Api Key Exposure in Echo Go with Bearer Tokens

Echo Go is a lightweight HTTP framework commonly used to build RESTful services. When API keys are passed via Bearer Tokens in the Authorization header, the framework’s default routing and middleware setup can inadvertently expose those keys if security controls are incomplete. The risk typically arises when routes intended for internal or authenticated use are accessible without proper access enforcement, allowing unauthenticated or low-privilege callers to reach endpoints that return or reflect tokens.

One common pattern in Echo Go is to set the Authorization header on outgoing requests to downstream services using Bearer Tokens. If the service also exposes an endpoint that echoes or logs that header without validation, an attacker can probe unauthenticated paths to retrieve the token. For example, a route like /debug/headers that returns request headers in the response can disclose the Authorization header if access control is missing. This becomes a chain where the Bearer Token is both used as a credential and unintentionally surfaced.

Additionally, misconfigured route-level middleware can fail to enforce authentication for selected paths. In Echo Go, groups of routes can be assigned middleware stacks; if a Bearer Token validation middleware is applied inconsistently—such as being omitted from a route group or applied after a public route—an attacker can bypass authorization and interact with endpoints that expose token-related logic. This misalignment is especially risky when OpenAPI specs are generated automatically and do not accurately reflect which endpoints require authentication.

Another exposure vector involves error messages and logging. Echo Go applications that include the Authorization header in detailed error responses or logs can leak Bearer Tokens through stack traces or application logs that are accessible to unauthorized users. If the service does not scrub sensitive headers before logging, a simple unauthenticated request to a misbehaving endpoint can reveal active credentials.

Because Echo Go does not enforce authentication by default, developers must explicitly apply middleware and route guards. The combination of Bearer Tokens and inconsistent middleware application means that an attacker can perform unauthenticated probing against the public attack surface and potentially discover tokens through reflection, logging, or incomplete route protection. This aligns with BOLA/IDOR and Unsafe Consumption checks in middleBrick, which flag endpoints that expose sensitive headers or lack proper authorization.

Remediation focuses on ensuring Bearer Tokens are never reflected, logged, or accessible without proper authorization. The following patterns demonstrate secure handling in Echo Go.

1. Enforce authentication middleware on all relevant routes

Apply an authentication middleware that validates Bearer Tokens for protected routes. Do not omit middleware on any route that handles sensitive operations.

// main.go
package main

import (
    "net/http"
    "github.com/labstack/echo/v4"
    "github.com/labstack/echo/v4/middleware"
)

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

    // Middleware to validate Bearer Token
    bearerAuth := middleware.JWTWithConfig(middleware.JWTConfig{
        SigningKey:    []byte("your-secret-key"),
        AuthScheme:    "Bearer",
        TokenLookup:   "header:Authorization",
        ValidateFunc: func(token *jwt.Token) (interface{}, error) {
            // Validate token via your auth provider
            return []byte("secret"), nil
        },
    })

    // Public route (no auth required)
    e.GET("/public", func(c echo.Context) error {
        return c.String(http.StatusOK, "public data")
    })

    // Protected group with Bearer auth
    protected := e.Group("/api")
    protected.Use(bearerAuth)
    {
        protected.GET("/data", func(c echo.Context) error {
            return c.JSON(http.StatusOK, map[string]string{"message": "authorized"})
        })
    }

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

2. Avoid returning or logging Authorization headers

Ensure handlers and middleware do not echo or log the Authorization header. Sanitize logs and responses to remove sensitive values.

// safe_handler.go
package main

import (
    "net/http"
    "github.com/labstack/echo/v4"
)

func safeHandler(c echo.Context) error {
    // Explicitly avoid using c.Request().Header.Get("Authorization") in responses
    // If logging is necessary, redact the token
    auth := c.Request().Header.Get("Authorization")
    if auth != "" {
        // Redact before any logging
        c.Logger().Infof("request received, auth header: [REDACTED]")
    }
    return c.JSON(http.StatusOK, map[string]string{"status": "ok"})
}

3. Validate token scope and audience to prevent misuse

When using JWT-based Bearer Tokens, validate claims such as scope and audience to ensure tokens are used only for intended purposes within the Echo Go service.

// jwt_validate.go
package main

import (
    "github.com/golang-jwt/jwt/v5"
    "github.com/labstack/echo/v4/middleware"
)

func validateToken(token *jwt.Token) (interface{}, error) {
    // Verify signing method
    if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
        return nil, jwt.ErrSignatureInvalid
    }
    // Validate custom claims
    claims, ok := token.Claims.(jwt.MapClaims)
    if !ok || !claims.VerifyIssuer("https://api.example.com", true) {
        return nil, jwt.ErrTokenInvalid
    }
    if !claims.VerifyAudience("echo-go-service", true) {
        return nil, jwt.ErrTokenInvalid
    }
    return []byte("your-secret-key"), nil
}

func main() {
    e := echo.New()
    e.Use(middleware.JWTWithConfig(middleware.JWTConfig{
        SigningKey:  []byte("your-secret-key"),
        AuthScheme:  "Bearer",
        TokenLookup: "header:Authorization",
        ValidateFunc: validateToken,
    }))
    // routes...
}

4. Secure OpenAPI generation to reflect correct auth requirements

When generating OpenAPI specs for Echo Go services, ensure that security schemes explicitly require Bearer Tokens for protected endpoints and that unauthenticated paths are correctly marked as public.

// openapi_config.go
package main

import (
    "github.com/labstack/echo/v4"
    "github.com/swaggo/swag"
)

// @title Secure Echo API
// @version 1.0
// @description API with proper Bearer Token requirements
// @securityDefinitions.bearer ApiKeyAuth
// @in header
// @name Authorization
func init() {
    swag.SetHost("localhost:8080")
    swag.SetBasePath("/")
}