Credential Stuffing in Gin with Basic Auth

Credential stuffing is an automated attack where attackers use large lists of breached username and password pairs to gain unauthorized access. When Basic Auth is used in a Gin application without additional protections, each request carries credentials in an Authorization header encoded as base64(username:password). Because base64 is easily reversible, intercepted credentials are immediately usable. During a credential stuffing campaign, attackers iterate over many accounts, and Basic Auth provides no built-in mechanism to detect or throttle repeated failed attempts. In Gin, if routes are unprotected by middleware that enforces rate limits or account lockout, an attacker can send many sequential requests and iterate over credentials at scale. The authentication check may look like a simple comparison against a hardcoded user or a database query, but without per-account rate limiting or suspicious login velocity detection, the API effectively becomes a free login endpoint for bots. Moreover, if the same credentials are reused across services, stuffing attacks that originate from other breaches can succeed here even if the application has not directly leaked passwords. Because Basic Auth sends credentials with every request, logging or proxy misconfigurations may accidentally store these headers, further exposing credentials. In a black-box scan, middleBrick tests authentication by submitting known breached credential pairs and observing whether unauthorized access is granted, while also checking whether rate limiting is present to slow down high-volume attempts. The combination of weak or reused passwords, lack of rate controls, and the stateless nature of Basic Auth creates a favorable environment for successful credential stuffing.

To reduce credential stuffing risk with Basic Auth in Gin, combine strict transport security, per-request validation, and robust rate controls. Always serve Basic Auth over TLS to prevent on-path interception of the base64-encoded credentials. Implement middleware that validates credentials on each request and enforces rate limits scoped to username or client identity. Below are concrete, working examples that show how to structure these protections.

Example 1: Basic Auth with TLS enforcement and per-route middleware

//go
package main

import (
	"net/http"
	"strings"

	"github.com/gin-gonic/gin"
)

// hardcoded user store — replace with a secure hashed lookup in production
var validUser = "admin"
var validPasswordHash = "$2a$10$abc123..." // bcrypt hash placeholder

func RequireBasicAuth() gin.HandlerFunc {
	return func(c *gin.Context) {
		user, pass, ok := c.Request.BasicAuth()
		if !ok {
			c.Header("WWW-Authenticate", `Basic realm="restricted", charset="UTF-8"`)
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
			return
		}
		// In production, verify pass against a bcrypt hash using golang.org/x/crypto/bcrypt
		if user != validUser || !checkPasswordHash(pass, validPasswordHash) {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
			return
		}
		c.Next()
	}
}

// Placeholder — use golang.org/x/crypto/bcrypt in real code
func checkPasswordHash(password, hash string) bool {
	// bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
	return password == "correct-bcrypt-hash-placeholder"
}

func main() {
	r := gin.Default()

	// Enforce TLS in production by rejecting cleartext HTTP
	// Middleware can inspect X-Forwarded-Proto or TLS state as needed
	r.Use(func(c *gin.Context) {
		// Example header check when behind a proxy
		if c.Request.Header.Get("X-Forwarded-Proto") != "https" {
			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{"error": "HTTPS required"})
			return
		}
		c.Next()
	})

	protected := r.Group("/api")
	protected.Use(RequireBasicAuth())
	protected.GET("/data", func(c *gin.Context) {
		c.JSON(http.StatusOK, gin.H{"message": "protected data"})
	})

	r.RunTLS(":8443", "server.crt", "server.key")
}

Example 2: Rate limiting scoped to username to mitigate stuffing

//go
package main

import (
	"net/http"
	"strings"
	"sync"n"time"

	"github.com/gin-gonic/gin"
)

type RateLimiter struct {
	mu       sync.Mutex
	perUser  map[string][]time.Time
	limit    int           // max requests
	interval time.Duration // within this window
}

func NewRateLimiter(limit int, interval time.Duration) *RateLimiter {
	return &RateLimiter{
		perUser:  make(map[string][]time.Time),
		limit:    limit,
		interval: interval,
	}
}

func (rl *RateLimiter) Allow(user string) bool {
	rl.mu.Lock()
	defer rl.mu.Unlock()
	now := time.Now()
	// clean old entries
	var recent []time.Time
	for _, t := range rl.perUser[user] {
		if now.Sub(t) < rl.interval {
			recent = append(recent, t)
		}
	}
	rl.perUser[user] = recent
	if len(rl.perUser[user]) >= rl.limit {
		return false
	}
	rl.perUser[user] = append(rl.perUser[user], now)
	return true
}

func RequireBasicAuthWithRate(rl *RateLimiter) gin.HandlerFunc {
	return func(c *gin.Context) {
		user, pass, ok := c.Request.BasicAuth()
		if !ok {
			c.Header("WWW-Authenticate", `Basic realm="restricted", charset="UTF-8"`)
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "authentication required"})
			return
		}
		if !rl.Allow(user) {
			c.AbortWithStatusJSON(http.StatusTooManyRequests, gin.H{"error": "rate limit exceeded"})
			return
		}
		// credential verification should happen here as in Example 1
		// placeholder check
		if user == "admin" && pass == "correct-bcrypt-hash-placeholder" {
			c.Next()
		} else {
			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
		}
	}
}

func main() {
	r := gin.Default()
	rl := NewRateLimiter(5, time.Minute) // 5 requests per minute per user

	r.Use(func(c *gin.Context) {
		if c.Request.Header.Get("X-Forwarded-Proto") != "https" {
			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{"error": "HTTPS required"})
			return
		}
		c.Next()
	})

	protected := r.Group("/api")
	protected.Use(RequireBasicAuthWithRate(rl))
	protected.GET("/data", func(c *gin.Context) {
		c.JSON(http.StatusOK, gin.H{"message": "protected data"})
	})

	r.RunTLS(":8443", "server.crt", "server.key")
}

These examples emphasize that Basic Auth in Gin should always be deployed over TLS, paired with per-request credential validation, and coupled with rate limiting scoped to the username to reduce the effectiveness of credential stuffing. middleBrick’s authentication checks can verify whether these defenses are present during scans.