fix(ntfs): reject malformed MFT update sequence arrays

Co-authored-by: gensokyo-dev <342580529+gensokyo-dev@users.noreply.github.com>

src/domain/windows/ntfsMft.test.ts

@@ -143,6 +143,28 @@ describe("parseMftImage", () => {
     );
   });
 
+  it.each([
+    [48, 4],
+    [49, 3],
+    [508, 3],
+  ])(
+    "rejects a malformed update sequence array at %i with %i entries",
+    (offset, count) => {
+      const bytes = recordOf();
+      const view = new DataView(bytes.buffer);
+      view.setUint16(4, offset, true);
+      view.setUint16(6, count, true);
+
+      const parsed = parseMftImage(bytes);
+      if (!parsed.ok) throw new Error(parsed.error.message);
+      expect(parsed.value.records[0]?.fixups).toMatchObject({
+        malformed: true,
+        verifiedSectors: 0,
+      });
+      expect(parsed.value.metadata.fixup_unverified_record_count).toBe(1);
+    },
+  );
+
   it("reports an array that covers fewer sectors than the record has", () => {
     // A 4 KiB record holds eight sectors; a three-entry array leaves five unverified.
     const parsed = parseMftImage(

src/domain/windows/ntfsMft.ts

@@ -323,13 +323,14 @@ const verifyFixups = (record: Uint8Array, view: DataView): MftRecordFixups => {
   const usaCount = view.getUint16(RECORD_HEADER.updateSequenceCount, true);
   const sectors = Math.floor(record.length / FIXUP_SECTOR_BYTES);
   // Entry 0 holds the sequence number, so sector n's saved trailer is entry n+1.
-  const coveredSectors = Math.min(sectors, Math.max(0, usaCount - 1));
+  const coveredSectors = Math.max(0, usaCount - 1);
 
   if (
     usaCount < USA_MIN_ENTRIES ||
+    coveredSectors > sectors ||
     usaOffset < RECORD_HEADER_BYTES ||
-    usaOffset + usaCount * 2 > record.length ||
-    coveredSectors === 0
+    usaOffset % 2 !== 0 ||
+    usaOffset + usaCount * 2 > FIXUP_SECTOR_BYTES - 2
   )
     return {
       sequenceNumber: 0,