add random timeout on deny

Author: Pofilo

geoblock.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"io/fs"
 	"log"
+	"math/rand"
 	"net"
 	"net/http"
 	"os"
@@ -55,6 +56,7 @@ type Config struct {
 	HTTPStatusCodeDeniedRequest  int      `yaml:"httpStatusCodeDeniedRequest"`
 	LogFilePath                  string   `yaml:"logFilePath"`
 	RedirectURLIfDenied          string   `yaml:"redirectUrlIfDenied"`
+	DelayOnDenyMs                int      `yaml:"delayOnDenyMs"`
 }
 
 type ipEntry struct {
@@ -94,6 +96,7 @@ type GeoBlock struct {
 	logFile                      *os.File
 	redirectURLIfDenied          string
 	name                         string
+	delayOnDenyMs                int
 }
 
 // New created a new GeoBlock plugin.
@@ -178,6 +181,7 @@ func New(ctx context.Context, next http.Handler, config *Config, name string) (h
 		logFile:                      logFile,
 		redirectURLIfDenied:          config.RedirectURLIfDenied,
 		name:                         name,
+		delayOnDenyMs:                config.DelayOnDenyMs,
 	}, nil
 }
 
@@ -202,7 +206,12 @@ func (a *GeoBlock) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 				rw.WriteHeader(http.StatusFound)
 				return
 			}
-
+			// Introduce a delay before responding (with +-50%)
+			if a.delayOnDenyMs > 0 {
+				randomFactor := 0.5 + rand.Float64()  // between 0.5 and 1.5
+				randomDelay := time.Duration(float64(a.delayOnDenyMs) * randomFactor)
+				time.Sleep(time.Duration(randomDelay) * time.Millisecond)
+			}
 			rw.WriteHeader(a.httpStatusCodeDeniedRequest)
 			return
 		}

readme.md

@@ -182,6 +182,7 @@ my-GeoBlock:
             unknownCountryApiResponse: "nil"
             blackListMode: false
             addCountryHeader: false
+            delayOnDenyMs: 2000
             countries:
                 - AF # Afghanistan
                 - AL # Albania
@@ -526,3 +527,7 @@ Basically tells GeoBlock to only allow/deny a request based on the first IP addr
 ### Define a custom log file `redirectUrlIfDenied`
 
 Allows returning a HTTP 301 status code, which indicates that the requested resource has been moved. The URL which can be specified is used to redirect the client to. So instead of "blocking" the client, the client will be redirected to the configured URL.
+
+### Define a custom delay on requests `delayOnDenyMs`
+
+Add a +-50% random delay for deny requests. This is useful to limit spam from forbidden IPs.