¡El misterio de fail2ban!
Todo parece funcionar y estar bien configurado, pero el servidor aún recibe intentos de conexión.
[moso@matrix ~]$ sudo systemctl status fail2ban
● fail2ban.service - Fail2Ban Service
Loaded: loaded (/usr/lib/systemd/system/fail2ban.service; enabled; vendor preset: disabled)
Active: active (running) since Sat 2022-04-16 22:10:45 -03; 13h ago
Docs: man:fail2ban(1)
Process: 332 ExecStartPre=/bin/mkdir -p /run/fail2ban (code=exited, status=0/SUCCESS)
Main PID: 335 (fail2ban-server)
Tasks: 5 (limit: 19183)
Memory: 17.9M
CPU: 1min 945ms
CGroup: /system.slice/fail2ban.service
└─335 /usr/bin/python /usr/bin/fail2ban-server -xf start
Apr 16 22:10:45 matrix systemd[1]: Starting Fail2Ban Service...
Apr 16 22:10:45 matrix systemd[1]: Started Fail2Ban Service.
Apr 16 22:10:45 matrix fail2ban-server[335]: Server ready
[moso@matrix ~]$ sudo cat /etc/fail2ban/jail.d/sshd.local
[sshd]
enabled = true
filter = sshd
banaction = iptables
backend = systemd
maxretry = 3
findtime = 1d
bantime = 2w
ignoreip = 127.0.0.1/8 x1.y1.z1.w1/32 x2.y2.z2.w2/32
[moso@matrix ~]$ sudo fail2ban-client status sshd
Status for the jail: sshd
|- Filter
| |- Currently failed: 1
| |- Total failed: 10
| `- Journal matches: _SYSTEMD_UNIT=sshd.service + _COMM=sshd
`- Actions
|- Currently banned: 1
|- Total banned: 1
`- Banned IP list: 179.43.156.154
[moso@matrix ~]$ sudo iptables -L -n | grep 179.43.156.154
REJECT all -- 179.43.156.154 0.0.0.0/0 reject-with icmp-port-unreachable
[moso@matrix ~]$ sudo cat /var/log/fail2ban.log
2022-04-16 22:10:45,655 fail2ban.server [335]: INFO Starting Fail2ban v0.11.2
2022-04-16 22:10:45,657 fail2ban.observer [335]: INFO Observer start...
2022-04-16 22:10:45,667 fail2ban.database [335]: INFO Connected to fail2ban persistent database '/var/lib/fail2ban/fail2ban.sqlite3'
2022-04-16 22:10:45,670 fail2ban.database [335]: WARNING New database created. Version '4'
2022-04-16 22:10:45,670 fail2ban.jail [335]: INFO Creating new jail 'sshd'
2022-04-16 22:10:45,706 fail2ban.jail [335]: INFO Jail 'sshd' uses systemd {}
2022-04-16 22:10:45,706 fail2ban.jail [335]: INFO Initiated 'systemd' backend
2022-04-16 22:10:45,707 fail2ban.filter [335]: INFO maxLines: 1
2022-04-16 22:10:45,723 fail2ban.filtersystemd [335]: INFO [sshd] Added journal match for: '_SYSTEMD_UNIT=sshd.service + _COMM=sshd'
2022-04-16 22:10:45,723 fail2ban.filter [335]: INFO maxRetry: 3
2022-04-16 22:10:45,723 fail2ban.filter [335]: INFO findtime: 86400
2022-04-16 22:10:45,724 fail2ban.actions [335]: INFO banTime: 1209600
2022-04-16 22:10:45,724 fail2ban.filter [335]: INFO encoding: UTF-8
2022-04-16 22:10:45,725 fail2ban.jail [335]: INFO Jail 'sshd' started
2022-04-16 22:53:09,239 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-16 22:53:08
2022-04-17 00:33:22,995 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 00:33:22
2022-04-17 01:31:38,980 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 01:31:38
2022-04-17 01:31:39,266 fail2ban.actions [335]: NOTICE [sshd] Ban 179.43.156.154
2022-04-17 02:58:45,765 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 02:58:45
2022-04-17 05:40:59,243 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 05:40:58
2022-04-17 07:13:51,766 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 07:13:51
2022-04-17 07:13:52,130 fail2ban.actions [335]: WARNING [sshd] 179.43.156.154 already banned
2022-04-17 07:49:33,667 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 07:49:33
2022-04-17 08:20:44,205 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 08:20:44
2022-04-17 08:44:07,980 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 08:44:07
2022-04-17 08:44:08,129 fail2ban.actions [335]: WARNING [sshd] 179.43.156.154 already banned
2022-04-17 09:44:54,464 fail2ban.filter [335]: INFO [sshd] Found 179.43.156.154 - 2022-04-17 09:44:54
...
[moso@matrix ~]$ journalctl _SYSTEMD_UNIT=sshd.service
Apr 16 22:10:15 matrix sshd[151093]: Received signal 15; terminating.
-- Boot aa222dfff23f467ab30cd5125c7c3a55 --
Apr 16 22:10:45 matrix sshd[333]: Server listening on 0.0.0.0 port 2206.
Apr 16 22:53:08 matrix sshd[656]: Connection from 179.43.156.154 port 40138 on 38.105.209.109 port 2206 rdomain ""
Apr 16 22:53:08 matrix sshd[656]: Invalid user root root from 179.43.156.154 port 40138
Apr 16 22:53:08 matrix sshd[656]: Connection closed by invalid user root root 179.43.156.154 port 40138 [preauth]
Apr 17 00:33:22 matrix sshd[685]: Connection from 179.43.156.154 port 34498 on 38.105.209.109 port 2206 rdomain ""
Apr 17 00:33:22 matrix sshd[685]: Invalid user root root from 179.43.156.154 port 34498
Apr 17 00:33:22 matrix sshd[685]: Connection closed by invalid user root root 179.43.156.154 port 34498 [preauth]
Apr 17 01:31:38 matrix sshd[699]: Connection from 179.43.156.154 port 59372 on 38.105.209.109 port 2206 rdomain ""
Apr 17 01:31:38 matrix sshd[699]: Invalid user root root from 179.43.156.154 port 59372
Apr 17 01:31:38 matrix sshd[699]: Connection closed by invalid user root root 179.43.156.154 port 59372 [preauth]
Apr 17 02:58:44 matrix sshd[722]: Connection from 179.43.156.154 port 57448 on 38.105.209.109 port 2206 rdomain ""
Apr 17 02:58:45 matrix sshd[722]: Invalid user root root from 179.43.156.154 port 57448
Apr 17 02:58:45 matrix sshd[722]: Connection closed by invalid user root root 179.43.156.154 port 57448 [preauth]
Apr 17 05:40:58 matrix sshd[760]: Connection from 179.43.156.154 port 54992 on 38.105.209.109 port 2206 rdomain ""
Apr 17 05:40:58 matrix sshd[760]: Invalid user root root from 179.43.156.154 port 54992
Apr 17 05:40:58 matrix sshd[760]: Connection closed by invalid user root root 179.43.156.154 port 54992 [preauth]
Apr 17 07:13:51 matrix sshd[777]: Connection from 179.43.156.154 port 59646 on 38.105.209.109 port 2206 rdomain ""
Apr 17 07:13:51 matrix sshd[777]: Invalid user root root from 179.43.156.154 port 59646
Apr 17 07:13:51 matrix sshd[777]: Connection closed by invalid user root root 179.43.156.154 port 59646 [preauth]
Apr 17 07:49:33 matrix sshd[789]: Connection from 179.43.156.154 port 33684 on 38.105.209.109 port 2206 rdomain ""
Apr 17 07:49:33 matrix sshd[789]: Invalid user root root from 179.43.156.154 port 33684
Apr 17 07:49:33 matrix sshd[789]: Connection closed by invalid user root root 179.43.156.154 port 33684 [preauth]
Apr 17 08:20:43 matrix sshd[801]: Connection from 179.43.156.154 port 55522 on 38.105.209.109 port 2206 rdomain ""
Apr 17 08:20:44 matrix sshd[801]: Invalid user root root from 179.43.156.154 port 55522
Apr 17 08:20:44 matrix sshd[801]: Connection closed by invalid user root root 179.43.156.154 port 55522 [preauth]
Apr 17 08:44:07 matrix sshd[805]: Connection from 179.43.156.154 port 39862 on 38.105.209.109 port 2206 rdomain ""
Apr 17 08:44:07 matrix sshd[805]: Invalid user root root from 179.43.156.154 port 39862
Apr 17 08:44:07 matrix sshd[805]: Connection closed by invalid user root root 179.43.156.154 port 39862 [preauth]
Apr 17 09:44:54 matrix sshd[822]: Connection from 179.43.156.154 port 42592 on 38.105.209.109 port 2206 rdomain ""
Apr 17 09:44:54 matrix sshd[822]: Invalid user root root from 179.43.156.154 port 42592
Apr 17 09:44:54 matrix sshd[822]: Connection closed by invalid user root root 179.43.156.154 port 42592 [preauth]
...
¿Por qué IP 179.43.156.154 continúa intentando conectarse si fail2ban parece funcionar Y cualquier conexión desde 179.43.156.154 debe rechazarse? (ver salida de iptables arriba)
Respuesta1
El problema era... ¡yo!
Supuse erróneamente que fail2ban prohibió el puerto detectado (como se mostró arriba, 2206).
Otra cosa que me llevó a una conclusión equivocada fue el resultado de sudo iptables -L -n | grep 179.43.156.154.
REJECT all -- 179.43.156.154 0.0.0.0/0 reject-with icmp-port-unreachable
No considero en qué cadena estaba la regla...
Solo agregué una línea con el puerto que estoy usando en sshd y el problema (causado por mí) se resolvió.
[peracchi@matrix ~]$ cat /etc/fail2ban/jail.d/sshd.local
[sshd]
enabled = true
filter = sshd
port = 2206
banaction = iptables
backend = systemd
maxretry = 5
findtime = 1d
bantime = 30d
ignoreip = 127.0.0.1/8 a.b.c.d/32 x.y.z.w/32
"Es imposible que un hombre aprenda lo que cree que ya sabe."- Epicteto