apex-stripinaccessible-and-fls-enforcement

# Apex stripInaccessible and FLS Enforcement

Activate when Apex code accepts records from a less-privileged context (LWC, Aura, REST, Visualforce) and writes them to the database, OR when query results need to be scrubbed of fields the running user cannot read. `Security.stripInaccessible(AccessType, records)` removes inaccessible fields from a record collection and returns an `SObjectAccessDecision` you must operate on instead of the original list.

---

## Before Starting

- Confirm the records are user-supplied. Internal trusted-context data (e.g., trigger handler reading from the trigger context with `without sharing`) does not need stripInaccessible.
- Decide the AccessType: are you reading, creating, updating, or upserting? The wrong enum will silently strip the wrong fields.
- Confirm the calling class's sharing keyword. `with sharing` enforces record visibility; stripInaccessible enforces FIELD visibility. Both are needed for full enforcement.
- If the SOQL itself is fetching records to return to a less-privileged caller, prefer `WITH USER_MODE` (Summer '23+) on the query and skip a redundant strip pass.

---

## Core Concepts

### The four AccessType enum values

`AccessType` is the first argument to `Security.stripInaccessible`. Each value evaluates a different permission:

| Enum | What it strips | When to use |
|---|---|---|
| `AccessType.READABLE` | Fields the user cannot read. | AFTER a SOQL query whose results you'll return to a less-privileged caller. |
| `AccessType.CREATABLE` | Fields the user cannot create. | BEFORE `insert`. |
| `AccessType.UPDATABLE` | Fields the user cannot update. | BEFORE `update`. |
| `AccessType.UPSERTABLE` | Fields the user cannot create OR update (strict intersection — a field must be both creatable AND updatable to survive). | BEFORE `upsert`. |

Picking the wrong AccessType is a real bug. `READABLE` before an `update` will leave create-only or update-only fields in the payload that the user could not have set themselves.

### SObjectAccessDecision — getRecords, getRemovedFields, getModifiedRecords

`Security.stripInaccessible(...)` returns an immutable `SObjectAccessDecision`. You cannot mutate the original list and call it safe — you must operate on the decision's outputs:

- **`getRecords()`** — the sanitized list with inaccessible fields removed. Always DML on this, never on the original argument.
- **`getRemovedFields()`** — a `Map<String, Set<String>>` keyed by SObject API name, value is the set of removed field API names. Useful for logging/audit and for surfacing soft warnings.
- **`getModifiedRecords()`** — a `Map<Id, SObject>` of records that had at least one field stripped (post-DML id only — useful when re-fetching).

### Canonical pattern wrapping DML

```
public void createCases(List<Case> userSupplied) {
    SObjectAccessDecision decision =
        Security.stripInaccessible(AccessType.CREATABLE, userSupplied);

    if (!decision.getRemovedFields().isEmpty()) {
        ApplicationLogger.warn('createCases',
            JSON.serialize(decision.getRemovedFields()));
    }

    insert decision.getRecords();   // NEVER `insert userSupplied;`
}
```

The single most common bug is calling `insert userSupplied;` after the strip — the strip then has zero effect.

### When stripInaccessible is the right choice vs WITH USER_MODE

| Goal | Prefer |
|---|---|
| Querying records to return/manipulate as the running user | `WITH USER_MODE` on the SOQL itself |
| DML on records assembled from user input (e.g., REST body) | `stripInaccessible(CREATABLE/UPDATABLE/UPSERTABLE, ...)` |
| Apex constructed records, no SOQL involved | `stripInaccessible` |
| Backwards compat to API 47 or earlier | `WITH SECURITY_ENFORCED` (legacy) |
| Need granular per-field reporting (which fields were removed) | `stripInaccessible` (USER_MODE throws, doesn't strip) |

Rule of thumb: `WITH USER_MODE` is THROW-on-inaccessible, `stripInaccessible` is REMOVE-and-continue. Pick based on whether silent partial success is acceptable.

### Performance — per-record FLS evaluation

`stripInaccessible` evaluates FLS for every field on every record. For large lists (10k+) it consumes CPU. It does NOT count against SOQL/DML governor limits, but it does count against the 10-second sync CPU limit. Profile before strip-then-DML on huge collections; consider chunking.

### Gotcha: parent-child relationships are NOT recursively stripped

`stripInaccessible` evaluates fields on the SObject collection you pass. If a `Case` carries a populated `Contact` lookup with nested fields (e.g., `caseRec.Contact.Email`), those nested fields are NOT evaluated. You must strip child collections separately.

```
SObjectAccessDecision parents  = Security.stripInaccessible(AccessType.UPDATABLE, cases);
SObjectAccessDecision contacts = Security.stripInaccessible(
    AccessType.UPDATABLE,
    Pluck.contacts(parents.getRecords())  // your own helper
);
```

### Interaction with Schema.SObjectField.isCreateable / isUpdateable / isAccessible

`Schema.DescribeFieldResult.isCreateable()` is a CHEAP proactive check — use it to fail fast before assembling a payload. `stripInaccessible` is an EXPENSIVE post-hoc scrub — use it as the enforcement gate. They are complementary, not redundant.

```
if (!Schema.sObjectType.Account.fields.AnnualRevenue.isCreateable()) {
    throw new AuraHandledException('You cannot set AnnualRevenue.');
}
// later, still call stripInaccessible before insert as defense-in-depth.
```

### Testing with System.runAs

Tests run as the system user by default — FLS is bypassed. To prove stripInaccessible actually strips, create a non-admin user with limited permissions and wrap your test in `System.runAs(testUser)`. Without `runAs`, your strip call returns the input unchanged and your test passes for the wrong reason.

---

## Common Patterns

### Pattern: REST endpoint — strip before DML

**When to use:** `@RestResource` accepting a JSON body of records.

**How it works:** Deserialize, strip with the appropriate AccessType, log removed fields for audit, DML on the stripped result.

**Why not the alternative:** Trusting the JSON payload assumes the running user can set every field they sent — they often cannot.

### Pattern: Aura/LWC controller — strip on the way out

**When to use:** `@AuraEnabled` method returning records to the client.

**How it works:** Query with `WITH USER_MODE` (preferred) OR strip the result with `AccessType.READABLE` before returning. Returning unscrubbed records lets the client see fields the user cannot read in the UI.

### Pattern: Defense-in-depth with WITH USER_MODE + stripInaccessible

**When to use:** The query already uses USER_MODE, but you also need to write back updates from a partially user-controlled object.

**How it works:** USER_MODE protects the read; stripInaccessible(UPDATABLE) protects the write. Each guards a different operation — do not collapse them.

---

## Decision Guidance

| Situation | Recommended Approach | Reason |
|---|---|---|
| REST/LWC inserts user-supplied records | `stripInaccessible(CREATABLE, ...)` then DML on `getRecords()` | Records originate from a less-trusted client |
| Aura controller returns records | `WITH USER_MODE` on the SOQL | Throws on inaccessible read, no silent strip |
| Upsert from a user-supplied list | `stripInaccessible(UPSERTABLE, ...)` | Intersects creatable AND updatable |
| Internal trigger handler updating fields the running user can edit anyway | Skip — not user-supplied | stripInaccessible cost not justified |
| Need to know WHICH fields got removed for audit | `stripInaccessible` + `getRemovedFields()` | USER_MODE throws, gives no per-field detail |
| Running on API < 48 | `WITH SECURITY_ENFORCED` | stripInaccessible introduced in API 45, USER_MODE in 58 |

---

## Recommended Workflow

1. Identify entry points where records cross from less-privileged caller (LWC, Aura, REST, Visualforce) into Apex. Mark every parameter.
2. For each entry point, pick the correct `AccessType` based on the DML you'll perform (CREATABLE for insert, UPDATABLE for update, UPSERTABLE for upsert, READABLE for outbound payloads).
3. Replace the raw DML on the input list with DML on `Security.stripInaccessible(type, input).getRecords()`. Capture the decision in a local variable so you can also call `getRemovedFields()`.
4. Strip child collections separately if relationships are populated — parent strip does NOT recurse.
5. Log `getRemovedFields()` (or surface as a warning to the caller) so silent stripping is observable.
6. Add a test under `System.runAs(nonAdminUser)` that proves a restricted field IS stripped. The same test under default system context should be a no-op.
7. Run `python3 scripts/check_apex_stripinaccessible_and_fls_enforcement.py` over the changed `.cls` files to catch the "stripped-then-DML-on-original" mistake.

---

## Review Checklist

- [ ] Every user-supplied record list passes through `Security.stripInaccessible` before DML
- [ ] DML targets `decision.getRecords()`, never the original argument
- [ ] `AccessType` matches the DML operation (CREATABLE/UPDATABLE/UPSERTABLE)
- [ ] Outbound query results either use `WITH USER_MODE` or `AccessType.READABLE` strip
- [ ] Child collections are stripped independently when relationships are populated
- [ ] `getRemovedFields()` is logged or surfaced; silent stripping is forbidden
- [ ] Test class uses `System.runAs(nonAdminUser)` and asserts a restricted field was removed
- [ ] No double-enforcement (USER_MODE in SOQL AND READABLE strip on the same path)

---

## Salesforce-Specific Gotchas

1. **DML on the original list silently bypasses the strip.** `stripInaccessible(...).getRecords()` returns a NEW list. Calling `insert userSupplied;` after the strip line does nothing — the strip's effect is in `getRecords()`.
2. **Parent strip does not recurse into child collections.** `Security.stripInaccessible(UPDATABLE, cases)` does not evaluate fields on `case.Contact.*`. Strip child collections separately.
3. **Tests pass under system context regardless of FLS.** Without `System.runAs(nonAdminUser)`, every field is accessible and your strip call is a no-op — the test proves nothing.
4. **`AccessType.UPSERTABLE` is the intersection of CREATABLE and UPDATABLE.** A field accessible for create but not update gets stripped on UPSERTABLE — this is correct behavior for upsert but surprising if you expected union semantics.
5. **`SObjectAccessDecision` is immutable.** You cannot mutate `getRecords()` results and have those changes reflect anywhere; call DML directly on the returned list.

---

## Output Artifacts

| Artifact | Description |
|---|---|
| Sanitized DML payload | `decision.getRecords()` — the only safe input to `insert`/`update`/`upsert` |
| Removed-fields audit | `decision.getRemovedFields()` map for logging or warnings |
| FLS enforcement test | Test under `System.runAs(nonAdmin)` proving restricted field stripped |
| AccessType decision note | Documented choice of CREATABLE / UPDATABLE / UPSERTABLE / READABLE per entry point |

---

## Related Skills

- `apex/apex-with-user-mode-soql` — when to prefer USER_MODE on the SOQL itself
- `apex/apex-sharing-keywords` — class-level `with sharing` / `without sharing` / `inherited sharing` (record visibility, complements FLS)
- `apex/apex-security-utils` — using the shared `templates/apex/SecurityUtils.cls` helpers
- `security/security-fls-crud-enforcement` — broader CRUD/FLS strategy across the org