begin refactor of proxy engine

proxychain/rsm/block_incoming_cookies.go

@@ -0,0 +1,58 @@
+package rsm // ReSponseModifers
+
+import (
+	"ladder/proxychain"
+	"net/http"
+)
+
+// BlockIncomingCookies prevents ALL cookies from being sent from the proxy server
+// to the client.
+func BlockIncomingCookies(whitelist ...string) proxychain.ResponseModification {
+	return func(px *proxychain.ProxyChain) error {
+		px.Response.Header.Del("Set-Cookie")
+		return nil
+	}
+}
+
+// BlockIncomingCookiesExcept prevents non-whitelisted cookies from being sent from the proxy server
+// to the client. Cookies whose names are in the whitelist are not removed.
+func BlockIncomingCookiesExcept(whitelist ...string) proxychain.ResponseModification {
+	return func(px *proxychain.ProxyChain) error {
+		// Convert whitelist slice to a map for efficient lookups
+		whitelistMap := make(map[string]struct{})
+		for _, cookieName := range whitelist {
+			whitelistMap[cookieName] = struct{}{}
+		}
+
+		// If the response has no cookies, return early
+		if px.Response.Header == nil {
+			return nil
+		}
+
+		// Filter the cookies in the response
+		filteredCookies := []string{}
+		for _, cookieStr := range px.Response.Header["Set-Cookie"] {
+			cookie := parseCookie(cookieStr)
+			if _, found := whitelistMap[cookie.Name]; found {
+				filteredCookies = append(filteredCookies, cookieStr)
+			}
+		}
+
+		// Update the Set-Cookie header with the filtered cookies
+		if len(filteredCookies) > 0 {
+			px.Response.Header["Set-Cookie"] = filteredCookies
+		} else {
+			px.Response.Header.Del("Set-Cookie")
+		}
+
+		return nil
+	}
+}
+
+// parseCookie parses a cookie string and returns an http.Cookie object.
+func parseCookie(cookieStr string) *http.Cookie {
+	header := http.Header{}
+	header.Add("Set-Cookie", cookieStr)
+	request := http.Request{Header: header}
+	return request.Cookies()[0]
+}