feat(backend): add structured audit logging for admin and auth actions

backend/src/logger.ts

@@ -18,3 +18,19 @@ const logger = createLogger({
 });
 
 export default logger;
+
+/** Structured audit entry for security-sensitive actions (no secrets/tokens). */
+export function auditLog(
+  actor: string,
+  action: string,
+  params: Record<string, unknown> = {},
+): void {
+  const ctx = requestContext.getStore();
+  logger.info('audit', {
+    audit: true,
+    actor,
+    action,
+    params,
+    requestId: ctx?.requestId,
+  });
+}

backend/src/middleware/auth.ts

@@ -2,7 +2,7 @@ import type { Request, Response, NextFunction } from 'express';
 import * as crypto from 'crypto';
 import * as StellarSdk from '@stellar/stellar-sdk';
 import type { AuthenticatedRequest } from '../types/auth.types.js';
-import logger from '../logger.js';
+import logger, { auditLog } from '../logger.js';
 
 const isProduction = process.env.NODE_ENV === 'production';
 const rawJwtSecret = process.env.JWT_SECRET;
@@ -181,6 +181,7 @@ export function verifyChallenge(req: Request, res: Response): void {
 
     const now = Math.floor(Date.now() / 1000);
     const token = signJwt({ sub: publicKey, iat: now, exp: now + JWT_EXPIRY_SECONDS });
+    auditLog(publicKey, 'auth.verify.success');
     res.json({ token, expiresIn: JWT_EXPIRY_SECONDS });
   } catch (err) {
     logger.error('[Auth] verifyChallenge error:', err);
@@ -210,9 +211,11 @@ export function requireAdmin(req: Request, res: Response, next: NextFunction): v
     const user = (req as AuthenticatedRequest).user;
     const adminKey = process.env.ADMIN_PUBLIC_KEY;
     if (!adminKey || user.publicKey !== adminKey) {
+      auditLog(user.publicKey, 'admin.access.denied');
       res.status(403).json({ error: 'Forbidden', message: 'Admin access required' });
       return;
     }
+    auditLog(user.publicKey, 'admin.access.granted');
     next();
   });
 }

backend/src/routes/v1/admin.routes.ts

@@ -11,7 +11,8 @@ import { prisma } from '../../lib/prisma.js';
 import { INDEXER_STATE_ID } from '../../lib/indexer-state.js';
 import { sseService } from '../../services/sse.service.js';
 import { cache } from '../../lib/redis.js';
-import logger from '../../logger.js';
+import type { AuthenticatedRequest } from '../../types/auth.types.js';
+import logger, { auditLog } from '../../logger.js';
 
 const router = Router();
 
@@ -211,6 +212,8 @@ router.post('/indexer/reset', async (req: Request, res: Response) => {
   }
   try {
     await resetIndexer(ledger);
+    const actor = (req as AuthenticatedRequest).user.publicKey;
+    auditLog(actor, 'admin.indexer.reset', { ledger });
     res.json({ ok: true, lastLedger: ledger });
   } catch (err) {
     res.status(500).json({ error: 'Reset failed' });
@@ -242,6 +245,8 @@ router.post('/indexer/replay', async (req: Request, res: Response) => {
   }
   try {
     await replayFromLedger(fromLedger);
+    const actor = (req as AuthenticatedRequest).user.publicKey;
+    auditLog(actor, 'admin.indexer.replay', { fromLedger });
     res.status(202).json({ ok: true, replayingFrom: fromLedger });
   } catch (err) {
     res.status(500).json({ error: 'Replay failed' });