jail.conf0 - Online in the Cloud

PROGRAM:

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=[email protected], actname=smtp-chris]
smtp.py[dest=[email protected], 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.

Use jail.conf0 online using onworks.net services