bcquality/microsoft/knowledge/security/validate-user-configurable-urls.md
Jesper Schulz-Wedde a9f3c50863 Regenerate microsoft/knowledge from upstream BCApps instructions
The previous LLM-generated knowledge files contained factual
hallucinations. The most visible was the claim that `FindFirst` /
`FindLast` "forces a full-table scan" on an unfiltered record - it does
not; those APIs return a single row via the current key.

Other inaccuracies the audit found and fixed:

* `FindSet(true)` was described as "taking a LockTable". The correct
  upstream phrasing is that `FindSet(true)` sets
  `ReadIsolation::UpdLock` on the read. UpdLock and LockTable are
  related but distinct mechanisms.
* The list of production-scale tables had been invented beyond the
  upstream source (e.g. "Detailed Cust. Ledg. Entry") without a
  citation. The regenerated list matches the ten tables upstream lists
  with their P95 row counts.
* `SetLoadFields` guidance had been augmented with an extra mechanism
  claim ("the database resolves the filter using the index without
  hydrating the value") not present in upstream.

Approach: full regeneration of `microsoft/knowledge/` from the six
upstream BCApps Code Review instruction files, with Microsoft Learn /
the AL language reference as a secondary source. Every claim in every
regenerated file is anchored to a verbatim upstream quote (or a Learn
URL); the audit trail lives in artifacts/trace-<domain>.json on the
session workspace.

The PR #11 transaction/error-handling cluster is preserved verbatim:

* performance/understand-implicit-transaction-boundary.md
* performance/codeunit-run-as-atomic-sub-operation.{md,good.al,bad.al}
* performance/codeunit-run-requires-prior-commit-inside-transaction.{md,good.al,bad.al}
* performance/use-tryfunction-for-error-catching-not-rollback.{md,good.al,bad.al}
* performance/avoid-commit-inside-loops.{md,good.al,bad.al}
* security/commitbehavior-attribute-scopes-explicit-commits.{md,good.al,bad.al}
* testing/transactionmodel-attribute-governs-test-transactions.{md,good.al,bad.al}

These articles already cite Microsoft Learn and were carefully
cross-referenced; the regeneration skips their topics rather than
duplicating them.

File counts after regeneration:

  performance   35 .md  (5 preserved + 30 new)
  privacy       17 .md
  security      18 .md  (1 preserved + 17 new)
  style         33 .md
  testing        1 .md  (preserved)
  ui            19 .md
  upgrade       18 .md

Total 141 atomic knowledge files, each strictly one rule. All pass
.github/scripts/validate_frontmatter.py with 0 errors and 0 warnings.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-05-21 09:53:09 +02:00

22 lines
2.1 KiB
Markdown

---
bc-version: [all]
domain: security
keywords: [ssrf, uri, url-validation, areurishavesamehost, isvaliduripattern, httpclient]
technologies: [al]
countries: [w1]
application-area: [all]
---
# Validate URLs that come from table fields before calling them
## Description
A URL stored in a table field is user-configurable: anyone with write access to the row can change it. If that URL is then used as the target of an `HttpClient.Get`/`Post`, the extension becomes a server-side request forgery (SSRF) primitive — an attacker can redirect the call to an internal endpoint, to a metadata service, or to a malicious host that mirrors the legitimate API. The `Uri` codeunit from System Modules provides two validators built for this situation: `AreURIsHaveSameHost()` checks that two URLs share the same host (use when the hostname should not change — for example, the extension always talks to `api.contoso.com`). `IsValidURIPattern()` checks that a URL matches a wildcard pattern (use when the host varies but follows a predictable shape — for example `https://{store}.myshopify.com/...`).
## Best Practice
Before any `HttpClient` call whose URL came from a table field, call `Uri.AreURIsHaveSameHost(StoredUrl, ExpectedBaseUrl)` against a hard-coded expected base, or `Uri.IsValidURIPattern(StoredUrl, 'https://*.myshopify.com/*')` against a fixed pattern. Fail the call with an `Error` when the validator returns false. For webhook scenarios where the host is registered out-of-band, compare against the registered host stored alongside the URL. See sample: `validate-user-configurable-urls.good.al`.
## Anti Pattern
`HttpClient.Get(Setup."Service URL", Response)` or `HttpClient.Post(WebhookSetup."Callback URL", Content, Response)` with no validation step in between. The extension will dutifully send the request — and any sensitive payload — to whatever host the attacker put in the field. Reviewers should flag any `HttpClient` call whose first argument is a record field, an `OnValidate`-mutable field, or a value sourced from a table read, unless a `Uri.AreURIsHaveSameHost` or `Uri.IsValidURIPattern` check precedes it. See sample: `validate-user-configurable-urls.bad.al`.