improve ua modifier with client side spoofing

proxychain/requestmodifers/spoof_user_agent.go

@@ -1,13 +1,39 @@
 package requestmodifers
 
 import (
+	_ "embed"
 	"ladder/proxychain"
+	tx "ladder/proxychain/responsemodifers"
+	"strings"
 )
 
+// https://github.com/faisalman/ua-parser-js/tree/master
+// update using:
+// git submodule update --remote --merge
+//
+//go:embed vendor/ua-parser-js/dist/ua-parser.min.js
+var UAParserJS string
+
+// note: spoof_user_agent.js has a dependency on ua-parser.min.js
+// ua-parser.min.js should be loaded first.
+//
+//go:embed spoof_user_agent.js
+var spoofUserAgentJS string
+
 // SpoofUserAgent modifies the user agent
 func SpoofUserAgent(ua string) proxychain.RequestModification {
-	return func(px *proxychain.ProxyChain) error {
-		px.Request.Header.Set("user-agent", ua)
+	return func(chain *proxychain.ProxyChain) error {
+		// modify ua headers
+		chain.AddOnceRequestModifications(
+			SetRequestHeader("user-agent", ua),
+		)
+
+		script := strings.ReplaceAll(spoofUserAgentJS, "{{USER_AGENT}}", ua)
+		chain.AddOnceResponseModifications(
+			tx.InjectScriptBeforeDOMContentLoaded(script),
+			tx.InjectScriptBeforeDOMContentLoaded(UAParserJS),
+		)
+
 		return nil
 	}
 }