Full-Disclosure posting "FreeBSD 9.1 ftpd Remote Denial of Service"

[Dmitry Morozovsky]

On Mon, 4 Feb 2013, Alexandr Kovalenko wrote:

> On Mon, Feb 4, 2013 at 6:27 PM, Fabian Wenk <fabian at wenks.ch> wrote:
> > A few days ago there was the posting "FreeBSD 9.1 ftpd Remote Denial of
> > Service" [1] on the Full-Disclosure mailing list. Is this a known issue to
> > the FreeBSD community?
> >
> >   [1]
> > http://lists.grok.org.uk/pipermail/full-disclosure/2013-February/089583.html
> >
> > There are also many ftp.*.freebsd.org mirrors listed in the above mention
> > posting, so I also put freebsd-hubs@ into the recipient list. This will
> > probably help, that ftp mirror operators are alerted and can take any action
> > if needed.
> 
> I can confirm this is an issue on stable/9 r245742. Though I hardly
> can call it DoS as normally ftp account is running with well-defined
> ulimits and proper ftpd usage pattern does not generate much CPU
> usage, so you can keep limits pretty much low, thus not being affected
> by so-called "DoS".
> 
> Nevertheless any ideas on how to fix our glob(3)?

Not the global fix, but workaround (kinda) for current situation, via dadv:

Add to your /etc/login.conf

ftp:\
    :priority=20:\
    :cputime=5:
    :tc=default:

and rebuild yout login.conf database via 

cap_mkdb /etc/login.conf

Than, apply newly create class to anonymous ftp user:

pw usermod ftp -L ftp

This should not affect regular ftp consumer, as they are hardly comsume host' 
resources, but will stop malicious anonymous users from eating your 
CPU resources.

--

Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
[ FreeBSD committer:                                 marck at FreeBSD.org ]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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