Memory Leak in Echo Go with Basic Auth

A memory leak in an Echo Go service using HTTP Basic Authentication can occur when request-scoped objects are retained beyond the request lifecycle. In Go, memory that is still referenced cannot be garbage collected. When Basic Auth middleware is added to an Echo instance, it typically parses credentials from the Authorization header and attaches user context to the request. If the application or middleware stores references to request-specific data—such as large buffers, parsed tokens, or context values—in global or long-lived structures, those references prevent garbage collection and cause the process memory footprint to grow over time.

With Basic Auth, each request carries credentials in a header. If the server logs or retains the raw header, copies the username or password into a global cache, or binds them to long-lived structs without cleanup, the associated memory persists. For example, attaching user info to the context without cleaning up derived values or failing to limit per-request buffers when processing uploaded content can accumulate allocations. This pattern becomes more pronounced under sustained load, where many authenticated requests allocate similar objects that are never released.

The interaction with Echo is important: Echo’s default context pool and reuse can reduce allocations, but if handlers or middleware introduce new references—such as storing parsed credentials in a map keyed by username for “session-like” tracking without eviction—they defeat the pool’s benefits. An OpenAPI/Swagger spec analyzed by middleBrick may reveal endpoints with Basic Auth security schemes; runtime findings can then highlight unusual memory-related behaviors like high allocation rates or spikes in heap objects, consistent with patterns seen in SSRF or unsafe consumption issues that indirectly stress memory through unexpected payloads.

In black-box scanning, middleBrick runs 12 security checks in parallel. While it does not profile memory, findings related to Input Validation, Unsafe Consumption, and Property Authorization can indicate request paths that may exacerbate retention issues. For instance, large file uploads with Basic Auth that are not streamed or bounded can cause buffers to accumulate. Remediation guidance provided by the scan will point to refactoring handler logic and ensuring middleware cleans up context and buffers promptly.

To prevent memory retention with Basic Auth in Echo, ensure credentials are used transiently and no global or long-lived caches hold request-scident data. Use context values sparingly and clean up any derived objects. Below are concrete, working examples that demonstrate secure handling.

Example 1: Minimal, non-retaining Basic Auth middleware

package main

import (
	"encoding/base64"
	"net/http"
	"strings"

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

// BasicAuthMiddleware validates credentials per request without storing them.
func BasicAuthMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		auth := c.Request().Header.Get(echo.HeaderAuthorization)
		if auth == "" {
			return echo.ErrUnauthorized
		}
		scheme, token, ok := strings.Cut(auth, " ")
		if !ok || strings.ToLower(scheme) != "basic" {
			return echo.ErrUnauthorized
		}
		decoded, err := base64.StdEncoding.DecodeString(token)
		if err != nil {
			return echo.ErrUnauthorized
		}
		creds := strings.SplitN(string(decoded), ":", 2)
		if len(creds) != 2 || !valid(creds[0], creds[1]) {
			return echo.ErrUnauthorized
		}
		// Use credentials only for this request; do not attach to context unless necessary.
		if err := next(c); err != nil {
			c.Error(err)
		}
		return nil
	}
}

func valid(username, password string) bool {
	// Replace with secure lookup (e.g., constant-time compare against a store).
	return username == "admin" && password == "s3cr3t"
}

func handler(c echo.Context) error {
	return c.String(http.StatusOK, "ok")
}

func main() {
	e := echo.New()
	e.Use(BasicAuthMiddleware)
	e.GET("/", handler)
	e.Start(":8080")
}

Example 2: Avoiding context pollution and cleanup

package main

import (
	"context"
	"net/http"

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

// Key type to avoid stringly-typed context keys.
type contextKey string

const userKey contextKey = "user"

// Handler that attaches user data temporarily and ensures no retention.
func handler(c echo.Context) error {
	// Perform auth in middleware; attach only lightweight, request-scoped data.
	user := c.Get("user") // Set by middleware after validation.
	if user == nil {
		return echo.ErrUnauthorized
	}
	// Use user value for this request only; do not store in globals.
	_ = user
	return c.String(http.StatusOK, "authenticated")
}

// Middleware that cleans up after request.
func authMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		// Parse and validate auth.
		// ...
		c.Set("user", username) // Lightweight value, e.g., username string.
		defer func() {
			// Explicit cleanup is often unnecessary because Echo recycles context,
			// but removing the key can help in long-lived contexts if needed.
			c.Set("user", nil)
		}()
		return next(c)
	}
}

func main() {
	e := echo.New()
	e.Use(authMiddleware)
	e.GET("/secure", handler)
	e.Start(":8080")
}

Key remediation practices

• Do not store credentials or parsed user data in global variables or long-lived caches.
• Limit the scope of context values and clear them when no longer needed, using defer if necessary.
• Stream and bound large payloads to avoid unbounded buffer growth, even when authenticated.
• Use middleware to validate Basic Auth per request and avoid side effects that retain memory.

These fixes address the specific combination by removing long-term references tied to authenticated requests, ensuring that Echo’s context reuse does not contribute to retention. By focusing on transient use and cleanup, the service reduces the risk of gradual memory growth while maintaining Basic Authentication security.