Fail2ban

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Revision as of 20:16, 31 March 2024 by Ebroch (talk | contribs)
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Install fail2ban
# yum install fail2ban -y
Create the filter definition files in filter.d # cat >/etc/fail2ban/filter.d/qmail-smtp-authnotavail.conf << EOL [Definition] #Looks for failed auth outside TLS to SMTP failregex = 503 auth not available \(\#5\.3\.3\) - <HOST> ignoreregex = EOL
# cat >/etc/fail2ban/filter.d/qmail-smtps-passfail.conf<< EOL [Definition] #Looks for failed password logins to SMTP failregex = vchkpw-smtps: password fail ([^)]*) [^@]*@[^:]*:<HOST> ignoreregex = EOL
# cat >/etc/fail2ban/filter.d/qmail-smtps-usernotfound.conf<< EOL [Definition] failregex = vchkpw-smtps: vpopmail user not found .*:<HOST> ignoreregex = EOL
# cat >/etc/fail2ban/filter.d/qmail-submission-passfail.conf<< EOL [Definition] failregex = vchkpw-submission: password fail ([^)]*) [^@]*@[^:]*:<HOST> ignoreregex = EOL
# cat >/etc/fail2ban/filter.d/qmail-submission-usernotfound.conf<< EOL [Definition] failregex = vchkpw-submission: vpopmail user not found .*:<HOST> ignoreregex = EOL
Create jail.local # cat >>/etc/fail2ban/jail.d/jail.local << EOL [qmail-submission-passfail] enabled = true filter = qmail-submission-passfail action = iptables[name=QMAIL-SUBMISSION, port=587, protocol=tcp] logpath = /var/log/maillog maxretry = 3 bantime = 86400 findtime = 3600 backend = auto
[qmail-submission-usernotfound] enabled = true filter = qmail-submission-usernotfound action = iptables[name=QMAIL-SUBMISSION, port=587, protocol=tcp] logpath = /var/log/maillog maxretry = 3 bantime = 86400 findtime = 3600 backend = auto
[qmail-smtps-passfail] enabled = true filter = qmail-smtps-passfail action = iptables[name=QMAIL-SMTPS, port=465, protocol=tcp] logpath = /var/log/maillog maxretry = 3 bantime = 86400 findtime = 3600 backend = auto
[qmail-smtps-usernotfound] enabled = true filter = qmail-smtps-usernotfound action = iptables[name=QMAIL-SMTPS, port=465, protocol=tcp] logpath = /var/log/maillog maxretry = 3 bantime = 86400 findtime = 3600 backend = auto
[qmail-smtp-authnotavail] enabled = true filter = qmail-smtp-authnotavail action = iptables[name=QMAIL-SMTP, port=25, protocol=tcp] logpath = /var/log/qmail/smtptx/current (This log path will require /var/qmail/supervise/smtp/log/run to be edited (below) or f2b will not start) #logpath = /var/log/qmail/smtp/current maxretry = 3 bantime = 86400 findtime = 300 backend = auto
EOL
In order to log SMTPTX (transactions) do the following:
 1) # qmailctl stop
 2) Add 'SMTP_DEBUG="1"' to /etc/tcprules.d/tcp.smtp 
 3) Replace contents of '/var/qmail/supervise/smtp/log/run' script with below to log transactions to different file: 
     #!/bin/sh
     LOGSIZE=`cat /var/qmail/control/logsize`
     LOGCOUNT=`cat /var/qmail/control/logcount`
     exec /usr/bin/setuidgid qmaill \
       /usr/bin/multilog t s$LOGSIZE n$LOGCOUNT \
       '-*' '+@* server:[*' '+@* client:[*' /var/log/qmail/smtptx \
       '+*' '-@* server:[*' '-@* client:[*' /var/log/qmail/smtp 2>&1
 4) # qmailctl start && qmailctl cdb
 5) # tail -f /var/log/qmail/smtptx/current | tai64nlocal
Start fail2ban
# systemctl start fail2ban
Script to check blocking
# tee -a /usr/local/bin/f2bstat<<EOL
#!/bin/bash
for FILTER in qmail-submission-passfail \\
             qmail-submission-usernotfound \\
             qmail-smtps-passfail \\
             qmail-smtps-usernotfound \\
             qmail-smtp-authnotavail
do
   fail2ban-client status \$FILTER
   echo ""
done
EOL
Set permissions & run script (w/output sample)
# chmod 755 /usr/local/bin/f2bstat && f2bstat
qmail-submission-passfail:
Status for the jail: qmail-submission-passfail |- Filter | |- Currently failed: 1 | |- Total failed: 1 | `- File list: /var/log/maillog `- Actions |- Currently banned: 0 |- Total banned: 0 `- Banned IP list:
qmail-submission-usernotfound:
Status for the jail: qmail-submission-usernotfound |- Filter | |- Currently failed: 7 | |- Total failed: 7 | `- File list: /var/log/maillog `- Actions |- Currently banned: 0 |- Total banned: 0 `- Banned IP list:
qmail-smtps-passfail:
Status for the jail: qmail-smtps-passfail |- Filter | |- Currently failed: 0 | |- Total failed: 0 | `- File list: /var/log/maillog `- Actions |- Currently banned: 0 |- Total banned: 0 `- Banned IP list:
qmail-smtps-usernotfound:
Status for the jail: qmail-smtps-usernotfound |- Filter | |- Currently failed: 0 | |- Total failed: 0 | `- File list: /var/log/maillog `- Actions |- Currently banned: 2 |- Total banned: 2 `- Banned IP list: 5.34.207.174 212.70.149.72
qmail-smtp-authnotavail:
Status for the jail: qmail-smtp-authnotavail |- Filter | |- Currently failed: 0 | |- Total failed: 0 | `- File list: /var/log/qmail/smtptx/current `- Actions |- Currently banned: 0 |- Total banned: 0 `- Banned IP list:

Note

Basic commands

  • Check banned IPs:
  Format: fail2ban-client get 'jail' banned
        # fail2ban-client get qmail-smtp-authnotavail banned
        ['xxx.xxx.xxx.xxx', 'yyy.yyy.yyy.yyy',...,]
  • How to unblock an IP(s):
  Format: fail2ban-client set 'jail' unbanip xxx.xxx.xxx.xxx yyy.yyy.yyy.yyy ...
        # fail2ban-client set qmail-smtp-authnotavail unbanip 192.168.1.105 192.168.1.112 192.168.1.119
        3
        #
  • How to block an IP(s):
  Format: fail2ban-client set 'jail' unbanip xxx.xxx.xxx.xxx yyy.yyy.yyy.yyy ...
        # fail2ban-client set qmail-smtp-authnotavail banip 192.168.9.105 192.168.1.112 192.168.1.119
        3
        #

References

[1] fail2ban homepage: http://www.fail2ban.org