Use a harder to optimize out memset().

diff --git a/lib/Makefile.am b/lib/Makefile.am
index 817db30488bf352ad84882cdb33d3ce4111722a4..e39c7c45bf3ea3c77c42f5c3c7ab4aa266292b1a 100644 (file)
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -81,7 +81,8 @@ COBJECTS = gnutls_range.c gnutls_record.c \
        gnutls_rsa_export.c gnutls_helper.c gnutls_supplemental.c       \
        random.c crypto-api.c gnutls_privkey.c gnutls_pcert.c           \
        gnutls_pubkey.c locks.c gnutls_dtls.c system_override.c \
-       crypto-backend.c verify-tofu.c pin.c tpm.c fips.c
+       crypto-backend.c verify-tofu.c pin.c tpm.c fips.c \
+       safe-memset.c
 
 if ENABLE_SELF_CHECKS
 COBJECTS += crypto-selftests.c crypto-selftests-pk.c
@@ -109,7 +110,7 @@ HFILES = abstract_int.h debug.h gnutls_compress.h gnutls_cipher.h   \
        gnutls_srp.h auth/srp.h auth/srp_passwd.h       \
        gnutls_helper.h gnutls_supplemental.h crypto.h random.h system.h\
        locks.h gnutls_mbuffers.h gnutls_ecc.h pin.h fips.h \
-       priority_options.h
+       priority_options.h safe-memset.h
 
 if ENABLE_PKCS11
 HFILES += pkcs11_int.h

diff --git a/lib/gnutls_mem.c b/lib/gnutls_mem.c
index 01638745c3642b91f2e16814569a7a6f16e9c656..b82c392bbf538e9508a762ac35e47b829e18b37b 100644 (file)
--- a/lib/gnutls_mem.c
+++ b/lib/gnutls_mem.c
@@ -82,16 +82,6 @@ char *_gnutls_strdup(const char *str)
        return ret;
 }
 
-void _gnutls_bzero(void *mem, size_t size)
-{
-       /* The reason we use that function instead of directly
-        * calling memset is to prevent the compiler
-        * optimizing out certain calls that may look
-        * pointless to him, but needed to erase
-        * private keys. */
-       memset(mem, 0, size);
-}
-
 #if 0
 /* don't use them. They are included for documentation.
  */

diff --git a/lib/gnutls_mem.h b/lib/gnutls_mem.h
index 2dc4200a35511e21ebe834053f51a108dfaf05ca..1f1da609cdcdbbb5156db082d6db72a4b985d2fb 100644 (file)
--- a/lib/gnutls_mem.h
+++ b/lib/gnutls_mem.h
@@ -37,14 +37,14 @@ svoid *gnutls_secure_calloc(size_t nmemb, size_t size);
 void *_gnutls_calloc(size_t nmemb, size_t size);
 char *_gnutls_strdup(const char *);
 
-void _gnutls_bzero(void *v, size_t n);
-
 #define zrelease_mpi_key(mpi) if (*mpi!=NULL) { \
                 _gnutls_mpi_clear(*mpi); \
                 _gnutls_mpi_release(mpi); \
         }
 
-#define zeroize_key(x, size) _gnutls_bzero(x, size)
+void _gnutls_safe_memset(void *data, int c, size_t size);
+
+#define zeroize_key(x, size) _gnutls_safe_memset(x, 0, size)
 
 #define zeroize_temp_key zeroize_key
 #define zrelease_temp_mpi_key zrelease_mpi_key

diff --git a/lib/safe-memset.c b/lib/safe-memset.c
new file mode 100644 (file)
index 0000000..2cf2cb8
--- /dev/null
+++ b/lib/safe-memset.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2014 Red Hat
+ *
+ * This file is part of GnuTLS.
+ *
+ * The GnuTLS is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This 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
+ * 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, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+#ifdef TEST_SAFE_MEMSET
+# include <string.h>
+#else
+# include <gnutls_int.h>
+#endif
+
+/* This is based on a nice trick for safe memset,
+ * sent by David Jacobson in the openssl-dev mailing list.
+ */
+
+void _gnutls_safe_memset(void *data, int c, size_t size)
+{
+       volatile unsigned volatile_zero = 0;
+       volatile char *vdata = (volatile char*)data;
+
+       do {
+               memset(data, c, size);
+       } while(vdata[volatile_zero] != c);
+}
+
+#ifdef TEST_SAFE_MEMSET
+int main()
+{
+       char x[64];
+
+       safe_memset(x, 0, sizeof(x));
+
+       return 0;
+
+}
+
+#endif