gpg: Allow printing of MPI values in --list-mode.

* g10/parse-packet.c (set_packet_list_mode): Set mpi_print_mode.
* g10/misc.c (mpi_print): Do not print an extra leading zero.
--

This was in older versions possible using "--debug 4" but that was
disabled in 2.1 due to a conflict using this values also for
Libgcrypt.  Now the values are dumped either with --debug 4 or using
--list-packets along with --verbose.

Because OpenPGP only uses unsigned integers an extra leading zero will
not be printed anymore.

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

doc/gpg.texi

@@ -333,8 +333,9 @@ listed too.
 
 @item --list-packets
 @opindex list-packets
-List only the sequence of packets. This is mainly
-useful for debugging.
+List only the sequence of packets. This is mainly useful for
+debugging.  When used with option @option{--verbose} the actual MPI
+values are dumped and not only their lengths.
 
 
 @item --card-edit

g10/misc.c

@@ -1636,7 +1636,8 @@ pubkey_nbits( int algo, gcry_mpi_t *key )
 int
 mpi_print (estream_t fp, gcry_mpi_t a, int mode)
 {
-  int n=0;
+  int n = 0;
+  size_t nwritten;
 
   if (!a)
     return es_fprintf (fp, "[MPI_NULL]");
@@ -1654,19 +1655,19 @@ mpi_print (estream_t fp, gcry_mpi_t a, int mode)
         n += es_fprintf (fp, "[invalid opaque value]");
       else
         {
-          nbits = (nbits + 7)/8;
-          for (; nbits; nbits--, p++)
-            n += es_fprintf (fp, "%02X", *p);
+          if (!es_write_hexstring (fp, p, (nbits + 7)/8, 0, &nwritten))
+            n += nwritten;
         }
     }
   else
     {
       unsigned char *buffer;
+      size_t buflen;
 
-      if (gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buffer, NULL, a))
+      if (gcry_mpi_aprint (GCRYMPI_FMT_USG, &buffer, &buflen, a))
         BUG ();
-      es_fputs (buffer, fp);
-      n += strlen (buffer);
+      if (!es_write_hexstring (fp, buffer, buflen, 0, &nwritten))
+        n += nwritten;
       gcry_free (buffer);
     }
   return n;

g10/parse-packet.c

@@ -112,7 +112,7 @@ read_32 (IOBUF inp)
 /* Read an external representation of an mpi and return the MPI.  The
  * external format is a 16 bit unsigned value stored in network byte
  * order, giving the number of bits for the following integer. The
- * integer is stored with MSB first (left padded with zeroes to align
+ * integer is stored with MSB first (left padded with zero bits to align
  * on a byte boundary).  */
 static gcry_mpi_t
 mpi_read (iobuf_t inp, unsigned int *ret_nread, int secure)
@@ -177,24 +177,38 @@ set_packet_list_mode (int mode)
 {
   int old = list_mode;
   list_mode = mode;
-  /* FIXME(gcrypt) mpi_print_mode = DBG_MPI; */
-  /* We use stdout print only if invoked by the --list-packets command
+
+  /* We use stdout only if invoked by the --list-packets command
      but switch to stderr in all other cases.  This breaks the
      previous behaviour but that seems to be more of a bug than
      intentional.  I don't believe that any application makes use of
      this long standing annoying way of printing to stdout except when
      doing a --list-packets. If this assumption fails, it will be easy
      to add an option for the listing stream.  Note that we initialize
-     it only once; mainly because some code may switch the option
-     value later back to 1 and we want to have all output to the same
-     stream.
+     it only once; mainly because there is code which switches
+     opt.list_mode back to 1 and we want to have all output to the
+     same stream.  The MPI_PRINT_MODE will be enabled if the
+     corresponding debug flag is set or if we are in --list-packets
+     and --verbose is given.
 
      Using stderr is not actually very clean because it bypasses the
      logging code but it is a special thing anyway.  I am not sure
      whether using log_stream() would be better.  Perhaps we should
-     enable the list mdoe only with a special option. */
+     enable the list mode only with a special option. */
   if (!listfp)
-    listfp = opt.list_packets == 2 ? es_stdout : es_stderr;
+    {
+      if (opt.list_packets == 2)
+        {
+          listfp = es_stdout;
+          if (opt.verbose)
+            mpi_print_mode = 1;
+        }
+      else
+        listfp = es_stderr;
+
+      if (opt.debug && DBG_MPI_VALUE)
+        mpi_print_mode = 1;
+    }
   return old;
 }