WIM: Fix handling of reparse points

Reparse point data is not always in the first stream, sometimes it is in
the file data itself. Remove ReparseStream and always put it in the file
data.

wim/wim.go

@@ -153,11 +153,15 @@ const streamentrySize = 38
 // ParseError is returned when the WIM cannot be parsed.
 type ParseError struct {
 	Oper string
+	Path string
 	Err  error
 }
 
 func (e *ParseError) Error() string {
-	return "WIM parse error at " + e.Oper + ": " + e.Err.Error()
+	if e.Path == "" {
+		return "WIM parse error at " + e.Oper + ": " + e.Err.Error()
+	}
+	return fmt.Sprintf("WIM parse error: %s %s: %s", e.Oper, e.Path, e.Err.Error())
 }
 
 // Reader provides functions to read a WIM file.
@@ -205,7 +209,6 @@ type FileHeader struct {
 	LinkID             int64
 	ReparseTag         uint32
 	ReparseReserved    uint32
-	ReparseStream      *Stream
 }
 
 // File represents a file or directory in a WIM image.
@@ -227,7 +230,7 @@ func NewReader(f io.ReaderAt) (*Reader, error) {
 	}
 
 	if r.hdr.ImageTag != wimImageTag {
-		return nil, &ParseError{"image tag", errors.New("not a WIM file")}
+		return nil, &ParseError{Oper: "image tag", Err: errors.New("not a WIM file")}
 	}
 
 	if r.hdr.Flags&^supportedHdrFlags != 0 {
@@ -295,12 +298,12 @@ func (r *Reader) ReadXML() (string, error) {
 	XMLData := make([]uint16, r.hdr.XMLData.OriginalSize/2)
 	err = binary.Read(rsrc, binary.LittleEndian, XMLData)
 	if err != nil {
-		return "", &ParseError{"XML data", err}
+		return "", &ParseError{Oper: "XML data", Err: err}
 	}
 
 	// The BOM will always indicate little-endian UTF-16.
 	if XMLData[0] != 0xfeff {
-		return "", &ParseError{"XML data", errors.New("invalid BOM")}
+		return "", &ParseError{Oper: "XML data", Err: errors.New("invalid BOM")}
 	}
 	return string(utf16.Decode(XMLData[1:])), nil
 }
@@ -311,39 +314,39 @@ func (r *Reader) readOffsetTable(res *resourceDescriptor) (map[SHA1Hash]resource
 
 	offsetTable, err := r.readResource(res)
 	if err != nil {
-		return nil, nil, &ParseError{"offset table", err}
+		return nil, nil, &ParseError{Oper: "offset table", Err: err}
 	}
 
 	br := bytes.NewReader(offsetTable)
-	for {
+	for i := 0; ; i++ {
 		var res streamDescriptor
 		err := binary.Read(br, binary.LittleEndian, &res)
 		if err == io.EOF {
 			break
 		}
 		if err != nil {
-			return nil, nil, &ParseError{"offset table", err}
+			return nil, nil, &ParseError{Oper: "offset table", Err: err}
 		}
 		if res.Flags()&^supportedResFlags != 0 {
-			return nil, nil, &ParseError{"offset table", errors.New("unsupported resource flag")}
+			return nil, nil, &ParseError{Oper: "offset table", Err: errors.New("unsupported resource flag")}
 		}
 
 		// Validation for ad-hoc testing
 		if validate {
 			sec, err := r.resourceReader(&res.resourceDescriptor)
 			if err != nil {
-				return nil, nil, err
+				panic(fmt.Sprint(i, err))
 			}
 			hash := sha1.New()
 			_, err = io.Copy(hash, sec)
 			sec.Close()
 			if err != nil {
-				return nil, nil, err
+				panic(fmt.Sprint(i, err))
 			}
 			var cmphash SHA1Hash
 			copy(cmphash[:], hash.Sum(nil))
 			if cmphash != res.Hash {
-				return nil, nil, errors.New("hash mismatch")
+				panic(fmt.Sprint(i, "hash mismatch"))
 			}
 		}
 
@@ -359,7 +362,7 @@ func (r *Reader) readOffsetTable(res *resourceDescriptor) (map[SHA1Hash]resource
 	}
 
 	if len(images) != int(r.hdr.ImageCount) {
-		return nil, nil, &ParseError{"offset table", errors.New("mismatched image count")}
+		return nil, nil, &ParseError{Oper: "offset table", Err: errors.New("mismatched image count")}
 	}
 
 	return fileData, images, nil
@@ -369,7 +372,7 @@ func (r *Reader) readSecurityDescriptors(rsrc io.Reader) (sds [][]byte, n int64,
 	var secBlock securityblockDisk
 	err = binary.Read(rsrc, binary.LittleEndian, &secBlock)
 	if err != nil {
-		err = &ParseError{"security table", err}
+		err = &ParseError{Oper: "security table", Err: err}
 		return
 	}
 
@@ -378,7 +381,7 @@ func (r *Reader) readSecurityDescriptors(rsrc io.Reader) (sds [][]byte, n int64,
 	secSizes := make([]int64, secBlock.NumEntries)
 	err = binary.Read(rsrc, binary.LittleEndian, &secSizes)
 	if err != nil {
-		err = &ParseError{"security table sizes", err}
+		err = &ParseError{Oper: "security table sizes", Err: err}
 		return
 	}
 
@@ -389,7 +392,7 @@ func (r *Reader) readSecurityDescriptors(rsrc io.Reader) (sds [][]byte, n int64,
 		sd := make([]byte, size&0xffffffff)
 		_, err = io.ReadFull(rsrc, sd)
 		if err != nil {
-			err = &ParseError{"security descriptor", err}
+			err = &ParseError{Oper: "security descriptor", Err: err}
 			return
 		}
 		n += int64(len(sd))
@@ -398,7 +401,7 @@ func (r *Reader) readSecurityDescriptors(rsrc io.Reader) (sds [][]byte, n int64,
 
 	secsize := int64((secBlock.TotalLength + 7) &^ 7)
 	if n > secsize {
-		err = &ParseError{"security descriptor", errors.New("security descriptor table too small")}
+		err = &ParseError{Oper: "security descriptor", Err: errors.New("security descriptor table too small")}
 		return
 	}
 
@@ -432,7 +435,7 @@ func (img *Image) Open() (*File, error) {
 		return nil, err
 	}
 	if len(f) != 1 {
-		return nil, &ParseError{"root directory", errors.New("expected exactly 1 root directory entry")}
+		return nil, &ParseError{Oper: "root directory", Err: errors.New("expected exactly 1 root directory entry")}
 	}
 	return f[0], err
 }
@@ -457,7 +460,7 @@ func (img *Image) readdir(rsrc io.Reader) ([]*File, error) {
 func (img *Image) readNextEntry(r *bufio.Reader) (*File, error) {
 	lengthBuf, err := r.Peek(8)
 	if err != nil {
-		return nil, &ParseError{"directory length check", err}
+		return nil, &ParseError{Oper: "directory length check", Err: err}
 	}
 
 	left := int(binary.LittleEndian.Uint64(lengthBuf))
@@ -466,24 +469,46 @@ func (img *Image) readNextEntry(r *bufio.Reader) (*File, error) {
 	}
 
 	if left < direntrySize {
-		return nil, &ParseError{"directory entry", errors.New("size too short")}
+		return nil, &ParseError{Oper: "directory entry", Err: errors.New("size too short")}
 	}
 
 	var dentry direntry
 	err = binary.Read(r, binary.LittleEndian, &dentry)
 	if err != nil {
-		return nil, &ParseError{"directory entry", err}
+		return nil, &ParseError{Oper: "directory entry", Err: err}
 	}
 
 	left -= direntrySize
 
+	namesLen := int(dentry.FileNameLength + 2 + dentry.ShortNameLength)
+	if left < namesLen {
+		return nil, &ParseError{Oper: "directory entry", Err: errors.New("size too short for names")}
+	}
+
+	names := make([]uint16, namesLen/2)
+	err = binary.Read(r, binary.LittleEndian, names)
+	if err != nil {
+		return nil, &ParseError{Oper: "file name", Err: err}
+	}
+
+	left -= namesLen
+
+	var name, shortName string
+	if dentry.FileNameLength > 0 {
+		name = string(utf16.Decode(names[:dentry.FileNameLength/2]))
+	}
+
+	if dentry.ShortNameLength > 0 {
+		shortName = string(utf16.Decode(names[dentry.FileNameLength/2+1:]))
+	}
+
 	var offset resourceDescriptor
 	zerohash := SHA1Hash{}
 	if dentry.Hash != zerohash {
 		var ok bool
 		offset, ok = img.wim.fileData[dentry.Hash]
 		if !ok {
-			return nil, &ParseError{"directory entry", fmt.Errorf("could not find file data matching hash %v", dentry.Hash)}
+			return nil, &ParseError{Oper: "directory entry", Path: name, Err: fmt.Errorf("could not find file data matching hash %#v", dentry)}
 		}
 	}
 
@@ -495,6 +520,8 @@ func (img *Image) readNextEntry(r *bufio.Reader) (*File, error) {
 			LastWriteTime:  dentry.LastWriteTime,
 			Hash:           dentry.Hash,
 			Size:           offset.OriginalSize,
+			Name:           name,
+			ShortName:      shortName,
 		},
 
 		offset:       offset,
@@ -502,38 +529,28 @@ func (img *Image) readNextEntry(r *bufio.Reader) (*File, error) {
 		subdirOffset: dentry.SubdirOffset,
 	}
 
+	isDir := false
+
 	if dentry.Attributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT == 0 {
 		f.LinkID = dentry.ReparseHardLink
+		if dentry.Attributes&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
+			isDir = true
+		}
 	} else {
 		f.ReparseTag = uint32(dentry.ReparseHardLink)
 		f.ReparseReserved = uint32(dentry.ReparseHardLink >> 32)
 	}
 
+	if isDir && f.subdirOffset == 0 {
+		return nil, &ParseError{Oper: "directory entry", Path: name, Err: errors.New("no subdirectory data for directory")}
+	} else if !isDir && f.subdirOffset != 0 {
+		return nil, &ParseError{Oper: "directory entry", Path: name, Err: errors.New("unexpected subdirectory data for non-directory")}
+	}
+
 	if dentry.SecurityID != 0xffffffff {
 		f.SecurityDescriptor = img.sds[dentry.SecurityID]
 	}
 
-	namesLen := int(dentry.FileNameLength + 2 + dentry.ShortNameLength)
-	if left < namesLen {
-		return nil, &ParseError{"directory entry", errors.New("size too short for names")}
-	}
-
-	names := make([]uint16, namesLen/2)
-	err = binary.Read(r, binary.LittleEndian, names)
-	if err != nil {
-		return nil, &ParseError{"file name", err}
-	}
-
-	left -= namesLen
-
-	if dentry.FileNameLength > 0 {
-		f.Name = string(utf16.Decode(names[:dentry.FileNameLength/2]))
-	}
-
-	if dentry.ShortNameLength > 0 {
-		f.ShortName = string(utf16.Decode(names[dentry.FileNameLength/2+1:]))
-	}
-
 	_, err = r.Discard(left)
 	if err != nil {
 		return nil, err
@@ -546,19 +563,20 @@ func (img *Image) readNextEntry(r *bufio.Reader) (*File, error) {
 			if err != nil {
 				return nil, err
 			}
-			if !(s.Name == "" && s.Size == 0) {
+			// The first unnamed stream should be treated as the file stream.
-				if dentry.Attributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 && s.Name == "" {
+			if i == 0 && s.Name == "" {
-					f.ReparseStream = s
+				f.Hash = s.Hash
-				} else {
+				f.Size = s.Size
-					streams = append(streams, s)
+				f.offset = s.offset
-				}
+			} else if s.Name != "" {
+				streams = append(streams, s)
 			}
 		}
 		f.Streams = streams
 	}
 
-	if dentry.Attributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 && f.ReparseStream == nil {
+	if dentry.Attributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 && f.Size == 0 {
-		return nil, &ParseError{"directory entry", errors.New("reparse point is missing reparse stream")}
+		return nil, &ParseError{Oper: "directory entry", Path: name, Err: errors.New("reparse point is missing reparse stream")}
 	}
 
 	return f, nil
@@ -567,28 +585,41 @@ func (img *Image) readNextEntry(r *bufio.Reader) (*File, error) {
 func (img *Image) readNextStream(r *bufio.Reader) (*Stream, error) {
 	lengthBuf, err := r.Peek(8)
 	if err != nil {
-		return nil, &ParseError{"stream length check", err}
+		return nil, &ParseError{Oper: "stream length check", Err: err}
 	}
 
 	left := int(binary.LittleEndian.Uint64(lengthBuf))
 	if left < streamentrySize {
-		return nil, &ParseError{"stream entry", errors.New("size too short")}
+		return nil, &ParseError{Oper: "stream entry", Err: errors.New("size too short")}
 	}
 
 	var sentry streamentry
 	err = binary.Read(r, binary.LittleEndian, &sentry)
 	if err != nil {
-		return nil, &ParseError{"stream entry", err}
+		return nil, &ParseError{Oper: "stream entry", Err: err}
 	}
 
 	left -= streamentrySize
 
+	if left < int(sentry.NameLength) {
+		return nil, &ParseError{Oper: "stream entry", Err: errors.New("size too short for name")}
+	}
+
+	names := make([]uint16, sentry.NameLength/2)
+	err = binary.Read(r, binary.LittleEndian, names)
+	if err != nil {
+		return nil, &ParseError{Oper: "file name", Err: err}
+	}
+
+	left -= int(sentry.NameLength)
+	name := string(utf16.Decode(names))
+
 	var offset resourceDescriptor
 	if sentry.Hash != (SHA1Hash{}) {
 		var ok bool
 		offset, ok = img.wim.fileData[sentry.Hash]
 		if !ok {
-			return nil, &ParseError{"stream entry", fmt.Errorf("could not find file data matching hash %v", sentry.Hash)}
+			return nil, &ParseError{Oper: "stream entry", Path: name, Err: fmt.Errorf("could not find file data matching hash %v", sentry.Hash)}
 		}
 	}
 
@@ -596,24 +627,12 @@ func (img *Image) readNextStream(r *bufio.Reader) (*Stream, error) {
 		StreamHeader: StreamHeader{
 			Hash: sentry.Hash,
 			Size: offset.OriginalSize,
+			Name: name,
 		},
 		wim:    img.wim,
 		offset: offset,
 	}
 
-	if left < int(sentry.NameLength) {
-		return nil, &ParseError{"stream entry", errors.New("size too short for name")}
-	}
-
-	names := make([]uint16, sentry.NameLength/2)
-	err = binary.Read(r, binary.LittleEndian, names)
-	if err != nil {
-		return nil, &ParseError{"file name", err}
-	}
-
-	left -= int(sentry.NameLength)
-	s.Name = string(utf16.Decode(names))
-
 	_, err = r.Discard(left)
 	if err != nil {
 		return nil, err
@@ -634,7 +653,7 @@ func (f *File) Open() (io.ReadCloser, error) {
 
 // Readdir reads the directory entries.
 func (f *File) Readdir() ([]*File, error) {
-	if f.Attributes&syscall.FILE_ATTRIBUTE_DIRECTORY == 0 {
+	if !f.IsDir() {
 		return nil, errors.New("not a directory")
 	}
 	rsrc, err := f.img.wim.resourceReaderWithOffset(&f.img.offset, f.subdirOffset)
@@ -644,3 +663,9 @@ func (f *File) Readdir() ([]*File, error) {
 	defer rsrc.Close()
 	return f.img.readdir(rsrc)
 }
+
+// IsDir returns whether the given file is a directory. It returns false when it
+// is a directory reparse point.
+func (f *FileHeader) IsDir() bool {
+	return f.Attributes&(syscall.FILE_ATTRIBUTE_DIRECTORY|syscall.FILE_ATTRIBUTE_REPARSE_POINT) == syscall.FILE_ATTRIBUTE_DIRECTORY
+}