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Diffstat (limited to 'src/net/http/fs.go')
| -rw-r--r-- | src/net/http/fs.go | 1057 |
1 files changed, 1057 insertions, 0 deletions
diff --git a/src/net/http/fs.go b/src/net/http/fs.go new file mode 100644 index 0000000..af7511a --- /dev/null +++ b/src/net/http/fs.go @@ -0,0 +1,1057 @@ +// 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" + "internal/safefilepath" + "io" + "io/fs" + "mime" + "mime/multipart" + "net/textproto" + "net/url" + "os" + "path" + "path/filepath" + "sort" + "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 '/'. +// +// Note that Dir could expose sensitive files and directories. Dir will follow +// symlinks pointing out of the directory tree, which can be especially dangerous +// if serving from a directory in which users are able to create arbitrary symlinks. +// Dir will also allow access to files and directories starting with a period, +// which could expose sensitive directories like .git or sensitive files like +// .htpasswd. To exclude files with a leading period, remove the files/directories +// from the server or create a custom FileSystem implementation. +// +// An empty Dir is treated as ".". +type Dir string + +// mapOpenError maps the provided non-nil error from opening name +// to a possibly better non-nil error. In particular, it turns OS-specific errors +// about opening files in non-directories into fs.ErrNotExist. See Issues 18984 and 49552. +func mapOpenError(originalErr error, name string, sep rune, stat func(string) (fs.FileInfo, error)) error { + if errors.Is(originalErr, fs.ErrNotExist) || errors.Is(originalErr, fs.ErrPermission) { + return originalErr + } + + parts := strings.Split(name, string(sep)) + for i := range parts { + if parts[i] == "" { + continue + } + fi, err := stat(strings.Join(parts[:i+1], string(sep))) + if err != nil { + return originalErr + } + if !fi.IsDir() { + return fs.ErrNotExist + } + } + return originalErr +} + +// Open implements [FileSystem] using [os.Open], opening files for reading rooted +// and relative to the directory d. +func (d Dir) Open(name string) (File, error) { + path, err := safefilepath.FromFS(path.Clean("/" + name)) + if err != nil { + return nil, errors.New("http: invalid or unsafe file path") + } + dir := string(d) + if dir == "" { + dir = "." + } + fullName := filepath.Join(dir, path) + f, err := os.Open(fullName) + if err != nil { + return nil, mapOpenError(err, fullName, filepath.Separator, os.Stat) + } + 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. +// See the [FileServer] function to convert a FileSystem to a [Handler]. +// +// This interface predates the [fs.FS] interface, which can be used instead: +// the [FS] adapter function converts an fs.FS to a FileSystem. +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 + io.Seeker + Readdir(count int) ([]fs.FileInfo, error) + Stat() (fs.FileInfo, error) +} + +type anyDirs interface { + len() int + name(i int) string + isDir(i int) bool +} + +type fileInfoDirs []fs.FileInfo + +func (d fileInfoDirs) len() int { return len(d) } +func (d fileInfoDirs) isDir(i int) bool { return d[i].IsDir() } +func (d fileInfoDirs) name(i int) string { return d[i].Name() } + +type dirEntryDirs []fs.DirEntry + +func (d dirEntryDirs) len() int { return len(d) } +func (d dirEntryDirs) isDir(i int) bool { return d[i].IsDir() } +func (d dirEntryDirs) name(i int) string { return d[i].Name() } + +func dirList(w ResponseWriter, r *Request, f File) { + // Prefer to use ReadDir instead of Readdir, + // because the former doesn't require calling + // Stat on every entry of a directory on Unix. + var dirs anyDirs + var err error + if d, ok := f.(fs.ReadDirFile); ok { + var list dirEntryDirs + list, err = d.ReadDir(-1) + dirs = list + } else { + var list fileInfoDirs + list, err = f.Readdir(-1) + dirs = list + } + + if err != nil { + logf(r, "http: error reading directory: %v", err) + Error(w, "Error reading directory", StatusInternalServerError) + return + } + sort.Slice(dirs, func(i, j int) bool { return dirs.name(i) < dirs.name(j) }) + + w.Header().Set("Content-Type", "text/html; charset=utf-8") + fmt.Fprintf(w, "<pre>\n") + for i, n := 0, dirs.len(); i < n; i++ { + name := dirs.name(i) + if dirs.isDir(i) { + 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-Match, If-Unmodified-Since, If-None-Match, If-Modified-Since, +// and If-Range 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 formatted per RFC 7232, section 2.3, +// ServeContent uses it to handle requests using If-Match, If-None-Match, or If-Range. +// +// 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, io.SeekEnd) + if err != nil { + return 0, errSeeker + } + _, err = content.Seek(0, io.SeekStart) + 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") + +// errNoOverlap is returned by serveContent's parseRange if first-byte-pos of +// all of the byte-range-spec values is greater than the content size. +var errNoOverlap = errors.New("invalid range: failed to overlap") + +// 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) { + setLastModified(w, modtime) + done, rangeReq := checkPreconditions(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, io.SeekStart) // 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 + } + if size < 0 { + // Should never happen but just to be sure + Error(w, "negative content size computed", StatusInternalServerError) + return + } + + // handle Content-Range header. + sendSize := size + var sendContent io.Reader = content + ranges, err := parseRange(rangeReq, size) + switch err { + case nil: + case errNoOverlap: + if size == 0 { + // Some clients add a Range header to all requests to + // limit the size of the response. If the file is empty, + // ignore the range header and respond with a 200 rather + // than a 416. + ranges = nil + break + } + w.Header().Set("Content-Range", fmt.Sprintf("bytes */%d", size)) + fallthrough + default: + 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 7233, Section 4.1: + // "If a single part is being transferred, the server + // generating the 206 response MUST generate a + // Content-Range header field, describing what range + // of the selected representation is enclosed, and a + // payload consisting of the range. + // ... + // A server MUST NOT generate a multipart response to + // a request for a single range, since a client that + // does not request multiple parts might not support + // multipart responses." + ra := ranges[0] + if _, err := content.Seek(ra.start, io.SeekStart); 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, io.SeekStart); 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") + + // We should be able to unconditionally set the Content-Length here. + // + // However, there is a pattern observed in the wild that this breaks: + // The user wraps the ResponseWriter in one which gzips data written to it, + // and sets "Content-Encoding: gzip". + // + // The user shouldn't be doing this; the serveContent path here depends + // on serving seekable data with a known length. If you want to compress + // on the fly, then you shouldn't be using ServeFile/ServeContent, or + // you should compress the entire file up-front and provide a seekable + // view of the compressed data. + // + // However, since we've observed this pattern in the wild, and since + // setting Content-Length here breaks code that mostly-works today, + // skip setting Content-Length if the user set Content-Encoding. + // + // If this is a range request, always set Content-Length. + // If the user isn't changing the bytes sent in the ResponseWrite, + // the Content-Length will be correct. + // If the user is changing the bytes sent, then the range request wasn't + // going to work properly anyway and we aren't worse off. + // + // A possible future improvement on this might be to look at the type + // of the ResponseWriter, and always set Content-Length if it's one + // that we recognize. + if len(ranges) > 0 || 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) + } +} + +// scanETag determines if a syntactically valid ETag is present at s. If so, +// the ETag and remaining text after consuming ETag is returned. Otherwise, +// it returns "", "". +func scanETag(s string) (etag string, remain string) { + s = textproto.TrimString(s) + start := 0 + if strings.HasPrefix(s, "W/") { + start = 2 + } + if len(s[start:]) < 2 || s[start] != '"' { + return "", "" + } + // ETag is either W/"text" or "text". + // See RFC 7232 2.3. + for i := start + 1; i < len(s); i++ { + c := s[i] + switch { + // Character values allowed in ETags. + case c == 0x21 || c >= 0x23 && c <= 0x7E || c >= 0x80: + case c == '"': + return s[:i+1], s[i+1:] + default: + return "", "" + } + } + return "", "" +} + +// etagStrongMatch reports whether a and b match using strong ETag comparison. +// Assumes a and b are valid ETags. +func etagStrongMatch(a, b string) bool { + return a == b && a != "" && a[0] == '"' +} + +// etagWeakMatch reports whether a and b match using weak ETag comparison. +// Assumes a and b are valid ETags. +func etagWeakMatch(a, b string) bool { + return strings.TrimPrefix(a, "W/") == strings.TrimPrefix(b, "W/") +} + +// condResult is the result of an HTTP request precondition check. +// See https://tools.ietf.org/html/rfc7232 section 3. +type condResult int + +const ( + condNone condResult = iota + condTrue + condFalse +) + +func checkIfMatch(w ResponseWriter, r *Request) condResult { + im := r.Header.Get("If-Match") + if im == "" { + return condNone + } + for { + im = textproto.TrimString(im) + if len(im) == 0 { + break + } + if im[0] == ',' { + im = im[1:] + continue + } + if im[0] == '*' { + return condTrue + } + etag, remain := scanETag(im) + if etag == "" { + break + } + if etagStrongMatch(etag, w.Header().get("Etag")) { + return condTrue + } + im = remain + } + + return condFalse +} + +func checkIfUnmodifiedSince(r *Request, modtime time.Time) condResult { + ius := r.Header.Get("If-Unmodified-Since") + if ius == "" || isZeroTime(modtime) { + return condNone + } + t, err := ParseTime(ius) + if err != nil { + return condNone + } + + // The Last-Modified header truncates sub-second precision so + // the modtime needs to be truncated too. + modtime = modtime.Truncate(time.Second) + if ret := modtime.Compare(t); ret <= 0 { + return condTrue + } + return condFalse +} + +func checkIfNoneMatch(w ResponseWriter, r *Request) condResult { + inm := r.Header.get("If-None-Match") + if inm == "" { + return condNone + } + buf := inm + for { + buf = textproto.TrimString(buf) + if len(buf) == 0 { + break + } + if buf[0] == ',' { + buf = buf[1:] + continue + } + if buf[0] == '*' { + return condFalse + } + etag, remain := scanETag(buf) + if etag == "" { + break + } + if etagWeakMatch(etag, w.Header().get("Etag")) { + return condFalse + } + buf = remain + } + return condTrue +} + +func checkIfModifiedSince(r *Request, modtime time.Time) condResult { + if r.Method != "GET" && r.Method != "HEAD" { + return condNone + } + ims := r.Header.Get("If-Modified-Since") + if ims == "" || isZeroTime(modtime) { + return condNone + } + t, err := ParseTime(ims) + if err != nil { + return condNone + } + // The Last-Modified header truncates sub-second precision so + // the modtime needs to be truncated too. + modtime = modtime.Truncate(time.Second) + if ret := modtime.Compare(t); ret <= 0 { + return condFalse + } + return condTrue +} + +func checkIfRange(w ResponseWriter, r *Request, modtime time.Time) condResult { + if r.Method != "GET" && r.Method != "HEAD" { + return condNone + } + ir := r.Header.get("If-Range") + if ir == "" { + return condNone + } + etag, _ := scanETag(ir) + if etag != "" { + if etagStrongMatch(etag, w.Header().Get("Etag")) { + return condTrue + } else { + return condFalse + } + } + // The If-Range value is typically the ETag value, but it may also be + // the modtime date. See golang.org/issue/8367. + if modtime.IsZero() { + return condFalse + } + t, err := ParseTime(ir) + if err != nil { + return condFalse + } + if t.Unix() == modtime.Unix() { + return condTrue + } + return condFalse +} + +var unixEpochTime = time.Unix(0, 0) + +// isZeroTime reports whether t is obviously unspecified (either zero or Unix()=0). +func isZeroTime(t time.Time) bool { + return t.IsZero() || t.Equal(unixEpochTime) +} + +func setLastModified(w ResponseWriter, modtime time.Time) { + if !isZeroTime(modtime) { + w.Header().Set("Last-Modified", modtime.UTC().Format(TimeFormat)) + } +} + +func writeNotModified(w ResponseWriter) { + // RFC 7232 section 4.1: + // a sender SHOULD NOT generate representation metadata other than the + // above listed fields unless said metadata exists for the purpose of + // guiding cache updates (e.g., Last-Modified might be useful if the + // response does not have an ETag field). + h := w.Header() + delete(h, "Content-Type") + delete(h, "Content-Length") + delete(h, "Content-Encoding") + if h.Get("Etag") != "" { + delete(h, "Last-Modified") + } + w.WriteHeader(StatusNotModified) +} + +// checkPreconditions evaluates request preconditions and reports whether a precondition +// resulted in sending StatusNotModified or StatusPreconditionFailed. +func checkPreconditions(w ResponseWriter, r *Request, modtime time.Time) (done bool, rangeHeader string) { + // This function carefully follows RFC 7232 section 6. + ch := checkIfMatch(w, r) + if ch == condNone { + ch = checkIfUnmodifiedSince(r, modtime) + } + if ch == condFalse { + w.WriteHeader(StatusPreconditionFailed) + return true, "" + } + switch checkIfNoneMatch(w, r) { + case condFalse: + if r.Method == "GET" || r.Method == "HEAD" { + writeNotModified(w) + return true, "" + } else { + w.WriteHeader(StatusPreconditionFailed) + return true, "" + } + case condNone: + if checkIfModifiedSince(r, modtime) == condFalse { + writeNotModified(w) + return true, "" + } + } + + rangeHeader = r.Header.get("Range") + if rangeHeader != "" && checkIfRange(w, r, modtime) == condFalse { + rangeHeader = "" + } + return false, rangeHeader +} + +// 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, err := f.Stat() + if err != 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 + } + } + } + + if d.IsDir() { + url := r.URL.Path + // redirect if the directory name doesn't end in a slash + if url == "" || url[len(url)-1] != '/' { + localRedirect(w, r, path.Base(url)+"/") + return + } + + // use contents of index.html for directory, if present + index := strings.TrimSuffix(name, "/") + indexPage + ff, err := fs.Open(index) + if err == nil { + defer ff.Close() + dd, err := ff.Stat() + if err == nil { + d = dd + f = ff + } + } + } + + // Still a directory? (we didn't find an index.html file) + if d.IsDir() { + if checkIfModifiedSince(r, d.ModTime()) == condFalse { + writeNotModified(w) + return + } + setLastModified(w, d.ModTime()) + dirList(w, r, 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 errors.Is(err, fs.ErrNotExist) { + return "404 page not found", StatusNotFound + } + if errors.Is(err, fs.ErrPermission) { + 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. +// +// If the provided file or directory name is a relative path, it is +// interpreted relative to the current directory and may ascend to +// parent directories. If the provided name is constructed from user +// input, it should be sanitized before calling ServeFile. +// +// As a precaution, ServeFile will reject requests where r.URL.Path +// contains a ".." path element; this protects against callers who +// might unsafely use [filepath.Join] on r.URL.Path without sanitizing +// it and then use that filepath.Join result as the name argument. +// +// As another special case, ServeFile redirects any request where r.URL.Path +// ends in "/index.html" to the same path, without the final +// "index.html". To avoid such redirects either modify the path or +// use [ServeContent]. +// +// Outside of those two special cases, ServeFile does not use +// r.URL.Path for selecting the file or directory to serve; only the +// file or directory provided in the name argument is used. +func ServeFile(w ResponseWriter, r *Request, name string) { + if containsDotDot(r.URL.Path) { + // Too many programs use r.URL.Path to construct the argument to + // serveFile. Reject the request under the assumption that happened + // here and ".." may not be wanted. + // Note that name might not contain "..", for example if code (still + // incorrectly) used filepath.Join(myDir, r.URL.Path). + Error(w, "invalid URL path", StatusBadRequest) + return + } + dir, file := filepath.Split(name) + serveFile(w, r, Dir(dir), file, false) +} + +// ServeFileFS replies to the request with the contents +// of the named file or directory from the file system fsys. +// +// If the provided file or directory name is a relative path, it is +// interpreted relative to the current directory and may ascend to +// parent directories. If the provided name is constructed from user +// input, it should be sanitized before calling [ServeFile]. +// +// As a precaution, ServeFile will reject requests where r.URL.Path +// contains a ".." path element; this protects against callers who +// might unsafely use [filepath.Join] on r.URL.Path without sanitizing +// it and then use that filepath.Join result as the name argument. +// +// As another special case, ServeFile redirects any request where r.URL.Path +// ends in "/index.html" to the same path, without the final +// "index.html". To avoid such redirects either modify the path or +// use ServeContent. +// +// Outside of those two special cases, ServeFile does not use +// r.URL.Path for selecting the file or directory to serve; only the +// file or directory provided in the name argument is used. +func ServeFileFS(w ResponseWriter, r *Request, fsys fs.FS, name string) { + if containsDotDot(r.URL.Path) { + // Too many programs use r.URL.Path to construct the argument to + // serveFile. Reject the request under the assumption that happened + // here and ".." may not be wanted. + // Note that name might not contain "..", for example if code (still + // incorrectly) used filepath.Join(myDir, r.URL.Path). + Error(w, "invalid URL path", StatusBadRequest) + return + } + serveFile(w, r, FS(fsys), name, false) +} + +func containsDotDot(v string) bool { + if !strings.Contains(v, "..") { + return false + } + for _, ent := range strings.FieldsFunc(v, isSlashRune) { + if ent == ".." { + return true + } + } + return false +} + +func isSlashRune(r rune) bool { return r == '/' || r == '\\' } + +type fileHandler struct { + root FileSystem +} + +type ioFS struct { + fsys fs.FS +} + +type ioFile struct { + file fs.File +} + +func (f ioFS) Open(name string) (File, error) { + if name == "/" { + name = "." + } else { + name = strings.TrimPrefix(name, "/") + } + file, err := f.fsys.Open(name) + if err != nil { + return nil, mapOpenError(err, name, '/', func(path string) (fs.FileInfo, error) { + return fs.Stat(f.fsys, path) + }) + } + return ioFile{file}, nil +} + +func (f ioFile) Close() error { return f.file.Close() } +func (f ioFile) Read(b []byte) (int, error) { return f.file.Read(b) } +func (f ioFile) Stat() (fs.FileInfo, error) { return f.file.Stat() } + +var errMissingSeek = errors.New("io.File missing Seek method") +var errMissingReadDir = errors.New("io.File directory missing ReadDir method") + +func (f ioFile) Seek(offset int64, whence int) (int64, error) { + s, ok := f.file.(io.Seeker) + if !ok { + return 0, errMissingSeek + } + return s.Seek(offset, whence) +} + +func (f ioFile) ReadDir(count int) ([]fs.DirEntry, error) { + d, ok := f.file.(fs.ReadDirFile) + if !ok { + return nil, errMissingReadDir + } + return d.ReadDir(count) +} + +func (f ioFile) Readdir(count int) ([]fs.FileInfo, error) { + d, ok := f.file.(fs.ReadDirFile) + if !ok { + return nil, errMissingReadDir + } + var list []fs.FileInfo + for { + dirs, err := d.ReadDir(count - len(list)) + for _, dir := range dirs { + info, err := dir.Info() + if err != nil { + // Pretend it doesn't exist, like (*os.File).Readdir does. + continue + } + list = append(list, info) + } + if err != nil { + return list, err + } + if count < 0 || len(list) >= count { + break + } + } + return list, nil +} + +// FS converts fsys to a [FileSystem] implementation, +// for use with [FileServer] and [NewFileTransport]. +// The files provided by fsys must implement [io.Seeker]. +func FS(fsys fs.FS) FileSystem { + return ioFS{fsys} +} + +// FileServer returns a handler that serves HTTP requests +// with the contents of the file system rooted at root. +// +// As a special case, the returned file server redirects any request +// ending in "/index.html" to the same path, without the final +// "index.html". +// +// To use the operating system's file system implementation, +// use [http.Dir]: +// +// http.Handle("/", http.FileServer(http.Dir("/tmp"))) +// +// To use an [fs.FS] implementation, use [http.FileServerFS] instead. +func FileServer(root FileSystem) Handler { + return &fileHandler{root} +} + +// FileServerFS returns a handler that serves HTTP requests +// with the contents of the file system fsys. +// +// As a special case, the returned file server redirects any request +// ending in "/index.html" to the same path, without the final +// "index.html". +// +// http.Handle("/", http.FileServerFS(fsys)) +func FileServerFS(root fs.FS) Handler { + return FileServer(FS(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 7233. +// errNoOverlap is returned if none of the ranges overlap. +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 + noOverlap := false + for _, ra := range strings.Split(s[len(b):], ",") { + ra = textproto.TrimString(ra) + if ra == "" { + continue + } + start, end, ok := strings.Cut(ra, "-") + if !ok { + return nil, errors.New("invalid range") + } + start, end = textproto.TrimString(start), textproto.TrimString(end) + var r httpRange + if start == "" { + // If no start is specified, end specifies the + // range start relative to the end of the file, + // and we are dealing with <suffix-length> + // which has to be a non-negative integer as per + // RFC 7233 Section 2.1 "Byte-Ranges". + if end == "" || end[0] == '-' { + return nil, errors.New("invalid range") + } + i, err := strconv.ParseInt(end, 10, 64) + if i < 0 || 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 < 0 { + return nil, errors.New("invalid range") + } + if i >= size { + // If the range begins after the size of the content, + // then it does not overlap. + noOverlap = true + continue + } + 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) + } + if noOverlap && len(ranges) == 0 { + // The specified ranges did not overlap with the content. + return nil, errNoOverlap + } + 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 +} |