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Date: Thu, 04 Aug 2005 12:46:20 -0500
From: Paul Schmehl <pauls@utdallas.edu>
To: freebsd-questions@freebsd.org
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Subject: Shell script question
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I'm working on a shell script to use p0f to identify "unauthorized" hosts 
on our network.

In the script I use an echo command to see what the output of the command 
is.  This is what it looks like:
/usr/local/bin/p0f -i xl0 -N -l -o /root/capture.1123177152.log 'src net 
10.0.0.0/8 or src net 129.110.0.0/16'

If I paste the output of the echo command to the cli and hit enter, p0f 
runs and writes to the log.  Yet when I actually try to run that same 
command from the script, p0f complains:

pcap_compile: illegal token: '
See man tcpdump or p0f README for help on bpf filter expressions.

Here's the script.  It's very simple right now, but there's a lot more work 
to be done.  I first have to figure out this problem, though:

#!/bin/sh

P0F=/usr/local/bin/p0f
EPOCH_DATE=`date -j -f "%a %b %d %T %Z %Y" "\`date\`" "+%s"`
LOG=/root/capture.${EPOCH_DATE}.log
NIC="-i xl0"
ARGS="-N -l -o ${LOG}"
DAEMON="-d"
FILTER="'src net 10.0.0.0/8 or src net 129.110.0.0/16'"

echo "${P0F} ${NIC} ${ARGS} ${DAEMON} ${FILTER}"
${P0F} ${NIC} ${ARGS} ${FILTER}

Why is p0f complaining about the bpf filter?  I've tried escaping the 
single quotes, but that generates a different error.  I don't understand 
why the identical command works on the cli, but not in the script.

Paul Schmehl (pauls@utdallas.edu)
Adjunct Information Security Officer
University of Texas at Dallas
AVIEN Founding Member
http://www.utdallas.edu/ir/security/