Gemini audit finding NET-05 ("unbounded collection deserialization before
semantic validation", Low). `LibrarySnapshot::games` and
`CallToPlayAuthorSnapshot::events` were plain `Vec`s. Their semantic
validators reject more than 4,096 elements, but serde had already built
the complete vector by then, so a peer could make a receiver allocate up
to a full 8 MiB response frame's worth of parsed elements before the
limit was applied. The 64 KiB request bound already covers inbound
requests; this closes the same gap for responses a client accepts from a
peer it connected to.
Both fields now deserialize through a bounded visitor that keeps at most
`maximum + 1` elements and drains the remainder as `IgnoredAny` without
allocating. Keeping exactly one element past the limit is deliberate: the
existing `validate` methods still observe `len() > maximum` and report
`TooManyItems`, and `Response::decode` keeps leaving that judgement to
the caller so an invalid Call-to-Play domain does not discard a valid
library (and vice versa). Frames at or below the limit are byte-for-byte
unchanged, and the encoder still refuses to produce oversize frames.
Tests build oversize JSON by hand (the encoder cannot) and check that a
sequence four times the limit decodes to limit + 1 elements, that the
semantic validator then reports `TooManyItems`, and that a sequence
exactly at the limit is untouched. The existing domain-isolation test
asserts the truncated length as well.
Ported from the parallel security branch (lanspread2 commit 5139ec1),
which bundled it with the request frame bound this branch already has.
Test plan:
- `cargo test -p lanspread-proto`: 24 passed.
- `cargo clippy -p lanspread-proto --all-targets -- -D warnings`: clean.
Claude-Session: https://claude.ai/code/session_01QRkCv4a4GqkajyamxmbSuA
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