Add a platform function to return a random uint32_t

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>

include/mbedtls/platform_util.h

@@ -231,6 +231,18 @@ int mbedtls_platform_memmove( void *dst, const void *src, size_t num );
  */
 int mbedtls_platform_memcmp( const void *buf1, const void *buf2, size_t num );
 
+/**
+ * \brief       RNG-function for getting a random 32-bit integer.
+ *
+ *
+ * \note        Currently the function is dependent of hardware providing an
+ *              rng with MBEDTLS_ENTROPY_HARDWARE_ALT. By default, 0 is
+ *              returned.
+ *
+ * \return      The generated random number.
+ */
+uint32_t mbedtls_platform_random_uint32( void );
+
 /**
  * \brief       RNG-function for getting a random in given range.
  *

library/platform_util.c

@@ -172,6 +172,20 @@ int mbedtls_platform_memcmp( const void *buf1, const void *buf2, size_t num )
     return( (int) diff | (int) ( flow_counter ^ num ) );
 }
 
+uint32_t mbedtls_platform_random_uint32( )
+{
+#if !defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
+    return 0;
+#else
+    uint32_t result = 0;
+    size_t olen = 0;
+
+    mbedtls_hardware_poll( NULL, (unsigned char *) &result, sizeof( result ),
+                           &olen );
+    return( result );
+#endif
+}
+
 uint32_t mbedtls_platform_random_in_range( size_t num )
 {
 #if !defined(MBEDTLS_ENTROPY_HARDWARE_ALT)