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`

41 files changed, 436 insertions, 180 deletions

diff --git a/app/controllers/accounts_controller.rb b/app/controllers/accounts_controller.rb
index fe7d934dc..d92f91b30 100644
--- a/app/controllers/accounts_controller.rb
+++ b/app/controllers/accounts_controller.rb
@@ -7,7 +7,7 @@ class AccountsController < ApplicationController
   include AccountControllerConcern
   include SignatureAuthentication
 
-  before_action :require_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
+  before_action :require_account_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
   before_action :set_cache_headers
   before_action :set_body_classes
 
diff --git a/app/controllers/activitypub/claims_controller.rb b/app/controllers/activitypub/claims_controller.rb
index 08ad952df..339333e46 100644
--- a/app/controllers/activitypub/claims_controller.rb
+++ b/app/controllers/activitypub/claims_controller.rb
@@ -6,7 +6,7 @@ class ActivityPub::ClaimsController < ActivityPub::BaseController
 
   skip_before_action :authenticate_user!
 
-  before_action :require_signature!
+  before_action :require_account_signature!
   before_action :set_claim_result
 
   def create
diff --git a/app/controllers/activitypub/collections_controller.rb b/app/controllers/activitypub/collections_controller.rb
index e4e994a98..d94a285ea 100644
--- a/app/controllers/activitypub/collections_controller.rb
+++ b/app/controllers/activitypub/collections_controller.rb
@@ -4,7 +4,7 @@ class ActivityPub::CollectionsController < ActivityPub::BaseController
   include SignatureVerification
   include AccountOwnedConcern
 
-  before_action :require_signature!, if: :authorized_fetch_mode?
+  before_action :require_account_signature!, if: :authorized_fetch_mode?
   before_action :set_items
   before_action :set_size
   before_action :set_type
diff --git a/app/controllers/activitypub/followers_synchronizations_controller.rb b/app/controllers/activitypub/followers_synchronizations_controller.rb
index 940b77cf0..4e445bcb1 100644
--- a/app/controllers/activitypub/followers_synchronizations_controller.rb
+++ b/app/controllers/activitypub/followers_synchronizations_controller.rb
@@ -4,7 +4,7 @@ class ActivityPub::FollowersSynchronizationsController < ActivityPub::BaseContro
   include SignatureVerification
   include AccountOwnedConcern
 
-  before_action :require_signature!
+  before_action :require_account_signature!
   before_action :set_items
   before_action :set_cache_headers
 
diff --git a/app/controllers/activitypub/inboxes_controller.rb b/app/controllers/activitypub/inboxes_controller.rb
index 92dcb5ac7..5ee85474e 100644
--- a/app/controllers/activitypub/inboxes_controller.rb
+++ b/app/controllers/activitypub/inboxes_controller.rb
@@ -6,7 +6,7 @@ class ActivityPub::InboxesController < ActivityPub::BaseController
   include AccountOwnedConcern
 
   before_action :skip_unknown_actor_activity
-  before_action :require_signature!
+  before_action :require_actor_signature!
   skip_before_action :authenticate_user!
 
   def create
@@ -49,17 +49,17 @@ class ActivityPub::InboxesController < ActivityPub::BaseController
   end
 
   def upgrade_account
-    if signed_request_account.ostatus?
+    if signed_request_account&.ostatus?
       signed_request_account.update(last_webfingered_at: nil)
       ResolveAccountWorker.perform_async(signed_request_account.acct)
     end
 
-    DeliveryFailureTracker.reset!(signed_request_account.inbox_url)
+    DeliveryFailureTracker.reset!(signed_request_actor.inbox_url)
   end
 
   def process_collection_synchronization
     raw_params = request.headers['Collection-Synchronization']
-    return if raw_params.blank? || ENV['DISABLE_FOLLOWERS_SYNCHRONIZATION'] == 'true'
+    return if raw_params.blank? || ENV['DISABLE_FOLLOWERS_SYNCHRONIZATION'] == 'true' || signed_request_account.nil?
 
     # Re-using the syntax for signature parameters
     tree   = SignatureParamsParser.new.parse(raw_params)
@@ -71,6 +71,6 @@ class ActivityPub::InboxesController < ActivityPub::BaseController
   end
 
   def process_payload
-    ActivityPub::ProcessingWorker.perform_async(signed_request_account.id, body, @account&.id)
+    ActivityPub::ProcessingWorker.perform_async(signed_request_actor.id, body, @account&.id, signed_request_actor.class.name)
   end
 end
diff --git a/app/controllers/activitypub/outboxes_controller.rb b/app/controllers/activitypub/outboxes_controller.rb
index cd3992502..60d201f76 100644
--- a/app/controllers/activitypub/outboxes_controller.rb
+++ b/app/controllers/activitypub/outboxes_controller.rb
@@ -6,7 +6,7 @@ class ActivityPub::OutboxesController < ActivityPub::BaseController
   include SignatureVerification
   include AccountOwnedConcern
 
-  before_action :require_signature!, if: :authorized_fetch_mode?
+  before_action :require_account_signature!, if: :authorized_fetch_mode?
   before_action :set_statuses
   before_action :set_cache_headers
 
diff --git a/app/controllers/activitypub/replies_controller.rb b/app/controllers/activitypub/replies_controller.rb
index 4ff7cfa08..8e0f9de2e 100644
--- a/app/controllers/activitypub/replies_controller.rb
+++ b/app/controllers/activitypub/replies_controller.rb
@@ -7,7 +7,7 @@ class ActivityPub::RepliesController < ActivityPub::BaseController
 
   DESCENDANTS_LIMIT = 60
 
-  before_action :require_signature!, if: :authorized_fetch_mode?
+  before_action :require_account_signature!, if: :authorized_fetch_mode?
   before_action :set_status
   before_action :set_cache_headers
   before_action :set_replies
diff --git a/app/controllers/concerns/signature_verification.rb b/app/controllers/concerns/signature_verification.rb
index 4da068aed..2394574b3 100644
--- a/app/controllers/concerns/signature_verification.rb
+++ b/app/controllers/concerns/signature_verification.rb
@@ -45,10 +45,14 @@ module SignatureVerification
     end
   end
 
-  def require_signature!
+  def require_account_signature!
     render plain: signature_verification_failure_reason, status: signature_verification_failure_code unless signed_request_account
   end
 
+  def require_actor_signature!
+    render plain: signature_verification_failure_reason, status: signature_verification_failure_code unless signed_request_actor
+  end
+
   def signed_request?
     request.headers['Signature'].present?
   end
@@ -68,7 +72,11 @@ module SignatureVerification
   end
 
   def signed_request_account
-    return @signed_request_account if defined?(@signed_request_account)
+    signed_request_actor.is_a?(Account) ? signed_request_actor : nil
+  end
+
+  def signed_request_actor
+    return @signed_request_actor if defined?(@signed_request_actor)
 
     raise SignatureVerificationError, 'Request not signed' unless signed_request?
     raise SignatureVerificationError, 'Incompatible request signature. keyId and signature are required' if missing_required_signature_parameters?
@@ -78,22 +86,22 @@ module SignatureVerification
     verify_signature_strength!
     verify_body_digest!
 
-    account = account_from_key_id(signature_params['keyId'])
+    actor = actor_from_key_id(signature_params['keyId'])
 
-    raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if account.nil?
+    raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if actor.nil?
 
     signature             = Base64.decode64(signature_params['signature'])
     compare_signed_string = build_signed_string
 
-    return account unless verify_signature(account, signature, compare_signed_string).nil?
+    return actor unless verify_signature(actor, signature, compare_signed_string).nil?
 
-    account = stoplight_wrap_request { account.possibly_stale? ? account.refresh! : account_refresh_key(account) }
+    actor = stoplight_wrap_request { actor_refresh_key!(actor) }
 
-    raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if account.nil?
+    raise SignatureVerificationError, "Public key not found for key #{signature_params['keyId']}" if actor.nil?
 
-    return account unless verify_signature(account, signature, compare_signed_string).nil?
+    return actor unless verify_signature(actor, signature, compare_signed_string).nil?
 
-    fail_with! "Verification failed for #{account.username}@#{account.domain} #{account.uri} using rsa-sha256 (RSASSA-PKCS1-v1_5 with SHA-256)"
+    fail_with! "Verification failed for #{actor.to_log_human_identifier} #{actor.uri} using rsa-sha256 (RSASSA-PKCS1-v1_5 with SHA-256)"
   rescue SignatureVerificationError => e
     fail_with! e.message
   rescue HTTP::Error, OpenSSL::SSL::SSLError => e
@@ -112,7 +120,7 @@ module SignatureVerification
 
   def fail_with!(message)
     @signature_verification_failure_reason = message
-    @signed_request_account = nil
+    @signed_request_actor = nil
   end
 
   def signature_params
@@ -160,10 +168,10 @@ module SignatureVerification
     raise SignatureVerificationError, "Invalid Digest value. Computed SHA-256 digest: #{body_digest}; given: #{sha256[1]}"
   end
 
-  def verify_signature(account, signature, compare_signed_string)
-    if account.keypair.public_key.verify(OpenSSL::Digest.new('SHA256'), signature, compare_signed_string)
-      @signed_request_account = account
-      @signed_request_account
+  def verify_signature(actor, signature, compare_signed_string)
+    if actor.keypair.public_key.verify(OpenSSL::Digest.new('SHA256'), signature, compare_signed_string)
+      @signed_request_actor = actor
+      @signed_request_actor
     end
   rescue OpenSSL::PKey::RSAError
     nil
@@ -226,7 +234,7 @@ module SignatureVerification
     signature_params['keyId'].blank? || signature_params['signature'].blank?
   end
 
-  def account_from_key_id(key_id)
+  def actor_from_key_id(key_id)
     domain = key_id.start_with?('acct:') ? key_id.split('@').last : key_id
 
     if domain_not_allowed?(domain)
@@ -237,13 +245,13 @@ module SignatureVerification
     if key_id.start_with?('acct:')
       stoplight_wrap_request { ResolveAccountService.new.call(key_id.gsub(/\Aacct:/, ''), suppress_errors: false) }
     elsif !ActivityPub::TagManager.instance.local_uri?(key_id)
-      account   = ActivityPub::TagManager.instance.uri_to_resource(key_id, Account)
+      account   = ActivityPub::TagManager.instance.uri_to_actor(key_id)
       account ||= stoplight_wrap_request { ActivityPub::FetchRemoteKeyService.new.call(key_id, id: false, suppress_errors: false) }
       account
     end
   rescue Mastodon::PrivateNetworkAddressError => e
     raise SignatureVerificationError, "Requests to private network addresses are disallowed (tried to query #{e.host})"
-  rescue Mastodon::HostValidationError, ActivityPub::FetchRemoteAccountService::Error, ActivityPub::FetchRemoteKeyService::Error, Webfinger::Error => e
+  rescue Mastodon::HostValidationError, ActivityPub::FetchRemoteActorService::Error, ActivityPub::FetchRemoteKeyService::Error, Webfinger::Error => e
     raise SignatureVerificationError, e.message
   end
 
@@ -255,12 +263,14 @@ module SignatureVerification
       .run
   end
 
-  def account_refresh_key(account)
-    return if account.local? || !account.activitypub?
-    ActivityPub::FetchRemoteAccountService.new.call(account.uri, only_key: true, suppress_errors: false)
+  def actor_refresh_key!(actor)
+    return if actor.local? || !actor.activitypub?
+    return actor.refresh! if actor.respond_to?(:refresh!) && actor.possibly_stale?
+
+    ActivityPub::FetchRemoteActorService.new.call(actor.uri, only_key: true, suppress_errors: false)
   rescue Mastodon::PrivateNetworkAddressError => e
     raise SignatureVerificationError, "Requests to private network addresses are disallowed (tried to query #{e.host})"
-  rescue Mastodon::HostValidationError, ActivityPub::FetchRemoteAccountService::Error, Webfinger::Error => e
+  rescue Mastodon::HostValidationError, ActivityPub::FetchRemoteActorService::Error, Webfinger::Error => e
     raise SignatureVerificationError, e.message
   end
 end
diff --git a/app/controllers/follower_accounts_controller.rb b/app/controllers/follower_accounts_controller.rb
index f3f8336c9..da7bb4ed2 100644
--- a/app/controllers/follower_accounts_controller.rb
+++ b/app/controllers/follower_accounts_controller.rb
@@ -4,7 +4,7 @@ class FollowerAccountsController < ApplicationController
   include AccountControllerConcern
   include SignatureVerification
 
-  before_action :require_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
+  before_action :require_account_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
   before_action :set_cache_headers
 
   skip_around_action :set_locale, if: -> { request.format == :json }
diff --git a/app/controllers/following_accounts_controller.rb b/app/controllers/following_accounts_controller.rb
index 69f0321f8..c37e3b68c 100644
--- a/app/controllers/following_accounts_controller.rb
+++ b/app/controllers/following_accounts_controller.rb
@@ -4,7 +4,7 @@ class FollowingAccountsController < ApplicationController
   include AccountControllerConcern
   include SignatureVerification
 
-  before_action :require_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
+  before_action :require_account_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
   before_action :set_cache_headers
 
   skip_around_action :set_locale, if: -> { request.format == :json }
diff --git a/app/controllers/statuses_controller.rb b/app/controllers/statuses_controller.rb
index c52170d08..7d9db4d5b 100644
--- a/app/controllers/statuses_controller.rb
+++ b/app/controllers/statuses_controller.rb
@@ -8,7 +8,7 @@ class StatusesController < ApplicationController
 
   layout 'public'
 
-  before_action :require_signature!, only: [:show, :activity], if: -> { request.format == :json && authorized_fetch_mode? }
+  before_action :require_account_signature!, only: [:show, :activity], if: -> { request.format == :json && authorized_fetch_mode? }
   before_action :set_status
   before_action :set_instance_presenter
   before_action :set_link_headers
diff --git a/app/controllers/tags_controller.rb b/app/controllers/tags_controller.rb
index b82da8f0c..6dbc2667a 100644
--- a/app/controllers/tags_controller.rb
+++ b/app/controllers/tags_controller.rb
@@ -8,7 +8,7 @@ class TagsController < ApplicationController
 
   layout 'public'
 
-  before_action :require_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
+  before_action :require_account_signature!, if: -> { request.format == :json && authorized_fetch_mode? }
   before_action :authenticate_user!, if: :whitelist_mode?
   before_action :set_local
   before_action :set_tag
diff --git a/app/lib/activitypub/activity.rb b/app/lib/activitypub/activity.rb
index 7ff06ea39..f4c67cccd 100644
--- a/app/lib/activitypub/activity.rb
+++ b/app/lib/activitypub/activity.rb
@@ -116,12 +116,12 @@ class ActivityPub::Activity
   def dereference_object!
     return unless @object.is_a?(String)
 
-    dereferencer = ActivityPub::Dereferencer.new(@object, permitted_origin: @account.uri, signature_account: signed_fetch_account)
+    dereferencer = ActivityPub::Dereferencer.new(@object, permitted_origin: @account.uri, signature_actor: signed_fetch_actor)
 
     @object = dereferencer.object unless dereferencer.object.nil?
   end
 
-  def signed_fetch_account
+  def signed_fetch_actor
     return Account.find(@options[:delivered_to_account_id]) if @options[:delivered_to_account_id].present?
 
     first_mentioned_local_account || first_local_follower
@@ -163,15 +163,15 @@ class ActivityPub::Activity
   end
 
   def followed_by_local_accounts?
-    @account.passive_relationships.exists? || @options[:relayed_through_account]&.passive_relationships&.exists?
+    @account.passive_relationships.exists? || (@options[:relayed_through_actor].is_a?(Account) && @options[:relayed_through_actor].passive_relationships&.exists?)
   end
 
   def requested_through_relay?
-    @options[:relayed_through_account] && Relay.find_by(inbox_url: @options[:relayed_through_account].inbox_url)&.enabled?
+    @options[:relayed_through_actor] && Relay.find_by(inbox_url: @options[:relayed_through_actor].inbox_url)&.enabled?
   end
 
   def reject_payload!
-    Rails.logger.info("Rejected #{@json['type']} activity #{@json['id']} from #{@account.uri}#{@options[:relayed_through_account] && "via #{@options[:relayed_through_account].uri}"}")
+    Rails.logger.info("Rejected #{@json['type']} activity #{@json['id']} from #{@account.uri}#{@options[:relayed_through_actor] && "via #{@options[:relayed_through_actor].uri}"}")
     nil
   end
 end
diff --git a/app/lib/activitypub/dereferencer.rb b/app/lib/activitypub/dereferencer.rb
index bea69608f..4d7756d71 100644
--- a/app/lib/activitypub/dereferencer.rb
+++ b/app/lib/activitypub/dereferencer.rb
@@ -3,10 +3,10 @@
 class ActivityPub::Dereferencer
   include JsonLdHelper
 
-  def initialize(uri, permitted_origin: nil, signature_account: nil)
+  def initialize(uri, permitted_origin: nil, signature_actor: nil)
     @uri               = uri
     @permitted_origin  = permitted_origin
-    @signature_account = signature_account
+    @signature_actor = signature_actor
   end
 
   def object
@@ -46,7 +46,7 @@ class ActivityPub::Dereferencer
 
     req.add_headers('Accept' => 'application/activity+json, application/ld+json')
     req.add_headers(headers) if headers
-    req.on_behalf_of(@signature_account) if @signature_account
+    req.on_behalf_of(@signature_actor) if @signature_actor
 
     req.perform do |res|
       if res.code == 200
diff --git a/app/lib/activitypub/linked_data_signature.rb b/app/lib/activitypub/linked_data_signature.rb
index e853a970e..f90adaf6c 100644
--- a/app/lib/activitypub/linked_data_signature.rb
+++ b/app/lib/activitypub/linked_data_signature.rb
@@ -9,7 +9,7 @@ class ActivityPub::LinkedDataSignature
     @json = json.with_indifferent_access
   end
 
-  def verify_account!
+  def verify_actor!
     return unless @json['signature'].is_a?(Hash)
 
     type        = @json['signature']['type']
@@ -18,7 +18,7 @@ class ActivityPub::LinkedDataSignature
 
     return unless type == 'RsaSignature2017'
 
-    creator   = ActivityPub::TagManager.instance.uri_to_resource(creator_uri, Account)
+    creator   = ActivityPub::TagManager.instance.uri_to_actor(creator_uri)
     creator ||= ActivityPub::FetchRemoteKeyService.new.call(creator_uri, id: false)
 
     return if creator.nil?
@@ -35,7 +35,7 @@ class ActivityPub::LinkedDataSignature
   def sign!(creator, sign_with: nil)
     options = {
       'type'    => 'RsaSignature2017',
-      'creator' => [ActivityPub::TagManager.instance.uri_for(creator), '#main-key'].join,
+      'creator' => ActivityPub::TagManager.instance.key_uri_for(creator),
       'created' => Time.now.utc.iso8601,
     }
 
diff --git a/app/lib/activitypub/tag_manager.rb b/app/lib/activitypub/tag_manager.rb
index f6b9741fa..3d6b28ef5 100644
--- a/app/lib/activitypub/tag_manager.rb
+++ b/app/lib/activitypub/tag_manager.rb
@@ -44,6 +44,10 @@ class ActivityPub::TagManager
     end
   end
 
+  def key_uri_for(target)
+    [uri_for(target), '#main-key'].join
+  end
+
   def uri_for_username(username)
     account_url(username: username)
   end
@@ -155,6 +159,10 @@ class ActivityPub::TagManager
     path_params[param]
   end
 
+  def uri_to_actor(uri)
+    uri_to_resource(uri, Account)
+  end
+
   def uri_to_resource(uri, klass)
     return if uri.nil?
 
diff --git a/app/lib/request.rb b/app/lib/request.rb
index eac04c798..648aa3085 100644
--- a/app/lib/request.rb
+++ b/app/lib/request.rb
@@ -40,12 +40,11 @@ class Request
     set_digest! if options.key?(:body)
   end
 
-  def on_behalf_of(account, key_id_format = :uri, sign_with: nil)
-    raise ArgumentError, 'account must not be nil' if account.nil?
+  def on_behalf_of(actor, sign_with: nil)
+    raise ArgumentError, 'actor must not be nil' if actor.nil?
 
-    @account       = account
-    @keypair       = sign_with.present? ? OpenSSL::PKey::RSA.new(sign_with) : @account.keypair
-    @key_id_format = key_id_format
+    @actor         = actor
+    @keypair       = sign_with.present? ? OpenSSL::PKey::RSA.new(sign_with) : @actor.keypair
 
     self
   end
@@ -79,7 +78,7 @@ class Request
   end
 
   def headers
-    (@account ? @headers.merge('Signature' => signature) : @headers).without(REQUEST_TARGET)
+    (@actor ? @headers.merge('Signature' => signature) : @headers).without(REQUEST_TARGET)
   end
 
   class << self
@@ -128,12 +127,7 @@ class Request
   end
 
   def key_id
-    case @key_id_format
-    when :acct
-      @account.to_webfinger_s
-    when :uri
-      [ActivityPub::TagManager.instance.uri_for(@account), '#main-key'].join
-    end
+    ActivityPub::TagManager.instance.key_uri_for(@actor)
   end
 
   def http_client
diff --git a/app/serializers/activitypub/public_key_serializer.rb b/app/serializers/activitypub/public_key_serializer.rb
index 62ed49e81..8621517e7 100644
--- a/app/serializers/activitypub/public_key_serializer.rb
+++ b/app/serializers/activitypub/public_key_serializer.rb
@@ -6,7 +6,7 @@ class ActivityPub::PublicKeySerializer < ActivityPub::Serializer
   attributes :id, :owner, :public_key_pem
 
   def id
-    [ActivityPub::TagManager.instance.uri_for(object), '#main-key'].join
+    ActivityPub::TagManager.instance.key_uri_for(object)
   end
 
   def owner
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
diff --git a/app/services/fetch_resource_service.rb b/app/services/fetch_resource_service.rb
index 6c0093cd4..73204e55d 100644
--- a/app/services/fetch_resource_service.rb
+++ b/app/services/fetch_resource_service.rb
@@ -47,7 +47,7 @@ class FetchResourceService < BaseService
       body = response.body_with_limit
       json = body_to_json(body)
 
-      [json['id'], { prefetched_body: body, id: true }] if supported_context?(json) && (equals_or_includes_any?(json['type'], ActivityPub::FetchRemoteAccountService::SUPPORTED_TYPES) || expected_type?(json))
+      [json['id'], { prefetched_body: body, id: true }] if supported_context?(json) && (equals_or_includes_any?(json['type'], ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES) || expected_type?(json))
     elsif !terminal
       link_header = response['Link'] && parse_link_header(response)
 
diff --git a/app/services/keys/claim_service.rb b/app/services/keys/claim_service.rb
index 69568a0d1..ae9e24a24 100644
--- a/app/services/keys/claim_service.rb
+++ b/app/services/keys/claim_service.rb
@@ -72,7 +72,7 @@ class Keys::ClaimService < BaseService
 
   def build_post_request(uri)
     Request.new(:post, uri).tap do |request|
-      request.on_behalf_of(@source_account, :uri)
+      request.on_behalf_of(@source_account)
       request.add_headers(HEADERS)
     end
   end
diff --git a/app/services/resolve_url_service.rb b/app/services/resolve_url_service.rb
index e2c745673..37c856cf8 100644
--- a/app/services/resolve_url_service.rb
+++ b/app/services/resolve_url_service.rb
@@ -20,8 +20,8 @@ class ResolveURLService < BaseService
   private
 
   def process_url
-    if equals_or_includes_any?(type, ActivityPub::FetchRemoteAccountService::SUPPORTED_TYPES)
-      ActivityPub::FetchRemoteAccountService.new.call(resource_url, prefetched_body: body)
+    if equals_or_includes_any?(type, ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES)
+      ActivityPub::FetchRemoteActorService.new.call(resource_url, prefetched_body: body)
     elsif equals_or_includes_any?(type, ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES)
       status = FetchRemoteStatusService.new.call(resource_url, body)
       authorize_with @on_behalf_of, status, :show? unless status.nil?
diff --git a/app/workers/activitypub/delivery_worker.rb b/app/workers/activitypub/delivery_worker.rb
index 788f2cf80..d9153132b 100644
--- a/app/workers/activitypub/delivery_worker.rb
+++ b/app/workers/activitypub/delivery_worker.rb
@@ -37,7 +37,7 @@ class ActivityPub::DeliveryWorker
 
   def build_request(http_client)
     Request.new(:post, @inbox_url, body: @json, http_client: http_client).tap do |request|
-      request.on_behalf_of(@source_account, :uri, sign_with: @options[:sign_with])
+      request.on_behalf_of(@source_account, sign_with: @options[:sign_with])
       request.add_headers(HEADERS)
       request.add_headers({ 'Collection-Synchronization' => synchronization_header }) if ENV['DISABLE_FOLLOWERS_SYNCHRONIZATION'] != 'true' && @options[:synchronize_followers]
     end
diff --git a/app/workers/activitypub/processing_worker.rb b/app/workers/activitypub/processing_worker.rb
index 37e316354..4d06ad079 100644
--- a/app/workers/activitypub/processing_worker.rb
+++ b/app/workers/activitypub/processing_worker.rb
@@ -5,11 +5,15 @@ class ActivityPub::ProcessingWorker
 
   sidekiq_options backtrace: true, retry: 8
 
-  def perform(account_id, body, delivered_to_account_id = nil)
-    account = Account.find_by(id: account_id)
-    return if account.nil?
+  def perform(actor_id, body, delivered_to_account_id = nil, actor_type = 'Account')
+    case actor_type
+    when 'Account'
+      actor = Account.find_by(id: actor_id)
+    end
 
-    ActivityPub::ProcessCollectionService.new.call(body, account, override_timestamps: true, delivered_to_account_id: delivered_to_account_id, delivery: true)
+    return if actor.nil?
+
+    ActivityPub::ProcessCollectionService.new.call(body, actor, override_timestamps: true, delivered_to_account_id: delivered_to_account_id, delivery: true)
   rescue ActiveRecord::RecordInvalid => e
     Rails.logger.debug "Error processing incoming ActivityPub object: #{e}"
   end
diff --git a/spec/controllers/accounts_controller_spec.rb b/spec/controllers/accounts_controller_spec.rb
index 662a89927..12266c800 100644
--- a/spec/controllers/accounts_controller_spec.rb
+++ b/spec/controllers/accounts_controller_spec.rb
@@ -420,7 +420,7 @@ RSpec.describe AccountsController, type: :controller do
         let(:remote_account) { Fabricate(:account, domain: 'example.com') }
 
         before do
-          allow(controller).to receive(:signed_request_account).and_return(remote_account)
+          allow(controller).to receive(:signed_request_actor).and_return(remote_account)
           get :show, params: { username: account.username, format: format }
         end
 
diff --git a/spec/controllers/activitypub/collections_controller_spec.rb b/spec/controllers/activitypub/collections_controller_spec.rb
index 4d87f80ce..f78d9abbf 100644
--- a/spec/controllers/activitypub/collections_controller_spec.rb
+++ b/spec/controllers/activitypub/collections_controller_spec.rb
@@ -24,7 +24,7 @@ RSpec.describe ActivityPub::CollectionsController, type: :controller do
   end
 
   before do
-    allow(controller).to receive(:signed_request_account).and_return(remote_account)
+    allow(controller).to receive(:signed_request_actor).and_return(remote_account)
 
     Fabricate(:status_pin, account: account)
     Fabricate(:status_pin, account: account)
diff --git a/spec/controllers/activitypub/followers_synchronizations_controller_spec.rb b/spec/controllers/activitypub/followers_synchronizations_controller_spec.rb
index e233bd560..c19bb8cae 100644
--- a/spec/controllers/activitypub/followers_synchronizations_controller_spec.rb
+++ b/spec/controllers/activitypub/followers_synchronizations_controller_spec.rb
@@ -15,7 +15,7 @@ RSpec.describe ActivityPub::FollowersSynchronizationsController, type: :controll
   end
 
   before do
-    allow(controller).to receive(:signed_request_account).and_return(remote_account)
+    allow(controller).to receive(:signed_request_actor).and_return(remote_account)
   end
 
   describe 'GET #show' do
diff --git a/spec/controllers/activitypub/inboxes_controller_spec.rb b/spec/controllers/activitypub/inboxes_controller_spec.rb
index 973ad83bb..2f023197b 100644
--- a/spec/controllers/activitypub/inboxes_controller_spec.rb
+++ b/spec/controllers/activitypub/inboxes_controller_spec.rb
@@ -6,7 +6,7 @@ RSpec.describe ActivityPub::InboxesController, type: :controller do
   let(:remote_account) { nil }
 
   before do
-    allow(controller).to receive(:signed_request_account).and_return(remote_account)
+    allow(controller).to receive(:signed_request_actor).and_return(remote_account)
   end
 
   describe 'POST #create' do
diff --git a/spec/controllers/activitypub/outboxes_controller_spec.rb b/spec/controllers/activitypub/outboxes_controller_spec.rb
index 04f036447..74bf46a5e 100644
--- a/spec/controllers/activitypub/outboxes_controller_spec.rb
+++ b/spec/controllers/activitypub/outboxes_controller_spec.rb
@@ -28,7 +28,7 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
   end
 
   before do
-    allow(controller).to receive(:signed_request_account).and_return(remote_account)
+    allow(controller).to receive(:signed_request_actor).and_return(remote_account)
   end
 
   describe 'GET #show' do
diff --git a/spec/controllers/activitypub/replies_controller_spec.rb b/spec/controllers/activitypub/replies_controller_spec.rb
index a35957f24..aee1a8b1a 100644
--- a/spec/controllers/activitypub/replies_controller_spec.rb
+++ b/spec/controllers/activitypub/replies_controller_spec.rb
@@ -168,7 +168,7 @@ RSpec.describe ActivityPub::RepliesController, type: :controller do
 
   before do
     stub_const 'ActivityPub::RepliesController::DESCENDANTS_LIMIT', 5
-    allow(controller).to receive(:signed_request_account).and_return(remote_querier)
+    allow(controller).to receive(:signed_request_actor).and_return(remote_querier)
 
     Fabricate(:status, thread: status, visibility: :public)
     Fabricate(:status, thread: status, visibility: :public)
diff --git a/spec/controllers/concerns/signature_verification_spec.rb b/spec/controllers/concerns/signature_verification_spec.rb
index 05fb1445b..6e73643b4 100644
--- a/spec/controllers/concerns/signature_verification_spec.rb
+++ b/spec/controllers/concerns/signature_verification_spec.rb
@@ -3,6 +3,16 @@
 require 'rails_helper'
 
 describe ApplicationController, type: :controller do
+  class WrappedActor
+    attr_reader :wrapped_account
+
+    def initialize(wrapped_account)
+      @wrapped_account = wrapped_account
+    end
+
+    delegate :uri, :keypair, to: :wrapped_account
+  end
+
   controller do
     include SignatureVerification
 
@@ -73,6 +83,41 @@ describe ApplicationController, type: :controller do
       end
     end
 
+    context 'with a valid actor that is not an Account' do
+      let(:actor) { WrappedActor.new(author) }
+
+      before do
+        get :success
+
+        fake_request = Request.new(:get, request.url)
+        fake_request.on_behalf_of(author)
+
+        request.headers.merge!(fake_request.headers)
+
+        allow(ActivityPub::TagManager.instance).to receive(:uri_to_actor).with(anything) do
+          actor
+        end
+      end
+
+      describe '#signed_request?' do
+        it 'returns true' do
+          expect(controller.signed_request?).to be true
+        end
+      end
+
+      describe '#signed_request_account' do
+        it 'returns nil' do
+          expect(controller.signed_request_account).to be_nil
+        end
+      end
+
+      describe '#signed_request_actor' do
+        it 'returns the expected actor' do
+          expect(controller.signed_request_actor).to eq actor
+        end
+      end
+    end
+
     context 'with request older than a day' do
       before do
         get :success
diff --git a/spec/controllers/statuses_controller_spec.rb b/spec/controllers/statuses_controller_spec.rb
index 05fae67fa..6ed5d4bbb 100644
--- a/spec/controllers/statuses_controller_spec.rb
+++ b/spec/controllers/statuses_controller_spec.rb
@@ -426,7 +426,7 @@ describe StatusesController do
       let(:remote_account) { Fabricate(:account, domain: 'example.com') }
 
       before do
-        allow(controller).to receive(:signed_request_account).and_return(remote_account)
+        allow(controller).to receive(:signed_request_actor).and_return(remote_account)
       end
 
       context 'when account blocks account' do
diff --git a/spec/lib/activitypub/activity/announce_spec.rb b/spec/lib/activitypub/activity/announce_spec.rb
index 41806b258..e9cd6c68c 100644
--- a/spec/lib/activitypub/activity/announce_spec.rb
+++ b/spec/lib/activitypub/activity/announce_spec.rb
@@ -115,7 +115,7 @@ RSpec.describe ActivityPub::Activity::Announce do
 
       let(:object_json) { 'https://example.com/actor/hello-world' }
 
-      subject { described_class.new(json, sender, relayed_through_account: relay_account) }
+      subject { described_class.new(json, sender, relayed_through_actor: relay_account) }
 
       before do
         stub_request(:get, 'https://example.com/actor/hello-world').to_return(body: Oj.dump(unknown_object_json))
diff --git a/spec/lib/activitypub/dereferencer_spec.rb b/spec/lib/activitypub/dereferencer_spec.rb
index ce30513d7..e50b497c7 100644
--- a/spec/lib/activitypub/dereferencer_spec.rb
+++ b/spec/lib/activitypub/dereferencer_spec.rb
@@ -4,10 +4,10 @@ RSpec.describe ActivityPub::Dereferencer do
   describe '#object' do
     let(:object) { { '@context': 'https://www.w3.org/ns/activitystreams', id: 'https://example.com/foo', type: 'Note', content: 'Hoge' } }
     let(:permitted_origin) { 'https://example.com' }
-    let(:signature_account) { nil }
+    let(:signature_actor) { nil }
     let(:uri) { nil }
 
-    subject { described_class.new(uri, permitted_origin: permitted_origin, signature_account: signature_account).object }
+    subject { described_class.new(uri, permitted_origin: permitted_origin, signature_actor: signature_actor).object }
 
     before do
       stub_request(:get, 'https://example.com/foo').to_return(body: Oj.dump(object), headers: { 'Content-Type' => 'application/activity+json' })
@@ -21,7 +21,7 @@ RSpec.describe ActivityPub::Dereferencer do
       end
 
       context 'with signature account' do
-        let(:signature_account) { Fabricate(:account) }
+        let(:signature_actor) { Fabricate(:account) }
 
         it 'makes signed request' do
           subject
@@ -52,7 +52,7 @@ RSpec.describe ActivityPub::Dereferencer do
       end
 
       context 'with signature account' do
-        let(:signature_account) { Fabricate(:account) }
+        let(:signature_actor) { Fabricate(:account) }
 
         it 'makes signed request' do
           subject
diff --git a/spec/lib/activitypub/linked_data_signature_spec.rb b/spec/lib/activitypub/linked_data_signature_spec.rb
index 2222c46fb..d55a7c7fa 100644
--- a/spec/lib/activitypub/linked_data_signature_spec.rb
+++ b/spec/lib/activitypub/linked_data_signature_spec.rb
@@ -20,7 +20,7 @@ RSpec.describe ActivityPub::LinkedDataSignature do
     stub_jsonld_contexts!
   end
 
-  describe '#verify_account!' do
+  describe '#verify_actor!' do
     context 'when signature matches' do
       let(:raw_signature) do
         {
@@ -32,7 +32,7 @@ RSpec.describe ActivityPub::LinkedDataSignature do
       let(:signature) { raw_signature.merge('type' => 'RsaSignature2017', 'signatureValue' => sign(sender, raw_signature, raw_json)) }
 
       it 'returns creator' do
-        expect(subject.verify_account!).to eq sender
+        expect(subject.verify_actor!).to eq sender
       end
     end
 
@@ -40,7 +40,7 @@ RSpec.describe ActivityPub::LinkedDataSignature do
       let(:signature) { nil }
 
       it 'returns nil' do
-        expect(subject.verify_account!).to be_nil
+        expect(subject.verify_actor!).to be_nil
       end
     end
 
@@ -55,7 +55,7 @@ RSpec.describe ActivityPub::LinkedDataSignature do
       let(:signature) { raw_signature.merge('type' => 'RsaSignature2017', 'signatureValue' => 's69F3mfddd99dGjmvjdjjs81e12jn121Gkm1') }
 
       it 'returns nil' do
-        expect(subject.verify_account!).to be_nil
+        expect(subject.verify_actor!).to be_nil
       end
     end
   end
@@ -73,14 +73,14 @@ RSpec.describe ActivityPub::LinkedDataSignature do
     end
 
     it 'can be verified again' do
-      expect(described_class.new(subject).verify_account!).to eq sender
+      expect(described_class.new(subject).verify_actor!).to eq sender
     end
   end
 
-  def sign(from_account, options, document)
+  def sign(from_actor, options, document)
     options_hash   = Digest::SHA256.hexdigest(canonicalize(options.merge('@context' => ActivityPub::LinkedDataSignature::CONTEXT)))
     document_hash  = Digest::SHA256.hexdigest(canonicalize(document))
     to_be_verified = options_hash + document_hash
-    Base64.strict_encode64(from_account.keypair.sign(OpenSSL::Digest.new('SHA256'), to_be_verified))
+    Base64.strict_encode64(from_actor.keypair.sign(OpenSSL::Digest.new('SHA256'), to_be_verified))
   end
 end
diff --git a/spec/services/activitypub/fetch_remote_actor_service_spec.rb b/spec/services/activitypub/fetch_remote_actor_service_spec.rb
new file mode 100644
index 000000000..20117c66d
--- /dev/null
+++ b/spec/services/activitypub/fetch_remote_actor_service_spec.rb
@@ -0,0 +1,180 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::FetchRemoteActorService, type: :service do
+  subject { ActivityPub::FetchRemoteActorService.new }
+
+  let!(:actor) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'https://example.com/alice',
+      type: 'Person',
+      preferredUsername: 'alice',
+      name: 'Alice',
+      summary: 'Foo bar',
+      inbox: 'http://example.com/alice/inbox',
+    }
+  end
+
+  describe '#call' do
+    let(:account) { subject.call('https://example.com/alice', id: true) }
+
+    shared_examples 'sets profile data' do
+      it 'returns an account' do
+        expect(account).to be_an Account
+      end
+
+      it 'sets display name' do
+        expect(account.display_name).to eq 'Alice'
+      end
+
+      it 'sets note' do
+        expect(account.note).to eq 'Foo bar'
+      end
+
+      it 'sets URL' do
+        expect(account.url).to eq 'https://example.com/alice'
+      end
+    end
+
+    context 'when the account does not have a inbox' do
+      let!(:webfinger) { { subject: 'acct:alice@example.com', links: [{ rel: 'self', href: 'https://example.com/alice' }] } }
+
+      before do
+        actor[:inbox] = nil
+
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'returns nil' do
+        expect(account).to be_nil
+      end
+    end
+
+    context 'when URI and WebFinger share the same host' do
+      let!(:webfinger) { { subject: 'acct:alice@example.com', links: [{ rel: 'self', href: 'https://example.com/alice' }] } }
+
+      before do
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'sets username and domain from webfinger' do
+        expect(account.username).to eq 'alice'
+        expect(account.domain).to eq 'example.com'
+      end
+
+      include_examples 'sets profile data'
+    end
+
+    context 'when WebFinger presents different domain than URI' do
+      let!(:webfinger) { { subject: 'acct:alice@iscool.af', links: [{ rel: 'self', href: 'https://example.com/alice' }] } }
+
+      before do
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+        stub_request(:get, 'https://iscool.af/.well-known/webfinger?resource=acct:alice@iscool.af').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'looks up "redirected" webfinger' do
+        account
+        expect(a_request(:get, 'https://iscool.af/.well-known/webfinger?resource=acct:alice@iscool.af')).to have_been_made.once
+      end
+
+      it 'sets username and domain from final webfinger' do
+        expect(account.username).to eq 'alice'
+        expect(account.domain).to eq 'iscool.af'
+      end
+
+      include_examples 'sets profile data'
+    end
+
+    context 'when WebFinger returns a different URI' do
+      let!(:webfinger) { { subject: 'acct:alice@example.com', links: [{ rel: 'self', href: 'https://example.com/bob' }] } }
+
+      before do
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'does not create account' do
+        expect(account).to be_nil
+      end
+    end
+
+    context 'when WebFinger returns a different URI after a redirection' do
+      let!(:webfinger) { { subject: 'acct:alice@iscool.af', links: [{ rel: 'self', href: 'https://example.com/bob' }] } }
+
+      before do
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+        stub_request(:get, 'https://iscool.af/.well-known/webfinger?resource=acct:alice@iscool.af').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'looks up "redirected" webfinger' do
+        account
+        expect(a_request(:get, 'https://iscool.af/.well-known/webfinger?resource=acct:alice@iscool.af')).to have_been_made.once
+      end
+
+      it 'does not create account' do
+        expect(account).to be_nil
+      end
+    end
+
+    context 'with wrong id' do
+      it 'does not create account' do
+        expect(subject.call('https://fake.address/@foo', prefetched_body: Oj.dump(actor))).to be_nil
+      end
+    end
+  end
+end
diff --git a/spec/services/activitypub/process_collection_service_spec.rb b/spec/services/activitypub/process_collection_service_spec.rb
index 3eccaab5b..093a188a2 100644
--- a/spec/services/activitypub/process_collection_service_spec.rb
+++ b/spec/services/activitypub/process_collection_service_spec.rb
@@ -68,7 +68,7 @@ RSpec.describe ActivityPub::ProcessCollectionService, type: :service do
       let(:forwarder) { Fabricate(:account, domain: 'example.com', uri: 'http://example.com/other_account') }
 
       it 'does not process payload if no signature exists' do
-        expect_any_instance_of(ActivityPub::LinkedDataSignature).to receive(:verify_account!).and_return(nil)
+        expect_any_instance_of(ActivityPub::LinkedDataSignature).to receive(:verify_actor!).and_return(nil)
         expect(ActivityPub::Activity).not_to receive(:factory)
 
         subject.call(json, forwarder)
@@ -77,7 +77,7 @@ RSpec.describe ActivityPub::ProcessCollectionService, type: :service do
       it 'processes payload with actor if valid signature exists' do
         payload['signature'] = { 'type' => 'RsaSignature2017' }
 
-        expect_any_instance_of(ActivityPub::LinkedDataSignature).to receive(:verify_account!).and_return(actor)
+        expect_any_instance_of(ActivityPub::LinkedDataSignature).to receive(:verify_actor!).and_return(actor)
         expect(ActivityPub::Activity).to receive(:factory).with(instance_of(Hash), actor, instance_of(Hash))
 
         subject.call(json, forwarder)
@@ -86,7 +86,7 @@ RSpec.describe ActivityPub::ProcessCollectionService, type: :service do
       it 'does not process payload if invalid signature exists' do
         payload['signature'] = { 'type' => 'RsaSignature2017' }
 
-        expect_any_instance_of(ActivityPub::LinkedDataSignature).to receive(:verify_account!).and_return(nil)
+        expect_any_instance_of(ActivityPub::LinkedDataSignature).to receive(:verify_actor!).and_return(nil)
         expect(ActivityPub::Activity).not_to receive(:factory)
 
         subject.call(json, forwarder)
diff --git a/spec/services/fetch_resource_service_spec.rb b/spec/services/fetch_resource_service_spec.rb
index ded05ffbc..c0c96ab69 100644
--- a/spec/services/fetch_resource_service_spec.rb
+++ b/spec/services/fetch_resource_service_spec.rb
@@ -66,7 +66,7 @@ RSpec.describe FetchResourceService, type: :service do
 
       it 'signs request' do
         subject
-        expect(a_request(:get, url).with(headers: { 'Signature' => /keyId="#{Regexp.escape(ActivityPub::TagManager.instance.uri_for(Account.representative) + '#main-key')}"/ })).to have_been_made
+        expect(a_request(:get, url).with(headers: { 'Signature' => /keyId="#{Regexp.escape(ActivityPub::TagManager.instance.key_uri_for(Account.representative))}"/ })).to have_been_made
       end
 
       context 'when content type is application/atom+xml' do