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