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Offline and Air-Gap Technical Reference

Source Advisories:

01-Dec-2025 - DSSE‑Signed Offline Scanner Updates
07-Dec-2025 - Reliable Air‑Gap Verification Workflows

Last Updated: 2025-12-14

1. OFFLINE UPDATE BUNDLE STRUCTURE

1.1 Directory Layout

/bundle-2025-12-14/
  manifest.json              # version, created_at, entries[], sha256s
  payload.tar.zst            # actual DB/indices/feeds
  payload.tar.zst.sha256
  statement.dsse.json        # DSSE-wrapped statement over payload hash
  rekor-receipt.json         # Rekor v2 inclusion/verification material

1.2 Manifest Schema

manifest.json:

{
  "version": "string",
  "created_at": "UTC ISO-8601",
  "entries": [{"name": "string", "sha256": "string", "size": int}],
  "payload_sha256": "string"
}

1.3 DSSE Predicate Schema

statement.dsse.json payload:

{
  "payloadType": "application/vnd.in-toto+json",
  "payload": {
    "subject": {
      "name": "stella-ops-offline-kit-<DATE>.tgz",
      "digest": {"sha256": "string"}
    },
    "predicateType": "https://stella-ops.org/attestations/offline-update/1",
    "predicate": {
      "offline_manifest_sha256": "string",
      "feeds": [{"name": "string", "snapshot_date": "UTC ISO-8601", "archive_digest": "string"}],
      "builder": "string",
      "created_at": "UTC ISO-8601",
      "oukit_channel": "edge|stable|fips-profile"
    }
  }
}

1.4 Rekor Receipt Schema

rekor-receipt.json:

{
  "uuid": "string",
  "logIndex": int,
  "rootHash": "string",
  "hashes": ["string"],
  "checkpoint": "string"
}

2. VERIFICATION SEQUENCE

2.1 Offline Kit Import Steps

1. Validate Cosign signature of tarball
2. Validate offline-manifest.json with JWS signature
3. Verify file digests for all entries (including /attestations/*)
4. Verify DSSE:
   - Call StellaOps.Attestor.Verify with:
     - offline-update.dsse.json
     - offline-update.rekor.json
     - local Rekor log snapshot/segment
   - Ensure payload digest matches kit tarball + manifest digests
5. Only after all checks pass:
   - Swap Scanner's feed pointer to new snapshot
   - Emit audit event (kit filename, tarball digest, DSSE digest, Rekor UUID + log index)

2.2 Activation Acceptance Rules

Trust root: pinned publisher public keys (out-of-band rotation)
Monotonicity: only activate if manifest.version > current.version
Atomic switch: unpack → validate → symlink flip (db/staging/ → db/active/)
Quarantine on failure: move to updates/quarantine/ with reason code

3. OFFLINE DIRECTORY LAYOUT

/evidence/
  keys/
    roots/                 # root/intermediate certs, PGP pubkeys
    identities/            # per-vendor public keys
    tlog-root/             # hashed/pinned tlog root(s)
  policy/
    verify-policy.yaml
    lattice-rules.yaml
  sboms/                   # *.cdx.json, *.spdx.json
  attestations/            # *.intoto.jsonl.dsig (DSSE)
  tlog/
    checkpoint.sig         # signed tree head
    entries/               # *.jsonl (Merkle leaves) + proofs
  tools/
    cosign-<ver> (sha256)
    oras-<ver>   (sha256)
    jq-<ver>     (sha256)
    scanner-<ver> (sha256)

4. OFFLINE VERIFICATION POLICY SCHEMA

keys:
  - ./evidence/keys/identities/vendor_A.pub
  - ./evidence/keys/identities/your_authority.pub
tlog:
  mode: "offline"
  checkpoint: "./evidence/tlog/checkpoint.sig"
  entry_pack: "./evidence/tlog/entries"
attestations:
  required:
    - type: slsa-provenance
    - type: cyclonedx-sbom
  optional:
    - type: vex
constraints:
  subjects:
    alg: "sha256"
  certs:
    allowed_issuers:
      - "https://fulcio.offline"
    allow_expired_if_timepinned: true

5. DETERMINISTIC EVIDENCE RECONCILIATION ALGORITHM

1. Index artifacts by immutable digest
2. For each artifact digest:
   - Collect SBOM nodes from canonical SBOM files
   - Collect attestations (provenance, VEX, SLSA, signatures)
   - Validate each attestation (sig + tlog inclusion proof)
3. Normalize all docs (stable sort, strip non-essential timestamps, lowercase URIs)
4. Apply lattice rules (precedence: vendor > maintainer > 3rd-party)
5. Emit `evidence-graph.json` (stable node/edge order) + `evidence-graph.sha256` + DSSE signature

6. OFFLINE FLOW OPERATIONAL STEPS

1. Import bundle (mount WORM media read-only)
2. Verify tools (hash + signature) before execution
3. Verify tlog checkpoint
4. Verify each inclusion proof
5. Verify attestations (keyring + policy)
6. Ingest SBOMs (canonicalize + hash)
7. Reconcile (apply lattice rules → evidence graph)
8. Record run: write `run.manifest` with input/policy/tool/output hashes; DSSE-sign with Authority key

7. SCANNER CONFIG SURFACE

7.1 Offline Kit Configuration

scanner:
  offlineKit:
    requireDsse: true        # fail import if DSSE/Rekor verification fails
    rekorOfflineMode: true   # use local snapshots only
    attestationVerifier: https://attestor.internal
    trustAnchors:
      - anchorId: "UUID"
        purlPattern: "pkg:npm/*"
        allowedKeyids: ["key1", "key2"]

7.2 DSSE/Rekor Failure Handling

DSSE/Rekor fail, Cosign + manifest OK:

Keep old feeds active
Mark import as failed; surface ProblemDetails error via API/UI
Log structured fields: rekorUuid, attestationDigest, offlineKitHash, failureReason

Config flag to soften during rollout:

When requireDsse=false: treat DSSE/Rekor failure as warning; allow import with alerts

8. SBOM INGESTION DETERMINISTIC FLOW

# 1. Normalize SBOMs to canonical form
jq -S . sboms/app.cdx.json > sboms/_canon/app.cdx.json

# 2. Validate schemas (vendored validators)

# 3. Hash-pin canonical files and record in manifest.lock
sha256sum sboms/_canon/*.json > manifest.lock

# 4. Import to DB with idempotent keys: (artifactDigest, sbomHash)

9. OFFLINE REKOR MIRROR VERIFICATION

9.1 File-Ledger Pattern

Keep tlog/checkpoint.sig (signed tree head) + tlog/entries/*.jsonl (leaves + proofs)

9.2 Verification Steps

1. Recompute Merkle root from entries
2. Check matches `checkpoint.sig` (after verifying signature with tlog root key)
3. For each attestation:
   - Verify UUID/digest appears in entry pack
   - Verify inclusion proof resolves

10. METRICS & OBSERVABILITY

10.1 Offline Kit Metrics (Prometheus)

offlinekit_import_total{status="success|failed_dsse|failed_rekor|failed_cosign"}
offlinekit_attestation_verify_latency_seconds (histogram)
attestor_rekor_success_total
attestor_rekor_retry_total
rekor_inclusion_latency

10.2 Structured Logging Fields

rekorUuid
attestationDigest
offlineKitHash
failureReason
kitFilename
tarballDigest
dsseStatementDigest
rekorLogIndex

11. ERROR HANDLING

11.1 Import Failure Modes

Failure Type	Action	Audit Event
Cosign signature invalid	Reject, quarantine	`IMPORT_FAILED_COSIGN`
Manifest signature invalid	Reject, quarantine	`IMPORT_FAILED_MANIFEST`
DSSE verification failed	Reject (if requireDsse=true)	`IMPORT_FAILED_DSSE`
Rekor inclusion failed	Reject (if requireDsse=true)	`IMPORT_FAILED_REKOR`
Digest mismatch	Reject, quarantine	`IMPORT_FAILED_DIGEST`
Version not monotonic	Reject	`IMPORT_FAILED_VERSION`

11.2 Quarantine Structure

/updates/quarantine/<timestamp>-<reason>/
  bundle.tar.zst
  manifest.json
  verification.log
  failure-reason.txt

12. CLI COMMANDS

12.1 Offline Kit Import

stellaops offline import \
  --bundle ./bundle-2025-12-14.tar.zst \
  --verify-dsse \
  --verify-rekor \
  --trust-root /evidence/keys/roots/stella-root.pub

12.2 Offline Kit Status

stellaops offline status
# Output:
# Active kit: bundle-2025-12-14
# Kit digest: sha256:abc123...
# Activated at: 2025-12-14T10:00:00Z
# DSSE verified: true
# Rekor verified: true

12.3 Offline Verification

stellaops verify offline \
  --evidence-dir /evidence \
  --artifact sha256:def456... \
  --policy verify-policy.yaml

13. AUDIT TRAIL

13.1 Audit Event Schema

{
  "eventId": "uuid",
  "eventType": "OFFLINE_KIT_IMPORTED",
  "timestamp": "2025-12-14T10:00:00Z",
  "actor": "system",
  "details": {
    "kitFilename": "bundle-2025-12-14.tar.zst",
    "tarballDigest": "sha256:...",
    "dsseStatementDigest": "sha256:...",
    "rekorUuid": "...",
    "rekorLogIndex": 12345,
    "previousKitVersion": "bundle-2025-12-07",
    "newKitVersion": "bundle-2025-12-14"
  },
  "result": "success"
}

13.2 Audit Log Storage

CREATE TABLE offline_kit_audit (
  event_id UUID PRIMARY KEY,
  event_type TEXT NOT NULL,
  timestamp TIMESTAMPTZ NOT NULL,
  actor TEXT NOT NULL,
  details JSONB NOT NULL,
  result TEXT NOT NULL
);

CREATE INDEX idx_offline_kit_audit_ts ON offline_kit_audit(timestamp DESC);
CREATE INDEX idx_offline_kit_audit_type ON offline_kit_audit(event_type);

14. SECURITY CONSIDERATIONS

14.1 Key Management

Trust roots: pinned via out-of-band distribution
Key rotation: maintain version history in trust store
Revocation: maintain revoked_keys list in trust anchors

14.2 Integrity Guarantees

All bundles content-addressed
Manifest integrity via signature
DSSE envelope integrity via signature
Rekor inclusion proof integrity via Merkle tree

14.3 Air-Gap Boundaries

Allowed:

Local file system reads (read-only mount)
Local tool execution (verified binaries)
Local database writes (staged)

Forbidden:

Network egress
DNS lookups
NTP synchronization (use frozen clock)
External API calls

Document Version: 1.0 Target Platform: .NET 10, PostgreSQL ≥16, Angular v17

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