[libmicrohttpd] [SSL-Example] load_file(), terminate c-string with a null-character?

[Weber, Peter (Wilken Software Engineering GmbH)]

Hello!

I've used the example code from the PDF-Tutorial[1] and from the
website [2] to build the foundation for the application im currently
developing. Finally Valgrind reported an error "Invalid read of size 1"
(valgrind --leak-check=yes ./yourapplication).

Maybe I'm wrong. I think the returned C-String should be terminated by
the famous Null-Character, and therefore we also need to extend the
allocated buffer from the heap by one byte.

Original-Code:
-----------------------------------------------------------------------
static char *
load_file (const char *filename)
{
  FILE *fp;
  char *buffer;
  long size;

  size = get_file_size (filename);
  if (size == 0)
    return NULL;

  fp = fopen (filename, "rb");
  if (!fp)
    return NULL;

  buffer = malloc (size);
  if (!buffer)
    {
      fclose (fp);
      return NULL;
    }

  if (size != fread (buffer, 1, size, fp))
    {
      free (buffer);
      buffer = NULL;
    }

  fclose (fp);
  return buffer;
}
-----------------------------------------------------------------------
Patch:
-----------------------------------------------------------------------
--- load_file.c 2016-08-24 14:27:51.871565051 +0200
+++ new_load_file.c     2016-08-24 14:29:33.441565410 +0200
@@ -13,7 +13,7 @@
   if (!fp)
     return NULL;
 
-  buffer = malloc (size);
+  buffer = malloc (size + 1);
   if (!buffer)
     {
       fclose (fp);
@@ -26,6 +26,8 @@
       buffer = NULL;
     }
 
+  // null-termination of c-string
+  buffer[size] = '\0';
   fclose (fp);
   return buffer;
 }
-----------------------------------------------------------------------



Thanks for your patience with me.
Peter

[1]https://www.gnu.org/software/libmicrohttpd/tutorial.pdf
[2]https://www.gnu.org/software/libmicrohttpd/tutorial.html#tlsauthenti
cation_002ec