Fail2ban filter for mongodb

Toncy John

12/10/22, 1:53 PM

Fail2Ban version: 0.10.2

I have tried a lot of filter config files for MongoDB remote authentication fail, none of them have been working, I have figured that the problem is with failregex and I am not able to come up with a proper regex.

{"$date":"2021-08-10T17:27:13.498+05:30"},"s":"I",  "c":"ACCESS",   "id":20249,   "ctx":"conn187","msg":"Authentication failed","attr":{"mechanism":"SCRAM-SHA-256","speculative":true,"principalName":"Admin","authenticationDatabase":"admin","remote":"123.456.789.123:60054","extraInfo":{},"error":"AuthenticationFailed: SCRAM authentication failed, storedKey mismatch"}}

This is the mongo log I get on the failed attempt. I have tried using <HOST>, <ADDR> in the regex but the <HOST> gives 0.0.0.0 and <ADDR> gives 3:6005 (last digit of IP and 4 digits of port).

What would be the proper regex to filter this log?

Regex I have tried

^(.*Authentication failed.*)|(.*<ADDR>.*)|$
^(.*Authentication failed.*)|(.*<HOST>.*)|$

109

1 + 3

fail2ban

Toncy John

12/11/22, 6:13 AM

@MichaelHampton I have added the regex I have used. With the mentioned regex fail2ban was able to detect after max retries but it doesn't get the IP properly

mforsetti

12/11/22, 7:13 AM

uh fail2ban for mongodb? should you expose your database to public internet?

Toncy John

12/11/22, 7:32 AM

@mforsetti the database I am exposing to the public internet is only used for testing while development so this shouldn't be an issue. Also, the reason for setting up fail2ban is to act as extra security to compensate for this.

Score:0

Server

sebres

12/11/22, 5:56 PM

shortly:

[Definition]

datepattern = ^\{"t":\{"\$date":"%%Y-%%m-%%dT%%H:%%M:%%S\.%%f%%z"}\s*,\s*
_groupre = (?:"(?!(?:msg|attr|client|remote)\b)\w+":(?:"[^"]+"|\w+)\s*[,\}]\s*)
failregex = ^%(_groupre)s*"msg":"Authentication failed"\s*,\s*%(_groupre)s*"attr"\s*:\s*\{%(_groupre)s*"(?:client|remote)":"<ADDR>:\d+"

0 + 2

Toncy John

12/12/22, 10:52 AM

This works, thanks for the solution. Regarding exposing the database to the public internet how safe it would be with a strong passphrase and fail2ban implemented?

sebres

12/12/22, 11:14 AM

It's hard to say. Fail2ban would just reduce the risk of success by the bruteforce (e. g. drastically reduce the attempts count), but for example it would not really protect against some vulnerabilities (if any exists or will be introduced in the future). So if it's possible, better is to protect it by the firewall (e. g. net-filter white-listing some hosts/addresses allowed to communicate with mongodb, or http- or port-knocking, etc).

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Fail2ban filter for mongodb

TH: ตัวกรอง Fail2ban สำหรับ Mongodb

RO: Filtru Fail2ban pentru mongodb

RU: Фильтр Fail2ban для mongodb

VI: Bộ lọc Fail2ban cho mongodb

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