Fix a security issue that author_signature is not checked on the to-downstream...

Fix a security issue that author_signature is not checked on the to-downstream receive of a federated relayable entity, allowing to forge relayables if you are an owner of the pod where a parent object is stored.

closes #6539

Changelog.md

 # 0.5.6.0
 
 ## Refactor
+* Add more integration tests with the help of the new diaspora-federation gem [#6539](https://github.com/diaspora/diaspora/pull/6539)
 
 ## Bug fixes
 * Fix mention autocomplete when pasting the username [#6510](https://github.com/diaspora/diaspora/pull/6510)
 * Use and update updated\_at for notifications [#6573](https://github.com/diaspora/diaspora/pull/6573)
+* Ensure the author signature is checked when receiving a relayable [#6539](https://github.com/diaspora/diaspora/pull/6539) 
 
 ## Features
 

lib/diaspora/relayable.rb

@@ -69,6 +69,12 @@ module Diaspora
     def receive(user, person=nil)
       comment_or_like = self.class.where(guid: self.guid).first || self
 
+      unless comment_or_like.signature_valid?
+        logger.warn "event=receive status=abort reason='object signature not valid' recipient=#{user.diaspora_handle} "\
+                    "sender=#{parent.author.diaspora_handle} payload_type=#{self.class} parent_id=#{parent.id}"
+        return
+      end
+
       # Check to make sure the signature of the comment or like comes from the person claiming to author it
       unless comment_or_like.parent_author == user.person || comment_or_like.verify_parent_author_signature
         logger.warn "event=receive status=abort reason='object signature not valid' recipient=#{user.diaspora_handle} "\

spec/integration/federation/federation_messages_generation.rb

@@ -117,6 +117,13 @@ def generate_relayable_local_parent_wrong_author_key(entity_name)
   generate_relayable_local_parent(entity_name)
 end
 
+# Checks when a remote pod B wants to send us a relayable with authorship from a remote pod C user
+# without having correct signature from him.
+def generate_relayable_remote_parent_wrong_author_key(entity_name)
+  substitute_wrong_key(@remote_user2, 1)
+  generate_relayable_remote_parent(entity_name)
+end
+
 # Checks when a remote pod C wants to send us a relayable from its user, but bypassing the pod B where
 # remote status came from.
 def generate_relayable_remote_parent_wrong_parent_key(entity_name)

spec/integration/federation/shared_receive_relayable.rb

@@ -21,6 +21,14 @@ shared_examples_for "it deals correctly with a relayable" do
     expect(received_entity.author.diaspora_handle).to eq(@remote_person2.diaspora_handle)
   end
 
+  it "rejects a downstream entity with a malformed author signature" do
+    Workers::ReceiveEncryptedSalmon.new.perform(
+      @user.id,
+      generate_relayable_remote_parent_wrong_author_key(entity_name)
+    )
+    expect(klass.exists?(guid: @entity.guid)).to be(false)
+  end
+
   it "declines downstream receive when sender signed with a wrong key" do
     Workers::ReceiveEncryptedSalmon.new.perform(
       @user.id,