first

backend/internal/platform/middleware/ratelimit.go

@@ -0,0 +1,66 @@
+package middleware
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"golang.org/x/time/rate"
+)
+
+// PerIPRateLimiter limits requests per client IP, intended for sensitive
+// low-frequency endpoints like login (defense against credential stuffing
+// / brute force).
+type PerIPRateLimiter struct {
+	mu       sync.Mutex
+	limiters map[string]*rate.Limiter
+	r        rate.Limit
+	burst    int
+}
+
+func NewPerIPRateLimiter(requestsPerMinute int, burst int) *PerIPRateLimiter {
+	l := &PerIPRateLimiter{
+		limiters: make(map[string]*rate.Limiter),
+		r:        rate.Every(time.Minute / time.Duration(requestsPerMinute)),
+		burst:    burst,
+	}
+	go l.cleanupLoop()
+	return l
+}
+
+func (l *PerIPRateLimiter) getLimiter(ip string) *rate.Limiter {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	limiter, exists := l.limiters[ip]
+	if !exists {
+		limiter = rate.NewLimiter(l.r, l.burst)
+		l.limiters[ip] = limiter
+	}
+	return limiter
+}
+
+func (l *PerIPRateLimiter) cleanupLoop() {
+	for {
+		time.Sleep(10 * time.Minute)
+		l.mu.Lock()
+		for ip, limiter := range l.limiters {
+			if limiter.Tokens() >= float64(l.burst) {
+				delete(l.limiters, ip)
+			}
+		}
+		l.mu.Unlock()
+	}
+}
+
+func (l *PerIPRateLimiter) Middleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		ip := c.ClientIP()
+		if !l.getLimiter(ip).Allow() {
+			c.AbortWithStatusJSON(http.StatusTooManyRequests, gin.H{"error": "too many requests, try again later"})
+			return
+		}
+		c.Next()
+	}
+}