Man In The Middle in Buffalo with Basic Auth

When a Buffalo application uses HTTP Basic Authentication over unencrypted HTTP, a Man In The Middle (MitM) can intercept and abuse credentials. Basic Auth encodes the username and password with Base64, which is trivial to decode; if the transport is not authenticated and encrypted via TLS, an attacker on the same network can observe the Authorization header and reuse it to impersonate the client.

In Buffalo, routes that rely on beforeAction or custom authentication logic may call req.BasicAuth() to extract credentials. If the request was made over HTTP, the header is present in plaintext in the wire traffic, and there is no transport-layer protection to prevent interception. An attacker performing ARP spoofing or operating on an open Wi‑Fi network can capture the requests, extract the Base64 string, and replay it to access protected endpoints.

Buffalo’s typical pattern uses a before action to validate credentials on each request. For example:

func app() *buffalo.App {
    app := buffalo.New(buffalo.Options{
        Env:         ENV,
        SessionStore: &middleware.NullSessionStore{},
    })
    app.Use(middleware.ParameterParser)
    app.Use(middleware.Session)
    app.Use(middleware.Flash)

    // Example unprotected API route
    app.GET("/api/values", func(c buffalo.Context) error {
        user, pass, ok := c.Request().BasicAuth()
        if !ok || !validate(user, pass) {
            c.Response().Header().Set("WWW-Authenticate", `Basic realm="restricted", charset="UTF-8"`)
            return c.Render(401, r.JSON(H{"error": "unauthorized"}))
        }
        return c.Render(200, r.JSON(H{"data": "protected"}))
    })
    return app
}

If this endpoint is served over HTTP, an attacker observing the traffic can extract the Base64 credentials and replay them in a crafted curl request, bypassing network-level protections. Additionally, if the application redirects from HTTP to HTTP (or uses a mixed-content site where some pages are served over HTTPS and others not), the credentials may be exposed inconsistently. The lack of TLS means there is no server authentication, enabling a straightforward MitM where the attacker can alter responses or inject malicious content without detection.

Even when the application sets the WWW-Authenticate header correctly, without TLS the protection is purely nominal. Basic Auth over HTTP should never be considered secure; the combination inherently exposes credentials to anyone capable of observing the network path. Attack patterns such as session hijacking via credential replay fall under the broader OWASP API Top 10 risk of Broken Object Level Authorization (BOLA) when access tokens or session identifiers are similarly exposed.

To assess this risk with middleBrick, the scanner runs unauthenticated checks that detect whether authentication mechanisms like Basic Auth are exposed over non-TLS channels and whether protections such as HSTS are absent. Findings include severity ratings and remediation guidance mapped to frameworks like OWASP API Top 10 and PCI-DSS, helping teams understand the exposure without implying automatic remediation.

Remediation centers on enforcing transport encryption with TLS and avoiding reliance on Basic Auth over insecure channels. In Buffalo, you should ensure all routes are served over HTTPS and that the application redirects HTTP to HTTPS before any authentication logic runs.

First, configure your server to use TLS. When initializing your Buffalo app, use buffalo.New with appropriate options and ensure your front-end load balancer or reverse proxy terminates TLS. Then enforce HTTPS in middleware:

func app() *buffalo.App {
    app := buffalo.New(buffalo.Options{
        Env: ENV,
    })
    app.Use(middleware.Secure)
    app.Use(forceHTTPS)
    app.Use(middleware.ParameterParser)
    app.Use(middleware.Session)
    return app
}

func forceHTTPS(next buffalo.Handler) buffalo.Handler {
    return func(c buffalo.Context) error {
        if c.Request().TLS == nil {
            url := "https://" + c.Request().Host + c.Request().RequestURI
            http.Redirect(c.Response(), c.Request(), url, http.StatusMovedPermanently)
            return nil
        }
        return next(c)
    }
}

Second, require TLS for all routes by using the Secure middleware and setting security headers. The Secure middleware can include HSTS, which instructs browsers to only use HTTPS for future requests:

app.Use(middleware.Secure)
// Optionally customize HSTS:
// app.Secure().STSSeconds = 31536000
// app.Secure().STSIncludeSubdomains = true
// app.Secure().STSPreload = true

Third, avoid sending credentials in the Authorization header over HTTP entirely. If you must support Basic Auth for compatibility, ensure the client always uses HTTPS. In client code (e.g., curl or HTTP clients), always use https:// URLs and never fall back to HTTP:

# Example: always use HTTPS with Basic Auth
curl --user user:password https://api.example.com/endpoint

Within Buffalo, you can also rotate or scope credentials to reduce reuse risk, but the primary fix is eliminating cleartext transmission. Combine TLS enforcement with content security policies and strict transport security headers to mitigate interception and replay. middleBrick’s scans can verify that endpoints requiring authentication are served over TLS and that HSTS is present, providing findings and remediation steps aligned with compliance frameworks.