It fixes a bunch of bugs and compile errors, introduces a few minor new features, has some code clean ups, etc. etc.
vsftpd-2.1.0 is interesting from a security perspective because of its changes to SSL support. It actual contains a reasonable resolution to the connection theft attack I blogged about here:
In the linked advisory I said "I have a crazy idea to use the SSL session cache as a cheezy form of authentication". Well, thanks to investigation by Tim Kosse of FileZilla fame, it turns out this is a very feasible option. Better still, a large number of clients already (whether they know it or not) use SSL session reuse between the control and data connection. This includes up to date versions of FileZilla, lftp and command line ftp-ssl. Therefore, vsftpd now defaults to requiring SSL session reuse. If your SSL FTP client does not re-use sessions, you can turn this off but you would do better to change FTP clients. Tim's FileZilla seems like a pretty awesome option to me. Hopefully other FTP servers will follow suit (quick source code scanning of popular open source ones seemed to lack a call to the relevant
Other new security features are:
- A per-process memory map limit of 100Mb. Just because it was easy, really. Note however!!! A memory leak in a session-private, isolated child process of a daemon cannot really be considered a security problem in this day and age -- unless you're on crack.
- An ambitious new built-in sandbox. Think of it as privsep++, but more on this in an upcoming post and paper.