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// 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, "<pre>\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, "<a href=\"%s\">%s</a>\n", url.String(), htmlReplacer.Replace(name))
}
}
fmt.Fprintf(w, "</pre>\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 or Unix epoch, 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)
}
}
var unixEpochTime = time.Unix(0, 0)
// 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() || modtime.Equal(unixEpochTime) {
// If the file doesn't have a modtime (IsZero), or the modtime
// is obviously garbage (Unix time == 0), then ignore modtimes
// and don't process the If-Modified-Since header.
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 {
msg, code := toHTTPError(err)
Error(w, msg, code)
return
}
defer f.Close()
d, err1 := f.Stat()
if err1 != nil {
msg, code := toHTTPError(err)
Error(w, msg, code)
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)
}
// toHTTPError returns a non-specific HTTP error message and status code
// for a given non-nil error value. It's important that toHTTPError does not
// actually return err.Error(), since msg and httpStatus are returned to users,
// and historically Go's ServeContent always returned just "404 Not Found" for
// all errors. We don't want to start leaking information in error messages.
func toHTTPError(err error) (msg string, httpStatus int) {
if os.IsNotExist(err) {
return "404 page not found", StatusNotFound
}
if os.IsPermission(err) {
return "403 Forbidden", StatusForbidden
}
// Default:
return "500 Internal Server Error", StatusInternalServerError
}
// 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
}