Pii Leakage in Echo Go with Basic Auth

When an Echo Go service uses HTTP Basic Authentication and transmits credentials in cleartext, PII leakage can occur if responses or logs inadvertently expose sensitive user data. Basic Auth encodes credentials with Base64, which is easily reversible, and does not encrypt the payload. If the server returns user details—such as email, username, or role—in response bodies or headers without protection, a network observer or an SSRF-prone endpoint can capture this information.

Consider an Echo Go handler that authenticates via Basic Auth and then returns the current user profile:

package main

import (
    "net/http"
    "strings"

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

type UserProfile struct {
    Username string `json:"username"`
    Email    string `json:"email"`
    Role     string `json:"role"`
}

func main() {
    e := echo.New()
    e.Use(middleware.BasicAuth(func(username, password string, c echo.Context) (bool, error) {
        return username == "alice" && password == "secret123", nil
    }))

    e.GET("/profile", func(c echo.Context) error {
        // PII risk: returning sensitive user data in response
        profile := UserProfile{
            Username: "alice",
            Email:    "[email protected]",
            Role:     "admin",
        }
        return c.JSON(http.StatusOK, profile)
    })

    e.Start(":8080")
}

If an attacker can observe the network traffic—via a compromised proxy, insecure logging, or an SSRF endpoint that forwards requests to internal services—they can extract the Base64-encoded credentials and any PII returned in JSON. Even without decrypting the credentials, the response body itself contains PII (email, role) that should be protected. In addition, if the Basic Auth credentials are reused across services or stored in browser history, the exposure risk extends beyond the immediate API call.

middleBrick detects this category under Data Exposure and Input Validation checks during unauthenticated scans. It examines whether responses include PII such as email addresses, usernames, or identifiers in combination with authentication mechanisms like Basic Auth. Findings include severity ratings and remediation guidance mapped to frameworks such as OWASP API Top 10 and GDPR personal data handling expectations.

To reduce PII leakage risk with Basic Auth in Echo Go, avoid returning sensitive user data in responses unless strictly necessary, and always enforce transport encryption. Use middleware to validate authorization scope and minimize data exposure in logs.

1. Avoid returning PII in responses

Return only necessary fields. If you must return user data, exclude sensitive attributes or provide a minimal representation:

package main

import (
    "net/http"

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

type MinimalProfile struct {
    Username string `json:"username"`
    // Email and Role omitted to reduce PII exposure
}

func main() {
    e := echo.New()
    e.Use(middleware.BasicAuth(func(username, password string, c echo.Context) (bool, error) {
        return username == "alice" && password == "secret123", nil
    }))

    e.GET("/profile", func(c echo.Context) error {
        profile := MinimalProfile{
            Username: "alice",
        }
        return c.JSON(http.StatusOK, profile)
    })

    e.Start(":8080")
}

2. Enforce HTTPS to protect credentials and data in transit

Basic Auth credentials are only as strong as the transport. Configure Echo to reject cleartext HTTP or redirect to HTTPS:

package main

import (
    "net/http"

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

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

    // Redirect HTTP to HTTPS
    go func() {
        http.ListenAndServe(":80", middleware.HTTPSRedirect())
    }()

    e.Use(middleware.BasicAuth(func(username, password string, c echo.Context) (bool, error) {
        return username == "alice" && password == "secret123", nil
    }))

    e.GET("/secure", func(c echo.Context) error {
        return c.String(http.StatusOK, "OK")
    })

    e.StartTLS(":443", "cert.pem", "key.pem")
}

3. Sanitize logs and error messages

Ensure middleware and handlers do not log full request headers or credentials. Customize the Basic Auth middleware behavior to avoid echoing sensitive values:

package main

import (
    "net/http"

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

func main() {
    e := echo.New()
    e.Use(middleware.BasicAuthWithConfig(middleware.BasicAuthConfig{
        Skipper: nil,
        Validator: func(username, password string, c echo.Context) (bool, error) {
            return username == "alice" && password == "secret123", nil
        },
        // Avoid logging credentials by not using default debug handlers
    }))

    e.GET("/data", func(c echo.Context) error {
        return c.String(http.StatusOK, "authenticated")
    })

    e.Start(":8080")
}

middleBrick’s CLI can be used to verify these changes by scanning the endpoint with middlebrick scan <url> and reviewing the Data Exposure and Authentication findings. The Pro plan supports continuous monitoring so that regressions in authentication handling are flagged early, while the GitHub Action can fail builds if risk scores drop below your defined threshold.