Token Leakage in Echo Go with Basic Auth

Token leakage in an Echo Go service using HTTP Basic Authentication occurs when authentication tokens, session identifiers, or other bearer credentials are inadvertently exposed through logs, error messages, headers, or response bodies. Basic Auth encodes credentials with Base64 but does not encrypt them; therefore, any additional token carried in headers or cookies can be disclosed if the application mishandles them.

In Echo Go, a common pattern is to use middleware that extracts a token from the Authorization header (after Basic Auth validation) and stores it in a request-scoped context or attaches it to downstream HTTP requests. If the application logs the incoming Authorization header verbatim or includes request context in error responses, a token can be exposed in server logs or to an attacker who can read error pages. For example, if a developer logs req.Header.Get("Authorization") without redacting the token portion, any observer with access to logs can harvest credentials or session tokens.

Another leakage vector arises when Echo Go services proxy requests to upstream APIs and forward the same Authorization header without stripping or transforming it. A token embedded in headers may be reflected in upstream logs or returned in error responses from those services. Additionally, misconfigured CORS or verbose HTTP debug handlers can echo back headers, including authorization tokens, to the client. Middleware that sets security headers incorrectly or fails to clear sensitive headers from copied requests can also contribute to inadvertent exposure.

The combination of Basic Auth and token-based authorization increases risk because developers may assume that Base64 encoding provides confidentiality. In practice, the token must be protected at every stage: ingress logging, request context propagation, error handling, and outbound proxying. Without strict header sanitization and context isolation, an attacker who can observe logs, error pages, or network traffic may recover both the Basic Auth credentials and the associated token, leading to account compromise or privilege escalation.

Remediation focuses on preventing the logging and propagation of sensitive headers, isolating token handling from Basic Auth validation, and ensuring error responses do not disclose tokens. The following examples demonstrate secure patterns in Echo Go.

• Validate Basic Auth without logging raw credentials

//go
package main

import (
	"net/http"
	"strings"

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

// BasicAuthValidator extracts and validates credentials without logging them.
func BasicAuthValidator(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		auth := c.Request().Header.Get("Authorization")
		if auth == "" {
			return echo.ErrUnauthorized
		}
		const prefix = "Basic "
		if !strings.HasPrefix(auth, prefix) {
			return echo.ErrUnauthorized
		}
		// Decode and validate credentials (omitted for brevity).
		// Do NOT log the full auth header.
		// Perform validation and set user identity in context.
		c.Set("user", "authenticated-user")
		return next(c)
	}
}

func main() {
	e := echo.New()
	e.Use(BasicAuthValidator)
	e.GET("/secure", func(c echo.Context) error {
		return c.String(http.StatusOK, "OK")
	})
	e.Logger.Fatal(e.Start(":8080"))
}

• Strip sensitive headers before proxying or logging

//go
package main

import (
	"net/http"
	"strings"

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

// SecureProxy middleware removes or replaces sensitive headers before forwarding.
func SecureProxy(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		// Remove or overwrite Authorization to avoid leaking tokens.
		req := c.Request()
		if auth := req.Header.Get("Authorization"); auth != "" {
			// Keep Basic Auth for the upstream call if required, otherwise replace with a token.
			req.Header.Set("Authorization", "Bearer REDACTED")
		}
		// Ensure no debug or custom headers echo back tokens.
		req.Header.Del("X-Debug-Token")
		return next(c)
	}
}

func main() {
	e := echo.New()
	e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
		// Customize log format to exclude Authorization.
		Format: "time=${time} uri=${uri} status=${status} latency=${latency}
",
	}))
	e.Use(SecureProxy)
	e.GET("/proxy", func(c echo.Context) error {
		// Proxy logic here; sensitive headers are already sanitized.
		return c.String(http.StatusOK, "Proxied")
	})
	e.Logger.Fatal(e.Start(":8080"))
}

• Return safe error responses and enforce security headers

//go
package main

import (
	"net/http"

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

func main() {
	e := echo.New()
	// Prevent verbose debug output that may include headers.
	e.HTTPErrorHandler = func(err error, c echo.Context) {
		// Do not include request headers in the response body.
		c.JSON(http.StatusInternalServerError, map[string]string{
			"error": "internal server error",
		})
	}
	e.Use(middleware.SecureWithConfig(middleware.SecureConfig{
		XSSProtection:                "1; mode=block",
		ContentTypeNosniff:          "nosniff",
		XFrameOptions:               "DENY",
		HSTSMaxAge:                  31536000,
		HSTSExcludeSubdomains:       false,
		HSTSPreload:                 false,
		SSLRedirect:                 false,
		SSLHost:                     "",
		SSLProxyHeaders:               nil,
		StatusFuncRedirect:          nil,
		IsDevelopment:               false,
	}))
	e.GET("/safe", func(c echo.Context) error {
		return c.String(http.StatusOK, "OK")
	})
	e.Logger.Fatal(e.Start(":8080"))
}