Use explicit_bzero to clear GnuTLS keys

* admin/merge-gnulib (GNULIB_MODULES): Add explicit_bzero.
* lib/explicit_bzero.c, m4/explicit_bzero.m4: New files.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/gnutls.c (clear_storage): New function.
(gnutls_symmetric_aead): Use it instead of memset.

1 files changed, 48 insertions, 0 deletions

diff --git a/lib/explicit_bzero.c b/lib/explicit_bzero.c
new file mode 100644
index 00000000000..262c68f9cd6
--- /dev/null
+++ b/lib/explicit_bzero.c
@@ -0,0 +1,48 @@
+/* Erasure of sensitive data, generic implementation.
+   Copyright (C) 2016-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* An assembler implementation of explicit_bzero can be created as an
+   assembler alias of an optimized bzero implementation.
+   Architecture-specific implementations also need to define
+   __explicit_bzero_chk.  */
+
+#if !_LIBC
+# include <config.h>
+#endif
+
+#include <string.h>
+
+/* glibc-internal users use __explicit_bzero_chk, and explicit_bzero
+   redirects to that.  */
+#undef explicit_bzero
+
+/* Set LEN bytes of S to 0.  The compiler will not delete a call to
+   this function, even if S is dead after the call.  */
+void
+explicit_bzero (void *s, size_t len)
+{
+#ifdef HAVE_EXPLICIT_MEMSET
+  explicit_memset (s, 0, len);
+#else
+  memset (s, '\0', len);
+# ifdef __GNUC__
+  /* Compiler barrier.  */
+  asm volatile ("" ::: "memory");
+# endif
+#endif
+}