ZDDC/zddc

zddc-server

A purpose-built HTTPS file server for ZDDC document archives. Designed to replace caddy file-server --browse with features specific to ZDDC workflows.

Features

• High-performance static file serving — ETag, conditional GET, Cache-Control
• ETag on embedded tool HTMLs — sha256 of the embedded bytes; repeat loads return 304 Not Modified instead of re-shipping 50–920 KB
• gzip compression middleware — wraps the entire mux; ~75% size reduction on tool HTMLs and JSON listings (skips bodies under 1 KB)
• Public landing page — root / is reachable by anyone, including anonymous; per-project ACL filtering still hides projects the caller can't reach
• Cascading .zddc ACL — email-based allow/deny lists evaluated bottom-up from requested directory to root
• Caddy-compatible JSON listings — the Archive Browser works without modification
• Virtual .archive index — resolve the earliest revision of any tracked document by URL
• Filesystem watcher — archive index updates automatically when files change
• File-based audit log — JSON-line access log tee'd to <ZDDC_ROOT>/.zddc.d/logs/access-<host>.log by default, rotated by lumberjack (100 MB / 10 backups / 90 days, gzipped)
• Conservative HTTP timeouts — slowloris-resistant; 10 s read-header, 60 s read+write, 120 s idle
• Flexible TLS modes — self-signed, real certificates, or plain HTTP
• Single static binary — CGO-free, no runtime dependencies; cross-compiled to Linux/macOS/Windows

Quick Start

zddc-server ships as a cross-compiled binary distributed via Codeberg release assets.

# Pick a tag from https://codeberg.org/VARASYS/ZDDC/releases (filter by zddc-server-v*)
curl -L -o zddc-server \
  https://codeberg.org/VARASYS/ZDDC/releases/download/zddc-server-vX.Y.Z/zddc-server-linux-amd64
chmod +x zddc-server

# Run against your archive root (HTTPS on :8443 with an in-memory self-signed cert)
ZDDC_ROOT=/srv/archive ./zddc-server

Or build from source (requires Go 1.24+):

git clone https://codeberg.org/VARASYS/ZDDC.git
cd ZDDC/zddc
go build -o zddc-server ./cmd/zddc-server
ZDDC_ROOT=/srv/archive ./zddc-server

For plain HTTP behind a reverse proxy, set ZDDC_TLS_CERT=none and ZDDC_INSECURE_DIRECT=1 — see "TLS" below.

There is no Containerfile / Dockerfile / compose file in this repo. Two ways to run zddc-server in Kubernetes / containers:

• The example Helm charts under helm/ (zddc-server-prod/ for stable / zddc-server-dev/ for tracking main HEAD) compile zddc-server from source via init container — no image registry needed.
• Roll your own image: copy the static binary into a FROM scratch or FROM alpine base in a few lines.

Environment Variables

Variable	Default	Description
ZDDC_ROOT	(required)	Absolute path to the served file tree
ZDDC_ADDR	:8443	Bind address (host:port)
ZDDC_TLS_CERT	(empty)	Path to PEM certificate file. none = plain HTTP (no TLS); empty = generate self-signed
ZDDC_TLS_KEY	(empty)	Path to PEM private key file. Required when ZDDC_TLS_CERT is a file path; ignored otherwise
ZDDC_INSECURE_DIRECT	(empty)	Must be 1 when ZDDC_TLS_CERT=none and the bind address is non-loopback. Acknowledges that an authenticating reverse proxy is in front of zddc-server; without it, plain-HTTP non-loopback startup is refused
ZDDC_INSECURE	(empty)	Must be 1 to allow startup when <ZDDC_ROOT>/.zddc is missing. Without it, the server refuses to start because no .zddc files anywhere → public-by-default access. Set only for deliberately-public deployments
ZDDC_OPA_URL	internal	Policy decider endpoint. internal = built-in Go evaluator (default). http(s)://... or unix:///... = external OPA-compatible server (federal deployments using their own audited Rego). See "External policy decider" below.
ZDDC_OPA_FAIL_OPEN	(empty)	External OPA only. 1 = on transport error, allow the request (availability over correctness). Default = fail closed (deny). Never set to 1 in federal contexts.
ZDDC_OPA_CACHE_TTL	1s	External OPA only. Per-decision cache TTL — bursts of identical queries (a single .archive listing can hit the same (email, dir) tuple many times) collapse to one OPA round-trip. Set 0 to disable. Format is Go's time.ParseDuration (500ms, 2s, 1m).
ZDDC_LOG_LEVEL	info	Log level: debug, info, warn, error
ZDDC_INDEX_PATH	.archive	URL path segment name for the virtual archive index
ZDDC_EMAIL_HEADER	X-Auth-Request-Email	HTTP request header containing the authenticated user's email (the oauth2-proxy / nginx auth-request convention)
ZDDC_CORS_ORIGIN	(empty)	Comma-separated allowlist of origins permitted to make cross-origin requests. Empty (default) disables CORS — appropriate when zddc-server's embedded tools serve same-origin. Set explicitly only if browser-loaded pages from a different origin call back into this server (e.g. https://tools.acme.com for self-hosted tools, or https://zddc.varasys.io for the CDN-bootstrap pattern)
ZDDC_ACCESS_LOG	<ZDDC_ROOT>/.zddc.d/logs/access-<host>.log	Tee'd structured access log. Auto-mkdir on first run. Empty value (set explicitly with --access-log=) disables file logging; stderr stream stays. Per-host filenames let multiple replicas write to the same .zddc.d/ directory without collision; every record carries a host field for downstream aggregation.

ZDDC_TLS_CERT=none disables TLS entirely (plain HTTP). Both cert and key must be set together when using real certificates.

CORS

CORS is disabled by default — ZDDC_CORS_ORIGIN defaults to empty. The embedded-tools install path serves tools and data from the same origin (both come from zddc-server itself), so no cross-origin allowlist is needed and there is no implicit cross-origin trust to a third-party host.

Set the value explicitly only when browser-loaded pages from a different origin need to call back into this server. Two scenarios:

# Self-hosted tools on a separate domain
ZDDC_CORS_ORIGIN=https://tools.acme.com

# CDN-bootstrap pattern (loading tools from the canonical upstream and
# pointing them at your server) — opt in to this trust explicitly
ZDDC_CORS_ORIGIN=https://zddc.varasys.io

Multiple origins are comma-separated. The middleware echoes the matched origin back per-request and sets Access-Control-Allow-Credentials: true so the upstream-set X-Auth-Request-Email header crosses the boundary.

Why empty by default? Earlier releases defaulted this to https://zddc.varasys.io for the CDN-bootstrap convenience, but every deployment then implicitly trusted that origin to make authenticated cross-origin XHRs on behalf of any logged-in user. That's an unusual trust assumption to bake into a default. Now you opt in explicitly when you actually need it.

TLS

Plain HTTP (no TLS)

Set ZDDC_TLS_CERT=none to run without TLS. Recommended when an upstream reverse proxy (nginx, Caddy, Traefik) terminates external TLS and talks to zddc-server over plain HTTP on a private network. zddc-server requires ZDDC_INSECURE_DIRECT=1 for any non-loopback bind in this mode — an explicit acknowledgement that an authenticating proxy sits in front:

ZDDC_ROOT=/srv/archive \
ZDDC_TLS_CERT=none \
ZDDC_ADDR=:8080 \
ZDDC_INSECURE_DIRECT=1 \
  ./zddc-server

When ZDDC_TLS_CERT / ZDDC_TLS_KEY are empty (or when using real certificates), zddc-server generates an ECDSA P-256 self-signed certificate in memory at startup. The certificate changes on every restart — this is intentional and acceptable when an upstream reverse proxy terminates external TLS and uses this server only for encrypted in-datacenter transport.

To use a real certificate (e.g. from Let's Encrypt or an internal CA):

ZDDC_ROOT=/srv/archive \
ZDDC_TLS_CERT=/etc/ssl/zddc/server.crt \
ZDDC_TLS_KEY=/etc/ssl/zddc/server.key \
  ./zddc-server

Authentication

zddc-server does not perform authentication itself. It reads the user's email address from a request header (default: X-Auth-Request-Email) that must be set by an upstream reverse proxy (nginx, Caddy, Traefik, Azure Application Gateway, etc.) after authenticating the user.

If the header is absent, the user is treated as anonymous (empty email). A request is allowed only if (a) no .zddc file exists anywhere in the chain from ZDDC_ROOT to the requested directory (a fresh tree with zero .zddc files defaults to public access — see warning at the top of the next section), or (b) some level in the chain explicitly allows the caller's email. See "Access control: the .zddc cascade" below for the full evaluation order.

Access control: the .zddc cascade

⚠️ zddc-server refuses to start without a root .zddc. A ZDDC_ROOT containing no .zddc files anywhere would default to allow-all (anonymous callers included), so the server fails fast at startup with a clear error. Pass --insecure (or ZDDC_INSECURE=1) to acknowledge a deliberately-public deployment, otherwise drop a starter <ZDDC_ROOT>/.zddc per "Step 1" below.

zddc-server enforces access via cascading .zddc YAML files: drop one in any directory, and its rules apply to that directory and everything beneath it that doesn't override. The model is small enough to hold in your head, but the cascade has one asymmetry that bites operators on first contact — read "When the cascade helps and when it fights you" below before designing a layout.

# Example .zddc file
acl:
  allow:
    - "*@mycompany.com"        # everyone at mycompany.com
    - "contractor@partner.com" # specific external user
  deny:
    - "intern@mycompany.com"   # override: block this specific user

Step 1: starter .zddc

Every install should write a root .zddc before exposing the bind address. The minimum is an admins: line so the admin debug page works (see "Admin Debug Page" below) — adding acl: is optional at this step:

# <ZDDC_ROOT>/.zddc — bare minimum
admins:
  - you@yourcompany.com

With this single file in place, HasAnyFile becomes true for every directory in the tree and the default switches from "allow-all-anonymous" to "deny-anything-not- explicitly-allowed." From here you grant access by adding acl: rules at the levels that need them. (See worked examples below.)

How a request is evaluated

When a request arrives for /A/B/C/, zddc-server reads every .zddc file along the chain from ZDDC_ROOT down to /A/B/C/, then walks bottom-up (deepest level first) looking for a match. The first explicit match wins — either an allow or a deny.

1. At the current level, check deny patterns first. If the email matches any deny → 403 Forbidden, stop walking. (Important: at the same level, deny beats allow — see anti-patterns below.)
2. Same level, check allow patterns. If the email matches → allow, stop walking.
3. No match at this level → walk up to the parent directory's .zddc and repeat.
4. No level matched anywhere in the chain:
   • If no .zddc file existed anywhere in the chain (HasAnyFile=false) → allow (the empty-tree default; see warning above).
   • If at least one .zddc file existed somewhere in the chain (HasAnyFile=true) → 403 Forbidden (default-deny).

The two functions implementing this are AllowedAtLevel (within-level: deny first, then allow) at zddc/internal/zddc/acl.go:10 and AllowedWithChain (deepest-first walk + default-deny rule) at zddc/internal/zddc/acl.go:29. The chain itself is built by EffectivePolicy at zddc/internal/zddc/cascade.go:25.

Glob patterns

* matches any sequence of characters within one side of the @ boundary:

Pattern	Matches
*@mycompany.com	Any user at mycompany.com
alice@*	alice at any domain
*	Any non-empty email
alice@example.com	Exact match only

The * does not cross the @. Implementation at zddc/internal/zddc/acl.go:52.

When the cascade helps and when it fights you

The cascade is well-suited to one shape and clumsy at another. Internalize the asymmetry before designing your layout:

• Adding a new email at a leaf is easy (third parties, occasional contractors). The new email doesn't match any rule at higher levels, so the cascade just grants the leaf-level allow and silently default-denies them everywhere else. No extra deny: rules needed.
• Excluding insiders from a leaf is harder (commercially sensitive subset of an otherwise company-wide tree). If a parent has allow: ["*@company.com"], a leaf-level allow: [alice@company.com] adds alice on top of everyone — it does not subtract everyone-else. Subtracting requires either (a) the two-level gate-and-reallow pattern in the worked example below, or (b) not having the permissive parent rule in the first place.

This shape is intentional: the cascade is designed for delegation (subtree owners can grant access without coordinating with central admin), not for fine-grained subtractive policy. If your model is "everyone has access by default, specific dirs are restricted," push the wildcards downward off the root rather than fighting the cascade.

Pick your layout

Your shape	Recommended pattern
Solo / single-user archive	One .zddc at root with admins: [you], no acl: block — root-only restriction
Single small team, full sharing	Root .zddc with acl: {allow: ["*@team.com"]}. No subdir overrides needed
Multi-tenant: each tenant in own subdir	Empty root .zddc (just admins:), per-tenant <tenant>/.zddc with acl: {allow: [<tenant emails>]}. Tenants don't see each other's listings
Mixed: half open within company, half locked-down to a subset, plus third-party folders	The worked example below — careful: do not put *@company.com at root

Worked example: paired open/closed projects + third-party archive

This is the deployment shape most operators end up with: technical projects are shared company-wide; their commercial siblings are restricted to a subset; a separate /Archive/ tree holds per-vendor folders where each vendor sees only their own subdir. The cascade handles all three with no deny: rules — but only if you keep the *@company.com wildcard off the root.

# <ZDDC_ROOT>/.zddc — admins only, no broad ACL
admins:
  - admin@mycompany.com

# <ZDDC_ROOT>/Acme-tech/.zddc — open employee project (technical)
acl:
  allow: ["*@mycompany.com"]

# <ZDDC_ROOT>/Acme-comm/.zddc — closed sibling (commercially sensitive)
acl:
  allow:
    - alice@mycompany.com
    - bob@mycompany.com

# <ZDDC_ROOT>/Archive/.zddc — employees can browse the vendor list
acl:
  allow: ["*@mycompany.com"]

# <ZDDC_ROOT>/Archive/Acme/.zddc — vendor's only window
acl:
  allow:
    - acme-rep@acme.com

Trace for an insider (alice@mycompany.com) and a vendor (acme-rep@acme.com) hitting representative paths:

Path	alice@mycompany.com	acme-rep@acme.com
/Acme-tech/	✅ matches *@mycompany.com at this level	❌ no match anywhere; HasAnyFile=true → 403
/Acme-comm/	✅ matches alice at this level	❌ default-deny
/<other-closed-project>/	❌ no match anywhere → 403	❌ default-deny
/Archive/	✅ matches *@mycompany.com	❌ no match; default-deny
/Archive/Acme/	✅ falls up to /Archive/.zddc, matches	✅ matches acme-rep@acme.com at this level
/Archive/Acme/Incoming/	✅ inherits from /Archive/.zddc	✅ inherits from /Archive/Acme/.zddc
/Archive/<other-vendor>/	✅ inherits from /Archive/	❌ no match; default-deny
/ (project picker)	Lands; sees the projects she has access to	Lands; project picker filtering hides everything she can't reach

The vendor reaches /Archive/Acme/... only via direct URL (a bookmark or a transmittal email link). Trying to navigate up to /Archive/ returns 403; the archive tool itself treats /Archive/Acme/ as the root of its world (see "Tool-rooted view" in ARCHITECTURE.md § Server security model), so there is no breadcrumb leading anywhere they can't see.

Patterns that look secure but aren't

These are the traps. Each is plausible at first glance and doesn't behave as naive intuition suggests.

1. Same-level allow + deny "*@company.com" does NOT lock the level down to the allow's targets. Deny is checked before allow within a single .zddc, so the allowed user's email matches the deny first and is blocked. To exclude insiders from a leaf, use the two-level gate-and-reallow (parent denies, deeper level re-allows) — or avoid putting *@company.com at any ancestor.

   # /Closed/.zddc — DOES NOT WORK as intended
   acl:
     allow: [alice@company.com]
     deny:  ["*@company.com"]   # blocks alice too — deny is checked first at same level
   

2. A leaf-level allow: [subset] does NOT restrict when a parent has allow: ["*@domain"]. Non-subset users hit the leaf with no match, walk up, match the parent wildcard, and are allowed. Adding a leaf allow is additive, never subtractive. (See the asymmetry section above.)

3. admins: in any .zddc other than the root is silently ignored. The check at zddc/internal/zddc/file.go:17-20 (and IsAdmin) only reads root. This is the only upward-escalation gate; subtree write access never grants admin.

4. An apps: URL override is a full UI mount, not just a tool version pin. Any .zddc writer in a subtree can pin archive: https://attacker.example/... and serve arbitrary HTML to every viewer below that level. Subtree write authority on .zddc should be treated as full UI-mounting authority. The _app/ cache is fetch-once-and-keep — operators clear it by deleting <ZDDC_ROOT>/_app/<host>/<path>. (See "Apps: virtual tool HTMLs" below for the resolver order; SHA-256 pinning is on the federal-readiness list, not currently implemented.)

5. Relying on /Archive/ being unbrowsable to "hide" sibling vendor folders' existence. Sibling-vendor names are hidden because directories the caller can't access are omitted from listings (see "Directory visibility" below) — that's the actual mechanism. Don't rely on the parent dir being denied; rely on the listing filter.

Trust model and invariants

These are the invariants security reviewers should expect to find, stated plainly and tied to the code that enforces them:

• Auth boundary. zddc-server does not authenticate. The user's email is read from the configured request header (default X-Auth-Request-Email) set by an upstream reverse proxy. If the proxy is misconfigured or the bind address is reachable without traversing the proxy, every request is anonymous — and any caller able to set the header can claim any email. Network isolation between the proxy and zddc-server is required (see "Trust boundary" below).
• Subtree authority. Whoever can write a .zddc controls that subtree's ACL — including overriding a parent deny with a leaf allow (test: zddc/internal/zddc/acl_test.go:212 "leaf allows user that parent denies → leaf wins"). This is intentional delegation, not a bug. If you grant write access to /Project-A/.zddc, you've granted full ACL authority over the Project-A subtree.
• Root-only escalation gate. admins: is honored only at <ZDDC_ROOT>/.zddc. Subtree admins: entries are silently ignored (zddc/internal/zddc/file.go:17-20). This is the only upward escalation block; without it, anyone with subtree write authority could promote themselves to admin.

Trust boundary

What zddc-server enforces stops at the network boundary. The deployment must guarantee these for the model above to hold:

1. The bind address must be reachable only via the authenticating proxy. The email-header trust assumes the proxy is the only path to the server. In Kubernetes: a NetworkPolicy restricting ingress to the proxy pod. On a single host: bind to loopback (ZDDC_ADDR=127.0.0.1:8080) and run the proxy on the same host. Without this, anyone reaching the bind address can forge any email by setting X-Auth-Request-Email themselves. zddc-server refuses to start with ZDDC_TLS_CERT=none on a non-loopback bind unless ZDDC_INSECURE_DIRECT=1 is set as an explicit acknowledgement that an authenticating proxy is enforcing this.
2. Anonymous information disclosure on / is by design. The public landing page returns a project picker filtered by ACL — anonymous callers see only projects with no .zddc rules along their chain (in a properly-configured deployment, none). The existence of the server and the names of any ACL-free projects are disclosed without authentication. For deployments where this disclosure is unacceptable, gate / itself behind the proxy's auth-required path; zddc-server's public-landing logic does not need to be disabled, it simply never receives an anonymous request. /.profile is also reachable anonymously by design — same caveat applies.
3. Audit log integrity is filesystem-level, not application-level. The tee'd JSON access log lives at <ZDDC_ROOT>/.zddc.d/logs/access-<host>.log on the served volume. While .-prefixed paths return 404 over HTTP (so the log is not readable through zddc-server), anything with filesystem write authority on the served volume (a sidecar, a backup-restore process, an admin shell) can modify log entries after the fact. For tamper-evident logging, ship the JSON-line file to an external append-only sink (syslog, SIEM) via a sidecar; do not treat the local rotation as the system of record.
4. apps: URL fetches have no integrity check. Fetched once on first miss, cached at <ZDDC_ROOT>/_app/<host>/<path> forever — no SHA-256 pin, no signature. Use only URLs you control, treat the apps cache as a trust boundary, and audit who has .zddc write authority where.

Debugging permissions

When a user reports "I can't see /Project-X/" and you need to figure out why, manual cascade-tracing is the current path:

1. Confirm the resolved email — hit /.admin/whoami as the user (you'll need to have proxy auth working, or run the request through the proxy that signs them in). The page shows every header on the request and the email field zddc-server resolved.
2. List the chain. From <ZDDC_ROOT> down to the requested directory, inspect each .zddc (most directories have none). For /Project-X/sub/sub/, that's /.zddc, /Project-X/.zddc, /Project-X/sub/.zddc, /Project-X/sub/sub/.zddc — read whatever exists.
3. Walk bottom-up. At each level, mentally run AllowedAtLevel: deny patterns first (any match → blocked), then allow (any match → allowed). First explicit match in the bottom-up walk is the answer. Default-deny if HasAnyFile=true and nothing matches.

A built-in /.admin/effective-policy?path=...&email=... endpoint that does this trace and returns the chain + decision is on the future-work list (see below); until it ships, the manual procedure is the only path.

Directory visibility

Directories for which the user lacks access are omitted from JSON listings entirely — they are neither listed nor queryable. A direct request to a denied path returns 403.

This is the mechanism that hides sibling subtrees from a caller. Vendor acme-rep sees an empty-looking /Archive/ (in fact returns 403 since they're not allowed there at all in the worked example), and no other vendor's name leaks via listing.

Reserved hidden segments

Two prefixes are filtered from listings under ZDDC_ROOT:

• .-prefixed (e.g. /.devshell/, /Project-A/.internal/notes.md) — excluded from listings and 404 on direct HTTP access. The recognized virtual prefixes (.archive, .admin) are explicitly permitted through. This lets operators store side-state (caches, dev-shell home dirs, snapshot staging) on the same volume that's served, without exposing it.
• _-prefixed (e.g. /_template/) — excluded from listings only. Direct URL access still works. Use this for operator-managed scaffolding the user shouldn't browse to but might link to (e.g. a _template/ directory of stub-HTML examples to copy into project subdirs).

How to verify in 5 minutes

This recipe stands up the worked-example layout in a tmpdir, hits each (email, path) cell with curl, and asserts the documented behavior. Run it on your own deployment to confirm the cascade is doing what you think:

ROOT=$(mktemp -d)
mkdir -p "$ROOT/Acme-tech" "$ROOT/Acme-comm" "$ROOT/Archive/Acme"

cat > "$ROOT/.zddc" <<'YAML'
admins: [admin@mycompany.com]
YAML
cat > "$ROOT/Acme-tech/.zddc" <<'YAML'
acl: {allow: ["*@mycompany.com"]}
YAML
cat > "$ROOT/Acme-comm/.zddc" <<'YAML'
acl: {allow: [alice@mycompany.com]}
YAML
cat > "$ROOT/Archive/.zddc" <<'YAML'
acl: {allow: ["*@mycompany.com"]}
YAML
cat > "$ROOT/Archive/Acme/.zddc" <<'YAML'
acl: {allow: [acme-rep@acme.com]}
YAML

# Plain HTTP on loopback so curl doesn't need TLS
ZDDC_ROOT="$ROOT" ZDDC_TLS_CERT=none ZDDC_ADDR=127.0.0.1:8090 \
  ./zddc-server &
SERVER_PID=$!
sleep 1

probe() { # email path expected_status
    got=$(curl -s -o /dev/null -w '%{http_code}' \
        -H "X-Auth-Request-Email: $1" \
        "http://127.0.0.1:8090$2")
    printf '%-40s %-30s expected=%s got=%s %s\n' \
        "$1" "$2" "$3" "$got" \
        "$([ "$got" = "$3" ] && echo OK || echo FAIL)"
}

# Insider — alice should see all the technical + her closed project + Archive tree
probe alice@mycompany.com   /Acme-tech/         200
probe alice@mycompany.com   /Acme-comm/         200
probe alice@mycompany.com   /Archive/           200
probe alice@mycompany.com   /Archive/Acme/      200

# Insider not on the closed project — bob should hit the technical and Archive,
# NOT the closed sibling
probe bob@mycompany.com     /Acme-tech/         200
probe bob@mycompany.com     /Acme-comm/         403
probe bob@mycompany.com     /Archive/           200
probe bob@mycompany.com     /Archive/Acme/      200

# Vendor — acme-rep should ONLY see /Archive/Acme/, blocked everywhere else
probe acme-rep@acme.com     /Acme-tech/         403
probe acme-rep@acme.com     /Acme-comm/         403
probe acme-rep@acme.com     /Archive/           403
probe acme-rep@acme.com     /Archive/Acme/      200

# Anonymous — root .zddc exists, so HasAnyFile=true → default-deny everywhere
# (the root / itself is the public-landing exception; subdirs are gated)
probe ''                    /Acme-tech/         403
probe ''                    /Archive/Acme/      403

# Anti-pattern: same-level allow + deny *@company.com does NOT lock alice in
mkdir -p "$ROOT/Trap"
cat > "$ROOT/Trap/.zddc" <<'YAML'
acl:
  allow: [alice@mycompany.com]
  deny:  ["*@mycompany.com"]   # deny is checked first → blocks alice too
YAML
probe alice@mycompany.com   /Trap/              403  # the trap docs warn about

kill $SERVER_PID

Every line should print OK. If any prints FAIL, the cascade isn't behaving as documented — file an issue with the failing line. After every .zddc change in production, retest at minimum as the editing user (to confirm you haven't locked yourself out).

Federal-readiness gap analysis

The current model is well-suited for commercial-tenant ACL with delegated authentication. To clear federal hurdles (FedRAMP Moderate, NIST 800-53 Rev. 5 baseline, FIPS 140-3, DoD STIG), these gaps would need to be closed. None are implemented today — this list is informational so security reviewers don't have to redo the gap analysis from scratch.

• FIPS 140-3 cryptography (NIST SC-13) — current build uses Go stdlib crypto. Required: build with GOEXPERIMENT=systemcrypto + RHEL FIPS userspace, or use the microsoft/go (formerly goboring) toolchain.
• TLS hardening (NIST SC-8(1)) — server uses Go stdlib tls.Config defaults; no explicit MinVersion, CipherSuites, or curve list. Required: explicit MinVersion: tls.VersionTLS12 (TLS 1.3 preferred), DoD-approved cipher allowlist, OCSP stapling, HSTS header.
• Authenticated proxy↔server channel (NIST IA-3) — current trust is network-level isolation only. Required: mTLS or signed forwarding token (e.g. JWT signed by the proxy with a key zddc-server validates).
• Multi-factor authentication (NIST IA-2(1)) — delegated to upstream proxy. Required: documented reference deployment with PIV/CAC via oauth2-proxy or equivalent.
• Role-based access control (NIST AC-3(7)) — current model is per-email allow/deny + a single root-admin role. Required: roles as first-class entities, .zddc syntax for role grants, identity-source-driven role assignment.
• Least-privilege bounding (NIST AC-6) — leaf-allow-overrides-parent-deny is incompatible with default federal expectations. Required: a configurable enforcement mode where parent denies are absolute and only root admins can override.
• Account lifecycle (NIST AC-2) — emails as identifiers must tie to authoritative sources (PIV cert subject, IdP-managed identity). Required: documented integration with at least one IdP supporting federal identity attestation.
• Audit log integrity & retention (NIST AU-9, AU-11) — current 90-day local rotation is a starting point. Required: tamper-evident logs (signed log chain or external append-only sink) with 1-year minimum online and 3-year archive.
• Continuous monitoring hooks (NIST CA-7) — automated alerting on .zddc changes, admin endpoint use, repeated 403s from one identity. Required: structured event emission to syslog/SIEM beyond the local file.
• Supply-chain integrity (NIST SI-7) — vendored libs (jszip, docx-preview, xlsx) need SBOM, CVE tracking, automated update pipeline. apps: URL fetches need SHA-256 pinning and signature verification.
• Data-at-rest encryption (NIST SC-28) — delegated to the deployment platform. Required: documented baseline (cloud KMS, LUKS, dm-crypt) with key-rotation procedures.
• Vulnerability disclosure process (NIST SI-5) — repo lacks SECURITY.md. Required: documented disclosure procedure, embargoed-fix workflow, CVE-assignment policy.

A full SSP / control-by-control mapping consumes this list as input; it is not a substitute for one.

External policy decider (OPA-compatible)

For deployments that need policy decisions made by an external, independently-audited engine — typically federal customers using Open Policy Agent — zddc-server can delegate every access decision to an HTTP/Unix-socket endpoint that speaks OPA's /v1/data/... JSON wire protocol.

Set one of:

ZDDC_OPA_URL=internal                       # built-in Go evaluator (default)
ZDDC_OPA_URL=http://127.0.0.1:8181          # OPA via HTTP
ZDDC_OPA_URL=https://opa.internal:8181      # OPA via HTTPS
ZDDC_OPA_URL=unix:///run/opa/opa.sock       # OPA via Unix socket

Internal mode uses zddc-server's in-process evaluator — same Go code that backs the cascade rules above, no network round-trip, no external dependency. This is the default.

External mode POSTs each access decision to <ZDDC_OPA_URL>/v1/data/zddc/access/allow with body:

{
  "input": {
    "user": {"email": "alice@mycompany.com"},
    "path": "/Project-A/sub/",
    "policy_chain": {
      "levels": [
        {"acl": {}, "admins": ["admin@mycompany.com"]},
        {"acl": {"allow": ["*@mycompany.com"]}}
      ],
      "has_any_file": true
    }
  }
}

OPA evaluates the deployment's Rego policy against this input and returns:

{"result": true}

Rego policy authors can implement either:

• Same semantics as our internal evaluator — walk input.policy_chain.levels bottom-up, deny-first within a level, default-deny when input.policy_chain.has_any_file is true. The .zddc files in the served tree continue to drive policy unchanged.
• Federal-mode tightening — same chain, but parent denies are absolute (no leaf-allow override of an ancestor's deny). NIST AC-6 least-privilege posture.
• RBAC-from-IdP — read additional fields from input.user (e.g. roles populated by the upstream proxy from SAML/OIDC claims) and decide based on those, treating .zddc as a file-tree map of required-roles instead of explicit emails.
• Anything else — Rego is general-purpose policy; once you're running real OPA, the constraints are whatever you write.

OPA failure modes

External mode adds a network call to the request hot path. zddc-server treats unreachable / non-2xx / malformed-response cases as deny (fail-closed) by default, with a WARN log. Operators who prefer availability over correctness — typically not federal — can flip this:

ZDDC_OPA_FAIL_OPEN=1                        # allow on transport error

Always-WARN logging means a healthy run is silent and a sick OPA is loud regardless of which mode you pick.

OPA decision cache

External OPA mode wraps the HTTP/socket client in a small per-decision cache (default 1 s TTL). A single .archive listing or directory enumeration walks the cascade for every entry, which would otherwise issue one OPA round-trip per entry; the cache collapses identical (email, decision-input) tuples down to one call per TTL window.

The 1-second default is short enough that a .zddc edit is reflected in the next listing (it's the same window as the fsnotify watcher's debounce). Operators who want zero staleness — or who are running their own caching layer in front of OPA — can disable:

ZDDC_OPA_CACHE_TTL=0                        # no caching, every request → OPA
ZDDC_OPA_CACHE_TTL=5s                       # longer window for batchy workloads

The cache is per-process, in-memory, and capped at ~4096 entries with opportunistic eviction of expired entries. Internal mode (the default) gets no cache — the in-process Go evaluator is already cheaper than a cache lookup would be.

Reference Rego policy

The --print-rego flag emits the bundled reference Rego policy that mirrors internal-mode semantics exactly. Federal customers standing up their own OPA instance can use it as a starting point:

zddc-server --print-rego > /etc/opa/policies/zddc-access.rego

Parity is enforced at build time. zddc/internal/policy/parity_test.go imports the OPA Go module as a test-only dependency, evaluates the bundled Rego against the same fixture set the internal Go evaluator runs, and fails CI on any divergence. The test-only import means the production binary stays OPA-free (still 13 MB) — the OPA library is in go.mod but not in go build's output.

This gives you both ends of the spectrum: a single OPA-aware codebase where the production decider is pure Go (no library bloat, no extra process), the wire format is OPA-canonical (just point an external OPA at it and decisions delegate seamlessly), and the bundled reference Rego is a parity-tested artifact you can ship alongside or extend.

Typical federal customizations on top of the bundled Rego:

• Parent-deny-is-absolute — flip the leaf-allow-overrides-parent-deny rule for NIST AC-6 least-privilege posture.
• Role-based access — read additional input fields like input.user.roles populated by the upstream proxy from SAML/OIDC claims, and decide based on those instead of (or alongside) email.
• Time-of-day or IP-range constraints — Rego can read input.context.now and request metadata for context-aware decisions.
• SIEM-shipped decision logs — OPA's logging plugins emit every decision in a structured format ready for Splunk Government, Elastic Federal, etc.

Reference deployment shapes

Commercial / default: nothing to set. ZDDC_OPA_URL=internal is the implicit default; the in-process evaluator handles every decision. No sidecar, no extra port, no extra binary.

Federal sidecar: deploy OPA alongside zddc-server (k8s sidecar, nomad task, or systemd service on the same host), bind it to 127.0.0.1:8181 (or a Unix socket), point ZDDC_OPA_URL at it. OPA loads the deployment's bundled Rego policy from a configured source (filesystem, signed bundle from S3, OPAL, etc.) and is patched independently of zddc-server.

Per-tenant policy variants: run multiple OPA instances each loaded with a different bundle, point each zddc-server replica at the appropriate one. The .zddc files in the served tree stay the same; the interpretation of those files differs per tenant.

Future work

Items the conversation flagged as friction in operator setup or as documented gaps that warrant code, in addition to the federal-readiness items above:

• /.admin/effective-policy?path=...&email=... endpoint returning the resolved chain + decision, so debugging permissions stops requiring manual cascade tracing.
• .zddc.form.yaml ACL editor (built on the form-data system) once file-as-truth round-trip preserves comments — turn the manual YAML edit into a self-service UI for project owners.
• Save-time validation that warns when a .zddc change would lock the editing user out (or have a measurable effect they didn't anticipate).
• zddc-server policy export command emitting every .zddc file's resolved effect, suitable for change-control review (and a prerequisite for the CM-3 federal control above).
• Per-decision caching for external OPA mode (small TTL on (email, path) to amortize the .archive listing's per-entry round-trip).
• A reference Rego bundle shipped alongside the binary that exactly reproduces internal mode, plus a "federal-mode" variant that flips the parent-deny-is-absolute toggle. Useful as a starting point for customers who want to extend rather than write from scratch.

Admin Debug Page

zddc-server exposes a built-in debug page at /.admin/ for operators who can push code/images but cannot kubectl exec into the running container. It surfaces:

• /.admin/whoami — every header on the current request, the configured email header name, the value observed at that name, and the resolved email. This is the first thing to look at when access logs show email=anonymous — it tells you exactly which (if any) header the upstream proxy is sending.
• /.admin/config — the resolved Config (env vars). Equivalent to kubectl exec -- env | grep ^ZDDC_ for diagnosing chart / deployment overrides.
• /.admin/logs — recent log entries (last 500) from an in-memory ring buffer. Optional ?level=info|warn|error|debug and ?since=<RFC3339> query params. At ZDDC_LOG_LEVEL=debug every request also logs its full header map under msg=request headers — useful for diagnosing proxy / SSO header passthrough (e.g. confirming which header carries the email). Note: that dump includes auth tokens and cookies; only enable debug in trusted environments.
• /.admin/ — HTML dashboard that fetches the three JSON endpoints client-side.

Authorization

Authorization is via an admins: list in the root .zddc file (<ZDDC_ROOT>/.zddc). Patterns use the same glob syntax as acl.allow / acl.deny:

admins:
  - alice@mycompany.com
  - "*@admin.mycompany.com"
acl:
  allow:
    - "*@mycompany.com"

The root-only invariant (subdirectory admins: entries are silently ignored, so subtree write authority cannot be self-promoted to admin) is documented under "Trust model and invariants" in the access-control section above — that's the canonical home; this section just shows the syntax.

If the root .zddc has no admins list (or no .zddc exists), every admin endpoint returns 404 to every caller. Non-admin requests also receive 404 (not 403) so the existence of the admin page is invisible to unauthorized callers.

Forward-auth target for upstream proxies

zddc-server also exposes GET /.auth/admin — a machine-only endpoint that returns 200 if the caller's resolved email is in the root .zddc admins: list, 403 otherwise. No body, no redirect, no UI; it is a pure authorization decision intended to be polled by an upstream proxy's forward-auth directive (Caddy forward_auth, nginx auth_request, Traefik ForwardAuth, etc.).

The intended use case is gating adjacent services on the same pod / host that don't have their own ACL. Concretely: the dev-shell deployment runs both zddc-server and code-server behind one Caddy listener; Caddy uses forward_auth to ask /.auth/admin whether the caller is allowed to reach /devshell/* (the IDE) before forwarding. zddc-server's own routes (/, /<project>/, /.archive/, etc.) keep their existing .zddc-cascade ACL and don't go through this endpoint.

# example: protect /devshell/* with forward_auth on /.auth/admin
handle_path /devshell/* {
    forward_auth 127.0.0.1:9090 {
        uri /.auth/admin
        copy_headers X-Auth-Request-Email
    }
    reverse_proxy 127.0.0.1:8443  # code-server
}

The check is cheap (one map lookup against the cached PolicyChain); calling it on every request is fine. Edits to /srv/.zddc propagate within the fsnotify watcher's debounce window (~2 s) — no service restart needed.

Caveats

• Logs are in-memory and lost on restart. The buffer holds the most recent 500 records; for long-term audit, parse the stderr stream the way you already do.
• The page reads only configuration and request state — it does not modify anything.
• An interactive terminal is not yet available; that's planned as a follow-up behind a separate ZDDC_ADMIN_TERM=1 env-var gate so it stays opt-in.

Apps: virtual tool HTMLs

zddc-server virtually serves the five tool HTMLs (archive, transmittal, classifier, mdedit, landing) at the appropriate paths. The current-stable build of each tool is baked into the binary at compile time via //go:embed; that's the default. No fetch happens out of the box.

Where each tool is served

App	Available at
archive	every directory (multi-project, project, archive, vendor)
classifier	any Incoming, Working, or Staging directory and its subtree
mdedit	any Working directory and its subtree
transmittal	any Staging directory and its subtree
landing	only at the deployment root (the project picker)

Outside these locations, the corresponding <app>.html URL returns 404.

Override and version-pin

For any path, the resolution order is:

1. Real file at the path — operator drops archive.html (or any other) into a directory; the static handler serves it. Beats everything below.
2. Closer-to-leaf .zddc apps: entry — walks .zddc files leaf→root for an apps.<app> entry. The first match wins. Spec is one of:
   • stable / beta / alpha (canonical upstream channel)
   • v0.0.4 / v0.0 / v0 (canonical upstream version pin)
   • https://... (full URL to a custom mirror)
   • ./local.html / /abs/path.html (local file)
3. Embedded — the build-time HTML compiled into the binary.

URL sources are fetched once on first request and cached forever in <ZDDC_ROOT>/_app/<host>/<path>. There is no background refresh and no hash verification — to pull a new build, delete the cache file. Concurrent misses for the same URL share one outbound fetch (singleflight). Direct URL access to /_app/... is blocked at dispatch; cached HTMLs are served only via the apps resolver.

If a configured URL fetch fails (network down, 5xx), the server falls back to the embedded copy and emits a one-time WARN log per source. The X-ZDDC-Source response header always reports what was served: fetch:URL, cache:URL, path:/abs, or embedded:<app>@<build>.

Example

# <ZDDC_ROOT>/Project-A/.zddc
apps:
  classifier: alpha                                                # track alpha for this project
  archive: https://my-mirror.internal/zddc/archive_v0.0.4.html     # custom mirror, pinned
  mdedit: ./our-mdedit.html                                        # local fork

Env vars

Variable	Default	Purpose
ZDDC_BUILD_VERSION	dev	String stamped into X-ZDDC-Source: embedded:<app>@<v>

The landing page fetches GET / (with Accept: application/json) to retrieve the list of top-level project directories the requesting user has access to. It renders checkboxes for each project and opens archive.html?projects=Proj-A,Proj-B when the user clicks "Open Archive".

Presets (named project selections) are stored in the browser's localStorage — no server-side state required.

Shared URLs: the ?projects= parameter is preserved in the archive browser URL so users can email direct links to a pre-filtered view. If the recipient does not have access to a project listed in the URL, a warning banner is shown.

Caching and ETags

zddc-server uses content-hash ETags wherever a re-fetch of identical content is plausible — directory listings, the project list, the embedded HTML tools.

Endpoint	ETag source	Notes
GET / (project list, Accept: application/json)	SHA-256 prefix of the response body	Refetched on every request; the JSON is rebuilt from current FS state. The hash is the actual response, so 304s are always trustworthy regardless of filesystem-watcher reliability.
GET /<dir>/ (directory listing, Accept: application/json)	SHA-256 prefix of the response body	Same.
GET /<dir>/ (HTML browse)	Hash of the embedded browse.html template	Computed once at startup, memoized. Changes only on binary redeploy.
GET /<app>.html (embedded tools)	Hash of the embedded bytes	Same — memoized at startup.

Why content-hash and not server-side caching? The cascade walks .zddc files on every directory access; an os.ReadDir runs to build the listing; the ACL filter applies. A cache keyed on directory mtime would save that server work but depends on reliable filesystem watching — and Azure Files SMB mounts (a common deployment substrate) do not support inotify/fsnotify reliably. Content-hash ETags deliver only the bandwidth savings, not the server-work savings, but they cannot lie about staleness regardless of watcher behavior. A future enhancement could add an mtime-keyed cache for environments with reliable watchers, behind a feature flag.

The response headers are:

Cache-Control: private, max-age=0, must-revalidate
ETag: "<16-hex-char hash>"

must-revalidate ensures every refresh round-trips the server (which re-runs the cascade and ACL filter); max-age=0 means no client-side freshness window; private prevents intermediary caches from sharing responses across users (each user has their own ACL-filtered view).

Access Logging

Every HTTP request is logged as a structured slog entry at INFO level:

Field	Description
ts	Request arrival timestamp (RFC3339)
email	User email from the configured header, or anonymous
method	HTTP method
path	URL path
status	HTTP response status code
bytes	Response body bytes written
duration_ms	Request duration in milliseconds

Log output goes to stderr. Use ZDDC_LOG_LEVEL=warn to suppress access logs if needed, or pipe stderr to a log aggregator.

Virtual Archive Index (.archive)

Any URL path segment named .archive (configurable via ZDDC_INDEX_PATH) is intercepted by the server and treated as a virtual document index.

The index is built at startup by scanning all transmittal folders under ZDDC_ROOT. It maps each (project, trackingNumber, revision, modifier) tuple to the file from the chronologically earliest transmittal folder within that project that contains it.

Project scoping

The .archive index is scoped to the project — i.e. the first slash-separated segment of the request's .archive context path. The same tracking number issued under two different projects does NOT collide; each project's .archive/ surfaces only that project's documents.

A request to /.archive/... at the very root has no project segment to scope by and returns 404 Not Found. Stable references must always be project-rooted (e.g. /ProjectA/.archive/TRK-001.html).

Within one project, two different files claiming to be the same (tracking, rev) are an authoring mistake. The chronological winner still wins, but a WARN log is emitted with both paths so the conflict can be diagnosed and corrected.

URL patterns

URL	Resolves to
GET /Project/.archive/TRK-001.html	Latest base revision of TRK-001 within Project
GET /Project/.archive/TRK-001_A.html	Base revision A of TRK-001 within Project
GET /Project/.archive/TRK-001_A+C1.html	Modifier C1 of revision A of TRK-001 within Project
GET /Project/.archive/	JSON listing of Project's resolvable entries
GET /Project/sub/sub/.archive/TRK-001.html	Same as the top-level Project listing — depth within a project doesn't change scope
GET /.archive/...	404 — root has no project segment

All successful responses are 302 Found redirects to the actual file URL. ACL is enforced on both the .archive context directory and the resolved target file.

Why "earliest" transmittal?

Within one project, any file claiming to be TRK-001_A (IFC) should be identical across transmittals (same content, same SHA-256). If the same tracking number and revision appears in multiple transmittals, the first one received chronologically is treated as the authoritative copy. A later arrival with a different file path is an error condition; the server logs a WARN with both paths but does not change the winner.

Index refresh

The index refreshes automatically via an fsnotify filesystem watcher. Changes are debounced by 2 seconds before the relevant transmittal folder is re-indexed.

Note for Azure Files: Azure SMB mounts do not support inotify/fsnotify reliably. The watcher will log a warning and the index will only be updated by restarting the server.

ZDDC Filename Convention

The server parses filenames following the ZDDC convention:

trackingNumber_revision (status) - title.extension

Part	Format	Example
trackingNumber	No spaces or underscores	123456-EL-SPC-2623
revision	~?[A-Z0-9]+(\+[CBNQ][0-9]+)?	A, ~B, C+C1
status	One of the valid status codes	IFC, REC, ---
title	Free text	Electrical Specification

Valid status codes: IFA IFB IFC IFD IFI IFP IFR IFU REC RSA RSB RSC RSD RSI ---

Transmittal folder format: YYYY-MM-DD_trackingNumber (STATUS) - title

Integration with Archive Browser

The Archive Browser (archive.html) can connect to zddc-server in HTTP mode. The server returns JSON directory listings in exactly the same format as Caddy's file-server --browse — no changes to archive/js/source.js are needed.

To use: install archive.html at ZDDC_ROOT/archive.html (or any subdirectory) — either the actual built tool downloaded by the self-contained install snippet, or one of the six-line stubs from the project-subdir / track-upstream snippets that fetches it. Then open it via the zddc-server URL; the app will auto-connect and scan the directory tree.

Distribution

Each stable release is a Codeberg git tag (zddc-server-vX.Y.Z) with four pre-built binaries attached as release assets:

File	Platform
zddc-server-linux-amd64	Linux (x86-64)
zddc-server-darwin-amd64	macOS (Intel)
zddc-server-darwin-arm64	macOS (Apple Silicon)
zddc-server-windows-amd64.exe	Windows (x86-64)

All binaries are statically linked (CGO disabled), built with -trimpath -ldflags="-s -w -X main.version=<ver>". No runtime dependencies.

Download URLs from Codeberg directly:

https://codeberg.org/VARASYS/ZDDC/releases/download/zddc-server-vX.Y.Z/zddc-server-linux-amd64

Browse all releases at https://codeberg.org/VARASYS/ZDDC/releases.

There is no alpha/beta channel for binary distribution. Active dev/soak happens via the helm/zddc-server-dev/ chart, which builds zddc-server from source on every pod restart against any commit you point it at. There is no container image; if you want your own, copy the static binary into a FROM scratch or FROM alpine base in a few lines, or use one of the helm charts which compile from source via init container.

Env-var contract (for chart consumers)

Downstream Helm charts and Compose files should set these explicitly:

Variable	Typical value (behind ingress + SSO)	Purpose
ZDDC_ROOT	/srv	Path of the served archive (volume mount)
ZDDC_TLS_CERT	none	TLS terminated upstream
ZDDC_INSECURE_DIRECT	1	Acknowledge plain HTTP behind a trusted proxy
ZDDC_ADDR	:8080	Match service / probe port
ZDDC_EMAIL_HEADER	X-Auth-Request-Email	Header your auth proxy sets
ZDDC_CORS_ORIGIN	(unset)	Leave unset for embedded-tools deployments (same-origin); set to your tool host (https://tools.acme.com) only for self-hosted-tools or CDN-bootstrap layouts

See "Environment Variables" above for the full list.

Building from source

Requires Go 1.24+.

# Single binary for the host platform
(cd zddc && go build -o zddc-server ./cmd/zddc-server)

# All four release platforms (cross-compiled, statically linked)
./build   # at the repo root — silently skips if Go isn't on PATH
              # → outputs to zddc/dist/zddc-server-{linux,darwin,windows}-*

To run unit tests:

(cd zddc && go test ./...)

Release tagging

zddc-server has no separate release script. The repo's top-level ./build alpha|beta|release [version] is the canonical path: it cross-compiles the four binaries inside the containerized Go toolchain, copies them into dist/release-output/ with the lockstep symlink chain (one set per platform), regenerates the per-version + per-channel stub pages, refreshes the index, and (on stable cuts) tags zddc-server-v<X.Y.Z> alongside the five HTML-tool tags.

./build release            # lockstep stable, coordinated next version
./build release 1.2.0      # lockstep stable, explicit version
./build alpha              # lockstep alpha cut
./build beta               # lockstep beta cut
./deploy --releases        # publish dist/release-output/ to /srv/zddc/releases/

The script tags every tool but does NOT push — finish with git push origin main && git push origin --tags (and run ./deploy to put the artifacts on the live site).

Prerequisites:

• Go 1.24+ available inside the build container (downloaded automatically — docker.io/golang:1.24-alpine).
• podman (preferred) or docker on PATH.

Single-developer / solo-release flow by design — no CI babysitting, no separate dashboard to debug. The script fails loudly and visibly on the developer's terminal if anything goes wrong.

Versioning

Clean semver, lockstep across all six tools (5 HTML + zddc-server). Stable cuts get <tool>-vX.Y.Z tags for every tool, all six sharing the same X.Y.Z. There are no alpha/beta tags — channel URLs are stable URLs by design (counters defeat that). Active dev runs via helm/zddc-server-dev/, which builds from source on each rollout.

The two existing zddc-server-v0.0.8-alpha.1 and zddc-server-v0.0.8-alpha.2 tags from a previous experiment stay as historical artifacts; no new alpha/beta tags are created going forward.

---

Notes:

• The .archive virtual path resolves ZDDC tracking numbers to their earliest-received revision
• ACL is enforced via bottom-up .zddc file evaluation