608c787c52 fixed a bug where messages sent by the email gateway "as"
a user failed to properly attribute ownership of their attachments,
leaving the attachments orphaned and thus with nobody with permissions
to view them.
These orphaned attachments only remain longer than a few weeks if the
`delete_unclaimed_attachments` script has not been run reliably.
Since there is currently no shipped cron job for this, that is most
likely all deployments.
Add a migration to find such orphaned attachments, and re-attach them
to their original message. While theoretically the attachments
could have been later referenced in other messages -- which would be
very difficult to find and determine if they had access to the
attachment -- we only fix the original message.
In order to make this somewhat performant, we assume that the Message
rows associated with an Attachment made by the email gateway happened
within 5 minutes, since they must have been made during one HTTP
request.
This is complicated by the message potentially having been deleted; in
this case, the Attachment is moved into ArchivedAttachment, so it can
relate to the ArchivedMessage. The many-to-many
`zerver_archivedattachment_messages` relationship table cannot use its
own `id` sequence for the value, since the `id` is re-used when the
row is inserted into the `zerver_attachment_messages` table -- we
instead consume a value from the `id` sequence of the
`zerver_attachment_messages` table.
Anders Kaseorg
Alex Vandiver