I'm trying to figure out how to use awk to parse values from a string of
unknown length and unknown fields using awk, from within a shell script, and
write those values to a file in a certain order.
Here's a typical string that I want to parse:
alert ip
[50.0.0.0/8,100.0.0.0/6,104.0.0.0/5,112.0.0.0/6,173.0.0.0/8,174.0.0.0/7,176.0.0.0/5,184.0.0.0/6]
any -> $HOME_NET any (msg:"ET POLICY Reserved IP Space Traffic - Bogon Nets 2";
classtype:bad-unknown; reference:url,www.cymru.com/Documents/bogon-list.html;
threshold: type limit, track by_src, count 1, seconds 360; sid:2002750; rev:10;)
What I want to do is extract the value after "sid:", the value after
"reference:" and the value after "msg:" and insert them into a file that would
look like this:
2002750 || "ET POLICY Reserved IP Space Traffic - Bogon Nets 2" ||
url,www.cymru.com/Documents/bogon-list.html
Yes, I know I could do this easily in Perl. I'm doing this to try and improve
my understanding of awk. I *think* I've figured out that the right approach is
to use an associative array, and this command:
# awk '!/#/ { for (i=1; i<=NF; i++) { if ( $i ~ /sid/) {mtcmsg[sid]=$i; print
mtcmsg[sid]}}}' < /usr/local/etc/snort/rules/mtc.rules.test
prodcues this data:
sid:299913;
sid:52123;
sid:3001441;
sid:1444;
sid:2008120;
sid:5001684;
sid:2001683;
sid:22466;
sid:2002750;
sid:3000003;
sid:292000032;
sid:22000032;
sid:3000000;
sid:2003070;
sid:2003484;
sid:2003603;
sid:31000004;
sid:299998;
So it appears (at least to me) that I'm on the right path, but I thought I'd
query the awk gurus on the list. Is there a better way to approach this?
The standard FS breaks the msg into multiple fields, which is unacceptable. So
my thinking is that I would need to do somthing like this (pseudocode)
!/#/; FS=";" {if ( $i ~ /sid/) then use tr to stip the "sid:" and ";" and
insert the result into an element named sid
if ($i ~ /reference/) then ditto into an element named ref
if $i ~ /msg/) then ditto into an element named msg)
then print array[sid]" || "array[msg]" || " array[ref] > resulting file.}
But when I add an FS to the script, I get odd results:
# awk '!/#/ { FS=";"; for (i=1; i<=NF; i++) { if ( $i ~ /sid/)
{mtcmsg[sid]=$i; print mtcmsg[sid]}}}' <
/usr/local/etc/snort/rules/mtc.rules.test
sid:299913;
sid:52123
sid:3001441
sid:1444
sid:2008120
sid:5001684
sid:2001683
sid:22466
sid:2002750
sid:3000003
sid:292000032
sid:22000032
sid:3000000
sid:2003070
sid:2003484
sid:2003603
sid:31000004
sid:299998
Why is the first value indented and not stripped of the semi-colon?
--
Paul Schmehl, Senior Infosec Analyst
As if it wasn't already obvious, my opinions
are my own and not those of my employer.
*******************************************
"It is as useless to argue with those who have
renounced the use of reason as to administer
medication to the dead." Thomas Jefferson
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