bcquality/microsoft/knowledge/web-services/api-page-least-privilege-write-access.md
Michael Dieringer 67962727f6 Fix ten focused correctness items plus sample links from Jesper's 2026-09-15 re-review
Six carried-over threads:
- api-page-least-privilege-write-access fixtures: added the mandatory
  EntityName/EntitySetName properties (AL0485).
- pages-must-not-contain-business-logic fixtures: Sales Line has no
  "Total Amount" field; replaced with the real "Line Amount" (field 103).
- test-feature-scenario-tags.good.al and test-one-when-per-test.good.al:
  CreatePriceHeader leaves a price list in Draft status, which price
  calculation ignores. Added Validate(Status, Active) + Modify before the
  sales line that depends on it. Verified Status field/enum against
  PriceListHeader.Table.al and PriceStatus.Enum.al in the BCApps clone.
- exposed-objects-must-be-in-a-permission-set.md: a published codeunit is
  a SOAP endpoint (SOAP is deprecated), not OData - Page/Query are the
  OData object types. Corrected and pointed new integrations at API
  pages/queries instead.
- al-error-handling-review.md: the log-writes-must-survive-rollback cue
  selected on Session.StartSession, which only appears in the compliant
  fix, never in the anti-pattern - the bad fixture could never be
  worklisted. Recued on the actual risk shape (log insert around a
  failed TryFunction/GetLastError* path, then raise/propagate), with
  StartSession as an explicit compliant discriminator instead.
- page-design-must-match-bc-page-type-conventions.md: the enum value is
  NavigatePage, not Navigate; noted the type list is a selected subset,
  not an exhaustive PageType catalogue (PromptDialog, ConfigurationDialog,
  UserControlHost, XmlPort also exist, out of this article's scope).

Four new correctness gaps:
- release-must-update-app-version.md: "the version is the only identity"
  was backwards - id is the app's stable identity, version identifies a
  release/code-state of it.
- defensive-vs-offensive-code-must-match-blast-radius.good.al: the "low
  blast radius" example had no else branch, so a failed Customer.Get()
  left the field at its prior/default value instead of the explicit
  chosen fallback the article claims to demonstrate. Added the else.
- bcpt-scenarios-must-be-app-specific.good.al: InitTest and both measured
  StartScenario/EndScenario sections were empty/comment-only, so the
  "app-specific" fixture measured no actual work. Filled in a real,
  self-contained header+line creation path.
- upgrade-tag-logic-must-not-nest-deeply.good.al: the flattened version
  dropped both safety conditions the bad fixture had (Discount % = 0,
  nonblank posting group), silently changing behavior instead of just
  removing nesting. Extracted the guarded update into a helper with both
  conditions preserved as early exits.

Also converted this PR's remaining plain-backtick "See sample:" sample
references (16 articles) to the READ-convention markdown-link form,
matching the fix already made on #156/#158.

Rebased onto upstream/main (conflicts in al-ui-review.md, al-style-review.md,
al-upgrade-review.md against merged upstream PRs - all additive, both
sides' worklist cues retained).
2026-09-21 22:44:17 +02:00

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2.1 KiB
Markdown

---
bc-version: [all]
domain: web-services
keywords: [api-page, least-privilege, write-access, odata, security, external-api, identity-fields]
technologies: [al]
countries: [w1]
application-area: [all]
---
# Give API pages least-privilege write access
## Description
A general-purpose API page that exposes many fields should not be widened to allow writes on one additional field. A `PageType = API` page consumed by an external integration, an automation agent, or a partner system carries the same risk regardless of caller: a write-enabled page with no per-field restriction is a wide-open surface. Least privilege has to cover both dimensions of exposure: which fields are on the page, and which operations the page allows. Only a field actually placed on the page is reachable at all — but a page that includes many fields, with `InsertAllowed`/`ModifyAllowed`/`DeleteAllowed` left at their defaults and no `Editable = false` on most of them, leaves every one of those included fields — identity fields and financially significant ones among them — fully writable, with nothing marking that as deliberate. Restricting fields alone is not enough either: a page with only two fields on it can still let a caller insert brand-new records or delete existing ones if `InsertAllowed`/`DeleteAllowed` are left at their true defaults (both `true`).
## Best Practice
Create a separate, minimal API page that exposes only the key and the specific field the consumer needs to write, with everything else `Editable = false` or simply absent from the page — and set `InsertAllowed`/`DeleteAllowed` to `false` unless the consumer's use case genuinely needs to create or delete records through that page.
See sample: [`api-page-least-privilege-write-access.good.al`](api-page-least-privilege-write-access.good.al).
## Anti Pattern
Widening an existing general-purpose API page with write access to one field, leaving every other field on the page (including identity and posting fields) writable by default because no one added `Editable = false`.
See sample: [`api-page-least-privilege-write-access.bad.al`](api-page-least-privilege-write-access.bad.al).