fix: allow mapfs to open dirs (#3867)

pkg/mapfs/file.go

@@ -36,8 +36,7 @@ func (f *file) Open(name string) (fs.File, error) {
 		return f.open()
 	}
 
-	// TODO: support directory
-	if sub, err := f.getFile(name); err == nil && !sub.stat.IsDir() {
+	if sub, err := f.getFile(name); err == nil {
 		return sub.open()
 	}
 
@@ -49,16 +48,26 @@ func (f *file) Open(name string) (fs.File, error) {
 }
 
 func (f *file) open() (fs.File, error) {
-	// virtual file
-	if len(f.data) != 0 {
+	switch {
+	case f.stat.IsDir(): // Directory
+		entries, err := f.ReadDir(".")
+		if err != nil {
+			return nil, xerrors.Errorf("read dir error: %w", err)
+		}
+		return &mapDir{
+			path:     f.path,
+			fileStat: f.stat,
+			entry:    entries,
+		}, nil
+	case len(f.data) != 0: // Virtual file
 		return &openMapFile{
 			path:   f.stat.name,
 			file:   f,
 			offset: 0,
 		}, nil
+	default: // Real file
+		return os.Open(f.path)
 	}
-	// real file
-	return os.Open(f.path)
 }
 
 func (f *file) Remove(name string) error {
@@ -213,6 +222,9 @@ func (f *file) WriteFile(path, underlyingPath string) error {
 }
 
 func (f *file) WriteVirtualFile(path string, data []byte, mode fs.FileMode) error {
+	if mode&fs.ModeDir != 0 {
+		return xerrors.Errorf("invalid perm: %v", mode)
+	}
 	parts := strings.Split(path, separator)
 
 	if len(parts) == 1 {
@@ -287,7 +299,11 @@ func (f *openMapFile) Read(b []byte) (int, error) {
 		return 0, io.EOF
 	}
 	if f.offset < 0 {
-		return 0, &fs.PathError{Op: "read", Path: f.path, Err: fs.ErrInvalid}
+		return 0, &fs.PathError{
+			Op:   "read",
+			Path: f.path,
+			Err:  fs.ErrInvalid,
+		}
 	}
 	n := copy(b, f.file.data[f.offset:])
 	f.offset += int64(n)
@@ -304,19 +320,61 @@ func (f *openMapFile) Seek(offset int64, whence int) (int64, error) {
 		offset += int64(len(f.file.data))
 	}
 	if offset < 0 || offset > int64(len(f.file.data)) {
-		return 0, &fs.PathError{Op: "seek", Path: f.path, Err: fs.ErrInvalid}
+		return 0, &fs.PathError{
+			Op:   "seek",
+			Path: f.path,
+			Err:  fs.ErrInvalid,
+		}
 	}
 	f.offset = offset
 	return offset, nil
 }
 
 func (f *openMapFile) ReadAt(b []byte, offset int64) (int, error) {
 	if offset < 0 || offset > int64(len(f.file.data)) {
-		return 0, &fs.PathError{Op: "read", Path: f.path, Err: fs.ErrInvalid}
+		return 0, &fs.PathError{
+			Op:   "read",
+			Path: f.path,
+			Err:  fs.ErrInvalid,
+		}
 	}
 	n := copy(b, f.file.data[offset:])
 	if n < len(b) {
 		return n, io.EOF
 	}
 	return n, nil
 }
+
+// A mapDir is a directory fs.File (so also an fs.ReadDirFile) open for reading.
+type mapDir struct {
+	path string
+	fileStat
+	entry  []fs.DirEntry
+	offset int
+}
+
+func (d *mapDir) Stat() (fs.FileInfo, error) { return &d.fileStat, nil }
+func (d *mapDir) Close() error               { return nil }
+func (d *mapDir) Read(_ []byte) (int, error) {
+	return 0, &fs.PathError{
+		Op:   "read",
+		Path: d.path,
+		Err:  fs.ErrInvalid,
+	}
+}
+
+func (d *mapDir) ReadDir(count int) ([]fs.DirEntry, error) {
+	n := len(d.entry) - d.offset
+	if n == 0 && count > 0 {
+		return nil, io.EOF
+	}
+	if count > 0 && n > count {
+		n = count
+	}
+	list := make([]fs.DirEntry, n)
+	for i := range list {
+		list[i] = d.entry[d.offset+i]
+	}
+	d.offset += n
+	return list, nil
+}

pkg/mapfs/fs.go

@@ -5,6 +5,7 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"golang.org/x/exp/slices"
@@ -188,5 +189,6 @@ func (m *FS) RemoveAll(path string) error {
 func cleanPath(path string) string {
 	path = filepath.Clean(path)
 	path = filepath.ToSlash(path)
+	path = strings.TrimLeft(path, "/") // Remove the leading slash
 	return path
 }

pkg/mapfs/fs_test.go

@@ -281,7 +281,10 @@ func TestFS_Open(t *testing.T) {
 		{
 			name:     "dir",
 			filePath: "a/b/c",
-			wantErr:  assert.Error,
+			want: file{
+				fileInfo: cdirFileInfo,
+			},
+			wantErr: assert.NoError,
 		},
 		{
 			name:     "no such file",
@@ -306,9 +309,11 @@ func TestFS_Open(t *testing.T) {
 			require.NoError(t, err)
 			assertFileInfo(t, tt.want.fileInfo, fi)
 
-			b, err := io.ReadAll(f)
-			require.NoError(t, err)
-			assert.Equal(t, tt.want.body, string(b))
+			if tt.want.body != "" {
+				b, err := io.ReadAll(f)
+				require.NoError(t, err)
+				assert.Equal(t, tt.want.body, string(b))
+			}
 		})
 	}
 }

pkg/module/memfs.go

@@ -8,13 +8,13 @@ import (
 	"golang.org/x/xerrors"
 
 	dio "github.com/aquasecurity/go-dep-parser/pkg/io"
-	"github.com/aquasecurity/memoryfs"
+	"github.com/aquasecurity/trivy/pkg/mapfs"
 )
 
-// memFS is a wrapper of memoryfs.FS and can change its underlying file system
+// memFS is a wrapper of mapfs.FS and can change its underlying file system
 // at runtime. This implements fs.FS.
 type memFS struct {
-	current *memoryfs.FS
+	current *mapfs.FS
 }
 
 // Open implements fs.FS.
@@ -29,18 +29,20 @@ func (m *memFS) Open(name string) (fs.File, error) {
 //
 // Note: it is always to safe swap the underlying FS with this API since this is called only at the beginning of
 // Analyze interface call, which is not concurrently called per module instance.
-func (m *memFS) initialize(filePath string, content dio.ReadSeekerAt) (err error) {
-	memfs := memoryfs.New()
-	if err = memfs.MkdirAll(filepath.Dir(filePath), fs.ModePerm); err != nil {
-		return xerrors.Errorf("memory fs mkdir error: %w", err)
+func (m *memFS) initialize(filePath string, content dio.ReadSeekerAt) error {
+	mfs := mapfs.New()
+	if err := mfs.MkdirAll(filepath.Dir(filePath), fs.ModePerm); err != nil {
+		return xerrors.Errorf("mapfs mkdir error: %w", err)
 	}
-	err = memfs.WriteLazyFile(filePath, func() (io.Reader, error) {
-		return content, nil
-	}, fs.ModePerm)
+	b, err := io.ReadAll(content)
 	if err != nil {
-		return xerrors.Errorf("memory fs write error: %w", err)
+		return xerrors.Errorf("read error: %w", err)
+	}
+	err = mfs.WriteVirtualFile(filePath, b, fs.ModePerm)
+	if err != nil {
+		return xerrors.Errorf("mapfs write error: %w", err)
 	}
 
-	m.current = memfs
-	return
+	m.current = mfs
+	return nil
 }