fix(collab): re-derive content key on collection updates — deliver rotated keys to members (HIGH #173) - #175
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…r rotated keys to members (HIGH #173) A member derived its per-KB content key ONCE, at join/share/enable. On subsequent kbc: collection broadcasts, handle_kbc_membership_broadcast relearned the epoch but never re-derived the content key, so the network task's content_keys (seal + open) was frozen at first derive. Consequences: - 3c rotation was broken for remaining members: after the owner rotated to k', members kept the old k — couldn't open k'-sealed content, sealed their edits under the stale k → divergence after any membership change. - Wrap-on-admit for a member who already joined never reached their seal/open path. - Subsumes #169 M2 (concurrent rotations converge once both deltas merge + re-derive). Fix: - KbCryptoCtx gains kb_collections: per-KB full collection replicas, seeded at join/share/enable, advanced by inbound kbc: deltas. - New refresh_kb_content_key_on_collection_delta: on a kbc: delta, advance the replica and RE-DERIVE content_keys via derive_kb_content_key (+ persist), wired into both inbound sync_update paths. No-op for non-kbc / unseeded / unencrypted (a plain KB is undisturbed). - Rotation handler now registers the find_wrapped winner derived from the post-rotation collection (the #169 M2 single-source-of-truth fix), not the locally-generated k2. Test (principle #14, the rotation-delivery oracle): refresh_kb_content_key_re_derives_on_rotation_remaining_yes_removed_no — a REMAINING member re-derives k' on the rotation delta; the REMOVED member stays stranded on the old k. 116 collab_bridge tests green; clippy clean. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Closes #173. Subsumes #169 M2. Found during the M2 investigation — broader + more severe.
Bug
A member derived its per-KB content key once (join/share/enable). On subsequent
kbc:collection broadcasts,handle_kbc_membership_broadcastrelearned the epoch but never re-derived the content key — the network task'scontent_keys(seal + open) was frozen at first derive. So:k', members kept the oldk: couldn't openk'-sealed content, sealed their edits under stalek→ divergence after any membership change.The data layer was correct (
find_wrapped_content_keyreturnsk'— tested); the gap was collab-bridge wiring.Fix
KbCryptoCtxgainskb_collections— per-KB full collection replicas, seeded at join/share/enable, advanced by inboundkbc:deltas.refresh_kb_content_key_on_collection_delta: on akbc:delta, advance the replica + re-derivecontent_keys(+ persist), wired into both inboundsync_updatepaths. No-op for non-kbc:/ unseeded / unencrypted KBs (a plain KB is undisturbed).find_wrappedwinner derived from the post-rotation collection (the M2 single-source-of-truth fix), not the locally-generatedk2.Test (principle #14 — rotation-delivery oracle)
refresh_kb_content_key_re_derives_on_rotation_remaining_yes_removed_no: a REMAINING member re-derivesk'on the rotation delta; the REMOVED member stays stranded on the oldk. 116 collab_bridge tests + fullcargo test -p maegreen; clippy clean.release:none.🤖 Generated with Claude Code