Add ForceZero for wolfSSL < 5.8.4

Author: LinuxJedi

src/internal.c

@@ -102,6 +102,17 @@
     #error "wolfTPM and MAXQ10XX are incompatible with each other."
 #endif
 
+/* wc_ForceZero was added in wolfSSL 5.8.4. Provide a fallback for older
+ * versions to securely zero sensitive memory. */
+#if defined(LIBWOLFSSL_VERSION_HEX) && LIBWOLFSSL_VERSION_HEX >= 0x05008004
+    #include <wolfssl/wolfcrypt/memory.h>
+#else
+    static void wc_ForceZero(void* mem, size_t len) {
+        volatile byte* p = (volatile byte*)mem;
+        while (len--) *p++ = 0;
+    }
+#endif
+
 /* Helper to get size of struct field */
 #define FIELD_SIZE(type, field) (sizeof(((type *)0)->field))