add req/resp header forwarding modifiers

proxychain/requestmodifers/forward_request_headers.go

@@ -0,0 +1,43 @@
+package requestmodifers
+
+import (
+	"ladder/proxychain"
+	"strings"
+)
+
+var forwardBlacklist map[string]bool
+
+func init() {
+	forwardBlacklist = map[string]bool{
+		"host":              true,
+		"connection":        true,
+		"keep-alive":        true,
+		"content-length":    true,
+		"content-encoding":  true,
+		"transfer-encoding": true,
+		"referer":           true,
+		"x-forwarded-for":   true,
+		"x-real-ip":         true,
+		"forwarded":         true,
+	}
+}
+
+// ForwardRequestHeaders forwards the requests headers sent from the client to the upstream server
+func ForwardRequestHeaders(ua string) proxychain.RequestModification {
+	return func(chain *proxychain.ProxyChain) error {
+
+		forwardHeaders := func(key, value []byte) {
+			k := strings.ToLower(string(key))
+			v := string(value)
+			if forwardBlacklist[k] {
+				return
+			}
+			chain.Request.Header.Set(k, v)
+		}
+
+		chain.Context.Request().
+			Header.VisitAll(forwardHeaders)
+
+		return nil
+	}
+}