Ubuntu Manpage: jail.conf - configuration for the fail2ban server

NAME

       jail.conf - configuration for the fail2ban server

SYNOPSIS

       fail2ban.conf fail2ban.d/*.conf fail2ban.local fail2ban.d/*.local

       jail.conf jail.d/*.conf jail.local jail.d/*.local

       action.d/*.conf action.d/*.local action.d/*.py

       filter.d/*.conf filter.d/*.local

DESCRIPTION

       Fail2ban has four configuration file types:

       fail2ban.conf
              Fail2Ban global configuration (such as logging)

       filter.d/*.conf
              Filters specifying how to detect authentication failures

       action.d/*.conf
              Actions defining the commands for banning and unbanning of IP address

       jail.conf
              Jails defining combinations of Filters with Actions.

CONFIGURATION FILES FORMAT

*.conf files are distributed by Fail2Ban. It is recommended that *.conf files should remain unchanged to
ease upgrades. If needed, customizations should be provided in *.local files. For example, if you would
like to enable the [ssh-iptables-ipset] jail specified in jail.conf, create jail.local containing

jail.local
[ssh-iptables-ipset]

enabled = true

In .local files specify only the settings you would like to change and the rest of the configuration will
then come from the corresponding .conf file which is parsed first.

jail.d/ and fail2ban.d/

In addition to .local, for jail.conf or fail2ban.conf file there can be a corresponding .d/
directory containing additional .conf files. The order e.g. for jail configuration would be:

jail.conf
jail.d/*.conf (in alphabetical order)
jail.local
jail.d/*.local (in alphabetical order).

i.e. all .local files are parsed after .conf files in the original configuration file and files
under .d directory. Settings in the file parsed later take precedence over identical entries in
previously parsed files. Files are ordered alphabetically, e.g.

fail2ban.d/01_custom_log.conf - to use a different log path
jail.d/01_enable.conf - to enable a specific jail
jail.d/02_custom_port.conf - to change the port(s) of a jail.

Configuration files have sections, those specified with [section name], and name = value pairs. For those
name items that can accept multiple values, specify the values separated by spaces, or in separate lines
space indented at the beginning of the line before the second value.

Configuration files can include other (defining common variables) configuration files, which is often
used in Filters and Actions. Such inclusions are defined in a section called [INCLUDES]:

before indicates that the specified file is to be parsed before the current file.

after indicates that the specified file is to be parsed after the current file.

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

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

Comments: use '#' for comment lines and '; ' (space is important) for inline comments. When using
Python2.X '; ' can only be used on the first line due to an Python library bug.

FAIL2BAN CONFIGURATION FILE(S) (fail2ban.conf)

These files have one section, [Definition].

The items that can be set are:

loglevel
verbosity level of log output: CRITICAL, ERROR, WARNING, NOTICE, INFO, DEBUG. Default: ERROR

logtarget
log target: filename, SYSLOG, STDERR or STDOUT. Default: STDERR . Only a single log target can be
specified. If you change logtarget from the default value and you are using logrotate -- also
adjust or disable rotation in the corresponding configuration file (e.g. /etc/logrotate.d/fail2ban
on Debian systems).

socket socket filename. Default: /var/run/fail2ban/fail2ban.sock . This is used for communication with
the fail2ban server daemon. Do not remove this file when Fail2ban is running. It will not be
possible to communicate with the server afterwards.

pidfile
PID filename. Default: /var/run/fail2ban/fail2ban.pid. This is used to store the process ID of
the fail2ban server.

dbfile Database filename. Default: /var/lib/fail2ban/fail2ban.sqlite3 This defines where the persistent
data for fail2ban is stored. This persistent data allows bans to be reinstated and continue
reading log files from the last read position when fail2ban is restarted. A value of None disables
this feature.

dbpurgeage
Database purge age in seconds. Default: 86400 (24hours) This sets the age at which bans should be
purged from the database.

JAIL CONFIGURATION FILE(S) (jail.conf)

The following options are applicable to any jail. They appear in a section specifying the jail name or in
the [DEFAULT] section which defines default values to be used if not specified in the individual section.

filter name of the filter -- filename of the filter in /etc/fail2ban/filter.d/ without the .conf/.local
extension. Only one filter can be specified.

logpath
filename(s) of the log files to be monitored, separated by new lines. Globs -- paths containing *
and ? or [0-9] -- can be used however only the files that exist at start up matching this glob
pattern will be considered.

Optional space separated option 'tail' can be added to the end of the path to cause the log file
to be read from the end, else default 'head' option reads file from the beginning

Ensure syslog or the program that generates the log file isn't configured to compress repeated log
messages to "*last message repeated 5 time*s" otherwise it will fail to detect. This is called
RepeatedMsgReduction in rsyslog and should be Off.

logencoding
encoding of log files used for decoding. Default value of "auto" uses current system locale.

action action(s) from /etc/fail2ban/action.d/ without the .conf/.local extension. Arguments can be passed
to actions to override the default values from the [Init] section in the action file. Arguments
are specified by:

[name=value,name2=value,name3="values,values"]

Values can also be quoted (required when value includes a ","). More that one action can be
specified (in separate lines).

ignoreip
list of IPs not to ban. They can include a CIDR mask too.

ignorecommand
command that is executed to determine if the current candidate IP for banning should not be
banned. IP will not be banned if command returns successfully (exit code 0). Like ACTION FILES,
tags like <ip> are can be included in the ignorecommand value and will be substituted before
execution. Currently only <ip> is supported however more will be added later.

bantime
effective ban duration (in seconds).

findtime
time interval (in seconds) before the current time where failures will count towards a ban.

maxretry
number of failures that have to occur in the last findtime seconds to ban then IP.

backend
backend to be used to detect changes in the logpath. It defaults to "auto" which will try
"pyinotify", "gamin", "systemd" before "polling". Any of these can be specified. "pyinotify" is
only valid on Linux systems with the "pyinotify" Python libraries. "gamin" requires the "gamin"
libraries.

usedns use DNS to resolve HOST names that appear in the logs. By default it is "warn" which will resolve
hostnames to IPs however it will also log a warning. If you are using DNS here you could be
blocking the wrong IPs due to the asymmetric nature of reverse DNS (that the application used to
write the domain name to log) compared to forward DNS that fail2ban uses to resolve this back to
an IP (but not necessarily the same one). Ideally you should configure your applications to log a
real IP. This can be set to "yes" to prevent warnings in the log or "no" to disable DNS resolution
altogether (thus ignoring entries where hostname, not an IP is logged)..

failregex
regex (Python regular expression) to be added to the filter's failregexes. If this is useful for
others using your application please share you regular expression with the fail2ban developers by
reporting an issue (see REPORTING BUGS below).

ignoreregex
regex which, if the log line matches, would cause Fail2Ban not consider that line. This line will
be ignored even if it matches a failregex of the jail or any of its filters.

Backends
Available options are listed below.

pyinotify
requires pyinotify (a file alteration monitor) to be installed. If pyinotify is not installed,
Fail2ban will use auto.

gamin requires Gamin (a file alteration monitor) to be installed. If Gamin is not installed, Fail2ban
will use auto.

polling
uses a polling algorithm which does not require external libraries.

systemd
uses systemd python library to access the systemd journal. Specifying logpath is not valid for
this backend and instead utilises journalmatch from the jails associated filter config.

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, and in the case of Python actions, the ".py" file extension is
stripped. Where multiple of the same action are to be used, the actname option can be assigned to the
action to avoid duplication e.g.:

[ssh-iptables-ipset]
enabled = true
action = smtp.py[dest=chris@example.com, actname=smtp-chris]
smtp.py[dest=sally@example.com, actname=smtp-sally]

ACTION CONFIGURATION FILES (**action.d/*.conf**)

       Action files specify which commands are executed to ban and unban an IP address.

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

       Action files have two sections, Definition and Init .

       The  [Init] section enables action-specific settings. In jail.conf/jail.local these can be overridden for
       a particular jail as options of the action's specification in that jail.

       The following commands can be present in the [Definition] section.

       actionstart
              command(s) executed when the jail starts.

       actionstop
              command(s) executed when the jail stops.

       actioncheck
              command(s) ran before any other action. It aims to verify if the environment is still ok.

       actionban
              command(s) that bans the IP address after maxretry log lines matches within last findtime seconds.

       actionunban
              command(s) that unbans the IP address after bantime.

       The [Init] section allows for action-specific settings. In jail.conf/jail.local these can be  overwritten
       for  a  particular  jail  as  options to the jail. The following are special tags which can be set in the
       [Init] section:

       timeout
              The maximum period of time in seconds that a command can executed, before being killed.

       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 actioncheck exits with non-0 status, it is taken as indication that firewall status  has  changed  and
       fail2ban  needs  to  reinitialize  itself  (i.e.  issue  actionstop  and actionstart 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 fail2ban-client using the "set <JAIL> action <ACT>" command. <br> 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 whitespace(s) 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

   Action Tags
       The  following  tags  are  substituted  in the actionban, actionunban and actioncheck (when called before
       actionban/actionunban) commands.

       ip     IPv4 IP address to be banned. e.g. 192.168.0.2

       failures
              number of times the failure occurred in the log file. e.g. 3

       ipfailures
              As per failures, but total of all failures for that ip address across all jails from the  fail2ban
              persistent database. Therefore the database must be set for this tag to function.

       ipjailfailures
              As per ipfailures, but total based on the IPs failures for the current jail.

       time   UNIX (epoch) time of the ban. e.g. 1357508484

       matches
              concatenated  string  of the log file lines of the matches that generated the ban. Many characters
              interpreted by shell get escaped to prevent injection, nevertheless use with caution.

       ipmatches
              As per matches, but includes all lines for the IP which are contained with the fail2ban persistent
              database. Therefore the database must be set for this tag to function.

       ipjailmatches
              As per ipmatches, but matches are limited for the IP and for the current jail.

PYTHON ACTION FILES

       Python based actions can also be used, where the file name must be [actionname].py. The Python file  must
       contain  a variable Action which points to Python class. This class must implement a minimum interface as
       described by fail2ban.server.action.ActionBase, which can be inherited from to ease implementation.

FILTER FILES (**filter.d/*.conf**)

Filter definitions are those in /etc/fail2ban/filter.d/*.conf and filter.d/*.local.

These are used to identify failed authentication attempts in log files and to extract the host IP address
(or hostname if usedns is true).

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:

failregex
is the regex (regular expression) that will match failed attempts. The tag <HOST> is used as part
of the regex and is itself a regex for IPv4 addresses (and hostnames if usedns). Fail2Ban will
work out which one of these it actually is. For multiline regexs the tag <SKIPLINES> 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.

ignoreregex
is the regex to identify log entries that should be ignored by Fail2Ban, even if they match
failregex.

Similar to actions, filters have an [Init] section which can be overridden in jail.conf/jail.local. The
filter [Init] section is limited to the following options:

maxlines
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.

datepattern
specifies a custom date pattern/regex as an alternative to the default date detectors e.g.
%Y-%m-%d %H:%M(?::%S)?. For a list of valid format directives, see Python library documentation
for strptime behaviour.
Also, special values of Epoch (UNIX Timestamp), TAI64N and ISO8601 can be used.
NOTE: due to config file string substitution, that %'s must be escaped by an % in config files.

journalmatch
specifies the systemd journal match used to filter the journal entries. See journalctl(1) and
systemd.journal-fields(7) for matches syntax and more details on special journal fields. This
option is only valid for the systemd backend.

Filters can also have a section called [INCLUDES]. This is used to read other configuration files.

before indicates that this file is read before the [Definition] section.

after indicates that this file is read after the [Definition] section.

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>,  Daniel  Black
       <daniel.subs@internode.on.net>  and  Steven Hiscocks <steven-fail2ban@hiscocks.me.uk> along with a number
       of contributors.  See THANKS file shipped with Fail2Ban for a full list.  Manual page written  by  Daniel
       Black and Yaroslav Halchenko.

REPORTING BUGS

       Report bugs to https://github.com/fail2ban/fail2ban/issues

COPYRIGHT

       Copyright © 2013 the Fail2Ban Team
       Copyright of modifications held by their respective authors.
       Licensed under the GNU General Public License v2 (GPL) or (at your option) any later version.