Snort mailing list archives

Re: byte_test and buffer cursor


From: Alex McDonnell <amcdonnell () sourcefire com>
Date: Thu, 9 Feb 2017 16:34:23 -0500

I'm pretty sure that's in the Snort Manual, byte_test does not move the
cursor, byte_extract does. You could also test for the value you expect in
your second test to verify ;)

Alex McDonnell
TALOS

On Thu, Feb 9, 2017 at 4:30 PM, Y M <snort () outlook com> wrote:

Does a byte_test move the cursor into a buffer the number of bytes it
tests? Does is depend on the buffer against which the byte_test is
operating?


In essence, I am trying to use byte_test to validate that the decimal
value of X number of bytes fall within a decimal range. Something similar
to:


http_raw_header; byte_test:3,>,160,0,relative;
byte_test:3,<,170,0,relative;


If the first byte_test above moves the cursor 3 bytes into the buffer, how
can I reset the cursor back to the beginning of the buffer of the
last/relative content match (http_raw_header)? Or am I just doing it all
wrong?


YM




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