Cache Poisoning in Fiber with Cockroachdb

Cache poisoning in a Fiber application that uses CockroachDB as the backend data store occurs when an attacker causes the application or an intermediate cache to store attacker-controlled data that is later served to other users or to the same user in an incorrect context. This typically arises when dynamic responses that depend on request parameters, headers, or tenant context are cached without sufficient key differentiation or validation. Because CockroachDB is often used in distributed, multi-tenant or geo-partitioned setups, the risk is compounded when caching logic does not account for tenant identifiers, request path variations, or user-specific data scopes.

With Fiber, a high-performance Go web framework, cache poisoning can manifest when response caching is implemented at the HTTP handler level without normalizing or isolating cache keys by critical request attributes. For example, if a handler builds a cache key from the request URL path alone, two different users with different authentication or tenant context might receive the same cached response from CockroachDB because the cache key does not include user or tenant identifiers. CockroachDB’s strong consistency and SQL semantics do not inherently prevent this; the vulnerability is in how the application constructs cache keys and decides what data is safe to reuse.

An attacker can exploit this by sending requests that manipulate URL parameters, headers, or subdomain routing to trick the Fiber app into caching a malicious or sensitive response under a key that will later be reused. If the caching layer or a CDN uses the same key for different users or SQL rows fetched from CockroachDB, poisoned content can be served to unrelated users. This can lead to data leakage, incorrect business logic outcomes, or unauthorized information exposure. Because the scan categories include Input Validation and Property Authorization, middleBrick would flag cases where responses vary by tenant or user but caching does not incorporate those scopes into the cache key, and it would surface related risks in the BOLA/IDOR and Data Exposure findings.

Moreover, if the Fiber application uses shared caching infrastructure without namespace isolation, a compromised or manipulated cache entry can persist across deployments or tenant boundaries. This is especially relevant when CockroachDB is used as the source of truth and the cached representation does not reflect the latest row-level security constraints enforced by the database. The scanner tests such scenarios by probing endpoints with varied parameters and headers to detect inconsistent authorization or data exposure across requests, which can indicate insufficient cache isolation.

To mitigate cache poisoning when using CockroachDB with Fiber, ensure cache keys incorporate all dimensions that affect the response, including tenant ID, user ID, and any request parameters that change the authorized data subset. Below are concrete Go examples using a Fiber handler with a SQLx-based CockroachDB client and a simple in-memory cache layer that demonstrates secure practices.

// secure_cache_fiber.go
package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"strings"

	"github.com/gofiber/fiber/v2"
	"github.com/jmoiron/sqlx"
	_ "github.com/lib/pq"
)

type Product struct {
	ID    int    `db:"id"`
	Name  string `db:"name"`
	Price int    `db:"price"`
	Tenant string `db:"tenant_id"`
}

// cacheKey builds a namespaced key from tenant, user, path, and relevant query params.
func cacheKey(tenant, userID, path string, query map[string]string) string {
	var parts []string
	parts = append(parts, fmt.Sprintf("tenant:%s", tenant))
	parts = append(parts, fmt.Sprintf("user:%s", userID))
	parts = append(parts, fmt.Sprintf("path:%s", path))
	if len(query) > 0 {
		kv := []string{}
		for k, v := range query {
			kv = append(kv, fmt.Sprintf("%s=%s", k, v))
		}
		parts = append(parts, strings.Join(kv, "&"))
	}
	return strings.Join(parts, ":")
}

func main() {
	app := fiber.New()
	db, err := sqlx.Connect("postgres", "host=localhost port=26257 user=admin password=secret dbname=store sslmode=disable")
	if err != nil {
		log.Fatalf("failed to connect: %v", err)
	}
	// simple in-memory cache for demonstration; use a production-grade cache in practice.
	cache := make(map[string]Product)

	app.Get("/products/:id", func(c *fiber.Ctx) error {
		productID := c.Params("id")
		tenant := c.Get("X-Tenant-ID", "unknown")
		userID := c.Get("X-User-ID", "anonymous")
		query := c.Query()

		key := cacheKey(tenant, userID, c.Path(), query)
		if cached, ok := cache[key]; ok {
			return c.JSON(cached)
		}

		var p Product
		// CockroachDB query includes tenant and row-level filtering to prevent cross-tenant reads.
		querySQL := `SELECT id, name, price, tenant_id FROM products WHERE id = $1 AND tenant_id = $2`
		err := db.GetContext(context.Background(), &p, querySQL, productID, tenant)
		if err != nil {
			return c.Status(http.StatusNotFound).JSON(fiber.Map{"error": "not found"})
		}

		cache[key] = p
		return c.JSON(p)
	})

	log.Fatal(app.Listen(":3000"))
}

This example demonstrates how to construct cache keys that include tenant, user, path, and query parameters, ensuring that responses from CockroachDB are not inadvertently shared across different security contexts. For broader protection, combine this with Fiber middleware that enforces tenant and user scopes on every request and validates that cached entries respect those scopes before use.

Additionally, set reasonable TTLs and consider cache invalidation strategies when data in CockroachDB changes. Avoid caching responses that contain sensitive or user-specific data unless the cache key fully captures the security boundary. middleBrick’s scans will highlight missing tenant or user context in cache keys under Data Exposure and BOLA/IDOR checks, and its findings include remediation guidance to harden the implementation.