screen: signatures required as the policy a change came under says

Review 3, R1: what a node received was vouched for only while its own
document's policy required signatures. A joiner's first sync, and
every node's message bringing `required`, went in by the rules alone:
a malicious first peer could plant changes under other members' actors
at their next seqs, their real ones then failing as duplicates for
good.

The signatures a message carries are always offered now, and the
screen always has them: a change waits for one where the policy at the
heads it is judged at requires it (rules::Reads::required, read once
per heads), whatever the receiving document holds. Changes written
under a policy not requiring signatures wait for none, as on every
other node; the check for forged changes runs always. Changes waiting
for a signature are judged again whenever signatures come.

The test of signatures required now takes the history into an empty
document; a new one takes changes written under a policy not requiring
them without any.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/state/host.rs b/src/state/host.rs
index 01cbaa2..7b2eb07 100644
--- a/src/state/host.rs
+++ b/src/state/host.rs
@@ -570,7 +570,6 @@ impl Host for AppState {
             tokio::task::spawn_blocking(move || {
                 let result = {
                     let mut replica = state.doc.blocking_write();
-                    let policy = crate::access::policy::of(&replica.doc);
                     // Judged first (`access::screen`), whether this document has a policy
                     // yet or not.
                     let result = {
@@ -582,7 +581,7 @@ impl Host for AppState {
                             epoch_seq,
                             change.raw_bytes(),
                             &state.screening,
-                            policy.required().then_some(&mut replica.signatures),
+                            Some(&mut replica.signatures),
                             &mut crate::document::PatchLog::inactive(),
                         )
                         .map(|_| ())