Broken Authentication in Buffalo with Bearer Tokens

Broken Authentication in the Buffalo framework when using Bearer Tokens typically arises from weak token handling and insufficient validation, which expands the unauthenticated attack surface that middleBrick tests. Even without credentials, a black-box scan can detect whether token issuance, transmission, or validation is insecure.

One common pattern is generating tokens without sufficient entropy or without tying them to a specific scope or audience. If a Buffalo application embeds a Bearer Token in URLs, logs, or error messages, a scan can discover tokens through response leakage or timing differences. For example, a route that returns an Authorization header value in JSON can expose tokens to anyone who can trigger the endpoint:

package controllers

import (
    "github.com/gobuffalo/buffalo"
    "net/http"
)

func showToken(c buffalo.Context) error {
    token := c.Request().Header.Get("Authorization")
    if len(token) == 0 {
        c.Response().WriteHeader(http.StatusUnauthorized)
        return c.Render(401, r.JSON(map[string]string{"error": "missing token"}))
    }
    // Unsafe: returns the token in the response
    return c.Render(200, r.JSON(map[string]string{"token": token}))
}

Another vulnerability arises when token validation is performed inconsistently across routes. If some endpoints verify the signature and expiration while others skip checks, an attacker can pivot to less-protected endpoints. Buffalo applications that use multiple subdomains or wildcard routes must ensure token validation is applied uniformly; otherwise, BOLA/IDOR and BFLA risks increase because access controls become route-dependent rather than token-dependent.

CSRF and session fixation concerns also intersect with Bearer Tokens when Buffalo apps mix cookie-based sessions with token-based auth. If a token is stored in a cookie without the HttpOnly and Secure flags, or if the SameSite attribute is missing, an attacker can leverage cross-site requests to obtain or replay tokens. middleBrick tests for these combinations by probing unauthenticated endpoints and inspecting response headers and cookies for insecure attributes.

Additionally, token revocation and rotation are often under-implemented. Without a mechanism to invalidate compromised tokens, stolen Bearer Tokens remain valid until expiry, which may be set far in the future. middleBrick’s checks for authentication and authorization assess whether token validation includes scope, audience, and issuer checks, and whether tokens are bound to a specific context to reduce replay and privilege escalation risks.

Finally, insecure transport exacerbates the issue. If a Buffalo app serves endpoints over HTTP or uses weak TLS configurations, Bearer Tokens can be intercepted. middleBrick scans for encryption and transport weaknesses, flagging endpoints that accept tokens without enforcing HTTPS, thereby exposing credentials in transit.

Remediation focuses on secure token generation, transmission, storage, and validation within the Buffalo framework. Follow these practices to reduce the attack surface that middleBrick evaluates.

• Generate tokens with high entropy and include claims for audience, issuer, and scope:

package auth

import (
    "github.com/gobuffalo/buffalo"
    "github.com/golang-jwt/jwt/v5"
    "time"
)

func GenerateToken(userID string) (string, error) {
    token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
        "sub":   userID,
        "iss":   "myapp-buffalo",
        "aud":   "api.myapp.com",
        "scope": "read write",
        "exp":   time.Now().Add(time.Hour * 24).Unix(),
        "nbf":   time.Now().Unix(),
        "iat":   time.Now().Unix(),
        "jti":   "unique-identifier-here",
    })
    return token.SignedString([]byte("your-256-bit-secret"))
}

• Validate tokens on every protected route and reject malformed or unsigned tokens:

package middleware

import (
    "github.com/gobuffalo/buffalo"
    "github.com/golang-jwt/jwt/v5"
    "net/http"
)

func ValidateToken(next buffalo.Handler) buffalo.Handler {
    return func(c buffalo.Context) error {
        auth := c.Request().Header.Get("Authorization")
        if auth == "" {
            return c.Render(http.StatusUnauthorized, r.JSON(map[string]string{"error": "authorization header required"}))
        }
        tokenString := auth[len("Bearer "):]
        claims := jwt.MapClaims{}
        token, err := jwt.ParseWithClaims(tokenString, claims, func(token *jwt.Token) (interface{}, error) {
            return []byte("your-256-bit-secret"), nil
        })
        if err != nil || !token.Valid {
            return c.Render(http.StatusUnauthorized, r.JSON(map[string]string{"error": "invalid token"}))
        }
        c.Set("claims", claims)
        return next(c)
    }
}

• Ensure tokens are transmitted only over HTTPS and set secure cookie attributes when storing tokens client-side:

package actions

import (
    "github.com/gobuffalo/buffalo"
    "github.com/gobuffalo/buffalo/middleware"
)

func App() *buffalo.App {
    app := buffalo.New(buffalo.Options{
        Env:         ENV,
        SessionStore: &middlebury.Memstore{},
        PreWares: []buffalo.PreWare{
            middleware.ParameterLogger,
            middleware.CSRF,
            middleware.Secure,
        },
    })
    app.GET("/dashboard", ValidateToken(dashboardHandler), func(c buffalo.Context) error {
        return c.Render(200, r.JSON(map[string]string{"status": "secure"}))
    })
    return app
}

• Avoid including tokens in logs or URLs. Use request-scoped context instead of global or session variables that might be exposed:

package controllers

import (
    "github.com/gobuffalo/buffalo"
    "net/http"
)

func safeHandler(c buffalo.Context) error {
    claims, ok := c.Get("claims").(map[string]interface{})
    if !ok {
        return c.Render(http.StatusInternalServerError, r.JSON(map[string]string{"error": "invalid context"}))
    }
    // Do not log or echo the token
    return c.Render(200, r.JSON(map[string]interface{}{"user": claims["sub"]}))
}

• Implement token revocation and short-lived access tokens with refresh token rotation, storing refresh tokens server-side with strict binding to user and client metadata.