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b1f74ab59e
The strict-dynamic CSP directive is supported in all our target browsers, and makes for a much simpler configuration. Instead of allowlisting paths, we use a per-request nonce to authorize `<script>` tags, and then those scripts are allowed to load additional scripts (or add additional inline scripts) without restriction. This becomes especially useful when admins want to add external scripts like Google Tag Manager, or advertising scripts, which then go on to load a ton of other scripts. All script tags introduced via themes will automatically have the nonce attribute applied, so it should be zero-effort for theme developers. Plugins *may* need some changes if they are inserting their own script tags. This commit introduces a strict-dynamic-based CSP behind an experimental `content_security_policy_strict_dynamic` site setting.
100 lines
2.3 KiB
Ruby
100 lines
2.3 KiB
Ruby
# frozen_string_literal: true
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require "content_security_policy/default"
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class ContentSecurityPolicy
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class Builder
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EXTENDABLE_DIRECTIVES = %i[
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base_uri
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frame_ancestors
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manifest_src
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object_src
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script_src
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worker_src
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].freeze
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# Make extending these directives no-op, until core includes them in default CSP
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TO_BE_EXTENDABLE = %i[
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connect_src
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default_src
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font_src
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form_action
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frame_src
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img_src
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media_src
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prefetch_src
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style_src
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].freeze
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def initialize(base_url:)
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@directives = Default.new(base_url: base_url).directives
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@base_url = base_url
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end
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def <<(extension)
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return unless valid_extension?(extension)
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extension.each do |directive, sources|
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extend_directive(normalize_directive(directive), sources)
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end
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end
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def build
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policy = ActionDispatch::ContentSecurityPolicy.new
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@directives.each do |directive, sources|
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if sources.is_a?(Array)
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policy.public_send(directive, *sources)
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else
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policy.public_send(directive, sources)
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end
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end
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policy.build
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end
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private
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def normalize_directive(directive)
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directive.to_s.gsub("-", "_").to_sym
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end
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def normalize_source(source)
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if source.starts_with?("/")
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"#{@base_url}#{source}"
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else
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source
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end
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rescue URI::ParseError
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source
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end
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def extend_directive(directive, sources)
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return unless extendable?(directive)
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@directives[directive] ||= []
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sources = Array(sources).map { |s| normalize_source(s) }
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if SiteSetting.content_security_policy_strict_dynamic
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# Strip any sources which are ignored under strict-dynamic
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# If/when we make strict-dynamic the only option, we could print deprecation warnings
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# asking plugin/theme authors to remove the unnecessary config
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sources =
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sources.reject { |s| s == "'unsafe-inline'" || s == "'self'" || !s.start_with?("'") }
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end
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@directives[directive].concat(sources)
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@directives[directive].delete(:none) if @directives[directive].count > 1
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end
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def extendable?(directive)
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EXTENDABLE_DIRECTIVES.include?(directive)
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end
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def valid_extension?(extension)
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extension.is_a?(Hash)
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end
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end
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end
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