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fileserver.go
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fileserver.go
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package middleware
import (
"fmt"
"math/rand"
"net/http"
"os"
"path"
"path/filepath"
"strconv"
"strings"
)
// This file contains a standard way for Caddy middleware
// to load files from the file system given a request
// URI and path to site root. Other middleware that load
// files should use these facilities.
// FileServer implements a production-ready file server
// and is the 'default' handler for all requests to Caddy.
// It simply loads and serves the URI requested. If Caddy is
// run without any extra configuration/directives, this is the
// only middleware handler that runs. It is not in its own
// folder like most other middleware handlers because it does
// not require a directive. It is a special case.
//
// FileServer is adapted from the one in net/http by
// the Go authors. Significant modifications have been made.
//
// Original license:
//
// 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.
func FileServer(root http.FileSystem, hide []string) Handler {
return &fileHandler{root: root, hide: hide}
}
type fileHandler struct {
root http.FileSystem
hide []string // list of files to treat as "Not Found"
}
func (fh *fileHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
// r.URL.Path has already been cleaned in caddy/server by path.Clean().
if r.URL.Path == "" {
r.URL.Path = "/"
}
return fh.serveFile(w, r, r.URL.Path)
}
// serveFile writes the specified file to the HTTP response.
// name is '/'-separated, not filepath.Separator.
func (fh *fileHandler) serveFile(w http.ResponseWriter, r *http.Request, name string) (int, error) {
// Prevent absolute path access on Windows.
// TODO remove when stdlib http.Dir fixes this.
if runtimeGoos == "windows" {
if filepath.IsAbs(name[1:]) {
return http.StatusNotFound, nil
}
}
f, err := fh.root.Open(name)
if err != nil {
if os.IsNotExist(err) {
return http.StatusNotFound, nil
} else if os.IsPermission(err) {
return http.StatusForbidden, err
}
// Likely the server is under load and ran out of file descriptors
backoff := int(3 + rand.Int31()%3) // 3–5 seconds to prevent a stampede
w.Header().Set("Retry-After", strconv.Itoa(backoff))
return http.StatusServiceUnavailable, err
}
defer f.Close()
d, err := f.Stat()
if err != nil {
if os.IsNotExist(err) {
return http.StatusNotFound, nil
} else if os.IsPermission(err) {
return http.StatusForbidden, err
}
// Return a different status code than above so as to distinguish these cases
return http.StatusInternalServerError, err
}
// redirect to canonical path
url := r.URL.Path
if d.IsDir() {
// Ensure / at end of directory url
if !strings.HasSuffix(url, "/") {
redirect(w, r, path.Base(url)+"/")
return http.StatusMovedPermanently, nil
}
} else {
// Ensure no / at end of file url
if strings.HasSuffix(url, "/") {
redirect(w, r, "../"+path.Base(url))
return http.StatusMovedPermanently, nil
}
}
// use contents of an index file, if present, for directory
if d.IsDir() {
for _, indexPage := range IndexPages {
index := strings.TrimSuffix(name, "/") + "/" + indexPage
ff, err := fh.root.Open(index)
if err == nil {
// this defer does not leak fds because previous iterations
// of the loop must have had an err, so nothing to close
defer ff.Close()
dd, err := ff.Stat()
if err == nil {
name = index
d = dd
f = ff
break
}
}
}
}
// Still a directory? (we didn't find an index file)
// Return 404 to hide the fact that the folder exists
if d.IsDir() {
return http.StatusNotFound, nil
}
// If file is on hide list.
if fh.isHidden(d) {
return http.StatusNotFound, nil
}
// Add ETag header
e := fmt.Sprintf(`W/"%x-%x"`, d.ModTime().Unix(), d.Size())
w.Header().Set("ETag", e)
// Note: Errors generated by ServeContent are written immediately
// to the response. This usually only happens if seeking fails (rare).
http.ServeContent(w, r, d.Name(), d.ModTime(), f)
return http.StatusOK, nil
}
// isHidden checks if file with FileInfo d is on hide list.
func (fh fileHandler) isHidden(d os.FileInfo) bool {
// If the file is supposed to be hidden, return a 404
// (TODO: If the slice gets large, a set may be faster)
for _, hiddenPath := range fh.hide {
// Check if the served file is exactly the hidden file.
if hFile, err := fh.root.Open(hiddenPath); err == nil {
fs, _ := hFile.Stat()
hFile.Close()
if os.SameFile(d, fs) {
return true
}
}
}
return false
}
// redirect is taken from http.localRedirect of the std lib. It
// sends an HTTP redirect to the client but will preserve the
// query string for the new path.
func redirect(w http.ResponseWriter, r *http.Request, newPath string) {
if q := r.URL.RawQuery; q != "" {
newPath += "?" + q
}
http.Redirect(w, r, newPath, http.StatusMovedPermanently)
}
// IndexPages is a list of pages that may be understood as
// the "index" files to directories.
var IndexPages = []string{
"index.html",
"index.htm",
"index.txt",
"default.html",
"default.htm",
"default.txt",
}