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package contentenc
// Per-file header
//
// Format: [ "Version" uint16 big endian ] [ "Id" 16 random bytes ]
import (
"bytes"
"encoding/binary"
"log"
"syscall"
"github.com/rfjakob/gocryptfs/internal/cryptocore"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
// CurrentVersion is the current On-Disk-Format version
CurrentVersion = 2
headerVersionLen = 2 // uint16
headerIDLen = 16 // 128 bit random file id
// HeaderLen is the total header length
HeaderLen = headerVersionLen + headerIDLen
)
// FileHeader represents the header stored on each non-empty file.
type FileHeader struct {
Version uint16
ID []byte
}
// Pack - serialize fileHeader object
func (h *FileHeader) Pack() []byte {
if len(h.ID) != headerIDLen || h.Version != CurrentVersion {
log.Panic("FileHeader object not properly initialized")
}
buf := make([]byte, HeaderLen)
binary.BigEndian.PutUint16(buf[0:headerVersionLen], h.Version)
copy(buf[headerVersionLen:], h.ID)
return buf
}
// allZeroFileID is preallocated to quickly check if the data read from disk is all zero
var allZeroFileID = make([]byte, headerIDLen)
// ParseHeader - parse "buf" into fileHeader object
func ParseHeader(buf []byte) (*FileHeader, error) {
if len(buf) != HeaderLen {
tlog.Warn.Printf("ParseHeader: invalid length: want %d bytes, got %d. Returning EINVAL.", HeaderLen, len(buf))
return nil, syscall.EINVAL
}
var h FileHeader
h.Version = binary.BigEndian.Uint16(buf[0:headerVersionLen])
if h.Version != CurrentVersion {
tlog.Warn.Printf("ParseHeader: invalid version: want %d, got %d. Returning EINVAL.", CurrentVersion, h.Version)
return nil, syscall.EINVAL
}
h.ID = buf[headerVersionLen:]
if bytes.Equal(h.ID, allZeroFileID) {
tlog.Warn.Printf("ParseHeader: file id is all-zero. Returning EINVAL.")
return nil, syscall.EINVAL
}
return &h, nil
}
// RandomHeader - create new fileHeader object with random Id
func RandomHeader() *FileHeader {
var h FileHeader
h.Version = CurrentVersion
h.ID = cryptocore.RandBytes(headerIDLen)
return &h
}
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