1.\" Copyright (c) 2015 The DragonFly Project.  All rights reserved.
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3.\" This code is derived from software contributed to The DragonFly Project
4.\" by Matthew Dillon <dillon@backplane.com>
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33.Dd September 13, 2017
34.Dt SSHLOCKOUT 8
35.Os
36.Sh NAME
37.Nm sshlockout
38.Nd utility to block port 22 on preauth failures
39.Sh SYNOPSIS
40.Cd #
41.Cd # pf(4) configuration.
42.Cd #
43.Pp
44.Cd # in /etc/pf.conf
45.Cd #
46.Cd table <lockout> persist { }
47.Pp
48.Cd # and later in /etc/pf.conf - see below
49.Cd #
50.Cd block in quick on $ext_if proto tcp from <lockout> to any port 22
51.Pp
52.Cd # in /etc/syslog.conf
53.Cd #
54.Cd auth.info;authpriv.info		|exec /usr/sbin/sshlockout -pf "lockout"
55.Pp
56.Cd # in root's crontab
57.Cd #
58.Cd 3 3 * * *       pfctl -tlockout -T expire 86400
59.Pp
60.Pp
61.Cd #
62.Cd # ipfw(8) configuration.
63.Cd #
64.Cd ipfw table 0 create
65.Cd ipfw add deny ip from '<0>' to any
66.Pp
67.Cd # in /etc/syslog.conf
68.Cd #
69.Cd auth.info;authpriv.info		|exec /usr/sbin/sshlockout -ipfwtbl 0
70.Pp
71.Cd # in root's crontab
72.Cd #
73.Cd 3 3 * * *       ipfw -fq table 0 expire 86400
74.Sh DESCRIPTION
75This program is generally installed in
76.Pa /etc/syslog.conf
77as a pipe to parse the
78.Xr sshd 8
79demons error log in realtime.
80In addition, a root crontab entry should generally be created to clean
81out stale entries in the
82.Xr pf 4
83or
84.Xr ipfw 8
85.Ar table
86at least once a day.
87Using expire instead of flush will maintain a rolling window of locked out
88IPs.
89The
90.Xr pf 4
91or
92.Xr ipfw 8
93module must be loaded and running with the table and rules properly
94configured.
95.Pp
96This program will monitor the ssh syslog output and keep track of attempts
97to login to unknown users as well as preauth failures.
98If 5 attempts fail in any one hour period, a permanent entry is added to the
99.Xr pf 4
100or
101.Xr ipfw 8
102.Ar table
103for the associated IP address.
104You still have to add a rule to
105.Xr pf.conf 5
106or use
107.Xr ipfw 8
108to block IP addresses listed in this table.
109The cron entry you create cleans the block list out typically once a day.
110.Pp
111This program generally limits brute-force attempts to break into a machine
112via ssh.
113.Pp
114When setting up the
115.Xr pf 4
116or
117.Xr ipfw 8
118rules,
119note that the table will be filled based on failed ssh connections destined
120to that particular machine.
121If the machine is acting as a router you can decide whether you want the
122.Xr pf 4
123or
124.Xr ipfw 8
125rule to lockout that suspect IP to just the machine,
126or to everything it routes to.
127We usually recommend an unconditional blocking rule.
128.Sh NOTICE
129This program is still a work in progress.
130.Sh SEE ALSO
131.Xr ssh 1 ,
132.Xr pf 4 ,
133.Xr syslog.conf 5 ,
134.Xr ipfw 8 ,
135.Xr sshd 8
136.Sh HISTORY
137The
138.Nm
139utility first appeared in
140.Dx 4.1 .
141.Sh AUTHORS
142.An Matthew Dillon Aq Mt dillon@backplane.com
143