Add initial options and support for parameter validation

This function adds the additional config.h option of MBEDTLS_CHECK_PARAMS which
allows additional validation of parameters passed to the library.

include/mbedtls/config.h

@@ -256,6 +256,25 @@
  */
 //#define MBEDTLS_DEPRECATED_REMOVED
 
+/**
+ * \def MBEDTLS_CHECK_PARAMS
+ *
+ * This configuration controls whether the library validates parameters passed
+ * to it.
+ *
+ * Application code that deals with 3rd party input may wish to enable such
+ * validation, whilst code on closed systems, such as embedded systems, where
+ * the input is controlled and predictable, may wish to disable it entirely to
+ * reduce the code size of the library.
+ *
+ * When the symbol is not defined, no parameter validation except that required
+ * to ensure the integrity or security of the library are performed.
+ *
+ * When the symbol is defined, all parameters will be validated, and an error
+ * code returned where appropriate.
+ */
+#define MBEDTLS_CHECK_PARAMS
+
 /* \} name SECTION: System support */
 
 /**
@@ -2996,6 +3015,9 @@
 //#define MBEDTLS_PLATFORM_NV_SEED_READ_MACRO   mbedtls_platform_std_nv_seed_read /**< Default nv_seed_read function to use, can be undefined */
 //#define MBEDTLS_PLATFORM_NV_SEED_WRITE_MACRO  mbedtls_platform_std_nv_seed_write /**< Default nv_seed_write function to use, can be undefined */
 
+//#define MBEDTLS_PARAM_FAILED(x)               mbedtls_param_failed( #x ) /**< Default parameter validation callback to use. Can be undefined */
+
+
 /* SSL Cache options */
 //#define MBEDTLS_SSL_CACHE_DEFAULT_TIMEOUT       86400 /**< 1 day  */
 //#define MBEDTLS_SSL_CACHE_DEFAULT_MAX_ENTRIES      50 /**< Maximum entries in cache */

include/mbedtls/platform_util.h

@@ -41,6 +41,34 @@
 extern "C" {
 #endif
 
+#if defined( MBEDTLS_CHECK_PARAMS ) && defined(MBEDTLS_PLATFORM_C) && \
+    !defined(MBEDTLS_PARAM_FAILED)
+#define MBEDTLS_PARAM_FAILED( cond, file, line )                               \
+                                        mbedtls_param_failed( cond, file, line )
+
+/**
+ * \brief       User supplied callback function for parameter validation failure.
+ *
+ *              When the MBEDTLS_CHECK_PARAMS option is enabled, the library
+ *              provides additional validation of all input parameters to
+ *              confirm that they conform to what the interface can accept.
+ *              For example - NULL paramater checks.
+ *
+ *              These checks are designed to check programmatic issues in the
+ *              application software using Mbed TLS, or catch other runtime
+ *              errors which may be due to issues in the application software.
+ *
+ *              This function will be called unless an alternative function is
+ *              defined through the MBEDTLS_PARAM_FAILURE function.
+ *
+ *              This function can return, and the operation will be aborted, or
+ *              alternatively, through use of setjmp()/longjmp() can resume
+ *              execution in the application code.
+ */
+void mbedtls_param_failed( char* failure_condition, char* file, int line );
+
+#endif /* MBEDTLS_CHECK_PARAMS && MBEDTLS_PLATFORM_C && !MBEDTLS_PARAM_FAILED */
+
 /**
  * \brief       Securely zeroize a buffer
  *

library/platform_util.c

@@ -35,6 +35,7 @@
 #endif
 
 #include "mbedtls/platform_util.h"
+#include "mbedtls/platform.h"
 #include "mbedtls/threading.h"
 
 #include <stddef.h>
@@ -133,3 +134,11 @@ struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt,
 #endif /* _WIN32 && !EFIX64 && !EFI32 */
 }
 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
+
+#if defined( MBEDTLS_CHECK_PARAMS ) && defined(MBEDTLS_PLATFORM_C) && \
+    defined(MBEDTLS_DEBUG_INVALID_PARAMS)
+void mbedtls_param_failed( char* failure_condition )
+{
+    mbedtls_printf("%s:%i: Input param failed - %s\n", __FILE__, __LINE__,                           failure_condition );
+}
+#endif