fix(security): public-form submissions can no longer forge server-managed anchors (#3022)

The anonymous public-form surface (ADR-0056 Option A) is authorized by the
declaration-derived publicFormGrant, which short-circuits the security
middleware BEFORE every write gate (CRUD, FLS, the owner anchor guard, the
tenant CHECK). The only field-side defense was the submit route's
declared-field allow-list — and a FormView with zero declared section fields
fell back to merging the raw body wholesale, so an unauthenticated visitor
could POST owner_id=<victim> (or organization_id / audit columns / id) and
attach the record to another user or tenant: the #3004 insert-forge with no
credentials at all.

Enforce the server-managed anchors on this surface at BOTH layers from one
shared definition (PUBLIC_FORM_SERVER_MANAGED_FIELDS, new in
@objectstack/spec/security):

- plugin-security: the publicFormGrant branch strips the managed set from
  every row of a granted insert (batch included) before admitting the write —
  the data-layer boundary that holds no matter what any route lets through.
- rest: the submit allow-list excludes the set unconditionally (an explicitly
  declared owner_id no longer passes; the zero-sections fallback keeps its
  all-fields behavior for business columns only), the resolve route drops the
  fields from rendered sections + the embedded schema, and the lookup route
  refuses a publicPicker declared on a managed anchor (would open anonymous
  sys_user search). Dunder body keys (__proto__/constructor/prototype) are
  skipped so a JSON-parsed own __proto__ key cannot smuggle inherited anchors
  past own-property checks.

Proofs: publicFormGrant strip matrix in security-plugin.test.ts; route-level
matrix in public-form-routes.test.ts; end-to-end forged-owner submit in
showcase-public-form.dogfood.test.ts; authz-conformance ledger row
public-form-managed-anchors pins the boundary as enforced.

Closes #3022

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lr7QwD4Fx9KYkLH1xDMwEo

Author: claude

.changeset/public-form-server-managed-anchors.md

@@ -0,0 +1,42 @@
+---
+'@objectstack/plugin-security': patch
+'@objectstack/rest': patch
+'@objectstack/spec': patch
+---
+
+fix(security): public-form submissions can no longer forge server-managed anchors (#3022)
+
+The anonymous public-form surface (ADR-0056 Option A, `POST /forms/:slug/submit`)
+is authorized by the declaration-derived `publicFormGrant`, which short-circuits
+the security middleware BEFORE every write gate (CRUD, FLS, the owner anchor
+guard, the tenant CHECK). The only field-side defense was the route's
+declared-field allow-list — and a FormView with zero declared section fields
+fell back to merging the raw body wholesale, so an unauthenticated visitor
+could `POST owner_id=<victim>` (or `organization_id`, audit columns, `id`) and
+attach the record to another user or tenant — the #3004 insert-forge, with no
+credentials at all.
+
+Server-managed anchors are now enforced on this surface at BOTH layers, from a
+single shared definition (`PUBLIC_FORM_SERVER_MANAGED_FIELDS`, new in
+`@objectstack/spec/security`):
+
+- **Data layer (authoritative)** — the `publicFormGrant` branch in
+  `@objectstack/plugin-security` strips `id` / `owner_id` / `organization_id` /
+  `tenant_id` / audit columns / soft-delete state / `__search` from every row
+  of a granted insert (batch included) before admitting the write, so the
+  boundary holds no matter what any route lets through. Ownership stays NULL
+  for object hooks / the first-admin bootstrap to assign, as for other
+  anonymous-seeded rows.
+- **Route layer** — the submit allow-list excludes the same set
+  unconditionally: an explicitly declared `owner_id` section field no longer
+  passes, and the zero-declared-sections fallback keeps its documented
+  all-fields behavior for business columns while refusing the managed set.
+  The resolve route (`GET /forms/:slug`) drops the managed fields from the
+  rendered sections and the embedded object schema so a form never collects a
+  value the submit refuses, and `GET /forms/:slug/lookup/:field` refuses a
+  `publicPicker` declared on a managed anchor (which would have opened
+  anonymous `sys_user` search through `owner_id`).
+
+Authenticated writes are unaffected — this is the anonymous-surface rule only;
+`owner_id` transfer semantics for signed-in callers stay governed by the
+transfer grant (#3004 / PR #3018).

content/docs/ui/public-data-collection.mdx

@@ -45,6 +45,8 @@ POST /api/v1/forms/contact-us/submit   → INSERT one showcase_inquiry
 
 Only the fields listed in `sections[].fields` are accepted on submit; everything else is stripped server-side. Server-controlled fields (`status`, `source`, owner stamps) are set by a defaults hook, never by the submitter. The submit route derives a narrow `publicFormGrant: { object: 'showcase_inquiry' }` — create + read-back of the row it just made, and nothing else.
 
+System-managed anchors (`owner_id`, `organization_id`, audit columns, `id`) are **never** accepted from a public submission — not even when a section declares them, and not through the zero-sections all-fields fallback. The route filter and the data layer enforce the same set (`PUBLIC_FORM_SERVER_MANAGED_FIELDS` from `@objectstack/spec/security`), so an anonymous visitor cannot forge record ownership or tenant placement regardless of how the form is declared (#3022).
+
 ### 3. Keep the object private once inside
 
 Set `sharingModel: 'private'` on the object so submissions are staff-scoped after creation. The public path only ever **inserts**; it never lists.

packages/dogfood/test/authz-conformance.matrix.ts

@@ -114,6 +114,10 @@ export const AUTHZ_CONFORMANCE: AuthzPrimitive[] = [
     enforcement: 'plugin-security/field-masker.ts + detectForbiddenWrites' },
   { id: 'ownership-stamp', summary: 'owner_id auto-stamp on insert', state: 'enforced',
     enforcement: 'plugin-security/security-plugin.ts (insert owner_id inject)' },
+  { id: 'public-form-managed-anchors', summary: 'anonymous public-form submit cannot supply server-managed anchors (owner_id / organization_id / audit / id) — #3022', state: 'enforced',
+    enforcement: 'spec/security/public-form.ts PUBLIC_FORM_SERVER_MANAGED_FIELDS shared by rest/rest-server.ts form routes (allow-list + schema/section/lookup exposure) AND plugin-security publicFormGrant branch (strips every insert row before the grant admits the write — the data-layer boundary the grant otherwise bypasses)',
+    proof: 'showcase-public-form.dogfood.test.ts',
+    note: 'Proof file carries the forged owner_id/organization_id submit case; the route-level matrix is covered unit-side in rest public-form-routes.test.ts + plugin-security security-plugin.test.ts (publicFormGrant strip suite).' },
   { id: 'record-share', summary: 'manual record shares (sys_record_share)', state: 'enforced',
     enforcement: 'plugin-sharing/sharing-service.ts buildReadFilter/canEdit' },
   { id: 'sharing-rules', summary: 'criteria/owner sharing rules', state: 'enforced',

packages/dogfood/test/showcase-public-form.dogfood.test.ts

@@ -63,6 +63,28 @@ describe('showcase: web-to-lead public form (ADR-0056 Option A)', () => {
     expect(body.record.source).toBe('web');
   });
 
+  it('a forged owner_id / organization_id never lands on the row (#3022)', async () => {
+    const r = await stack.api('/forms/contact-us/submit', {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({
+        name: 'Mallory',
+        email: 'mallory@example.com',
+        message: 'Attach this record to the victim.',
+        owner_id: 'usr_victim',          // ← ownership forge (#3004-class, no credentials)
+        organization_id: 'org_victim',   // ← cross-tenant landing attempt
+        created_by: 'usr_victim',
+      }),
+    });
+    expect(r.status, 'the submit itself still succeeds — the anchors are stripped, not fatal').toBe(201);
+    const body = (await r.json()) as { record: Record<string, unknown> };
+    expect(body.record.name).toBe('Mallory');
+    // The anchors are server-managed on this surface: never the forged values.
+    expect(body.record.owner_id ?? null, 'anonymous submission must not forge ownership').not.toBe('usr_victim');
+    expect(body.record.organization_id ?? null, 'anonymous submission must not land cross-tenant').not.toBe('org_victim');
+    expect(body.record.created_by ?? null).not.toBe('usr_victim');
+  });
+
   it('the public grant is create + read-back ONLY — anonymous cannot list inquiries', async () => {
     const r = await stack.api('/data/showcase_inquiry');
     expect(r.status, 'general anonymous read must NOT be opened by the form grant').not.toBe(200);

packages/plugins/plugin-security/src/security-plugin.test.ts

@@ -239,6 +239,83 @@ describe('SecurityPlugin', () => {
     expect(opCtx.ast.where).toBeUndefined();
   });
 
+  // ── publicFormGrant — server-managed anchor stripping (#3022) ───────────
+  // The ADR-0056 Option A grant short-circuits the middleware BEFORE every
+  // write gate (FLS 2.5, owner anchor 3.5, tenant CHECK), so the grant branch
+  // itself must force the system-managed anchors: an anonymous public-form
+  // insert can never forge `owner_id` / `organization_id` / audit columns,
+  // no matter what the route-side field allow-list let through.
+  describe('publicFormGrant — server-managed anchor stripping (#3022)', () => {
+    const anonFormCtx = { publicFormGrant: { object: 'task' }, permissions: ['guest_portal'], anonymous: true };
+
+    const boot = async () => {
+      const plugin = new SecurityPlugin({ fallbackPermissionSet: 'member_default' });
+      const harness = makeMiddlewareCtx({ permissionSets: [tenantPolicySet] });
+      await plugin.init(harness.ctx);
+      await plugin.start(harness.ctx);
+      return harness;
+    };
+
+    it('strips forged owner_id / organization_id / audit anchors from an insert', async () => {
+      const harness = await boot();
+      const opCtx: any = {
+        object: 'task', operation: 'insert',
+        data: {
+          name: 'Ada', id: 'rec_forged', owner_id: 'usr_victim', organization_id: 'org_victim',
+          created_by: 'usr_victim', updated_by: 'usr_victim',
+          created_at: '2020-01-01T00:00:00Z', updated_at: '2020-01-01T00:00:00Z',
+        },
+        context: anonFormCtx,
+      };
+      await harness.run(opCtx);
+      // Business fields survive; every server-managed anchor is gone
+      // (ownership stays unset for hooks / first-admin bootstrap to assign).
+      expect(opCtx.data).toEqual({ name: 'Ada' });
+    });
+
+    it('strips anchors from EVERY row of a batch insert', async () => {
+      const harness = await boot();
+      const opCtx: any = {
+        object: 'task', operation: 'insert',
+        data: [
+          { name: 'A', owner_id: 'usr_victim' },
+          { name: 'B', organization_id: 'org_victim' },
+          { name: 'C' },
+        ],
+        context: anonFormCtx,
+      };
+      await harness.run(opCtx);
+      expect(opCtx.data).toEqual([{ name: 'A' }, { name: 'B' }, { name: 'C' }]);
+    });
+
+    it('a clean insert passes through untouched', async () => {
+      const harness = await boot();
+      const opCtx: any = {
+        object: 'task', operation: 'insert',
+        data: { name: 'Ada', email: 'ada@example.com' },
+        context: anonFormCtx,
+      };
+      await harness.run(opCtx);
+      expect(opCtx.data).toEqual({ name: 'Ada', email: 'ada@example.com' });
+    });
+
+    it('the grant still refuses non-granted operations and foreign objects', async () => {
+      const harness = await boot();
+      await expect(
+        harness.run({
+          object: 'task', operation: 'update', data: { owner_id: 'usr_victim' },
+          context: anonFormCtx,
+        }),
+      ).rejects.toThrow(/public-form grant permits only create\/read-back/);
+      await expect(
+        harness.run({
+          object: 'sys_user', operation: 'insert', data: { name: 'x' },
+          context: anonFormCtx,
+        }),
+      ).rejects.toThrow(/public-form grant permits only create\/read-back/);
+    });
+  });
+
   // ── Row-level WRITE authorization (pre-image check, #1985) ──────────────
   // A by-id update/delete never builds an RLS `where`, so the owner/tenant
   // predicate must be enforced by re-reading the target row before mutating.

packages/plugins/plugin-security/src/security-plugin.ts

@@ -2,7 +2,7 @@
 
 import { Plugin, PluginContext } from '@objectstack/core';
 import type { PermissionSet, RowLevelSecurityPolicy } from '@objectstack/spec/security';
-import { describeHighPrivilegeBits, describeAnchorForbiddenBits } from '@objectstack/spec/security';
+import { describeHighPrivilegeBits, describeAnchorForbiddenBits, PUBLIC_FORM_SERVER_MANAGED_FIELDS } from '@objectstack/spec/security';
 import { MCP_AGENT_PERMISSION_SET_RESTRICTED } from '@objectstack/spec/ai';
 import { PermissionEvaluator, crudBucketForOperation } from './permission-evaluator.js';
 import { DelegatedAdminGate } from './delegated-admin-gate.js';
@@ -569,7 +569,39 @@ export class SecurityPlugin implements Plugin {
         const allowed =
           opCtx.object === grantObject &&
           ['insert', 'find', 'findOne', 'count'].includes(opCtx.operation);
-        if (allowed) return next();
+        if (allowed) {
+          // [#3022] The grant bypasses every downstream write gate (FLS 2.5,
+          // owner anchor 3.5, tenant CHECK) — so the system-managed anchors
+          // must be forced HERE, before the write is admitted. An anonymous
+          // submission has no principal to backfill from and no conceivable
+          // transfer authorization, so a supplied `owner_id` /
+          // `organization_id` / audit column is stripped from every row (the
+          // route-side field allow-list is the first net; this is the
+          // data-layer boundary that holds even if a FormView declares — or
+          // a zero-section form falls open to — one of these columns).
+          // Ownership stays NULL for object hooks / the first-admin
+          // bootstrap to assign, exactly like other anonymous-seeded rows.
+          if (opCtx.operation === 'insert' && opCtx.data && typeof opCtx.data === 'object') {
+            const rows = Array.isArray(opCtx.data) ? opCtx.data : [opCtx.data];
+            const stripped = new Set<string>();
+            for (const row of rows) {
+              if (!row || typeof row !== 'object' || Array.isArray(row)) continue;
+              for (const field of PUBLIC_FORM_SERVER_MANAGED_FIELDS) {
+                if (Object.prototype.hasOwnProperty.call(row, field)) {
+                  delete (row as Record<string, unknown>)[field];
+                  stripped.add(field);
+                }
+              }
+            }
+            if (stripped.size > 0) {
+              ctx.logger.warn(
+                `[security] public-form insert on '${grantObject}' supplied server-managed ` +
+                  `field(s) [${[...stripped].join(', ')}] — stripped (#3022)`,
+              );
+            }
+          }
+          return next();
+        }
         throw new PermissionDeniedError(
           `[Security] Access denied: public-form grant permits only create/read-back on '${grantObject}', ` +
             `not '${opCtx.operation}' on '${opCtx.object}'`,