atar wrote on 06/14/2016 20:29:
atar wrote on 06/14/2016 16:05:
atar wrote on 06/14/2016 14:52:
[...]
The hostname "google.com" isn't blocked since its current ip differs from its
previous ip when pf has loaded the rule, what can I do in order to be able to block such
sites (with many ip addresses)?
I would use tables and populate them periodically from shell script which can
do FQDN to many IPs resolution.
It can be simple as this
host yahoo.com | awk '$0 ~ /has address/ { print $4 }' > /var/run/pf.yahoo_table
pfctl -t yahoo_table -T replace -f /var/run/pf.yahoo.table
I am sure you will find better solution :)
Miroslav Lachman
Thanks for your answer, it is an interested idea.
However, is this method of update periodically the pf tables not disturb or
burden the performance of the pf filter engine especially if the script that
update the tables runs too often?
How often is "too often"?
I think that updating the tables every 5 minutes is enough (no one uses shorter
TTL for DNS entries)
The nicest thing on PF tables is you don't need to reload PF and tables can
live in memory (not need for persistent file on filesystem) so all operations
are really quick.
Our PF firewalls are using tables with thousands of entries without any issues.
I don't see any trouble even if you will update tables each minute.
Miroslav Lachman
Thanks again for replying.
I don't know why, but even refresh rate of one minute isn't enough for the
domains google.com or gmail.com.
Even immediately after I load the table which has the rule to block the above
mentioned domains I am still able to access those domains. Sometimes it is
indeed blocked for a half of a minute but finally the chromium browser succeed
to load them.
Do you have any idea?
I am not sure but it can have something with keep-state.
If you have PF disabled, then start it, populate table and then make
first connection attempt (there should be no states), are you still able
to connect for a half minute?
You can check tables by: pfctl -vv -s Tables
and check states by: pfctl -vv -s state
Miroslav Lachman
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