Defines actors, resources, actions, rules, inheritance, defaults, and denial behavior for sharing by link. This reference fixes the adoption boundary, failure behavior, and observable evidence while leaving environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For Sharing by link, adopt a centralized server-side policy decision using authenticated subject and resource context. Enforce the control on the trusted server side, default to denial, and define threat assumptions, abuse limits, evidence, and recovery. This security block focuses specifically on policy model. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The Sharing by link actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes required for the policy model focus of this security block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Deny by default when subject, action, resource ownership, tenant, or policy version is missing or contradictory.
- Apply the same resource scope to primary records, indexes, caches, files, jobs, exports, aggregates, and support tooling.
- Do not treat a hidden UI control, client claim, route name, or hard-to-guess identifier as authorization evidence.
- Record policy version, subject, resource, action, result, and safe reason for privileged and denied decisions.
- Treat all client, callback, file, model, and telemetry fields as untrusted until authenticated and validated for the intended action.
- Require a second independent safeguard for high-impact paths where one parser, credential, or provider compromise would otherwise be decisive.
- Issue a high-entropy capability bound to one resource, allowed actions, audience or authentication requirement, expiry, download policy, and optional use limit without placing sensitive meaning in the URL.
- Hash stored tokens, redact them from logs and referrers, recheck resource policy on every use, and support immediate revocation, rotation, owner review, and safe responses to invalid links.
- For the policy model variant, enforce this declared boundary: defines actors, resources, actions, rules, inheritance, defaults, and denial behavior for sharing by link.
Implementation guidance
- Threat-model normal, replay, enumeration, cross-tenant, automation, and degraded-dependency paths before implementation review.
- Model Sharing by link inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Sharing by link contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- Policy service or context failure denies the protected operation and emits a bounded, non-sensitive investigation signal.
- Invalid or contradictory Sharing by link state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Use paired allow and deny cases at every trust boundary and confirm that loss of the control dependency fails closed.
- Monitor Sharing by link success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.