diff options
| -rw-r--r-- | app/helpers/jsonld_helper.rb | 72 | ||||
| -rw-r--r-- | app/services/activitypub/process_collection_service.rb | 18 | ||||
| -rw-r--r-- | spec/helpers/jsonld_helper_spec.rb | 82 |
3 files changed, 170 insertions, 2 deletions
diff --git a/app/helpers/jsonld_helper.rb b/app/helpers/jsonld_helper.rb index 841f27746..c6557817d 100644 --- a/app/helpers/jsonld_helper.rb +++ b/app/helpers/jsonld_helper.rb @@ -77,6 +77,78 @@ module JsonLdHelper 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) diff --git a/app/services/activitypub/process_collection_service.rb b/app/services/activitypub/process_collection_service.rb index 5f3d63bb3..eb008c40a 100644 --- a/app/services/activitypub/process_collection_service.rb +++ b/app/services/activitypub/process_collection_service.rb @@ -5,13 +5,27 @@ class ActivityPub::ProcessCollectionService < BaseService 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'] diff --git a/spec/helpers/jsonld_helper_spec.rb b/spec/helpers/jsonld_helper_spec.rb index 883a88b14..744a14f26 100644 --- a/spec/helpers/jsonld_helper_spec.rb +++ b/spec/helpers/jsonld_helper_spec.rb @@ -89,4 +89,86 @@ describe JsonLdHelper do 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 |