Prevent false positive CF Test Failures

Marked dirty memory ends up in the result buffer after encoding (due to
the input having been marked dirty), and then the final comparison
to make sure that we got what we expected was triggering the constant
flow checker.

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/tests/suites/test_suite_base64.function b/tests/suites/test_suite_base64.function
index ec10033..be9b6e8 100644
--- a/tests/suites/test_suite_base64.function
+++ b/tests/suites/test_suite_base64.function
@@ -26,6 +26,10 @@
     TEST_ASSERT( mbedtls_base64_encode( dst_str, dst_buf_size, &len, src_str, src_len) == result );
     TEST_CF_PUBLIC( src_str, sizeof( src_str ) );
 
+    /* dest_str will have had tainted data copied to it, prevent the TEST_ASSERT below from triggering
+       CF failures by unmarking it. */
+    TEST_CF_PUBLIC( dst_str, len );
+
     if( result == 0 )
     {
         TEST_ASSERT( strcmp( (char *) dst_str, dst_string ) == 0 );
@@ -67,6 +71,10 @@
     TEST_ASSERT( mbedtls_base64_encode( res, dst_buf_size, &len, src->x, src->len ) == result );
     TEST_CF_PUBLIC( src->x, src->len );
 
+    /* res will have had tainted data copied to it, prevent the TEST_ASSERT below from triggering
+       CF failures by unmarking it. */
+    TEST_CF_PUBLIC( res, len );
+
     if( result == 0 )
     {
         TEST_ASSERT( len == strlen( dst ) );