File matcher enforces trailing-slash convention to match dirs/files

modules/caddyhttp/fileserver/matcher.go

@@ -19,6 +19,7 @@ import (
 	"net/http"
 	"os"
 	"path"
+	"strings"
 	"time"
 
 	"github.com/caddyserver/caddy/v2"
@@ -149,7 +150,7 @@ func (m MatchFile) selectFile(r *http.Request) (rel, abs string, matched bool) {
 		for _, f := range m.TryFiles {
 			suffix := path.Clean(repl.ReplaceAll(f, ""))
 			fullpath := sanitizedPathJoin(root, suffix)
-			if fileExists(fullpath) {
+			if strictFileExists(fullpath) {
 				return suffix, fullpath, true
 			}
 		}
@@ -207,22 +208,33 @@ func (m MatchFile) selectFile(r *http.Request) (rel, abs string, matched bool) {
 	return
 }
 
-// fileExists returns true if file exists,
+// strictFileExists returns true if file exists
-// false if it doesn't, or false if there
+// and matches the convention of the given file
-// was any other error.
+// path. If the path ends in a forward slash,
-func fileExists(file string) bool {
+// the file must also be a directory; if it does
-	_, err := os.Stat(file)
+// NOT end in a forward slash, the file must NOT
-	if err == nil {
+// be a directory.
-		return true
+func strictFileExists(file string) bool {
-	} else if os.IsNotExist(err) {
+	stat, err := os.Stat(file)
-		return false
+	if err != nil {
-	} else {
+		// in reality, this can be any error
-		// we don't know if it exists,
+		// such as permission or even obscure
-		// so assume it doesn't, since
+		// ones like "is not a directory" (when
-		// there must have been some
+		// trying to stat a file within a file);
-		// other error anyway
+		// in those cases we can't be sure if
+		// the file exists, so we just treat any
+		// error as if it does not exist; see
+		// https://stackoverflow.com/a/12518877/1048862
 		return false
 	}
+	if strings.HasSuffix(file, "/") {
+		// by convention, file paths ending
+		// in a slash must be a directory
+		return stat.IsDir()
+	}
+	// by convention, file paths NOT ending
+	// in a slash must NOT be a directory
+	return !stat.IsDir()
 }
 
 const (