scd:p15: Read certificates in extended mode.

* scd/app-p15.c (readcert_by_cdf): Allow reading in extended mode.
* scd/app-common.h (app_get_slot): New.
--

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

(Back ported from master)

Added app_get_slot.

scd/app-common.h

@@ -119,6 +119,19 @@ struct app_ctx_s {
   } fnc;
 };
 
+
+/* Helper to get the slot from an APP object. */
+static inline int
+app_get_slot (app_t app)
+{
+  /* Note that this is a similar function of the one in 2.3 which we
+   * use to make back porting easier.  */
+  if (app)
+    return app->slot;
+  return -1;
+}
+
+
 /*-- app-help.c --*/
 unsigned int app_help_count_bits (const unsigned char *a, size_t len);
 gpg_error_t app_help_get_keygrip_string (ksba_cert_t cert, char *hexkeygrip);

scd/app-p15.c

@@ -659,6 +659,8 @@ read_ef_odf (app_t app, unsigned short odf_fid)
               app->app_local->home_df = home_df;
               log_info ("p15: application directory detected as 0x%04hX\n",
                         home_df);
+              /* We assume that direct path selection is possible.  */
+              app->app_local->direct_path_selection = 1;
             }
 
           /* We only allow a full path if all files are at the same
@@ -2713,7 +2715,8 @@ readcert_by_cdf (app_t app, cdf_object_t cdf,
   if (err)
     goto leave;
 
-  err = iso7816_read_binary (app->slot, cdf->off, cdf->len, &buffer, &buflen);
+  err = iso7816_read_binary_ext (app_get_slot (app), 1, cdf->off, cdf->len,
+                                 &buffer, &buflen);
   if (!err && (!buflen || *buffer == 0xff))
     err = gpg_error (GPG_ERR_NOT_FOUND);
   if (err)