master represents the unreleased 4.x line. See the upgrading to 4.x doc for instructions on how to upgrade. Bug fixes should go in the 3.x branch for now.

The 3.x branch is moving into maintenance mode. See the upgrading to 3.x doc for instructions on how to upgrade including the differences and benefits of using the 3.x branch.

The 2.x branch will be not be maintained once 4.x is released. The documentation below only applies to the 3.x branch. See the 2.x README for the old way of doing things.

The gem will automatically apply several headers that are related to security. This includes:

• Content Security Policy (CSP) - Helps detect/prevent XSS, mixed-content, and other classes of attack. CSP 2 Specification
  • https://csp.withgoogle.com
  • https://csp.withgoogle.com/docs/strict-csp.html
  • https://csp-evaluator.withgoogle.com
• HTTP Strict Transport Security (HSTS) - Ensures the browser never visits the http version of a website. Protects from SSLStrip/Firesheep attacks. HSTS Specification
• X-Frame-Options (XFO) - Prevents your content from being framed and potentially clickjacked. X-Frame-Options Specification
• X-XSS-Protection - Cross site scripting heuristic filter for IE/Chrome
• X-Content-Type-Options - Prevent content type sniffing
• X-Download-Options - Prevent file downloads opening
• X-Permitted-Cross-Domain-Policies - Restrict Adobe Flash Player's access to data
• Referrer-Policy - Referrer Policy draft
• Public Key Pinning - Pin certificate fingerprints in the browser to prevent man-in-the-middle attacks due to compromised Certificate Authorities. Public Key Pinning Specification
• Expect-CT - Only use certificates that are present in the certificate transparency logs. Expect-CT draft specification.
• Clear-Site-Data - Clearing browser data for origin. Clear-Site-Data specification.

It can also mark all http cookies with the Secure, HttpOnly and SameSite attributes (when configured to do so).

secure_headers is a library with a global config, per request overrides, and rack middleware that enables you customize your application settings.

• Named overrides and appends
• Per action configuration
• Cookies
• HPKP
• Hashes
• Sinatra Config

For Rails 3+ applications, secure_headers has a railtie that should automatically include the middleware. If for some reason the middleware is not being included follow the instructions for Rails 2.

For Rails 2 or non-rails applications, an explicit statement is required to use the middleware component.

use SecureHeaders::Middleware

If you do not supply a default configuration, exceptions will be raised. If you would like to use a default configuration (which is fairly locked down), just call SecureHeaders::Configuration.default without any arguments or block.

All nil values will fallback to their default values. SecureHeaders::OPT_OUT will disable the header entirely.

Word of caution: The following is not a default configuration per se. It serves as a sample implementation of the configuration. You should read more about these headers and determine what is appropriate for your requirements.

SecureHeaders::Configuration.default do |config|
  config.cookies = {
    secure: true, # mark all cookies as "Secure"
    httponly: true, # mark all cookies as "HttpOnly"
    samesite: {
      lax: true # mark all cookies as SameSite=lax
    }
  }
  # Add "; preload" and submit the site to hstspreload.org for best protection.
  config.hsts = "max-age=#{20.years.to_i}"
  config.x_frame_options = "DENY"
  config.x_content_type_options = "nosniff"
  config.x_xss_protection = "1; mode=block"
  config.x_download_options = "noopen"
  config.x_permitted_cross_domain_policies = "none"
  config.referrer_policy = "origin-when-cross-origin"
  config.csp = {
    # "meta" values. these will shape the header, but the values are not included in the header.
    preserve_schemes: true, # default: false. Schemes are removed from host sources to save bytes and discourage mixed content.

    # directive values: these values will directly translate into source directives
    default_src: %w(https: 'self'),
    base_uri: %w('self'),
    block_all_mixed_content: true, # see http://www.w3.org/TR/mixed-content/
    child_src: %w('self'), # if child-src isn't supported, the value for frame-src will be set.
    connect_src: %w(wss:),
    font_src: %w('self' data:),
    form_action: %w('self' github.com),
    frame_ancestors: %w('none'),
    img_src: %w(mycdn.com data:),
    manifest_src: %w('self'),
    media_src: %w(utoob.com),
    object_src: %w('self'),
    sandbox: true, # true and [] will set a maximally restrictive setting
    plugin_types: %w(application/x-shockwave-flash),
    script_src: %w('self'),
    style_src: %w('unsafe-inline'),
    upgrade_insecure_requests: true, # see https://www.w3.org/TR/upgrade-insecure-requests/
    report_uri: %w(https://report-uri.io/example-csp)
  }
  # This is available only from 3.5.0; use the `report_only: true` setting for 3.4.1 and below.
  config.csp_report_only = config.csp.merge({
    img_src: %w(somewhereelse.com),
    report_uri: %w(https://report-uri.io/example-csp-report-only)
  })
end

All headers except for PublicKeyPins and ClearSiteData have a default value. The default set of headers is:

Content-Security-Policy: default-src 'self' https:; font-src 'self' https: data:; img-src 'self' https: data:; object-src 'none'; script-src https:; style-src 'self' https: 'unsafe-inline'
Strict-Transport-Security: max-age=631138519
X-Content-Type-Options: nosniff
X-Download-Options: noopen
X-Frame-Options: sameorigin
X-Permitted-Cross-Domain-Policies: none
X-Xss-Protection: 1; mode=block

• Rack rack-secure_headers
• Node.js (express) helmet and hood
• Node.js (hapi) blankie
• J2EE Servlet >= 3.0 headlines
• ASP.NET - NWebsec
• Python - django-csp + commonware; django-security
• Go - secureheader
• Elixir secure_headers
• Dropwizard dropwizard-web-security
• Ember.js ember-cli-content-security-policy
• PHP secure-headers

Copyright 2013-2014 Twitter, Inc and other contributors.

Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0