NAME
blacklistd
—
block and release ports on demand to
avoid DoS abuse
SYNOPSIS
blacklistd |
[-dfrv ] [-C
controlprog] [-c
configfile] [-D
dbfile] [-P
sockpathsfile] [-R
rulename] [-s
sockpath] [-t
timeout] |
DESCRIPTION
blacklistd
is a daemon similar to
syslogd(8) that listens to sockets at paths specified in the
sockpathsfile for notifications from other daemons about
successful or failed connection attempts. If no such file is specified, then
it only listens to the socket path specified by
sockspath or if that is not specified to
/var/run/blacklistd.sock. Each notification contains
an (action, port, protocol, address, owner) tuple that identifies the remote
connection and the action. This tuple is consulted against entries in
configfile with syntax specified in
blacklistd.conf(5). If an entry is matched, a state entry is
created for that tuple. Each entry contains a number of tries limit and a
duration.
If the action is “add” and the number of tries limit is reached, then a control script controlprog is invoked with arguments:
control add <rulename> <proto> <address> <mask> <port>
and should invoke a packet filter command to block the connection
specified by the arguments. The rulename argument can
be set from the command line (default blacklistd
).
The script could print a numerical id to stdout as a handle for the rule
that can be used later to remove that connection, but that is not required
as all information to remove the rule is kept.
If the action is “remove” Then the same control script is invoked as:
control remove <rulename> <proto> <address> <mask> <port> <id>
where id is the number returned from the “add” action.
blacklistd
maintains a database of known
connections in dbfile. On startup it reads entries
from that file, and updates its internal state.
blacklistd
checks the list of active
entries every timeout seconds (default
15
) and removes entries and block rules using the
control program as necessary.
The following options are available:
-C
controlprog- Use controlprog to communicate with the packet
filter, usually /usr/libexec/blacklistd-helper.
The following arguments are passed to the control program:
- action
- The action to perform:
add
,rem
, orflush
to add, remove or flush a firewall rule. - name
- The rule name.
- protocol
- The optional protocol name (can be empty):
tcp
,tcp6
,udp
,udp6
. - address
- The IPv4 or IPv6 numeric address to be blocked or released.
- mask
- The numeric mask to be applied to the blocked or released address
- port
- The optional numeric port to be blocked (can be empty).
- id
- For packet filters that support removal of rules by rule identifier, the identifier of the rule to be removed. The add command is expected to return the rule identifier string to stdout.
-c
configuration- The name of the configuration file to read, usually /etc/blacklistd.conf.
-D
dbfile- The Berkeley DB file where
blacklistd
stores its state, usually /var/run/blacklistd.db. -d
- Normally,
blacklistd
disassociates itself from the terminal unless the-d
flag is specified, in which case it stays in the foreground. -f
- Truncate the state database and flush all the rules named
rulename are deleted by invoking the control script
as:
control flush <rulename>
-P
sockspathsfile- A file containing a list of pathnames, one per line that
blacklistd
will create sockets to listen to. This is useful for chrooted environments. -R
rulename- Specify the default rule name for the packet filter rules, usually
blacklistd
. -r
- Re-read the firewall rules from the internal database, then remove and re-add them. This helps for packet filters that do not retain state across reboots.
-s
sockpath- Add sockpath to the list of Unix sockets
blacklistd
listens to. -t
timeout- The interval in seconds
blacklistd
polls the state file to update the rules. -v
- Cause
blacklistd
to print diagnostic messages tostdout
instead of syslogd(8).
SIGNAL HANDLING
blacklistd
deals with the following
signals:
- HUP
- Receipt of this signal causes
blacklistd
to re-read the configuration file. - INT, TERM & QUIT
- These signals tell
blacklistd
to exit in an orderly fashion. - USR1
- This signal tells
blacklistd
to increase the internal debugging level by 1. - USR2
- This signal tells
blacklistd
to decrease the internal debugging level by 1.
FILES
- /usr/libexec/blacklistd-helper
- Shell script invoked to interface with the packet filter.
- /etc/blacklistd.conf
- Configuration file.
- /var/db/blacklistd.db
- Database of current connection entries.
- /var/run/blacklistd.sock
- Socket to receive connection notifications.
SEE ALSO
HISTORY
blacklistd
first appeared in
NetBSD 7. FreeBSD support
for blacklistd
was implemented in
FreeBSD 11.
AUTHORS
Christos Zoulas