Fix: Malformed MKV could cause an infinite loop

ItalyPaleAle · sindresorhus · sindresorhus · commit 2c4d1200c99d · 2022-07-19T11:08:32.000+02:00
Co-authored-by: Sindre Sorhus &lt;sindresorhus@gmail.com&gt;
diff --git a/core.js b/core.js
@@ -654,7 +654,7 @@ class FileTypeParser {
 				let ic = 0; // 0 = A, 1 = B, 2 = C, 3
 				// = D
 
-				while ((msb & mask) === 0) {
+				while ((msb & mask) === 0 && mask !== 0) {
 					++ic;
 					mask >>= 1;
 				}
@@ -675,7 +675,7 @@ class FileTypeParser {
 				};
 			}
 
-			async function readChildren(level, children) {
+			async function readChildren(children) {
 				while (children > 0) {
 					const element = await readElement();
 					if (element.id === 0x42_82) {
@@ -689,7 +689,7 @@ class FileTypeParser {
 			}
 
 			const re = await readElement();
-			const docType = await readChildren(1, re.len);
+			const docType = await readChildren(re.len);
 
 			switch (docType) {
 				case 'webm':
diff --git a/fixture/fixture-corrupt.mkv b/fixture/fixture-corrupt.mkv
diff --git a/test.js b/test.js
@@ -614,3 +614,8 @@ test('supported files types are listed alphabetically', async t => {
 		currentNode = currentNode.next;
 	}
 });
+
+test('corrupt MKV throws', async t => {
+	const filePath = path.join(__dirname, 'fixture/fixture-corrupt.mkv');
+	await t.throwsAsync(fileTypeFromFile(filePath), {message: /out of range/});
+});

Original file line number	Diff line number	Diff line change
`@@ -614,3 +614,8 @@ test('supported files types are listed alphabetically', async t => {`
`614`	`614`	`currentNode = currentNode.next;`
`615`	`615`	`}`
`616`	`616`	`});`
	`617`	`+`
	`618`	`+test('corrupt MKV throws', async t => {`
	`619`	`+ const filePath = path.join(__dirname, 'fixture/fixture-corrupt.mkv');`
	`620`	`+ await t.throwsAsync(fileTypeFromFile(filePath), {message: /out of range/});`
	`621`	`+});`