Merge pull request #34 from Touffy/fix-small-files-with-large-offsets

Fix Zip64 header for small files with large offsets

CHANGES.md

@@ -1,3 +1,8 @@
+## 2.0.1:
+
+* Fixed a bug where small files requiring a 64-bit offset (but not size) were corrupted.
+* Never use 64-bit sizes in data descriptor for small files, even at large offsets.
+
 ## 2.0.0:
 
 * breaking: now targets ES2020 because we need BigInts, because…

src/zip.ts

@@ -7,12 +7,13 @@ const fileHeaderSignature = 0x504b_0304, fileHeaderLength = 30
 const descriptorSignature = 0x504b_0708, descriptorLength = 16
 const centralHeaderSignature = 0x504b_0102, centralHeaderLength = 46
 const endSignature = 0x504b_0506, endLength = 22
-const zip64HeaderLength = 28
 const zip64endRecordSignature = 0x504b_0606, zip64endRecordLength = 56
 const zip64endLocatorSignature = 0x504b_0607, zip64endLocatorLength = 20
 
 export type ForAwaitable<T> = AsyncIterable<T> | Iterable<T>
 
+type Zip64FieldLength = 0 | 12 | 28
+
 export async function* loadFiles(files: ForAwaitable<ZipFileDescription>) {
   const centralRecord: Uint8Array[] = []
   let offset = 0n
@@ -24,18 +25,18 @@ export async function* loadFiles(files: ForAwaitable<ZipFileDescription>) {
     yield fileHeader(file)
     yield file.encodedName
     yield* fileData(file)
-    const fileNeedsZip64 = file.uncompressedSize! >= 0xffffffffn || offset >= 0xffffffffn
-    yield dataDescriptor(file, fileNeedsZip64)
-
-    centralRecord.push(centralHeader(file, offset, fileNeedsZip64))
+    const bigFile = file.uncompressedSize! >= 0xffffffffn
+    const bigOffset = offset >= 0xffffffffn
+    const zip64HeaderLength = (+bigOffset * 12 | +bigFile * 28) as Zip64FieldLength
+    yield dataDescriptor(file, bigFile)
+
+    centralRecord.push(centralHeader(file, offset, zip64HeaderLength))
     centralRecord.push(file.encodedName)
-    if (fileNeedsZip64) {
-      centralRecord.push(zip64ExtraField(file, offset))
-      offset += 8n
-    }
+    if (zip64HeaderLength) centralRecord.push(zip64ExtraField(file, offset, zip64HeaderLength))
+    if (bigFile) offset += 8n // because the data descriptor will have 64-bit sizes
     fileCount++
     offset += BigInt(fileHeaderLength + descriptorLength + file.encodedName.length) + file.uncompressedSize!
-    archiveNeedsZip64 ||= fileNeedsZip64
+    archiveNeedsZip64 ||= bigFile
   }
 
   // write central repository
@@ -123,7 +124,7 @@ export function dataDescriptor(file: ZipFileDescription, needsZip64: boolean) {
   return makeUint8Array(header)
 }
 
-export function centralHeader(file: ZipFileDescription, offset: bigint, needsZip64: boolean) {
+export function centralHeader(file: ZipFileDescription, offset: bigint, zip64HeaderLength: Zip64FieldLength = 0) {
   const header = makeBuffer(centralHeaderLength)
   header.setUint32(0, centralHeaderSignature)
   header.setUint32(4, 0x2d03_2d_00) // UNIX app version 4.5 | ZIP version 4.5
@@ -134,20 +135,22 @@ export function centralHeader(file: ZipFileDescription, offset: bigint, needsZip
   header.setUint32(20, clampInt32(file.uncompressedSize!), true)
   header.setUint32(24, clampInt32(file.uncompressedSize!), true)
   header.setUint16(28, file.encodedName.length, true)
-  header.setUint16(30, needsZip64 ? zip64HeaderLength : 0, true)
+  header.setUint16(30, zip64HeaderLength, true)
   // useless disk fields = zero (4 bytes)
   // useless attributes = zero (4 bytes)
   header.setUint16(40, 0o100664, true) // UNIX regular file, permissions 664
   header.setUint32(42, clampInt32(offset), true) // offset
   return makeUint8Array(header)
 }
 
-export function zip64ExtraField(file: ZipFileDescription, offset: bigint) {
+export function zip64ExtraField(file: ZipFileDescription, offset: bigint, zip64HeaderLength: Exclude<Zip64FieldLength, 0>) {
   const header = makeBuffer(zip64HeaderLength)
   header.setUint16(0, 1, true)
   header.setUint16(2, zip64HeaderLength - 4, true)
-  header.setBigUint64(4, file.uncompressedSize!, true)
-  header.setBigUint64(12, file.uncompressedSize!, true)
-  header.setBigUint64(20, offset, true)
+  if (zip64HeaderLength & 16) {
+    header.setBigUint64(4, file.uncompressedSize!, true)
+    header.setBigUint64(12, file.uncompressedSize!, true)
+  }
+  header.setBigUint64(zip64HeaderLength - 8, offset, true)
   return makeUint8Array(header)
 }

test/crc32.test.ts

@@ -1,4 +1,4 @@
-import { assertEquals } from "https://deno.land/std/testing/asserts.ts"
+import { assertEquals } from "https://deno.land/std@0.132.0/testing/asserts.ts"
 import { crc32, memory } from "../src/crc32.ts"
 
 const table = await Deno.readFile("./test/table.array")

test/datetime.test.ts

@@ -1,4 +1,4 @@
-import { assertEquals } from "https://deno.land/std/testing/asserts.ts"
+import { assertEquals } from "https://deno.land/std@0.132.0/testing/asserts.ts"
 import { formatDOSDateTime } from "../src/datetime.ts"
 import { makeBuffer } from "../src/utils.ts"
 

test/zip.test.ts

@@ -1,4 +1,5 @@
-import { assertEquals, assertStrictEquals } from "https://deno.land/std/testing/asserts.ts"
+import { assertEquals, assertStrictEquals } from "https://deno.land/[email protected]/testing/asserts.ts"
+import { Buffer } from "https://deno.land/[email protected]/io/buffer.ts"
 import { fileHeader, fileData, dataDescriptor, centralHeader, zip64ExtraField } from "../src/zip.ts"
 import type { ZipFileDescription } from "../src/input.ts"
 
@@ -19,7 +20,7 @@ Deno.test("the ZIP fileHeader function makes file headers", () => {
 
 Deno.test("the ZIP fileData function yields all the file's data", async () => {
   const file = {...baseFile}
-  const actual = new Deno.Buffer()
+  const actual = new Buffer()
   for await (const chunk of fileData(file)) actual.writeSync(chunk)
   assertEquals(actual.bytes({copy: false}), zipSpec)
 })
@@ -50,23 +51,23 @@ Deno.test("the ZIP dataDescriptor function makes ZIP64 data descriptors", () =>
 Deno.test("the ZIP centralHeader function makes central record file headers", () => {
   const file = {...baseFile, uncompressedSize: 0x10203040n, crc: 0x12345678}
   const offset = 0x01020304n
-  const actual = centralHeader(file, offset, false)
+  const actual = centralHeader(file, offset, 0)
   const expected = BufferFromHex("504b01022d032d000800000000109a4e7856341240302010403020100b0000000000000000000000b48104030201")
   assertEquals(actual, expected)
 })
 
 Deno.test("the ZIP centralHeader function makes ZIP64 central record file headers", () => {
   const file = {...baseFile, uncompressedSize: 0x110203040n, crc: 0x12345678}
   const offset = 0x101020304n
-  const actual = centralHeader(file, offset, true)
+  const actual = centralHeader(file, offset, 28)
   const expected = BufferFromHex("504b01022d032d000800000000109a4e78563412ffffffffffffffff0b001c000000000000000000b481ffffffff")
   assertEquals(actual, expected)
 })
 
 Deno.test("the ZIP zip64ExtraField function makes Zip64 extra fields", () => {
   const file = {...baseFile, uncompressedSize: 0x10203040n, crc: 0x12345678}
   const offset = 0x01020304n
-  const actual = zip64ExtraField(file, offset)
+  const actual = zip64ExtraField(file, offset, 28)
   const expected = BufferFromHex("01001800403020100000000040302010000000000403020100000000")
   assertEquals(actual, expected)
 })