[Snort-users] (smtp) Attempted header name buffer overflow: xx chars before colon

Todd Wease twease at ...1935...
Tue Sep 2 10:28:27 EDT 2008


Hi Ryan,

This should be fixed in 2.8.3.  For now, you can comment the 
SMTP_HEADER_NAME_OVERFLOW rule in preproc.rules.  To utilize the 
preproc.rules you need to compile Snort with 
"--enable-decoder-preprocessor-rules" and uncomment "include 
$PREPROC_RULE_PATH/preprocessor.rules" in snort.conf.

Todd

chris ryan wrote:
> Hi,
>
> we are running snort (2.8.2.1, latest subscribers rule set) in front of
> an big email infrastructure (>10000 users).
>
> I'm getting a lot of these alerts from the smtp preprocessor:
> "(smtp) Attempted header name buffer overflow: xx chars before colon",
> where xx is (65 .. 255).
>
> I found an older post on the list:
>
>   
>> ----
>>     
> Todd Wease
> Date: 2008-03-27 12:41:50
>
> The header name buffer overflow looks for a header name > 64 characters.
> Header names are taken to be the tags in the data header, e.g.
>
> Subject:
> Return-Path:
> Received:
> etc.
>
> If the number of characters before the ":" is more than 64 characters
> the smtp preprocessor alerts.  The max_header_line_len has nothing to do
> with this - it looks for the length of the entire line.
>
> Is your network asynchronous?  Are you dropping packets?  Can you
> provide a pcap that generates the alert (send to <email removed>)?
>   
>> ----
>>     
>
> Our network isn't asynchronous and we have a very, very low drop rate.
> Most of the false postives seem to be newsletters or spam in html.
> I can provide pcaps of that, if needed.
>
> Is there a way of disabling that warning without disabling the hole
> preprocessor? I only found these in the preproc.rules:
> SMTP_COMMAND_OVERFLOW
> SMTP_DATA_HDR_OVERFLOW
> SMTP_RESPONSE_OVERFLOW
> SMTP_SPECIFIC_CMD_OVERFLOW
> SMTP_UNKNOWN_CMD
> SMTP_ILLEGAL_CMD
> SMTP_HEADER_NAME_OVERFLOW
>
> It seems to me that the alert message is still from the preprocessor
> itself and does not use the preproc.rules.
>
>
> Thanks in advance,
> Chris.
>
>
>
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