SECURITY OF THE PROXY

    The proxy runs with dropped priviledges, and chrooted.
    It can also be set to run on just one interface. All the string
    handling is done through the functions in str.c on sstr structures
    rather than raw buffers. Potential buffer overflows should be
    limited to that file.

DoS:

    Each client is served in a separate process which dies after a
    period of inactivity (using SIGALRM). Config file options exist
    for the maximimum number of clients and the maximum number of
    connections from a single IP.


Sanitising data that passes through the proxy

    Not much is done here. We only allow printable ascii characters
    through the control stream which should make sending buffer
    overflow code through the proxy pretty difficult. FTP commands are
    all forced to be in the format "XXXX [argument]", and replies in
    the form "nnn[-] Message". Bear in mind that FTP is a
    fundamentally insecure protocol, and that there is not much
    difference that a proxy can make to many aspects of that. I'd
    suggest turning on "BounceDefend", "SameAddress", and "APConv" in
    the config file.

Can someone use the proxy to make a hole in the firewall?

    Not from the outside (I hope:). It would be fairly easy to write a
    program to tunnel IP through the proxy if you had access to
    machines on both sides, but then again this is true of most
    protocols.

Transparent data connection proxying / libiptc [Kernel 2.4 only]

    If you are using transparent data connections then there is some
    code in linux.c which is forked off and runs as root in order to
    add and remove iptables entries. The amount of code here is very
    small, but in the case of an exploit in the main part of the code
    an attacker might be able to use this to add and delete fairly
    arbitrary iptables rules. If your ftp clients don't mind receiving
    data connections which are not from the ftp-server (all clients I
    have tested are OK with this, and it is the rfc compliant
    behaviour) then I suggest you leave this setting off.