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// Copyright (c) Contributors to the Apptainer project, established as
// Apptainer a Series of LF Projects LLC.
// For website terms of use, trademark policy, privacy policy and other
// project policies see https://lfprojects.org/policies
// Copyright (c) 2018-2019, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package image
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"os"
"unsafe"
)
const (
extMagicOffset = 1080
extMagic = "\x53\xEF"
compatHasJournal = 0x4
incompatFileType = 0x2
incompatRecover = 0x4
incompatMetabg = 0x10
rocompatSparseSuper = 0x1
rocompatLargeFile = 0x2
rocompatBtreeDir = 0x4
)
const notValidExt3ImageMessage = "file is not a valid ext3 image"
var ErrNotValidExt3Image = errors.New(notValidExt3ImageMessage)
type extFSInfo struct {
Magic [2]byte
State uint16
Dummy [8]uint32
Compat uint32
Incompat uint32
Rocompat uint32
}
type ext3Format struct{}
// CheckExt3Header checks if byte content contains a valid ext3 header
// and returns offset where ext3 partition begin
func CheckExt3Header(b []byte) (uint64, error) {
var offset uint64 = extMagicOffset
o := bytes.Index(b, []byte(launchString))
if o > 0 {
offset += uint64(o + len(launchString) + 1)
}
einfo := &extFSInfo{}
if uintptr(offset)+unsafe.Sizeof(einfo) >= uintptr(len(b)) {
return offset, debugError("can't find ext3 information header")
}
buffer := bytes.NewReader(b[offset:])
if err := binary.Read(buffer, binary.LittleEndian, einfo); err != nil {
return offset, debugError("can't read the top of the image")
}
if !bytes.Equal(einfo.Magic[:], []byte(extMagic)) {
return offset, debugError(notValidExt3ImageMessage)
}
if einfo.Compat&compatHasJournal == 0 {
return offset, ErrNotValidExt3Image
}
if einfo.Incompat&^(incompatFileType|incompatRecover|incompatMetabg) != 0 {
return offset, ErrNotValidExt3Image
}
if einfo.Rocompat&^(rocompatSparseSuper|rocompatLargeFile|rocompatBtreeDir) != 0 {
return offset, ErrNotValidExt3Image
}
offset -= extMagicOffset
return offset, nil
}
func (f *ext3Format) initializer(img *Image, fileinfo os.FileInfo) error {
if fileinfo.IsDir() {
return debugError("not an ext3 image")
}
b := make([]byte, bufferSize)
if n, err := img.File.Read(b); err != nil || n != bufferSize {
return debugErrorf("can't read first %d bytes: %v", bufferSize, err)
}
offset, err := CheckExt3Header(b)
if err != nil {
return err
}
img.Type = EXT3
img.Partitions = []Section{
{
Offset: offset,
Size: uint64(fileinfo.Size()) - offset,
ID: 1,
Type: EXT3,
Name: RootFs,
AllowedUsage: RootFsUsage | OverlayUsage | DataUsage,
},
}
return nil
}
func (f *ext3Format) openMode(writable bool) int {
if writable {
return os.O_RDWR
}
return os.O_RDONLY
}
func (f *ext3Format) lock(img *Image) error {
if err := lockSection(img, img.Partitions[0]); err != nil {
return fmt.Errorf("while locking ext3 partition from %s: %s", img.Path, err)
}
return nil
}
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