blacklistd is now available for current (comments?)

[christos%zoulas.com@localhost (Christos Zoulas)]

You can get it from http://www.netbsd.org/~christos/blacklistd.tar.gz

Appended is the README file. I wrote this over the weekend, it seems to
work :-) Please let me know what you think? Is it useful? Should I commit
it to the base system? Do you have any suggestions to improve it?

christos

--- snip ---

# Tue Jan 20 21:18:54 EST 2015

This is package contains library that can be used by network daemons to
communicate with a packet filter via a daemon to enforce opening and
closing ports dynamically based on policy.

The interface to the packet filter is in etc/control (this is currently
designed for npf) and the configuration file (inspired from inetd.conf)
is in etc/conf.

A patch to OpenSSH is in ssh.diff that adds blacklisting capabilities to
openssh.

The network daemon (for example sshd) communicates to blacklistd, via
a unix socket like syslog. The library calls are simple and everything
is handled by the library. In the simplest form the only thing the
daemon needs to do is to call:

	blacklist(action, acceptedfd, message);

Where:
	action = 0 -> successful login clear blacklist state
		 1 -> failed login, add to the failed count
	acceptedfd -> the file descriptor where the server is
		      connected to the remote client. It is used
		      to determine the listening socket, and the
		      remote address. This allows any program to
		      contact the blacklist daemon, since the verification
		      if the program has access to the listening
		      socket is done by virtue that the port
		      number is retrieved from the kernel.
	message    -> an optional string that is used in debugging logs.

The configuration file contains entries of the form:

# Blacklist rule
# Port	type	protocol	owner		nfail	disable
ssh	stream	tcp		*		6	60m
ssh	stream	tcp6		*		6	60m

Here note that owner is * because the connection is done from the
child ssh socket which runs with user privs. We also register for
both tcp and tcp6 since those are different listening sockets and
addresses. We use nfail = 6, because ssh allows 3 password attempts
per connection, and this will let us have 2 connections before
blocking.  Finally we block for an hour; we could block forever
too by specifying * in the duration column.

blacklistd and the library use syslog(3) to report errors. The
blacklist filter state is persisted automatically in /var/db/blacklistd.db
so that if the daemon is restarted, it remembers what connections
is currently handling. To start from a fresh state (if you restart
npf too for example), you can use -f. To watch the daemon at work,
you can use -d.

The current control file is designed for npf, and it uses the
dynamic rule feature. You need to create a dynamic rule in your
/etc/npf.conf on the group referring to the interface you want to block
called blacklistd as follows:

ext_if=bge0
	
group "external" on $ext_if {
	...
        ruleset "blacklistd" 
	...
}

Enjoy,

christos