// Copyright 2009 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // HTTP file system request handler package http import ( "errors" "fmt" "io" "mime" "mime/multipart" "net/textproto" "net/url" "os" "path" "path/filepath" "strconv" "strings" "time" ) // A Dir implements FileSystem using the native file system restricted to a // specific directory tree. // // While the FileSystem.Open method takes '/'-separated paths, a Dir's string // value is a filename on the native file system, not a URL, so it is separated // by filepath.Separator, which isn't necessarily '/'. // // An empty Dir is treated as ".". type Dir string func (d Dir) Open(name string) (File, error) { if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 || strings.Contains(name, "\x00") { return nil, errors.New("http: invalid character in file path") } dir := string(d) if dir == "" { dir = "." } f, err := os.Open(filepath.Join(dir, filepath.FromSlash(path.Clean("/"+name)))) if err != nil { return nil, err } return f, nil } // A FileSystem implements access to a collection of named files. // The elements in a file path are separated by slash ('/', U+002F) // characters, regardless of host operating system convention. type FileSystem interface { Open(name string) (File, error) } // A File is returned by a FileSystem's Open method and can be // served by the FileServer implementation. // // The methods should behave the same as those on an *os.File. type File interface { io.Closer io.Reader Readdir(count int) ([]os.FileInfo, error) Seek(offset int64, whence int) (int64, error) Stat() (os.FileInfo, error) } func dirList(w ResponseWriter, f File) { w.Header().Set("Content-Type", "text/html; charset=utf-8") fmt.Fprintf(w, "
\n")
	for {
		dirs, err := f.Readdir(100)
		if err != nil || len(dirs) == 0 {
			break
		}
		for _, d := range dirs {
			name := d.Name()
			if d.IsDir() {
				name += "/"
			}
			// name may contain '?' or '#', which must be escaped to remain
			// part of the URL path, and not indicate the start of a query
			// string or fragment.
			url := url.URL{Path: name}
			fmt.Fprintf(w, "%s\n", url.String(), htmlReplacer.Replace(name))
		}
	}
	fmt.Fprintf(w, "
\n") } // ServeContent replies to the request using the content in the // provided ReadSeeker. The main benefit of ServeContent over io.Copy // is that it handles Range requests properly, sets the MIME type, and // handles If-Modified-Since requests. // // If the response's Content-Type header is not set, ServeContent // first tries to deduce the type from name's file extension and, // if that fails, falls back to reading the first block of the content // and passing it to DetectContentType. // The name is otherwise unused; in particular it can be empty and is // never sent in the response. // // If modtime is not the zero time, ServeContent includes it in a // Last-Modified header in the response. If the request includes an // If-Modified-Since header, ServeContent uses modtime to decide // whether the content needs to be sent at all. // // The content's Seek method must work: ServeContent uses // a seek to the end of the content to determine its size. // // If the caller has set w's ETag header, ServeContent uses it to // handle requests using If-Range and If-None-Match. // // Note that *os.File implements the io.ReadSeeker interface. func ServeContent(w ResponseWriter, req *Request, name string, modtime time.Time, content io.ReadSeeker) { sizeFunc := func() (int64, error) { size, err := content.Seek(0, os.SEEK_END) if err != nil { return 0, errSeeker } _, err = content.Seek(0, os.SEEK_SET) if err != nil { return 0, errSeeker } return size, nil } serveContent(w, req, name, modtime, sizeFunc, content) } // errSeeker is returned by ServeContent's sizeFunc when the content // doesn't seek properly. The underlying Seeker's error text isn't // included in the sizeFunc reply so it's not sent over HTTP to end // users. var errSeeker = errors.New("seeker can't seek") // if name is empty, filename is unknown. (used for mime type, before sniffing) // if modtime.IsZero(), modtime is unknown. // content must be seeked to the beginning of the file. // The sizeFunc is called at most once. Its error, if any, is sent in the HTTP response. func serveContent(w ResponseWriter, r *Request, name string, modtime time.Time, sizeFunc func() (int64, error), content io.ReadSeeker) { if checkLastModified(w, r, modtime) { return } rangeReq, done := checkETag(w, r, modtime) if done { return } code := StatusOK // If Content-Type isn't set, use the file's extension to find it, but // if the Content-Type is unset explicitly, do not sniff the type. ctypes, haveType := w.Header()["Content-Type"] var ctype string if !haveType { ctype = mime.TypeByExtension(filepath.Ext(name)) if ctype == "" { // read a chunk to decide between utf-8 text and binary var buf [sniffLen]byte n, _ := io.ReadFull(content, buf[:]) ctype = DetectContentType(buf[:n]) _, err := content.Seek(0, os.SEEK_SET) // rewind to output whole file if err != nil { Error(w, "seeker can't seek", StatusInternalServerError) return } } w.Header().Set("Content-Type", ctype) } else if len(ctypes) > 0 { ctype = ctypes[0] } size, err := sizeFunc() if err != nil { Error(w, err.Error(), StatusInternalServerError) return } // handle Content-Range header. sendSize := size var sendContent io.Reader = content if size >= 0 { ranges, err := parseRange(rangeReq, size) if err != nil { Error(w, err.Error(), StatusRequestedRangeNotSatisfiable) return } if sumRangesSize(ranges) > size { // The total number of bytes in all the ranges // is larger than the size of the file by // itself, so this is probably an attack, or a // dumb client. Ignore the range request. ranges = nil } switch { case len(ranges) == 1: // RFC 2616, Section 14.16: // "When an HTTP message includes the content of a single // range (for example, a response to a request for a // single range, or to a request for a set of ranges // that overlap without any holes), this content is // transmitted with a Content-Range header, and a // Content-Length header showing the number of bytes // actually transferred. // ... // A response to a request for a single range MUST NOT // be sent using the multipart/byteranges media type." ra := ranges[0] if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil { Error(w, err.Error(), StatusRequestedRangeNotSatisfiable) return } sendSize = ra.length code = StatusPartialContent w.Header().Set("Content-Range", ra.contentRange(size)) case len(ranges) > 1: sendSize = rangesMIMESize(ranges, ctype, size) code = StatusPartialContent pr, pw := io.Pipe() mw := multipart.NewWriter(pw) w.Header().Set("Content-Type", "multipart/byteranges; boundary="+mw.Boundary()) sendContent = pr defer pr.Close() // cause writing goroutine to fail and exit if CopyN doesn't finish. go func() { for _, ra := range ranges { part, err := mw.CreatePart(ra.mimeHeader(ctype, size)) if err != nil { pw.CloseWithError(err) return } if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil { pw.CloseWithError(err) return } if _, err := io.CopyN(part, content, ra.length); err != nil { pw.CloseWithError(err) return } } mw.Close() pw.Close() }() } w.Header().Set("Accept-Ranges", "bytes") if w.Header().Get("Content-Encoding") == "" { w.Header().Set("Content-Length", strconv.FormatInt(sendSize, 10)) } } w.WriteHeader(code) if r.Method != "HEAD" { io.CopyN(w, sendContent, sendSize) } } // modtime is the modification time of the resource to be served, or IsZero(). // return value is whether this request is now complete. func checkLastModified(w ResponseWriter, r *Request, modtime time.Time) bool { if modtime.IsZero() { return false } // The Date-Modified header truncates sub-second precision, so // use mtime < t+1s instead of mtime <= t to check for unmodified. if t, err := time.Parse(TimeFormat, r.Header.Get("If-Modified-Since")); err == nil && modtime.Before(t.Add(1*time.Second)) { h := w.Header() delete(h, "Content-Type") delete(h, "Content-Length") w.WriteHeader(StatusNotModified) return true } w.Header().Set("Last-Modified", modtime.UTC().Format(TimeFormat)) return false } // checkETag implements If-None-Match and If-Range checks. // // The ETag or modtime must have been previously set in the // ResponseWriter's headers. The modtime is only compared at second // granularity and may be the zero value to mean unknown. // // The return value is the effective request "Range" header to use and // whether this request is now considered done. func checkETag(w ResponseWriter, r *Request, modtime time.Time) (rangeReq string, done bool) { etag := w.Header().get("Etag") rangeReq = r.Header.get("Range") // Invalidate the range request if the entity doesn't match the one // the client was expecting. // "If-Range: version" means "ignore the Range: header unless version matches the // current file." // We only support ETag versions. // The caller must have set the ETag on the response already. if ir := r.Header.get("If-Range"); ir != "" && ir != etag { // The If-Range value is typically the ETag value, but it may also be // the modtime date. See golang.org/issue/8367. timeMatches := false if !modtime.IsZero() { if t, err := ParseTime(ir); err == nil && t.Unix() == modtime.Unix() { timeMatches = true } } if !timeMatches { rangeReq = "" } } if inm := r.Header.get("If-None-Match"); inm != "" { // Must know ETag. if etag == "" { return rangeReq, false } // TODO(bradfitz): non-GET/HEAD requests require more work: // sending a different status code on matches, and // also can't use weak cache validators (those with a "W/ // prefix). But most users of ServeContent will be using // it on GET or HEAD, so only support those for now. if r.Method != "GET" && r.Method != "HEAD" { return rangeReq, false } // TODO(bradfitz): deal with comma-separated or multiple-valued // list of If-None-match values. For now just handle the common // case of a single item. if inm == etag || inm == "*" { h := w.Header() delete(h, "Content-Type") delete(h, "Content-Length") w.WriteHeader(StatusNotModified) return "", true } } return rangeReq, false } // name is '/'-separated, not filepath.Separator. func serveFile(w ResponseWriter, r *Request, fs FileSystem, name string, redirect bool) { const indexPage = "/index.html" // redirect .../index.html to .../ // can't use Redirect() because that would make the path absolute, // which would be a problem running under StripPrefix if strings.HasSuffix(r.URL.Path, indexPage) { localRedirect(w, r, "./") return } f, err := fs.Open(name) if err != nil { // TODO expose actual error? NotFound(w, r) return } defer f.Close() d, err1 := f.Stat() if err1 != nil { // TODO expose actual error? NotFound(w, r) return } if redirect { // redirect to canonical path: / at end of directory url // r.URL.Path always begins with / url := r.URL.Path if d.IsDir() { if url[len(url)-1] != '/' { localRedirect(w, r, path.Base(url)+"/") return } } else { if url[len(url)-1] == '/' { localRedirect(w, r, "../"+path.Base(url)) return } } } // use contents of index.html for directory, if present if d.IsDir() { index := strings.TrimSuffix(name, "/") + indexPage ff, err := fs.Open(index) if err == nil { defer ff.Close() dd, err := ff.Stat() if err == nil { name = index d = dd f = ff } } } // Still a directory? (we didn't find an index.html file) if d.IsDir() { if checkLastModified(w, r, d.ModTime()) { return } dirList(w, f) return } // serveContent will check modification time sizeFunc := func() (int64, error) { return d.Size(), nil } serveContent(w, r, d.Name(), d.ModTime(), sizeFunc, f) } // localRedirect gives a Moved Permanently response. // It does not convert relative paths to absolute paths like Redirect does. func localRedirect(w ResponseWriter, r *Request, newPath string) { if q := r.URL.RawQuery; q != "" { newPath += "?" + q } w.Header().Set("Location", newPath) w.WriteHeader(StatusMovedPermanently) } // ServeFile replies to the request with the contents of the named file or directory. func ServeFile(w ResponseWriter, r *Request, name string) { dir, file := filepath.Split(name) serveFile(w, r, Dir(dir), file, false) } type fileHandler struct { root FileSystem } // FileServer returns a handler that serves HTTP requests // with the contents of the file system rooted at root. // // To use the operating system's file system implementation, // use http.Dir: // // http.Handle("/", http.FileServer(http.Dir("/tmp"))) func FileServer(root FileSystem) Handler { return &fileHandler{root} } func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) { upath := r.URL.Path if !strings.HasPrefix(upath, "/") { upath = "/" + upath r.URL.Path = upath } serveFile(w, r, f.root, path.Clean(upath), true) } // httpRange specifies the byte range to be sent to the client. type httpRange struct { start, length int64 } func (r httpRange) contentRange(size int64) string { return fmt.Sprintf("bytes %d-%d/%d", r.start, r.start+r.length-1, size) } func (r httpRange) mimeHeader(contentType string, size int64) textproto.MIMEHeader { return textproto.MIMEHeader{ "Content-Range": {r.contentRange(size)}, "Content-Type": {contentType}, } } // parseRange parses a Range header string as per RFC 2616. func parseRange(s string, size int64) ([]httpRange, error) { if s == "" { return nil, nil // header not present } const b = "bytes=" if !strings.HasPrefix(s, b) { return nil, errors.New("invalid range") } var ranges []httpRange for _, ra := range strings.Split(s[len(b):], ",") { ra = strings.TrimSpace(ra) if ra == "" { continue } i := strings.Index(ra, "-") if i < 0 { return nil, errors.New("invalid range") } start, end := strings.TrimSpace(ra[:i]), strings.TrimSpace(ra[i+1:]) var r httpRange if start == "" { // If no start is specified, end specifies the // range start relative to the end of the file. i, err := strconv.ParseInt(end, 10, 64) if err != nil { return nil, errors.New("invalid range") } if i > size { i = size } r.start = size - i r.length = size - r.start } else { i, err := strconv.ParseInt(start, 10, 64) if err != nil || i > size || i < 0 { return nil, errors.New("invalid range") } r.start = i if end == "" { // If no end is specified, range extends to end of the file. r.length = size - r.start } else { i, err := strconv.ParseInt(end, 10, 64) if err != nil || r.start > i { return nil, errors.New("invalid range") } if i >= size { i = size - 1 } r.length = i - r.start + 1 } } ranges = append(ranges, r) } return ranges, nil } // countingWriter counts how many bytes have been written to it. type countingWriter int64 func (w *countingWriter) Write(p []byte) (n int, err error) { *w += countingWriter(len(p)) return len(p), nil } // rangesMIMESize returns the number of bytes it takes to encode the // provided ranges as a multipart response. func rangesMIMESize(ranges []httpRange, contentType string, contentSize int64) (encSize int64) { var w countingWriter mw := multipart.NewWriter(&w) for _, ra := range ranges { mw.CreatePart(ra.mimeHeader(contentType, contentSize)) encSize += ra.length } mw.Close() encSize += int64(w) return } func sumRangesSize(ranges []httpRange) (size int64) { for _, ra := range ranges { size += ra.length } return }