Memory Leak in Fiber with Basic Auth

A memory leak in a Fiber application using HTTP Basic Authentication can occur when request-scoped objects are retained beyond the request lifecycle. In Go, the Fiber framework provides a fast, low-level HTTP server; however, developers must manage object lifetimes carefully. When Basic Auth credentials are parsed on each request, middleware or handlers might inadvertently cache or hold references to request context, buffers, or parsed credential structures. For example, storing a pointer to a request-specific auth state in a global map without cleanup prevents the garbage collector from reclaiming memory, causing a gradual increase in heap usage over time.

In a black-box scan using middleBrick, unauthenticated testing can detect indicators such as steadily increasing memory usage under repeated requests with the Authorization header present. One of the 12 parallel security checks, Property Authorization, examines whether access controls are consistently enforced; if auth state is stored beyond a request, it may indicate insecure handling of authentication context. Additionally, Input Validation checks can surface issues where malformed or repeated Basic Auth headers lead to allocations that are never freed. Because Basic Auth sends credentials on each request, high-traffic endpoints that parse auth in middleware become hotspots for leaks if context objects are pooled or reused incorrectly.

Real-world patterns that exacerbate this include attaching user identity derived from Basic Auth to request context and failing to clean up associated resources, such as database connections or large buffers. For instance, if a handler decodes base64 credentials and stores intermediate byte slices in a session-like structure without expiration, memory pressure grows. Another scenario involves middleware that logs auth details into a long-lived slice or map keyed by request ID, where keys are never evicted. These patterns align with findings that map to compliance frameworks like OWASP API Top 10 (2023) A03:2021 — Injection and A05:2021 — Security Misconfiguration when resource management is inconsistent.

middleBrick’s OpenAPI/Swagger spec analysis, supporting full $ref resolution, can highlight endpoints with authentication schemes defined but without clear session management guidance, prompting a deeper runtime review. When scans reveal a Memory Leak in combination with Basic Auth, the output includes prioritized findings with severity and remediation guidance, helping teams correlate design decisions with runtime behavior. Note that middleBrick detects and reports these conditions without fixing them; it provides actionable guidance so developers can address the root cause.

To prevent memory leaks when using Basic Auth in Fiber, ensure that per-request data is not stored beyond the request lifecycle and that allocations are minimized. Use Fiber’s context-local storage carefully and prefer stack-allocated structures where possible. Below are concrete code examples that demonstrate secure handling of Basic Auth without retaining references.

First, a safe middleware that parses credentials each request and cleans up after the request finishes:

package main

import (
	"encoding/base64"
	"strings"

	"github.com/gofiber/fiber/v2"
)

func basicAuthMiddleware() fiber.Handler {
	return func(c *fiber.Ctx) error {
		auth := c.Get(fiber.HeaderAuthorization)
		if len(auth) == 0 || !strings.HasPrefix(auth, "Basic ") {
			return c.SendStatus(fiber.StatusUnauthorized)
		}
		payload, err := base64.StdEncoding.DecodeString(auth[7:])
		if err != nil {
			return c.SendStatus(fiber.StatusBadRequest)
		}
		// Do not store payload or parsed credentials globally
		parts := strings.SplitN(string(payload), ":", 2)
		if len(parts) != 2 {
			return c.SendStatus(fiber.StatusUnauthorized)
		}
		username, password := parts[0], parts[1]
		// Validate credentials here (e.g., against a secure store)
		_ = username
		_ = password
		return c.Next()
	}
}

func main() {
	app := fiber.New()
	app.Use(basicAuthMiddleware())
	app.Get("/secure", func(c *fiber.Ctx) error {
		return c.SendString("Authenticated")
	})
	app.Listen(":3000")
}

This example avoids global caches and processes credentials within the request scope. The variables username and password are scoped to the middleware invocation and released after the request ends, reducing pressure on the garbage collector.

Second, if you need to pass user identity downstream, use context values with a clear cleanup strategy. Fiber’s context can carry values safely as long as you do not attach long-lived objects:

package main

import (
	"context"
	"encoding/base64"
	"strings"

	"github.com/gofiber/fiber/v2"
)

func authWithCtx() fiber.Handler {
	return func(c *fiber.Ctx) error {
		auth := c.Get(fiber.HeaderAuthorization)
		if len(auth) < 8 || auth[:6] != "Basic " {
			return c.SendStatus(fiber.StatusUnauthorized)
		}
		payload, err := base64.StdEncoding.DecodeString(auth[7:])
		if err != nil {
			return c.SendStatus(fiber.StatusBadRequest)
		}
		parts := strings.SplitN(string(payload), ":", 2)
		if len(parts) != 2 {
			return c.SendStatus(fiber.StatusUnauthorized)
		}
		c.Locals("user", parts[0]) // Store only lightweight data
		defer func() {
			// Ensure cleanup if needed; Fiber’s context is per-request
		}()
		return c.Next()
	}
}

By storing only a username string via Locals and avoiding global maps, you minimize the risk of retention. middleBrick’s scans can verify that endpoints with Basic Auth do not exhibit anomalies in memory behavior, and its GitHub Action can integrate these checks into CI/CD to fail builds if regression risks are detected.