compacted
end
+ # Patches a JSON-LD document to avoid compatibility issues on redistribution
+ #
+ # Since compacting a JSON-LD document against Mastodon's built-in vocabulary
+ # means other extension namespaces will be expanded, malformed JSON-LD
+ # attributes lost, and some values “unexpectedly” compacted this method
+ # patches the following likely sources of incompatibility:
+ # - 'https://www.w3.org/ns/activitystreams#Public' being compacted to
+ # 'as:Public' (for instance, pre-3.4.0 Mastodon does not understand
+ # 'as:Public')
+ # - single-item arrays being compacted to the item itself (`[foo]` being
+ # compacted to `foo`)
+ #
+ # It is not always possible for `patch_for_forwarding!` to produce a document
+ # deemed safe for forwarding. Use `safe_for_forwarding?` to check the status
+ # of the output document.
+ #
+ # @param original [Hash] The original JSON-LD document used as reference
+ # @param compacted [Hash] The compacted JSON-LD document to be patched
+ # @return [void]
+ def patch_for_forwarding!(original, compacted)
+ original.without('@context', 'signature').each do |key, value|
+ next if value.nil? || !compacted.key?(key)
+
+ compacted_value = compacted[key]
+ if value.is_a?(Hash) && compacted_value.is_a?(Hash)
+ patch_for_forwarding!(value, compacted_value)
+ elsif value.is_a?(Array)
+ compacted_value = [compacted_value] unless compacted_value.is_a?(Array)
+ return if value.size != compacted_value.size
+
+ compacted[key] = value.zip(compacted_value).map do |v, vc|
+ if v.is_a?(Hash) && vc.is_a?(Hash)
+ patch_for_forwarding!(v, vc)
+ vc
+ elsif v == 'https://www.w3.org/ns/activitystreams#Public' && vc == 'as:Public'
+ v
+ else
+ vc
+ end
+ end
+ elsif value == 'https://www.w3.org/ns/activitystreams#Public' && compacted_value == 'as:Public'
+ compacted[key] = value
+ end
+ end
+ end
+
+ # Tests whether a JSON-LD compaction is deemed safe for redistribution,
+ # that is, if it doesn't change its meaning to consumers that do not actually
+ # handle JSON-LD, but rely on values being serialized in a certain way.
+ #
+ # See `patch_for_forwarding!` for details.
+ #
+ # @param original [Hash] The original JSON-LD document used as reference
+ # @param compacted [Hash] The compacted JSON-LD document to be patched
+ # @return [Boolean] Whether the patched document is deemed safe
+ def safe_for_forwarding?(original, compacted)
+ original.without('@context', 'signature').all? do |key, value|
+ compacted_value = compacted[key]
+ return false unless value.class == compacted_value.class
+
+ if value.is_a?(Hash)
+ safe_for_forwarding?(value, compacted_value)
+ elsif value.is_a?(Array)
+ value.zip(compacted_value).all? do |v, vc|
+ v.is_a?(Hash) ? (vc.is_a?(Hash) && safe_for_forwarding?(v, vc)) : v == vc
+ end
+ else
+ value == compacted_value
+ end
+ end
+ end
+
def fetch_resource(uri, id, on_behalf_of = nil)
unless id
json = fetch_resource_without_id_validation(uri, on_behalf_of)
def call(body, account, **options)
@account = account
- @json = Oj.load(body, mode: :strict)
+ @json = original_json = Oj.load(body, mode: :strict)
@options = options
- @json = compact(@json) if @json['signature'].is_a?(Hash)
+ begin
+ @json = compact(@json) if @json['signature'].is_a?(Hash)
+ rescue JSON::LD::JsonLdError => e
+ Rails.logger.debug "Error when compacting JSON-LD document for #{value_or_id(@json['actor'])}: #{e.message}"
+ @json = original_json.without('signature')
+ end
return if !supported_context? || (different_actor? && verify_account!.nil?) || suspended_actor? || @account.local?
+ if @json['signature'].present?
+ # We have verified the signature, but in the compaction step above, might
+ # have introduced incompatibilities with other servers that do not
+ # normalize the JSON-LD documents (for instance, previous Mastodon
+ # versions), so skip redistribution if we can't get a safe document.
+ patch_for_forwarding!(original_json, @json)
+ @json.delete('signature') unless safe_for_forwarding?(original_json, @json)
+ end
+
case @json['type']
when 'Collection', 'CollectionPage'
process_items @json['items']
expect(fetch_resource_without_id_validation('https://host.test/')).to eq({})
end
end
+
+ context 'compaction and forwarding' do
+ let(:json) do
+ {
+ '@context' => [
+ 'https://www.w3.org/ns/activitystreams',
+ 'https://w3id.org/security/v1',
+ {
+ 'obsolete' => 'http://ostatus.org#',
+ 'convo' => 'obsolete:conversation',
+ 'new' => 'https://obscure-unreleased-test.joinmastodon.org/#',
+ },
+ ],
+ 'type' => 'Create',
+ 'to' => ['https://www.w3.org/ns/activitystreams#Public'],
+ 'object' => {
+ 'id' => 'https://example.com/status',
+ 'type' => 'Note',
+ 'inReplyTo' => nil,
+ 'convo' => 'https://example.com/conversation',
+ 'tag' => [
+ {
+ 'type' => 'Mention',
+ 'href' => ['foo'],
+ }
+ ],
+ },
+ 'signature' => {
+ 'type' => 'RsaSignature2017',
+ 'created' => '2022-02-02T12:00:00Z',
+ 'creator' => 'https://example.com/actor#main-key',
+ 'signatureValue' => 'some-sig',
+ },
+ }
+ end
+
+ describe '#compact' do
+ it 'properly compacts JSON-LD with alternative context definitions' do
+ expect(compact(json).dig('object', 'conversation')).to eq 'https://example.com/conversation'
+ end
+
+ it 'compacts single-item arrays' do
+ expect(compact(json).dig('object', 'tag', 'href')).to eq 'foo'
+ end
+
+ it 'compacts the activistreams Public collection' do
+ expect(compact(json)['to']).to eq 'as:Public'
+ end
+
+ it 'properly copies signature' do
+ expect(compact(json)['signature']).to eq json['signature']
+ end
+ end
+
+ describe 'patch_for_forwarding!' do
+ it 'properly patches incompatibilities' do
+ json['object'].delete('convo')
+ compacted = compact(json)
+ patch_for_forwarding!(json, compacted)
+ expect(compacted['to']).to eq ['https://www.w3.org/ns/activitystreams#Public']
+ expect(compacted.dig('object', 'tag', 0, 'href')).to eq ['foo']
+ expect(safe_for_forwarding?(json, compacted)).to eq true
+ end
+ end
+
+ describe 'safe_for_forwarding?' do
+ it 'deems a safe compacting as such' do
+ json['object'].delete('convo')
+ compacted = compact(json)
+ deemed_compatible = patch_for_forwarding!(json, compacted)
+ expect(compacted['to']).to eq ['https://www.w3.org/ns/activitystreams#Public']
+ expect(safe_for_forwarding?(json, compacted)).to eq true
+ end
+
+ it 'deems an unsafe compacting as such' do
+ compacted = compact(json)
+ deemed_compatible = patch_for_forwarding!(json, compacted)
+ expect(compacted['to']).to eq ['https://www.w3.org/ns/activitystreams#Public']
+ expect(safe_for_forwarding?(json, compacted)).to eq false
+ end
+ end
+ end
end
cat aescling's git repositories / mastodon.git / commitdiff