go-macaron Filter for Open Redirect attempts

filter.go

// Use with:
// m.Before(filter.Filter)
//

package filter

import (
	"fmt"
	"net/http"

	log "github.com/sirupsen/logrus"
)

func isInvalidRequest(url string) bool {
	return url[0] == '/' && (url[1] == '/' || url[1] == '\\')
}

// Filter - Filter for possible open redirect URIs
func Filter(rw http.ResponseWriter, req *http.Request) bool {
	if req.Method == http.MethodGet {
		urlLen := len(req.URL.Path)

		if urlLen <= 1 {
			return false
		} else {
			if isInvalidRequest(req.URL.Path) {
				rw.WriteHeader(http.StatusNotFound)
				log.Debug(fmt.Sprintf("Invalid URL Found: %s", req.URL.Path))
				return true
			}
		}
	}

	return false
}