Sandbox Escape in Fiber with Cockroachdb

A sandbox escape in a Fiber service that uses CockroachDB typically occurs when application logic or configuration allows an attacker to move beyond intended isolation boundaries, often leveraging database features or API behavior to reach host resources or execute unintended operations. In this combination, the risk is not inherent to CockroachDB itself but arises from how the Fiber application interacts with it.

Consider a scenario where a Fiber endpoint dynamically constructs CockroachDB connection strings or queries using user-supplied input without strict validation. If input validation is weak (one of the 12 parallel checks performed by middleBrick), an attacker might inject connection parameters that point to external hosts or administrative endpoints. For example, a malicious payload could redirect queries to a sensitive internal service, probing for metadata or configuration details that are not normally exposed. Because middleBrick tests input validation as a core security check, it can detect cases where user-controlled data influences database connection behavior.

Another pathway involves the use of CockroachDB’s built-in SQL functions or administrative endpoints that may be accessible through the application’s database user. If the Fiber app uses a highly privileged database account, an attacker who can inject or manipulate queries might leverage functions like crdb_internal or file operations to read server-side files or execute commands. This becomes a sandbox escape when the injected query causes the database to interact with the host filesystem or network in ways the application did not intend. middleBrick’s checks for SSRF and Property Authorization help surface these risks by identifying whether database responses expose internal endpoints or sensitive configuration properties.

Unauthenticated endpoints also play a role. If a Fiber route that interacts with CockroachDB is exposed without authentication, middleBrick’s unauthenticated attack surface testing can reveal whether an attacker can directly invoke database-influencing operations. For instance, an endpoint that accepts a table name or schema name as a parameter and passes it to raw SQL without sanitization could allow an attacker to enumerate system tables or trigger administrative actions. This aligns with BOLA/IDOR and BFLA/Privilege Escalation checks, which examine whether object-level permissions are properly enforced across endpoints.

Finally, insecure consumption patterns—such as trusting database metadata returned to the client or exposing internal error messages containing query details—can amplify the impact of a sandbox escape. middleByte’s Data Exposure and Unsafe Consumption checks look for sensitive data or code in outputs, including LLM responses if applicable, ensuring that CockroachDB errors or schema details do not leak in a way that aids further exploitation.

Remediation centers on strict input validation, least-privilege database access, and secure query construction in your Fiber application. Below are concrete examples using the CockroachDB Go driver.

1. Use parameterized queries and avoid dynamic SQL

Never concatenate user input directly into SQL strings. Instead, use placeholders and prepared statements.

package main

import (
	"context"
	"github.com/gofiber/fiber/v2"
	"github.com/lib/pq"
	"database/sql"
)

func getUser(c *fiber.Ctx) error {
	ctx := c.Context()
	var userID string = c.Params("id") // Assume validated elsewhere
	db, _ := sql.Open("postgres", "postgresql://user:pass@localhost:26257/mydb?sslmode=require")
	defer db.Close()

	var name string
	// Safe: parameterized query
	err := db.QueryRowContext(ctx, "SELECT name FROM users WHERE id = $1", userID).Scan(&name)
	if err != nil {
		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{"error": "unable to fetch user"})
	}
	return c.JSON(fiber.Map{"name": name})
}

2. Apply principle of least privilege to the CockroachDB user

Ensure the database user used by Fiber has only the permissions needed for the task. Avoid using the root or admin user for routine operations.

-- Example CockroachDB role setup (run separately in CockroachDB SQL shell)
CREATE ROLE fiber_app WITH LOGIN PASSWORD 'secure_password';
GRANT SELECT, INSERT ON TABLE users TO fiber_app;
REVOKE ALL ON DATABASE mydb FROM PUBLIC;
-- Then connect with this role in your Fiber app connection string

3. Validate and sanitize all inputs that influence database behavior

If your endpoint accepts identifiers that map to database objects, use an allowlist approach.

func safeTableHandler(c *fiber.Ctx) error {
	allowedTables := map[string]bool{"users": true, "products": true}
	tableName := c.Params("table")
	if !allowedTables[tableName] {
		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{"error": "invalid table"})
	}
	// Proceed with safe, parameterized access
	// ...
	return c.SendString("OK")
}

4. Restrict network exposure and use secure connections

Configure your Fiber server and CockroachDB connection to use TLS and avoid binding to public interfaces unless necessary.

// In your Fiber app setup
app := fiber.New(fiber.Config{
	ServerHeader: "Fiber",
})
// Use TLS when connecting to CockroachDB
connStr := "postgresql://user:pass@localhost:26257/mydb?sslmode=require&sslcert=client.crt&sslkey=client.key"

5. Monitor and limit query results to prevent data exposure

Ensure that queries do not return more data than needed, and avoid exposing internal errors.

func getLimited(c *fiber.Ctx) error {
	ctx := c.Context()
	db, _ := sql.Open("postgres", "...")
	rows, err := db.QueryContext(ctx, "SELECT id, name FROM users LIMIT 100")
	if err != nil {
		c.SendStatus(fiber.StatusInternalServerError)
		return nil
	}
	defer rows.Close()
	// process rows safely
	return c.JSON(/* processed data */)
}