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# Fail2Ban filter for sendmail spam/relay type failures
#
# Some of the below failregex will only work properly, when the following
# options are set in the .mc file (see your Sendmail documentation on how
# to modify it and generate the corresponding .cf file):
#
# FEATURE(`delay_checks')
# FEATURE(`greet_pause', `500')
# FEATURE(`ratecontrol', `nodelay', `terminate')
# FEATURE(`conncontrol', `nodelay', `terminate')
#
# ratecontrol and conncontrol also need corresponding options ClientRate:
# and ClientConn: in the access file, see documentation for ratecontrol and
# conncontrol in the sendmail/cf/README file.
[INCLUDES]
before = common.conf
[Definition]
_daemon = (?:(sm-(mta|acceptingconnections)|sendmail))
__prefix_line = %(known/__prefix_line)s(?:\w{14,20}: )?
addr = (?:(?:IPv6:)?<IP6>|<IP4>)
prefregex = ^<F-MLFID>%(__prefix_line)s</F-MLFID><F-CONTENT>.+</F-CONTENT>$
cmnfailre = ^ruleset=check_rcpt, arg1=(?P<email><\S+@\S+>), relay=(\S+ )?\[%(addr)s\](?: \(may be forged\))?, reject=(?:550 5\.7\.1(?: (?P=email)\.\.\.)?(?: Relaying denied\.)? (?:IP name possibly forged \[(\d+\.){3}\d+\]|Proper authentication required\.|IP name lookup failed \[(\d+\.){3}\d+\]|Fix reverse DNS for \S+)|553 5\.1\.8(?: (?P=email)\.\.\.)? Domain of sender address \S+ does not exist|550 5\.[71]\.1 (?P=email)\.\.\. (Rejected: .*|User unknown))$
^ruleset=check_relay(?:, arg\d+=\S*)*, relay=(\S+ )?\[%(addr)s\](?: \(may be forged\))?, reject=421 4\.3\.2 (Connection rate limit exceeded\.|Too many open connections\.)$
^rejecting commands from (\S* )?\[%(addr)s\] due to pre-greeting traffic after \d+ seconds$
^(?:\S+ )?\[%(addr)s\]: (?:(?i)expn|vrfy) \S+ \[rejected\]$
^<[^@]+@[^>]+>\.\.\. No such user here$
^<F-NOFAIL>from=<[^@]+@[^>]+></F-NOFAIL>, size=\d+, class=\d+, nrcpts=\d+, bodytype=\w+, proto=E?SMTP, daemon=MTA, relay=\S+ \[%(addr)s\]$
mdre-normal =
mdre-extra = ^(?:\S+ )?\[%(addr)s\](?: \(may be forged\))? did not issue \S+ during connection
mdre-aggressive = %(mdre-extra)s
failregex = %(cmnfailre)s
<mdre-<mode>>
# Parameter "mode": normal (default), extra or aggressive
# Usage example (for jail.local):
# [sendmail-reject]
# filter = sendmail-reject[mode=extra]
#
mode = normal
ignoreregex =
journalmatch = SYSLOG_IDENTIFIER=sm-mta + _SYSTEMD_UNIT=sendmail.service
# DEV NOTES:
#
# Regarding the multiline regex:
#
# "No such user" lines generate a failure and needs to be matched together with
# another line with the HOST, therefore no-failure line was added as regex, that
# contains HOST (see line with tag <F-NOFAIL>).
#
# Note the capture <F-MLFID>, includes both the __prefix_lines (which includes
# the sendmail PID), but also the `\w{14}` which the the sendmail assigned
# mail ID (todo: check this is necessary, possible obsolete).
#
# Author: Daniel Black, Fabian Wenk and Sergey Brester aka sebres.
# Rewritten using prefregex by Serg G. Brester.
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