Cache Poisoning in Echo Go with Api Keys

Cache poisoning in the Echo Go ecosystem occurs when an attacker manipulates cached responses by injecting attacker-controlled data, often tied to how API keys are handled in request processing. When API keys are used for authentication but not properly isolated in cache keys, a cached response intended for one client may be served to another client with a different key, leading to data leakage or unauthorized access patterns. This is particularly risky when the cache key is derived from the request path or headers without including the API key or a normalized representation of the authenticated context.

In Echo Go, developers often use middleware to validate API keys and then proceed to serve responses that may be cached by an upstream layer (e.g., CDN, in-memory cache). If the cache key does not incorporate the API key or a hashed representation of the authenticated subject, two different requests with distinct API keys but similar paths can map to the same cache entry. An attacker who knows or guesses a valid API key pattern could cause the server to cache a response containing sensitive data under that key, which may later be served to other users if their requests coincidentally match the same cache key.

For example, consider an endpoint /api/v1/user/profile that caches responses for 60 seconds. If the cache key is simply GET:/api/v1/user/profile, then any authenticated user’s profile data could be served to others. Including the API key in the cache key mitigates this but introduces a new concern: if the API key is logged or exposed in server-side logs during cache operations, it may become a target for exfiltration. The LLM/AI Security checks in middleBrick specifically test for such data exposure risks by scanning for API keys in outputs and inspecting how endpoints handle sensitive values in both runtime and spec-defined flows.

This combination is also relevant to broader API security checks such as BOLA/IDOR and Data Exposure, where improper scoping of cached data intersects with authentication context. MiddleBrick’s 12 security checks run in parallel to detect these issues, including tracing how API keys flow through request handling and whether cached responses inadvertently bypass authentication boundaries.

To remediate cache poisoning risks related to API keys in Echo Go, ensure that cache keys are constructed using a combination of the request path and a normalized, non-sensitive representation of the authenticated identity, such as a hashed API key or user ID, never the raw key itself. Avoid including raw API keys in logs, URLs, or cache entries. Below are examples demonstrating secure handling in Echo Go middleware and cache logic.

Secure API Key Validation and Cache Key Construction

// main.go
package main

import (
	"crypto/sha256"
	"encoding/hex"
	"net/http"

	"github.com/labstack/echo/v4"
)

func main() {
	e := echo.New()

	e.Use(func(next echo.HandlerFunc) echo.HandlerFunc {
		return func(c echo.Context) error {
			apiKey := c.Request().Header.Get("X-API-Key")
			if apiKey == "" {
				return echo.NewHTTPError(http.StatusUnauthorized, "missing api key")
			}
			// Normalize and hash the API key for safe use in cache context
			h := sha256.New()
			h.Write([]byte(apiKey))
			hashedKey := hex.EncodeToString(h.Sum(nil))
			// Store a non-sensitive reference (e.g., first 8 chars for logging if needed)
			c.Set("cacheKeySuffix", hashedKey[:8])
			return next(c)
		}
	})

	e.GET("/api/v1/user/profile", func(c echo.Context) error {
		userID := c.Get("user_id").(string) // Assume set after further auth validation
		suffix := c.Get("cacheKeySuffix").(string)
		cacheKey := "profile:" + userID + ":" + suffix
		// Use cacheKey with your caching layer; ensure raw API key is not stored
		return c.JSON(http.StatusOK, map[string]string{"cache_key": cacheKey})
	})

	e.Logger.Fatal(e.Start(":8080"))
}

Avoiding Raw Key Exposure in Logs and Cache

// logging middleware example
func secureLogger(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		apiKey := c.Request().Header.Get("X-API-Key")
		// Never log raw API key
		if apiKey != "" {
			h := sha256.New()
			h.Write([]byte(apiKey))
			c.Set("key_hash", hex.EncodeToString(h.Sum(nil)))
		}
		return next(c)
	}
}

These examples ensure that API keys are not stored or logged in cleartext and that cache keys incorporate a one-way transformation of the key, reducing the risk of cache poisoning across authenticated contexts. middleBrick’s CLI can be used to validate these patterns by scanning endpoints and checking whether API key handling aligns with secure practices.