Go

Check and report with net/http, including a small middleware.

Plain net/http, no dependencies.

Check an address

func isipsafeScore(ctx context.Context, ip string) (int, error) {
	ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
	defer cancel()
	req, _ := http.NewRequestWithContext(ctx, "GET", "https://isipsafe.com/api/v1/check?ip="+url.QueryEscape(ip), nil)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return 0, err
	}
	defer resp.Body.Close()
	var out struct {
		Data struct {
			Score int `json:"abuseConfidenceScore"`
		} `json:"data"`
	}
	err = json.NewDecoder(resp.Body).Decode(&out)
	return out.Data.Score, err
}

Middleware

func blockListed(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		ip, _, _ := net.SplitHostPort(r.RemoteAddr)
		if score, err := isipsafeScore(r.Context(), ip); err == nil && score >= 75 {
			http.Error(w, "access denied", http.StatusForbidden)
			return
		}
		next.ServeHTTP(w, r) // fail open on errors
	})
}

Add a small cache (a map with expiry, or a library like golang-lru) before using this on hot paths.

Report an address

form := url.Values{"ip": {ip}, "categories": {"web-app-attack,brute-force"}, "comment": {"40 failed logins"}}
resp, err := http.PostForm("https://isipsafe.com/api/v1/report?key="+os.Getenv("ISIPSAFE_KEY"), form)

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