scd: PC/SC reader selection by partial string match.

* scd/apdu.c (open_pcsc_reader_direct): Partial string match.
* scd/pcsc-wrapper.c (handle_open): Likewise.

--

(backport from 2.1 commit 01a2a61bc4)

The card reader name by PC/SC service might include USB bus,
which varies (on some platform like GNU/Linux).  Thus, it's
better to match partial string.

Original patch was submitted by anstein.  I changed it to fallback to
the first reader if no match found.

GnuPG-bug-id: 1618, 1930

scd/apdu.c

@@ -1870,7 +1870,8 @@ open_pcsc_reader_direct (const char *portstr)
   long err;
   int slot;
   char *list = NULL;
-  pcsc_dword_t nreader, listlen;
+  char *rdrname = NULL;
+  pcsc_dword_t nreader;
   char *p;
 
   slot = new_reader_slot ();
@@ -1917,24 +1918,27 @@ open_pcsc_reader_direct (const char *portstr)
       return -1;
     }
 
-  listlen = nreader;
   p = list;
   while (nreader)
     {
       if (!*p && !p[1])
         break;
-      if (*p)
-        log_info ("detected reader `%s'\n", p);
+      log_info ("detected reader `%s'\n", p);
       if (nreader < (strlen (p)+1))
         {
           log_error ("invalid response from pcsc_list_readers\n");
           break;
         }
+      if (!rdrname && portstr && !strncmp (p, portstr, strlen (portstr)))
+        rdrname = p;
       nreader -= strlen (p)+1;
       p += strlen (p) + 1;
     }
 
-  reader_table[slot].rdrname = xtrymalloc (strlen (portstr? portstr : list)+1);
+  if (!rdrname)
+    rdrname = list;
+
+  reader_table[slot].rdrname = xtrystrdup (rdrname);
   if (!reader_table[slot].rdrname)
     {
       log_error ("error allocating memory for reader name\n");
@@ -1943,7 +1947,6 @@ open_pcsc_reader_direct (const char *portstr)
       unlock_slot (slot);
       return -1;
     }
-  strcpy (reader_table[slot].rdrname, portstr? portstr : list);
   xfree (list);
   list = NULL;
 

scd/pcsc-wrapper.c

@@ -406,8 +406,9 @@ static void
 handle_open (unsigned char *argbuf, size_t arglen)
 {
   long err;
-  const char * portstr;
+  const char *portstr;
   char *list = NULL;
+  char *rdrname = NULL;
   pcsc_dword_t nreader, atrlen;
   char *p;
   pcsc_dword_t card_state, card_protocol;
@@ -416,7 +417,10 @@ handle_open (unsigned char *argbuf, size_t arglen)
   /* Make sure there is only the port string */
   if (arglen != strlen ((char*)argbuf))
     bad_request ("OPEN");
-  portstr = (char*)argbuf;
+  if (arglen == 0)
+    portstr = NULL;
+  else
+    portstr = (char*)argbuf;
 
   if (driver_is_open)
     {
@@ -466,17 +470,21 @@ handle_open (unsigned char *argbuf, size_t arglen)
           fprintf (stderr, PGM": invalid response from pcsc_list_readers\n");
           break;
         }
+      if (!rdrname && portstr && !strncmp (p, portstr, strlen (portstr)))
+        rdrname = p;
       nreader -= strlen (p)+1;
       p += strlen (p) + 1;
     }
 
-  current_rdrname = malloc (strlen (portstr && *portstr? portstr:list)+1);
+  if (!rdrname)
+    rdrname = list;
+
+  current_rdrname = strdup (rdrname);
   if (!current_rdrname)
     {
       fprintf (stderr, PGM": error allocating memory for reader name\n");
       exit (1);
     }
-  strcpy (current_rdrname, portstr && *portstr? portstr:list);
   free (list);
 
   err = pcsc_connect (pcsc_context,