prevent memset() from being optimized out.

2 files changed, 18 insertions, 2 deletions

diff --git a/lib/gstr.h b/lib/gstr.h
index 51db059..34e8153 100644
--- a/lib/gstr.h
+++ b/lib/gstr.h
@@ -25,3 +25,18 @@ void _asn1_str_cat (char *dest, size_t dest_tot_size, const char *src);
 
 #define Estrcpy(x,y) _asn1_str_cpy(x,ASN1_MAX_ERROR_DESCRIPTION_SIZE,y)
 #define Estrcat(x,y) _asn1_str_cat(x,ASN1_MAX_ERROR_DESCRIPTION_SIZE,y)
+
+inline static
+void safe_memset(void *data, int c, size_t size)
+{
+	volatile unsigned volatile_zero = 0;
+	volatile char *vdata = (volatile char*)data;
+
+	/* This is based on a nice trick for safe memset,
+	 * sent by David Jacobson in the openssl-dev mailing list.
+	 */
+
+	do {
+		memset(data, c, size);
+	} while(vdata[volatile_zero] != c);
+}
diff --git a/lib/parser_aux.c b/lib/parser_aux.c
index b5f665d..6b34512 100644
--- a/lib/parser_aux.c
+++ b/lib/parser_aux.c
@@ -458,8 +458,9 @@ _asn1_remove_node (asn1_node node, unsigned int flags)
   if (node == NULL)
     return;
 
-  if (flags & ASN1_DELETE_FLAG_ZEROIZE)
-    memset(node->value, 0, node->value_len);
+  if (flags & ASN1_DELETE_FLAG_ZEROIZE && node->value) {
+    safe_memset(node->value, 0, node->value_len);
+  }
 
   if (node->value != NULL && node->value != node->small_value)
     free (node->value);