(C) 2019 John D. Robertson [email protected]
ban2fail is a simple and efficient tool to coordinate log file scanning, reporting, and iptables filtering. As the name implies, ban2fail was inspired by the popular fail2ban project (http://fail2ban.org). The main technical advantages ban2fail provides over fail2ban are:
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When installed as a systemd service, filtering response is well under 0.5 second.
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By design all relevant logfiles on disk are scanned, not just the current log files.
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A unique and transparent caching scheme is employed to make this process at least 100x as fast as doing the same thing with, say, grep.
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Instantaneously and conveniently produces on command all offending logfile entries which exist somewhere in the logfile history for given address(es).
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Easily handles hundreds of thousands of blocked IP addresses.
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Directly calls iptables, and handles filtering rules in one fell swoop using fork() & execve() calls.
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Provides integrated reporting with reverse and forward DNS information.
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When reporting, DNS lookups are performed in parallel with 200 simultaneous lookups.
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Written in pure C, with less than 15,000 lines of source code. Your CPU has better things to do than load the python runtime 10,000 times a day ;-)
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Efficient enough to run every 0.4 seconds without monopolizing a CPU core on a modest server.
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In the case of a reboot or after iptables filters get flushed, blocking rules will be instantaneously generated from entire log file histories (long memory).
ban2fail started with a few hours of frenzied C hacking after my mail server was exploited to deliver spam for others who had cracked a user's SMTP send password. After inspecting the log files I realized that crackers are now using widely distributed attacks, and that I would need an extremely efficient tool that could scan my entire log file history in a fraction of a second on my rather modest Linode virtual server to have a chance of stopping them. Here are the timing results for a typical scan on my server:
real 0m0.325s
user 0m0.186s
sys 0m0.150s
Currently I am running ban2fail from a systemd service file which triggers ban2fail whenever a watched log file is modified. This gives attackers at most a 0.4 second window to do their worst. I hope you find this code useful.
There are 4 basic types of reporting provided:
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summary
-
per-address
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per-country
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log file entries for specific address(es)
The summary report is very brief, but useful for spotting sudden changes in numbers of filtered addresses:
ban2fail -s
155 countries affected
7669 addresses currently blocked
Per-address is the most useful report to a system administrator looking for overly zealous address blocking. Records appear sorted with the most recent offenders on top. Here is a truncated sample report with full DNS information:
ban2fail -a+
=============== ban2fail v0.13.10 =============
Scanning "/var/log/auth.log"... found 666 offenses (565 addresses)
Scanning "/var/log/auth.log.1"... found 1143 offenses (1075 addresses)
Scanning "/var/log/auth.log.2.gz"... found 217 offenses (174 addresses)
Scanning "/var/log/auth.log.3.gz"... found 966 offenses (429 addresses)
Scanning "/var/log/auth.log.4.gz"... found 267 offenses (168 addresses)
>>>> Found 3259 offenses (2399 addresses) for /var/log/auth.log*
Scanning "/var/log/exim4/mainlog"... found 92 offenses (90 addresses)
Scanning "/var/log/exim4/mainlog.1"... found 319 offenses (284 addresses)
Scanning "/var/log/exim4/mainlog.2.gz"... found 329 offenses (302 addresses)
Scanning "/var/log/exim4/mainlog.3.gz"... found 315 offenses (295 addresses)
Scanning "/var/log/exim4/mainlog.4.gz"... found 521 offenses (214 addresses)
Scanning "/var/log/exim4/mainlog.5.gz"... found 254 offenses (229 addresses)
Scanning "/var/log/exim4/mainlog.6.gz"... found 234 offenses (214 addresses)
Scanning "/var/log/exim4/mainlog.7.gz"... found 256 offenses (238 addresses)
Scanning "/var/log/exim4/mainlog.8.gz"... found 231 offenses (218 addresses)
Scanning "/var/log/exim4/mainlog.9.gz"... found 330 offenses (213 addresses)
Scanning "/var/log/exim4/mainlog.10.gz"... found 882 offenses (351 addresses)
Scanning "/var/log/exim4/mainlog.11.gz"... found 1795 offenses (504 addresses)
Scanning "/var/log/exim4/mainlog.12.gz"... found 2222 offenses (1201 addresses)
Scanning "/var/log/exim4/mainlog.13.gz"... found 732 offenses (349 addresses)
Scanning "/var/log/exim4/mainlog.14.gz"... found 736 offenses (370 addresses)
>>>> Found 9248 offenses (4997 addresses) for /var/log/exim4/mainlog*
Scanning "/var/log/apache2/access.log"... found 18 offenses (7 addresses)
Scanning "/var/log/apache2/access.log.1"... found 734 offenses (54 addresses)
Scanning "/var/log/apache2/access.log.2.gz"... found 649 offenses (23 addresses)
Scanning "/var/log/apache2/access.log.3.gz"... found 383 offenses (6 addresses)
Scanning "/var/log/apache2/access.log.4.gz"... found 235 offenses (4 addresses)
Scanning "/var/log/apache2/access.log.5.gz"... found 75 offenses (4 addresses)
Scanning "/var/log/apache2/access.log.6.gz"... found 156 offenses (2 addresses)
Scanning "/var/log/apache2/access.log.7.gz"... found 815 offenses (6 addresses)
Scanning "/var/log/apache2/access.log.8.gz"... found 582 offenses (27 addresses)
Scanning "/var/log/apache2/access.log.9.gz"... found 1001 offenses (16 addresses)
Scanning "/var/log/apache2/access.log.10.gz"... found 802 offenses (8 addresses)
Scanning "/var/log/apache2/access.log.11.gz"... found 386 offenses (5 addresses)
Scanning "/var/log/apache2/access.log.12.gz"... found 466 offenses (78 addresses)
Scanning "/var/log/apache2/access.log.13.gz"... found 524 offenses (25 addresses)
Scanning "/var/log/apache2/access.log.14.gz"... found 565 offenses (16 addresses)
>>>> Found 7391 offenses (255 addresses) for /var/log/apache2/access.log*
Scanning "/var/log/mail.log"... found 608 offenses (457 addresses)
Scanning "/var/log/mail.log.1"... found 964 offenses (894 addresses)
Scanning "/var/log/mail.log.2.gz"... found 170 offenses (5 addresses)
Scanning "/var/log/mail.log.3.gz"... found 0 offenses (0 addresses)
Scanning "/var/log/mail.log.4.gz"... found 0 offenses (0 addresses)
>>>> Found 1742 offenses (1351 addresses) for /var/log/mail.log*
===== Found 21640 total offenses (7660 addresses) =====
Performing DNS lookups for up to 60 seconds ...
==> Completed 7660 of 7660 lookups in 60.0 seconds
3 Dec 07 07:09 1/0 offenses US [BLK] 184.179.216.156 NXDOMAIN
0 Dec 07 07:08 1/0 offenses US [BLK] 23.254.228.40 client-23-254-228-40.hostwindsdns.com !!
2 Dec 07 07:04 1/0 offenses HK [BLK] 47.91.220.119 NXDOMAIN
3 Dec 07 06:57 2/0 offenses TR [BLK] 81.214.245.188 81.214.245.188.dynamic.ttnet.com.tr !!
0 Dec 07 06:51 1/0 offenses -- [BLK] 188.119.103.157 NXDOMAIN
0 Dec 07 06:50 1/0 offenses GB [BLK] 185.217.230.211 SERVFAIL
0 Dec 07 06:47 1/0 offenses RU [BLK] 92.38.176.115 journalagricult.casa !
0 Dec 07 06:47 1/0 offenses CO [BLK] 191.103.219.225 xdsl-191-103-219-225.edatel.net.co !!
4 Dec 07 06:46 2/0 offenses CN [BLK] 175.6.5.233 NXDOMAIN
0 Dec 07 06:44 1/0 offenses UA [BLK] 109.87.78.144 144.78.87.109.triolan.net !!
0 Dec 07 06:36 1/0 offenses BR [BLK] 200.209.34.34 NXDOMAIN
3 Dec 07 06:35 2/0 offenses US [BLK] 184.179.216.138 NXDOMAIN
3 Dec 07 06:31 2/0 offenses CN [BLK] 120.33.205.162 NXDOMAIN
0 Dec 07 06:30 1/0 offenses SG [BLK] 160.20.12.205 SERVFAIL
--- snipped ---
===============================================
7660 addresses currently blocked
Per-country reports show how blocked address are distributed between the countries:
ban2fail -c
=============== ban2fail v0.13.10 =============
Scanning "/var/log/auth.log"... found 666 offenses (565 addresses)
Scanning "/var/log/auth.log.1"... found 1143 offenses (1075 addresses)
--- snipped ---
===== Found 21642 total offenses (7661 addresses) =====
US 1335 blocked addresses
CN 852 blocked addresses
VN 619 blocked addresses
RU 432 blocked addresses
BR 414 blocked addresses
IN 244 blocked addresses
GB 197 blocked addresses
-- 196 blocked addresses
AR 175 blocked addresses
TH 141 blocked addresses
FR 140 blocked addresses
ID 136 blocked addresses
--- snipped ---
===============================================
155 countries affected
Before unblocking any address it is usually necessary to investigate the offending log file entries. Here is an example:
ban2fail 184.179.216.156 23.254.228.40
====== Report for 184.179.216.156 ======
------- /var/log/auth.log -------------
Dec 7 07:09:52 srv auth: pam_unix(dovecot:auth): authentication failure; logname= uid=0 euid=0 tty=dovecot [email protected] rhost=184.179.216.156
------- /var/log/mail.log -------------
Dec 7 07:12:29 srv dovecot: imap-login: Disconnected: Inactivity (auth failed, 1 attempts in 160 secs): user=<[email protected]>, method=PLAIN, rip=184.179.216.156, lip=50.116.38.131, TLS, session=<lZUGChyZ8+G4s9ic>
====== Report for 23.254.228.40 ======
------- /var/log/exim4/mainlog -------------
2019-12-07 07:08:27 H=(green.medifeetz.icu) [23.254.228.40] F=<[email protected]> rejected RCPT <[email protected]>: 23.254.228.40 is listed at zen.spamhaus.org (127.0.0.3: https://www.spamhaus.org/sbl/query/SBLCSS)
ban2fail works from a configuration file found at "/etc/ban2fail/ban2fail.cfg". The overarching premise is that if any REGEX appearing in a LOGTYPE clause matches a line in an associated log file, then by default that IP will be blocked.
LOGTYPE auth {
# Where to find the log files
DIR= /var/log
PREFIX= auth.log
# How to read the timestamp
TIMESTAMP auth_ts {
# isolates the timestamp from a line matched by a TARGET
REGEX= ^(.*) srv
# Passed to strptime() to intrepret the timestamp string
STRPTIME= %b %d %T
# These stamps do not include the year, so it is implied.
FLAGS= GUESS_YEAR
}
TARGET imap {
# Pattern to search for, isolates the IP address
REGEX= imapd.*Login failed.*\[([0-9.a-f:]+)\]$
# Assign this as the severity of the offense.
SEVERITY= 3
}
TARGET ssh {
SEVERITY= 4
REGEX= sshd.*Failed password.*from ([0-9.a-f:]+) port [0-9]+ ssh2$
REGEX= sshd.*Invalid user.*from ([0-9.a-f:]+) port
}
TARGET negotiate_fail {
SEVERITY= 2
REGEX= Unable to negotiate with ([0-9.a-f:]+) port
}
TARGET dovecot {
SEVERITY= 3
REGEX= dovecot.*authentication failure.*rhost=([0-9.a-f:]+)
}
}
Syntax in the config file is pretty much the same as the nftables syntax. All keywords must be in upper case. Any values in the key=value pairs have whitespace stripped from the beginning and end of the line. Since there is little escaping of characters going on, regular expressions are mostly WYSIWYG. If you have a hash symbol '#' or a double quote '"' in your pattern (which are special characters for the config file parser), you will need to escape them like so:
# Nov 27 02:03:03 srv named[764]: client @0x7fe6a0053420 1.192.90.183#27388 (www.ipplus360.com): query (cache) 'www.ipplus360.com/A/IN' denied
REGEX= named.*client.* ([0-9.a-f:]+)\#.*denied$
Finding typos and so forth in the config file is easy; use the -v command flag to print all unrecognized content (besides comments).
ban2fail -v
The only way to alter the default blocking behavior is with a MAX_OFFENSES clause. This clause allows you specify how many offenses are tolerated before an IP is blocked. Offenses will naturally disappear as old logfiles are deleted by logrotate.
# Whitelist ourself
MAX_OFFENSES -1 {
# Put your server's IP addresses here
# IP= 1.2.3.4
IP= 127.0.0.1
# IP= dead:beef::20::32a
IP= ::1
}
# Allegedly legit servers
MAX_OFFENSES 50 {
# Google Ireland
IP= 2a00:1450:4864:20::32a
IP= 2a00:1450:4864:20::336
# Google EU
# Attempted to break in
# IP= 35.205.240.168
# Google US
IP= 09.85.216.42
# Attempted to break in
# IP= 130.211.246.128
IP= 209.85.166.194
IP= 209.85.166.195
IP= 209.85.208.67
IP= 209.85.214.194
IP= 209.85.215.173
IP= 209.85.215.175
IP= 209.85.215.193
IP= 209.85.216.42
IP= 2607:f8b0:4864:20::1034
IP= 2607:f8b0:4864:20::a46
# Yahoo
IP= 106.10.244.139
# Outlook
IP= 40.92.4.30
IP= 40.107.73.61
IP= 40.107.74.48
IP= 40.107.74.72
IP= 40.107.76.74
IP= 40.107.79.52
IP= 40.107.79.59
IP= 40.107.80.40
IP= 40.107.80.53
IP= 40.107.80.78
IP= 40.107.82.75
IP= 52.101.129.30
IP= 52.101.132.108
IP= 52.101.136.79
IP= 52.101.140.230
}
# "trusted" addresses
MAX_OFFENSES 200 {
# me from home
# IP= 1.2.3.4/20
# Customer
# IP= 5.6.7.8/24
}
If you recieve a complaint about an address unjustly getting blocked, place it in one of the MAX_OFFENSES blocks, and the IP will be unblocked the next time ban2fail runs in production mode.
There are two primary modes in which ban2fail is used:
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Production mode, where iptables rules are modified.
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Testing mode, where modifications to blocking rules are merely indicated.
In production mode it is expected that ban2fail is running non-interactively, and no output is printed unless addresses are (un)blocked. It is also possible to generate a listing of addresses, offense counts, and status with the -a command flag. Likewise, a listing of countries and offense counts is available with the -c flag. In order to get DNS information for the -a flag, follow with a plus for all DNS info -a+, or a minus for only legit (backward & forward match) info -a-. In the list, DNS issues are presented like so:
# DNS is good
0 Dec 06 08:31 1/0 offenses AR [BLK] 200.71.237.244 host244.200-71-237.telecom.net.ar
# Reverse lookup failed with DNS server
0 Dec 05 19:43 1/0 offenses GB [BLK] 185.217.230.146 SERVFAIL
# Reverse lookup is a non-existent domain
2 Dec 05 21:11 1/0 offenses US [BLK] 67.205.153.94 NXDOMAIN
# Forward lookup does not match reverse lookup
0 Dec 06 08:40 1/0 offenses LU [BLK] 92.38.132.54 ibocke43.monster !
# Forward DNS record does not exist
0 Dec 06 08:37 1/0 offenses US [BLK] 63.81.90.135 63-81-90-135.nca.lanset.com !!
# DNS is inconclusive due to lack of response from a DNS server
0 Dec 05 22:04 1/0 offenses RU [BLK] 77.221.144.107 news5.burningcoalsa.com ~
If you want to see the offending log lines for specific address(es), supply them on the command line like so:
john@srv:~$ ban2fail 68.183.105.52
====== Report for 68.183.105.52 ======
------- /var/log/auth.log -------------
Dec 5 17:50:47 srv sshd[22326]: Invalid user cron from 68.183.105.52 port 41874
Dec 5 17:50:48 srv sshd[22326]: Failed password for invalid user cron from 68.183.105.52 port 41874 ssh2
In test mode (-t flag) the presumption is that you are testing a modified configuration which is not yet in place, and that you don't want to disturb the production setup. This is how you might do that:
ban2fail -t myNew.cfg -a
No iptables rules will be modified. You will be shown in the listing which addresses would be (un)blocked if the contents of "myNew.cfg" was in place, and ban2fail was running in production mode.
When you are happy with the new configuration, copy it into place, and the the iptable rule changes will be realized the next time ban2fail runs in production mode.
I've tested ban2fail only on Debian Buster, but it should compile on just about any modern Linux distro. It uses the following libraries:
-
libcrypto from the libssl package, for md5 checksums
-
libGeoIP to identify the country of origin for IP addresses
-
libz to read compressed log files
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libpthread for parallel DNS lookups (200 simultaneous)
-
libdb caching of offense location and size in log files
Build and install like so:
make release
make install
The make install target calls install.sh, which does a bunch of stuff including setting up and enabling a systemd service, so you might want have a look before pulling the trigger.
ban2fail.service points to ban2fail.sh, which can be tested from the command line for debugging. Remember to make sure the service is disabled:
systemctl stop ban2fail
In order to run ban2fail as non-root user, the user must belong to group 'adm'. This is so in order to run iptables, which is accomplished via setuid(0) at the appropriate time.