scd: Slight change to app->fnc.do_with_keygrip.

* scd/app-openpgp.c (do_with_keygrip): Return a real error code to
avoid misinterpretation of the result.  Also fix the case for a too
small buffer.
--

The only real chnage is the case for a too small buffer.  That should
in general never happen but if so we now return an error instead of
success.

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

scd/app-common.h

@@ -126,11 +126,13 @@ struct app_ctx_s {
     gpg_error_t (*check_pin) (app_t app, const char *keyidstr,
                       gpg_error_t (*pincb)(void*, const char *, char **),
                       void *pincb_arg);
-    int (*with_keygrip) (app_t app, ctrl_t ctrl, int action,
-                         const char *keygrip_str);
+    gpg_error_t (*with_keygrip) (app_t app, ctrl_t ctrl, int action,
+                                 const char *keygrip_str);
   } fnc;
 };
 
+
+/* Action values for app_do_with_keygrip.  */
 enum
  {
   KEYGRIP_ACTION_SEND_DATA,
@@ -138,6 +140,7 @@ enum
   KEYGRIP_ACTION_LOOKUP
  };
 
+
 /*-- app-help.c --*/
 unsigned int app_help_count_bits (const unsigned char *a, size_t len);
 gpg_error_t app_help_get_keygrip_string_pk (const void *pk, size_t pklen,

scd/app-openpgp.c

@@ -4913,7 +4913,7 @@ do_check_pin (app_t app, const char *keyidstr,
     return verify_chv2 (app, pincb, pincb_arg);
 }
 
-static int
+static gpg_error_t
 do_with_keygrip (app_t app, ctrl_t ctrl, int action, const char *keygrip_str)
 {
   int i;
@@ -4925,14 +4925,12 @@ do_with_keygrip (app_t app, ctrl_t ctrl, int action, const char *keygrip_str)
   if (action == KEYGRIP_ACTION_LOOKUP)
     {
       if (keygrip_str == NULL)
-        return 1;
+        return gpg_error (GPG_ERR_NOT_FOUND);
 
       for (i = 0; i < 3; i++)
         if (app->app_local->pk[i].read_done
             && !strcmp (keygrip_str, app->app_local->pk[i].keygrip_str))
-          return 0;                     /* Found */
-
-      return 1;
+          return 0; /* Found */
     }
   else
     {
@@ -4941,7 +4939,7 @@ do_with_keygrip (app_t app, ctrl_t ctrl, int action, const char *keygrip_str)
       int data = (action == KEYGRIP_ACTION_SEND_DATA);
 
       if (DIM (buf) < 2 * app->serialnolen + 1)
-        return 0;
+        return gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
 
       bin2hex (app->serialno, app->serialnolen, buf);
 
@@ -4954,6 +4952,10 @@ do_with_keygrip (app_t app, ctrl_t ctrl, int action, const char *keygrip_str)
                 send_keyinfo (ctrl, data,
                               app->app_local->pk[i].keygrip_str,buf, idbuf);
               }
+          /* Return an error so that the dispatcher keeps on looping
+           * over the other applications.  Only for clarity we use a
+           * different error code than for the not_found case.  */
+          return gpg_error (GPG_ERR_TRUE);
         }
       else
         {
@@ -4966,9 +4968,9 @@ do_with_keygrip (app_t app, ctrl_t ctrl, int action, const char *keygrip_str)
                 return 0;
               }
         }
-
-      return 1;
     }
+
+  return gpg_error (GPG_ERR_NOT_FOUND);
 }
 
 /* Show information about card capabilities.  */

scd/app.c

@@ -1292,9 +1292,27 @@ app_send_card_list (ctrl_t ctrl)
 }
 
 /* Execute an action for each app.  ACTION can be one of:
-     KEYGRIP_ACTION_SEND_DATA: send data if KEYGRIP_STR matches
-     KEYGRIP_ACTION_WRITE_STATUS: write status if KEYGRIP_STR matches
-     KEYGRIP_ACTION_LOOKUP: Return matching APP
+ *
+ * - KEYGRIP_ACTION_SEND_DATA
+ *
+ *     If KEYGRIP_STR matches a public key of any active application
+ *     send information as LF terminated data lines about the public
+ *     key.  The format of these lines is
+ *         <keygrip> T <serialno> <idstr>
+ *     If a match was found a pointer to the matching application is
+ *     returned.  With the KEYGRIP_STR given as NULL, lines for all
+ *     keys will be send and the return value is NULL.
+ *
+ * - KEYGRIP_ACTION_WRITE_STATUS
+ *
+ *     Same as KEYGRIP_ACTION_SEND_DATA but uses status lines instead
+ *     of data lines.
+ *
+ * - KEYGRIP_ACTION_LOOKUP
+ *
+ *     Returns a pointer to the application matching KEYGRIP_STR but
+ *     does not emit any status or data lines.  If no key with that
+ *     keygrip is available or KEYGRIP_STR is NULL, NULL is returned.
  */
 app_t
 app_do_with_keygrip (ctrl_t ctrl, int action, const char *keygrip_str)