sexp: Avoid a fatal error in case of ENOMEM in called functions.

* src/sexp.c (do_vsexp_sscan): Replace BUG() by a proper error
return.  Replace sprintf by snprintf.
(convert_to_hex): Replace sprintf by snprintf.
(convert_to_string): Ditto.
(_gcry_sexp_sprint): Ditto.
--

_gcry_mpi_print can actually return ENOMEM because it inetrnally needs
to allocate temporary buffers.  Thus BUG was not the right thing to
do.  This was detected while investigating bug 3530.

Replacing sprintf by snprintf is not technically required but some
compilers print warnings for the use of sprintf.  So let's silence
them.

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

1 files changed, 15 insertions, 13 deletions

diff --git a/src/sexp.c b/src/sexp.c
index 6077bab9..0462d92e 100644
--- a/src/sexp.c
+++ b/src/sexp.c
@@ -1,7 +1,7 @@
 /* sexp.c  -  S-Expression handling
  * Copyright (C) 1999, 2000, 2001, 2002, 2003,
  *               2004, 2006, 2007, 2008, 2011  Free Software Foundation, Inc.
- * Copyright (C) 2013, 2014 g10 Code GmbH
+ * Copyright (C) 2013, 2014, 2017 g10 Code GmbH
  *
  * This file is part of Libgcrypt.
  *
@@ -15,9 +15,9 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ * SPDX-License-Identifier: LGPL-2.1+
  */
 
 
@@ -1429,8 +1429,9 @@ do_vsexp_sscan (gcry_sexp_t *retsexp, size_t *erroff,
                 }
               else
                 {
-                  if (_gcry_mpi_print (mpifmt, NULL, 0, &nm, m))
-                    BUG ();
+                  err = _gcry_mpi_print (mpifmt, NULL, 0, &nm, m);
+                  if (err)
+                    goto leave;
 
                   MAKE_SPACE (nm);
                   if (!_gcry_is_secure (c.sexp->d)
@@ -1456,8 +1457,9 @@ do_vsexp_sscan (gcry_sexp_t *retsexp, size_t *erroff,
 
                   *c.pos++ = ST_DATA;
                   STORE_LEN (c.pos, nm);
-                  if (_gcry_mpi_print (mpifmt, c.pos, nm, &nm, m))
-                    BUG ();
+                  err = _gcry_mpi_print (mpifmt, c.pos, nm, &nm, m);
+                  if (err)
+                    goto leave;
                   c.pos += nm;
                 }
 	    }
@@ -1521,7 +1523,7 @@ do_vsexp_sscan (gcry_sexp_t *retsexp, size_t *erroff,
 	      char buf[35];
 
 	      ARG_NEXT (aint, int);
-	      sprintf (buf, "%d", aint);
+	      snprintf (buf, sizeof buf, "%d", aint);
 	      alen = strlen (buf);
 	      MAKE_SPACE (alen);
 	      *c.pos++ = ST_DATA;
@@ -1537,7 +1539,7 @@ do_vsexp_sscan (gcry_sexp_t *retsexp, size_t *erroff,
 	      char buf[35];
 
 	      ARG_NEXT (aint, unsigned int);
-	      sprintf (buf, "%u", aint);
+	      snprintf (buf, sizeof buf, "%u", aint);
 	      alen = strlen (buf);
 	      MAKE_SPACE (alen);
 	      *c.pos++ = ST_DATA;
@@ -1810,7 +1812,7 @@ convert_to_hex (const unsigned char *src, size_t len, char *dest)
     {
       *dest++ = '#';
       for (i=0; i < len; i++, dest += 2 )
-        sprintf (dest, "%02X", src[i]);
+        snprintf (dest, 3, "%02X", src[i]);
       *dest++ = '#';
     }
   return len*2+2;
@@ -1839,7 +1841,7 @@ convert_to_string (const unsigned char *s, size_t len, char *dest)
             default:
               if ( (*s < 0x20 || (*s >= 0x7f && *s <= 0xa0)))
                 {
-                  sprintf (p, "\\x%02x", *s);
+                  snprintf (p, 5, "\\x%02x", *s);
                   p += 4;
                 }
               else
@@ -1999,7 +2001,7 @@ _gcry_sexp_sprint (const gcry_sexp_t list, int mode,
             }
           else
             {
-              sprintf (numbuf, "%u:", (unsigned int)n );
+              snprintf (numbuf, sizeof numbuf, "%u:", (unsigned int)n );
               len += strlen (numbuf) + n;
               if ( buffer )
                 {