Owner decision on #107 (2026-11-13): enabling AuditLog:HashChain must not
chain the historical backlog. main chained every unchained row oldest-first.
- The first chaining pass on a pristine database (no head, no chained row)
writes a chain-start anchor: AuditLogChainTombstone (cutoff month,
ChainSeq 0), PurgedAtUtc = DB SYSUTCDATETIME(), RowHash =
SHA-256("ScadaBridge.AuditLog.ChainCutoff.v1" || YYYY-MM || ticks).
Written once under the exclusive chain lock, so both centrals agree
whatever their clocks/config. No migration: existing table + grants.
- Only rows with OccurredAtUtc >= cutoff are chained. The anchor hash is
the cutoff month's genesis, binding the cutoff into the chain.
- AuditLog:HashChain:ChainBacklog (default false) restores chain-everything,
read only on the very first enablement. Legacy chains (heads, no anchor)
keep chaining everything.
- verify-chain splits unchained rows into UnchainedRows vs PreCutoffRows
(+ ChainFromUtc); new breaks ChainedBeforeCutoff (row re-dated before the
cutoff, or cutoff moved forward) and CutoffAnchorInvalid (anchor hash /
month / multiplicity). Archive verify uses the anchor from its own
tombstone file or the DB.
- Partition switch-out keeps the anchor (deletes ChainSeq > 0 only); the
head store / export / verify-heads tombstone count excludes it.
- CLI verify-chain table prints Chain from + Pre-cutoff rows.
Tests: AuditLogHashChainCutoffTests (7, MSSQL), 6 verifier unit tests,
service/CLI/management wire tests; 9 mutations all killed.
Claude-Session: https://claude.ai/code/session_01GT67ACmpMR7b9LGRPLijMi
#113: AuditLogPartitionMaintenance (monthly SPLIT RANGE) and the
backfill-source-node endpoint now use the AuditLog:MaintenanceConnectionString
login when set (unset = unchanged). Migration AuditMaintenanceGrants gives
scadabridge_audit_purger ALTER ANY DATASPACE and column-level UPDATE (SourceNode).
#114: archive cleanup deletes the writer's own *.tmp files and manifest-less
data files older than 24 h inside {Directory}/{YYYY} (DeletedOrphan, dry-run aware).
#115: head-export failures bump scadabridge.audit.chain_head_export.failures and
Degrade the /health/ready entry audit-chain-head-export (failing or stale > 2 intervals).
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Item 1 (owner decision: no signing). AuditLog:HashChain:HeadExport (default
off): both centrals periodically read every month's chain head (LastSeq,
LastHash, purge anchor, chained rows, tombstones; one snapshot under the
chain lock SHARED) and append the changed heads to a sink the DB login cannot
write - File (append-only JSONL per node per day, local or UNC) or Syslog
(RFC 5424 over UDP / TCP octet counting). `audit verify-heads --path` reads
those records back (file or syslog-collector lines) and the new
VerifyAuditChainHeads command checks each against the database: Matches /
Extended / Purged, or Mismatch / Regressed / MissingHead / MissingLink /
CountMismatch (exit 3). AuditChainHeadStoreTests forges a chain with the
production hasher: verify-chain says Intact, verify-heads says Mismatch.
Item 3. AuditLog:MaintenanceConnectionString (${secret:}-capable, unset =
today's single login) runs the chain job, chain verify / head export, the
partition switch-out + archive and the per-channel purge on
AuditMaintenanceContext (keyed audit-maintenance repository/archive, purge
actor prefers them). AuditMaintenanceLoginTests runs the hardened setup on
SQL Server: writer (datareader/datawriter/audit_writer) ingests and is
refused chaining and deleting; the chainer+purger login does the full cycle.
Two-login grants documented in Component-AuditLog.md.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty