Password Spraying in Buffalo

Password spraying attacks target authentication endpoints by attempting a small set of common passwords across many usernames, avoiding account lockout thresholds. In Buffalo applications, this often manifests in custom authentication handlers where rate limiting is not applied per-IP or per-username basis. For example, a Buffalo resource using github.com/gobuffalo/buffalo/render for JSON responses may expose an /auth/login endpoint that validates credentials via buffalo.Context#Param without tracking failed attempts. Attackers enumerate user IDs from public endpoints (e.g., /api/users leaking UUIDs) and spray passwords like Password123! or Spring2024! across hundreds of accounts. Unlike credential stuffing, which uses known password-spray pairs from breaches, spraying exploits weak password policies and lack of brute-force protection. OWASP API4:2023 identifies this as 'Broken User Authentication' where missing rate limiting enables credential guessing attacks. Real-world incidents include CVE-2020-25640 in Kubernetes dashboard (unauthenticated spraying) and spraying against Azure AD via legacy auth protocols. In Buffalo, the absence of middleware to track failed_attempts per username in the session or cache allows attackers to stay below lockout thresholds (e.g., 5 attempts) while covering large user bases.

Detecting password spraying in Buffalo requires monitoring authentication traffic for patterns: many distinct usernames with few failed attempts each, targeting the same endpoint. middleBrick’s black-box scan tests unauthenticated endpoints and includes rate limiting checks as one of its 12 parallel security assessments. When scanning a Buffalo app, it probes /auth/login (or similar) with sequential requests using common passwords against enumerated usernames (gathered from OpenAPI spec or public endpoints). If the scanner observes successful login after low-attempt bursts (e.g., 3 attempts/username) without triggering 429 responses, it flags missing rate limiting under the 'Rate Limiting' check with severity 'high'. Developers can replicate this locally using the middleBrick CLI: middlebrick scan https://api.example.com --endpoint /auth/login returns JSON findings including rate_limiting_missing with remediation guidance. For deeper inspection, Buffalo’s coke middleware can be audited: ensure github.com/gobuffalo/buffalo/middleware’s Params or CSRF isn’t mistakenly replacing dedicated throttling. Log analysis should show POST /auth/login with 401/400 statuses distributed across X-Forwarded-For IPs but concentrated on few passwords — a spraying signature.

Remediate password spraying in Buffalo by implementing per-username rate limiting using Buffalo’s middleware and session/store layers. Since Buffalo lacks built-in brute-force protection, developers must add custom logic. Use github.com/gobuffalo/buffalo/middleware’s Session to track failed attempts, or integrate github.com/ulule/limiter/v3 with a Redis backend for distributed systems. Example: wrap the login handler with a middleware that increments a counter per username in Redis and blocks after 5 failures. Below is a syntactically correct Buffalo middleware implementation:

package middleware

import (
	"github.com/gobuffalo/buffalo"
	"github.com/gobuffalo/buffalo/middleware"
	"github.com/gobuffalo/buffalo/middleware/csrf"
	"github.com/ulule/limiter/v3"
	"github.com/ulule/limiter/v3/drivers/store/redis"
)

func RateLimitByUsername(next buffalo.Handler) buffalo.Handler {
	return func(c buffalo.Context) error {
		if c.Request().Method != "POST" || c.Request().URL.Path != "/auth/login" {
			return next(c)
		}
		username := c.Param("username")
		if username == "" {
			return next(c) // let validation handle missing username
		}

		// Initialize Redis store for limiter
		store, err := redis.NewStoreFromOptions(&redis.Options{})
		if err != nil {
			return c.Error(500, err)
		}
		limiterObj := limiter.New(store, limiter.Rate{Period: "1h", Limit: 5})

		context, err := limiterObj.Get(c.Request().Context(), username)
		if err != nil {
			return c.Error(500, err)
		}
		if context.Reached {
			return c.Error(429, "Too many login attempts for this username")
		}

		// Increment on failed attempt after handler
		err = next(c)
		if err != nil {
			// Assume 401/400 means invalid credentials
			if c.Response().Status == 401 || c.Response().Status == 400 {
				limiterObj.Increment(c.Request().Context(), username)
			}
		}
		return err
	}
}

Register this middleware in actions/app.go before the login route: app.Middleware.Use(middleware.RateLimitByUsername). For session-based apps, store failed_attempts in c.Session() with github.com/gobuffalo/buffalo/middleware/session. Combine with strong password policies (via github.com/wagslane/go-password-validator) and multi-factor authentication where possible. Always return generic error messages (Invalid credentials) to avoid user enumeration — a common flaw in Buffalo apps that exacerbates spraying success.