Mini Shell

'use strict'

// this[BUFFER] is the remainder of a chunk if we're waiting for
// the full 512 bytes of a header to come in.  We will Buffer.concat()
// it to the next write(), which is a mem copy, but a small one.
//
// this[QUEUE] is a Yallist of entries that haven't been emitted
// yet this can only get filled up if the user keeps write()ing after
// a write() returns false, or does a write() with more than one entry
//
// We don't buffer chunks, we always parse them and either create an
// entry, or push it into the active entry.  The ReadEntry class knows
// to throw data away if .ignore=true
//
// Shift entry off the buffer when it emits 'end', and emit 'entry' for
// the next one in the list.
//
// At any time, we're pushing body chunks into the entry at WRITEENTRY,
// and waiting for 'end' on the entry at READENTRY
//
// ignored entries get .resume() called on them straight away

const warner = require('./warn-mixin.js')
const Header = require('./header.js')
const EE = require('events')
const Yallist = require('yallist')
const maxMetaEntrySize = 1024 * 1024
const Entry = require('./read-entry.js')
const Pax = require('./pax.js')
const zlib = require('minizlib')
const { nextTick } = require('process')

const gzipHeader = Buffer.from([0x1f, 0x8b])
const STATE = Symbol('state')
const WRITEENTRY = Symbol('writeEntry')
const READENTRY = Symbol('readEntry')
const NEXTENTRY = Symbol('nextEntry')
const PROCESSENTRY = Symbol('processEntry')
const EX = Symbol('extendedHeader')
const GEX = Symbol('globalExtendedHeader')
const META = Symbol('meta')
const EMITMETA = Symbol('emitMeta')
const BUFFER = Symbol('buffer')
const QUEUE = Symbol('queue')
const ENDED = Symbol('ended')
const EMITTEDEND = Symbol('emittedEnd')
const EMIT = Symbol('emit')
const UNZIP = Symbol('unzip')
const CONSUMECHUNK = Symbol('consumeChunk')
const CONSUMECHUNKSUB = Symbol('consumeChunkSub')
const CONSUMEBODY = Symbol('consumeBody')
const CONSUMEMETA = Symbol('consumeMeta')
const CONSUMEHEADER = Symbol('consumeHeader')
const CONSUMING = Symbol('consuming')
const BUFFERCONCAT = Symbol('bufferConcat')
const MAYBEEND = Symbol('maybeEnd')
const WRITING = Symbol('writing')
const ABORTED = Symbol('aborted')
const DONE = Symbol('onDone')
const SAW_VALID_ENTRY = Symbol('sawValidEntry')
const SAW_NULL_BLOCK = Symbol('sawNullBlock')
const SAW_EOF = Symbol('sawEOF')
const CLOSESTREAM = Symbol('closeStream')

const noop = _ => true

module.exports = warner(class Parser extends EE {
  constructor (opt) {
    opt = opt || {}
    super(opt)

    this.file = opt.file || ''

    // set to boolean false when an entry starts.  1024 bytes of \0
    // is technically a valid tarball, albeit a boring one.
    this[SAW_VALID_ENTRY] = null

    // these BADARCHIVE errors can't be detected early. listen on DONE.
    this.on(DONE, _ => {
      if (this[STATE] === 'begin' || this[SAW_VALID_ENTRY] === false) {
        // either less than 1 block of data, or all entries were invalid.
        // Either way, probably not even a tarball.
        this.warn('TAR_BAD_ARCHIVE', 'Unrecognized archive format')
      }
    })

    if (opt.ondone) {
      this.on(DONE, opt.ondone)
    } else {
      this.on(DONE, _ => {
        this.emit('prefinish')
        this.emit('finish')
        this.emit('end')
      })
    }

    this.strict = !!opt.strict
    this.maxMetaEntrySize = opt.maxMetaEntrySize || maxMetaEntrySize
    this.filter = typeof opt.filter === 'function' ? opt.filter : noop
    // Unlike gzip, brotli doesn't have any magic bytes to identify it
    // Users need to explicitly tell us they're extracting a brotli file
    // Or we infer from the file extension
    const isTBR = (opt.file && (
        opt.file.endsWith('.tar.br') || opt.file.endsWith('.tbr')))
    // if it's a tbr file it MIGHT be brotli, but we don't know until
    // we look at it and verify it's not a valid tar file.
    this.brotli = !opt.gzip && opt.brotli !== undefined ? opt.brotli
      : isTBR ? undefined
      : false

    // have to set this so that streams are ok piping into it
    this.writable = true
    this.readable = false

    this[QUEUE] = new Yallist()
    this[BUFFER] = null
    this[READENTRY] = null
    this[WRITEENTRY] = null
    this[STATE] = 'begin'
    this[META] = ''
    this[EX] = null
    this[GEX] = null
    this[ENDED] = false
    this[UNZIP] = null
    this[ABORTED] = false
    this[SAW_NULL_BLOCK] = false
    this[SAW_EOF] = false

    this.on('end', () => this[CLOSESTREAM]())

    if (typeof opt.onwarn === 'function') {
      this.on('warn', opt.onwarn)
    }
    if (typeof opt.onentry === 'function') {
      this.on('entry', opt.onentry)
    }
  }

  [CONSUMEHEADER] (chunk, position) {
    if (this[SAW_VALID_ENTRY] === null) {
      this[SAW_VALID_ENTRY] = false
    }
    let header
    try {
      header = new Header(chunk, position, this[EX], this[GEX])
    } catch (er) {
      return this.warn('TAR_ENTRY_INVALID', er)
    }

    if (header.nullBlock) {
      if (this[SAW_NULL_BLOCK]) {
        this[SAW_EOF] = true
        // ending an archive with no entries.  pointless, but legal.
        if (this[STATE] === 'begin') {
          this[STATE] = 'header'
        }
        this[EMIT]('eof')
      } else {
        this[SAW_NULL_BLOCK] = true
        this[EMIT]('nullBlock')
      }
    } else {
      this[SAW_NULL_BLOCK] = false
      if (!header.cksumValid) {
        this.warn('TAR_ENTRY_INVALID', 'checksum failure', { header })
      } else if (!header.path) {
        this.warn('TAR_ENTRY_INVALID', 'path is required', { header })
      } else {
        const type = header.type
        if (/^(Symbolic)?Link$/.test(type) && !header.linkpath) {
          this.warn('TAR_ENTRY_INVALID', 'linkpath required', { header })
        } else if (!/^(Symbolic)?Link$/.test(type) && header.linkpath) {
          this.warn('TAR_ENTRY_INVALID', 'linkpath forbidden', { header })
        } else {
          const entry = this[WRITEENTRY] = new Entry(header, this[EX], this[GEX])

          // we do this for meta & ignored entries as well, because they
          // are still valid tar, or else we wouldn't know to ignore them
          if (!this[SAW_VALID_ENTRY]) {
            if (entry.remain) {
              // this might be the one!
              const onend = () => {
                if (!entry.invalid) {
                  this[SAW_VALID_ENTRY] = true
                }
              }
              entry.on('end', onend)
            } else {
              this[SAW_VALID_ENTRY] = true
            }
          }

          if (entry.meta) {
            if (entry.size > this.maxMetaEntrySize) {
              entry.ignore = true
              this[EMIT]('ignoredEntry', entry)
              this[STATE] = 'ignore'
              entry.resume()
            } else if (entry.size > 0) {
              this[META] = ''
              entry.on('data', c => this[META] += c)
              this[STATE] = 'meta'
            }
          } else {
            this[EX] = null
            entry.ignore = entry.ignore || !this.filter(entry.path, entry)

            if (entry.ignore) {
              // probably valid, just not something we care about
              this[EMIT]('ignoredEntry', entry)
              this[STATE] = entry.remain ? 'ignore' : 'header'
              entry.resume()
            } else {
              if (entry.remain) {
                this[STATE] = 'body'
              } else {
                this[STATE] = 'header'
                entry.end()
              }

              if (!this[READENTRY]) {
                this[QUEUE].push(entry)
                this[NEXTENTRY]()
              } else {
                this[QUEUE].push(entry)
              }
            }
          }
        }
      }
    }
  }

  [CLOSESTREAM] () {
    nextTick(() => this.emit('close'))
  }

  [PROCESSENTRY] (entry) {
    let go = true

    if (!entry) {
      this[READENTRY] = null
      go = false
    } else if (Array.isArray(entry)) {
      this.emit.apply(this, entry)
    } else {
      this[READENTRY] = entry
      this.emit('entry', entry)
      if (!entry.emittedEnd) {
        entry.on('end', _ => this[NEXTENTRY]())
        go = false
      }
    }

    return go
  }

  [NEXTENTRY] () {
    do {} while (this[PROCESSENTRY](this[QUEUE].shift()))

    if (!this[QUEUE].length) {
      // At this point, there's nothing in the queue, but we may have an
      // entry which is being consumed (readEntry).
      // If we don't, then we definitely can handle more data.
      // If we do, and either it's flowing, or it has never had any data
      // written to it, then it needs more.
      // The only other possibility is that it has returned false from a
      // write() call, so we wait for the next drain to continue.
      const re = this[READENTRY]
      const drainNow = !re || re.flowing || re.size === re.remain
      if (drainNow) {
        if (!this[WRITING]) {
          this.emit('drain')
        }
      } else {
        re.once('drain', _ => this.emit('drain'))
      }
    }
  }

  [CONSUMEBODY] (chunk, position) {
    // write up to but no  more than writeEntry.blockRemain
    const entry = this[WRITEENTRY]
    const br = entry.blockRemain
    const c = (br >= chunk.length && position === 0) ? chunk
      : chunk.slice(position, position + br)

    entry.write(c)

    if (!entry.blockRemain) {
      this[STATE] = 'header'
      this[WRITEENTRY] = null
      entry.end()
    }

    return c.length
  }

  [CONSUMEMETA] (chunk, position) {
    const entry = this[WRITEENTRY]
    const ret = this[CONSUMEBODY](chunk, position)

    // if we finished, then the entry is reset
    if (!this[WRITEENTRY]) {
      this[EMITMETA](entry)
    }

    return ret
  }

  [EMIT] (ev, data, extra) {
    if (!this[QUEUE].length && !this[READENTRY]) {
      this.emit(ev, data, extra)
    } else {
      this[QUEUE].push([ev, data, extra])
    }
  }

  [EMITMETA] (entry) {
    this[EMIT]('meta', this[META])
    switch (entry.type) {
      case 'ExtendedHeader':
      case 'OldExtendedHeader':
        this[EX] = Pax.parse(this[META], this[EX], false)
        break

      case 'GlobalExtendedHeader':
        this[GEX] = Pax.parse(this[META], this[GEX], true)
        break

      case 'NextFileHasLongPath':
      case 'OldGnuLongPath':
        this[EX] = this[EX] || Object.create(null)
        this[EX].path = this[META].replace(/\0.*/, '')
        break

      case 'NextFileHasLongLinkpath':
        this[EX] = this[EX] || Object.create(null)
        this[EX].linkpath = this[META].replace(/\0.*/, '')
        break

      /* istanbul ignore next */
      default: throw new Error('unknown meta: ' + entry.type)
    }
  }

  abort (error) {
    this[ABORTED] = true
    this.emit('abort', error)
    // always throws, even in non-strict mode
    this.warn('TAR_ABORT', error, { recoverable: false })
  }

  write (chunk) {
    if (this[ABORTED]) {
      return
    }

    // first write, might be gzipped
    const needSniff = this[UNZIP] === null ||
      this.brotli === undefined && this[UNZIP] === false
    if (needSniff && chunk) {
      if (this[BUFFER]) {
        chunk = Buffer.concat([this[BUFFER], chunk])
        this[BUFFER] = null
      }
      if (chunk.length < gzipHeader.length) {
        this[BUFFER] = chunk
        return true
      }

      // look for gzip header
      for (let i = 0; this[UNZIP] === null && i < gzipHeader.length; i++) {
        if (chunk[i] !== gzipHeader[i]) {
          this[UNZIP] = false
        }
      }

      const maybeBrotli = this.brotli === undefined
      if (this[UNZIP] === false && maybeBrotli) {
        // read the first header to see if it's a valid tar file. If so,
        // we can safely assume that it's not actually brotli, despite the
        // .tbr or .tar.br file extension.
        // if we ended before getting a full chunk, yes, def brotli
        if (chunk.length < 512) {
          if (this[ENDED]) {
            this.brotli = true
          } else {
            this[BUFFER] = chunk
            return true
          }
        } else {
          // if it's tar, it's pretty reliably not brotli, chances of
          // that happening are astronomical.
          try {
            new Header(chunk.slice(0, 512))
            this.brotli = false
          } catch (_) {
            this.brotli = true
          }
        }
      }

      if (this[UNZIP] === null || (this[UNZIP] === false && this.brotli)) {
        const ended = this[ENDED]
        this[ENDED] = false
        this[UNZIP] = this[UNZIP] === null
          ? new zlib.Unzip()
          : new zlib.BrotliDecompress()
        this[UNZIP].on('data', chunk => this[CONSUMECHUNK](chunk))
        this[UNZIP].on('error', er => this.abort(er))
        this[UNZIP].on('end', _ => {
          this[ENDED] = true
          this[CONSUMECHUNK]()
        })
        this[WRITING] = true
        const ret = this[UNZIP][ended ? 'end' : 'write'](chunk)
        this[WRITING] = false
        return ret
      }
    }

    this[WRITING] = true
    if (this[UNZIP]) {
      this[UNZIP].write(chunk)
    } else {
      this[CONSUMECHUNK](chunk)
    }
    this[WRITING] = false

    // return false if there's a queue, or if the current entry isn't flowing
    const ret =
      this[QUEUE].length ? false :
      this[READENTRY] ? this[READENTRY].flowing :
      true

    // if we have no queue, then that means a clogged READENTRY
    if (!ret && !this[QUEUE].length) {
      this[READENTRY].once('drain', _ => this.emit('drain'))
    }

    return ret
  }

  [BUFFERCONCAT] (c) {
    if (c && !this[ABORTED]) {
      this[BUFFER] = this[BUFFER] ? Buffer.concat([this[BUFFER], c]) : c
    }
  }

  [MAYBEEND] () {
    if (this[ENDED] &&
        !this[EMITTEDEND] &&
        !this[ABORTED] &&
        !this[CONSUMING]) {
      this[EMITTEDEND] = true
      const entry = this[WRITEENTRY]
      if (entry && entry.blockRemain) {
        // truncated, likely a damaged file
        const have = this[BUFFER] ? this[BUFFER].length : 0
        this.warn('TAR_BAD_ARCHIVE', `Truncated input (needed ${
          entry.blockRemain} more bytes, only ${have} available)`, { entry })
        if (this[BUFFER]) {
          entry.write(this[BUFFER])
        }
        entry.end()
      }
      this[EMIT](DONE)
    }
  }

  [CONSUMECHUNK] (chunk) {
    if (this[CONSUMING]) {
      this[BUFFERCONCAT](chunk)
    } else if (!chunk && !this[BUFFER]) {
      this[MAYBEEND]()
    } else {
      this[CONSUMING] = true
      if (this[BUFFER]) {
        this[BUFFERCONCAT](chunk)
        const c = this[BUFFER]
        this[BUFFER] = null
        this[CONSUMECHUNKSUB](c)
      } else {
        this[CONSUMECHUNKSUB](chunk)
      }

      while (this[BUFFER] &&
          this[BUFFER].length >= 512 &&
          !this[ABORTED] &&
          !this[SAW_EOF]) {
        const c = this[BUFFER]
        this[BUFFER] = null
        this[CONSUMECHUNKSUB](c)
      }
      this[CONSUMING] = false
    }

    if (!this[BUFFER] || this[ENDED]) {
      this[MAYBEEND]()
    }
  }

  [CONSUMECHUNKSUB] (chunk) {
    // we know that we are in CONSUMING mode, so anything written goes into
    // the buffer.  Advance the position and put any remainder in the buffer.
    let position = 0
    const length = chunk.length
    while (position + 512 <= length && !this[ABORTED] && !this[SAW_EOF]) {
      switch (this[STATE]) {
        case 'begin':
        case 'header':
          this[CONSUMEHEADER](chunk, position)
          position += 512
          break

        case 'ignore':
        case 'body':
          position += this[CONSUMEBODY](chunk, position)
          break

        case 'meta':
          position += this[CONSUMEMETA](chunk, position)
          break

        /* istanbul ignore next */
        default:
          throw new Error('invalid state: ' + this[STATE])
      }
    }

    if (position < length) {
      if (this[BUFFER]) {
        this[BUFFER] = Buffer.concat([chunk.slice(position), this[BUFFER]])
      } else {
        this[BUFFER] = chunk.slice(position)
      }
    }
  }

  end (chunk) {
    if (!this[ABORTED]) {
      if (this[UNZIP]) {
        this[UNZIP].end(chunk)
      } else {
        this[ENDED] = true
        if (this.brotli === undefined) chunk = chunk || Buffer.alloc(0)
        this.write(chunk)
      }
    }
  }
})