Add OPENSSL_cleanse() to help cleanse memory and avoid certain compiler
and linker optimizations.
PR: 343

crypto/mem.c

diff --git a/crypto/mem.c b/crypto/mem.c
index 03d2569..46a0069 100644
--- a/crypto/mem.c
+++ b/crypto/mem.c
@@ -250,6 +250,7 @@
 void *CRYPTO_malloc_locked(int num, const char *file, int line)
 	{
 	void *ret = NULL;
+	extern unsigned char cleanse_ctr;
 
 	allow_customize = 0;
 	if (malloc_debug_func != NULL)
@@ -264,6 +265,12 @@
 	if (malloc_debug_func != NULL)
 		malloc_debug_func(ret, num, file, line, 1);
 
+        /* Create a dependency on the value of 'cleanse_ctr' so our memory
+         * sanitisation function can't be optimised out. NB: We only do
+         * this for >2Kb so the overhead doesn't bother us. */
+        if(ret && (num > 2048))
+		((unsigned char *)ret)[0] = cleanse_ctr;
+
 	return ret;
 	}
 
@@ -282,6 +289,7 @@
 void *CRYPTO_malloc(int num, const char *file, int line)
 	{
 	void *ret = NULL;
+	extern unsigned char cleanse_ctr;
 
 	allow_customize = 0;
 	if (malloc_debug_func != NULL)
@@ -296,6 +304,12 @@
 	if (malloc_debug_func != NULL)
 		malloc_debug_func(ret, num, file, line, 1);
 
+        /* Create a dependency on the value of 'cleanse_ctr' so our memory
+         * sanitisation function can't be optimised out. NB: We only do
+         * this for >2Kb so the overhead doesn't bother us. */
+        if(ret && (num > 2048))
+                ((unsigned char *)ret)[0] = cleanse_ctr;
+
 	return ret;
 	}