File permissions changed while unzipping.

[rash805115]

Yauzl library is incorrectly unzipping my file permissions. Below is a test file.

const AdmZip = require('adm-zip')
const fs = require('fs-extra')
const path = require('path')
const yauzl = require('yauzl')
const yazl = require('yazl')

// Create an archive of a file whose permission is 755.
let createArchive = function () {
  return new Promise(function (resolve) {
    let zip = new yazl.ZipFile()
    zip.addFile('./node_modules/webpack-dev-server/bin/webpack-dev-server.js', 'webpack-dev-server.js')
    zip.end(function () {
      zip.outputStream
        .pipe(fs.createWriteStream('./test.zip'))
        .on('close', function () {
          resolve()
        })
    })
  })
}

// Check the permission of the file inside zip. It should be same as what we archived.
let checkArchive = function () {
  return new Promise(function (resolve) {
    let outputZip = new AdmZip('./test.zip')
    resolve(outputZip.getEntry('webpack-dev-server.js'))
  })
}

// Extract the file and check its permission. It should be the same as the original permission.
let extractArchive = function () {
  return new Promise(function (resolve) {
    yauzl.open('./test.zip', {lazyEntries: true}, (error, zip) => {
      zip.on('end', () => { resolve() })
      zip.on('entry', (entry) => {
        zip.openReadStream(entry, function (error, readStream) {
          if (error) return zip.emit('error', error)

          // Save current entry. Then read next.
          fs.ensureFile(path.join('./', entry.fileName), (error) => {
            if (error) return zip.emit('error', error)

            let outputStream = fs.createWriteStream('./' + entry.fileName)
            outputStream.on('error', (error) => { zip.emit('error', error) })
            outputStream.on('finish', () => { zip.readEntry() })

            readStream.on('error', (error) => { zip.emit('error', error) })
            readStream.pipe(outputStream)
          })
        })
      })

      zip.readEntry()
    })
  })
}

let modes = {}

let originalMode = fs.statSync('./node_modules/webpack-dev-server/bin/webpack-dev-server.js')
modes['original'] = ((originalMode.mode << 16) >>> 0)

createArchive()
  .then(function () {
    return checkArchive()
  })
  .then(function (permission) {
    modes['zipped'] = permission.header.attr
    return extractArchive()
  })
  .then(function () {
    let unzippedMode = fs.statSync('./webpack-dev-server.js')
    modes['unzipped'] = ((unzippedMode.mode << 16) >>> 0)

    console.log('Original ' + modes['original']) // 33261 i.e. 755
    console.log('Zipped   ' + modes['zipped']) // 33261 i.e. 755
    console.log('Unzipped ' + modes['unzipped']) // 33188 i.e. 644
  })

Output

Original 2179792896
Zipped   2179792896
Unzipped 2175008768

I have also verified that in Line 287, the same value as zipped is read, so I am not sure why the file is not set with correct permissions.

[thejoshwolfe]

yauzl does not write to the file system. This line from your example is where the file is being created:

let outputStream = fs.createWriteStream('./' + entry.fileName)

or possibly this line; i'm not familiar with the libraries you're using:

fs.ensureFile(path.join('./', entry.fileName), ...)

You'll need to set the file permission bits yourself. See the readme for how to get the file permissions from yauzl.

[rash805115]

Ah I see. Thank you for explanation. I will have to change this line.

let outputStream = fs.createWriteStream('./' + entry.fileName, {mode: entry.externalFileAttributes})

But externalFileAttributes is this big number 2179792896 that I am not sure how to convert to 33261 and I couldn't find anything in docs.

[thejoshwolfe]

Ah sorry! I was thinking of the docs for yazl. My mistake.

If you trust that your zip files are all coming from a UNIX-like zipfile creator, then you can use this:

{mode: entry.externalFileAttributes >>> 16}

I have not done an analysis to see how common it is to encode the permission bits like this in the external file attributes, but I know it is typical in at least some situations. The meaning of the external file attributes is not specified by the zipfile specification.

It's probably appropriate for me to do this investigation and have a getter function in the Entry class like I do for getLastModDate(). An implementation would include the above logic in at least one case for that function.

[rash805115]

It works! I was missing two things.

1. It turns out that the method ensureFile() that I was using to ensure an empty file is present, creates the file with default 644 permission and this will never be overridden. So I am now using ensureDir() method to only ensure the directory structure exists, not file.
2. The fs.createWriteStream() method with mode option then ensures that my file is created with correct permissions. I used your suggested conversion {mode: entry.externalFileAttributes >>> 16} and it works just fine.

Regarding yauzl code change, if the method is about this much only, then I can raise a PR with this code and appropriate README changes.

let getLastModDate = function () {
  return entry.externalFileAttributes >>> 16
}

I will leave this PR to your discretion. You can keep it open to track the changes, or close it.

[thejoshwolfe]

I opened #102 to implement the method.