feat: revocable read-only API keys for machine access

Integrations such as the Wabenhain shop sync no longer need a service
account with a password (and without MFA). An admin creates a key under
Verwaltung > Automatisierung > API-Schlüssel.

- Key format ack_<8>_<43>; only its SHA-256 hash is stored, the key is
  shown exactly once. Optional expiry, "last used" timestamp, revocation
  takes effect immediately; create/revoke are audit-logged without the key.
- A key is not a user: JwtAuthGuard sets request.apiKey, PermissionsGuard
  admits it only to routes whose permission is among its scopes and never
  to user-only routes. Scopes come from a short allowlist (shop-sync:read).
- Managing keys requires the new permission api-keys:manage.
- Keys are excluded from backups on purpose; a restore means issuing a new
  key.

Additive migration (new table).

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

ApiCore-Backend/src/api-keys/api-keys.service.ts

@@ -0,0 +1,162 @@
+import { Injectable, NotFoundException } from '@nestjs/common';
+import { createHash, randomBytes, randomInt } from 'node:crypto';
+import { PrismaService } from '../prisma/prisma.service';
+import { AuditLogService } from '../audit/audit-log.service';
+import { ApiKey } from '../../generated/prisma';
+import { CreateApiKeyDto } from './dto/create-api-key.dto';
+import { ApiKeyScope, isApiKeyScope } from './api-key-scopes';
+
+// ack_<8 lowercase chars>_<32 random bytes, base64url>
+const TOKEN_PATTERN = /^ack_[a-z0-9]{8}_[A-Za-z0-9_-]{43}$/;
+const PREFIX_ALPHABET = 'abcdefghijklmnopqrstuvwxyz0123456789';
+// lastUsedAt is informational; writing it on every request would turn each
+// read into a write for no benefit.
+const LAST_USED_RESOLUTION_MS = 5 * 60 * 1000;
+
+/** What a request authenticated by an API key may do - it is not a user. */
+export interface ApiKeyPrincipal {
+  id: string;
+  scopes: ApiKeyScope[];
+}
+
+/** An API key as shown in the admin UI - never the hash or the key itself. */
+export type ApiKeySummary = Omit<ApiKey, 'keyHash'>;
+
+export interface CreatedApiKey {
+  apiKey: ApiKeySummary;
+  /** The only time the plain key exists outside the caller's system. */
+  token: string;
+}
+
+function hashToken(token: string): string {
+  return createHash('sha256').update(token).digest('hex');
+}
+
+function randomPrefix(): string {
+  let prefix = '';
+  for (let i = 0; i < 8; i++) {
+    prefix += PREFIX_ALPHABET[randomInt(PREFIX_ALPHABET.length)];
+  }
+  return `ack_${prefix}`;
+}
+
+function toSummary(apiKey: ApiKey): ApiKeySummary {
+  const { keyHash, ...summary } = apiKey;
+  void keyHash;
+  return summary;
+}
+
+@Injectable()
+export class ApiKeysService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly auditLog: AuditLogService,
+  ) {}
+
+  async findAll(): Promise<ApiKeySummary[]> {
+    const keys = await this.prisma.apiKey.findMany({
+      orderBy: { createdAt: 'desc' },
+    });
+    return keys.map(toSummary);
+  }
+
+  async create(
+    dto: CreateApiKeyDto,
+    actingUserId: string,
+  ): Promise<CreatedApiKey> {
+    const prefix = randomPrefix();
+    // 32 random bytes: a plain hash of it is safe to store without a slow
+    // KDF - there is nothing guessable to brute-force.
+    const token = `${prefix}_${randomBytes(32).toString('base64url')}`;
+    const expiresAt =
+      dto.expiresInDays !== undefined
+        ? new Date(Date.now() + dto.expiresInDays * 24 * 60 * 60 * 1000)
+        : null;
+
+    const apiKey = await this.prisma.apiKey.create({
+      data: {
+        name: dto.name.trim(),
+        prefix,
+        keyHash: hashToken(token),
+        scopes: [...new Set(dto.scopes)],
+        expiresAt,
+        createdByUserId: actingUserId,
+      },
+    });
+    const summary = toSummary(apiKey);
+    await this.auditLog.record({
+      entityType: 'ApiKey',
+      entityId: apiKey.id,
+      action: 'CREATE',
+      userId: actingUserId,
+      afterData: summary,
+    });
+    return { apiKey: summary, token };
+  }
+
+  async revoke(id: string, actingUserId: string): Promise<ApiKeySummary> {
+    const before = await this.prisma.apiKey.findUnique({ where: { id } });
+    if (!before) {
+      throw new NotFoundException('API-Schlüssel nicht gefunden');
+    }
+    if (before.revokedAt) {
+      return toSummary(before);
+    }
+    const revoked = await this.prisma.apiKey.update({
+      where: { id },
+      data: { revokedAt: new Date() },
+    });
+    await this.auditLog.record({
+      entityType: 'ApiKey',
+      entityId: id,
+      action: 'DEACTIVATE',
+      userId: actingUserId,
+      beforeData: toSummary(before),
+      afterData: toSummary(revoked),
+    });
+    return toSummary(revoked);
+  }
+
+  /**
+   * Resolves a presented key to what it may do, or null for anything that
+   * must not pass: malformed, unknown, revoked or expired.
+   */
+  async authenticate(token: string): Promise<ApiKeyPrincipal | null> {
+    if (!TOKEN_PATTERN.test(token)) {
+      return null;
+    }
+    const apiKey = await this.prisma.apiKey.findUnique({
+      where: { keyHash: hashToken(token) },
+    });
+    const now = new Date();
+    if (
+      !apiKey ||
+      apiKey.revokedAt ||
+      (apiKey.expiresAt && apiKey.expiresAt <= now)
+    ) {
+      return null;
+    }
+    if (
+      !apiKey.lastUsedAt ||
+      now.getTime() - apiKey.lastUsedAt.getTime() > LAST_USED_RESOLUTION_MS
+    ) {
+      await this.prisma.apiKey.update({
+        where: { id: apiKey.id },
+        data: { lastUsedAt: now },
+      });
+    }
+    // Intersect with today's allowlist: narrowing it later also narrows
+    // keys issued before.
+    return { id: apiKey.id, scopes: apiKey.scopes.filter(isApiKeyScope) };
+  }
+}
+
+/** The key from an `Authorization: Bearer ack_…` header, or null. */
+export function extractApiKeyToken(
+  authorization: string | undefined,
+): string | null {
+  if (!authorization?.startsWith('Bearer ack_')) {
+    return null;
+  }
+  return authorization.slice('Bearer '.length).trim();
+}