asar.js

'use strict';

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

  const envNoAsar = process.env.ELECTRON_NO_ASAR &&
      process.type !== 'browser' &&
      process.type !== 'renderer'
  const isAsarDisabled = () => process.noAsar || envNoAsar

  /**
   * @param {!Function} functionToCall
   * @param {!Array|undefined} args
   */
  const nextTick = (functionToCall, args = []) => {
    process.nextTick(() => functionToCall(...args))
  }

  // Cache asar archive objects.
  const cachedArchives = new Map()

  const getOrCreateArchive = archivePath => {
    const isCached = cachedArchives.has(archivePath)
    if (isCached) {
      return cachedArchives.get(archivePath)
    }

    const newArchive = asar.createArchive(archivePath)
    if (!newArchive) return null

    cachedArchives.set(archivePath, newArchive)
    return newArchive
  }

  const ASAR_EXTENSION = '.asar'

  // Separate asar package's path from full path.
  const splitPath = archivePathOrBuffer => {
    // Shortcut for disabled asar.
    if (isAsarDisabled()) return { isAsar: false }

    // Check for a bad argument type.
    let archivePath = archivePathOrBuffer
    if (Buffer.isBuffer(archivePathOrBuffer)) {
      archivePath = archivePathOrBuffer.toString()
    }
    if (typeof archivePath !== 'string') return { isAsar: false }

    if (archivePath.endsWith(ASAR_EXTENSION)) {
      return { isAsar: true, asarPath: archivePath, filePath: '' }
    }

    archivePath = path.normalize(archivePath)
    const index = archivePath.lastIndexOf(`${ASAR_EXTENSION}${path.sep}`)
    if (index === -1) return { isAsar: false }

    // E.g. for "//some/path/to/archive.asar/then/internal.file"...
    return {
      isAsar: true,
      // "//some/path/to/archive.asar"
      asarPath: archivePath.substr(0, index + ASAR_EXTENSION.length),
      // "then/internal.file" (with a path separator excluded)
      filePath: archivePath.substr(index + ASAR_EXTENSION.length + 1)
    }
  }

  // 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 msec = (date) => (date || fakeTime).getTime()

  const asarStatsToFsStats = function (stats) {
    const { Stats, constants } = require('fs')

    let mode = constants.S_IROTH ^ constants.S_IRGRP ^ constants.S_IRUSR ^ constants.S_IWUSR

    if (stats.isFile) {
      mode ^= constants.S_IFREG
    } else if (stats.isDirectory) {
      mode ^= constants.S_IFDIR
    } else if (stats.isLink) {
      mode ^= constants.S_IFLNK
    }

    return new Stats(
      1, // dev
      mode, // mode
      1, // nlink
      uid,
      gid,
      0, // rdev
      undefined, // blksize
      ++nextInode, // ino
      stats.size,
      undefined, // blocks,
      msec(stats.atime), // atim_msec
      msec(stats.mtime), // mtim_msec
      msec(stats.ctime), // ctim_msec
      msec(stats.birthtime) // birthtim_msec
    )
  }

  const AsarError = {
    NOT_FOUND: 'NOT_FOUND',
    NOT_DIR: 'NOT_DIR',
    NO_ACCESS: 'NO_ACCESS',
    INVALID_ARCHIVE: 'INVALID_ARCHIVE'
  }

  const createError = (errorType, { asarPath, filePath } = {}) => {
    let error
    switch (errorType) {
      case AsarError.NOT_FOUND:
        error = new Error(`ENOENT, ${filePath} not found in ${asarPath}`)
        error.code = 'ENOENT'
        error.errno = -2
        break
      case AsarError.NOT_DIR:
        error = new Error('ENOTDIR, not a directory')
        error.code = 'ENOTDIR'
        error.errno = -20
        break
      case AsarError.NO_ACCESS:
        error = new Error(`EACCES: permission denied, access '${filePath}'`)
        error.code = 'EACCES'
        error.errno = -13
        break
      case AsarError.INVALID_ARCHIVE:
        error = new Error(`Invalid package ${asarPath}`)
        break
      default:
        assert.fail(`Invalid error type "${errorType}" passed to createError.`)
    }
    return error
  }

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

      const archive = getOrCreateArchive(asarPath)
      if (!archive) throw createError(AsarError.INVALID_ARCHIVE, { asarPath })

      const newPath = archive.copyFileOut(filePath)
      if (!newPath) throw createError(AsarError.NOT_FOUND, { asarPath, filePath })

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

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

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

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const newPath = archive.copyFileOut(filePath)
      if (!newPath) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

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

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

        const archive = getOrCreateArchive(asarPath)
        if (!archive) {
          return Promise.reject(createError(AsarError.INVALID_ARCHIVE, { asarPath }))
        }

        const newPath = archive.copyFileOut(filePath)
        if (!newPath) {
          return Promise.reject(createError(AsarError.NOT_FOUND, { asarPath, filePath }))
        }

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

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

    const { lstatSync } = fs
    fs.lstatSync = (pathArgument, options) => {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return lstatSync(pathArgument, options)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) throw createError(AsarError.INVALID_ARCHIVE, { asarPath })

      const stats = archive.stat(filePath)
      if (!stats) throw createError(AsarError.NOT_FOUND, { asarPath, filePath })

      return asarStatsToFsStats(stats)
    }

    const { lstat } = fs
    fs.lstat = function (pathArgument, options, callback) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (typeof options === 'function') {
        callback = options
        options = {}
      }
      if (!isAsar) return lstat(pathArgument, options, callback)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const stats = archive.stat(filePath)
      if (!stats) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      const fsStats = asarStatsToFsStats(stats)
      nextTick(callback, [null, fsStats])
    }

    const { statSync } = fs
    fs.statSync = (pathArgument, options) => {
      const { isAsar } = splitPath(pathArgument)
      if (!isAsar) return statSync(pathArgument, options)

      // Do not distinguish links for now.
      return fs.lstatSync(pathArgument, options)
    }

    const { stat } = fs
    fs.stat = (pathArgument, options, callback) => {
      const { isAsar } = splitPath(pathArgument)
      if (typeof options === 'function') {
        callback = options
        options = {}
      }
      if (!isAsar) return stat(pathArgument, options, callback)

      // Do not distinguish links for now.
      process.nextTick(() => fs.lstat(pathArgument, options, callback))
    }

    const { realpathSync } = fs
    fs.realpathSync = function (pathArgument, options) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return realpathSync.apply(this, arguments)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        throw createError(AsarError.INVALID_ARCHIVE, { asarPath })
      }

      const fileRealPath = archive.realpath(filePath)
      if (fileRealPath === false) {
        throw createError(AsarError.NOT_FOUND, { asarPath, filePath })
      }

      return path.join(realpathSync(asarPath, options), fileRealPath)
    }

    fs.realpathSync.native = function (pathArgument, options) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return realpathSync.native.apply(this, arguments)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        throw createError(AsarError.INVALID_ARCHIVE, { asarPath })
      }

      const fileRealPath = archive.realpath(filePath)
      if (fileRealPath === false) {
        throw createError(AsarError.NOT_FOUND, { asarPath, filePath })
      }

      return path.join(realpathSync.native(asarPath, options), fileRealPath)
    }

    const { realpath } = fs
    fs.realpath = function (pathArgument, options, callback) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return realpath.apply(this, arguments)

      if (arguments.length < 3) {
        callback = options
        options = {}
      }

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const fileRealPath = archive.realpath(filePath)
      if (fileRealPath === false) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      realpath(asarPath, options, (error, archiveRealPath) => {
        if (error === null) {
          const fullPath = path.join(archiveRealPath, fileRealPath)
          callback(null, fullPath)
        } else {
          callback(error)
        }
      })
    }

    fs.realpath.native = function (pathArgument, options, callback) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return realpath.native.apply(this, arguments)

      if (arguments.length < 3) {
        callback = options
        options = {}
      }

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const fileRealPath = archive.realpath(filePath)
      if (fileRealPath === false) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      realpath.native(asarPath, options, (error, archiveRealPath) => {
        if (error === null) {
          const fullPath = path.join(archiveRealPath, fileRealPath)
          callback(null, fullPath)
        } else {
          callback(error)
        }
      })
    }

    const { exists } = fs
    fs.exists = (pathArgument, callback) => {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return exists(pathArgument, callback)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const pathExists = (archive.stat(filePath) !== false)
      nextTick(callback, [pathExists])
    }

    fs.exists[util.promisify.custom] = pathArgument => {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return exists[util.promisify.custom](pathArgument)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        return Promise.reject(error)
      }

      return Promise.resolve(archive.stat(filePath) !== false)
    }

    const { existsSync } = fs
    fs.existsSync = pathArgument => {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return existsSync(pathArgument)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) return false

      return archive.stat(filePath) !== false
    }

    const { access } = fs
    fs.access = function (pathArgument, mode, callback) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return access.apply(this, arguments)

      if (typeof mode === 'function') {
        callback = mode
        mode = fs.constants.F_OK
      }

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const info = archive.getFileInfo(filePath)
      if (!info) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.access(realPath, mode, callback)
      }

      const stats = archive.stat(filePath)
      if (!stats) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      if (mode & fs.constants.W_OK) {
        const error = createError(AsarError.NO_ACCESS, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      nextTick(callback)
    }

    const { accessSync } = fs
    fs.accessSync = function (pathArgument, mode) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return accessSync.apply(this, arguments)

      if (mode == null) mode = fs.constants.F_OK

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        throw createError(AsarError.INVALID_ARCHIVE, { asarPath })
      }

      const info = archive.getFileInfo(filePath)
      if (!info) {
        throw createError(AsarError.NOT_FOUND, { asarPath, filePath })
      }

      if (info.unpacked) {
        const realPath = archive.copyFileOut(filePath)
        return fs.accessSync(realPath, mode)
      }

      const stats = archive.stat(filePath)
      if (!stats) {
        throw createError(AsarError.NOT_FOUND, { asarPath, filePath })
      }

      if (mode & fs.constants.W_OK) {
        throw createError(AsarError.NO_ACCESS, { asarPath, filePath })
      }
    }

    const { readFile } = fs
    fs.readFile = function (pathArgument, options, callback) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      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) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const info = archive.getFileInfo(filePath)
      if (!info) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      if (info.size === 0) {
        nextTick(callback, [null, encoding ? '' : Buffer.alloc(0)])
        return
      }

      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)) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      logASARAccess(asarPath, filePath, info.offset)
      fs.read(fd, buffer, 0, info.size, info.offset, error => {
        callback(error, encoding ? buffer.toString(encoding) : buffer)
      })
    }

    const { readFileSync } = fs
    fs.readFileSync = function (pathArgument, options) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return readFileSync.apply(this, arguments)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) throw createError(AsarError.INVALID_ARCHIVE, { asarPath })

      const info = archive.getFileInfo(filePath)
      if (!info) throw createError(AsarError.NOT_FOUND, { asarPath, filePath })

      if (info.size === 0) return (options) ? '' : 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)) throw createError(AsarError.NOT_FOUND, { asarPath, filePath })

      logASARAccess(asarPath, filePath, info.offset)
      fs.readSync(fd, buffer, 0, info.size, info.offset)
      return (encoding) ? buffer.toString(encoding) : buffer
    }

    const { readdir } = fs
    fs.readdir = function (pathArgument, options, callback) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (typeof options === 'function') {
        callback = options
        options = {}
      }
      if (!isAsar) return readdir.apply(this, arguments)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        const error = createError(AsarError.INVALID_ARCHIVE, { asarPath })
        nextTick(callback, [error])
        return
      }

      const files = archive.readdir(filePath)
      if (!files) {
        const error = createError(AsarError.NOT_FOUND, { asarPath, filePath })
        nextTick(callback, [error])
        return
      }

      nextTick(callback, [null, files])
    }

    const { readdirSync } = fs
    fs.readdirSync = function (pathArgument, options) {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return readdirSync.apply(this, arguments)

      const archive = getOrCreateArchive(asarPath)
      if (!archive) {
        throw createError(AsarError.INVALID_ARCHIVE, { asarPath })
      }

      const files = archive.readdir(filePath)
      if (!files) {
        throw createError(AsarError.NOT_FOUND, { asarPath, filePath })
      }

      return files
    }

    const { internalModuleReadJSON } = process.binding('fs')
    process.binding('fs').internalModuleReadJSON = pathArgument => {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return internalModuleReadJSON(pathArgument)

      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 = pathArgument => {
      const { isAsar, asarPath, filePath } = splitPath(pathArgument)
      if (!isAsar) return internalModuleStat(pathArgument)

      // -ENOENT
      const archive = getOrCreateArchive(asarPath)
      if (!archive) return -34

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

      return (stats.isDirectory) ? 1 : 0
    }

    // Calling mkdir for directory inside asar archive should throw ENOTDIR
    // error, but on Windows it throws ENOENT.
    if (process.platform === 'win32') {
      const { mkdir } = fs
      fs.mkdir = (pathArgument, options, callback) => {
        if (typeof options === 'function') {
          callback = options
          options = {}
        }

        const { isAsar, filePath } = splitPath(pathArgument)
        if (isAsar && filePath.length > 0) {
          const error = createError(AsarError.NOT_DIR)
          nextTick(callback, [error])
          return
        }

        mkdir(pathArgument, options, callback)
      }

      const { mkdirSync } = fs
      fs.mkdirSync = function (pathArgument, options) {
        const { isAsar, filePath } = splitPath(pathArgument)
        if (isAsar && filePath.length) throw createError(AsarError.NOT_DIR)
        return mkdirSync(pathArgument, options)
      }
    }

    // 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
        }
      }
    }

    // Strictly implementing the flags of fs.copyFile is hard, just do a simple
    // implementation for now. Doing 2 copies won't spend much time more as OS
    // has filesystem caching.
    overrideAPI(fs, 'copyFile')
    overrideAPISync(fs, 'copyFileSync')

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