electron/lib/common/asar.js

(function () {
  const asar = process.binding('atom_common_asar')
  const {Buffer} = require('buffer')
  const childProcess = require('child_process')
  const path = require('path')
  const util = require('util')

  const hasProp = {}.hasOwnProperty

  // Cache asar archive objects.
  const cachedArchives = {}

  const envNoAsar = process.env.ELECTRON_NO_ASAR && process.type !== 'browser' && process.type !== 'renderer'
  const isAsarDisabled = function () {
    return process.noAsar || envNoAsar
  }

  const getOrCreateArchive = function (p) {
    let archive = cachedArchives[p]
    if (archive != null) {
      return archive
    }
    archive = asar.createArchive(p)
    if (!archive) {
      return false
    }
    cachedArchives[p] = archive
    return archive
  }

  // Clean cache on quit.
  process.on('exit', function () {
    for (let p in cachedArchives) {
      if (!hasProp.call(cachedArchives, p)) continue
      cachedArchives[p].destroy()
    }
  })

  // Separate asar package's path from full path.
  const splitPath = function (p) {
    // shortcut to disable asar.
    if (isAsarDisabled()) {
      return [false]
    }

    if (Buffer.isBuffer(p)) {
      p = p.toString()
    }

    if (typeof p !== 'string') {
      return [false]
    }

    if (p.substr(-5) === '.asar') {
      return [true, p, '']
    }

    p = path.normalize(p)
    const index = p.lastIndexOf('.asar' + path.sep)
    if (index === -1) {
      return [false]
    }
    return [true, p.substr(0, index + 5), p.substr(index + 6)]
  }

  // Convert asar archive's Stats object to fs's Stats object.
  let nextInode = 0

  const uid = process.getuid != null ? process.getuid() : 0

  const gid = process.getgid != null ? process.getgid() : 0

  const fakeTime = new Date()

  const asarStatsToFsStats = function (stats) {
    return {
      dev: 1,
      ino: ++nextInode,
      mode: 33188,
      nlink: 1,
      uid: uid,
      gid: gid,
      rdev: 0,
      atime: stats.atime || fakeTime,
      birthtime: stats.birthtime || fakeTime,
      mtime: stats.mtime || fakeTime,
      ctime: stats.ctime || fakeTime,
      size: stats.size,
      isFile: function () {
        return stats.isFile
      },
      isDirectory: function () {
        return stats.isDirectory
      },
      isSymbolicLink: function () {
        return stats.isLink
      },
      isBlockDevice: function () {
        return false
      },
      isCharacterDevice: function () {
        return false
      },
      isFIFO: function () {
        return false
      },
      isSocket: function () {
        return false
      }
    }
  }

  // Create a ENOENT error.
  const notFoundError = function (asarPath, filePath, callback) {
    const error = new Error(`ENOENT, ${filePath} not found in ${asarPath}`)
    error.code = 'ENOENT'
    error.errno = -2
    if (typeof callback !== 'function') {
      throw error
    }
    process.nextTick(function () {
      callback(error)
    })
  }

  // Create a ENOTDIR error.
  const notDirError = function (callback) {
    const error = new Error('ENOTDIR, not a directory')
    error.code = 'ENOTDIR'
    error.errno = -20
    if (typeof callback !== 'function') {
      throw error
    }
    process.nextTick(function () {
      callback(error)
    })
  }

  // Create a EACCES error.
  const accessError = function (asarPath, filePath, callback) {
    const error = new Error(`EACCES: permission denied, access '${filePath}'`)
    error.code = 'EACCES'
    error.errno = -13
    if (typeof callback !== 'function') {
      throw error
    }
    process.nextTick(function () {
      callback(error)
    })
  }

  // Create invalid archive error.
  const invalidArchiveError = function (asarPath, callback) {
    const error = new Error(`Invalid package ${asarPath}`)
    if (typeof callback !== 'function') {
      throw error
    }
    process.nextTick(function () {
      callback(error)
    })
  }

  // Override APIs that rely on passing file path instead of content to C++.
  const overrideAPISync = function (module, name, arg) {
    if (arg == null) {
      arg = 0
    }
    const old = module[name]
    module[name] = function () {
      const p = arguments[arg]
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return old.apply(this, arguments)
      }

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        invalidArchiveError(asarPath)
      }

      const newPath = archive.copyFileOut(filePath)
      if (!newPath) {
        notFoundError(asarPath, filePath)
      }

      arguments[arg] = newPath
      return old.apply(this, arguments)
    }
  }

  const overrideAPI = function (module, name, arg) {
    if (arg == null) {
      arg = 0
    }
    const old = module[name]
    module[name] = function () {
      const p = arguments[arg]
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return old.apply(this, arguments)
      }

      const callback = arguments[arguments.length - 1]
      if (typeof callback !== 'function') {
        return overrideAPISync(module, name, arg)
      }

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }

      const newPath = archive.copyFileOut(filePath)
      if (!newPath) {
        return notFoundError(asarPath, filePath, callback)
      }

      arguments[arg] = newPath
      return old.apply(this, arguments)
    }
    if (old[util.promisify.custom]) {
      module[name][util.promisify.custom] = function () {
        const p = arguments[arg]
        const [isAsar, asarPath, filePath] = splitPath(p)
        if (!isAsar) {
          return old[util.promisify.custom].apply(this, arguments)
        }

        const archive = getOrCreateArchive(asarPath)
        if (!archive) {
          return new Promise(() => invalidArchiveError(asarPath))
        }

        const newPath = archive.copyFileOut(filePath)
        if (!newPath) {
          return new Promise(() => notFoundError(asarPath, filePath))
        }

        arguments[arg] = newPath
        return old[util.promisify.custom].apply(this, arguments)
      }
    }
  }

  // Override fs APIs.
  exports.wrapFsWithAsar = function (fs) {
    const logFDs = {}
    const logASARAccess = function (asarPath, filePath, offset) {
      if (!process.env.ELECTRON_LOG_ASAR_READS) {
        return
      }
      if (!logFDs[asarPath]) {
        const path = require('path')
        const logFilename = path.basename(asarPath, '.asar') + '-access-log.txt'
        const logPath = path.join(require('os').tmpdir(), logFilename)
        logFDs[asarPath] = fs.openSync(logPath, 'a')
        console.log('Logging ' + asarPath + ' access to ' + logPath)
      }
      fs.writeSync(logFDs[asarPath], offset + ': ' + filePath + '\n')
    }

    const {lstatSync} = fs
    fs.lstatSync = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return lstatSync(p)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        invalidArchiveError(asarPath)
      }
      const stats = archive.stat(filePath)
      if (!stats) {
        notFoundError(asarPath, filePath)
      }
      return asarStatsToFsStats(stats)
    }

    const {lstat} = fs
    fs.lstat = function (p, callback) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return lstat(p, callback)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }
      const stats = getOrCreateArchive(asarPath).stat(filePath)
      if (!stats) {
        return notFoundError(asarPath, filePath, callback)
      }
      process.nextTick(function () {
        callback(null, asarStatsToFsStats(stats))
      })
    }

    const {statSync} = fs
    fs.statSync = function (p) {
      const [isAsar] = splitPath(p)
      if (!isAsar) {
        return statSync(p)
      }

      // Do not distinguish links for now.
      return fs.lstatSync(p)
    }

    const {stat} = fs
    fs.stat = function (p, callback) {
      const [isAsar] = splitPath(p)
      if (!isAsar) {
        return stat(p, callback)
      }

      // Do not distinguish links for now.
      process.nextTick(function () {
        fs.lstat(p, callback)
      })
    }

    const {statSyncNoException} = fs
    fs.statSyncNoException = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return statSyncNoException(p)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return false
      }
      const stats = archive.stat(filePath)
      if (!stats) {
        return false
      }
      return asarStatsToFsStats(stats)
    }

    const {realpathSync} = fs
    fs.realpathSync = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return realpathSync.apply(this, arguments)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        invalidArchiveError(asarPath)
      }
      const real = archive.realpath(filePath)
      if (real === false) {
        notFoundError(asarPath, filePath)
      }
      return path.join(realpathSync(asarPath), real)
    }

    const {realpath} = fs
    fs.realpath = function (p, cache, callback) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return realpath.apply(this, arguments)
      }
      if (typeof cache === 'function') {
        callback = cache
        cache = void 0
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }
      const real = archive.realpath(filePath)
      if (real === false) {
        return notFoundError(asarPath, filePath, callback)
      }
      return realpath(asarPath, function (err, p) {
        if (err) {
          return callback(err)
        }
        return callback(null, path.join(p, real))
      })
    }

    const {exists} = fs
    fs.exists = function (p, callback) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return exists(p, callback)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }
      process.nextTick(function () {
        // Disabled due to false positive in StandardJS
        // eslint-disable-next-line standard/no-callback-literal
        callback(archive.stat(filePath) !== false)
      })
    }

    fs.exists[util.promisify.custom] = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return exists[util.promisify.custom](p)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return new Promise(() => invalidArchiveError(asarPath))
      }
      return Promise.resolve(archive.stat(filePath) !== false)
    }

    const {existsSync} = fs
    fs.existsSync = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return existsSync(p)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return false
      }
      return archive.stat(filePath) !== false
    }

    const {access} = fs
    fs.access = function (p, mode, callback) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return access.apply(this, arguments)
      }
      if (typeof mode === 'function') {
        callback = mode
        mode = fs.constants.F_OK
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }
      const info = archive.getFileInfo(filePath)
      if (!info) {
        return notFoundError(asarPath, filePath, callback)
      }
      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.access(realPath, mode, callback)
      }
      const stats = getOrCreateArchive(asarPath).stat(filePath)
      if (!stats) {
        return notFoundError(asarPath, filePath, callback)
      }
      if (mode & fs.constants.W_OK) {
        return accessError(asarPath, filePath, callback)
      }
      process.nextTick(function () {
        callback()
      })
    }

    const {accessSync} = fs
    fs.accessSync = function (p, mode) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return accessSync.apply(this, arguments)
      }
      if (mode == null) {
        mode = fs.constants.F_OK
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        invalidArchiveError(asarPath)
      }
      const info = archive.getFileInfo(filePath)
      if (!info) {
        notFoundError(asarPath, filePath)
      }
      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.accessSync(realPath, mode)
      }
      const stats = getOrCreateArchive(asarPath).stat(filePath)
      if (!stats) {
        notFoundError(asarPath, filePath)
      }
      if (mode & fs.constants.W_OK) {
        accessError(asarPath, filePath)
      }
    }

    const {readFile} = fs
    fs.readFile = function (p, options, callback) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return readFile.apply(this, arguments)
      }
      if (typeof options === 'function') {
        callback = options
        options = {
          encoding: null
        }
      } else if (typeof options === 'string') {
        options = {
          encoding: options
        }
      } else if (options === null || options === undefined) {
        options = {
          encoding: null
        }
      } else if (typeof options !== 'object') {
        throw new TypeError('Bad arguments')
      }
      const {encoding} = options

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }
      const info = archive.getFileInfo(filePath)
      if (!info) {
        return notFoundError(asarPath, filePath, callback)
      }
      if (info.size === 0) {
        return process.nextTick(function () {
          callback(null, encoding ? '' : Buffer.alloc(0))
        })
      }
      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.readFile(realPath, options, callback)
      }

      const buffer = Buffer.alloc(info.size)
      const fd = archive.getFd()
      if (!(fd >= 0)) {
        return notFoundError(asarPath, filePath, callback)
      }
      logASARAccess(asarPath, filePath, info.offset)
      fs.read(fd, buffer, 0, info.size, info.offset, function (error) {
        callback(error, encoding ? buffer.toString(encoding) : buffer)
      })
    }

    const {readFileSync} = fs
    fs.readFileSync = function (p, options) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return readFileSync.apply(this, arguments)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        invalidArchiveError(asarPath)
      }
      const info = archive.getFileInfo(filePath)
      if (!info) {
        notFoundError(asarPath, filePath)
      }
      if (info.size === 0) {
        if (options) {
          return ''
        } else {
          return Buffer.alloc(0)
        }
      }
      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.readFileSync(realPath, options)
      }
      if (!options) {
        options = {
          encoding: null
        }
      } else if (typeof options === 'string') {
        options = {
          encoding: options
        }
      } else if (typeof options !== 'object') {
        throw new TypeError('Bad arguments')
      }
      const {encoding} = options
      const buffer = Buffer.alloc(info.size)
      const fd = archive.getFd()
      if (!(fd >= 0)) {
        notFoundError(asarPath, filePath)
      }
      logASARAccess(asarPath, filePath, info.offset)
      fs.readSync(fd, buffer, 0, info.size, info.offset)
      if (encoding) {
        return buffer.toString(encoding)
      } else {
        return buffer
      }
    }

    const {readdir} = fs
    fs.readdir = function (p, callback) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return readdir.apply(this, arguments)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return invalidArchiveError(asarPath, callback)
      }
      const files = archive.readdir(filePath)
      if (!files) {
        return notFoundError(asarPath, filePath, callback)
      }
      process.nextTick(function () {
        callback(null, files)
      })
    }

    const {readdirSync} = fs
    fs.readdirSync = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return readdirSync.apply(this, arguments)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        invalidArchiveError(asarPath)
      }
      const files = archive.readdir(filePath)
      if (!files) {
        notFoundError(asarPath, filePath)
      }
      return files
    }

    const {internalModuleReadFile} = process.binding('fs')
    process.binding('fs').internalModuleReadFile = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return internalModuleReadFile(p)
      }
      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        return
      }
      const info = archive.getFileInfo(filePath)
      if (!info) {
        return
      }
      if (info.size === 0) {
        return ''
      }
      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.readFileSync(realPath, {
          encoding: 'utf8'
        })
      }
      const buffer = Buffer.alloc(info.size)
      const fd = archive.getFd()
      if (!(fd >= 0)) {
        return
      }
      logASARAccess(asarPath, filePath, info.offset)
      fs.readSync(fd, buffer, 0, info.size, info.offset)
      return buffer.toString('utf8')
    }

    const {internalModuleStat} = process.binding('fs')
    process.binding('fs').internalModuleStat = function (p) {
      const [isAsar, asarPath, filePath] = splitPath(p)
      if (!isAsar) {
        return internalModuleStat(p)
      }
      const archive = getOrCreateArchive(asarPath)

      // -ENOENT
      if (!archive) {
        return -34
      }
      const stats = archive.stat(filePath)

      // -ENOENT
      if (!stats) {
        return -34
      }
      if (stats.isDirectory) {
        return 1
      } else {
        return 0
      }
    }

    // Calling mkdir for directory inside asar archive should throw ENOTDIR
    // error, but on Windows it throws ENOENT.
    // This is to work around the recursive looping bug of mkdirp since it is
    // widely used.
    if (process.platform === 'win32') {
      const {mkdir} = fs
      fs.mkdir = function (p, mode, callback) {
        if (typeof mode === 'function') {
          callback = mode
        }
        const [isAsar, , filePath] = splitPath(p)
        if (isAsar && filePath.length) {
          return notDirError(callback)
        }
        mkdir(p, mode, callback)
      }

      const {mkdirSync} = fs
      fs.mkdirSync = function (p, mode) {
        const [isAsar, , filePath] = splitPath(p)
        if (isAsar && filePath.length) {
          notDirError()
        }
        return mkdirSync(p, mode)
      }
    }

    // Executing a command string containing a path to an asar
    // archive confuses `childProcess.execFile`, which is internally
    // called by `childProcess.{exec,execSync}`, causing
    // Electron to consider the full command as a single path
    // to an archive.
    const {exec, execSync} = childProcess
    childProcess.exec = invokeWithNoAsar(exec)
    childProcess.exec[util.promisify.custom] = invokeWithNoAsar(exec[util.promisify.custom])
    childProcess.execSync = invokeWithNoAsar(execSync)

    function invokeWithNoAsar (func) {
      return function () {
        const processNoAsarOriginalValue = process.noAsar
        process.noAsar = true
        try {
          return func.apply(this, arguments)
        } finally {
          process.noAsar = processNoAsarOriginalValue
        }
      }
    }

    overrideAPI(fs, 'open')
    overrideAPI(childProcess, 'execFile')
    overrideAPISync(process, 'dlopen', 1)
    overrideAPISync(require('module')._extensions, '.node', 1)
    overrideAPISync(fs, 'openSync')
    overrideAPISync(childProcess, 'execFileSync')
  }
})()