From 788f70bdd1c2d64e4eb96dc6f99e0720cff80882 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Adam=20Wr=C3=B3blewski?= <adam@adguard.com>
Date: Mon, 6 May 2024 17:54:10 +0200
Subject: [PATCH] Add variable for logging decoded content Improve
 checkIfValidBase64 and add more tests

---
 .../trusted-replace-outbound-text.ts          | 17 +++++++++----
 .../trusted-replace-outbound-text.test.js     | 25 ++++++++++++++-----
 2 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/src/scriptlets/trusted-replace-outbound-text.ts b/src/scriptlets/trusted-replace-outbound-text.ts
index e2a1f39a7..564cdc025 100644
--- a/src/scriptlets/trusted-replace-outbound-text.ts
+++ b/src/scriptlets/trusted-replace-outbound-text.ts
@@ -153,9 +153,17 @@ export function trustedReplaceOutboundText(
      * @param str - The string to be checked.
      * @returns A boolean indicating whether the string is a valid base64 encoded string.
      */
-    const checkIfValidBase64 = (str: string) => {
+    const checkIfValidBase64 = (str: string): boolean => {
         try {
-            return str === '' ? false : btoa(atob(str)) === str;
+            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;
         }
@@ -216,6 +224,7 @@ export function trustedReplaceOutboundText(
 
     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;
@@ -242,9 +251,7 @@ export function trustedReplaceOutboundText(
             }
 
             const patternRegexp = toRegExp(textToReplace);
-            // If textToReplace is not set and decodeMethod and logContent are set
-            // then decoded content should be logged.
-            const modifiedContent = textToReplace || (decodeMethod && logContent)
+            const modifiedContent = textToReplace || logDecodedContent
                 ? decodeAndReplaceContent(result, patternRegexp, replacement, decodeMethod, logContent)
                 : result;
 
diff --git a/tests/scriptlets/trusted-replace-outbound-text.test.js b/tests/scriptlets/trusted-replace-outbound-text.test.js
index 541d302cd..ebb8b40ba 100644
--- a/tests/scriptlets/trusted-replace-outbound-text.test.js
+++ b/tests/scriptlets/trusted-replace-outbound-text.test.js
@@ -179,6 +179,19 @@ test('replace text - Array.prototype.join, decode base64', (assert) => {
     assert.strictEqual(window.hit, 'FIRED', 'hit function fired');
 });
 
+test('replace text - Array.prototype.join, decode base64, test for padding "="', (assert) => {
+    runScriptlet(name, ['Array.prototype.join', 'fooBarTest=', 'Test=', 'base64']);
+    const expectedText = 'Test=';
+    const expectedTextInBase64 = btoa(expectedText);
+    const textInBase64 = 'Zm9vQmFyVGVzdD0';
+    const splittedText = textInBase64.split('');
+    const result = splittedText.join('');
+    const decodedResult = atob(result);
+    assert.deepEqual(result, expectedTextInBase64, 'content in base64 is modified');
+    assert.deepEqual(decodedResult, expectedText, 'content is modified');
+    assert.strictEqual(window.hit, 'FIRED', 'hit function fired');
+});
+
 test('replace text decode - Array.prototype.join, match stack', (assert) => {
     runScriptlet(name, ['Array.prototype.join', 'disable_ads:false', 'disable_ads:true', 'base64', 'decodeStackFunc']);
     const decodeStackFunc = () => {
@@ -203,12 +216,12 @@ test('log - Array.prototype.join, base64', (assert) => {
         const argsLength = args.length;
         const consoleContent = args[0];
         if (argsLength === 1 && consoleContent.includes('Original text content:')) {
-            assert.ok(consoleContent.includes('Original text content:'), 'should log original text in console');
-            assert.ok(consoleContent.includes('Zm9vOmJhcixxd2VydHk6MTIzNA=='), 'should log original text in console');
+            assert.ok(consoleContent.includes('Original text content:'), '1 should log original text in console');
+            assert.ok(consoleContent.includes('Zm9vOmJhcixxd2VydHk6MTIzNA=='), '2 should log original text in console');
         }
         if (argsLength === 1 && consoleContent.includes('Decoded text content:')) {
-            assert.ok(consoleContent.includes('Decoded text content:'), 'log information about decoded content');
-            assert.ok(consoleContent.includes('foo:bar,qwerty:1234'), 'log information about decoded content');
+            assert.ok(consoleContent.includes('Decoded text content:'), '1 log information about decoded content');
+            assert.ok(consoleContent.includes('foo:bar,qwerty:1234'), '2 log information about decoded content');
         }
         if (argsLength === 1 && consoleContent.includes('Decoded text content was not modified')) {
             assert.ok(
@@ -227,7 +240,7 @@ test('log - Array.prototype.join, base64', (assert) => {
     const splittedText = textInBase64.split('');
     const result = splittedText.join('');
     const decodedResult = atob(result);
-    assert.deepEqual(result, expectedTextInBase64, 'Text content is intact');
-    assert.deepEqual(decodedResult, expectedText, 'Text content is intact');
+    assert.deepEqual(result, expectedTextInBase64, 'Encoded text content is intact');
+    assert.deepEqual(decodedResult, expectedText, 'Decoded text content is intact');
     assert.strictEqual(window.hit, 'FIRED', 'hit function fired');
 });