2 Commits

Include renames

Author	SHA1	Message	Date
jaap-jan	5d447da532	Take a rotated vault's contents onto the new key as well ... Rotating a vault re-keyed the vault and not its contents, which was the deal struck last time: everything already stored stayed sealed under the generation it was written with, every remaining member kept the older keys, and the guarantee was narrowed to "nothing written from now on". That left one gap worth closing — somebody who walked off with the old key could still open old ciphertext they later got hold of — and the reason it was safe to defer is the reason it was cheap to add. A vault at mixed generations reads perfectly well, so the pass that moves items across can stop half way and be run again. VaultResealer walks the vault and rewrites each item as an ordinary upsert against the version the server holds. It never decodes the plaintext: an item is opened and the same bytes are sealed again under a fresh data key, so an item written by a newer client crosses a rotation untouched rather than being re-encoded through this build's codec and quietly losing the fields this build has no concept of. It also means nothing in the pass knows what an item is, which is why one loop covers every type including the ones added after it. A conflict is counted and skipped rather than merged — there is nothing to merge, since no content changes — and the next pass picks the item up at the version the other client left. The half that a pass over stored items cannot see is a change queued before the rotation and pushed after it, which would put a brand-new item into the vault under the key the person who just left still holds. So the push path re-seals a stale payload as it dispatches it, writing the revision back to the outbox first so that a retry sends the same bytes rather than a fresh envelope. Between the two, nothing reaches the server under a superseded generation at all. Queued items are therefore deliberately left alone by the pass: rewriting one there would overwrite the user's unpushed work with the version the server holds, which is the one thing a re-keying pass must never do. Removal runs it last, after a sync — a mirror that is behind produces a batch of conflicts instead of a re-sealed vault — and the status line distinguishes the two guarantees, because they are not the same: a vault fully re-sealed is closed to the person who left, and one with items outstanding is closed only to what happens next. Six tests, and three mutations run against them: making the re-seal return the payload unchanged fails five of the six, making the push path skip re-sealing fails the queued-edit test and only that one, and counting conflicts as applied fails the write-elsewhere test. One of the six was wrong before it was right — it modelled a third-party write by re-pushing an existing payload at a bumped version, which no real client would do, and it took reading the AAD to see that the test was lying rather than the code.	2026-08-04 10:18:14 +02:00
jaap-jan	d5b1a73182	Move the keys when a membership changes, not just the flag ... Adding somebody to a team granted them nothing readable and removing them rotated nothing. Both were honest — the interface said so in as many words — and both left the actual work to a button somebody had to remember to press, on a machine that happened to hold the key. Adding now wraps every team vault this machine can open to the new member, and removing revokes their grants and moves each of those vaults to a fresh key that goes to whoever is left. The rotation is where the design had to be decided rather than written. A vault key is per generation and an item carries the generation it was sealed under, so advancing the vault and withdrawing the old grants would make everything already stored unreadable to everybody, including whoever pressed the button. So earlier grants are kept: a member holds one per generation, /me serves them as PriorKeyWraps, and VaultKeyring holds a key per generation — the newest for writing, the item's own for reading, chosen per item on every read path. Sharing issues one grant per generation held, because a recipient handed only the current key would open the vault to find most of it undecryptable; revocation takes every generation, because leaving the history behind leaves them able to read everything written before the rotation. The bump itself is one server transaction. POST /vaults/{id}/rekey must name exactly current + 1 and the vault's xmin token makes that binding, so two admins rotating at once do not both walk away believing they succeeded — the second is refused and told to read the vault again. The server contributes the moment and no cryptography: it cannot generate the key, cannot tell that the one it is handed differs from the old one, and checks that the caller held the old one the only way it can, by requiring a live grant at the current generation. What this does not do is re-encrypt what is already stored, and the product says so rather than the reassuring version: everything written from the rotation onwards is unreadable to the person who left, and nothing about the past changes. That half is deferred and is safe to add incrementally precisely because a vault at mixed generations stays readable. ADR 0010 records the alternatives — revoking the old grants, chaining each key under its successor, re-sealing every item in one request against a server that caps a push at 500 operations — and why each was rejected. Two things fell out of the change rather than being asked for. The grant listing would have shown a member once per generation, so it now returns one row per holder carrying the best key they hold, which is what makes a row below the vault's generation mean "still owed the new key". And MarkUnreadable gives up the write target as well as reporting: a client whose vault was rotated elsewhere would otherwise have gone on sealing items under its superseded key — readable to its author, unreadable to everybody else, with nothing to show for it.	2026-08-03 23:05:40 +02:00