| JAIL.CONF(5) | Fail2Ban Configuration | JAIL.CONF(5) |
jail.conf - configuration for the fail2ban server
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
Fail2ban has four configuration file types:
*.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
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.
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:
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
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]:
Using Python "string interpolation" mechanisms, other definitions are allowed and can later be used within other definitions as %(name)s.
Fail2ban has more advanced syntax (similar python extended
interpolation). This extended interpolation is using
%(section/parameter)s to denote a value from a foreign section.
Besides cross section interpolation the value of parameter in [DEFAULT]
section can be retrieved with %(default/parameter)s.
Fail2ban supports also another feature named %(known/parameter)s (means
last known option with name parameter). This interpolation makes
possible to extend a stock filter or jail regexp in .local file (opposite to
simply set failregex/ignoreregex that overwrites it), e.g.
baduseragents = IE|wget|%(my-settings/baduseragents)s
failregex = %(known/failregex)s
useragent=%(baduseragents)s
Additionally to interpolation %(known/parameter)s, that does not works for filter/action init parameters, an interpolation tag <known/parameter> can be used (means last known init definition of filters or actions with name parameter). This interpolation makes possible to extend a parameters of stock filter or action directly in jail inside jail.conf/jail.local file without creating a separately filter.d/*.local file, e.g.
[Init] test.method = GET baduseragents = IE|wget [Definition] failregex = ^%(__prefix_line)\s+"<test.method>"\s+test\s+regexp\s+-\s+useragent=(?:<baduseragents>) # jail.local: [test] # use filter "test", overwrite method to "POST" and extend known bad agents with "badagent": filter = test[test.method=POST, baduseragents="badagent|<known/baduseragents>"]
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.
The items that can be set in section [Definition] are:
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.
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.
If this option is not specified, log lines from which no explicit time zone has been found are interpreted by fail2ban in its own system time zone, and that may turn to be inappropriate. While the best practice is to configure the monitored applications to include explicit offsets, this option is meant to handle cases where that is not possible.
The supported time zones in this option are those with fixed offset: Z, UTC[+-]hhmm (you can also use GMT as an alias to UTC).
This option has no effect on log lines on which an explicit time zone has been found. Examples:
logtimezone = UTC
logtimezone = UTC+0200
logtimezone = GMT-0100
[name=value,name2=value,name3="values,values"]
ignorecache = key="<F-USER>@<ip-host>", max-count=100, max-time=5m
ignorecommand = if [ "<F-USER>" = "technical" ] && [ "<ip-host>" = "my-host.example.com" ]; then exit 0; fi;
exit 1
This will cache the result of ignorecommand (does not call it repeatedly)
for 5 minutes (cache time) for maximal 100 entries (cache size), using values
substituted like "user@host" as cache-keys. Set option
ignorecache to empty value disables the cache.Available options are listed below.
backend = systemd[journalpath=/run/log/journal/machine-1] backend = systemd[journalfiles="/path/to/system.journal, /path/to/user.journal"] backend = systemd[journalflags=1]
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]
The time entries in fail2ban configuration (like findtime or bantime) can be provided as integer in seconds or as string using special abbreviation format (e. g. 600 is the same as 10m).
years?, yea?, yy? months?, mon? weeks?, wee?, ww? days?, da, dd? hours?, hou?, hh? minutes?, min?, mm? seconds?, sec?, ss? The question mark (?) means the optional character, so day as well as days can be used.
You can combine multiple tokens in format (separated with space
resp. without separator), e. g.: 1y 6mo or 1d12h30m.
Note that tokens m as well as mm means minutes, for month use
abbreviation mo or mon.
The time format can be tested using fail2ban-client:
fail2ban-client --str2sec 1d12h
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.
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:
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
The following tags are substituted in the actionban, actionunban and actioncheck (when called before actionban/actionunban) commands.
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 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 several standard filter definitions used in the [Definition] section:
prefregex = ^%(__prefix_line)s (?:ERROR|FAILURE) <F-CONTENT>.+</F-CONTENT>$
failregex = ^user not found
^authentication failed
^unknown authentication method
For example <F-USER>[^@]+</F-USER> matches and stores a user name, that can be used in action with interpolation tag <F-USER>.
<F-ALT_*n>...</F-ALT_*n> - free regex capturing alternative named group stored in ticket.
For example first found matched value defined in regex as <F-ALT_USER>, <F-ALT_USER1> or <F-ALT_USER2> would be stored as <F-USER> (if direct match is not found or empty).
Every of abovementioned tags can be specified in prefregex and in failregex, thereby if specified in both, the value matched in failregex overwrites a value matched in prefregex.
NOTE: the failregex will be applied to the remaining part of message after prefregex processing (if specified), which in turn takes place after datepattern processing (whereby the string of timestamp matching the best pattern, cut out from the message).
For multiline regexs (parsing with maxlines greater that 1) the tag <SKIPLINES> can 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.
This is an obsolete handling and if the lines contain some common identifier, better would be to use new handling (with tags <F-MLFID>...<F-MLFID/>).
is the regex to identify log entries that should be ignored by Fail2Ban, even if they match failregex.
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.
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.
NOTE: due to config file string substitution, that %'s must be escaped by an % in config files.
Also, special values of Epoch (UNIX Timestamp), TAI64N and ISO8601 can be used as datepattern.
Normally the regexp generated for datepattern additionally gets word-start and word-end boundaries to avoid accidental match inside of some word in a message. There are several prefixes and words with special meaning that could be specified with custom datepattern to control resulting regex:
{DEFAULT} - can be used to add default date patterns of fail2ban.
{DATE} - can be used as part of regex that will be replaced with default date patterns.
{^LN-BEG} - prefix (similar to ^) changing word-start boundary to line-start boundary (ignoring up to 2 characters). If used as value (not as a prefix), it will also set all default date patterns (similar to {DEFAULT}), but anchored at begin of message line.
{UNB} - prefix to disable automatic word boundaries in regex.
{NONE} - value would allow one to find failures totally without date-time in log message. Filter will use now as a timestamp (or last known timestamp from previous line with timestamp).
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.
Similar to actions, filters may have an [Init] section also (optional since v.0.10). All parameters of both sections [Definition] and [Init] can be overridden (redefined or extended) in jail.conf or jail.local (or in related filter.d/filter-name.local). Every option supplied in the jail to the filter overwrites the value specified in [Init] section, which in turm would overwrite the value in [Definition] section. Besides the standard settings of filter both sections can be used to initialize filter-specific options. Filters can also have a section called [INCLUDES]. This is used to read other configuration files.
indicates that this file is read before the [Definition] section.
indicates that this file is read after the [Definition] section.
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.
Report bugs to https://github.com/fail2ban/fail2ban/issues
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.
fail2ban-server(1)
| November 2015 | Fail2Ban |