From 3a249f395cc44272d36757829c51a6d6fb863fc0 Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Mon, 26 Aug 2024 14:28:16 -0400
Subject: [PATCH] Improve `prevent-xhr` scriptlet

As per filter list maintainers feedback.
---
 assets/resources/scriptlets.js | 81 ++++++++++++++++++++++++++--------
 1 file changed, 63 insertions(+), 18 deletions(-)

diff --git a/assets/resources/scriptlets.js b/assets/resources/scriptlets.js
index 8acbb9894..0272ecce3 100644
--- a/assets/resources/scriptlets.js
+++ b/assets/resources/scriptlets.js
@@ -2695,6 +2695,13 @@ function noXhrIf(
         'content-type': '',
         'content-length': '',
     };
+    const safeDispatchEvent = (xhr, type) => {
+        try {
+            xhr.dispatchEvent(new Event(type));
+        } catch(_) {
+        }
+    };
+    const XHRBefore = XMLHttpRequest.prototype;
     self.XMLHttpRequest = class extends self.XMLHttpRequest {
         open(method, url, ...args) {
             xhrInstances.delete(this);
@@ -2721,27 +2728,26 @@ function noXhrIf(
             let promise = Promise.resolve({
                 xhr: this,
                 directive,
-                props: {
-                    readyState: { value: 4 },
+                response: {
                     response: { value: '' },
                     responseText: { value: '' },
                     responseXML: { value: null },
                     responseURL: { value: haystack.url },
-                    status: { value: 200 },
-                    statusText: { value: 'OK' },
-                },
+                }
             });
             switch ( this.responseType ) {
             case 'arraybuffer':
                 promise = promise.then(details => {
-                    details.props.response.value = new ArrayBuffer(0);
+                    const response = details.response;
+                    response.response.value = new ArrayBuffer(0);
                     return details;
                 });
                 haystack.headers['content-type'] = 'application/octet-stream';
                 break;
             case 'blob':
                 promise = promise.then(details => {
-                    details.props.response.value = new Blob([]);
+                    const response = details.response;
+                    response.response.value = new Blob([]);
                     return details;
                 });
                 haystack.headers['content-type'] = 'application/octet-stream';
@@ -2750,8 +2756,9 @@ function noXhrIf(
                 promise = promise.then(details => {
                     const parser = new DOMParser();
                     const doc = parser.parseFromString('', 'text/html');
-                    details.props.response.value = doc;
-                    details.props.responseXML.value = doc;
+                    const response = details.response;
+                    response.response.value = doc;
+                    response.responseXML.value = doc;
                     return details;
                 });
                 haystack.headers['content-type'] = 'text/html';
@@ -2759,8 +2766,9 @@ function noXhrIf(
             }
             case 'json':
                 promise = promise.then(details => {
-                    details.props.response.value = {};
-                    details.props.responseText.value = '{}';
+                    const response = details.response;
+                    response.response.value = {};
+                    response.responseText.value = '{}';
                     return details;
                 });
                 haystack.headers['content-type'] = 'application/json';
@@ -2769,8 +2777,9 @@ function noXhrIf(
                 if ( directive === '' ) { break; }
                 promise = promise.then(details => {
                     return generateContentFn(details.directive).then(text => {
-                        details.props.response.value = text;
-                        details.props.responseText.value = text;
+                        const response = details.response;
+                        response.response.value = text;
+                        response.responseText.value = text;
                         return details;
                     });
                 });
@@ -2778,11 +2787,35 @@ function noXhrIf(
                 break;
             }
             promise.then(details => {
-                haystack.headers['content-length'] = `${details.props.response.value}`.length;
-                Object.defineProperties(details.xhr, details.props);
-                details.xhr.dispatchEvent(new Event('readystatechange'));
-                details.xhr.dispatchEvent(new Event('load'));
-                details.xhr.dispatchEvent(new Event('loadend'));
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 1, configurable: true },
+                });
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                return details;
+            }).then(details => {
+                const response = details.response;
+                haystack.headers['content-length'] = `${response.response.value}`.length;
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 2, configurable: true },
+                    status: { value: 200 },
+                    statusText: { value: 'OK' },
+                });
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                return details;
+            }).then(details => {
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 3, configurable: true },
+                });
+                Object.defineProperties(details.xhr, details.response);
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                return details;
+            }).then(details => {
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 4 },
+                });
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                safeDispatchEvent(details.xhr, 'load');
+                safeDispatchEvent(details.xhr, 'loadend');
                 safe.uboLog(logPrefix, `Prevented with response:\n${details.xhr.response}`);
             });
         }
@@ -2809,6 +2842,18 @@ function noXhrIf(
             return out.join('\r\n');
         }
     };
+    self.XMLHttpRequest.prototype.open.toString = function() {
+        return XHRBefore.open.toString();
+    };
+    self.XMLHttpRequest.prototype.send.toString = function() {
+        return XHRBefore.send.toString();
+    };
+    self.XMLHttpRequest.prototype.getResponseHeader.toString = function() {
+        return XHRBefore.getResponseHeader.toString();
+    };
+    self.XMLHttpRequest.prototype.getAllResponseHeaders.toString = function() {
+        return XHRBefore.getAllResponseHeaders.toString();
+    };
 }
 
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