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header.go
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header.go
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package bacc
import (
"crypto/rsa"
"os"
"crypto/sha256"
"fmt"
"strings"
"bytes"
"github.com/go-errors/errors"
)
const (
checksumOffset = 0x04
signatureOffsetOffset = 0x28
certificateFingerprintOffset = 0x31
)
type archiveHeaderWriter struct {
magicHeader uint16
version uint8
bitflag uint8
checksum [32]byte
headerSize uint32
signatureOffset uint64
signatureMethod SignatureMethod
certificateFingerprint string
metadataSize uint32
metadata []byte
}
func createHeader(archive *JsonArchive, addressingMode AddressingMode,
metadata map[string]interface{}) (*archiveHeaderWriter, error) {
var metadataData []byte = nil
if metadata != nil && len(metadata) > 0 {
md, err := serialize(metadata)
if err != nil {
return nil, err
}
metadataData = md
}
bitflag := uint8(0)
if addressingMode == ADDRESSING_64BIT {
bitflag |= 1 << 7
}
return &archiveHeaderWriter{
magicHeader: MagicHeader,
version: 0x01,
bitflag: bitflag,
signatureMethod: archive.signatureConfig.signatureMethod,
certificateFingerprint: archive.signatureConfig.signatureCertificate,
metadataSize: uint32(len(metadataData)),
metadata: metadataData,
headerSize: BaseBytesizeArchiveHeader + uint32(len(metadataData)),
}, nil
}
func (ahw *archiveHeaderWriter) calculateChecksumOffset() int64 {
return checksumOffset
}
func (ahw *archiveHeaderWriter) calculateSignatureOffsetOffset() int64 {
return signatureOffsetOffset
}
func (ahw *archiveHeaderWriter) calculateCertificateFingerprintOffset() int64 {
return certificateFingerprintOffset
}
func (ahw *archiveHeaderWriter) write(writer *writeBuffer) error {
writer.mark()
if _, err := writer.writeUint16(ahw.magicHeader); err != nil {
return err
}
if _, err := writer.writeUint8(ahw.version); err != nil {
return err
}
if _, err := writer.writeUint8(ahw.bitflag); err != nil {
return err
}
writer.skip(32) // checksum will be added later in the creation process
if _, err := writer.writeUint32(ahw.headerSize); err != nil {
return err
}
if _, err := writer.writeUint64(ahw.signatureOffset); err != nil {
return err
}
if _, err := writer.writeUint8(uint8(ahw.signatureMethod)); err != nil {
return err
}
writer.skip(32) // signature fingerprint
if _, err := writer.writeUint24(ahw.metadataSize); err != nil {
return err
}
if ahw.metadataSize > 0 {
if _, err := writer.Write(ahw.metadata); err != nil {
return err
}
}
if int64(ahw.headerSize) != writer.writtenSinceMarker() {
panic("Wrong header size on header?")
}
return nil
}
type archiveHeader struct {
magicHeader uint16
version uint8
bitflag uint8
checksum [32]byte
headerSize uint32
signatureOffset uint64
signatureMethod SignatureMethod
certificateFingerprint string
metadata map[string]interface{}
}
func (header *archiveHeader) MagicHeader() uint16 {
return header.magicHeader
}
func (header *archiveHeader) Version() uint8 {
return header.version
}
func (header *archiveHeader) Bitflag() uint8 {
return header.bitflag
}
func (header *archiveHeader) Checksum() [32]byte {
return header.checksum
}
func (header *archiveHeader) HeaderSize() uint32 {
return header.headerSize
}
func (header *archiveHeader) SignatureOffset() uint64 {
return header.signatureOffset
}
func (header *archiveHeader) SignatureMethod() SignatureMethod {
return header.signatureMethod
}
func (header *archiveHeader) CertificateFingerprint() string {
return header.certificateFingerprint
}
func (header *archiveHeader) Metadata() map[string]interface{} {
return header.metadata
}
func (header *archiveHeader) Verify(allowUnsigned bool) (bool, error) {
// TODO implement verification
return true, nil
}
func (header *archiveHeader) AddressingMode() AddressingMode {
return AddressingMode((header.bitflag >> 7) & 1)
}
type readerArchive struct {
header ArchiveHeader
rootEntry ArchiveFolder
reader *readerBuffer
archivePath string
}
func (a *readerArchive) Close() error {
return a.reader.file.Close()
}
func (a *readerArchive) Header() ArchiveHeader {
return a.header
}
func (a *readerArchive) RootEntry() ArchiveFolder {
return a.rootEntry
}
func (a *readerArchive) ListLookupDirectory() {
a.printEntry(a.rootEntry, 0, false)
}
func (a *readerArchive) Verify(allowUnsigned bool) (bool, error) {
success, err := a.checkFingerprint()
if err != nil {
return false, err
}
if !success {
return success, nil
}
if a.header.SignatureMethod() == SIGMET_UNSINGED && !allowUnsigned {
return false, errors.New("unsigned archives are not allowed")
}
return a.checkSignature()
}
func (a *readerArchive) printEntry(entry ArchiveEntry, indentation int, lastItem bool) {
for i := 0; i < indentation; i++ {
fmt.Print("│ ")
}
switch e := entry.(type) {
case ArchiveFolder:
fmt.Println("├ " + entry.Name())
case ArchiveFile:
var compressionRatio = float64(100)
if e.UncompressedSize() > 0 {
compressionRatio = float64(e.CompressedSize()) * 100.0 / float64(e.UncompressedSize())
}
if !lastItem {
fmt.Print("├ ")
} else {
fmt.Print("└ ")
}
fmt.Println(fmt.Sprintf("%s [%s, %s, %d] %.2f %%, metadata: %s",
strings.Replace(e.Name(), "\r", "", -1), e.CompressionMethod().String(),
e.EncryptionMethod().String(), e.ContentOffset(), compressionRatio, e.Metadata()))
}
switch e := entry.(type) {
case ArchiveFolder:
for i, child := range e.Entries() {
a.printEntry(child, indentation+1, uint32(i) == e.EntryCount()-1)
}
}
}
func (a *readerArchive) checkSignature() (bool, error) {
key, err := LoadKeyForVerifying("test/public.pem")
if err != nil {
return false, err
}
file, err := os.Open(a.archivePath)
if err != nil {
return false, err
}
signatureOffset := int64(a.header.SignatureOffset())
signature := make([]byte, 256)
_, err = file.ReadAt(signature, signatureOffset)
if err != nil {
return false, err
}
reader := newBoundedReader(file, 0, signatureOffset)
err = key.Verify(reader, signatureOffset, signature, func(total uint64, processed uint64, progress float32) {
})
if err != nil && err != rsa.ErrVerification {
return false, err
}
return err == nil, nil
}
func (a *readerArchive) checkFingerprint() (bool, error) {
file, err := os.Open(a.archivePath)
if err != nil {
return false, err
}
signatureOffset := int64(a.header.SignatureOffset())
hasher := sha256.New()
buffer := make([]byte, 1024)
stat, err := file.Stat()
if err != nil {
return false, err
}
firstBlock := true
size := stat.Size()
offset := int64(0)
for ; offset < size; {
length := min(int64(len(buffer)), size-offset)
bytes, err := file.ReadAt(buffer[:length], offset)
if err != nil {
return false, err
}
if firstBlock {
firstBlock = false
override := make([]byte, 32)
copy(buffer[4:], override)
}
breakOut := false
if offset+int64(bytes) >= signatureOffset {
bytes = int(signatureOffset - offset)
breakOut = true
}
hasher.Write(buffer[:bytes])
offset += int64(bytes)
if breakOut {
break
}
}
checksum := hasher.Sum(nil)
expectedChecksum := a.header.Checksum()
return bytes.Equal(checksum, expectedChecksum[:]), nil
}