Secure Headers Versions Save

3.4.0 the frame-src/child-src transition for Firefox.

Handle the child-src/frame-src transition semi-intelligently across versions. I think the code best describes the behavior here:

if supported_directives.include?(:child_src)
  @config[:child_src] = @config[:child_src] || @config[:frame_src]
else
  @config[:frame_src] = @config[:frame_src] || @config[:child_src]
end

@dankohn was seeing "already initialized" errors in his output. This change conditionally defines the constants.

@stefansundin noticed that supplying false to "boolean" CSP directives (e.g. upgrade-insecure-requests and block-all-mixed-content) would still include the value.

While not officially part of the spec and not implemented anywhere, support for the experimental referrer-policy header was preemptively added.

Additionally, two minor enhancements were added this version:

1. Warn when the HPKP report host is the same as the current host. By definition any generated reports would be reporting to a known compromised connection.
2. Filter unsupported CSP directives when using Edge. Previously, this was causing many warnings in the developer console.

3.2.0 Cookie settings and CSP hash sources

Cookies

SecureHeaders supports Secure, HttpOnly and SameSite cookies. These can be defined in the form of a boolean, or as a Hash for more refined configuration.

Note: Regardless of the configuration specified, Secure cookies are only enabled for HTTPS requests.

Boolean-based configuration

Boolean-based configuration is intended to globally enable or disable a specific cookie attribute.

config.cookies = {
  secure: true, # mark all cookies as Secure
  httponly: false, # do not mark any cookies as HttpOnly
}

Hash-based configuration

Hash-based configuration allows for fine-grained control.

config.cookies = {
  secure: { except: ['_guest'] }, # mark all but the `_guest` cookie as Secure
  httponly: { only: ['_rails_session'] }, # only mark the `_rails_session` cookie as HttpOnly
}

SameSite cookie configuration

SameSite cookies permit either Strict or Lax enforcement mode options.

config.cookies = {
  samesite: {
    strict: true # mark all cookies as SameSite=Strict
  }
}

Strict and Lax enforcement modes can also be specified using a Hash.

config.cookies = {
  samesite: {
    strict: { only: ['_rails_session'] },
    lax: { only: ['_guest'] }
  }
}

Hash

script/style-src hashes can be used to whitelist inline content that is static. This has the benefit of allowing inline content without opening up the possibility of dynamic javascript like you would with a nonce.

You can add hash sources directly to your policy :

::SecureHeaders::Configuration.default do |config|
   config.csp = {
     default_src: %w('self')

     # this is a made up value but browsers will show the expected hash in the console.
     script_src: %w(sha256-123456)
   }
 end

You can also use the automated inline script detection/collection/computation of hash source values in your app.

 rake secure_headers:generate_hashes

This will generate a file (config/config/secure_headers_generated_hashes.yml by default, you can override by setting ENV["secure_headers_generated_hashes_file"]) containing a mapping of file names with the array of hash values found on that page. When ActionView renders a given file, we check if there are any known hashes for that given file. If so, they are added as values to the header.

---
scripts:
  app/views/asdfs/index.html.erb:
  - "'sha256-yktKiAsZWmc8WpOyhnmhQoDf9G2dAZvuBBC+V0LGQhg='"
styles:
  app/views/asdfs/index.html.erb:
  - "'sha256-SLp6LO3rrKDJwsG9uJUxZapb4Wp2Zhj6Bu3l+d9rnAY='"
  - "'sha256-HSGHqlRoKmHAGTAJ2Rq0piXX4CnEbOl1ArNd6ejp2TE='"

Helpers

This will not compute dynamic hashes by design. The output of both helpers will be a plain script/style tag without modification and the known hashes for a given file will be added to script-src/style-src when hashed_javascript_tag and hashed_style_tag are used. You can use raise_error_on_unrecognized_hash = true to be extra paranoid that you have precomputed hash values for all of your inline content. By default, this will raise an error in non-production environments.

<%= hashed_style_tag do %>
body {
  background-color: black;
}
<% end %>

<%= hashed_style_tag do %>
body {
  font-size: 30px;
  font-color: green;
}
<% end %>

<%= hashed_javascript_tag do %>
console.log(1)
<% end %>

Content-Security-Policy: ...
 script-src 'sha256-yktKiAsZWmc8WpOyhnmhQoDf9G2dAZvuBBC+V0LGQhg=' ... ;
 style-src 'sha256-SLp6LO3rrKDJwsG9uJUxZapb4Wp2Zhj6Bu3l+d9rnAY=' 'sha256-HSGHqlRoKmHAGTAJ2Rq0piXX4CnEbOl1ArNd6ejp2TE=' ...;

See https://github.com/twitter/secureheaders/pull/239

This meant that when header caches were regenerated upon calling SecureHeaders.override(:name) and using it with use_secure_headers_override would result in default values for anything other than CSP/HPKP.

See https://github.com/twitter/secureheaders/pull/235

idempotent_additions? would return false when comparing OPT_OUT with OPT_OUT, causing header_hash_for to return a header cache with { nil => nil } which cause the middleware to blow up when { nil => nil } was merged into the rack header hash.

This is a regression in 3.1.0 only.

Now it returns true. I've added a test case to ensure that header_hash_for will never return such an element.

New feature: marking all cookies as secure. Added by @jmera in https://github.com/twitter/secureheaders/pull/231. In the future, we'll probably add the ability to whitelist individual cookies that should not be marked secure. PRs welcome.

Internal refactoring: In https://github.com/twitter/secureheaders/pull/232, we changed the way dynamic CSP is handled internally. The biggest benefit is that highly dynamic policies (which can happen with multiple append/override calls per request) are handled better:

1. Only the CSP header cache is busted when using a dynamic policy. All other headers are preserved and don't need to be generated. Dynamic X-Frame-Options changes modify the cache directly.
2. Idempotency checks for policy modifications are deferred until the end of the request lifecycle and only happen once, instead of per append/override call. The idempotency check itself is fairly expensive itself.
3. CSP header string is produced at most once per request.

Bug fix for handling policy merges where appending a non-default source value (report-uri, plugin-types, frame-ancestors, base-uri, and form-action) would be combined with the default-src value. Appending a directive that doesn't exist in the current policy combines the new value with default-src to mimic the actual behavior of the addition. However, this does not make sense for non-default-src values (a.k.a. "fetch directives") and can lead to unexpected behavior like a report-uri value of *. Previously, this config:

{
  default_src => %w(*)
}

When appending:

{
  report_uri => %w(https://report-uri.io/asdf)
}

Would result in default-src *; report-uri * which doesn't make any sense at all.