Merge pull request #1676 from ClearlyClaire/glitch-soc/merge-upstream

Merge upstream changes

2 files changed, 135 insertions, 0 deletions

diff --git a/app/helpers/context_helper.rb b/app/helpers/context_helper.rb
new file mode 100644
index 000000000..2f5fecaae
--- /dev/null
+++ b/app/helpers/context_helper.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module ContextHelper
+  NAMED_CONTEXT_MAP = {
+    activitystreams: 'https://www.w3.org/ns/activitystreams',
+    security: 'https://w3id.org/security/v1',
+  }.freeze
+
+  CONTEXT_EXTENSION_MAP = {
+    direct_message: { 'litepub' => 'http://litepub.social/ns#', 'directMessage' => 'litepub:directMessage' },
+    manually_approves_followers: { 'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers' },
+    sensitive: { 'sensitive' => 'as:sensitive' },
+    hashtag: { 'Hashtag' => 'as:Hashtag' },
+    moved_to: { 'movedTo' => { '@id' => 'as:movedTo', '@type' => '@id' } },
+    also_known_as: { 'alsoKnownAs' => { '@id' => 'as:alsoKnownAs', '@type' => '@id' } },
+    emoji: { 'toot' => 'http://joinmastodon.org/ns#', 'Emoji' => 'toot:Emoji' },
+    featured: { 'toot' => 'http://joinmastodon.org/ns#', 'featured' => { '@id' => 'toot:featured', '@type' => '@id' }, 'featuredTags' => { '@id' => 'toot:featuredTags', '@type' => '@id' } },
+    property_value: { 'schema' => 'http://schema.org#', 'PropertyValue' => 'schema:PropertyValue', 'value' => 'schema:value' },
+    atom_uri: { 'ostatus' => 'http://ostatus.org#', 'atomUri' => 'ostatus:atomUri' },
+    conversation: { 'ostatus' => 'http://ostatus.org#', 'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri', 'conversation' => 'ostatus:conversation' },
+    focal_point: { 'toot' => 'http://joinmastodon.org/ns#', 'focalPoint' => { '@container' => '@list', '@id' => 'toot:focalPoint' } },
+    blurhash: { 'toot' => 'http://joinmastodon.org/ns#', 'blurhash' => 'toot:blurhash' },
+    discoverable: { 'toot' => 'http://joinmastodon.org/ns#', 'discoverable' => 'toot:discoverable' },
+    voters_count: { 'toot' => 'http://joinmastodon.org/ns#', 'votersCount' => 'toot:votersCount' },
+    olm: { 'toot' => 'http://joinmastodon.org/ns#', 'Device' => 'toot:Device', 'Ed25519Signature' => 'toot:Ed25519Signature', 'Ed25519Key' => 'toot:Ed25519Key', 'Curve25519Key' => 'toot:Curve25519Key', 'EncryptedMessage' => 'toot:EncryptedMessage', 'publicKeyBase64' => 'toot:publicKeyBase64', 'deviceId' => 'toot:deviceId', 'claim' => { '@type' => '@id', '@id' => 'toot:claim' }, 'fingerprintKey' => { '@type' => '@id', '@id' => 'toot:fingerprintKey' }, 'identityKey' => { '@type' => '@id', '@id' => 'toot:identityKey' }, 'devices' => { '@type' => '@id', '@id' => 'toot:devices' }, 'messageFranking' => 'toot:messageFranking', 'messageType' => 'toot:messageType', 'cipherText' => 'toot:cipherText' },
+    suspended: { 'toot' => 'http://joinmastodon.org/ns#', 'suspended' => 'toot:suspended' },
+  }.freeze
+
+  def full_context
+    serialized_context(NAMED_CONTEXT_MAP, CONTEXT_EXTENSION_MAP)
+  end
+
+  def serialized_context(named_contexts_map, context_extensions_map)
+    context_array = []
+
+    named_contexts     = named_contexts_map.keys
+    context_extensions = context_extensions_map.keys
+
+    named_contexts.each do |key|
+      context_array << NAMED_CONTEXT_MAP[key]
+    end
+
+    extensions = context_extensions.each_with_object({}) do |key, h|
+      h.merge!(CONTEXT_EXTENSION_MAP[key])
+    end
+
+    context_array << extensions unless extensions.empty?
+
+    if context_array.size == 1
+      context_array.first
+    else
+      context_array
+    end
+  end
+end
diff --git a/app/helpers/jsonld_helper.rb b/app/helpers/jsonld_helper.rb
index c24d2ddf1..c6557817d 100644
--- a/app/helpers/jsonld_helper.rb
+++ b/app/helpers/jsonld_helper.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 module JsonLdHelper
+  include ContextHelper
+
   def equals_or_includes?(haystack, needle)
     haystack.is_a?(Array) ? haystack.include?(needle) : haystack == needle
   end
@@ -69,6 +71,84 @@ module JsonLdHelper
     graph.dump(:normalize)
   end
 
+  def compact(json)
+    compacted = JSON::LD::API.compact(json.without('signature'), full_context, documentLoader: method(:load_jsonld_context))
+    compacted['signature'] = json['signature']
+    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)