Broken Access Control in Nestjs with Cockroachdb

Broken Access Control occurs when an API fails to enforce proper authorization checks, allowing one user to act on another user's resources. NestJS, a popular Node.js framework, provides modules, guards, and interceptors to structure authorization, but developers must wire these explicitly. CockroachDB, a distributed SQL database, does not inherently enforce row-level policies at the connection level; it relies on the application to issue correct queries with tenant or user identifiers. When a NestJS service uses a shared CockroachDB connection or pool without scoping queries to the requesting user, data from other users can be returned or modified unintentionally.

Consider a typical pattern: a controller receives a user-supplied id and passes it to a service that builds a SQL query like SELECT * FROM documents WHERE id = $1. If the service does not also filter by user_id, an attacker who iterates numeric or UUID identifiers can read or modify documents they do not own. This is a classic Insecure Direct Object Reference (IDOR), which maps to the Broken Access Control category in the OWASP API Top 10. The distributed nature of CockroachDB means queries run across nodes; without tenant isolation in SQL, a compromised service account could potentially access data belonging to other tenants if row ownership is not enforced in every query.

Another vector arises from role or permission checks performed only in the NestJS layer but not validated server-side in CockroachDB. If a service method relies solely on an in-memory role array and then constructs dynamic SQL by string interpolation, an attacker may exploit logic flaws to escalate privileges, such as changing their role in a join table or modifying admin flags. Because CockroachDB supports complex joins and constraints, it is best to enforce permissions in both the application layer (NestJS guards and interceptors) and the database layer (policies in WHERE clauses). Without this dual enforcement, the API surface expands, and the risk of unauthorized data access or mutation increases.

Middleware or interceptors that log request context can also inadvertently expose sensitive fields if structured data from CockroachDB is printed without redaction. In distributed SQL systems, query plans and execution details may reveal schema information that aids an attacker. Proper input validation and output encoding in NestJS, combined with explicit column selection in CockroachDB queries, reduce information leakage. The 12 security checks in middleBrick, including BOLA/IDOR and Property Authorization, are designed to detect these classes of flaws by correlating runtime behavior with OpenAPI specifications and database interaction patterns.

Remediation centers on ensuring every database query includes tenant or user context and that authorization decisions are verified before query construction. In NestJS, use a combination of Guards, Scopes, and Request Context to pass the authenticated user’s identifier into data access layers. With CockroachDB, always include a tenant or user column in WHERE clauses and avoid selecting by primary key alone.

Example: a secure document service in NestJS that scopes queries to the requesting user:

import { Injectable } from '@nestjs/common';
import { Pool, QueryResult } from 'pg';

@Injectable()
export class DocumentsService {
  constructor(private readonly pool: Pool) {}

  async findByUser(userId: string, documentId: string): Promise {
    const sql = 'SELECT id, title, content, user_id FROM documents WHERE id = $1 AND user_id = $2';
    const result = await this.pool.query(sql, [documentId, userId]);
    if (result.rows.length === 0) {
      throw new NotFoundException('Document not found or access denied');
    }
    return result;
  }

  async updateByUser(userId: string, documentId: string, patch: Partial<DocumentDto>): Promise<QueryResult> {
    const setClause = Object.keys(patch).map((key, i) => `${key} = $${i + 3}`).join(', ');
    const values = Object.values(patch);
    const sql = `UPDATE documents SET ${setClause} WHERE id = $${values.length + 1} AND user_id = $${values.length + 2}`;
    const result = await this.pool.query(sql, [...values, documentId, userId]);
    if (result.rowCount === 0) {
      throw new ForbiddenException('Update not allowed');
    }
    return result;
  }
}

In this example, both id and user_id are used in the WHERE clause, ensuring that even if an attacker guesses a document ID, they cannot access or modify documents belonging to other users. The same principle applies to tenant columns in multi-tenant deployments; CockroachDB’s strong consistency helps ensure that these filters are respected across distributed nodes.

NestJS Guards should validate ownership or roles before invoking services:

import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';

@Injectable()
export class DocumentOwnershipGuard implements CanActivate {
  constructor(private readonly documentsService: DocumentsService) {}

  async canActivate(context: ExecutionContext): Promise<boolean> {
    const request = context.switchToHttp().getRequest();
    const user = request.user;
    const documentId = request.params.id;
    const doc = await this.documentsService.findMetaById(documentId);
    return doc && doc.userId === user.id;
  }
}

Use the guard in a route: @UseGuards(DocumentOwnershipGuard). Combine this with parameterized SQL as shown earlier to prevent injection and ensure data isolation. For compliance mappings, these practices align with OWASP API Top 10 Broken Access Control, PCI-DSS requirements on access restrictions, and SOC2 controls around segregation of duties.

Finally, prefer explicit column lists in SELECT and UPDATE statements rather than SELECT * or dynamic object spreading. This reduces the attack surface by limiting returned fields and makes it easier to audit queries against CockroachDB’s execution plans. middleBrick’s checks for BOLA/IDOR and Property Authorization can validate that each endpoint includes proper ownership checks and that field-level permissions are enforced consistently.