naxsi

Basic Setup

Architecture of naxsi configuration

http {} level : include naxsi_core.rules
server {} level :
- Dynamic modifiers
location {} level :
location /RequestDenied
- return HTTP error code, post-processing …

Example configuration

#Only for nginx's version with modular support
load_module /../modules/ngx_http_naxsi_module.so;
events {
 ...
}
http {
 include /tmp/naxsi_ut/naxsi_core.rules;
 ...
 server {
  listen ...;
  server_name  ...;
  location / {
   #Enable naxsi
   SecRulesEnabled;
   #Enable learning mode
   LearningMode;
   #Define where blocked requests go
   DeniedUrl "/50x.html"; 
   #CheckRules, determining when naxsi needs to take action
   CheckRule "$SQL >= 8" BLOCK;
   CheckRule "$RFI >= 8" BLOCK;
   CheckRule "$TRAVERSAL >= 4" BLOCK;
   CheckRule "$EVADE >= 4" BLOCK;
   CheckRule "$XSS >= 8" BLOCK;
   #naxsi logs goes there
   error_log /.../foo.log;
   ...
  }
  error_page   500 502 503 504  /50x.html;
  #This is where the blocked requests are going
  location = /50x.html {
  return 418; #I'm a teapot \o/
  }
 }
}

Next steps

The next step is learning; however, before jumping there, ensure that you have:

A nginx as a webserver or reverse proxy
Naxsi installed and running in learning mode
If you perform a request such as curl 'http://127.0.0.1:4242/?a=<>', you should see a NAXSI_FMT in your logs : 2016/07/12 13:27:04 [error] 14492#0: *1 NAXSI_FMT: ip=127.0.0.1&server=127.0.0.1&uri=/&learning=1&vers=0.55rc2&total_processed=1&total_blocked=1&block=1&cscore0=$XSS&score0=16&zone0=ARGS&id0=1302&var_name0=a&zone1=ARGS&id1=1303&var_name1=a, client: 127.0.0.1, server: localhost, request: "GET /?a=<> HTTP/1.1", host: "127.0.0.1:4242"

Learning, log-injection, ElasticSearch, Kibana

The ElasticSearch/Kibana part is optional but provides a great comfort and way to visualize “what’s going on”.

Global Workflow

Components

Nxtool setup can be found here: (tl;dr: python setup.py install, or ./nxtool.py -c nxapi.json -x)

nxapi documentation

Kibana (v4 as of this writing) can be downloaded here:

kibana website

Once those two components are setup, you should be able to inject naxsi logs into ElasticSearch with NxTool. Here is an example of what it might look like in production:

Kibana Dashboard

Configuration - NXTOOL

As stated in dedicated documentation, nxtool comes with a json file specifying ES location, index etc.

"elastic" : {
 "host" : "127.0.0.1:9200",
 "index" : "nxapi",
 "doctype" : "events",
 "default_ttl" : "7200",
 "max_size" : "1000",
 "version" : "2"
},

Once configured and running on the same host as nginx, you can start injecting logs into ES:

nxtool.py --fifo /tmp/naxsi_pipe --no-timeout (here, nginx is being told to write logs to /tmp/naxsi_pipe which is a FIFO created by nxtool)

Configuration - Kibana

Now, you should be able to configure Kibana to setup a dashboard to visualize your naxsi data.

This step is left as an exercise for the reader, see Creating Kibana Dashboard.

Configuration - DataDog

Golden Setup

Blacklisting = mod_security

WAF = naxsi

https://gist.github.com/marcinguy/3a106991d3a84995efacc473f8db21a9

You can get logs to DataDog very easily using this Grok rule:

Grok Parser rule

​myParsingrule %{date("yyyy/MM/dd HH:mm:ss"):connect_date} \[%{word:status}\] %{number:id}\#%{number:id2}: \*%{number:value} %{data::json}

Then you will see a nice Dashboard of Attacks

[[https://user-images.githubusercontent.com/20355405/90318948-4c52a700-df34-11ea-8521-259551b5322e.png]]

You can also send alerts to Slack:

[[https://user-images.githubusercontent.com/20355405/92943641-52fd0d00-f453-11ea-99ee-411d9ea33105.png]]

You just built an Open Source WAF solution with Alerts and Dashboard.

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