AG-30879 Add trusted-replace-outbound-text scriptlet. #410

Squashed commit of the following:

commit e7a0a2d
Merge: a6f85a7 45a42cc
Author: Adam Wróblewski <[email protected]>
Date:   Mon May 20 17:28:17 2024 +0200

    Merge branch 'master' into feature/AG-30879

commit a6f85a7
Author: Adam Wróblewski <[email protected]>
Date:   Mon May 20 18:26:45 2024 +0300

    AG-30879 Add ability to decode text in trusted-replace-outbound-text scriptlet

    Squashed commit of the following:

    commit fc7fcdc
    Author: Adam Wróblewski <[email protected]>
    Date:   Tue May 14 11:51:48 2024 +0200

        Rename to isValidBase64

    commit e87edc4
    Author: Adam Wróblewski <[email protected]>
    Date:   Tue May 7 10:53:14 2024 +0200

        Add logging for invalid base64 encoded strings

    commit 788f70b
    Author: Adam Wróblewski <[email protected]>
    Date:   Mon May 6 17:54:10 2024 +0200

        Add variable for logging decoded content
        Improve checkIfValidBase64 and add more tests

    commit f0f931e
    Author: Adam Wróblewski <[email protected]>
    Date:   Fri May 3 17:08:17 2024 +0200

        trusted-replace-outbound-text - add ability to decode base64 text content

commit ff3e186
Author: Adam Wróblewski <[email protected]>
Date:   Fri Apr 26 11:03:30 2024 +0200

    Update decription

commit 0693ec6
Author: Adam Wróblewski <[email protected]>
Date:   Fri Apr 26 10:25:39 2024 +0200

    Update description

commit 76c8016
Author: Adam Wróblewski <[email protected]>
Date:   Fri Apr 26 10:00:07 2024 +0200

    Log information that content is not a string

commit c88ce94
Author: Adam Wróblewski <[email protected]>
Date:   Fri Apr 26 09:34:46 2024 +0200

    Fix typo in function name

commit 7ebb300
Author: Adam Wróblewski <[email protected]>
Date:   Thu Apr 25 12:18:59 2024 +0200

    Log information about not modified content
    Add a test

commit 48545bf
Author: Adam Wróblewski <[email protected]>
Date:   Tue Apr 23 12:48:51 2024 +0200

    Set default parameters
    Update test

commit 2fcc905
Author: Adam Wróblewski <[email protected]>
Date:   Mon Apr 22 20:06:00 2024 +0200

    Add trusted-replace-outbound-text scriptlet

CHANGELOG.md

@@ -13,6 +13,7 @@ The format is based on [Keep a Changelog], and this project adheres to [Semantic
 
 - `isRedirectResourceCompatibleWithAdg()` method to check compatibility of redirect resources with AdGuard
   without needing the full rule text [#420]
+- `trusted-replace-outbound-text` scriptlet [#410]
 - `trusted-dispatch-event` scriptlet [#382]
 
 ### Deprecated
@@ -26,6 +27,7 @@ The format is based on [Keep a Changelog], and this project adheres to [Semantic
 [Unreleased]: https://github.com/AdguardTeam/Scriptlets/compare/v1.10.25...HEAD
 [#425]: https://github.com/AdguardTeam/Scriptlets/issues/425
 [#420]: https://github.com/AdguardTeam/Scriptlets/issues/420
+[#410]: https://github.com/AdguardTeam/Scriptlets/issues/410
 [#382]: https://github.com/AdguardTeam/Scriptlets/issues/382
 
 ## [v1.10.25] - 2024-03-28

src/scriptlets/scriptlets-list.js

@@ -71,6 +71,7 @@ export * from './no-protected-audience';
 export * from './trusted-suppress-native-method';
 export * from './json-prune-xhr-response';
 export * from './trusted-dispatch-event';
+export * from './trusted-replace-outbound-text';
 // redirects as scriptlets
 // https://github.com/AdguardTeam/Scriptlets/issues/300
 export * from './amazon-apstag';

src/scriptlets/trusted-replace-outbound-text.ts

@@ -0,0 +1,298 @@
+import {
+    hit,
+    matchStackTrace,
+    getPropertyInChain,
+    getWildcardPropertyInChain,
+    logMessage,
+    // following helpers are needed for helpers above
+    shouldAbortInlineOrInjectedScript,
+    getNativeRegexpTest,
+    toRegExp,
+    isEmptyObject,
+} from '../helpers/index';
+
+/* eslint-disable max-len */
+/**
+ * @trustedScriptlet trusted-replace-outbound-text
+ *
+ * @description
+ * Replace the text in the outbound function call.
+ *
+ * Related UBO scriptlet:
+ * https://github.com/gorhill/uBlock/commit/21e1ee30ee36c1b9a7a3c9f43ac97e52d8e79661
+ *
+ * ### Syntax
+ *
+ * <!-- markdownlint-disable line-length -->
+ * ```text
+ * example.org#%#//scriptlet('trusted-replace-outbound-text', methodPath[, textToReplace[, replacement[, decodeMethod[, stack[, logContent]]]]])
+ * ```
+ * <!-- markdownlint-enable line-length -->
+ *
+ * - `methodPath` — required, the name of the function to trap, it must have an object as an argument.
+ *   Call with only `methodPath` as an argument will log all text content of the specified function to console,
+ *   but only if function call returns a string, otherwise it will log information that content is not a string.
+ * - `textToReplace` — optional, string or regular expression which should be replaced.
+ *   By default it's set to `''`. If it's not set to other value and `logContent` is set, it will log the original content.
+ * - `replacement` — optional, string which replace the matched text.
+ *   By default it's set to '', so matched content will removed.
+ * - `decodeMethod` — optional, string which specifies the method used to decode the content.
+ *   For now supported value is 'base64'. By default it's set to `''` and no decoding is performed.
+ *   If it's set and `logContent` is also set and `textToReplace` and `replacement` are not set,
+ *   then it will log the decoded content.
+ * - `stack` — optional, string or regular expression that must match the current function call stack trace.
+ *   If regular expression is invalid it will be skipped.
+ * - `logContent` — optional, if set to any value, the original and modified content will be logged.
+ *   By default it's set to '' and no content will be logged.
+ *
+ * > Logging content may be useful for debugging but it is not allowed for prod versions of filter lists.
+ *
+ * ### Examples
+ *
+ * <!-- markdownlint-disable line-length -->
+ *
+ * 1. Replace `foo` with 'bar' from the payload of the atob call:
+ *
+ *     ```adblock
+ *     example.org#%#//scriptlet('trusted-replace-outbound-text', 'atob', 'foo', 'bar')
+ *     ```
+ *
+ *     For instance, the following call will return `bar`
+ *
+ *     ```html
+ *     const text = btoa('foo');
+ *     atob(text);
+ *     ```
+ *
+ * 1. Replace `disable_ads:false` with 'disable_ads:true' from the payload of the `Array.prototype.join` if content is encoded in base64:
+ *
+ *     ```adblock
+ *     example.org#%#//scriptlet('trusted-replace-outbound-text', 'Array.prototype.join', 'disable_ads:false', 'disable_ads:true', 'base64')
+ *     ```
+ *
+ *     For instance, the following call will return `ZGlzYWJsZV9hZHM6dHJ1ZQ==` which is `'disable_ads:true'` after decoding
+ *
+ *     ```html
+ *     const arrayBase64 = ['ZGlzYWJsZV9h','ZHM6ZmFsc2U=']; // `ZGlzYWJsZV9hZHM6ZmFsc2U=` after decoding is `disable_ads:false`
+ *     arrayBase64.join('');
+ *     ```
+ *
+ * 1. Replace `"loadAds":true` with `"loadAds":false` from the payload of the JSON.stringify if the stack trace contains `testStackFunction`:
+ *
+ *     ```adblock
+ *     example.org#%#//scriptlet('trusted-replace-outbound-text', 'JSON.stringify', '"loadAds":true', '"loadAds":false', '', 'testStackFunction')
+ *     ```
+ *
+ *     For instance, the following call will return `'{"loadAds":false,"content":"bar"}'`
+ *
+ *     ```html
+ *     const testStackFunction = () => JSON.stringify({ loadAds: true, content: 'bar' });
+ *     testStackFunction();
+ *     ```
+ *
+ * 1. Call with `decodeMethod` and `logContent` arguments will log original and decoded text content of the specified function:
+ *
+ *     ```adblock
+ *     example.org#%#//scriptlet('trusted-replace-outbound-text', 'Array.prototype.join', '', '', 'base64' , '', 'true')
+ *     ```
+ *
+ * 1. Call with only first argument will log text content of the specified function:
+ *
+ *     ```adblock
+ *     example.org#%#//scriptlet('trusted-replace-outbound-text', 'atob')
+ *     ```
+ *
+ * 1. Call with `logContent` argument will log original and modified text content of the specified function:
+ *
+ *     ```adblock
+ *     example.org#%#//scriptlet('trusted-replace-outbound-text', 'atob', 'foo', 'bar', '', '', 'true')
+ *     ```
+ *
+ * <!-- markdownlint-enable line-length -->
+ *
+ * @added unknown.
+ */
+/* eslint-enable max-len */
+export function trustedReplaceOutboundText(
+    source: Source,
+    methodPath: string,
+    textToReplace = '',
+    replacement = '',
+    decodeMethod = '',
+    stack = '',
+    logContent = '',
+) {
+    if (!methodPath) {
+        return;
+    }
+
+    const getPathParts = getPropertyInChain as unknown as (base: Window, chain: string) => {
+        base: Record<string, unknown>;
+        prop: string;
+        chain?: string;
+    };
+
+    const { base, chain, prop } = getPathParts(window, methodPath);
+
+    if (typeof chain !== 'undefined') {
+        logMessage(source, `Could not reach the end of the prop chain: ${methodPath}`);
+        return;
+    }
+
+    const nativeMethod = base[prop];
+    if (!nativeMethod || typeof nativeMethod !== 'function') {
+        logMessage(source, `Could not retrieve the method: ${methodPath}`);
+        return;
+    }
+
+    /**
+     * A simple check if a string is a valid base64 encoded string.
+     * If after decoding and encoding the string is not the same as the original string,
+     * then the string is not a valid base64 encoded string.
+     *
+     * @param str - The string to be checked.
+     * @returns A boolean indicating whether the string is a valid base64 encoded string.
+     */
+    const isValidBase64 = (str: string): boolean => {
+        try {
+            if (str === '') {
+                return false;
+            }
+            const decodedString = atob(str);
+            const encodedString = btoa(decodedString);
+            // Encoded string may contains padding characters, so it's necessary to remove it before comparison
+            const stringWithoutPadding = str.replace(/=+$/, '');
+            const encodedStringWithoutPadding = encodedString.replace(/=+$/, '');
+            return encodedStringWithoutPadding === stringWithoutPadding;
+        } catch (e) {
+            return false;
+        }
+    };
+
+    /**
+     * Decodes the content, replaces the matched pattern with the specified text replacement,
+     * and returns the modified content.
+     * If the decode method is not specified, then content is modified without decoding.
+     *
+     * @param content - The original content to be decoded and replaced.
+     * @param pattern - The regular expression pattern to match.
+     * @param textReplacement - The text to replace the matched pattern.
+     * @param decode - The method used to decode the content. For now only supported value is 'base64'.
+     * @param log - The string, if set, decoded content should be logged.
+     * @returns The content after modifying.
+     */
+    const decodeAndReplaceContent = (
+        content: string,
+        pattern: RegExp,
+        textReplacement: string,
+        decode: string,
+        log: string,
+    ): String => {
+        switch (decode) {
+            case 'base64':
+                try {
+                    if (!isValidBase64(content)) {
+                        logMessage(source, `Text content is not a valid base64 encoded string: ${content}`);
+                        return content;
+                    }
+                    const decodedContent = atob(content);
+
+                    if (log) {
+                        logMessage(source, `Decoded text content: ${decodedContent}`);
+                    }
+
+                    const modifiedContent = textToReplace
+                        ? decodedContent.replace(pattern, textReplacement)
+                        : decodedContent;
+
+                    if (log) {
+                        const message = modifiedContent !== decodedContent
+                            ? `Modified decoded text content: ${modifiedContent}`
+                            : 'Decoded text content was not modified';
+
+                        logMessage(source, message);
+                    }
+
+                    const encodedContent = btoa(modifiedContent);
+                    return encodedContent;
+                } catch (e) {
+                    return content;
+                }
+            default:
+                return content.replace(pattern, textReplacement);
+        }
+    };
+
+    const logOriginalContent = !textToReplace || !!logContent;
+    const logModifiedContent = !!logContent;
+    const logDecodedContent = !!decodeMethod && !!logContent;
+
+    // This flag allows to prevent infinite loops when trapping props that are used by scriptlet's own code.
+    let isMatchingSuspended = false;
+
+    const objectWrapper = (
+        target: Function,
+        thisArg: any,
+        argumentsList: unknown[],
+    ) => {
+        if (isMatchingSuspended) {
+            return Reflect.apply(target, thisArg, argumentsList);
+        }
+        isMatchingSuspended = true;
+        hit(source);
+        const result = Reflect.apply(target, thisArg, argumentsList);
+
+        if (stack && !matchStackTrace(stack, new Error().stack || '')) {
+            return result;
+        }
+
+        if (typeof result === 'string') {
+            if (logOriginalContent) {
+                logMessage(source, `Original text content: ${result}`);
+            }
+
+            const patternRegexp = toRegExp(textToReplace);
+            const modifiedContent = textToReplace || logDecodedContent
+                ? decodeAndReplaceContent(result, patternRegexp, replacement, decodeMethod, logContent)
+                : result;
+
+            if (logModifiedContent) {
+                const message = modifiedContent !== result
+                    ? `Modified text content: ${modifiedContent}`
+                    : 'Text content was not modified';
+
+                logMessage(source, message);
+            }
+
+            isMatchingSuspended = false;
+            return modifiedContent;
+        }
+        isMatchingSuspended = false;
+        logMessage(source, 'Content is not a string');
+        return result;
+    };
+
+    const objectHandler = {
+        apply: objectWrapper,
+    };
+
+    base[prop] = new Proxy(nativeMethod, objectHandler);
+}
+
+trustedReplaceOutboundText.names = [
+    'trusted-replace-outbound-text',
+    // trusted scriptlets support no aliases
+];
+
+trustedReplaceOutboundText.injections = [
+    hit,
+    matchStackTrace,
+    getPropertyInChain,
+    getWildcardPropertyInChain,
+    logMessage,
+    // following helpers are needed for helpers above
+    shouldAbortInlineOrInjectedScript,
+    getNativeRegexpTest,
+    toRegExp,
+    isEmptyObject,
+];