a, const void *arg_b)
+{
+  const card_t a = *(const card_t *)arg_a;
+  const card_t b = *(const card_t *)arg_b;
+
+  return a->slot - b->slot;
+}
+
+
+/* Send status lines with the serialno of all inserted cards.  */
+gpg_error_t
 app_send_card_list (ctrl_t ctrl)
 {
+  gpg_error_t err;
   card_t c;
   char buf[65];
+  card_t *cardlist = NULL;
+  int n, ncardlist;
 
   npth_mutex_lock (&card_list_lock);
-  for (c = card_top; c; c = c->next)
+  for (n=0, c = card_top; c; c = c->next)
+    n++;
+  cardlist = xtrycalloc (n, sizeof *cardlist);
+  if (!cardlist)
     {
-      if (DIM (buf) < 2 * c->serialnolen + 1)
+      err = gpg_error_from_syserror ();
+      goto leave;
+    }
+  for (ncardlist=0, c = card_top; c; c = c->next)
+    cardlist[ncardlist++] = c;
+  qsort (cardlist, ncardlist, sizeof *cardlist, compare_card_list_items);
+
+  for (n=0; n < ncardlist; n++)
+    {
+      if (DIM (buf) < 2 * cardlist[n]->serialnolen + 1)
         continue;
 
-      bin2hex (c->serialno, c->serialnolen, buf);
+      bin2hex (cardlist[n]->serialno, cardlist[n]->serialnolen, buf);
       send_status_direct (ctrl, "SERIALNO", buf);
     }
+
+  err = 0;
+
+ leave:
   npth_mutex_unlock (&card_list_lock);
+  xfree (cardlist);
+  return err;
 }
 
 
diff --git a/scd/command.c b/scd/command.c
index 2b851c5fd..f341b6ae2 100644
--- a/scd/command.c
+++ b/scd/command.c
@@ -1630,7 +1630,7 @@ cmd_getinfo (assuan_context_t ctx, char *line)
     {
       ctrl_t ctrl = assuan_get_pointer (ctx);
 
-      app_send_card_list (ctrl);
+      rc = app_send_card_list (ctrl);
     }
   else
     rc = set_error (GPG_ERR_ASS_PARAMETER, "unknown value for WHAT");