Every upload stores the SHA-256 of its bytes, computed from the
in-memory buffer that is written — never by re-reading disk. Every
download re-hashes the stored object BEFORE the first byte leaves
(memory bounded by the max_file_bytes quota that gated the upload) and
fails closed on mismatch with attachment_integrity_failure; the
mismatch lands in the audit trail as file.integrity_failed with both
hashes. Detection of payload manipulation is the one integrity duty
par. 52 VSA leaves with the application — only it knows what the file
should be.
Pre-#199 rows are hashed by a bounded, idempotent backfill that rides
the existing nightly orphan-file-sweep job (no new scheduler job, job
fence untouched); unreadable files are logged and retried, never
silently skipped, and null-hash rows are served unverified only until
the backfill reaches them. Operator runbook note in security.md
(restore from backup, re-download, audit entry carries both hashes).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0168Ph5uBmHm8X28CSVpbpnJ
