Refactor ActivityPub handling to prepare for non-Account actors (#19212)

* Move ActivityPub::FetchRemoteAccountService to ActivityPub::FetchRemoteActorService

ActivityPub::FetchRemoteAccountService is kept as a wrapper for when the actor is
specifically required to be an Account

* Refactor SignatureVerification to allow non-Account actors

* fixup! Move ActivityPub::FetchRemoteAccountService to ActivityPub::FetchRemoteActorService

* Refactor ActivityPub::FetchRemoteKeyService to potentially return non-Account actors

* Refactor inbound ActivityPub payload processing to accept non-Account actors

* Refactor inbound ActivityPub processing to accept activities relayed through non-Account

* Refactor how Account key URIs are built

* Refactor Request and drop unused key_id_format parameter

* Rename ActivityPub::Dereferencer `signature_account` to `signature_actor`

4 files changed, 103 insertions, 88 deletions

diff --git a/app/services/activitypub/fetch_remote_account_service.rb b/app/services/activitypub/fetch_remote_account_service.rb
index d7d739c59..ca7a8c6ca 100644
--- a/app/services/activitypub/fetch_remote_account_service.rb
+++ b/app/services/activitypub/fetch_remote_account_service.rb
@@ -1,80 +1,12 @@
 # frozen_string_literal: true
 
-class ActivityPub::FetchRemoteAccountService < BaseService
-  include JsonLdHelper
-  include DomainControlHelper
-  include WebfingerHelper
-
-  class Error < StandardError; end
-
-  SUPPORTED_TYPES = %w(Application Group Organization Person Service).freeze
-
+class ActivityPub::FetchRemoteAccountService < ActivityPub::FetchRemoteActorService
   # Does a WebFinger roundtrip on each call, unless `only_key` is true
   def call(uri, id: true, prefetched_body: nil, break_on_redirect: false, only_key: false, suppress_errors: true)
-    return if domain_not_allowed?(uri)
-    return ActivityPub::TagManager.instance.uri_to_resource(uri, Account) if ActivityPub::TagManager.instance.local_uri?(uri)
-
-    @json = begin
-      if prefetched_body.nil?
-        fetch_resource(uri, id)
-      else
-        body_to_json(prefetched_body, compare_id: id ? uri : nil)
-      end
-    rescue Oj::ParseError
-      raise Error, "Error parsing JSON-LD document #{uri}"
-    end
-
-    raise Error, "Error fetching actor JSON at #{uri}" if @json.nil?
-    raise Error, "Unsupported JSON-LD context for document #{uri}" unless supported_context?
-    raise Error, "Unexpected object type for actor #{uri} (expected any of: #{SUPPORTED_TYPES})" unless expected_type?
-    raise Error, "Actor #{uri} has moved to #{@json['movedTo']}" if break_on_redirect && @json['movedTo'].present?
-
-    @uri      = @json['id']
-    @username = @json['preferredUsername']
-    @domain   = Addressable::URI.parse(@uri).normalized_host
-
-    check_webfinger! unless only_key
-
-    ActivityPub::ProcessAccountService.new.call(@username, @domain, @json, only_key: only_key, verified_webfinger: !only_key)
-  rescue Error => e
-    Rails.logger.debug "Fetching account #{uri} failed: #{e.message}"
-    raise unless suppress_errors
-  end
-
-  private
-
-  def check_webfinger!
-    webfinger                            = webfinger!("acct:#{@username}@#{@domain}")
-    confirmed_username, confirmed_domain = split_acct(webfinger.subject)
-
-    if @username.casecmp(confirmed_username).zero? && @domain.casecmp(confirmed_domain).zero?
-      raise Error, "Webfinger response for #{@username}@#{@domain} does not loop back to #{@uri}" if webfinger.link('self', 'href') != @uri
-      return
-    end
-
-    webfinger                            = webfinger!("acct:#{confirmed_username}@#{confirmed_domain}")
-    @username, @domain                   = split_acct(webfinger.subject)
-
-    unless confirmed_username.casecmp(@username).zero? && confirmed_domain.casecmp(@domain).zero?
-      raise Webfinger::RedirectError, "Too many webfinger redirects for URI #{uri} (stopped at #{@username}@#{@domain})"
-    end
-
-    raise Error, "Webfinger response for #{@username}@#{@domain} does not loop back to #{@uri}" if webfinger.link('self', 'href') != @uri
-  rescue Webfinger::RedirectError => e
-    raise Error, e.message
-  rescue Webfinger::Error => e
-    raise Error, "Webfinger error when resolving #{@username}@#{@domain}: #{e.message}"
-  end
-
-  def split_acct(acct)
-    acct.gsub(/\Aacct:/, '').split('@')
-  end
-
-  def supported_context?
-    super(@json)
-  end
+    actor = super
+    return actor if actor.nil? || actor.is_a?(Account)
 
-  def expected_type?
-    equals_or_includes_any?(@json['type'], SUPPORTED_TYPES)
+    Rails.logger.debug "Fetching account #{uri} failed: Expected Account, got #{actor.class.name}"
+    raise Error, "Expected Account, got #{actor.class.name}" unless suppress_errors
   end
 end
diff --git a/app/services/activitypub/fetch_remote_actor_service.rb b/app/services/activitypub/fetch_remote_actor_service.rb
new file mode 100644
index 000000000..17bf2f287
--- /dev/null
+++ b/app/services/activitypub/fetch_remote_actor_service.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+
+class ActivityPub::FetchRemoteActorService < BaseService
+  include JsonLdHelper
+  include DomainControlHelper
+  include WebfingerHelper
+
+  class Error < StandardError; end
+
+  SUPPORTED_TYPES = %w(Application Group Organization Person Service).freeze
+
+  # Does a WebFinger roundtrip on each call, unless `only_key` is true
+  def call(uri, id: true, prefetched_body: nil, break_on_redirect: false, only_key: false, suppress_errors: true)
+    return if domain_not_allowed?(uri)
+    return ActivityPub::TagManager.instance.uri_to_actor(uri) if ActivityPub::TagManager.instance.local_uri?(uri)
+
+    @json = begin
+      if prefetched_body.nil?
+        fetch_resource(uri, id)
+      else
+        body_to_json(prefetched_body, compare_id: id ? uri : nil)
+      end
+    rescue Oj::ParseError
+      raise Error, "Error parsing JSON-LD document #{uri}"
+    end
+
+    raise Error, "Error fetching actor JSON at #{uri}" if @json.nil?
+    raise Error, "Unsupported JSON-LD context for document #{uri}" unless supported_context?
+    raise Error, "Unexpected object type for actor #{uri} (expected any of: #{SUPPORTED_TYPES})" unless expected_type?
+    raise Error, "Actor #{uri} has moved to #{@json['movedTo']}" if break_on_redirect && @json['movedTo'].present?
+
+    @uri      = @json['id']
+    @username = @json['preferredUsername']
+    @domain   = Addressable::URI.parse(@uri).normalized_host
+
+    check_webfinger! unless only_key
+
+    ActivityPub::ProcessAccountService.new.call(@username, @domain, @json, only_key: only_key, verified_webfinger: !only_key)
+  rescue Error => e
+    Rails.logger.debug "Fetching actor #{uri} failed: #{e.message}"
+    raise unless suppress_errors
+  end
+
+  private
+
+  def check_webfinger!
+    webfinger                            = webfinger!("acct:#{@username}@#{@domain}")
+    confirmed_username, confirmed_domain = split_acct(webfinger.subject)
+
+    if @username.casecmp(confirmed_username).zero? && @domain.casecmp(confirmed_domain).zero?
+      raise Error, "Webfinger response for #{@username}@#{@domain} does not loop back to #{@uri}" if webfinger.link('self', 'href') != @uri
+      return
+    end
+
+    webfinger                            = webfinger!("acct:#{confirmed_username}@#{confirmed_domain}")
+    @username, @domain                   = split_acct(webfinger.subject)
+
+    unless confirmed_username.casecmp(@username).zero? && confirmed_domain.casecmp(@domain).zero?
+      raise Webfinger::RedirectError, "Too many webfinger redirects for URI #{uri} (stopped at #{@username}@#{@domain})"
+    end
+
+    raise Error, "Webfinger response for #{@username}@#{@domain} does not loop back to #{@uri}" if webfinger.link('self', 'href') != @uri
+  rescue Webfinger::RedirectError => e
+    raise Error, e.message
+  rescue Webfinger::Error => e
+    raise Error, "Webfinger error when resolving #{@username}@#{@domain}: #{e.message}"
+  end
+
+  def split_acct(acct)
+    acct.gsub(/\Aacct:/, '').split('@')
+  end
+
+  def supported_context?
+    super(@json)
+  end
+
+  def expected_type?
+    equals_or_includes_any?(@json['type'], SUPPORTED_TYPES)
+  end
+end
diff --git a/app/services/activitypub/fetch_remote_key_service.rb b/app/services/activitypub/fetch_remote_key_service.rb
index 01008d883..fe8f60b55 100644
--- a/app/services/activitypub/fetch_remote_key_service.rb
+++ b/app/services/activitypub/fetch_remote_key_service.rb
@@ -5,7 +5,7 @@ class ActivityPub::FetchRemoteKeyService < BaseService
 
   class Error < StandardError; end
 
-  # Returns account that owns the key
+  # Returns actor that owns the key
   def call(uri, id: true, prefetched_body: nil, suppress_errors: true)
     raise Error, 'No key URI given' if uri.blank?
 
@@ -27,7 +27,7 @@ class ActivityPub::FetchRemoteKeyService < BaseService
     raise Error, "Unable to fetch key JSON at #{uri}" if @json.nil?
     raise Error, "Unsupported JSON-LD context for document #{uri}" unless supported_context?(@json)
     raise Error, "Unexpected object type for key #{uri}" unless expected_type?
-    return find_account(@json['id'], @json, suppress_errors) if person?
+    return find_actor(@json['id'], @json, suppress_errors) if person?
 
     @owner = fetch_resource(owner_uri, true)
 
@@ -36,7 +36,7 @@ class ActivityPub::FetchRemoteKeyService < BaseService
     raise Error, "Unexpected object type for actor #{owner_uri} (expected any of: #{SUPPORTED_TYPES})" unless expected_owner_type?
     raise Error, "publicKey id for #{owner_uri} does not correspond to #{@json['id']}" unless confirmed_owner?
 
-    find_account(owner_uri, @owner, suppress_errors)
+    find_actor(owner_uri, @owner, suppress_errors)
   rescue Error => e
     Rails.logger.debug "Fetching key #{uri} failed: #{e.message}"
     raise unless suppress_errors
@@ -44,18 +44,18 @@ class ActivityPub::FetchRemoteKeyService < BaseService
 
   private
 
-  def find_account(uri, prefetched_body, suppress_errors)
-    account   = ActivityPub::TagManager.instance.uri_to_resource(uri, Account)
-    account ||= ActivityPub::FetchRemoteAccountService.new.call(uri, prefetched_body: prefetched_body, suppress_errors: suppress_errors)
-    account
+  def find_actor(uri, prefetched_body, suppress_errors)
+    actor   = ActivityPub::TagManager.instance.uri_to_actor(uri)
+    actor ||= ActivityPub::FetchRemoteActorService.new.call(uri, prefetched_body: prefetched_body, suppress_errors: suppress_errors)
+    actor
   end
 
   def expected_type?
-    person? || public_key?
+    actor? || public_key?
   end
 
-  def person?
-    equals_or_includes_any?(@json['type'], ActivityPub::FetchRemoteAccountService::SUPPORTED_TYPES)
+  def actor?
+    equals_or_includes_any?(@json['type'], ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES)
   end
 
   def public_key?
@@ -67,7 +67,7 @@ class ActivityPub::FetchRemoteKeyService < BaseService
   end
 
   def expected_owner_type?
-    equals_or_includes_any?(@owner['type'], ActivityPub::FetchRemoteAccountService::SUPPORTED_TYPES)
+    equals_or_includes_any?(@owner['type'], ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES)
   end
 
   def confirmed_owner?
diff --git a/app/services/activitypub/process_collection_service.rb b/app/services/activitypub/process_collection_service.rb
index eb008c40a..fffe30195 100644
--- a/app/services/activitypub/process_collection_service.rb
+++ b/app/services/activitypub/process_collection_service.rb
@@ -3,8 +3,8 @@
 class ActivityPub::ProcessCollectionService < BaseService
   include JsonLdHelper
 
-  def call(body, account, **options)
-    @account = account
+  def call(body, actor, **options)
+    @account = actor
     @json    = original_json = Oj.load(body, mode: :strict)
     @options = options
 
@@ -16,6 +16,7 @@ class ActivityPub::ProcessCollectionService < BaseService
     end
 
     return if !supported_context? || (different_actor? && verify_account!.nil?) || suspended_actor? || @account.local?
+    return unless @account.is_a?(Account)
 
     if @json['signature'].present?
       # We have verified the signature, but in the compaction step above, might
@@ -66,8 +67,10 @@ class ActivityPub::ProcessCollectionService < BaseService
   end
 
   def verify_account!
-    @options[:relayed_through_account] = @account
-    @account = ActivityPub::LinkedDataSignature.new(@json).verify_account!
+    @options[:relayed_through_actor] = @account
+    @account = ActivityPub::LinkedDataSignature.new(@json).verify_actor!
+    @account = nil unless @account.is_a?(Account)
+    @account
   rescue JSON::LD::JsonLdError => e
     Rails.logger.debug "Could not verify LD-Signature for #{value_or_id(@json['actor'])}: #{e.message}"
     nil