[ SOURCE: http://www.secureroot.com/security/advisories/9735780620.html ] ****************************************************************************** the original writeup can be found at http://www.uberhax0r.net/~miah/swat along with all the code mentioned in this advisory ****************************************************************************** The program swat included in the samba distribution allows username and password bruteforcing. An attacker can easily generate userlists and then bruteforce their passwords. Comments in the source code show that somebody tried to prevent this from happening[1]. The problem occurs when a user types in the wrong password. If swat gets a valid username, but incorrect password it errors with: 2second pause 401 Authorization Required You must be authenticated to use this service. If swat gets a invalid username / password: NO PAUSE 401 Bad Authorization username/password must be supplied The following code is written by t12. It will generate a list of valid usernames and then brute force passwords for those usernames. It has been tested on freebsd. http://www.uberhax0r.net/~miah/swat/code/flyswatter.c Obviously, if the username/password are correct you get logged in. What makes this even worse is that swat does no logging. However; if logging[2] is enabled a temp race exists. Swat does not check for file existence before hand and it overwrites the file without regret. What makes this even worse is swat will log *any* input it gets into this log file. So for example we have local shell on a system running swat but want root we simply: ln -s /tmp/cgi.log /etc/passwd telnet localhost 901 --enter the following-- rootuser::0:0::/:/bin/bash --hang up the connection-- We now have the following entry in our /etc/passwd file: [Date: Mon, 23 Oct 2000 16:03:13 GMT localhost.localdomain (127.0.0.1)] rootuser::0:0::/:/bin/bash You could also use this shell script http://www.uberhax0r.net/~miah/swat/code/swat-exp.sh or if you want it in C http://www.uberhax0r.net/~miah/swat/code/swat-exp.c also precompiled for linux http://www.uberhax0r.net/~miah/swat/code/swat-exp.linux (code by optyx) You can also download a fixed cgi.c http://www.uberhax0r.net/~miah/swat/code/cgi.c.fixed (make your own damned diff) (fix by optyx) You can now su to that user. *NOTE* this will destroy the passwd file. Now you might be thinking "but if the /tmp/cgi.log exists, how can a user overwrite it with a symlink?". The answer: Why bother! The cgi.log file contains everything the users webbrowser sent back to it including their login/password. The Authorization: Basic entries have username:password encoded in base64 in them. Most of the time the swat administrator will login as root to do the changes to the smb.conf, so getting root is easy. You can run the gimme-login.sh script to get a list of logins from the cgi.log. Swat is also vulnerable to a DoS attack. Anybody can perform this. Simply login to swat with a improper username and password, but change the default url from "hostname:901" to somthing like "hostname:901?somerandomfile". Swat will error with "Authentication Required"(even with valid accounts) and inetd will restart it. Using netscape, netscape will retry to get the file and will eventually cause the inetd daemon to shutdown swat for 10 minutes (dependent on inetd configuration, this is tested on linux redhat 6.2) [1] In the cgi.c file the following entry exists: Line 349/367 /* * Always give the same error so a cracker * cannot tell why we fail. */ The person that wrote this code obviously didn't check their work to well. [2] Logging is enabled by changing samba-2.0.7/source/web/cgi.c's "#define CGI_LOGGING 0" to "#define CGI_LOGGING 1". Some systems may have this by default, otherwise its a tweak the sysadmin will most likely have to do. credit to miah for discovering everything and t12 and optyx for the code. ***************************************************************************** Uberhax0r Communications, putting bullets in mullets since '96