fail2ban/config/filter.d/exim.conf

# Fail2Ban filter for exim
#
# This includes the rejection messages of exim. For spam and filter
# related bans use the exim-spam.conf
#


[INCLUDES]

# Read common prefixes. If any customizations available -- read them from
# exim-common.local
before = exim-common.conf

[Definition]

# Fre-filter via "prefregex" is currently inactive because of too different failure syntax in exim-log (testing needed):
#prefregex = ^%(pid)s <F-CONTENT>\b(?:\w+ authenticator failed|([\w\-]+ )?SMTP (?:(?:call|connection) from|protocol(?: synchronization)? error)|no MAIL in|(?:%(host_info_pre)s\[[^\]]+\]%(host_info_suf)s(?:sender verify fail|rejected RCPT|dropped|AUTH command))).+</F-CONTENT>$

failregex = ^%(pid)s %(host_info)ssender verify fail for <\S+>: (?:Unknown user|Unrouteable address|all relevant MX records point to non-existent hosts)\s*$
            ^%(pid)s \w+ authenticator failed for (?:[^\[\( ]* )?(?:\(\S*\) )?\[<HOST>\](?::\d+)?(?: I=\[\S+\](:\d+)?)?: 535 Incorrect authentication data( \(set_id=.*\)|: \d+ Time\(s\))?\s*$
            ^%(pid)s %(host_info)srejected RCPT [^@]+@\S+: (?:relay not permitted|Sender verify failed|Unknown user|Unrouteable address)\s*$
            ^%(pid)s SMTP protocol synchronization error \([^)]*\): rejected (?:connection from|"\S+") %(host_info)s(?:next )?input=".*"\s*$
            ^%(pid)s SMTP call from (?:[^\[\( ]* )?%(host_info)sdropped: too many (?:(?:nonmail|unrecognized) commands|syntax or protocol errors)
            ^%(pid)s SMTP protocol error in "[^"]+(?:"+[^"]*(?="))*?" %(host_info)sAUTH command used when not advertised\s*$
            ^%(pid)s no MAIL in SMTP connection from (?:[^\[\( ]* )?(?:\(\S*\) )?%(host_info)sD=\d\S*s(?: C=\S*)?\s*$
            ^%(pid)s (?:[\w\-]+ )?SMTP connection from (?:[^\[\( ]* )?(?:\(\S*\) )?%(host_info)sclosed by DROP in ACL\s*$
            <mdre-<mode>>

mdre-aggressive = ^%(pid)s no host name found for IP address <HOST>$
                  ^%(pid)s no IP address found for host \S+ \(during SMTP connection from \[<HOST>\]\)$

mdre-normal = 

# Parameter `mode` - `normal` or `aggressive`.
# Aggressive mode can be used to match flood and ddos-similar log-entries like:
#   'no host found for IP', 'no IP found for host'.
# Note this is not an authentication failures, so it may produce lots of false 
# positives on misconfigured MTAs.
# Ex.:
#   filter = exim[mode=aggressive]
mode = normal

ignoreregex = 

# DEV Notes:
# The %(host_info) definition contains a <HOST> match
#
# SMTP protocol synchronization error \([^)]*\)  <- This needs to be non-greedy
# to void capture beyond ")" to avoid a DoS Injection vulnerability as input= is
# user injectable data.
#
# Author: Cyril Jaquier
#         Daniel Black (rewrote with strong regexs)
#         Martin O'Neal (added additional regexs to detect authentication failures, protocol errors, and drops)