preauth usage

"Michael T. Davis" <[email protected]> Mon, 05 Apr 2010 12:32:40 -0400 (EDT)
Newsgroups gmane.comp.security.firewalls.ipfilter
Message-ID <18967_1270485292_4BBA112C_18967_2883_1_01NLLCNLRJYQ96DXHF@ecr6.ohio-state.edu>
	I'd like to leverage preauth, if possible, to add an optionally
tighter access control to certain services.  For example, let's look at
SSH:

block in quick on fxp0 proto tcp from any to any port = 22      head 22
block in quick from <bad-ip-1> to any                group 22
block in quick from <bad-ip-2> to any                group 22
#...etc...
pass  in quick proto tcp from any to <ip-range-1> \
 flags S/SAFR keep state group 22
pass  in quick proto tcp from any to <ip-range-2> \
 flags S/SAFR keep state group 22
#...etc...

Could a preauth rule be added as the second rule in the group...?

block in quick on fxp0 proto tcp from any to any port = 22      head 22
preauth in quick from any to any group 22
block in quick from <bad-ip-1> to any                group 22
block in quick from <bad-ip-2> to any                group 22
#...etc...
pass  in quick proto tcp from any to <ip-range-1> \
 flags S/SAFR keep state group 22
pass  in quick proto tcp from any to <ip-range-2> \
 flags S/SAFR keep state group 22
#...etc...

I'm concerned over the man page entry, which says, "If no further matching
rule is found, the packet will be dropped..."  Is this the case even for a
preauth in a group?  I'm hoping that, upon not finding a matching rule in the
pre-auth. list, processing would "bounce back" to the group and continue
processing the group rules.  Or, should the paraenthetical statement, "...the
FR_PREAUTH is not the same as FR_PASS," be interpreted to mean that rule
processing doesn't work the same for preauth, and if a matching rule doesn't
exist in the pre-auth. list, the packet really will be dropped right then and
there (regardless of any pre-existing "group context")?

Thanks,
Mike