Phishing Api Keys in Echo Go with Bearer Tokens

Echo Go is a lightweight web framework for building HTTP services in Go. When Echo Go routes are configured to accept Bearer Tokens in the Authorization header, the risk of phishing those credentials increases if endpoints expose tokens through logging, misconfigured CORS, or insecure client-side storage. A phishing vector can arise when a developer embeds a static Bearer Token in client-side JavaScript or mobile app code, making it enumerable via source code review or network inspection. Attackers can craft socially engineered pages that trick users into executing requests that leak the token, especially when the same token is used across multiple services and lacks scope restrictions.

In an API security scan using middleBrick, the LLM/AI Security checks probe for System Prompt Leakage and Active Prompt Injection, but the framework-agnostic checks also surface risks when tokens appear in observable outputs or error messages. For example, if an Echo Go handler returns the Authorization header in a debug response, a phishing page can harvest the token by inducing the victim’s browser to make a request to the target API and capturing the response. This becomes critical when the Bearer Token grants access to sensitive endpoints without additional context-bound validation, enabling BOLA/IDOR or BFLA scenarios if the token is also weakly scoped.

Additionally, if the Echo Go service does not enforce strict Transport Layer Security and relies on unauthenticated endpoints for health checks, an attacker can intercept token exchanges in transit. The combination of predictable token formats, lack of rotating secrets, and verbose error messages that include token fragments creates a favorable environment for phishing campaigns. middleBrick’s Data Exposure and Encryption checks would flag such endpoints, while the Inventory Management and Unsafe Consumption checks can reveal endpoints that inadvertently echo tokens in logs or responses, providing actionable remediation guidance to reduce the attack surface.

Remediation focuses on avoiding static Bearer Tokens in client-facing code, enforcing short-lived tokens, and ensuring Echo Go handlers never expose sensitive headers. Below are concrete, working examples that demonstrate secure patterns.

package main

import (
    "net/http"
    "strings"

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

// Secure middleware that validates Bearer Tokens without echoing them
func secureBearerMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        auth := c.Request().Header.Get("Authorization")
        if auth == "" {
            return echo.NewHTTPError(http.StatusUnauthorized, "authorization header missing")
        }
        const bearerPrefix = "Bearer "
        if !strings.HasPrefix(auth, bearerPrefix) {
            return echo.NewHTTPError(http.StatusUnauthorized, "invalid authorization header format")
        }
        token := strings.TrimPrefix(auth, bearerPrefix)
        if token == "" {
            return echo.NewHTTPError(http.StatusUnauthorized, "token is empty")
        }
        // Validate token via introspection or JWKS; keep token out of logs
        if !isValidToken(token) {
            return echo.NewHTTPError(http.StatusForbidden, "invalid token")
        }
        // Ensure token is not reflected in any response headers or body
        c.Response().Header().Del("Authorization")
        return next(c)
    }
}

func isValidToken(token string) bool {
    // Implement token validation against an OAuth2 introspection endpoint or JWKS
    // This is a placeholder; do not log or echo the token
    return token == "expected-rotating-token-referenced-via-env"
}

func main() {
    e := echo.New()
    e.Use(middleware.RequestID())
    e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
        Format: "${status} ${method} ${path}",
        // Never include headers containing Authorization
        Headers: []string{"X-Request-ID"},
    }))
    e.Use(secureBearerMiddleware)

    e.GET("/profile", func(c echo.Context) error {
        // Safe: token is validated and not exposed
        return c.JSON(http.StatusOK, map[string]string{"status": "ok"})
    })

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

Key practices demonstrated:

• Do not concatenate or log the full Authorization header; strip it before any logging.
• Validate tokens server-side via introspection or JWKS; avoid embedding secrets in source or client bundles.
• Use environment variables for token references and rotate credentials regularly.
• Configure CORS strictly to limit origins and avoid wildcard allowances that facilitate phishing.

For teams using middleBrick, the Pro plan’s continuous monitoring can be configured to alert on endpoints that echo Authorization headers, while the GitHub Action can enforce a security score threshold before merging changes that might reintroduce token exposure. The MCP Server allows AI coding assistants to scan API definitions in your IDE, helping detect insecure patterns early in development.