feat: add a config option to bypass mime content type sniffing (#60)

cmd/config.go

@@ -122,8 +122,11 @@ func parseUsers(raw []interface{}, c *lib.Config) {
 			}
 
 			user.Handler = &webdav.Handler{
-				Prefix:     c.User.Handler.Prefix,
-				FileSystem: webdav.Dir(user.Scope),
+				Prefix: c.User.Handler.Prefix,
+				FileSystem: lib.WebDavDir{
+					Dir:     webdav.Dir(user.Scope),
+					NoSniff: c.NoSniff,
+				},
 				LockSystem: webdav.NewMemLS(),
 			}
 
@@ -179,12 +182,16 @@ func readConfig(flags *pflag.FlagSet) *lib.Config {
 			Modify: getOptB(flags, "modify"),
 			Rules:  []*lib.Rule{},
 			Handler: &webdav.Handler{
-				Prefix:     getOpt(flags, "prefix"),
-				FileSystem: webdav.Dir(getOpt(flags, "scope")),
+				Prefix: getOpt(flags, "prefix"),
+				FileSystem: lib.WebDavDir{
+					Dir:     webdav.Dir(getOpt(flags, "scope")),
+					NoSniff: getOptB(flags, "nosniff"),
+				},
 				LockSystem: webdav.NewMemLS(),
 			},
 		},
-		Auth: getOptB(flags, "auth"),
+		Auth:    getOptB(flags, "auth"),
+		NoSniff: getOptB(flags, "nosniff"),
 		Cors: lib.CorsCfg{
 			Enabled:     false,
 			Credentials: false,

lib/dir.go

@@ -0,0 +1,83 @@
+package lib
+
+import (
+	"context"
+	"mime"
+	"os"
+	"path"
+
+	"golang.org/x/net/webdav"
+)
+
+// NoSniffFileInfo wraps any generic FileInfo interface and bypasses mime type sniffing.
+type NoSniffFileInfo struct {
+	os.FileInfo
+}
+
+func (w NoSniffFileInfo) ContentType(ctx context.Context) (contentType string, err error) {
+	if mimeType := mime.TypeByExtension(path.Ext(w.FileInfo.Name())); mimeType != "" {
+		// We can figure out the mime from the extension.
+		return mimeType, nil
+	} else {
+		// We can't figure out the mime type without sniffing, call it an octet stream.
+		return "application/octet-stream", nil
+	}
+}
+
+type WebDavDir struct {
+	webdav.Dir
+	NoSniff bool
+}
+
+func (d WebDavDir) Stat(ctx context.Context, name string) (os.FileInfo, error) {
+	// Skip wrapping if NoSniff is off
+	if !d.NoSniff {
+		return d.Dir.Stat(ctx, name)
+	}
+
+	info, err := d.Dir.Stat(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+
+	return NoSniffFileInfo{info}, nil
+}
+
+func (d WebDavDir) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (webdav.File, error) {
+	// Skip wrapping if NoSniff is off
+	if !d.NoSniff {
+		return d.Dir.OpenFile(ctx, name, flag, perm)
+	}
+
+	file, err := d.Dir.OpenFile(ctx, name, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+
+	return WebDavFile{File: file}, nil
+}
+
+type WebDavFile struct {
+	webdav.File
+}
+
+func (f WebDavFile) Stat() (os.FileInfo, error) {
+	info, err := f.File.Stat()
+	if err != nil {
+		return nil, err
+	}
+
+	return NoSniffFileInfo{info}, nil
+}
+
+func (f WebDavFile) Readdir(count int) (fis []os.FileInfo, err error) {
+	fis, err = f.File.Readdir(count)
+	if err != nil {
+		return nil, err
+	}
+
+	for i := range fis {
+		fis[i] = NoSniffFileInfo{fis[i]}
+	}
+	return fis, nil
+}

lib/webdav.go

@@ -20,9 +20,10 @@ type CorsCfg struct {
 // Config is the configuration of a WebDAV instance.
 type Config struct {
 	*User
-	Auth  bool
-	Cors  CorsCfg
-	Users map[string]*User
+	Auth    bool
+	NoSniff bool
+	Cors    CorsCfg
+	Users   map[string]*User
 }
 
 // ServeHTTP determines if the request is for this plugin, and if all prerequisites are met.