plan 8: trash refuses unsafe entry names and relative paths

1 files changed, 16 insertions, 3 deletions

diff --git a/internal/trash/trash.go b/internal/trash/trash.go
index cc9bc23..b96c3aa 100644
--- a/internal/trash/trash.go
+++ b/internal/trash/trash.go
@@ -174,7 +174,9 @@ func percentDecode(s string) string {
 }
 
 // Restore moves an entry back to the Path recorded in its .trashinfo and
-// removes the .trashinfo. It refuses when that path already exists.
+// removes the .trashinfo. It refuses when that path already exists. It also
+// refuses an entry that is not a plain name inside the Trash, and a
+// trashinfo whose Path is not absolute.
 //
 // Once the rename back to the original path has succeeded, removing the
 // .trashinfo is best-effort: that file back in place is the substantive
@@ -183,6 +185,11 @@ func percentDecode(s string) string {
 // as an error — Restore returns (path, nil) regardless — and the
 // .trashinfo may survive as a stale, otherwise-harmless record.
 func Restore(entry string) (restored string, err error) {
+	// An entry comes from the log; it must name something inside the Trash
+	// (spec §15.1), never a path that climbs out of it.
+	if entry == "" || entry == "." || entry == ".." || strings.ContainsRune(entry, '/') {
+		return "", fmt.Errorf("trash: bad entry name %q", entry)
+	}
 	infoPath := filepath.Join(infoDir(), entry+".trashinfo")
 	b, err := os.ReadFile(infoPath)
 	if err != nil {
@@ -211,11 +218,17 @@ func Restore(entry string) (restored string, err error) {
 	return path, nil
 }
 
-// parsePath extracts and decodes the Path= line of a .trashinfo file.
+// parsePath extracts and decodes the Path= line of a .trashinfo file. The
+// path must be absolute: Restore must never resolve one against the
+// working directory.
 func parsePath(info string) (string, error) {
 	for _, line := range strings.Split(info, "\n") {
 		if v, ok := strings.CutPrefix(line, "Path="); ok {
-			return percentDecode(v), nil
+			p := percentDecode(v)
+			if !filepath.IsAbs(p) {
+				return "", fmt.Errorf("trashinfo path %q is not absolute", p)
+			}
+			return p, nil
 		}
 	}
 	return "", errors.New("trashinfo has no path")