Imrpove `prevent-xhr` scriptlet; add `trusted-prevent-xhr` scriptlet

Add support for synchronous `send()` calls.

`trusted-prevent-xhr` is essentially the same as `prevent-xhr` except
that if the `directive` argument is not a known token, it will be
used as is as the response text of the xhr request, whereas `prevent-xhr`
returns an empty string when the directive is unknown.

assets/resources/scriptlets.js

@@ -321,6 +321,9 @@ function runAtHtmlElementFn(fn) {
 
 // Reference:
 // https://github.com/AdguardTeam/Scriptlets/blob/master/wiki/about-scriptlets.md#prevent-xhr
+//
+// Added `trusted` argument to allow for returning arbitrary text. Can only
+// be used through scriptlets requiring trusted source.
 
 builtinScriptlets.push({
     name: 'generate-content.fn',
@@ -329,7 +332,7 @@ builtinScriptlets.push({
         'safe-self.fn',
     ],
 });
-function generateContentFn(directive) {
+function generateContentFn(trusted, directive) {
     const safe = safeSelf();
     const randomize = len => {
         const chunks = [];
@@ -343,27 +346,27 @@ function generateContentFn(directive) {
         return chunks.join(' ').slice(0, len);
     };
     if ( directive === 'true' ) {
-        return Promise.resolve(randomize(10));
+        return randomize(10);
     }
     if ( directive === 'emptyObj' ) {
-        return Promise.resolve('{}');
+        return '{}';
     }
     if ( directive === 'emptyArr' ) {
-        return Promise.resolve('[]');
+        return '[]';
     }
     if ( directive === 'emptyStr' ) {
-        return Promise.resolve('');
+        return '';
     }
     if ( directive.startsWith('length:') ) {
         const match = /^length:(\d+)(?:-(\d+))?$/.exec(directive);
-        if ( match ) {
+        if ( match === null ) { return ''; }
         const min = parseInt(match[1], 10);
         const extent = safe.Math_max(parseInt(match[2], 10) || 0, min) - min;
         const len = safe.Math_min(min + extent * safe.Math_random(), 500000);
-            return Promise.resolve(randomize(len | 0));
+        return randomize(len | 0);
     }
-    }
+    if ( directive.startsWith('war:') ) {
-    if ( directive.startsWith('war:') && scriptletGlobals.warOrigin ) {
+        if ( scriptletGlobals.warOrigin === undefined ) { return ''; }
         return new Promise(resolve => {
             const warOrigin = scriptletGlobals.warOrigin;
             const warName = directive.slice(4);
@@ -379,9 +382,12 @@ function generateContentFn(directive) {
             };
             warXHR.open('GET', fullpath.join(''));
             warXHR.send();
-        });
+        }).catch(( ) => '');
     }
-    return Promise.resolve('');
+    if ( trusted ) {
+        return directive;
+    }
+    return '';
 }
 
 /******************************************************************************/
@@ -1565,6 +1571,196 @@ function proxyApplyFn(
     context[prop] = new Proxy(fn, proxyDetails);
 }
 
+/******************************************************************************/
+
+builtinScriptlets.push({
+    name: 'prevent-xhr.fn',
+    fn: preventXhrFn,
+    dependencies: [
+        'generate-content.fn',
+        'match-object-properties.fn',
+        'parse-properties-to-match.fn',
+        'safe-self.fn',
+    ],
+});
+function preventXhrFn(
+    trusted = false,
+    propsToMatch = '',
+    directive = ''
+) {
+    if ( typeof propsToMatch !== 'string' ) { return; }
+    const safe = safeSelf();
+    const scriptletName = trusted ? 'trusted-prevent-xhr' : 'prevent-xhr';
+    const logPrefix = safe.makeLogPrefix(scriptletName, propsToMatch, directive);
+    const xhrInstances = new WeakMap();
+    const propNeedles = parsePropertiesToMatch(propsToMatch, 'url');
+    const warOrigin = scriptletGlobals.warOrigin;
+    const safeDispatchEvent = (xhr, type) => {
+        try {
+            xhr.dispatchEvent(new Event(type));
+        } catch(_) {
+        }
+    };
+    const XHRBefore = XMLHttpRequest.prototype;
+    self.XMLHttpRequest = class extends self.XMLHttpRequest {
+        open(method, url, defer, ...args) {
+            xhrInstances.delete(this);
+            if ( warOrigin !== undefined && url.startsWith(warOrigin) ) {
+                return super.open(method, url, defer, ...args);
+            }
+            const haystack = { method, url };
+            if ( propsToMatch === '' && directive === '' ) {
+                safe.uboLog(logPrefix, `Called: ${safe.JSON_stringify(haystack, null, 2)}`);
+                return super.open(method, url, defer, ...args);
+            }
+            if ( matchObjectProperties(propNeedles, haystack) ) {
+                const xhrDetails = Object.assign(haystack, {
+                    xhr: this,
+                    defer,
+                    directive,
+                    headers: {
+                        'date': '',
+                        'content-type': '',
+                        'content-length': '',
+                    },
+                    props: {
+                        response: { value: '' },
+                        responseText: { value: '' },
+                        responseXML: { value: null },
+                        responseURL: { value: haystack.url },
+                    },
+                });
+                xhrInstances.set(this, xhrDetails);
+            }
+            return super.open(method, url, defer, ...args);
+        }
+        send(...args) {
+            const xhrDetails = xhrInstances.get(this);
+            if ( xhrDetails === undefined ) {
+                return super.send(...args);
+            }
+            xhrDetails.headers['date'] = (new Date()).toUTCString();
+            let xhrText = '';
+            switch ( this.responseType ) {
+            case 'arraybuffer':
+                xhrDetails.props.response.value = new ArrayBuffer(0);
+                xhrDetails.headers['content-type'] = 'application/octet-stream';
+                break;
+            case 'blob':
+                xhrDetails.props.response.value = new Blob([]);
+                xhrDetails.headers['content-type'] = 'application/octet-stream';
+                break;
+            case 'document': {
+                const parser = new DOMParser();
+                const doc = parser.parseFromString('', 'text/html');
+                xhrDetails.props.response.value = doc;
+                xhrDetails.props.responseXML.value = doc;
+                xhrDetails.headers['content-type'] = 'text/html';
+                break;
+            }
+            case 'json':
+                xhrDetails.props.response.value = {};
+                xhrDetails.props.responseText.value = '{}';
+                xhrDetails.headers['content-type'] = 'application/json';
+                break;
+            default: {
+                if ( directive === '' ) { break; }
+                xhrText = generateContentFn(trusted, xhrDetails.directive);
+                if ( xhrText instanceof Promise ) {
+                    xhrText = xhrText.then(text => {
+                        xhrDetails.props.response.value = text;
+                        xhrDetails.props.responseText.value = text;
+                    });
+                } else {
+                    xhrDetails.props.response.value = xhrText;
+                    xhrDetails.props.responseText.value = xhrText;
+                }
+                xhrDetails.headers['content-type'] = 'text/plain';
+                break;
+            }
+            }
+            if ( xhrDetails.defer === false ) {
+                xhrDetails.headers['content-length'] = `${xhrDetails.props.response.value}`.length;
+                Object.defineProperties(xhrDetails.xhr, {
+                    readyState: { value: 4 },
+                    status: { value: 200 },
+                    statusText: { value: 'OK' },
+                });
+                Object.defineProperties(xhrDetails.xhr, xhrDetails.props);
+                return;
+            }
+            Promise.resolve(xhrText).then(( ) => xhrDetails).then(details => {
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 1, configurable: true },
+                });
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                return details;
+            }).then(details => {
+                xhrDetails.headers['content-length'] = `${details.props.response.value}`.length;
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 2, configurable: true },
+                    status: { value: 200 },
+                    statusText: { value: 'OK' },
+                });
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                return details;
+            }).then(details => {
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 3, configurable: true },
+                });
+                Object.defineProperties(details.xhr, details.props);
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                return details;
+            }).then(details => {
+                Object.defineProperties(details.xhr, {
+                    readyState: { value: 4 },
+                });
+                safeDispatchEvent(details.xhr, 'readystatechange');
+                safeDispatchEvent(details.xhr, 'load');
+                safeDispatchEvent(details.xhr, 'loadend');
+                safe.uboLog(logPrefix, `Prevented with response:\n${details.xhr.response}`);
+            });
+        }
+        getResponseHeader(headerName) {
+            const xhrDetails = xhrInstances.get(this);
+            if ( xhrDetails === undefined || this.readyState < this.HEADERS_RECEIVED ) {
+                return super.getResponseHeader(headerName);
+            }
+            const value = xhrDetails.headers[headerName.toLowerCase()];
+            if ( value !== undefined && value !== '' ) { return value; }
+            return null;
+        }
+        getAllResponseHeaders() {
+            const xhrDetails = xhrInstances.get(this);
+            if ( xhrDetails === undefined || this.readyState < this.HEADERS_RECEIVED ) {
+                return super.getAllResponseHeaders();
+            }
+            const out = [];
+            for ( const [ name, value ] of Object.entries(xhrDetails.headers) ) {
+                if ( !value ) { continue; }
+                out.push(`${name}: ${value}`);
+            }
+            if ( out.length !== 0 ) { out.push(''); }
+            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();
+    };
+}
+
+
+
+
 /*******************************************************************************
 
     Injectable scriptlets
@@ -2271,7 +2467,7 @@ function noFetchIf(
         if ( proceed ) {
             return context.reflect();
         }
-        return generateContentFn(responseBody).then(text => {
+        return Promise.resolve(generateContentFn(false, responseBody)).then(text => {
             safe.uboLog(logPrefix, `Prevented with response "${text}"`);
             const response = new Response(text, {
                 headers: {
@@ -2730,192 +2926,17 @@ function webrtcIf(
 /******************************************************************************/
 
 builtinScriptlets.push({
-    name: 'no-xhr-if.js',
+    name: 'prevent-xhr.js',
     aliases: [
-        'prevent-xhr.js',
+        'no-xhr-if.js',
     ],
-    fn: noXhrIf,
+    fn: preventXhr,
     dependencies: [
-        'generate-content.fn',
+        'prevent-xhr.fn',
-        'match-object-properties.fn',
-        'parse-properties-to-match.fn',
-        'safe-self.fn',
     ],
 });
-function noXhrIf(
+function preventXhr(...args) {
-    propsToMatch = '',
+    return preventXhrFn(false, ...args);
-    directive = ''
-) {
-    if ( typeof propsToMatch !== 'string' ) { return; }
-    const safe = safeSelf();
-    const logPrefix = safe.makeLogPrefix('prevent-xhr', propsToMatch, directive);
-    const xhrInstances = new WeakMap();
-    const propNeedles = parsePropertiesToMatch(propsToMatch, 'url');
-    const warOrigin = scriptletGlobals.warOrigin;
-    const headers = {
-        'date': '',
-        '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);
-            if ( warOrigin !== undefined && url.startsWith(warOrigin) ) {
-                return super.open(method, url, ...args);
-            }
-            const haystack = { method, url };
-            if ( propsToMatch === '' && directive === '' ) {
-                safe.uboLog(logPrefix, `Called: ${safe.JSON_stringify(haystack, null, 2)}`);
-                return super.open(method, url, ...args);
-            }
-            if ( matchObjectProperties(propNeedles, haystack) ) {
-                xhrInstances.set(this, haystack);
-            }
-            haystack.headers = Object.assign({}, headers);
-            return super.open(method, url, ...args);
-        }
-        send(...args) {
-            const haystack = xhrInstances.get(this);
-            if ( haystack === undefined ) {
-                return super.send(...args);
-            }
-            haystack.headers['date'] = (new Date()).toUTCString();
-            let promise = Promise.resolve({
-                xhr: this,
-                directive,
-                response: {
-                    response: { value: '' },
-                    responseText: { value: '' },
-                    responseXML: { value: null },
-                    responseURL: { value: haystack.url },
-                }
-            });
-            switch ( this.responseType ) {
-            case 'arraybuffer':
-                promise = promise.then(details => {
-                    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 => {
-                    const response = details.response;
-                    response.response.value = new Blob([]);
-                    return details;
-                });
-                haystack.headers['content-type'] = 'application/octet-stream';
-                break;
-            case 'document': {
-                promise = promise.then(details => {
-                    const parser = new DOMParser();
-                    const doc = parser.parseFromString('', 'text/html');
-                    const response = details.response;
-                    response.response.value = doc;
-                    response.responseXML.value = doc;
-                    return details;
-                });
-                haystack.headers['content-type'] = 'text/html';
-                break;
-            }
-            case 'json':
-                promise = promise.then(details => {
-                    const response = details.response;
-                    response.response.value = {};
-                    response.responseText.value = '{}';
-                    return details;
-                });
-                haystack.headers['content-type'] = 'application/json';
-                break;
-            default:
-                if ( directive === '' ) { break; }
-                promise = promise.then(details => {
-                    return generateContentFn(details.directive).then(text => {
-                        const response = details.response;
-                        response.response.value = text;
-                        response.responseText.value = text;
-                        return details;
-                    });
-                });
-                haystack.headers['content-type'] = 'text/plain';
-                break;
-            }
-            promise.then(details => {
-                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${details.xhr.response}`);
-            });
-        }
-        getResponseHeader(headerName) {
-            const haystack = xhrInstances.get(this);
-            if ( haystack === undefined || this.readyState < this.HEADERS_RECEIVED ) {
-                return super.getResponseHeader(headerName);
-            }
-            const value = haystack.headers[headerName.toLowerCase()];
-            if ( value !== undefined && value !== '' ) { return value; }
-            return null;
-        }
-        getAllResponseHeaders() {
-            const haystack = xhrInstances.get(this);
-            if ( haystack === undefined || this.readyState < this.HEADERS_RECEIVED ) {
-                return super.getAllResponseHeaders();
-            }
-            const out = [];
-            for ( const [ name, value ] of Object.entries(haystack.headers) ) {
-                if ( !value ) { continue; }
-                out.push(`${name}: ${value}`);
-            }
-            if ( out.length !== 0 ) { out.push(''); }
-            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();
-    };
 }
 
 /******************************************************************************/
@@ -5103,4 +5124,23 @@ function trustedSuppressNativeMethod(
     });
 }
 
+/*******************************************************************************
+ * 
+ * Trusted version of prevent-xhr(), which allows the use of an arbitrary
+ * string as response text.
+ * 
+ * */
+
+builtinScriptlets.push({
+    name: 'trusted-prevent-xhr.js',
+    requiresTrust: true,
+    fn: trustedPreventXhr,
+    dependencies: [
+        'prevent-xhr.fn',
+    ],
+});
+function trustedPreventXhr(...args) {
+    return preventXhrFn(true, ...args);
+}
+
 /******************************************************************************/