手動解除 fail2ban 封鎖的 IP

因為常常發現更換密碼後, 來不及更改 client 端, 一下子 client 端的 IP 就被列入封鎖, 重新啟動 iptable , fail2ban 還是馬上會倍加回封鎖清單內, 因此找到以下的作法.

• 假設以下是已經被 ban 的 iptables 清單

  iptables --list

  Chain INPUT (policy ACCEPT)
  target     prot opt source               destination
  fail2ban-SSH  tcp  --  anywhere             anywhere            tcp dpt:ssh
  fail2ban-dovecot  tcp  --  anywhere             anywhere            multiport dports pop3,pop3s,imap,imaps,submission,urd,sieve
  fail2ban-dovecot-auth  tcp  --  anywhere             anywhere            multiport dports pop3,pop3s,imap,imaps,submission,urd,sieve
  fail2ban-sendmail-smtp  tcp  --  anywhere             anywhere            multiport dports smtp
  ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
  ACCEPT     icmp --  anywhere             anywhere
  :
  :
  Chain fail2ban-dovecot-auth (1 references)
  target     prot opt source               destination
  RETURN     all  --  anywhere             anywhere
  
  Chain fail2ban-sendmail-smtp (1 references)
  target     prot opt source               destination
  REJECT     all  --  192.168.0.120        anywhere            reject-with icmp-port-unreachable
  REJECT     all  --  176.61.137.108       anywhere            reject-with icmp-port-unreachable
  RETURN     all  --  anywhere             anywhere

• 打算將 fail2ban-sendmail-smtp 內 192.168.0.120 手動解除封鎖

• 並沒有成功.. 應該是要定義 action unban 的作用功能

  fail2ban-client get sendmail-smtp actionunban 192.168.0.120

  ERROR  NOK: ('Invalid Action name',)
  'Invalid Action name'

• 有成功..

  iptables -D fail2ban-sendmail-smtp 1
  iptables --list

  :
  :
  Chain fail2ban-sendmail-smtp (1 references)
  target     prot opt source               destination
  REJECT     all  --  176.61.137.108       anywhere            reject-with icmp-port-unreachable
  RETURN     all  --  anywhere             anywhere

• 因為特殊原因, 特定 IP 會造成被列入阻絕, 如果希望先開啟這 IP 不要被阻絕, 可透過編輯 jail.conf 內的 ignoreip 來達成
• Exp. 將 127.0.xx.xx 以及 192.168.0.124 加入白名單

  vi /etc/fail2ban/jail.conf

  :
  [DEFAULT]
  
  # "ignoreip" can be an IP address, a CIDR mask or a DNS host. Fail2ban will not
  # ban a host which matches an address in this list. Several addresses can be
  # defined using space separator.
  ignoreip = 127.0.0.1/8 192.168.0.124/24
  
  :

• 重新載入讓設定生效

  service fail2ban reload

• https://www.howtoforge.com/community/threads/how-to-manually-unban-ip-blocked-by-fail2ban.51366/