add whitelist of allowed remote hosts

imageproxy.go

@@ -5,12 +5,14 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"strings"
 
 	"github.com/willnorris/go-imageproxy/cache"
 	"github.com/willnorris/go-imageproxy/proxy"
 )
 
 var port = flag.Int("port", 8080, "port to listen on")
+var whitelist = flag.String("whitelist", "", "comma separated list of allowed remote hosts")
 
 func main() {
 	flag.Parse()
@@ -19,6 +21,9 @@ func main() {
 
 	p := proxy.NewProxy(nil)
 	p.Cache = cache.NewMemoryCache()
+	if *whitelist != "" {
+		p.Whitelist = strings.Split(*whitelist, ",")
+	}
 	server := &http.Server{
 		Addr:    fmt.Sprintf(":%d", *port),
 		Handler: p,