Bug 400921

Description of problem:
Thi is basically the re-edition on RHEL5 of bug# 241725.
when specifying the 'user_config_dir' directive in vsftpd.conf, vsftpd will fail
when there is no user config file in the specified directory.

Version-Release number of selected component (if applicable):
vsftpd-2.0.5-10.el5

How reproducible:
almost always (see description below)


Steps to Reproduce:
1. install vsftpd
2. add line to vsftpd.conf: user_config_dir=/etc/vsftpd/user_conf
3. login as a local or anonymous user without creating a config file for the user
  
Actual results:
500 OOPS: reading non-root config file

Expected results:
should be able to login even when user config file for a specific user doesn't 
exist (i.e. user config files should not be mandatory for all users when enabled)

Additional info:
touch a file in user_config_dir with the name of the ftp user to workaround this
issue
In twoprocess.c, we have the lines of code:
  retval = str_stat(&filename_str, &p_statbuf);
  /* Security - die unless owned by root */
  if (!vsf_sysutil_retval_is_error(retval) &&
      vsf_sysutil_statbuf_get_uid(p_statbuf) == VSFTP_ROOT_UID)
  {
    vsf_parseconf_load_file(str_getbuf(&filename_str), 1);
  }
  else if (vsf_sysutil_statbuf_get_uid(p_statbuf) != VSFTP_ROOT_UID)
  {
    die("reading non-root config file");
  }

If the file does not exist, the "else if" branch is taken and the test if
(vsf_sysutil_statbuf_get_uid(p_statbuf) != VSFTP_ROOT_UID) is performed. But
when the file does not exist, the whole structure pointed by p_statbuf has
uncertain content. I think that the value of retval should be again chacked, to
be sure that we're referring to a struct with valid data in it: comparing the
UID of a non-existent file is a nonsense.
When I make tests, most of the time ftp access fails, but sometimes it does not.
I think this is due to the fact that when the user config file does not exist,
p_statbuf points to random data, so sometimes the test yelds true.
I think that the above code should be something like (please review the code):

  retval = str_stat(&filename_str, &p_statbuf);
  /* Security - die unless owned by root */
  if (!vsf_sysutil_retval_is_error(retval))
  {
    if (vsf_sysutil_statbuf_get_uid(p_statbuf) == VSFTP_ROOT_UID)
    {
      vsf_parseconf_load_file(str_getbuf(&filename_str), 1);
    }
    else
    {
      die("reading non-root config file");
    }
  }