fail2ban/man/jail.conf.5

.TH JAIL.CONF "5" "March 2013" "Fail2Ban" "Fail2Ban Configuration"
.SH NAME
jail.conf \- configuration for the fail2ban server
.SH SYNOPSIS
.I jail.conf / jail.local

.I action.d/*.conf action.d/*.local

.I filter.d/*.conf filter.d/*.local
.SH DESCRIPTION
Fail2ban has three configuration file types. Action files are the commands for banning and unbanning of IP address,
Filter files tell fail2ban how to detect authentication failures, and Jail configurations combine filters with actions into jails.

There are *.conf files that are distributed by fail2ban and *.local file that contain user customizations.
It is recommended that *.conf files should remain unchanged.  If needed, customizations should be provided in *.local files.
For instance, if you would like to customize the [ssh-iptables-ipset] jail, create a jail.local to extend jail.conf
(the configuration for the fail2ban server).  The jail.local file will be the following if you only need to enable
it:

.TP
\fIjail.local\fR
[ssh-iptables-ipset]

enabled = true

.PP
Override only the settings you need to change and the rest of the configuration will come from the corresponding
*.conf file.

\fI*.d/\fR
.RS
In addition to .local, for any .conf file there can be a corresponding
\fI.d/\fR directory to contain additional .conf files that will be read after the
appropriate .local file.  Last parsed file will take precidence over
identical entries, parsed alphabetically, e.g.

.RS
\fIjail.d/01_enable.conf\fR - to enable a specific jail
.RE
.RS
\fIjail.d/02_custom_port.conf\fR - containing specific configuration entry to change the port of the jail specified in the configuration
.RE
.RS
\fIfail2ban.d/01_custom_log.conf\fR - containing specific configuration entry to use a different log path.
.RE
.RE

.SH DEFAULT
The following options are applicable to all jails. Their meaning is described in the default \fIjail.conf\fR file.
.TP
\fBignoreip\fR 
.TP
\fBbantime\fR
.TP
\fBfindtime\fR
.TP
\fBmaxretry\fR
.TP
\fBbackend\fR
.TP
\fBusedns\fR
.PP
.SS Backends
\fBbackend\fR specifies the backend used to get files modification. This option can be overridden in each jail as well.
Available options are listed below.
.TP
\fIpyinotify\fR
requires pyinotify (a file alteration monitor) to be installed. If pyinotify is not installed, Fail2ban will use auto.
.TP
\fIgamin\fR
requires Gamin (a file alteration monitor) to be installed. If Gamin is not installed, Fail2ban will use auto.
.TP
\fIpolling\fR
uses a polling algorithm which does not require external libraries.
.TP
\fIsystemd\fR
uses systemd python library to access the systemd journal. Specifying \fBlogpath\fR is not valid for this backend and instead utilises \fBjournalmatch\fR from the jails associated filter config.
.TP
\fIauto\fR
will try to use the following backends, in order: pyinotify, gamin, polling
.PP
.SS Actions
Each jail can be configured with only a single filter, but may have multiple actions. By default, the name of a action is the action filename. In the case where multiple of the same action are to be used, the \fBactname\fR option can be assigned to the action to avoid duplicatione.g.:
.PP
.nf
[ssh-iptables-ipset]
enabled = true
action = sendmail[name=ssh, dest=john@example.com, actname=mail-john]
         sendmail[name=ssh, dest=paul@example.com, actname=mail-paul]
.fi

.SH "ACTION FILES"
Action files specify which commands are executed to ban and unban an IP address. They are located under \fI/etc/fail2ban/action.d\fR.

Like with jail.conf files, if you desire local changes create an \fI[actionname].local\fR file in the \fI/etc/fail2ban/action.d\fR directory
and override the required settings.

Action files are ini files that have two sections, \fBDefinition\fR and \fBInit\fR . 

The [Init] section allows for action-specific settings. In \fIjail.conf/jail.local\fR these can be overwritten for a particular jail as options to the jail.

The following commands can be present in the [Definition] section.
.TP
\fBactionstart\fR
command(s) executed when the jail starts.
.TP
\fBactionstop\fR
command(s) executed when the jail stops.
.TP
\fBactioncheck\fR
the command ran before any other action. It aims to verify if the environment is still ok.
.TP
\fBactionban\fR
command(s) that bans the IP address after \fBmaxretry\fR log lines matches within last \fBfindtime\fR seconds.
.TP
\fBactionunban\fR
command(s) that unbans the IP address after \fBbantime\fR.

Commands specified in the [Definition] section are executed through a system shell so shell redirection and process control is allowed. The commands should
return 0, otherwise error would be logged.  Moreover if \fBactioncheck\fR exits with non-0 status, it is taken as indication that firewall status has changed and fail2ban needs to reinitialize itself (i.e. issue \fBactionstop\fR and \fBactionstart\fR commands).

Tags are enclosed in <>.  All the elements of [Init] are tags that are replaced in all action commands.  Tags can be added by the
\fBfail2ban-client\fR using the setctag command. \fB<br>\fR is a tag that is always a new line (\\n).

More than a single command is allowed to be specified. Each command needs to be on a separate line and indented with whitespaces without blank lines. The following example defines
two commands to be executed.

 actionban = iptables -I fail2ban-<name> --source <ip> -j DROP
             echo ip=<ip>, match=<match>, time=<time> >> /var/log/fail2ban.log

.SS "Action Tags"
The following tags are substituted in the actionban, actionunban and actioncheck (when called before actionban/actionunban) commands.
.TP
\fBip\fR
An IPv4 ip address to be banned. e.g. 192.168.0.2
.TP
\fBfailures\fR
The number of times the failure occurred in the log file. e.g. 3
.TP
\fBtime\fR
The unix time of the ban. e.g. 1357508484
.TP
\fBmatches\fR
The concatenated string of the log file lines of the matches that generated the ban. Many characters interpreted by shell get escaped.

.SH FILTER FILES

Filter definitions are those in \fI/etc/fail2ban/filter.d/*.conf\fR and \fIfilter.d/*.local\fR.

These are used to identify failed authentication attempts in logs and to extract the host IP address (or hostname if \fBusedns\fR is \fBtrue\fR).

Like action files, filter files are ini files. The main section is the [Definition] section.

There are two filter definitions used in the [Definition] section:

.TP
\fBfailregex\fR
is the regex (\fBreg\fRular \fBex\fRpression) that will match failed attempts. The tag \fI<HOST>\fR is used as part of the regex and is itself a regex
for IPv4 addresses and hostnames. fail2ban will work out which one of these it actually is.
For multiline regexs the tag \fI<SKIPLINES>\fR should be used to separate lines. This allows lines between the matched lines to continue to be searched for other failures. The tag can be used multiple times.

.TP
\fBignoreregex\fR
is the regex to identify log entries that should be ignored by fail2ban, even if they match failregex.


Using Python "string interpolation" mechanisms, other definitions are allowed and can later be used within other definitions as %(defnname)s. For example.

 baduseragents = IE|wget
 failregex = useragent=%(baduseragents)s

.PP
Similar to actions, filters have an [Init] section which can be overridden in \fIjail.conf/jail.local\fR. The filter [Init] section is limited to the following options:
.TP
\fBmaxlines\fR
specifies the maximum number of lines to buffer to match multi-line regexs. For some log formats this will not required to be changed. Other logs may require to increase this value if a particular log file is frequently written to.
.TP
\fBjournalmatch\fR
specifies the systemd journal match used to filter the journal entries. See \fBjournalctl(1)\fR and \fBsystemd.journal-fields(7)\fR for matches syntax and more details on special journal fields. This option is only valid for the \fIsystemd\fR backend.
.PP
Filters can also have a section called [INCLUDES]. This is used to read other configuration files.

.TP
\fBbefore\fR
indicates that this file is read before the [Definition] section.

.TP
\fBafter\fR
indicates that this file is read after the [Definition] section.

.SH AUTHOR
Fail2ban was originally written by Cyril Jaquier <cyril.jaquier@fail2ban.org>.
At the moment it is maintained and further developed by Yaroslav O. Halchenko <debian@onerussian.com> and a number of contributors.  See \fBTHANKS\fR file shipped with Fail2Ban for a full list.
.
Manual page written by Daniel Black and Yaroslav Halchenko.
.SH "REPORTING BUGS"
Report bugs to https://github.com/fail2ban/fail2ban/issues
.SH COPYRIGHT
Copyright \(co 2013 Daniel Black
.br
Copyright of modifications held by their respective authors.
Licensed under the GNU General Public License v2 (GPL).
.SH "SEE ALSO"
.br
fail2ban-server(1)