lib/fs: Don't add path separators at end of path (fixes #5144) (#5146)

lib/fs/basicfs.go

@@ -57,10 +57,6 @@ func newBasicFilesystem(root string) *BasicFilesystem {
 	// have an absolute path here if the previous steps failed.
 	if runtime.GOOS == "windows" {
 		root = longFilenameSupport(root)
-	} else if !strings.HasSuffix(root, sep) {
-		// If we're not on Windows, we want the path to end with a slash to
-		// penetrate symlinks. On Windows, paths must not end with a slash.
-		root = root + sep
 	}
 
 	return &BasicFilesystem{root}
@@ -80,33 +76,14 @@ func rooted(rel, root string) (string, error) {
 		return "", ErrInvalidFilename
 	}
 
-	pathSep := string(PathSeparator)
-
-	// The expected prefix for the resulting path is the root, with a path
-	// separator at the end.
-	expectedPrefix := filepath.FromSlash(root)
-	if !strings.HasSuffix(expectedPrefix, pathSep) {
-		expectedPrefix += pathSep
-	}
-
 	var err error
+	// Takes care that rel does not try to escape
 	rel, err = Canonicalize(rel)
 	if err != nil {
 		return "", err
 	}
 
-	// The supposedly correct path is the one filepath.Join will return, as
-	// it does cleaning and so on. Check that one first to make sure no
-	// obvious escape attempts have been made.
-	joined := filepath.Join(root, rel)
-	if rel == "." && !strings.HasSuffix(joined, pathSep) {
-		joined += pathSep
-	}
-	if !strings.HasPrefix(joined, expectedPrefix) {
-		return "", ErrNotRelative
-	}
-
-	return joined, nil
+	return filepath.Join(root, rel), nil
 }
 
 func (f *BasicFilesystem) unrooted(path string) string {

lib/fs/basicfs_test.go

@@ -332,10 +332,14 @@ func TestRooted(t *testing.T) {
 		{"baz/foo/", "/bar/baz", "baz/foo/bar/baz", true},
 
 		// Not escape attempts, but oddly formatted relative paths.
-		{"foo", "", "foo/", true},
-		{"foo", "/", "foo/", true},
-		{"foo", "/..", "foo/", true},
+		{"foo", "", "foo", true},
+		{"foo", "/", "foo", true},
+		{"foo", "/..", "foo", true},
 		{"foo", "./bar", "foo/bar", true},
+		{"foo/", "", "foo", true},
+		{"foo/", "/", "foo", true},
+		{"foo/", "/..", "foo", true},
+		{"foo/", "./bar", "foo/bar", true},
 		{"baz/foo", "./bar", "baz/foo/bar", true},
 		{"foo", "./bar/baz", "foo/bar/baz", true},
 		{"baz/foo", "./bar/baz", "baz/foo/bar/baz", true},
@@ -396,6 +400,10 @@ func TestRooted(t *testing.T) {
 			{`\\?\c:\`, `\\foo`, ``, false},
 			{`\\?\c:\`, ``, `\\?\c:\`, true},
 			{`\\?\c:\`, `\`, `\\?\c:\`, true},
+			{`\\?\c:\test`, `.`, `\\?\c:\test`, true},
+			{`c:\test`, `.`, `c:\test`, true},
+			{`\\?\c:\test`, `/`, `\\?\c:\test`, true},
+			{`c:\test`, ``, `c:\test`, true},
 
 			// makes no sense, but will be treated simply as a bad filename
 			{`c:\foo`, `d:\bar`, `c:\foo\d:\bar`, true},
@@ -461,8 +469,8 @@ func TestNewBasicFilesystem(t *testing.T) {
 		expectedRoot string
 		expectedURI  string
 	}{
-		{"/foo/bar/baz", "/foo/bar/baz/", "/foo/bar/baz/"},
-		{"/foo/bar/baz/", "/foo/bar/baz/", "/foo/bar/baz/"},
+		{"/foo/bar/baz", "/foo/bar/baz", "/foo/bar/baz"},
+		{"/foo/bar/baz/", "/foo/bar/baz", "/foo/bar/baz"},
 		{"", "/", "/"},
 		{"/", "/", "/"},
 	}