SCG WS nginx

This article is part of the OWASP Secure Configuration Guide.

Back to the OWASP Secure Configuration Guide ToC:
   https://www.owasp.org/index.php/Secure_Configuration_Guide
Back to the OWASP Secure Configuration Guide Project:
   https://www.owasp.org/index.php/OWASP_Secure_Configuration_Guide

1 Summary
2 Secure Configuration
3 References

NginX Secure Configuration Guide

Summary

This provides NginX security configuration harden guide. The configuration guide is focused on the NginX itself. Therefore, the Linux OS configuration hardening is not covered here.

It includes the following topic:

Buffer Overflow Protection
Remove Unnecessary backup files
Mitigating Slow HTTP DoS Attack
Allow Access To Specified Domain Only
Limit IP clients access
SSL/TLS Configuration
HTTP secure Header
Limit HTTP Method
SSL Module

Secure Configuration

Buffer Overflow Protection

 ## Size Limits & Buffer Overflows ##
 ## the size below needs testing with subject to the real needs
  client_body_buffer_size  1K;
  client_header_buffer_size 1k;
  client_max_body_size 1k;
  large_client_header_buffers 2 1k;

 ## END ##

Refer to [1]

Remove Unnecessary backup files

Use the following command to search if there is any unnecessary backup files to be removed.

# find /nginx -name '.?*' -not -name .ht* -or -name '*~' -or -name '*.bak*' -or -name '*.old*'
# find /usr/local/nginx/html/ -name '.?*' -not -name .ht* -or -name '*~' -or -name '*.bak*' -or -name '*.old*'

=== Remove Version number

# Display nginx Version number in error or http header may result in hacker to search for known vulnerability. 
# Therefore, the version number should be removed for every http response.
server_tokens off;

Mitigating Slow HTTP DoS Attack

 ## Timeouts definition ##
  client_body_timeout   10;
  client_header_timeout 10;
  keepalive_timeout     5 5;
  send_timeout          10;
 ## End ##

client_body_timeout: Defines a timeout for reading client request body. The timeout is set only for a period between two successive read operations, not for the transmission of the whole request body. If a client does not transmit anything within this time, the 408 (Request Time-out) error is returned to the client.
client_header_timeout: Defines a timeout for reading client request header. If a client does not transmit the entire header within this time, the 408 (Request Time-out) error is returned to the client.
keepalive_timeout: The first parameter sets a timeout during which a keep-alive client connection will stay open on the server side. The zero value disables keep-alive client connections. The optional second parameter sets a value in the “Keep-Alive: timeout=time” response header field. Two parameters may differ.

The “Keep-Alive: timeout=time” header field is recognized by Mozilla and Konqueror. MSIE closes keep-alive connections by itself in about 60 seconds.

send_timeout: Sets a timeout for transmitting a response to the client. The timeout is set only between two successive write operations, not for the transmission of the whole response. If the client does not receive anything within this time, the connection is closed.

Allow Access To Specified Domain Only

##  i.e. abc.com, images.abc.com and www.abc.com
      if ($host !~ ^(abc.com|www.abc.com|images.abc.com)$ ) {
         return 444;
      }
##

Limit IP clients access

Limit specific folder to certain source IP clients only.

   ## the docs folder is only allowed specific IP range in 192.168.1.0/24

  location /docs/ {
  ## block one workstation
  deny    192.168.1.1;
  ## allow anyone in 192.168.1.0/24
  allow   192.168.1.0/24;
  ## drop rest of the world
  deny    all;
}

SSL/TLS Configuration

Disable SSLv3(enabled by default since nginx 0.8.19)

server {
       # SSL protocols TLS v1~TLSv1.2 are allowed. Disabed SSLv3
       ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
}

For further details on SSL Module configuration refer to http://wiki.nginx.org/NginxHttpSslModule

SSL Module

server {
     # enables server-side protection from BEAST attacks
     ssl_prefer_server_ciphers on;

     # Disabled insecure ciphers suite. For example, MD5, DES, RC4, PSK
      ssl_ciphers "ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4";

}

HTTP secure Header

# X-Frame-Options is to prevent from clickJacking attack
add_header X-Frame-Options SAMEORIGIN;

#  disable content-type sniffing on some browsers.
add_header X-Content-Type-Options nosniff;

# This header enables the Cross-site scripting (XSS) filter
add_header X-XSS-Protection "1; mode=block";

# This will enforce HTTP browsing into HTTPS and avoid ssl stripping attack
add_header Strict-Transport-Security "max-age=31536000; includeSubdomains;";

refer to https://www.owasp.org/index.php/List_of_useful_HTTP_headers

Limit HTTP Method


## Only GET, Post, PUT are allowed##
     if ($request_method !~ ^(GET|PUT|POST)$ ) {
         return 444;
     }
## Do not accept HEAD, DELETE, SEARCH and other methods ##