alpine 3.8
race weakness #3

5

Weakness Breakdown


Definition:

A race condition exists when parallel code accesses shared data without proper coordination. An attack that uses a race-condition weakness takes advantage of the unsafe data access to manipulate how one of the parallel sections of code reacts. Even though each process runs as intended, the outcome is unexpected. For example, consider a bank service that depends on an encryption key that it reads from a known location. An independent cryptography service is responsible for generating the key and placing it where the bank is expected to read it in a timely manner. If the bank and cryptography services do not coordinate with each other, then the bank may read a blank encryption key before cryptography writes the key to the location. This can effectively turn off all encryption for the bank without either service, or the administrator, knowing that something has gone wrong.

Warning code(s):

This accepts filename arguments; if an attacker can move those files or change the link content, a race condition results. Also, it does not terminate with ASCII NUL..

File Name:

cogl/src/cogl-1.22.2/deps/glib/gfileutils.c

Context:

The highlighted line of code below is the trigger point of this particular Alpine 3.8 race weakness.

  *
 * Reads the contents of the symbolic link @filename like the POSIX
 * readlink() function.  The returned string is in the encoding used
 * for filenames. Use g_filename_to_utf8() to convert it to UTF-8.
 *
 * Returns: A newly-allocated string with the contents of the symbolic link, 
 *          or %NULL if an error occurred.
 *
 * Since: 2.4
 */
gchar *
g_file_read_link (const gchar  *filename,
	          GError      **error)
{
#ifdef HAVE_READLINK
  gchar *buffer;
  guint size;
  gint read_size;    
  
  size = 256; 
  buffer = g_malloc (size);
  
  while (TRUE) 
    {
      read_size = readlink (filename, buffer, size);
      if (read_size < 0) {
	int save_errno = errno;
	gchar *display_filename = g_filename_display_name (filename);

	g_free (buffer);
	g_set_error (error,
		     G_FILE_ERROR,
		     g_file_error_from_errno (save_errno),
		     _("Failed to read the symbolic link '%s': %s"),
		     display_filename, 
		     g_strerror (save_errno));
	g_free (display_filename);
	
	return NULL;
      }
    
      if (read_size < size) 
	{
	  buffer[read_size] = 0;
	  return buffer;
	}
      
      size *= 2;
      buffer = g_realloc (buffer, size);
    } 

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