In August 2003, I wrote a tool called asleap for Linux systems to exploit a weakness in the Cisco LEAP authentication protocol. Using this tool, an attacker can actively compromise Cisco LEAP networks by mounting an offline dictionary attack against weak user passwords. In my testing, I was able to search through large dictionary files very quickly for user passwords (~45 million passwords per second on meager hardware.)
A quick summary of asleap features are as follows:
+ Can read live from any wireless interface in RFMON mode with libpcap. + Can monitor a single channel, or perform channel hopping to look for target networks running LEAP. + Will actively deauthenticate users on LEAP networks, forcing them to reauthenticate. This makes the capture of LEAP passwords very fast. + Will only deauth users who have not already been seen, doesn't waste time on users who are not running LEAP. + Can read from stored libpcap files, or AiroPeek NX files (1.X or 2.X files). + Uses a dynamic database table and index to make lookups on large files very fast. Reduces the worst-case search time to .0015% as opposed to lookups in a flat file. + Can write *just* the LEAP exchange information to a libpcap file. This could be used to capture LEAP credentials with a device short on disk space (like an iPaq), and then process the LEAP credentials stored in the libpcap file on a system with more storage resources to mount the dictionary attack.
Upon advising the Cisco PSIRT team, I was asked to wait for six months until February 2004 before making the tool publicly available. In the end of January 2004, Cisco PSIRT asked me to wait another few months while they finished testing the EAP-FAST protocol, the designated replacement for the flawed LEAP protocol.
After working out a release date with Cisco, I am making the source for asleap v1.0 available including a partial-functionality Win32 port. I encourage LEAP users to install and use asleap to evaluate the risks of using LEAP as a mechanism to protect the security of wireless networks.
Windows users can use third-party wireless sniffer tools including AiroPeek NX to capture the LEAP authentication exchange to test the security of LEAP user passwords.
The source and Win32 binary distribution are available at http://asleap.sourceforge.net, along with documentation and a user-support mailing list. I welcome your comments, suggestions or bug reports.
-Josh -- -Joshua Wright jwright@hasborg.com http://home.jwu.edu/jwright/
pgpkey: http://home.jwu.edu/jwright/pgpkey.htm fingerprint: FDA5 12FC F391 3740 E0AE BDB6 8FE2 FC0A D44B 4A73
