meshbay.git/packages/meshbay-common/src/meshbay_common/adminop.py, branch 0.4

feat(groups): remove a member, and keep gigabytes out of the tab

2026-08-15T15:23:10Z

**Removing a member.** The owner can do it from the Members tab, and it is two halves in the order that fails safe: the node stops serving the group key first (an operator-signed request, so a paired browser only), then the hub drops the membership row. The other order would leave someone able to reach a node that still serves them. It is a membership, not an account. The user row is never written: their other groups, their files and their pinned identity survive, because one group's owner must not be able to erase someone from the hub. It is also per group — a node hosting two loses them from one — and it does not take back the key they already unwrapped, which is what rotating the GEK is for. The confirmation and the panel both say so. **Downloads and streaming through the disk, in both browsers.** The audit this started as found two ways to put gigabytes in a tab. Firefox and Safari have no File System Access API, so every download there was collected in memory. A service worker fixes it: the page keeps the writable half of a transferred stream, the worker answers a made-up URL with the readable half and a Content-Disposition header, and the browser writes it to disk as it arrives, with real backpressure. The worker caches nothing and falls through on every request that is not one of these downloads. A zip announces no Content-Length, since the archive is larger than the files in it and a length we miss truncates the file. Video was worse and affected both browsers. The node pushed ffmpeg's whole output as fast as it was produced while the player consumed a segment at a time, so the queue held the film — and appending all of it hit the SourceBuffer's cap, where the handler logged the error and dropped the segment, leaving a hole in the middle of the film with nothing to show for it. Streaming is credit-based now, 24 segments of 256 KB in flight, verified against the live node: three credits, three segments, then silence until more are granted. The player evicts what is more than a minute behind the playhead and retries a refused segment rather than dropping it. Co-Authored-By: Claude Opus 5

feat(files): download a folder as a zip, and remove an empty one

2026-08-15T10:19:22Z

Two things a Files panel needs and did not have. **Removing a directory** is privileged, where creating one is not: it acts on a name other members are using, on the operator's disk. It is refused unless the directory is empty, and that rule is the safety property — whatever the browser sends, this cannot destroy content. The check runs twice, once before the challenge and once after the signature comes back, because a file can land during the round trip. A file also accepts its uploader's key; a directory has no uploader, so only the operator's key will do. **Downloading a folder** produces a zip built in the browser, written straight to disk as the chunks arrive. An archive of a group folder is routinely tens of gigabytes, so nothing is held: peak memory is one chunk plus a small record per file. The node is not involved at all — it serves the same encrypted chunks as any other download, holds no temporary files, and cannot be asked to compress anything. zipstream.js is store-only. Group content is video and images, already compressed, so deflate would spend CPU on every byte to save nothing, in the thread that is also decrypting. Sizes and CRCs go in a data descriptor after each file because a stream cannot seek back to patch a header, and zip64 kicks in per entry past 4 GiB and for the archive itself. Because none of that can be checked from the Python side of the house, test_zipstream.py runs the real module under Node and reads what it produces with zipfile — CRCs, UTF-8 names, zip64 records and all. The archives also pass `unzip -t`. Firefox and Safari have no File System Access API, so there is nowhere to stream to: the fallback builds the archive in memory and says so, with the size, before starting rather than after failing. One mistake worth recording: the first version of deleteDirectory passed the node's own answer as the value to check the challenge against, which turns the comparison into a tautology. It checks the path we asked for. Co-Authored-By: Claude Opus 5

feat(node)!: the node wraps the group key — closes H3 and M3

2026-08-13T23:27:21Z

The invite flow fetched the invitee's pk_x25519 from the hub and wrapped the GEK for whatever came back (app.js:1466, and gek-init did the same server-side). The hub is the key directory, so a hub answering with its own key was handed the group key by an honest member following the protocol exactly. No forgery, no injection, nothing for the client to notice. That was H3. The fix is not safety numbers. Nobody reads the directory any more: - the node holds the GEK and wraps it itself, on every connection, for the X25519 key the joiner signed with their Ed25519 identity in one transcript (meshbay:join:v1), so the identity key vouches for the encryption key; - identities are bound to accounts by a one-time code the hub never sees — 40 bits, single use, one account, bounded per connection AND node-wide; - the node's own roster decides who may receive the key. Hub membership lets someone reach a node; it no longer gets them anything. A hub that invents an account and mints it a token is answered not_authorized_for_group. Safety numbers would have made substitution detectable by a human who checks, at the moment there is nothing to check against — first contact. Removing the lookup makes it impossible, and costs the user one code to pass along. M3 falls out of the same work. The daemon auto-pinned its own keystore key as admin_pk_ed25519 while the browser signs with the user identity key, so every privileged operation failed closed with a signature error that looked like a bug somewhere else; the demo only worked because a deploy script overwrote the value. Authority now comes from the roster, established locally by `operator pair`. Asking the hub for the operator's key — the obvious-looking fix — would have let the hub install itself as node administrator. BREAKING: gek_bundle_store is deleted, not gated. No member hands the node key material at all, so C5b becomes structural rather than an authorization to check. Existing stored bundles are still served, so current deployments keep working. Also: - join_policy (invite|open) is read from node.toml, never from the hub — a hub able to declare a group open would be handed its key. Unknown group ⇒ invite. - admin signatures are verified against the roster on every check, so unpinning takes effect without a restart. admin_pk_ed25519 stays readable as legacy. - two C5b tests were rewritten, deliberately: they asserted that gek_bundle_store demanded an operator signature, and the message is gone. They now assert the stronger property. The file says not to fix these tests, so this is the record of why they changed. - a slice-1 bug found while writing slice 2: connect() never passed skEdB64, so pairing would have failed at runtime with no test able to catch it. Tests: 152 node+common here, including an end-to-end DataChannel run where a member who has never held the group key redeems a code in the pre-proof window and receives the key wrapped for a key only they can open. Design: docs/invite-pairing-v1.md Co-Authored-By: Claude Opus 5

fix(node): group isolation, upload confinement, GEK seizure, admin challenge

2026-08-13T08:43:16Z

Phase 11.5 — findings H1, C5a, H2, C5b, H5 (see second-review.md). Batched together because the node-side changes share webrtc_server.py and cannot be separated into working commits. H1 — cross-group chat leak. chat_store, the peer registry and the display-name cache were read from the shared transport context, and daemon.py hoisted the FIRST group's chat store onto it. On a node hosting several groups every group's messages went to one database, chat_history served them back to members of every other group, and chat broadcast reached all peers regardless of group. All three now resolve through _group_ctx(). C5a — upload confinement. Uploads landed in the shared root under a client-chosen name and overwrote whatever was there. Any member could destroy the operator's files, and by becoming the recorded uploader of the replaced file could then delete it through the uploader path, bypassing the Ed25519 admin challenge. Uploads now go to a per-user quarantine (.uploads/{user_id}/), refuse to overwrite, and enforce chunk ordering, a filename allowlist and a size cap. H2 — stored XSS in the node admin UI. Filenames chosen by any group member were interpolated raw into the localhost UI, which has no authentication, so script execution there equals control of the node admin API. Now html.escape() throughout, textContent in the audit table, plus CSP/nosniff/no-referrer. The CSP contains exfiltration but cannot stop injected inline script — escaping is the fix. C5b — group key seizure. gek_bundle_store wrote whatever any member sent and auto-activated bundles addressed to the node operator. The operator's X25519 public key is public (the node publishes it in handshake_ack), so any member could wrap a key of their choosing for it and take over the group, locking every legitimate member out. Storing now requires an operator signature and _try_activate_gek is removed: nothing arriving over MNP can set a live GEK. H5 — unbound signing oracle. The node challenged with 32 raw random bytes and the client signed them blind, so a signature named no operation, subject, node or time. New meshbay_common/adminop.py defines a length-prefixed, domain-separated transcript; both sides build it independently and the client refuses to sign when the announced op/subject do not match its request. BREAKING: a group admin who does not operate the node can no longer store GEK bundles on it. Invites must be performed by the node operator. Adds tests/test_security_regressions.py. Verified against pre-fix source via git stash. Three pre-existing tests asserted the vulnerable behaviour as a feature and were inverted: gek auto-activation, and the transport-wide chat_store in test_daemon. Tests: 109 node, 132 hub+common. Co-Authored-By: Claude Opus 5