dezip-1.1.zip / dezip / main.go  
 
 ..
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
package main

import (
    "archive/tar"
    "archive/zip"
    "compress/bzip2"
    "compress/gzip"
    "fmt"
    "io"
    "io/ioutil"
    "log"
    "net/http"
    "net/url"
    "os"
    "os/signal"
    "path"
    "regexp"
    "runtime/debug"
    "sort"
    "strings"
    "strconv"
    "sync"
    "syscall"
    "time"

    "github.com/jlaffaye/ftp"
    "github.com/makeworld-the-better-one/go-gemini"
    "github.com/prologic/go-gopher"

    "github.com/xi2/xz"
)

// the archive that this source code can be found within.  the root of the site
// redirects to README.md within this archive.
const thisArchive = "https://dezip.org/dezip-1.1.zip"

// how long can the URL's path be before it's rejected?
const URLPathLimit = 999

// the maximum number of components allowed in a URL.
const URLComponentLimit = 99

// analogous limits for the path within the archive.  255 is important here
// because it keeps the lengths small enough to fit into one byte in the search
// index.
const archivePathLimit = 255
const archiveComponentLimit = 99

// files above this limit aren't rendered.
const textFileSizeLimit = 50_000_000 // 50 MB

// archives with a directory having more than this number of entries will fail
// to render.
const entriesPerDirectoryLimit = 99999

// downloads over this limit will fail.
const archiveSizeLimit = 1_000_000_000 // 1 GB

// unpacking an archive larger than this limit will fail.
const uncompressedArchiveSizeLimit = 3_000_000_000 // 3 GB

// files with lines longer than this won't get syntax highlighting.
const lineLengthLimit = 1000

// the maximum number of "weird" characters above 0xF4 that can appear before a
// file is considered a binary file.
const weirdCharacterLimit = 3

// the number of renderer goroutines running at once.
const numberOfRenderers = 2

// the number of archives that can be in a state other than finished or failed.
const activeArchiveLimit = 4

// the name of the "index.html" file.  dezip will ignore files and directories
// in the archive if they have this name.
const indexFileName = "hidden.from.dezip.html"

// how many seconds before a search times out?
const searchTimeoutSeconds = 20

// the maximum number of search results (to avoid overloading browsers).
const searchResultLimit = 99999

// a singleton closed channel that's initialized in main().
var closedChannel chan struct{}

// the regexp [^a-zA-Z0-9].
var alphanum *regexp.Regexp

// which protocols can you use to fetch archives?  and which formats can those
// archives be in?  protocols are keyed by url scheme, and formats are keyed by
// file extension.
var protocols map[string]protocol
var formats map[string]archiveFormat

// protects the following global variables.
var globalMutex sync.Mutex
// the number of archives in a non-terminal state.  limited to
// activeArchiveLimit.
var activeArchives int

type cache struct {
    mutex sync.Mutex

    rootPath string
    metaPath string
    textPath string

    archivesByURL map[string]*archive
    // archives in the order they will be reclaimed (at the time of writing,
    // this is in creation order).
    archiveURLsToReclaim []string
    renderingArchiveURLs []string
    renderingCond *sync.Cond
}

func main() {
    var err error
    alphanum, err = regexp.Compile("[^a-zA-Z0-9]")
    if err != nil {
        log.Fatal(err)
    }
    protocols = map[string]protocol{
        "ftp": ftpProtocol{},
        "gemini": geminiProtocol{},
        "gopher": gopherProtocol{},
        "http": httpProtocol{},
        "https": httpProtocol{},
    }
    formats = map[string]archiveFormat{
        ".zip": zipArchiveFormat{},

        ".tgz": tgzArchiveFormat{},
        ".tar.gz": tgzArchiveFormat{},

        ".tb2": tbz2ArchiveFormat{},
        ".tbz": tbz2ArchiveFormat{},
        ".tbz2": tbz2ArchiveFormat{},
        ".tar.bz2": tbz2ArchiveFormat{},

        ".txz": txzArchiveFormat{},
        ".tar.xz": txzArchiveFormat{},
    }
    closedChannel = make(chan struct{})
    close(closedChannel)

    workingDirectory, err := os.Getwd()
    if err != nil {
        log.Fatal(err)
    }
    c := &cache{
        rootPath: path.Join(workingDirectory, "root"),
        textPath: path.Join(workingDirectory, "text"),
        metaPath: path.Join(workingDirectory, "meta"),
    }
    c.renderingCond = sync.NewCond(&c.mutex)

    // decode existing archive metadata.
    c.archivesByURL, err = loadArchivesFromMetadata(c.metaPath)
    if err != nil {
        log.Fatal(err)
    }
    // sort by creation time to put the archives in reclamation order.
    var a []struct{url string; time time.Time}
    for k, v := range c.archivesByURL {
        a = append(a, struct{url string; time time.Time}{ k, v.creationTime })
    }
    sort.Slice(a, func (i, j int) bool {
        return a[i].time.Before(a[j].time)
    })
    for _, v := range a {
        c.archiveURLsToReclaim = append(c.archiveURLsToReclaim, v.url)
    }

    // find tmlanguage files.
    var languages []string
    if syntaxEnv, ok := os.LookupEnv("DEZIP_SYNTAX"); ok {
        files, err := ioutil.ReadDir(syntaxEnv)
        if err != nil {
            log.Fatal(err)
        }
        for _, file := range files {
            languages = append(languages, path.Join(syntaxEnv, file.Name()))
        }
    }

    // start the renderer goroutines.
    for i := 0; i < numberOfRenderers; i++ {
        go newRenderer(languages).renderLoop(c)
    }

    // start the reclamation goroutine.
    go c.reclaimLoop()

    go func () {
        // on exit, reclaim all unfinished archives.
        signals := make(chan os.Signal, 1)
        signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)
        <-signals
        c.mutex.Lock()
        for url, ar := range c.archivesByURL {
            c.mutex.Unlock()
            ar.mutex.Lock()
            if ar.state != archiveStateFinished {
                ar.mutex.Unlock()
                c.reclaim(url)
            }
            c.mutex.Lock()
        }
        os.Exit(0)
    }()
    // start the web server.
    log.Fatal(http.ListenAndServe("127.0.0.1:8001", c))
}

func (c *cache) ServeHTTP(response http.ResponseWriter, request *http.Request) {
    if len(request.URL.Path) > URLPathLimit {
        response.WriteHeader(404)
        fmt.Fprint(response, "404 invalid url")
        return
    }
    if request.URL.Path == "/" {
        response.Header().Add("Location", rewriteURLv1(strings.Split("/" + thisArchive, "/")) + "dezip/README.md")
        response.WriteHeader(302)
        return
    }
    components := strings.SplitN(request.URL.Path, "/", URLComponentLimit + 1)
    if len(components) == 2 {
        // this is so things still work without the usual reverse proxy deployment.
        http.ServeFile(response, request, path.Join(c.rootPath, request.URL.Path))
        return
    }
    if len(components) > URLComponentLimit || len(components) < 2 || components[0] != "" {
        response.WriteHeader(404)
        fmt.Fprint(response, "404 invalid url")
        return
    }
    rewrittenPath := ""
    if len(components) >= 3 && strings.HasSuffix(components[1], ":") {
        rewrittenPath = rewriteURLv1(components)
        components = strings.Split(rewrittenPath, "/")
    }
    if components[1] != "v1" {
        // plan ahead with a version number.
        response.WriteHeader(404)
        fmt.Fprint(response, "404 unrecognized version")
    } else if len(components) < 3 {
        response.WriteHeader(404)
        fmt.Fprint(response, "404 no path length specified")
    } else {
        // components[2] counts the components in the path to the archive root.
        // the rest are the path to the file or directory within the archive.
        length, err := strconv.Atoi(components[2])
        if err != nil || length < 4 || length >= len(components) {
            response.WriteHeader(404)
            fmt.Fprint(response, "404 invalid path length")
            return
        }
        var p page
        archiveComponents := components[:length]
        pathComponents := components[length:]
        if len(pathComponents) > 0 && pathComponents[len(pathComponents)-1] == "" {
            p.isDirectory = true
            pathComponents = pathComponents[:len(pathComponents)-1]
        }
        p.name = strings.Join(pathComponents, "/")

        // look up the proper protocol based on the scheme.  (https, gopher...)
        scheme := archiveComponents[3]
        fetchComponents := archiveComponents[4:]
        protocol, ok := protocols[scheme]
        if !ok {
            response.WriteHeader(404)
            p.writeErrorPage(response, fmt.Errorf("i don't know how to download %s:// urls", scheme))
            return
        }

        // construct the url which locates the archive.
        p.archiveURL = fmt.Sprintf("%s://%s", scheme, strings.Join(fetchComponents, "/"))

        if len(request.URL.Query()["remove"]) > 0 {
            response.Header().Set("Content-Type", "text/html;charset=utf-8")
            if request.Method == "POST" {
                c.mutex.Lock()
                archive := c.archivesByURL[p.archiveURL]
                c.mutex.Unlock()
                if archive != nil {
                    archive.mutex.Lock()
                    archive.transitionToState(archiveStateFailed)
                    archive.failureReason = fmt.Errorf("archive removed using ?remove query parameter")
                    archive.mutex.Unlock()
                    if err := c.reclaim(p.archiveURL); err != nil {
                        log.Print(err)
                    }
                    p.writeRemoveButtonPage(response, "archive removed.")
                } else {
                    p.writeRemoveButtonPage(response, "archive not found.")
                }
            } else {
                p.writeRemoveButtonPage(response, "")
            }
            return
        }

        // check whether an archive downloaded (or currently downloading) from
        // this url is in the cache.  if not, create a new empty archive.
        c.mutex.Lock()
        archive := c.archivesByURL[p.archiveURL]
        if archive == nil {
            archive = newArchive(strings.Join(archiveComponents, "/"))
            if archive != nil {
                c.archivesByURL[p.archiveURL] = archive
                c.archiveURLsToReclaim = append(c.archiveURLsToReclaim, p.archiveURL)
            }
        }
        c.mutex.Unlock()

        if archive == nil {
            response.WriteHeader(503)
            p.writeErrorPage(response, fmt.Errorf("too many concurrent downloads; try again later"))
            return
        }

        archive.mutex.Lock()
        if archive.state == archiveStateInitial {
            var format archiveFormat
            for extension, fmt := range formats {
                if strings.HasSuffix(p.archiveURL, extension) {
                    format = fmt
                    break
                }
            }
            if format == nil {
                archive.transitionToState(archiveStateFailed)
                archive.failureReason = fmt.Errorf("based on its file extension, %v doesn't look like an archive file", fetchComponents[len(fetchComponents)-1])
            } else {
                // if the archive is newly initialized, start the download and
                // transition to the downloading state.
                archive.transitionToState(archiveStateDownloading)
                archive.progress.estimatedContentLength = archiveSizeLimit
                go func () {
                    defer func () {
                        if r := recover(); r != nil {
                            log.Print("recovered in download: ", r, "\n", string(debug.Stack()))
                            archive.mutex.Lock()
                            archive.transitionToState(archiveStateFailed)
                            archive.failureReason = fmt.Errorf("panic during download: %v\n%v", r, string(debug.Stack()))
                            archive.mutex.Unlock()
                        }
                    }()
                    if err := c.download(p, format, protocol, archive); err != nil {
                        archive.mutex.Lock()
                        archive.transitionToState(archiveStateFailed)
                        archive.failureReason = err
                        archive.mutex.Unlock()
                    }
                    archive.mutex.Lock()
                    state := archive.state
                    archive.mutex.Unlock()
                    if state == archiveStateFailed {
                        c.reclaimFiles(archive.path)
                    }
                }()
            }
        }
        timeout := 1 * time.Second
        if len(request.Header["X-Dezip-Progress"]) > 0 {
            // deliver xhr progress updates immediately.
            timeout = 0
        } else if archive.state == archiveStateFailed {
            // there's no reason to wait if no further progress will be made.
            timeout = 0
        } else if archive.state == archiveStateRendering {
            // use a large timeout -- the file should be rendered right away
            // and the user wants to see it.  there's also no fallback page
            // like a progress bar in this case.
            timeout = 10 * time.Second
        }
        lineNumber := request.URL.Query()["line"]
        searchQuery := request.URL.Query()["search"]
        directorySearch := len(searchQuery) > 0 && p.isDirectory
        var ready chan struct{}
        if directorySearch {
            // directory searches require the entire archive to be downloaded.
            ready = archive.downloaded
        } else {
            // request that the file be rendered.  returns a channel that blocks
            // until the file is finished rendering.
            ready = archive.requestRender(p.name)
        }
        originalState := archive.state
        archive.mutex.Unlock()

        // wait a bit for the file to finish rendering.
        select {
        case <-ready:
            // either the file was rendered or the archive is in the finished
            // state (in this state the filesystem is the source of truth).
            // send the file, if it exists, as the response.
            if len(rewrittenPath) > 0 {
                // redirect to the /vN/... path which supports browsing within
                // the archive.
                archive.mutex.Lock()
                dir := archive.initialDirectory
                archive.mutex.Unlock()
                response.Header().Add("Location", path.Join(rewrittenPath, dir) + "/")
                response.WriteHeader(302)
                break
            }
            var filename string
            var info os.FileInfo
            if len(searchQuery) > 0 {
                filename = path.Join(c.textPath, request.URL.Path)
                info, err = os.Stat(filename)
            }
            if info == nil || err != nil || info.IsDir() {
                filename = path.Join(c.rootPath, request.URL.Path)
                info, err = os.Stat(filename)
            }
            var f *os.File
            if err == nil {
                if info.IsDir() {
                    if !strings.HasSuffix(request.URL.Path, "/") {
                        response.Header().Add("Location", request.URL.Path + "/")
                        response.WriteHeader(302)
                        break
                    }
                    f, err = os.Open(path.Join(filename, indexFileName))
                } else {
                    f, err = os.Open(filename)
                }
            }
            if err != nil {
                // this is where archive 404s are reported.
                response.WriteHeader(404)
                fmt.Fprint(response, "404 not found")
                break
            }
            defer f.Close()
            response.Header().Set("Content-Type", "text/html;charset=utf-8")
            if directorySearch {
                filter := ""
                for _, v := range request.Cookies() {
                    if v.Name == "filter" {
                        filter, err = url.PathUnescape(v.Value)
                        if err == nil {
                            break
                        }
                    }
                }
                results := make(chan searchResult, 5)
                go c.search(archive, searchQuery[0], filter, results)
                p.writeSearchResultsPage(response, searchQuery[0], filter, results)
            } else if len(searchQuery) > 0 {
                insertSearchAnchors(response, f, searchQuery[0])
            } else if len(lineNumber) > 0 {
                insertLineNumberAnchor(response, f, lineNumber[0])
            } else {
                io.Copy(response, f)
            }
        case <-time.After(timeout):
            // the file wasn't rendered, even after the timeout.  what happens
            // next depends on the archive state.
            archive.mutex.Lock()
            state := archive.state
            reason := archive.failureReason
            progress := archive.progress
            archive.mutex.Unlock()
            switch state {
            case archiveStateDownloading:
                // while downloading, show a progress bar.
                p.writeProgressPage(response, progress)
            case archiveStateRendering:
                // there are two possibilities here:
                // - the timeout expired while waiting for a file to render.
                // - the state changed from downloading to rendering.
                // in the first case, show an error.  in the second case, have
                // the client retry the request by issuing a redirect.
                if originalState == archiveStateRendering {
                    response.WriteHeader(503)
                    fmt.Fprintln(response, "error 503")
                    fmt.Fprintln(response, "this file is taking a long time to render.")
                    fmt.Fprintln(response, "you can refresh if you want to keep waiting for it.")
                } else {
                    response.Header().Add("Location", request.URL.Path)
                    response.WriteHeader(302)
                }
            case archiveStateFinished:
                // the state changed to finished.  retry the request in case
                // the timeout expired just before the archive finished
                // rendering.
                response.Header().Add("Location", request.URL.Path)
                response.WriteHeader(302)
            case archiveStateFailed:
                response.WriteHeader(503)
                p.writeErrorPage(response, reason)
            default:
                response.WriteHeader(503)
                p.writeErrorPage(response, fmt.Errorf("unexpected archive state %v", state))
            }
        }
    }
}

func rewriteURLv1(components []string) string {
    // rewrite urls of the form dezip.org/scheme://....
    // make sure to handle the case where scheme://... becomes scheme:/... due
    // to path normalization.
    path := components[2:]
    if components[2] == "" && len(components) >= 4 {
        path = components[3:]
    }
    scheme := strings.ToLower(components[1])
    return fmt.Sprintf("/v1/%d/%s/%s/", len(path) + 4, scheme[:len(scheme)-1], strings.Join(path, "/"))
}

// -- archive formats

type archiveFormat interface {
    download(*os.File, io.Reader) error
}

type zipArchiveFormat struct {}
func (a zipArchiveFormat) download(f *os.File, r io.Reader) error {
    _, err := io.Copy(f, r)
    return err
}

type tgzArchiveFormat struct {}
func (a tgzArchiveFormat) download(f *os.File, r io.Reader) error {
    gz, err := gzip.NewReader(r)
    if err != nil {
        return err
    }
    defer gz.Close()
    return downloadTar(f, gz)
}

type tbz2ArchiveFormat struct {}
func (a tbz2ArchiveFormat) download(f *os.File, r io.Reader) error {
    return downloadTar(f, bzip2.NewReader(r))
}

type txzArchiveFormat struct {}
func (a txzArchiveFormat) download(f *os.File, r io.Reader) error {
    xz, err := xz.NewReader(r, xz.DefaultDictMax)
    if err != nil {
        return err
    }
    return downloadTar(f, xz)
}

func downloadTar(f *os.File, r io.Reader) error {
    tr := tar.NewReader(r)
    zw := zip.NewWriter(f)
    var totalSize int64
    for {
        hdr, err := tr.Next()
        if err == io.EOF {
            break
        } else if err != nil {
            return err
        }
        totalSize += hdr.Size
        if totalSize > uncompressedArchiveSizeLimit {
            return fmt.Errorf("uncompressed archive size exceeded limit of %d bytes", uncompressedArchiveSizeLimit)
        }
        mode := os.FileMode(hdr.Mode)
        switch hdr.Typeflag {
        case tar.TypeReg:
        case tar.TypeLink:
            mode |= os.ModeSymlink
        case tar.TypeSymlink:
            mode |= os.ModeSymlink
        case tar.TypeChar:
        case tar.TypeBlock:
        case tar.TypeDir:
        case tar.TypeFifo:
            // show these.
        default:
            // hide anything else (e.g. the pax_global_header that appears in
            // linux tarballs).
            continue
        }
        zhdr := &zip.FileHeader{
            Name: hdr.Name,
            Method: zip.Store,
            Modified: hdr.ModTime,
        }
        zhdr.SetMode(mode)
        if hdr.Typeflag == tar.TypeDir {
            if len(zhdr.Name) == 0 {
                continue
            } else if zhdr.Name[len(zhdr.Name)-1] != '/' {
                zhdr.Name += "/"
            }
        }
        w, err := zw.CreateHeader(zhdr)
        if err != nil {
            return err
        }
        if mode & os.ModeSymlink != 0 {
            io.WriteString(w, hdr.Linkname)
        } else {
            if _, err := io.Copy(w, tr); err != nil {
                return err
            }
        }
    }
    if err := zw.Close(); err != nil {
        return err
    }
    return nil
}

// -- protocols

type protocol interface {
    fetch(string) (response, error)
}
type response struct {
    body io.ReadCloser

    // may be negative, indicating an unknown content length.
    contentLength int64
}

type httpProtocol struct {}
func (p httpProtocol) fetch(url string) (response, error) {
    res, err := http.Get(url)
    if err != nil {
        return response{}, err
    }
    if res.StatusCode < 200 || res.StatusCode > 299 {
        return response{}, fmt.Errorf("%s when fetching %s", res.Status, url)
    }
    return response{ res.Body, res.ContentLength }, nil
}

type gopherProtocol struct {}
func (p gopherProtocol) fetch(url string) (response, error) {
    res, err := gopher.Get(url)
    if err != nil {
        return response{}, err
    }
    if res.Body == nil {
        return response{}, fmt.Errorf("gopher response had nil body - is this a directory page?")
    }
    return response{ res.Body, -1 }, nil
}

type geminiProtocol struct {}
func (p geminiProtocol) fetch(url string) (response, error) {
    res, err := gemini.DefaultClient.Fetch(url)
    if err != nil {
        return response{}, err
    }
    return response{ res.Body, -1 }, nil
}

type ftpProtocol struct {}
func (p ftpProtocol) fetch(rawurl string) (response, error) {
    url, err := url.Parse(rawurl)
    if err != nil {
        return response{}, err
    }
    host := url.Host
    // this doesn't work with ipv6 addresses... but who is connecting to an ftp
    // server via a raw ipv6 address?  and why doesn't the go standard library
    // provide a reliable way to append a port to a hostname?
    if !strings.Contains(host, ":") {
        host += ":21"
    }
    conn, err := ftp.Dial(host)
    if err != nil {
        return response{}, err
    }
    conn.Login("anonymous", "anonymous")
    res := response{ contentLength: -1 }
    entries, err := conn.List(url.Path)
    if err == nil && len(entries) == 1 {
        res.contentLength = int64(entries[0].Size)
    }
    res.body, err = conn.Retr(url.Path)
    if err != nil {
        conn.Quit()
        return response{}, err
    }
    return res, nil
}