BlobRecordSet#import_batch preserved blob keys from exported ZIP files
verbatim. A crafted ZIP with a traversal key like "../../config/deploy.yml"
would create a blob whose key resolves to an arbitrary filesystem path
when served by ActiveStorage's DiskService, allowing an attacker to read
local files.
Fix: generate fresh blob keys on import, discarding whatever key was in
the ZIP. This is safe because nothing else in the import pipeline
references blobs by key — attachments use blob_id, ActionText uses GIDs
based on record IDs, and only FileRecordSet used the old key for file
data lookup.
Update FileRecordSet to build an old_key→blob_id mapping from the blob
JSON metadata in the ZIP, then look up blobs by ID instead of by key.
Both check_record and import_batch are now fail-closed: they raise
IntegrityError for unmapped storage files, missing blobs, and duplicate
keys in the export.
Backfill test coverage for BlobRecordSet and FileRecordSet import, and
add a round-trip test verifying blob data survives export/import with
regenerated keys.
Mike Dalessio
71b99c1e18