[Nagiosplug-devel] check_http, redirects and expect

[Lamprecht, Andreas]

Helo!
We recently ran into problems with check_http.
One of our checked webapps redirects to another website and that redirected page sends back a stupid, but correct result code of 494.

The command we run looks ike this:

  check_http -p 8080 -c 30 -I ServerIP -u "URL" -f follow -e '302,494'

However, the check always returns OK, even if the redirected page returns a different error code.
It seems check_http is not following redirects when "-e" is used.
This is because of that "if" statement in line 996 . This completely disables the checking for a possible redirection.

    994   /* Bypass normal status line check if server_expect was set by user and not default */
    995   /* NOTE: After this if/else block msg *MUST* be an asprintf-allocated string */
    996   if ( server_expect_yn )  {
    997     asprintf (&msg,
    998               _("Status line output matched \"%s\" - "), server_expect);
    999     if (verbose)
   1000       printf ("%s\n",msg);
   1001   }
   1002   else {
   ....
   1028     /* check redirected page if specified */
   1029     else if (http_status >= 300) {
   1030
   1031       if (onredirect == STATE_DEPENDENT)
   1032         redir (header, status_line);
   1033       else
   1034         result = max_state_alt(onredirect, result);
   1035       asprintf (&msg, _("%s - "), status_line);
   1036     } /* end if (http_status >= 300) */
   1037     else {

i could "fix" this behaviour by simply disabling the "if" in line 996 by adding a " && 0" to the if:

     996   if ( server_expect_yn   && 0 )  {

That works for the moment, but now check_http finishes with a WARNING state because the status-code is greater than 400.

To fix this, too, i had to change the stauts-code logic to include a check for the expected status code. And since this resulted into a segfault, i had to extend the "if" even further.
The result is this:

   1006     /* server errors result in a critical state */
   1007     else if (http_status >= 500 && http_status < 600 && ! expected_statuscode (status_line, server_expect) ) {
   1008         asprintf (&msg, _("%s - "), status_line);
   1009         result = STATE_CRITICAL;
   1010     }
   1011     /* client errors result in a warning state */
   1012     else if (http_status >= 400 && http_status < 500 && ! expected_statuscode (status_line, server_expect) ) {
   1013         asprintf (&msg, _("%s - "), status_line);
   1014         result = max_state_alt(STATE_WARNING, result);
   1015     }
   1016     /* check redirected page if specified */
   1017     else if (http_status >= 300 && http_status < 400 ) {


This seems to work now.

I am sure that could be done in a more elegant way and i am willing to invest more time in coding a better fix but first of all i would like to check with you guys if such a change in the behaviour of check_http would be acceptable.

Greetings
Andreas Lamprecht
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