README.md

Nginx Quick Reference

My notes about Nginx...

Introduction
External Resources
Helpers
- Shell aliases
Base rules
Performance
Hardening

Introduction

Before using the Nginx please read Beginner’s Guide.

Nginx (/ˌɛndʒɪnˈɛks/ EN-jin-EKS) is an HTTP and reverse proxy server, a mail proxy server, and a generic TCP/UDP proxy server, originally written by Igor Sysoev. For a long time, it has been running on many heavily loaded Russian sites including Yandex, Mail.Ru, VK, and Rambler.

To increase your knowledge, read Nginx Documentation.

General disclaimer

This is not an official handbook. Many of these rules refer to another resources. It is rather a quick collection of some rules used by me in production environments (not only).

The most important thing:

Do not follow guides just to get 100% of something. Think about what you actually do at your server!

And remember:

These guidelines provides recommendations for very restrictive setup.

SSL Report: blkcipher.info

Many of these recipes have been applied to the configuration of my private website. I finally got all 100%'s on my scores:

Printable high-res hardening checklist

Simple hardening checklist based on this recipes (@ssllabs A+ 100%) - High-Res 5000x7500:

For *.xcf and *.pdf formats please see this directory.

External Resources

Helpers

Shell aliases

alias ng.test='nginx -t -c /etc/nginx/nginx.conf'
alias ng.stop='ng.test && systemctl stop nginx'
alias ng.reload='ng.test && systemctl reload nginx'

Base rules

? Organising Nginx configuration

Rationale

When your configuration grow, the need for organising your code will also grow. Well organised code is:

easier to understand

easier to maintain

easier to work with

Use include directive to attach your nginx specific code to global config, contexts and other.

Example

# Store this configuration in https-ssl-common.conf
listen 10.240.20.2:443 ssl;

root /etc/nginx/error-pages/other;

ssl_certificate /etc/nginx/domain.com/certs/nginx_domain.com_bundle.crt;
ssl_certificate_key /etc/nginx/domain.com/certs/domain.com.key;

# And include this file in server section:
server {

  include /etc/nginx/domain.com/commons/https-ssl-common.conf;

  server_name domain.com www.domain.com;
  ...

External resources

Organize your data and code

? Separate listen directives for 80 and 443

Rationale

...

Example

# For http:
server {

  listen 10.240.20.2:80;
  ...

}

# For https:
server {

  listen 10.240.20.2:443 ssl;
  ...

}

External resources

Understanding the Nginx Configuration File Structure and Configuration Contexts

? Use `default_server` directive at the beginning

Rationale

Nginx should prevent processing requests with undefined server names - also traffic on ip address. It also protects against configuration errors and providing incorrect backends.

Example

server {

  listen 10.240.20.2:443 ssl;

  # Place it at the beginning of the configuration file.
  server_name default_server;

  location / {
    # serve static file (error page):
    root /etc/nginx/error-pages/404;
    # or redirect:
    # return 301 https://badssl.com;
  }

}

server {

  listen 10.240.20.2:443 ssl;

  server_name domain.com;
  ...

}

server {

  listen 10.240.20.2:443 ssl;

  server_name app.domain.com;
  ...

}

External resources

How nginx processes a request

? Force all connections over TLS

Rationale

You should always use HTTPS instead of HTTP to protect your website, even if it doesn’t handle sensitive communications.

Example

server {

  listen 10.240.20.2:80;

  server_name domain.com;
  return 301 https://$host$request_uri;

}

server {

  listen 10.240.20.2:443 ssl;

  server_name domain.com;
  ...

}

External resources

Should we force user to HTTPS on website?

? Use geo/map modules instead allow/deny

Rationale

Creates variables with values depending on the client IP address. Use map or geo modules (one of them) to prevent users abusing your servers.

Example

# Map module:
map $remote_addr $globals_internal_map_acl {

  # Status code:
  #  - 0 = false
  #  - 1 = true
  default 0;

  ### INTERNAL ###
  10.255.10.0/24 1;
  10.255.20.0/24 1;
  10.255.30.0/24 1;
  192.168.0.0/16 1;

}

# Geo module:
geo $globals_internal_geo_acl {

  # Status code:
  #  - 0 = false
  #  - 1 = true
  default 0;

  ### INTERNAL ###
  10.255.10.0/24 1;
  10.255.20.0/24 1;
  10.255.30.0/24 1;
  192.168.0.0/16 1;

}

External resources

Nginx Basic Configuration (Geo Ban)

? Map all the things...

Rationale

Map module provides a more elegant solution for clearly parsing a big list of regexes, e.g. User-Agents. Manage a large number of redirects with Nginx maps.

Example

map $http_user_agent $device_redirect {

  default "desktop";

  ~(?i)ip(hone|od) "mobile";
  ~(?i)android.*(mobile|mini) "mobile";
  ~Mobile.+Firefox "mobile";
  ~^HTC "mobile";
  ~Fennec "mobile";
  ~IEMobile "mobile";
  ~BB10 "mobile";
  ~SymbianOS.*AppleWebKit "mobile";
  ~Opera\sMobi "mobile";

}

if ($device_redirect = "mobile") {

  return 301 https://m.domain.com$request_uri;

}

External resources

Cool Nginx feature of the week

? Drop the same root inside location block

Rationale

If you add a root to every location block then a location block that isn’t matched will have no root. Set global root inside server directive.

Example

server {

  server_name domain.com;

  root /var/www/domain.com/public;

  location / {
    ...
  }

  location /api {
    ...
  }

  location /static {
    root /var/www/domain.com/static;
    ...
  }

}

External resources

Nginx Pitfalls: Root inside location block

? Use debug mode for debugging

Rationale

There's probably more detail than you want, but that can sometimes be a lifesaver (but log file growing rapidly).

Example

rewrite_log on;
error_log /var/log/nginx/error-debug.log debug;

External resources

A debugging log

Performance

? Set manually worker processes

Rationale

The worker_processes directive is the sturdy spine of life for Nginx. This directive is responsible for letting our virtual server know many workers to spawn once it has become bound to the proper IP and port(s).

Official Nginx documentation say: "When one is in doubt, setting it to the number of available CPU cores would be a good start (the value "auto" will try to autodetect it)."

I think for high load proxy servers (also standalone servers) the best value is ALL_CORES - 1 (please test it before used).

Example

# VCPU = 4 , expr $(nproc --all) - 1
worker_processes 3;

External resources

Nginx Core Module - worker_processes

? Use HTTP/2

Rationale

All requests are downloaded in parallel, not in a queue, HTTP headers are compressed, pages transfer as a binary, not as a text file, which is more efficient and more.

Example

# For https:
server {

  listen 10.240.20.2:443 ssl http2;
  ...

External resources

What is HTTP/2 - The Ultimate Guide

? Maintaining SSL Sessions

Rationale

This improves performance from the clients’ perspective, because it eliminates the need for a new (and time-consuming) SSL handshake to be conducted each time a request is made.

Most servers do not purge sessions or ticket keys, thus increasing the risk that a server compromise would leak data from previous (and future) connections.

Example

ssl_session_cache shared:SSL:10m;
ssl_session_timeout 24h;
ssl_session_tickets off;
ssl_buffer_size 1400;

External resources

Hardening

? Run as an unprivileged user

Rationale

There is no real difference in security just by changing the process owner name. On the other hand in security, the principle of least privilege states that an entity should be given no more permission than necessary to accomplish its goals within a given system. This way only master process runs as root.

Example

# Edit nginx.conf:
user www-data;

# Set owner and group:
chown -R www-data:www-data /var/www/domain.com

External resources

Why does nginx starts process as root?

? Disable unnecessary modules

Rationale

It is recommended to disable any modules which are not required as this will minimize the risk of any potential attacks by limiting the operations allowed by the web server.

Example

# During installation:
./configure --without-http_autoindex_module

# Comment modules in the configuration file:
# load_module /usr/share/nginx/modules/ndk_http_module.so;
# load_module /usr/share/nginx/modules/ngx_http_auth_pam_module.so;

External resources

nginx-modules

? Protect sensitive resources

Rationale

Hidden directories and files should never be web accessible.

Example

if ( $request_uri ~ "/\.git" ) {

  return 403;

}

# or
location ~ /\.git {

  deny all;

}

# or all . directories/files in general
location ~ /\. {

  deny all;

}

External resources

Hidden directories and files as a source of sensitive information about web application

? Hide Nginx version number

Rationale

Disclosing the version of nginx running can be undesirable, particularly in environments sensitive to information disclosure.

Example

server_tokens off;

External resources

Remove Version from Server Header Banner in nginx

? Hide Nginx server signature

Rationale

You should compile Nginx from sources with ngx_headers_more to used more_set_headers directive.

Example

more_set_headers "Server: Unknown";

External resources

How to change (hide) the Nginx Server Signature?

? Hide upstream proxy headers

Rationale

When nginx is used to proxy requests from an upstream server (such as a PHP-FPM instance), it can be beneficial to hide certain headers sent in the upstream response (for example, the version of PHP running).

Example

proxy_hide_header X-Powered-By;
proxy_hide_header X-AspNetMvc-Version;
proxy_hide_header X-AspNet-Version;
proxy_hide_header X-Drupal-Cache;

External resources

Remove insecure http headers

? Use only 4096-bit private keys

Rationale

Advisories recommend 2048 for now. Security experts are projecting that 2048 bits will be sufficient for commercial use until around the year 2030.

If you want to get A+ with 100%s on SSL Lab you should definitely use 4096 bit private key.

The "SSL/TLS Deployment Best Practices" book say: The cryptographic handshake, which is used to establish secure connections, is an operation whose cost is highly influenced by private key size. Using a key that is too short is insecure, but using a key that is too long will result in “too much” security and slow operation. For most web sites, using RSA keys stronger than 2048 bits and ECDSA keys stronger than 256 bits is a waste of CPU power and might impair user experience. Similarly, there is little benefit to increasing the strength of the ephemeral key exchange beyond 2048 bits for DHE and 256 bits for ECDHE.

I always generate 4096 bit keys for low busy sites since the downside is minimal (slightly lower performance) and security is slightly higher (although not as high as one would like).

Use of alternative solution: ECC Certificate Signing Request (CSR).

Example

### Example (RSA):
( _fd="domain.com.key" ; _len="4096" ; openssl genrsa -out ${_fd} ${_len} )

# Let's Encrypt:
certbot certonly -d domain.com -d www.domain.com --rsa-key-size 4096

### Example (ECC):
# _curve: prime256v1, secp521r1, secp384r1
( _fd="domain.com.key" ; _fd_csr="domain.com.csr" ; _curve="prime256v1" ; openssl ecparam -out ${_fd} -name ${_curve} -genkey ; openssl req -new -key ${_fd} -out ${_fd_csr} -sha256 )

# Let's Encrypt (from above):
certbot --csr ${_fd_csr} -[other-args]

For x25519:

( _fd="private.key" ; _curve="x25519" ; \
openssl genpkey -algorithm ${_curve} -out ${_fd} )

ssllabs score: 100

( _fd="domain.com.key" ; _len="2048" ; openssl genrsa -out ${_fd} ${_len} )

# Let's Encrypt:
certbot certonly -d domain.com -d www.domain.com

ssllabs score: 90

External resources

So you're making an RSA key for an HTTPS certificate. What key size do you use?

? Keep only TLS 1.2 (+ TLS 1.3)

Rationale

TLS 1.1 and 1.2 are both without security issues - but only v1.2 provides modern cryptographic algorithms. TLS 1.0 and TLS 1.1 protocols will be removed from browsers at the beginning of 2020.

If you use TLS 1.2 or TLS 1.1/1.2 older clients will not able to load your site.

Example

ssl_protocols TLSv1.2;

ssllabs score: 100

ssl_protocols TLSv1.2 TLSv1.1;

ssllabs score: 95

External resources

? Use only strong ciphers

Rationale

This parameter changes quite often, the recommended configuration for today may be out of date tomorrow. For more security use only strong and not vulnerable ciphersuite (but if you use http/2 you can get Server sent fatal alert: handshake_failure error).

For backward compatibility software components you should use less restrictive ciphers.

You should definitely disable weak ciphers like those with DSS, DSA, DES/3DES, RC4, MD5, SHA1, null, anon in the name.

Example

ssl_ciphers "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384";

ssllabs score: 100

ssl_ciphers "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA:ECDHE-ECDSA-AES128-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256";

ssllabs score: 90

External resources

? Use more secure ECDH Curve

Rationale

X25519 is a more secure but slightly less compatible option. To maximise interoperability with existing browsers and servers, stick to P-256 prime256v1 and P-384 secp384r1 curves.

If you not set ssh_ecdh_curve, then the Nginx will use its default settings, e.g. chrome will prefer X25519, but this is not recommended because you can not control the Nginx's default settings (seems to be P-256).

Explicitly set ssh_ecdh_curve X25519:prime256v1:secp521r1:secp384r1; - for me it's perfect solution because if web browser support X25519 curves -> use X25519 otherwise try the next curve listed.

Do not use the secp112r1, secp112r2, secp128r1, secp128r2, secp160k1, secp160r1, secp160r2, secp192k1 curves. They have a too small size for security application according to NIST recommendation.

Example

ssl_ecdh_curve X25519;

# Alternative (this one doesn’t affect compatibility, by the way; it’s just a question of the preferred order)
ssl_ecdh_curve X25519:prime256v1:secp521r1:secp384r1;

ssllabs score: 100

External resources

? Use strong Key Exchange

Rationale

dhparam is only used when using DHE ciphers. Given the ciphers listed, dhparam would not be used. Most of the "modern" profiles from places like Mozilla's ssl config generator no longer recommend using this.

Default key size in OpenSSL is 1024 bits - it's vulnerable and breakable. For the best security configuration use your own 4096 bit DH Group or use known safe ones pre-defined DH groups (it's recommended) from mozilla.

Example

# Generating DH parameters:
openssl dhparam -dsaparam -out /etc/nginx/ssl/dhparam_4096.pem 4096

# Nginx configuration:
ssl_dhparam /etc/nginx/ssl/dhparams_4096.pem;

ssllabs score: 100

External resources

? Defend against the BEAST attack

Rationale

Enables server-side protection from BEAST attacks.

Example

ssl_prefer_server_ciphers on;

External resources

Is BEAST still a threat?

? Disable compression (mitigation of CRIME attack)

Rationale

Disabling SSL/TLS compression stops the attack very effectively.

Some attacks are possible because of gzip being enabled on SSL requests. In most cases, the best action is to simply disable gzip for SSL requests.

Example

gzip off;

External resources

SSL/TLS attacks: Part 2 – CRIME Attack

? HTTP Strict Transport Security

Rationale

The header indicates for how long a browser should unconditionally refuse to take part in unsecured HTTP connection for a specific domain.

Example

add_header Strict-Transport-Security "max-age=63072000; includeSubdomains" always;

ssllabs score: A+

External resources

HTTP Strict Transport Security Cheat Sheet

? Reduce XSS risks (Content-Security-Policy)

Rationale

CSP reduce the risk and impact of XSS attacks in modern browsers.

Example

# This policy allows images, scripts, AJAX, and CSS from the same origin, and does not allow any other resources to load.
add_header Content-Security-Policy "default-src 'none'; script-src 'self'; connect-src 'self'; img-src 'self'; style-src 'self';" always;

External resources

? Control the behavior of the Referer header (Referrer-Policy)

Rationale

Determine what information is sent along with the requests.

Example

add_header Referrer-Policy "no-referrer";

External resources

A new security header: Referrer Policy

? Provide clickjacking protection (X-Frame-Options)

Rationale

Helps to protect your visitors against clickjacking attacks. It is recommended that you use the x-frame-options header on pages which should not be allowed to render a page in a frame.

Example

add_header X-Frame-Options "SAMEORIGIN" always;

External resources

Clickjacking Defense Cheat Sheet

? Prevent some categories of XSS attacks (X-XSS-Protection)

Rationale

Enable the cross-site scripting (XSS) filter built into modern web browsers.

Example

add_header X-XSS-Protection "1; mode=block" always

External resources

X-XSS-Protection HTTP Header

? Prevent Sniff Mimetype middleware (X-Content-Type-Options)

Rationale

It prevents the browser from doing MIME-type sniffing (prevents "mime" based attacks).

Example

add_header X-Content-Type-Options "nosniff" always;

External resources

X-Content-Type-Options HTTP Header

? Deny the use of browser features (Feature-Policy)

Rationale

This header protect your site from third parties using APIs that have security and privacy implications, and also from your own team adding outdated APIs or poorly optimized images.

Example

add_header Feature-Policy "geolocation none; midi none; notifications none; push none; sync-xhr none; microphone none; camera none; magnetometer none; gyroscope none; speaker none; vibrate none; fullscreen self; payment none; usb none;";

External resources

? Reject unsafe HTTP methods

Rationale

Set of methods support by a resource. An ordinary web server supports the HEAD, GET and POST methods to retrieve static and dynamic content. Other (e.g. OPTIONS, TRACE) methods should not be supported on public web servers, as they increase the attack surface.

Example

add_header Allow "GET, POST, HEAD" always;

if ( $request_method !~ ^(GET|POST|HEAD)$ ) {

  return 405;

}

External resources

Vulnerability name: Unsafe HTTP methods

? Control Buffer Overflow attacks

Rationale

Buffer overflow attacks are made possible by writing data to a buffer and exceeding that buffers’ boundary and overwriting memory fragments of a process. To prevent this in nginx we can set buffer size limitations for all clients.

Example

client_body_buffer_size 100k;
client_header_buffer_size 1k;
client_max_body_size 100k;
large_client_header_buffers 2 1k;

External resources

SCG WS nginx

? Mitigating Slow HTTP DoS attack (Closing Slow Connections)

Rationale

Close connections that are writing data too infrequently, which can represent an attempt to keep connections open as long as possible.

Example

client_body_timeout 10s;
client_header_timeout 10s;
keepalive_timeout 5 5;
send_timeout 10;

External resources

GitHub - trimstray/nginx-quick-reference: This notes describes how to improve Ng...

README.md

Nginx Quick Reference

Table of Contents

Introduction

General disclaimer

SSL Report: blkcipher.info

Printable high-res hardening checklist

External Resources

About Nginx

References

Cheatsheets

Performance & Hardening

Config generators

Static analyzers

Log analyzers

Performance analyzers

Benchmarking tools

Online tools

Other stuff

Helpers

Shell aliases

Base rules

? Organising Nginx configuration

? Separate listen directives for 80 and 443

? Use default_server directive at the beginning

? Force all connections over TLS

? Use geo/map modules instead allow/deny

? Map all the things...

? Drop the same root inside location block

? Use debug mode for debugging

Performance

? Set manually worker processes

? Use HTTP/2

? Maintaining SSL Sessions

Hardening

? Run as an unprivileged user

? Disable unnecessary modules

? Protect sensitive resources

? Hide Nginx version number

? Hide Nginx server signature

? Hide upstream proxy headers

? Use only 4096-bit private keys

? Keep only TLS 1.2 (+ TLS 1.3)

? Use only strong ciphers

? Use more secure ECDH Curve

? Use strong Key Exchange

? Defend against the BEAST attack

? Disable compression (mitigation of CRIME attack)

? HTTP Strict Transport Security

? Reduce XSS risks (Content-Security-Policy)

? Control the behavior of the Referer header (Referrer-Policy)

? Provide clickjacking protection (X-Frame-Options)

? Prevent some categories of XSS attacks (X-XSS-Protection)

? Prevent Sniff Mimetype middleware (X-Content-Type-Options)

? Deny the use of browser features (Feature-Policy)

? Reject unsafe HTTP methods

? Control Buffer Overflow attacks

? Mitigating Slow HTTP DoS attack (Closing Slow Connections)

Recommend

About Joyk

? Use `default_server` directive at the beginning