Re: SMTP decoder

[waldo kitty <wkitty42 () windstream net>]

On 2/11/2015 4:50 PM, Joel Esler (jesler) wrote:
> You’ve got your two alternatives there.  Raise the limit, or suppress the alert.
>
> Ask yourself what your action is going to be there.  “What am I going to do
> about a big SMTP server command”, if the answer is “nothing”, then suppress the
> alert.  If the answer is anything else, then use your best judgement as to what
> action you should take.

since RFC1869 allows for a larger command line length, would it be a good idea 
if snort's AMTP preprocessor allowed for different length check settings for 
each of HELO or EHLO? ;)

> --
> *Joel Esler*
> Open Source Manager
> Threat Intelligence Team Lead
> Talos
>
> > On Feb 11, 2015, at 9:51 AM, Dan Roberts <danroberts2604 () gmail com
> > <mailto:danroberts2604 () gmail com>> wrote:
> >
> > Hello guys,
> >
> > I'm running SNORT since a few months now, and I still get a lot of alerts like:
> >
> > *"(smtp) Attempted command buffer overflow: more than 512 chars ...."*
> >
> > In the snort.conf file, we find following parameter for the smtp decoder:
> >
> > *"max_command_line_len 512"*
> >
> > Although the maximum command line length is "strictly" limited to 512 by RFC
> > 821 (HELO), the RFC 1869 (EHLO) authorize the extension of this limit:
> > ... */This specification extends the SMTP MAIL FROM and TO to allow additional
> > parameters and parameter values. It is possible that the MAIL FROM and RCPT TO
> > lines that result will exceed the 512 character limit on command line length
> > imposed by RFC 821/*.
> > ..."
> >
> > How do you,  guys, manage this ?
> > Do you simply consider these alerts as FP ?
> > Have you raised the max_command_line_len limit ?



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