So I'm running a docker server with an nginx container reverse-proxing a bunch of other containers. On the host, I want to use fail2ban to ban IPs trying to break into wordpress websites. Pretty simple, but I need to use a custom action so the ban takes place in the DOCKER-USER chain, otherwise the docker forwards (which also use iptables) override the bans. In order to achieve this I mount the nginx logs directory from the host to the container so fail2ban can watch them from the host.
Everything seems to be working just fine, except for the fact that it's not banning any IPs. The regex matches correctly in tests, banning manually works just fine, the fail2ban logs shows no weirdness; I'm stumped.
Here's an obfuscated/anonymized excerpt from the accesslog;
132.321.555.777 - - [24/Mar/2025:17:12:07 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:07 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:07 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:08 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:08 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
84.29.333.555 - - [24/Mar/2025:17:12:08 +0000] "GET /wp-content/uploads/2024/06/xx-32x32.png HTTP/1.1" 200 926 "-" "NetworkingExtension/8620.2.4.10.8 Network/4277.82.1 iOS/18.3.2"
84.29.333.555 - - [24/Mar/2025:17:12:08 +0000] "GET /wp-content/uploads/2024/06/xx-180x180.png HTTP/1.1" 200 5567 "-" "NetworkingExtension/8620.2.4.10.8 Network/4277.82.1 iOS/18.3.2"
132.321.555.777 - - [24/Mar/2025:17:12:09 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:09 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:09 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
132.321.555.777 - - [24/Mar/2025:17:12:10 +0000] "POST //xmlrpc.php HTTP/1.1" 200 423 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36"
43.166.222.22 - - [24/Mar/2025:17:12:02 +0000] "GET / HTTP/1.1" 400 248 "-" "Mozilla/5.0 (iPhone; CPU iPhone OS 13_2_3 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.0.3 Mobile/15E148 Safari/604.1"
84.29.123.32 - - [24/Mar/2025:17:12:08 +0000] "GET /wp-content/uploads/2023/01/xx-300x225.png HTTP/1.1" 200 115438 "-" "NetworkingExtension/8620.2.4.10.8 Network/4277.82.1 iOS/18.3.2"
84.29.123.32 - - [24/Mar/2025:17:12:08 +0000] "GET /wp-content/uploads/2024/06/xx-192x192.png HTTP/1.1" 200 5994 "-" "NetworkingExtension/8620.2.4.10.8 Network/4277.82.1 iOS/18.3.2"
84.29.123.32 - - [24/Mar/2025:17:12:09 +0000] "GET /wp-content/uploads/2024/06/xx-32x32.png HTTP/1.1" 200 926 "-" "NetworkingExtension/8620.2.4.10.8 Network/4277.82.1 iOS/18.3.2"
/etc/fail2ban/jail.local
[nginx-xmlrpc]
enabled = true
filter = nginx-xmlrpc
logpath = /var/dockervolumes/nginx/logs/access.log
maxretry = 1
findtime = 5
bantime = 3600
action = iptables-docker
I set the maxretry and findtime really low for testing but that didn't help.
/etc/fail2ban/filter.d/nginx-xmlrpc.conf
[INCLUDES]
before = nginx-bad-request.conf
[Definition]
failregex = ^<HOST>.] "POST (|.)/xmlrpc.php.*
^<HOST>.] "GET (|.)/xmlrpc.php.*
^<HOST> .* "POST .wp-login.php
ignoreregex = ^<HOST>.] "POST (|.)/xmlrpc.php?for=jetpack.
datepattern = ^[^\[]*[({DATE})
{^LN-BEG}
As you can see I already tried messing with the date pattern but that didn't help.
/etc/fail2ban/action.d/iptables-docker.conf
[Definition]
actionstart =
actionstop =
actioncheck = /usr/sbin/iptables -n -L DOCKER-USER | grep -q '[<ip>]'
actionban = /usr/sbin/iptables -I DOCKER-USER -s <ip> -j DROP
actionunban = /usr/sbin/iptables -D DOCKER-USER -s <ip> -j DROP
Testing the regex; fail2ban-regex /var/dockervolumes/nginx/logs/access.log /etc/fail2ban/filter.d/nginx-xmlrpc.conf
Running tests
=============
Use failregex filter file : nginx-xmlrpc, basedir: /etc/fail2ban
Use datepattern : ^[^\[]*[({DATE})
{^LN-BEG} : Default Detectors
Use log file : /var/dockervolumes/nginx/logs/access.log
Use encoding : UTF-8
Results
Failregex: 13345 total
|- #) [# of hits] regular expression
| 1) [13299] ^<HOST>.] "POST (|.)/xmlrpc.php.*
| 2) [20] ^<HOST>.] "GET (|.)/xmlrpc.php.*
| 3) [26] ^<HOST> .* "POST .*wp-login.php
`-
Ignoreregex: 0 total
Date template hits:
|- [# of hits] date format
| [26486] ^[^\[]*[(Day(?P<_sep>[-/])MON(?P=_sep)ExYear[ :]?24hour:Minute:Second(?:.Microseconds)?(?: Zone offset)?)
`-
Lines: 26486 lines, 0 ignored, 13345 matched, 13141 missed
[processed in 2.39 sec]
Testing the ban manually; fail2ban-client set nginx-xmlrpc banip 1.2.5.9
Produces log:
2025-03-24 19:09:35,909 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Ban 1.2.5.9
And correctly lists the blocked ip; iptables -L DOCKER-USER
Chain DOCKER-USER (1 references)
target prot opt source destination
DROP all -- 1.2.5.9 anywhere
DROP all -- 1.2.4.9 anywhere
DROP all -- 1.2.3.9 anywhere
DROP all -- 1.2.3.8 anywhere
DROP all -- 1.2.3.7 anywhere
DROP all -- 1.2.3.6 anywhere
DROP all -- 1.2.3.5 anywhere
RETURN all -- anywhere anywhere
The log shows no further weirdness either; tail -f /var/log/fail2ban.log
2025-03-24 19:00:29,067 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Restore Ban 1.2.3.5
2025-03-24 19:00:29,080 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Restore Ban 1.2.3.6
2025-03-24 19:00:29,094 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Restore Ban 1.2.3.7
2025-03-24 19:00:29,104 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Restore Ban 1.2.3.8
2025-03-24 19:00:29,115 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Restore Ban 1.2.3.9
2025-03-24 19:00:29,126 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Restore Ban 1.2.4.9
2025-03-24 19:00:29,240 fail2ban.filtersystemd [828254]: INFO [nginx-xmlrpc] Jail is in operation now (process new journal entries)
2025-03-24 19:05:53,278 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Unban 1.2.3.4
2025-03-24 19:09:33,024 fail2ban.actions [828254]: WARNING [nginx-xmlrpc] 1.2.4.9 already banned
2025-03-24 19:09:35,909 fail2ban.actions [828254]: NOTICE [nginx-xmlrpc] Ban 1.2.5.9
UPDATE:
~ fail2ban-client status nginx-xmlrpc
Status for the jail: nginx-xmlrpc
|- Filter
| |- Currently failed: 0
| |- Total failed: 0
| `- Journal matches: _SYSTEMD_UNIT=nginx.service + _COMM=nginx
`- Actions
|- Currently banned: 0
|- Total banned: 8
`- Banned IP list:
Those 8 bans were my manual tests.
~ iptables-save
*filter
:INPUT ACCEPT [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
:DOCKER - [0:0]
:DOCKER-ISOLATION-STAGE-1 - [0:0]
:DOCKER-ISOLATION-STAGE-2 - [0:0]
:DOCKER-USER - [0:0]
-A FORWARD -j DOCKER-USER
-A FORWARD -j DOCKER-ISOLATION-STAGE-1
-A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o docker0 -j DOCKER
-A FORWARD -i docker0 ! -o docker0 -j ACCEPT
-A FORWARD -i docker0 -o docker0 -j ACCEPT
-A FORWARD -o br-51ec37449070 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -o br-51ec37449070 -j DOCKER
-A FORWARD -i br-51ec37449070 ! -o br-51ec37449070 -j ACCEPT
-A FORWARD -i br-51ec37449070 -o br-51ec37449070 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2020 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2019 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2018 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2017 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2016 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2015 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2014 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2013 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2012 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2011 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2010 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2009 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2008 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2007 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2006 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2005 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2004 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2003 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2002 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2001 -j ACCEPT
-A DOCKER -d 172.18.0.39/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 2000 -j ACCEPT
-A DOCKER -d 172.18.0.6/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 443 -j ACCEPT
-A DOCKER -d 172.18.0.6/32 ! -i br-51ec37449070 -o br-51ec37449070 -p tcp -m tcp --dport 80 -j ACCEPT
-A DOCKER-ISOLATION-STAGE-1 -i docker0 ! -o docker0 -j DOCKER-ISOLATION-STAGE-2
-A DOCKER-ISOLATION-STAGE-1 -i br-51ec37449070 ! -o br-51ec37449070 -j DOCKER-ISOLATION-STAGE-2
-A DOCKER-ISOLATION-STAGE-1 -j RETURN
-A DOCKER-ISOLATION-STAGE-2 -o docker0 -j DROP
-A DOCKER-ISOLATION-STAGE-2 -o br-51ec37449070 -j DROP
-A DOCKER-ISOLATION-STAGE-2 -j RETURN
-A DOCKER-USER -s 1.14.96.192/32 -j DROP
-A DOCKER-USER -s 18.219.14.219/32 -j DROP
-A DOCKER-USER -s 174.138.27.210/32 -j DROP
-A DOCKER-USER -s 128.199.244.121/32 -j DROP
-A DOCKER-USER -s 45.130.145.4/32 -j DROP
-A DOCKER-USER -s 128.199.244.121/32 -j DROP
-A DOCKER-USER -j RETURN
COMMIT
# Completed on Wed Mar 26 09:10:19 2025
# Generated by iptables-save v1.8.10 (nf_tables) on Wed Mar 26 09:10:19 2025
*nat
:PREROUTING ACCEPT [320032242:19224216945]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [396346224:30027564903]
:POSTROUTING ACCEPT [531692826:38140531338]
:DOCKER - [0:0]
-A PREROUTING -m addrtype --dst-type LOCAL -j DOCKER
-A OUTPUT ! -d 127.0.0.0/8 -m addrtype --dst-type LOCAL -j DOCKER
-A POSTROUTING -s 172.17.0.0/16 ! -o docker0 -j MASQUERADE
-A POSTROUTING -s 172.18.0.0/16 ! -o br-51ec37449070 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2020 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2019 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2018 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2017 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2016 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2015 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2014 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2013 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2012 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2011 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2010 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2009 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2008 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2007 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2006 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2005 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2004 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2003 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2002 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2001 -j MASQUERADE
-A POSTROUTING -s 172.18.0.39/32 -d 172.18.0.39/32 -p tcp -m tcp --dport 2000 -j MASQUERADE
-A POSTROUTING -s 172.18.0.6/32 -d 172.18.0.6/32 -p tcp -m tcp --dport 443 -j MASQUERADE
-A POSTROUTING -s 172.18.0.6/32 -d 172.18.0.6/32 -p tcp -m tcp --dport 80 -j MASQUERADE
-A DOCKER -i docker0 -j RETURN
-A DOCKER -i br-51ec37449070 -j RETURN
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2020 -j DNAT --to-destination 172.18.0.39:2020
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2019 -j DNAT --to-destination 172.18.0.39:2019
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2018 -j DNAT --to-destination 172.18.0.39:2018
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2017 -j DNAT --to-destination 172.18.0.39:2017
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2016 -j DNAT --to-destination 172.18.0.39:2016
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2015 -j DNAT --to-destination 172.18.0.39:2015
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2014 -j DNAT --to-destination 172.18.0.39:2014
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2013 -j DNAT --to-destination 172.18.0.39:2013
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2012 -j DNAT --to-destination 172.18.0.39:2012
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2011 -j DNAT --to-destination 172.18.0.39:2011
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2010 -j DNAT --to-destination 172.18.0.39:2010
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2009 -j DNAT --to-destination 172.18.0.39:2009
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2008 -j DNAT --to-destination 172.18.0.39:2008
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2007 -j DNAT --to-destination 172.18.0.39:2007
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2006 -j DNAT --to-destination 172.18.0.39:2006
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2005 -j DNAT --to-destination 172.18.0.39:2005
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2004 -j DNAT --to-destination 172.18.0.39:2004
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2003 -j DNAT --to-destination 172.18.0.39:2003
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2002 -j DNAT --to-destination 172.18.0.39:2002
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2001 -j DNAT --to-destination 172.18.0.39:2001
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 2000 -j DNAT --to-destination 172.18.0.39:2000
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 443 -j DNAT --to-destination 172.18.0.6:443
-A DOCKER ! -i br-51ec37449070 -p tcp -m tcp --dport 80 -j DNAT --to-destination 172.18.0.6:80
COMMIT
# Completed on Wed Mar 26 09:10:19 2025
