feat(artifacts): inventory NTFS $MFT record headers offline

An acquired $MFT stream had no reader, so an analyst holding one could only
treat it as an opaque file. Recognize the FILE signature of the first record
and inventory every record's header: sequence number, flags, used and total
bytes, base record reference and update-sequence array.

Each record's update-sequence fixups are verified against its sector
trailers. A mismatch keeps the header facts, is reported on the record and is
counted in the metadata, so a record that was not cleanly written is visible
rather than silently accepted. A missing or short array is reported as
unverified, a wrong signature stops the scan at its offset, and a trailing
partial record is reported as a byte count. Attributes, filenames and the
$UsnJrnl:$J journal are not decoded, so no path or change history is claimed.

Part of #9867

(cherry picked from commit ccb45f5712)

docs/specs/README.md

@@ -26,6 +26,7 @@ for new work, roadmap granularity and producer-owned contracts.
 - [Native call source coordinates](native/call-source-locations/spec.md) ([plan](native/call-source-locations/plan.md), [tasks](native/call-source-locations/tasks.md), [verification](native/call-source-locations/verification.md))
 - [Go static string-header literal recovery](native/go-string-literals/spec.md) ([plan](native/go-string-literals/plan.md), [tasks](native/go-string-literals/tasks.md))
 - [Windows Shell Link shortcut inspection](native/windows-shortcut/spec.md) ([plan](native/windows-shortcut/plan.md), [tasks](native/windows-shortcut/tasks.md))
+- [NTFS $MFT and USN Journal inspection](native/ntfs-mft/spec.md) ([plan](native/ntfs-mft/plan.md), [tasks](native/ntfs-mft/tasks.md))
 - [Solidity terminal metadata inspection](solidity/cbor-metadata/spec.md) ([plan](solidity/cbor-metadata/plan.md), [tasks](solidity/cbor-metadata/tasks.md), [verification](solidity/cbor-metadata/verification.md))
 - [Inspect a V8 code cache container](v8/code-cache-inspection/spec.md) ([plan](v8/code-cache-inspection/plan.md), [tasks](v8/code-cache-inspection/tasks.md))
 - [Deno compile executable inventory and extraction](artifacts/deno-standalone/spec.md) ([plan](artifacts/deno-standalone/plan.md), [tasks](artifacts/deno-standalone/tasks.md))

docs/specs/native/ntfs-mft/plan.md

@@ -0,0 +1,39 @@
+# Implementation plan
+
+## Boundary and contract
+
+Follow the existing artifact readers. `src/domain/windows/ntfsMft.ts` owns FILE
+record bytes and coverage; `src/domain/artifactFormatMetadata.ts` owns the
+`ntfs-mft` result schema. `NtfsMftArtifactReader` reads the admitted file
+through `ArtifactFileSource` and exposes its facts through `formatMetadata()`.
+A record stream is its own content, so the root occurrence carries every fact
+and no members are enumerated.
+
+Recognition lives in `hasMftFileRecordSignature` and is applied in
+`classifyArtifactBytes`, next to the other unambiguous magic probes.
+
+## Incremental work and validation
+
+1. Define the first-step contract, limits and observations; add parser fixtures.
+2. Implement the FILE record header and update-sequence fixup parse with
+   explicit limitations.
+3. Add the reader, format descriptor and byte classification.
+4. Decode attribute records, then `$FILE_NAME` attributes so a record's parent
+   reference, names and timestamps become explicit; keep hard links separate.
+5. Parse `$UsnJrnl:$J` records and correlate them to records by full file
+   reference, including sequence numbers, reporting unresolved references.
+6. Document the workflow in a native Windows artifact guide.
+
+## Effects and compatibility
+
+The workflow reads one caller-selected local file. It adds no target execution,
+injection, mutation, protection recovery, network access, volume mount or live
+filesystem access, so no maintainer scope decision is required.
+`inspect_artifact` routing for every existing format is unchanged, and the new
+format id appears only for bytes whose first record carries the `FILE`
+signature.
+
+## References
+
+- https://learn.microsoft.com/en-us/windows/win32/fileio/master-file-table
+- https://github.com/libyal/libfsntfs/blob/main/documentation/New%20Technologies%20File%20System%20(NTFS).asciidoc

docs/specs/native/ntfs-mft/spec.md

@@ -0,0 +1,48 @@
+# NTFS $MFT and USN Journal inspection
+
+This specification records an implementation increment and its original problem
+statement. For current behavior and limitations, see the artifact inventory
+guide.
+
+## Problem and outcome
+
+REA has no reader for acquired NTFS metadata artifacts. An analyst holding a
+captured `$MFT` stream cannot ask which FILE records it contains, whether their
+update-sequence fixups survived acquisition, or which records are directories,
+extensions of another record, or no longer in use. Add offline, read-only
+inventory of a selected `$MFT` file, delivered in steps so each one merges on
+its own.
+
+## Requirements
+
+- Recognize a `$MFT` stream by the `FILE` signature of its first record, under
+  any file name, and route it to a dedicated artifact reader.
+- Validate each FILE record header: the `FILE` signature, sequence number, flags,
+  used and total byte counts, base record reference, and the update-sequence
+  array's offset, count and array bounds.
+- Verify the update-sequence fixups: every sector trailer the array covers must
+  hold the array's sequence number. A mismatch keeps the record's header facts
+  and is reported per record and in the metadata count.
+- Report a missing, misplaced or short update-sequence array as unverified
+  rather than as a clean record, and a trailing partial record as a byte count.
+- Stop at the first record that does not begin with the `FILE` signature and
+  name its offset, rather than guessing at the remaining bytes.
+- Bound the whole file at a fixed 512 MiB ceiling and report the ceiling as a
+  `limit` failure with its boundary.
+- Parse only the records' headers and fixups. Attributes, filenames, data
+  streams and the `$UsnJrnl:$J` journal are not decoded in this step, so no path,
+  file size, file reference correlation or change history is claimed.
+
+## Acceptance
+
+Synthesized fixtures cover a clean record, a failed fixup, a missing update
+sequence array, an array shorter than the record's sector count, extension and
+directory records, a record whose signature is wrong mid-stream, a trailing
+partial record, an undeclared record size, a 4 KiB record, a stream shorter than
+one header, bytes without the `FILE` signature, and the file-size ceiling.
+Inventory tests cover the root occurrence's metadata and the coverage status
+when a fixup fails, and classification tests cover several file names for the
+same bytes.
+
+Not covered in this step: real `$MFT` files written by a Windows host, USN
+journal records, attribute decoding, and any correlation between the two.

docs/specs/native/ntfs-mft/tasks.md

@@ -0,0 +1,11 @@
+# Tasks
+
+- [x] Define the first-step scope, contract and limits.
+- [x] Parse FILE record headers and update-sequence fixups with synthesized
+      fixtures and explicit limitations.
+- [x] Add the reader, format descriptor and byte classification.
+- [ ] Decode attribute records, then `$FILE_NAME` attributes with parent
+      references, names, hard links and timestamps.
+- [ ] Parse `$UsnJrnl:$J` records and correlate them to records by full file
+      reference.
+- [ ] Verify against real `$MFT` and journal captures from a Windows host.

src/artifacts/ArtifactReader.ts

@@ -215,6 +215,7 @@ export interface ArtifactReader {
     | "dfuse"
     | "esp-flash-image"
     | "fit"
+    | "ntfs-mft"
     | "file";
   entries(
     signal?: AbortSignal,

src/artifacts/NtfsMftArtifactReader.test.ts

@@ -0,0 +1,77 @@
+import { writeFile } from "node:fs/promises";
+import { join } from "node:path";
+
+import { expect, it } from "vitest";
+
+import { MFT_DEFAULT_RECORD_BYTES } from "../domain/windows/ntfsMft.js";
+import { createTestTempDirectory } from "../../tests/fixtures/temporaryDirectory.js";
+import { scanCanonicalArtifactInventory } from "../../tests/fixtures/artifactInventory.js";
+
+/** A 1 KiB FILE record whose update sequence array covers both sectors. */
+const recordBytes = (options: {
+  readonly sequenceNumber?: number;
+  readonly flags?: number;
+}): Buffer => {
+  const record = Buffer.alloc(MFT_DEFAULT_RECORD_BYTES);
+  record.write("FILE", 0, "latin1");
+  const sequenceNumber = options.sequenceNumber ?? 1;
+  record.writeUInt16LE(48, 4);
+  record.writeUInt16LE(3, 6);
+  record.writeUInt16LE(sequenceNumber, 48);
+  record.writeUInt16LE(0xa5a5, 50);
+  record.writeUInt16LE(0xa5a5, 52);
+  record.writeUInt16LE(sequenceNumber, 16);
+  record.writeUInt16LE(1, 18);
+  record.writeUInt16LE(56, 20);
+  record.writeUInt16LE(options.flags ?? 0x0001, 22);
+  record.writeUInt32LE(56, 24);
+  record.writeUInt32LE(MFT_DEFAULT_RECORD_BYTES, 28);
+  record.writeUInt16LE(sequenceNumber, 510);
+  record.writeUInt16LE(sequenceNumber, 1022);
+  return record;
+};
+
+const writeMft = async (name: string, bytes: Buffer): Promise<string> => {
+  const directory = await createTestTempDirectory("rea-ntfs-mft-");
+  const path = join(directory, name);
+  await writeFile(path, bytes);
+  return path;
+};
+
+it("reports a $MFT stream's record headers as the root occurrence", async () => {
+  const inventory = await scanCanonicalArtifactInventory(
+    await writeMft("$MFT", Buffer.concat([recordBytes({}), recordBytes({ flags: 0x0003 })])),
+  );
+  expect(inventory.manifest.root_format).toBe("ntfs-mft");
+  expect(inventory.coverage.status).toBe("complete");
+  // A record stream declares no members, so the root is its whole inventory.
+  expect(inventory.occurrences.map((row) => row.logical_path)).toEqual(["."]);
+  expect(inventory.occurrences[0]).toMatchObject({
+    artifact_format: "ntfs-mft",
+    format_metadata: {
+      kind: "ntfs-mft",
+      record_bytes: MFT_DEFAULT_RECORD_BYTES,
+      record_count: 2,
+      in_use_record_count: 2,
+      directory_record_count: 1,
+      extension_record_count: 0,
+      fixup_mismatch_count: 0,
+      fixup_unverified_record_count: 0,
+      truncated_tail_bytes: 0,
+    },
+  });
+});
+
+it("names a failed fixup in the coverage limitations", async () => {
+  const record = recordBytes({ sequenceNumber: 4 });
+  // A trailer that is not the sequence number marks the sector as not cleanly written.
+  record.writeUInt16LE(0x1234, 510);
+  const inventory = await scanCanonicalArtifactInventory(
+    await writeMft("$MFT", record),
+  );
+  expect(inventory.manifest.root_format).toBe("ntfs-mft");
+  expect(inventory.coverage.status).toBe("unknown");
+  expect(inventory.limitations).toContainEqual(
+    expect.stringMatching(/sector trailer that is not the update sequence/u),
+  );
+});

src/artifacts/NtfsMftArtifactReader.ts

@@ -0,0 +1,143 @@
+import type { Readable } from "node:stream";
+
+import type { ArtifactFormatMetadata } from "../domain/artifactFormatMetadata.js";
+import type { RegionDecodeFailure } from "../domain/firmware/regionDecoder.js";
+import {
+  createMftDecoder,
+  type MftImage,
+} from "../domain/windows/ntfsMft.js";
+import {
+  ArtifactReaderFailure,
+  type ArtifactEntry,
+  type ArtifactReader,
+  type ArtifactReaderTraversal,
+  type ArtifactTraversalOptions,
+} from "./ArtifactReader.js";
+import { ArtifactResourceScope } from "./ArtifactResourceScope.js";
+import { assertArtifactReadActive } from "./ArtifactFileOperation.js";
+import { ArtifactFileSource } from "./ArtifactFileSource.js";
+import { readFileHandleChunks } from "../filesystem/readFileHandleChunks.js";
+import type { StableRegularFileDescriptor } from "../filesystem/RegularFile.js";
+
+/**
+ * An MFT stream is its own content: the FILE records describe the source
+ * volume, not members inside the stream, so the root occurrence carries every
+ * fact and no entries are enumerated.
+ */
+export class NtfsMftArtifactReader implements ArtifactReader {
+  readonly format = "ntfs-mft" as const;
+  readonly #scope = new ArtifactResourceScope();
+  readonly #source: ArtifactFileSource;
+  #prepared: Promise<void> | undefined;
+  #metadata: ArtifactFormatMetadata | undefined;
+  #limitations: readonly string[] = [];
+  #closing = false;
+
+  constructor(path: string, admitted?: StableRegularFileDescriptor) {
+    this.#source = new ArtifactFileSource(path, "$MFT stream", admitted);
+  }
+
+  formatMetadata(): ArtifactFormatMetadata | undefined {
+    return this.#metadata === undefined ? undefined : { ...this.#metadata };
+  }
+
+  async prepareContainer(
+    expectedSha256: string,
+    signal?: AbortSignal,
+  ): Promise<void> {
+    await this.#scope.run(async () => {
+      this.#assertOpen(signal);
+      await this.#source.bindSha256(expectedSha256, signal);
+    });
+  }
+
+  async *entries(
+    signal?: AbortSignal,
+    options?: ArtifactTraversalOptions,
+  ): AsyncIterable<ArtifactEntry> {
+    await this.#scope.run(async () => {
+      this.#assertOpen(signal);
+      this.#prepared ??= this.#prepare(signal);
+      await this.#prepared;
+    });
+    // An MFT declares no members, so the root occurrence is the whole
+    // inventory; the coverage callback reports what its parse did not establish.
+    options?.onCoverage?.(coverageOf(this.#limitations));
+  }
+
+  async open(entry: ArtifactEntry, _signal?: AbortSignal): Promise<Readable> {
+    return this.#scope.run(async () => {
+      throw new ArtifactReaderFailure(
+        "unavailable",
+        `$MFT stream declares no member to open for ${entry.path}`,
+      );
+    });
+  }
+
+  async close(): Promise<void> {
+    this.#closing = true;
+    await this.#scope.close();
+    await this.#source.close();
+    this.#metadata = undefined;
+  }
+
+  provenance(): readonly [] {
+    return [];
+  }
+
+  #assertOpen(signal?: AbortSignal): void {
+    assertArtifactReadActive(signal);
+    if (this.#closing)
+      throw new ArtifactReaderFailure(
+        "unavailable",
+        "$MFT stream reader is closed",
+      );
+  }
+
+  async #prepare(signal?: AbortSignal): Promise<void> {
+    const image = await this.#decode(signal);
+    this.#metadata = image.metadata;
+    this.#limitations = image.limitations;
+    await this.#source.read(signal);
+  }
+
+  async #decode(signal?: AbortSignal): Promise<MftImage> {
+    const { handle, initial } = await this.#source.read(signal);
+    const decoder = createMftDecoder(initial.size);
+    if (!decoder.ok) throw this.#failure(decoder.error);
+    if (initial.size > 0)
+      for await (const chunk of readFileHandleChunks(handle, {
+        end: initial.size - 1,
+        signal,
+        cancellationFailure: (reason) =>
+          new ArtifactReaderFailure("cancelled", "$MFT stream read cancelled", {
+            cause: reason,
+          }),
+      }) as AsyncIterable<Buffer>) {
+        this.#assertOpen(signal);
+        const written = decoder.value.write(chunk);
+        if (!written.ok) throw this.#failure(written.error);
+      }
+    const image = decoder.value.finish();
+    if (!image.ok) throw this.#failure(image.error);
+    return image.value;
+  }
+
+  #failure(failure: RegionDecodeFailure): ArtifactReaderFailure {
+    return failure.kind === "format"
+      ? new ArtifactReaderFailure(
+          "format",
+          `$MFT stream is malformed: ${failure.message}`,
+        )
+      : new ArtifactReaderFailure(
+          "limit",
+          `$MFT stream exceeds a fixed limit: ${failure.message}`,
+          failure.boundary === undefined ? {} : { boundary: failure.boundary },
+        );
+  }
+}
+
+const coverageOf = (limitations: readonly string[]): ArtifactReaderTraversal =>
+  limitations.length === 0
+    ? { status: "complete", limitations: [] }
+    : { status: "unknown", limitations };

src/artifacts/artifactFormats.test.ts

@@ -43,7 +43,8 @@ type FormatsWithReaders =
   | "uf2"
   | "dfuse"
   | "esp-flash-image"
-  | "fit";
+  | "fit"
+  | "ntfs-mft";
 
 const readerFormatsMatch: Equal<ArtifactReaderFormat, FormatsWithReaders> =
   true;

src/artifacts/artifactFormats.ts

@@ -40,6 +40,7 @@ import { NodeSeaArtifactReader } from "./NodeSeaArtifactReader.js";
 import type { PyInstallerAdmission } from "./pyinstaller/PyInstallerAdmission.js";
 import { PyInstallerArtifactReader } from "./PyInstallerArtifactReader.js";
 import { Uf2ArtifactReader } from "./Uf2ArtifactReader.js";
+import { NtfsMftArtifactReader } from "./NtfsMftArtifactReader.js";
 import { UImageArtifactReader } from "./UImageArtifactReader.js";
 import { UnityFsArtifactReader } from "./UnityFsArtifactReader.js";
 import { WxapkgArtifactReader } from "./WxapkgArtifactReader.js";
@@ -465,6 +466,14 @@ const NON_ZIP_FORMATS = {
     createReader: (path, options) =>
       new FitArtifactReader(path, sourceOf(options)),
   }),
+  "ntfs-mft": described("ntfs-mft", {
+    ...plain,
+    retainClassifiedSource: true,
+    readerLimitation:
+      "MFT inventory reports each FILE record's header, flags, record extent and update-sequence fixup result. Attributes, filenames, data streams and the $UsnJrnl:$J journal are not decoded, so no path, file size or change history is established.",
+    createReader: (path, options) =>
+      new NtfsMftArtifactReader(path, sourceOf(options)),
+  }),
   unknown: described("unknown", plain),
 } satisfies Record<
   Exclude<ArtifactFormatId, ZipPackageFormat>,

src/artifacts/inventory/ArtifactGraphConstruction.test.ts

@@ -576,6 +576,16 @@ it("classifies nested UF2 by block magics and DfuSe by prefix and suffix", () =>
   ).toMatchObject({ format: "file" });
 });
 
+it("classifies a $MFT stream by its FILE record signature, under any name", () => {
+  const mft = Buffer.alloc(2_048);
+  mft.write("FILE", 0, "latin1");
+  for (const path of ["evidence/$MFT", "evidence/mft.raw", "evidence/records"])
+    expect(classifyArtifactBytesAtPath(path, mft)).toEqual({
+      kind: "executable",
+      format: "ntfs-mft",
+    });
+});
+
 it("classifies a FIT by a /images node within the first 4 KiB", () => {
   const images = [{ name: "kernel", data: Buffer.from("kernel") }];
   const late = devicetreeFixture({

src/artifacts/inventory/ArtifactGraphConstruction.ts

@@ -11,6 +11,7 @@ import { recognizeEspImage } from "../../domain/firmware/espImage.js";
 import { hasUf2Block } from "../../domain/firmware/uf2.js";
 import { isDfuSeFile } from "../../domain/firmware/dfuse.js";
 import { hasFitImagesNode } from "../../domain/firmware/fitImage.js";
+import { hasMftFileRecordSignature } from "../../domain/windows/ntfsMft.js";
 import type { ArtifactClassificationEvidence } from "../ArtifactClassificationProbe.js";
 import { asarHeaderAdmissionFailure } from "../AsarHeader.js";
 import { hasDestinationPath } from "../ArtifactPaths.js";
@@ -622,6 +623,7 @@ export const classifyArtifactBytes = (
     return "dfuse";
   if (recognizeEspImage(prefix, fileSize) === "esp-image") return "esp-image";
   if (hasFitImagesNode(prefix)) return "fit";
+  if (hasMftFileRecordSignature(prefix)) return "ntfs-mft";
   if (hasBinaryPlistSignature(prefix)) return "plist";
   if (hasXmlPlistSignature(prefix)) return "plist";
   const fatFormat = classifyFatArtifact(evidence, fileSize);

src/domain/artifactFormatMetadata.ts

@@ -299,6 +299,19 @@ export const hexRecordRegionMetadataSchema = z.strictObject({
   last_line: offset,
 });
 
+/** NTFS $MFT record-header facts; attributes, names and the USN journal are later steps. */
+export const ntfsMftMetadataSchema = z.strictObject({
+  kind: z.literal("ntfs-mft"),
+  record_bytes: offset,
+  record_count: offset,
+  in_use_record_count: offset,
+  directory_record_count: offset,
+  extension_record_count: offset,
+  fixup_mismatch_count: offset,
+  fixup_unverified_record_count: offset,
+  truncated_tail_bytes: offset,
+});
+
 /**
  * U-Boot FIT root facts. Configuration references are declared names; a
  * reference that names no image is reported as a limitation, not removed.
@@ -886,6 +899,7 @@ export const artifactFormatMetadataSchema = z.discriminatedUnion("kind", [
   espImageSignatureBlockMetadataSchema,
   uf2MetadataSchema,
   uf2RegionMetadataSchema,
+  ntfsMftMetadataSchema,
   dfuSeMetadataSchema,
   dfuSeElementMetadataSchema,
   espFlashImageMetadataSchema,
@@ -1036,6 +1050,10 @@ const declarationsByKind: {
     notCompared:
       "Its familyID and addresses are in its path, family_name is REA's label for the familyID, and its block counts and positions are layout; content comparison covers its bytes.",
   },
+  "ntfs-mft": {
+    notCompared:
+      "Its fields come from the record headers in the file's own FILE records, which content comparison covers.",
+  },
   dfuse: {
     notCompared:
       "Its fields come from the file's own prefix, target headers and suffix, which content comparison covers.",

src/domain/artifactGraph.ts

@@ -103,6 +103,7 @@ export const ARTIFACT_FORMAT_IDS = [
   "dfuse",
   "esp-flash-image",
   "fit",
+  "ntfs-mft",
   "unknown",
 ] as const;
 
@@ -124,6 +125,7 @@ const artifactContentFormatSchema = artifactFormatSchema.extract([
   "uf2",
   "dfuse",
   "fit",
+  "ntfs-mft",
   "mach-o-universal",
   "mach-o",
   "elf",

src/domain/evidenceSubject.ts

@@ -52,6 +52,7 @@ export const evidenceSubjectFormatSchema = z.enum([
   "dfuse",
   "esp-flash-image",
   "fit",
+  "ntfs-mft",
 ]);
 
 /** Format-owned architecture declarations shared by Evidence and persisted executions. */

src/domain/windows/ntfsMft.test.ts

@@ -0,0 +1,276 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  MFT_DEFAULT_RECORD_BYTES,
+  MFT_MAX_FILE_BYTES,
+  createMftDecoder,
+  parseMftImage,
+} from "./ntfsMft.js";
+
+interface RecordOptions {
+  readonly sequenceNumber?: number;
+  readonly hardLinkCount?: number;
+  readonly flags?: number;
+  readonly baseRecordReference?: bigint;
+  readonly recordBytes?: number;
+  /** Write a wrong trailer value into this sector, leaving the others correct. */
+  readonly corruptSector?: number;
+  /** Truncate the update sequence array to this many entries; 0 omits it. */
+  readonly usaEntries?: number;
+}
+
+/** One FILE record with a zeroed body and fixups applied the way NTFS writes them. */
+const recordOf = (options: RecordOptions = {}): Uint8Array => {
+  const recordBytes = options.recordBytes ?? MFT_DEFAULT_RECORD_BYTES;
+  const record = new Uint8Array(recordBytes);
+  const view = new DataView(record.buffer);
+  record.set(Buffer.from("FILE", "latin1"), 0);
+  const sequenceNumber = options.sequenceNumber ?? 1;
+  const sectors = recordBytes / 512;
+
+  const usaEntries = options.usaEntries ?? sectors + 1;
+  if (usaEntries > 0) {
+    const usaOffset = 48;
+    view.setUint16(4, usaOffset, true);
+    view.setUint16(6, usaEntries, true);
+    view.setUint16(usaOffset, sequenceNumber, true);
+    for (let sector = 0; sector < sectors; sector += 1) {
+      const trailer = sector * 512 + 510;
+      // A saved trailer is what the sector held before the fixup replaced it.
+      view.setUint16(usaOffset + 2 * (sector + 1), 0xa5a5, true);
+      view.setUint16(
+        trailer,
+        sector >= usaEntries - 1
+          ? 0xa5a5
+          : sector === options.corruptSector
+            ? 0x1234
+            : sequenceNumber,
+        true,
+      );
+    }
+  } else {
+    view.setUint16(4, 0, true);
+    view.setUint16(6, 0, true);
+  }
+
+  view.setUint16(16, sequenceNumber, true);
+  view.setUint16(18, options.hardLinkCount ?? 1, true);
+  view.setUint16(20, 56, true);
+  view.setUint16(22, options.flags ?? 0x0001, true);
+  view.setUint32(24, 56, true);
+  view.setUint32(28, recordBytes, true);
+  view.setBigUint64(32, options.baseRecordReference ?? 0n, true);
+  view.setUint16(40, 0, true);
+  return record;
+};
+
+const streamOf = (...records: readonly Uint8Array[]): Uint8Array => {
+  const total = records.reduce((sum, record) => sum + record.length, 0);
+  const stream = new Uint8Array(total);
+  let offset = 0;
+  for (const record of records) {
+    stream.set(record, offset);
+    offset += record.length;
+  }
+  return stream;
+};
+
+describe("parseMftImage", () => {
+  it("inventories a clean record's header and verified fixups", () => {
+    const parsed = parseMftImage(streamOf(recordOf({ sequenceNumber: 5 })));
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.metadata).toEqual({
+      kind: "ntfs-mft",
+      record_bytes: MFT_DEFAULT_RECORD_BYTES,
+      record_count: 1,
+      in_use_record_count: 1,
+      directory_record_count: 0,
+      extension_record_count: 0,
+      fixup_mismatch_count: 0,
+      fixup_unverified_record_count: 0,
+      truncated_tail_bytes: 0,
+    });
+    expect(parsed.value.records[0]).toMatchObject({
+      index: 0,
+      fileOffset: 0,
+      sequenceNumber: 5,
+      inUse: true,
+      directory: false,
+      baseRecordReference: null,
+      firstAttributeOffset: 56,
+      fixups: {
+        sequenceNumber: 5,
+        verifiedSectors: 2,
+        coveredSectors: 2,
+        mismatchSector: null,
+        malformed: false,
+      },
+    });
+    expect(parsed.value.limitations).toEqual([]);
+  });
+
+  it("keeps a record whose sector trailer is not the sequence number, and reports it", () => {
+    const parsed = parseMftImage(
+      streamOf(
+        recordOf(),
+        recordOf({ sequenceNumber: 9, corruptSector: 1 }),
+      ),
+    );
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.records[1]?.fixups).toMatchObject({
+      sequenceNumber: 9,
+      verifiedSectors: 1,
+      mismatchSector: 1,
+    });
+    expect(parsed.value.metadata.fixup_mismatch_count).toBe(1);
+    expect(parsed.value.limitations.join(" ")).toMatch(
+      /1 record\(s\) hold a sector trailer/u,
+    );
+  });
+
+  it("treats a missing update sequence array as unverified rather than clean", () => {
+    const parsed = parseMftImage(streamOf(recordOf({ usaEntries: 0 })));
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.records[0]?.fixups).toMatchObject({
+      malformed: true,
+      mismatchSector: null,
+      coveredSectors: 0,
+    });
+    expect(parsed.value.metadata.fixup_mismatch_count).toBe(0);
+    expect(parsed.value.metadata.fixup_unverified_record_count).toBe(1);
+    expect(parsed.value.limitations.join(" ")).toMatch(
+      /update sequence array that does not cover every sector/u,
+    );
+  });
+
+  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(
+      streamOf(recordOf({ recordBytes: 4096, usaEntries: 3 })),
+    );
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.records[0]?.fixups).toMatchObject({
+      coveredSectors: 2,
+      verifiedSectors: 2,
+      mismatchSector: null,
+      malformed: false,
+    });
+    expect(parsed.value.metadata.fixup_unverified_record_count).toBe(1);
+  });
+
+  it("distinguishes extension records from base records", () => {
+    const parsed = parseMftImage(
+      streamOf(
+        recordOf(),
+        recordOf({ flags: 0x0005, baseRecordReference: 0x0000000000000001n }),
+      ),
+    );
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.records[1]).toMatchObject({
+      baseRecordReference: 1,
+      flags: { raw: 0x0005, names: ["in-use", "extension"] },
+    });
+    expect(parsed.value.metadata.extension_record_count).toBe(1);
+  });
+
+  it("names directory records without losing the in-use flag", () => {
+    const parsed = parseMftImage(streamOf(recordOf({ flags: 0x0003 })));
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.records[0]).toMatchObject({
+      directory: true,
+      inUse: true,
+      flags: { names: ["in-use", "directory"] },
+    });
+    expect(parsed.value.metadata.directory_record_count).toBe(1);
+  });
+
+  it("stops at a record that does not begin with the FILE signature", () => {
+    const stream = streamOf(recordOf(), recordOf(), recordOf());
+    stream.set(Buffer.from("BAAD", "latin1"), 1024);
+    const parsed = parseMftImage(stream);
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.metadata.record_count).toBe(1);
+    expect(parsed.value.limitations.join(" ")).toMatch(
+      /record at 1024 does not begin with the FILE signature/u,
+    );
+  });
+
+  it("keeps a trailing partial record out of the inventory", () => {
+    const stream = new Uint8Array(1024 + 300);
+    stream.set(recordOf(), 0);
+    const parsed = parseMftImage(stream);
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.metadata.record_count).toBe(1);
+    expect(parsed.value.metadata.truncated_tail_bytes).toBe(300);
+    expect(parsed.value.limitations.join(" ")).toMatch(
+      /300 trailing byte\(s\)/u,
+    );
+  });
+
+  it("falls back to the default record size when record 0 declares none", () => {
+    const record = recordOf();
+    new DataView(record.buffer).setUint32(28, 0, true);
+    const parsed = parseMftImage(record);
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.recordBytes).toBe(MFT_DEFAULT_RECORD_BYTES);
+    expect(parsed.value.limitations.join(" ")).toMatch(
+      /not a supported power of two/u,
+    );
+  });
+
+  it("reads a 4 KiB record at its declared size", () => {
+    const parsed = parseMftImage(streamOf(recordOf({ recordBytes: 4096 })));
+    expect(parsed.ok).toBe(true);
+    if (!parsed.ok) return;
+    expect(parsed.value.recordBytes).toBe(4096);
+    expect(parsed.value.metadata.record_count).toBe(1);
+  });
+
+});
+
+describe("parseMftImage refusals and limits", () => {
+  it("refuses a file shorter than one record header", () => {
+    const parsed = parseMftImage(new Uint8Array(32));
+    expect(parsed.ok).toBe(false);
+    if (parsed.ok) return;
+    expect(parsed.error.message).toMatch(/shorter than one 48-byte record header/u);
+  });
+
+  it("refuses bytes that do not start with the FILE signature", () => {
+    const parsed = parseMftImage(Buffer.alloc(2048, 0x41));
+    expect(parsed.ok).toBe(false);
+    if (parsed.ok) return;
+    expect(parsed.error.message).toMatch(/does not begin with the FILE signature/u);
+  });
+
+  it("refuses a file above the fixed ceiling", () => {
+    const decoder = createMftDecoder(MFT_MAX_FILE_BYTES + 1);
+    expect(decoder.ok).toBe(false);
+    if (decoder.ok) return;
+    expect(decoder.error).toMatchObject({ kind: "limit", boundary: "file-size" });
+  });
+
+  it("decodes the same stream through the chunked decoder", () => {
+    const stream = streamOf(recordOf(), recordOf({ flags: 0x0003 }));
+    const decoder = createMftDecoder(stream.length);
+    expect(decoder.ok).toBe(true);
+    if (!decoder.ok) return;
+    // Feed one byte past a record boundary so a chunk never aligns with a record.
+    for (const chunk of [stream.subarray(0, 1025), stream.subarray(1025)])
+      expect(decoder.value.write(chunk).ok).toBe(true);
+    const image = decoder.value.finish();
+    expect(image.ok).toBe(true);
+    if (!image.ok) return;
+    expect(image.value.metadata.record_count).toBe(2);
+    expect(image.value.metadata.directory_record_count).toBe(1);
+  });
+});

src/domain/windows/ntfsMft.ts

@@ -0,0 +1,385 @@
+import { err, ok, type Result } from "../result.js";
+import type {
+  RegionDecodeFailure,
+  RegionDecoder,
+} from "../firmware/regionDecoder.js";
+
+/** An NTFS FILE record begins with this signature. */
+export const MFT_FILE_RECORD_MAGIC = "FILE";
+export const MFT_FILE_RECORD_MAGIC_BYTES = 4;
+/** The shortest header worth reading: a FILE record header ends at `nextAttributeId`. */
+export const NTFS_MFT_MIN_RECORD_BYTES = 48;
+
+/**
+ * The `FILE` signature at file offset 0. An MFT stream is a run of fixed-size
+ * FILE records, so the first record's signature is the recognition fact;
+ * whether every record parses is the reader's question, not classification's.
+ */
+export const hasMftFileRecordSignature = (prefix: Uint8Array): boolean =>
+  prefix.length >= MFT_FILE_RECORD_MAGIC_BYTES &&
+  text(prefix.subarray(0, MFT_FILE_RECORD_MAGIC_BYTES)) ===
+    MFT_FILE_RECORD_MAGIC;
+
+/** A record's declared size is a power of two from 512 upward; 1024 is NTFS's default. */
+export const MFT_DEFAULT_RECORD_BYTES = 1024;
+const MFT_MIN_RECORD_BYTES = 512;
+const MFT_MAX_RECORD_BYTES = 65536;
+/** An update sequence array holds at least the sequence number and one fixup word. */
+const USA_MIN_ENTRIES = 2;
+/** NTFS fixes up one 512-byte sector at a time. */
+const FIXUP_SECTOR_BYTES = 512;
+/**
+ * Fixed whole-file ceiling. Records are inventoried from their headers only;
+ * attributes and their payloads are not decoded, so this is deliberately
+ * smaller than a volume's MFT can be.
+ */
+export const MFT_MAX_FILE_BYTES = 512 * 1024 * 1024;
+
+/** FILE record header fields; offsets are from the record start. */
+const RECORD_HEADER = {
+  updateSequenceOffset: 4,
+  updateSequenceCount: 6,
+  logFileSequenceNumber: 8,
+  sequenceNumber: 16,
+  hardLinkCount: 18,
+  firstAttributeOffset: 20,
+  flags: 22,
+  usedBytes: 24,
+  totalBytes: 28,
+  baseRecordReference: 32,
+  nextAttributeId: 40,
+  recordNumber: 44,
+} as const;
+const RECORD_HEADER_BYTES = NTFS_MFT_MIN_RECORD_BYTES;
+
+const FILE_RECORD_IN_USE = 0x0001;
+const FILE_RECORD_IS_DIRECTORY = 0x0002;
+const FILE_RECORD_NAMES = new Map<number, string>([
+  [FILE_RECORD_IN_USE, "in-use"],
+  [FILE_RECORD_IS_DIRECTORY, "directory"],
+  [0x0004, "extension"],
+  [0x0008, "view-index"],
+]);
+
+export interface MftRecordFixups {
+  /** The update sequence number the array's first entry holds, or 0 when absent. */
+  readonly sequenceNumber: number;
+  readonly entries: number;
+  /** Sectors whose trailer held the sequence number before a mismatch. */
+  readonly verifiedSectors: number;
+  /** Sectors the array covers; fewer than the record's sectors leaves a tail unverified. */
+  readonly coveredSectors: number;
+  /** The first sector whose trailer did not hold the sequence number, if any. */
+  readonly mismatchSector: number | null;
+  /** The array itself is missing, misplaced or too short to cover one sector. */
+  readonly malformed: boolean;
+}
+
+export interface MftRecord {
+  /** Zero-based ordinal of this record in the stream. */
+  readonly index: number;
+  /** File offset where the record starts. */
+  readonly fileOffset: number;
+  readonly sequenceNumber: number;
+  /** Hard link count as recorded; a zero count marks a record with no names. */
+  readonly hardLinkCount: number;
+  readonly flags: { readonly raw: number; readonly names: readonly string[] };
+  readonly inUse: boolean;
+  readonly directory: boolean;
+  /** Bytes the record claims it uses, and the record size it was parsed at. */
+  readonly usedBytes: number;
+  readonly totalBytes: number;
+  /** The base record this is an extension of, or `null` for a base record. */
+  readonly baseRecordReference: number | null;
+  /** The record number the header declares; `null` when the header predates the field. */
+  readonly declaredRecordNumber: number | null;
+  /** `$LogFile` sequence number as recorded; no log is read. */
+  readonly logFileSequenceNumber: number;
+  /** Declared offset of the first attribute; no attribute decoding follows yet. */
+  readonly firstAttributeOffset: number;
+  /** Declared id of the next attribute; no attribute decoding follows yet. */
+  readonly nextAttributeId: number;
+  readonly fixups: MftRecordFixups;
+}
+
+export interface MftImage {
+  readonly metadata: MftMetadata;
+  /** The record size the stream declared, or the fixed default when it did not. */
+  readonly recordBytes: number;
+  readonly records: readonly MftRecord[];
+  readonly limitations: readonly string[];
+}
+
+export interface MftMetadata {
+  readonly kind: "ntfs-mft";
+  readonly record_bytes: number;
+  readonly record_count: number;
+  readonly in_use_record_count: number;
+  readonly directory_record_count: number;
+  readonly extension_record_count: number;
+  readonly fixup_mismatch_count: number;
+  readonly fixup_unverified_record_count: number;
+  readonly truncated_tail_bytes: number;
+}
+
+const text = (ascii: Uint8Array): string =>
+  Buffer.from(ascii).toString("latin1");
+
+const failure = (
+  message: string,
+  boundary?: RegionDecodeFailure["boundary"],
+): RegionDecodeFailure => ({
+  kind: "format",
+  message,
+  ...(boundary === undefined ? {} : { boundary }),
+});
+
+const limit = (
+  message: string,
+  boundary?: RegionDecodeFailure["boundary"],
+): RegionDecodeFailure => ({
+  kind: "limit",
+  message,
+  ...(boundary === undefined ? {} : { boundary }),
+});
+
+const namesOf = (raw: number): readonly string[] => {
+  const names: string[] = [];
+  for (const [bit, name] of FILE_RECORD_NAMES)
+    if ((raw & bit) !== 0) names.push(name);
+  return names;
+};
+
+const isRecordSize = (bytes: number): boolean =>
+  bytes >= MFT_MIN_RECORD_BYTES &&
+  bytes <= MFT_MAX_RECORD_BYTES &&
+  (bytes & (bytes - 1)) === 0;
+
+/**
+ * Parse FILE record headers and verify their update-sequence fixups.
+ *
+ * Only the record structure is established: attributes, their names, the
+ * filenames and the USN journal are left to later steps, so no path, timestamp
+ * or file identity beyond the record itself is claimed. A record whose fixup
+ * does not match keeps its header facts, because the stream still declares it,
+ * and the mismatch is reported on the record and counted in the metadata.
+ */
+export const parseMftImage = (
+  bytes: Uint8Array,
+): Result<MftImage, RegionDecodeFailure> => {
+  if (bytes.length < NTFS_MFT_MIN_RECORD_BYTES)
+    return err(
+      failure(
+        `file is ${String(bytes.length)} bytes, shorter than one ${String(NTFS_MFT_MIN_RECORD_BYTES)}-byte record header`,
+      ),
+    );
+  if (!hasMftFileRecordSignature(bytes))
+    return err(failure("record 0 does not begin with the FILE signature"));
+
+  const limitations: string[] = [];
+  const header = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
+  const declaredRecordBytes = header.getUint32(RECORD_HEADER.totalBytes, true);
+  const recordBytes = isRecordSize(declaredRecordBytes)
+    ? declaredRecordBytes
+    : MFT_DEFAULT_RECORD_BYTES;
+  if (!isRecordSize(declaredRecordBytes))
+    limitations.push(
+      `record 0 declares a record size of ${String(declaredRecordBytes)} bytes, which is not a supported power of two from ${String(MFT_MIN_RECORD_BYTES)} to ${String(MFT_MAX_RECORD_BYTES)}; records were read at the ${String(MFT_DEFAULT_RECORD_BYTES)}-byte default`,
+    );
+
+  const records: MftRecord[] = [];
+  for (
+    let offset = 0;
+    offset + recordBytes <= bytes.length;
+    offset += recordBytes
+  ) {
+    if (
+      text(bytes.subarray(offset, offset + MFT_FILE_RECORD_MAGIC_BYTES)) !==
+      MFT_FILE_RECORD_MAGIC
+    ) {
+      limitations.push(
+        `record at ${String(offset)} does not begin with the FILE signature; ${String(records.length)} record(s) were examined`,
+      );
+      break;
+    }
+    records.push(readRecord(bytes, offset, records.length, recordBytes));
+  }
+
+  const truncatedTailBytes = bytes.length % recordBytes;
+  if (truncatedTailBytes !== 0)
+    limitations.push(
+      `${String(truncatedTailBytes)} trailing byte(s) do not fill a ${String(recordBytes)}-byte record and were not parsed`,
+    );
+
+  const mismatchCount = records.filter(
+    (record) => record.fixups.mismatchSector !== null,
+  ).length;
+  if (mismatchCount !== 0)
+    limitations.push(
+      `${String(mismatchCount)} record(s) hold a sector trailer that is not the update sequence number; their attributes were not read and no later step should trust them`,
+    );
+  const unverifiedCount = records.filter(
+    (record) =>
+      record.fixups.mismatchSector === null &&
+      (record.fixups.malformed ||
+        record.fixups.coveredSectors < recordBytes / FIXUP_SECTOR_BYTES),
+  ).length;
+  if (unverifiedCount !== 0)
+    limitations.push(
+      `${String(unverifiedCount)} record(s) carry an update sequence array that does not cover every sector; those trailers were neither restored nor verified`,
+    );
+
+  const metadata: MftMetadata = {
+    kind: "ntfs-mft",
+    record_bytes: recordBytes,
+    record_count: records.length,
+    in_use_record_count: records.filter((record) => record.inUse).length,
+    directory_record_count: records.filter((record) => record.directory).length,
+    extension_record_count: records.filter(
+      (record) => record.baseRecordReference !== null,
+    ).length,
+    fixup_mismatch_count: mismatchCount,
+    fixup_unverified_record_count: unverifiedCount,
+    truncated_tail_bytes: truncatedTailBytes,
+  };
+
+  return ok({ metadata, recordBytes, records, limitations });
+};
+
+const readRecord = (
+  bytes: Uint8Array,
+  fileOffset: number,
+  index: number,
+  recordBytes: number,
+): MftRecord => {
+  const record = bytes.subarray(fileOffset, fileOffset + recordBytes);
+  const view = new DataView(record.buffer, record.byteOffset, record.byteLength);
+
+  const flags = view.getUint16(RECORD_HEADER.flags, true);
+  const baseRecordReference = view.getBigUint64(
+    RECORD_HEADER.baseRecordReference,
+    true,
+  );
+
+  return {
+    index,
+    fileOffset,
+    sequenceNumber: view.getUint16(RECORD_HEADER.sequenceNumber, true),
+    hardLinkCount: view.getUint16(RECORD_HEADER.hardLinkCount, true),
+    flags: { raw: flags, names: namesOf(flags) },
+    inUse: (flags & FILE_RECORD_IN_USE) !== 0,
+    directory: (flags & FILE_RECORD_IS_DIRECTORY) !== 0,
+    usedBytes: view.getUint32(RECORD_HEADER.usedBytes, true),
+    totalBytes: view.getUint32(RECORD_HEADER.totalBytes, true),
+    baseRecordReference:
+      baseRecordReference === 0n
+        ? null
+        : Number(baseRecordReference & 0xffff_ffff_ffffn),
+    declaredRecordNumber:
+      recordBytes >= RECORD_HEADER.recordNumber + 4
+        ? view.getUint32(RECORD_HEADER.recordNumber, true)
+        : null,
+    logFileSequenceNumber: Number(
+      view.getBigUint64(RECORD_HEADER.logFileSequenceNumber, true),
+    ),
+    firstAttributeOffset: view.getUint16(
+      RECORD_HEADER.firstAttributeOffset,
+      true,
+    ),
+    nextAttributeId: view.getUint16(RECORD_HEADER.nextAttributeId, true),
+    fixups: verifyFixups(record, view),
+  };
+};
+
+/**
+ * Each sector's last two bytes are replaced on disk by the update sequence
+ * number; the array's first entry is that number and the rest are the saved
+ * trailer words. A sector whose trailer is not the sequence number was not
+ * cleanly written, so the record's attributes cannot be trusted.
+ */
+const verifyFixups = (
+  record: Uint8Array,
+  view: DataView,
+): MftRecordFixups => {
+  const usaOffset = view.getUint16(RECORD_HEADER.updateSequenceOffset, true);
+  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));
+
+  if (
+    usaCount < USA_MIN_ENTRIES ||
+    usaOffset < RECORD_HEADER_BYTES ||
+    usaOffset + usaCount * 2 > record.length ||
+    coveredSectors === 0
+  )
+    return {
+      sequenceNumber: 0,
+      entries: usaCount,
+      verifiedSectors: 0,
+      coveredSectors: 0,
+      mismatchSector: null,
+      malformed: true,
+    };
+
+  const sequenceNumber = view.getUint16(usaOffset, true);
+  for (let sector = 0; sector < coveredSectors; sector += 1) {
+    const trailerOffset = sector * FIXUP_SECTOR_BYTES + FIXUP_SECTOR_BYTES - 2;
+    if (view.getUint16(trailerOffset, true) !== sequenceNumber)
+      return {
+        sequenceNumber,
+        entries: usaCount,
+        verifiedSectors: sector,
+        coveredSectors,
+        mismatchSector: sector,
+        malformed: false,
+      };
+  }
+
+  return {
+    sequenceNumber,
+    entries: usaCount,
+    verifiedSectors: coveredSectors,
+    coveredSectors,
+    mismatchSector: null,
+    malformed: false,
+  };
+};
+
+/** Streaming form of the same parse: the whole admitted file is buffered once. */
+class StreamingMftDecoder implements RegionDecoder<MftImage> {
+  readonly #chunks: Uint8Array[] = [];
+  #length = 0;
+
+  constructor(readonly fileBytes: number) {}
+
+  write(chunk: Uint8Array): Result<void, RegionDecodeFailure> {
+    this.#chunks.push(chunk);
+    this.#length += chunk.length;
+    return ok(undefined);
+  }
+
+  finish(): Result<MftImage, RegionDecodeFailure> {
+    const bytes = new Uint8Array(this.#length);
+    let written = 0;
+    for (const chunk of this.#chunks) {
+      bytes.set(chunk, written);
+      written += chunk.length;
+    }
+    return parseMftImage(bytes);
+  }
+}
+
+export const createMftDecoder = (
+  fileBytes: number,
+): Result<RegionDecoder<MftImage>, RegionDecodeFailure> =>
+  Number.isSafeInteger(fileBytes) &&
+  fileBytes >= 0 &&
+  fileBytes <= MFT_MAX_FILE_BYTES
+    ? ok(new StreamingMftDecoder(fileBytes))
+    : err(
+        limit(
+          `file is ${String(fileBytes)} bytes, exceeding the fixed ${String(MFT_MAX_FILE_BYTES)}-byte (512 MiB) ceiling`,
+          "file-size",
+        ),
+      );