Repository: caddyserver/caddy
File: middleware/fileserver.go (Go)

Code before:
package middleware

import (
	"fmt"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"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) {
	upath := r.URL.Path
	if !strings.HasPrefix(upath, "/") {
		upath = "/" + upath
		r.URL.Path = upath
	}
	return fh.serveFile(w, r, path.Clean(upath))
}

// 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
		w.Header().Set("Retry-After", "5") // TODO: 5 seconds enough delay? Or too much?
		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 url[len(url)-1] != '/' {
			redirect(w, r, path.Base(url)+"/")
			return http.StatusMovedPermanently, nil
		}
	} else {
		// Ensure no / at end of file url
		if url[len(url)-1] == '/' {
			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("\"%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",
}


Review comment (bug):
It's a small thing, but I really don't like exposing more information than necessary.  While the last modification time may also be returned by the http request, putting it in here seems "wrong".

However, that can be changed later on.  :)


Code after:
package middleware

import (
	"fmt"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"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) {
	upath := r.URL.Path
	if !strings.HasPrefix(upath, "/") {
		upath = "/" + upath
		r.URL.Path = upath
	}
	return fh.serveFile(w, r, path.Clean(upath))
}

// 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
		w.Header().Set("Retry-After", "5") // TODO: 5 seconds enough delay? Or too much?
		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 url[len(url)-1] != '/' {
			redirect(w, r, path.Base(url)+"/")
			return http.StatusMovedPermanently, nil
		}
	} else {
		// Ensure no / at end of file url
		if url[len(url)-1] == '/' {
			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",
}