Information Disclosure in Echo Go with Basic Auth

Echo Go is a lightweight HTTP framework commonly used to build APIs. When Basic Authentication is implemented naively in Echo Go, it can contribute to information disclosure by exposing whether a given path is protected and by mishandling credentials in logs or error messages. Basic Auth transmits credentials in an Authorization header encoded with Base64, which is easily reversible; if the server responds differently depending on whether credentials are present or valid, an attacker can infer the existence of protected endpoints without needing valid credentials.

In Echo Go, a common pattern is to use middleware that checks the Authorization header and returns 401 or 403 based on the result. If the server returns a detailed error for missing authentication (e.g., “missing credentials”) but a different error for malformed credentials (e.g., “invalid username or password”), this behavioral difference leaks information about authentication state. Additionally, if the Echo Go server includes headers such as WWW-Authenticate: Basic realm="api" on every response for a protected route—even when the route does not require authentication in some configurations—it can signal the presence of protected resources to unauthenticated scanners. Information disclosure can also occur through server or framework version headers, verbose error pages, or debug routes that expose stack traces containing usernames or internal paths. These side channels allow an attacker to map the API surface and craft targeted credential-stuffing or phishing campaigns.

The standard library used by Echo Go does not inherently leak credentials, but developer practices can cause unsafe exposure. For example, logging the Authorization header in access logs—whether for debugging or observability—results in credentials being stored in plaintext or in easily parsed log files. If log aggregation systems or error-tracking services are accessible to unauthorized parties, this becomes an additional vector for information disclosure. Furthermore, if the Echo Go application returns the full path or internal handler names in error responses, an attacker gains insight into the application structure, which can be correlated with other findings to escalate risk. Properly configured middleware should normalize responses for authentication failures, avoid logging sensitive headers, and ensure that server headers do not reveal framework or application internals.

Remediation focuses on consistent error handling, secure credential handling, and minimizing information leakage through headers and logs. Use standard HTTP status codes without exposing details in the response body. Ensure that the same generic 401 response is returned for missing or invalid credentials, and avoid including hints about whether a username exists. Do not include WWW-Authenticate headers on routes that do not require authentication, and avoid verbose error messages that disclose stack traces or internal paths.

Below are concrete, syntactically correct examples of Basic Auth middleware in Echo Go that implement safe practices.

Example 1: Minimal, consistent Basic Auth middleware

package main

import (
    "net/http"
    "strings"

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

func basicAuthMiddleware(realm string, validUser, validPass string) echo.MiddlewareFunc {
    return func(next echo.HandlerFunc) echo.HandlerFunc {
        return func(c echo.Context) error {
            auth := c.Request().Header.Get("Authorization")
            if auth == "" {
                return c.NoContent(http.StatusUnauthorized)
            }
            const prefix = "Basic "
            if !strings.HasPrefix(auth, prefix) {
                return c.NoContent(http.StatusUnauthorized)
            }
            payload, err := base64.StdEncoding.DecodeString(auth[len(prefix):])
            if err != nil {
                return c.NoContent(http.StatusUnauthorized)
            }
            parts := strings.SplitN(string(payload), ":", 2)
            if len(parts) != 2 {
                return c.NoContent(http.StatusUnauthorized)
            }
            user, pass := parts[0], parts[1]
            if user != validUser || pass != validPass {
                return c.NoContent(http.StatusUnauthorized)
            }
            return next(c)
        }
    }
}

func main() {
    e := echo.New()
    e.Use(basicAuthMiddleware("api", "admin", "s3cr3t"))
    e.GET("/health", func(c echo.Context) error {
        return c.String(http.StatusOK, "ok")
    })
    e.Logger.Fatal(e.Start(":8080"))
}

Example 2: Middleware that avoids logging sensitive headers

package main

import (
    "net/http"
    "strings"

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

func secureLogger(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        // Ensure Authorization header is not captured by the default logger
        auth := c.Request().Header.Get("Authorization")
        if auth != "" {
            // Redact or omit the header from any request-scoped logging
            c.Request().Header.Del("Authorization")
            defer func() { c.Request().Header.Set("Authorization", auth) }()
        }
        return next(c)
    }
}

func main() {
    e := echo.New()
    e.Pre(middleware.RemoveHeader(echo.HeaderServer))
    e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
        Format: "method=${method}, uri=${uri}, status=${status}", // do not include headers
    }))
    e.Use(secureLogger)
    e.Use(basicAuthMiddleware("api", "admin", "s3cr3t"))
    e.GET("/secure", func(c echo.Context) error {
        return c.String(http.StatusOK, "protected")
    })
    e.Logger.Fatal(e.Start(":8080"))
}

Additional remediation steps include rotating credentials regularly, using HTTPS to prevent interception of the Base64-encoded credentials, and integrating these checks into the CI/CD pipeline. The middleBrick CLI can be used to scan your Echo Go endpoints for information disclosure patterns and authentication misconfigurations. With the Pro plan, continuous monitoring can alert you when inconsistent error responses or unsafe headers are detected, and the GitHub Action can fail builds if risk thresholds are exceeded.