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.Cd #
61.Cd # ipfw(8) configuration.
62.Cd #
63.Cd ipfw table 0 create
64.Cd ipfw add deny ip from '<0>' to any
65.Pp
66.Cd # in /etc/syslog.conf
67.Cd #
68.Cd auth.info;authpriv.info		|exec /usr/sbin/sshlockout -ipfwtbl 0
69.Pp
70.Cd # in root's crontab
71.Cd #
72.Cd 3 3 * * *       ipfw -fq table 0 expire 86400
73.Sh DESCRIPTION
74This program is generally installed in
75.Pa /etc/syslog.conf
76as a pipe to parse the
77.Xr sshd 8
78demons error log in realtime.
79In addition, a root crontab entry should generally be created to clean
80out stale entries in the
81.Xr pf 4
82or
83.Xr ipfw 8
84.Ar table
85at least once a day.
86Using expire instead of flush will maintain a rolling window of locked out
87IPs.
88The
89.Xr pf 4
90or
91.Xr ipfw 8
92module must be loaded and running with the table and rules properly
93configured.
94.Pp
95This program will monitor the ssh syslog output and keep track of attempts
96to login to unknown users as well as preauth failures.
97If 5 attempts fail in any one hour period, a permanent entry is added to the
98.Xr pf 4
99or
100.Xr ipfw 8
101.Ar table
102for the associated IP address.
103You still have to add a rule to
104.Xr pf.conf 5
105or use
106.Xr ipfw 8
107to block IP addresses listed in this table.
108The cron entry you create cleans the block list out typically once a day.
109.Pp
110This program generally limits brute-force attempts to break into a machine
111via ssh.
112.Pp
113When setting up the
114.Xr pf 4
115or
116.Xr ipfw 8
117rules,
118note that the table will be filled based on failed ssh connections destined
119to that particular machine.
120If the machine is acting as a router you can decide whether you want the
121.Xr pf 4
122or
123.Xr ipfw 8
124rule to lockout that suspect IP to just the machine,
125or to everything it routes to.
126We usually recommend an unconditional blocking rule.
127.Sh NOTICE
128This program is still a work in progress.
129.Sh SEE ALSO
130.Xr ssh 1 ,
131.Xr pf 4 ,
132.Xr syslog.conf 5 ,
133.Xr ipfw 8 ,
134.Xr sshd 8
135.Sh HISTORY
136The
137.Nm
138utility first appeared in
139.Dx 4.1 .
140.Sh AUTHORS
141.An Matthew Dillon Aq Mt dillon@backplane.com
142