full-disclosure - Cross-Site Scripting vulnerability in Nagios

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Date: Thu, 10 Mar 2011 18:50:05 +0100
From: "sschurtz@...nline.de" <sschurtz@...nline.de>
To: full-disclosure@...ts.grok.org.uk
Subject: Cross-Site Scripting vulnerability in Nagios

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Advisory:           Cross-Site Scripting vulnerability in Nagios
Advisory ID:        SSCHADV2011-002
Author:             Stefan Schurtz
Affected Software:  Successfully tested on: nagios-3.2.0 / nagios-3.2.3
Vendor URL:         http://www.nagios.org
Vendor Status:      0000207: Cross-Site Scripting vulnerability in Nagios
CVE-ID:             -

==========================
Vulnerability Description:
==========================

This is Cross-Site Scripting vulnerability

JavaScript can be included in style sheets by using "expression()" (IE only)

==================
Technical Details:
==================

The function "strip_html_brackets" strip > and < from string but it's
not enough to prevent XSS attacks in "statusmap.cgi&layer="

http://site/nagios/cgi-bin/statusmap.cgi?layer='
style=xss:expression(alert('XSS')) '
http://site/nagios/cgi-bin/statusmap.cgi?layer='
onmouseover="alert('XSS')" '

- -----------
cgiutils.c
- -----------

/* strip > and < from string */

void strip_html_brackets(char *buffer){
        register int x;
        register int y;
        register int z;

        if(buffer==NULL || buffer[0]=='\x0')
                return;

        /* remove all occurances in string */
        z=(int)strlen(buffer);
        for(x=0,y=0;x<z;x++){
                if(buffer[x]=='<' || buffer[x]=='>')
                        continue;
                buffer[y++]=buffer[x];
                }
        buffer[y++]='\x0';

        return;
        }

- -----------
statusmap.c
- -----------

/* we found the layer argument */
         else if(!strcmp(variables[x],"layer")){
                x++;
                if(variables[x]==NULL){
                      error=TRUE;
                      break;
                }

                strip_html_brackets(variables[x]);
                add_layer(variables[x]);
                }

- -----------
Problem in "statusmap.c"
- -----------

/* print layer url info */
void print_layer_url(int get_method){
        layer *temp_layer;


for(temp_layer=layer_list;temp_layer!=NULL;temp_layer=temp_layer->next){
                if(get_method==TRUE)
                        printf("&layer=%s",temp_layer->layer_name); <--
no "escape_string"
                else
                        printf("<input type='hidden' name='layer'
value='%s'>\n",escape_string(temp_layer->layer_name));
                }

=========
Solution:
=========

if(get_method==TRUE)
          /* printf("&layer=%s",temp_layer->layer_name); */
          printf("&layer=%s",escape_string(temp_layer->layer_name));

====================
Disclosure Timeline:
====================

09-Mar-2011 - informed developers
09-Mar-2011 - post on Nagios Tracker -
http://tracker.nagios.org/view.php?id=207
09-Mar-2011 - Release date of this security advisory
10-Mar-2011 - post on BugTraq -
http://www.securityfocus.com/archive/1/516934/30/0/threaded

========
Credits:
========

Vulnerability found and advisory written by Stefan Schurtz.

===========
References:
===========

http://www.nagios.org
http://www.rul3z.de/advisories/SSCHADV2011-002.txt
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