## Version 2022/08/06
# Fail2Ban configuration file for black-listing via nginx
#
# Author: Serg G. Brester (aka sebres)
#
# To use 'nginx-block-map' action you should define some special blocks in your nginx configuration,
# and use it hereafter in your locations (to notify fail2ban by failure, resp. nginx by ban).
#
# Example (argument "token_id" resp. cookie "session_id" used here as unique identifier for user):
#
#   http {
#     ...
#     # maps to check user is blacklisted (banned in f2b):
#     #map $arg_token_id      $blck_lst_tok { include blacklisted-tokens.map; }
#     map  $cookie_session_id $blck_lst_ses { include blacklisted-sessions.map; }
#     ...
#     # special log-format to notify fail2ban about failures:
#     log_format f2b_session_errors '$msec failure "$cookie_session_id" - $remote_addr - $remote_user '
#      ;#                  '"$request" $status $bytes_sent '
#       #                  '"$http_referer" "$http_user_agent"';
#
#     # location checking blacklisted values:
#     location ... {
#       # check banned sessionid:
#       if ($blck_lst_ses != "") {
#         try_files "" @f2b-banned;
#       }
#       ...
#       # notify fail2ban about a failure inside nginx:
#       error_page 401 = @notify-f2b;
#       ...
#     }
#     ...
#     # location for return with "403 Forbidden" if banned:
#     location @f2b-banned {
#       default_type text/html;
#       return 403 "<br/><center>
#         <b style=\"color:red; font-size:18pt; border:2pt solid black; padding:5pt;\">
#         You are banned!</b></center>";
#     }
#     ...
#     # location to notify fail2ban about a failure inside nginx:
#     location @notify-f2b {
#       access_log /var/log/nginx/f2b-auth-errors.log f2b_session_errors;
#     }
#   }
#   ...
#
# Note that quote-character (and possibly other special characters) are not allowed currently as session-id.
# Thus please add any session-id validation rule in your locations (or in the corresponding backend-service), 
# like in example below:
#
#   location ... {
#     if ($cookie_session_id !~ "^[\w\-]+$") {
#       return  403 "Wrong session-id"
#     }
#     ...
#   }
#
# The parameters for jail corresponding log-format (f2b_session_errors):
#
#   [nginx-blck-lst]
#   filter =
#   datepattern = ^Epoch
#   failregex = ^ failure "<F-ID>[^"]+</F-ID>" - <ADDR>
#   usedns = no
#
# The same log-file can be used for IP-related jail (additionally to session-related, to ban very bad IPs):
#
#   [nginx-blck-ip]
#   maxretry = 100
#   filter =
#   datepattern = ^Epoch
#   failregex = ^ failure "[^"]+" - <ADDR>
#   usedns = no
#

[Definition]

# path to configuration of nginx (used to target nginx-instance in multi-instance system,
# and as path for the blacklisted map):
srv_cfg_path = /etc/nginx/

# cmd-line arguments to supply to test/reload nginx:
#srv_cmd = nginx -c %(srv_cfg_path)s/nginx.conf
srv_cmd = nginx

# pid file (used to check nginx is running):
srv_pid = /run/nginx.pid

# command used to check whether nginx is running and configuration is valid:
srv_is_running = [ -f "%(srv_pid)s" ]
srv_check_cmd = %(srv_is_running)s && %(srv_cmd)s -qt

# first test nginx is running and configuration is correct, hereafter send reload signal:
blck_lst_reload = %(srv_check_cmd)s; if [ $? -eq 0 ]; then
                    %(srv_cmd)s -s reload; if [ $? -ne 0 ]; then echo 'reload failed.'; fi;
                  fi;

# map-file for nginx, can be redefined using `action = nginx-block-map[blck_lst_file="/path/file.map"]`:
blck_lst_file = %(srv_cfg_path)s/blacklisted-sessions.map

# Action definition:

actionstart_on_demand = false
actionstart = touch '%(blck_lst_file)s'

actionflush = truncate -s 0 '%(blck_lst_file)s'; %(blck_lst_reload)s

actionstop = %(actionflush)s

actioncheck = 

_echo_blck_row = printf '\%%s 1;\n' "<fid>"

actionban = %(_echo_blck_row)s >> '%(blck_lst_file)s'; %(blck_lst_reload)s

actionunban = id=$(%(_echo_blck_row)s | sed -e 's/[]\/$*.^|[]/\\&/g'); sed -i "/^$id$/d" %(blck_lst_file)s; %(blck_lst_reload)s
