First slice of in-chat file/photo sharing (dedicated file plane, images
inline + file chips, session-only). This stage adds the wire types and
the pure, unit-tested logic; no transport or UI yet.
- protocol: new FILES_ALPN / FILES_PROTO (peerspeak/files/1) for the
dedicated file-transfer plane. Bump GOSSIP_PROTO 1->2 + sig domain v2
(Chat gained an attachment field, so cross-version peers fail fast
rather than half-work) and Cargo 0.2.0 -> 0.3.0 per VERSIONING.md.
BREAKING wire change: all peers must run >= 0.3.0.
- new src/files.rs: ChatAttachment descriptor (name/size/kind/id; bytes
travel off-gossip), AttachmentKind, plus pure seams — sanitize_filename
(path-traversal/control-char/length-safe), size_within_cap, image
magic-byte sniffing + defensive limited decode (decode-bomb guard),
32-byte request parsing, human_size. 13 unit tests.
- GossipMessage::Chat and RoomEvent::ChatMessage carry an optional
ChatAttachment; send_chat takes Option<ChatAttachment>. Untrusted
inbound descriptors are filename-sanitized + size-validated on ingest.
serde(default) keeps the field forward-compatible at the JSON layer;
+round-trip and pre-v2 back-compat tests.
The attachment id is a random 32-byte handle (rand, already a dep), not
a content hash — the fetch is authenticated + encrypted + member-gated,
so no crypto-hash dep is needed.
349 lib tests pass, clippy clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
