fix(stock): require raw-material permission to consume, guard quantity edits

Security review findings on the raw material commit:
- Creating a production batch with inputs books raw material off other
  lots; production-batch:create alone no longer suffices, the user also
  needs raw-material:withdraw (403 otherwise).
- Correcting the quantity of a raw lot or production batch below what was
  already consumed, sold or withdrawn is refused (row lock + check in the
  same transaction) instead of silently driving the remaining stock
  negative; shortfalls go through an inventory correction.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Backend/src/production-batches/production-batches.service.ts

@@ -1,9 +1,11 @@
 import {
   BadRequestException,
   ConflictException,
+  ForbiddenException,
   Injectable,
   NotFoundException,
 } from '@nestjs/common';
+import { PermissionResolverService } from '../auth/permissions/permission-resolver.service';
 import { PrismaService } from '../prisma/prisma.service';
 import { AuditLogService } from '../audit/audit-log.service';
 import { StockService } from '../stock/stock.service';
@@ -38,6 +40,7 @@ export class ProductionBatchesService {
     private readonly prisma: PrismaService,
     private readonly auditLog: AuditLogService,
     private readonly stock: StockService,
+    private readonly permissions: PermissionResolverService,
   ) {}
 
   async findAll(filter: ProductionBatchFilter = {}) {
@@ -66,6 +69,16 @@ export class ProductionBatchesService {
   }
 
   async create(dto: CreateProductionBatchDto, actingUserId: string) {
+    // Consuming raw material is a withdrawal from someone else's stock:
+    // production-batch:create alone must not be enough to empty a wax lot.
+    if (dto.inputs && dto.inputs.length > 0) {
+      const granted = await this.permissions.getPermissions(actingUserId);
+      if (!granted.has('raw-material:withdraw')) {
+        throw new ForbiddenException(
+          'Rohstoffe verbrauchen erfordert die Berechtigung "Rohstoffe: Entnehmen und Inventur"',
+        );
+      }
+    }
     const product = await this.prisma.product.findUnique({
       where: { id: dto.productId },
     });
@@ -124,20 +137,29 @@ export class ProductionBatchesService {
     actingUserId: string,
   ) {
     const before = await this.findById(id);
-    await this.prisma.productionBatch.update({
+    await this.prisma.$transaction(async (tx) => {
-      where: { id },
+      if (dto.quantity !== undefined && dto.quantity !== before.quantity) {
-      data: {
+        await this.stock.assertInitialCovers(
-        lotNumber: dto.lotNumber,
+          tx,
-        date: dto.date ? new Date(dto.date) : undefined,
+          { kind: 'production', id },
-        quantity: dto.quantity,
+          dto.quantity,
-        bestBeforeDate:
+        );
-          dto.bestBeforeDate === undefined
+      }
-            ? undefined
+      await tx.productionBatch.update({
-            : dto.bestBeforeDate === null
+        where: { id },
-              ? null
+        data: {
-              : new Date(dto.bestBeforeDate),
+          lotNumber: dto.lotNumber,
-        notes: dto.notes,
+          date: dto.date ? new Date(dto.date) : undefined,
-      },
+          quantity: dto.quantity,
+          bestBeforeDate:
+            dto.bestBeforeDate === undefined
+              ? undefined
+              : dto.bestBeforeDate === null
+                ? null
+                : new Date(dto.bestBeforeDate),
+          notes: dto.notes,
+        },
+      });
     });
     const after = await this.findById(id);
     await this.auditLog.record({

ApiCore-Backend/src/raw-materials/raw-materials.service.ts

@@ -99,16 +99,25 @@ export class RawMaterialsService {
 
   async update(id: string, dto: UpdateRawMaterialLotDto, actingUserId: string) {
     const before = await this.findById(id);
-    await this.prisma.rawMaterialLot.update({
+    await this.prisma.$transaction(async (tx) => {
-      where: { id },
+      if (dto.quantity !== undefined && dto.quantity !== before.quantity) {
-      data: {
+        await this.stock.assertInitialCovers(
-        lotNumber: dto.lotNumber,
+          tx,
-        date: dto.date ? new Date(dto.date) : undefined,
+          { kind: 'raw', id },
-        quantity: dto.quantity,
+          dto.quantity,
-        apiaryId: dto.apiaryId,
+        );
-        harvestId: dto.harvestId,
+      }
-        notes: dto.notes,
+      await tx.rawMaterialLot.update({
-      },
+        where: { id },
+        data: {
+          lotNumber: dto.lotNumber,
+          date: dto.date ? new Date(dto.date) : undefined,
+          quantity: dto.quantity,
+          apiaryId: dto.apiaryId,
+          harvestId: dto.harvestId,
+          notes: dto.notes,
+        },
+      });
     });
     const after = await this.findById(id);
     await this.auditLog.record({

ApiCore-Backend/src/stock/stock.service.ts

@@ -304,6 +304,28 @@ export class StockService {
     }
   }
 
+  /**
+   * Guards a corrected initial quantity (produced pieces, harvested grams):
+   * it may not drop below what was already sold, withdrawn or consumed -
+   * that would turn the remaining stock negative without anyone booking a
+   * movement. Locks the stock row; call inside the transaction that writes
+   * the new quantity. A real shortfall belongs in an inventory correction.
+   */
+  async assertInitialCovers(
+    tx: Tx,
+    target: StockTarget,
+    newInitial: number,
+  ): Promise<void> {
+    await this.lock(tx, target);
+    const sums = await this.sumMovements(tx, target.kind, [target.id]);
+    const moved = sums.get(target.id) ?? 0;
+    if (newInitial + moved < 0) {
+      throw new BadRequestException(
+        `Menge ${newInitial} ist kleiner als bereits verbucht (${-moved}) - Fehlmengen bitte über "Inventur korrigieren" buchen`,
+      );
+    }
+  }
+
   /**
    * Gives the raw material of a production batch back - only for a batch
    * deleted as a typo. The give-back is a movement of its own, so the raw

ApiCore-Backend/test/raw-materials.e2e-spec.ts

@@ -176,6 +176,61 @@ describe('Raw materials and production (e2e)', () => {
     expect((await stockOf(propolisId)).summary.remaining).toBe(200);
   });
 
+  it('refuses to correct a raw lot below what was already used or withdrawn', async () => {
+    // wax: 1000 g harvested, 100 g withdrawn -> at least 100 g must remain booked
+    await auth(request(server()).patch(`/api/v1/raw-material-lots/${waxId}`))
+      .send({ quantity: 50 })
+      .expect(400);
+    await auth(request(server()).patch(`/api/v1/raw-material-lots/${waxId}`))
+      .send({ quantity: 950 })
+      .expect(200);
+    expect((await stockOf(waxId)).summary.remaining).toBe(850);
+  });
+
+  it('needs the raw material withdraw permission to consume raw material', async () => {
+    const role = await prisma.role.create({
+      data: {
+        key: `PRODUCER_ONLY_${suffix}`,
+        name: `Nur Herstellung ${suffix}`,
+        permissions: {
+          create: (
+            await prisma.permission.findMany({
+              where: {
+                key: {
+                  in: ['production-batch:read', 'production-batch:create'],
+                },
+              },
+            })
+          ).map((permission) => ({ permissionId: permission.id })),
+        },
+      },
+    });
+    await prisma.user.create({
+      data: {
+        email: `raw-producer-${suffix}@example.com`,
+        passwordHash: await bcrypt.hash(password, 12),
+        name: 'Producer',
+        roleId: role.id,
+      },
+    });
+    const producerToken = (
+      await login(app, `raw-producer-${suffix}@example.com`, password)
+    ).accessToken;
+
+    await request(server())
+      .post('/api/v1/production-batches')
+      .set('Authorization', `Bearer ${producerToken}`)
+      .send({
+        productId,
+        lotNumber: `S3-${suffix}`,
+        date: '2026-06-12',
+        quantity: 5,
+        inputs: [{ rawMaterialLotId: propolisId, quantity: 10 }],
+      })
+      .expect(403);
+    expect((await stockOf(propolisId)).summary.remaining).toBe(200);
+  });
+
   it('keeps a raw lot with movements as history', async () => {
     await auth(
       request(server()).delete(`/api/v1/raw-material-lots/${waxId}`),