rclone/backend/crypt/cipher.go
Nick Craig-Wood 1648c1a0f3 crypt: calculate hashes for uploads from local disk
Before this change crypt would not calculate hashes for files it was
uploading. This is because, in the general case, they have to be
downloaded, encrypted and hashed which is too resource intensive.

However this causes backends which need the hash first before
uploading (eg s3/b2 when uploading chunked files) not to have a hash
of the file. This causes cryptcheck to complain about missing hashes
on large files uploaded via s3/b2.

This change calculates hashes for the upload if the upload is coming
from a local filesystem. It does this by encrypting and hashing the
local file re-using the code used by cryptcheck. For a local disk this
is not a lot more intensive than calculating the hash.

See: https://forum.rclone.org/t/strange-output-for-cryptcheck/15437
Fixes: #2809
2020-04-22 11:33:48 +01:00

1054 lines
28 KiB
Go

package crypt
import (
"bytes"
"context"
"crypto/aes"
gocipher "crypto/cipher"
"crypto/rand"
"encoding/base32"
"fmt"
"io"
"strconv"
"strings"
"sync"
"unicode/utf8"
"github.com/pkg/errors"
"github.com/rclone/rclone/backend/crypt/pkcs7"
"github.com/rclone/rclone/fs"
"github.com/rclone/rclone/fs/accounting"
"github.com/rfjakob/eme"
"golang.org/x/crypto/nacl/secretbox"
"golang.org/x/crypto/scrypt"
)
// Constants
const (
nameCipherBlockSize = aes.BlockSize
fileMagic = "RCLONE\x00\x00"
fileMagicSize = len(fileMagic)
fileNonceSize = 24
fileHeaderSize = fileMagicSize + fileNonceSize
blockHeaderSize = secretbox.Overhead
blockDataSize = 64 * 1024
blockSize = blockHeaderSize + blockDataSize
encryptedSuffix = ".bin" // when file name encryption is off we add this suffix to make sure the cloud provider doesn't process the file
)
// Errors returned by cipher
var (
ErrorBadDecryptUTF8 = errors.New("bad decryption - utf-8 invalid")
ErrorBadDecryptControlChar = errors.New("bad decryption - contains control chars")
ErrorNotAMultipleOfBlocksize = errors.New("not a multiple of blocksize")
ErrorTooShortAfterDecode = errors.New("too short after base32 decode")
ErrorTooLongAfterDecode = errors.New("too long after base32 decode")
ErrorEncryptedFileTooShort = errors.New("file is too short to be encrypted")
ErrorEncryptedFileBadHeader = errors.New("file has truncated block header")
ErrorEncryptedBadMagic = errors.New("not an encrypted file - bad magic string")
ErrorEncryptedBadBlock = errors.New("failed to authenticate decrypted block - bad password?")
ErrorBadBase32Encoding = errors.New("bad base32 filename encoding")
ErrorFileClosed = errors.New("file already closed")
ErrorNotAnEncryptedFile = errors.New("not an encrypted file - no \"" + encryptedSuffix + "\" suffix")
ErrorBadSeek = errors.New("Seek beyond end of file")
defaultSalt = []byte{0xA8, 0x0D, 0xF4, 0x3A, 0x8F, 0xBD, 0x03, 0x08, 0xA7, 0xCA, 0xB8, 0x3E, 0x58, 0x1F, 0x86, 0xB1}
obfuscQuoteRune = '!'
)
// Global variables
var (
fileMagicBytes = []byte(fileMagic)
)
// ReadSeekCloser is the interface of the read handles
type ReadSeekCloser interface {
io.Reader
io.Seeker
io.Closer
fs.RangeSeeker
}
// OpenRangeSeek opens the file handle at the offset with the limit given
type OpenRangeSeek func(ctx context.Context, offset, limit int64) (io.ReadCloser, error)
// NameEncryptionMode is the type of file name encryption in use
type NameEncryptionMode int
// NameEncryptionMode levels
const (
NameEncryptionOff NameEncryptionMode = iota
NameEncryptionStandard
NameEncryptionObfuscated
)
// NewNameEncryptionMode turns a string into a NameEncryptionMode
func NewNameEncryptionMode(s string) (mode NameEncryptionMode, err error) {
s = strings.ToLower(s)
switch s {
case "off":
mode = NameEncryptionOff
case "standard":
mode = NameEncryptionStandard
case "obfuscate":
mode = NameEncryptionObfuscated
default:
err = errors.Errorf("Unknown file name encryption mode %q", s)
}
return mode, err
}
// String turns mode into a human readable string
func (mode NameEncryptionMode) String() (out string) {
switch mode {
case NameEncryptionOff:
out = "off"
case NameEncryptionStandard:
out = "standard"
case NameEncryptionObfuscated:
out = "obfuscate"
default:
out = fmt.Sprintf("Unknown mode #%d", mode)
}
return out
}
// Cipher defines an encoding and decoding cipher for the crypt backend
type Cipher struct {
dataKey [32]byte // Key for secretbox
nameKey [32]byte // 16,24 or 32 bytes
nameTweak [nameCipherBlockSize]byte // used to tweak the name crypto
block gocipher.Block
mode NameEncryptionMode
buffers sync.Pool // encrypt/decrypt buffers
cryptoRand io.Reader // read crypto random numbers from here
dirNameEncrypt bool
}
// newCipher initialises the cipher. If salt is "" then it uses a built in salt val
func newCipher(mode NameEncryptionMode, password, salt string, dirNameEncrypt bool) (*Cipher, error) {
c := &Cipher{
mode: mode,
cryptoRand: rand.Reader,
dirNameEncrypt: dirNameEncrypt,
}
c.buffers.New = func() interface{} {
return make([]byte, blockSize)
}
err := c.Key(password, salt)
if err != nil {
return nil, err
}
return c, nil
}
// Key creates all the internal keys from the password passed in using
// scrypt.
//
// If salt is "" we use a fixed salt just to make attackers lives
// slighty harder than using no salt.
//
// Note that empty passsword makes all 0x00 keys which is used in the
// tests.
func (c *Cipher) Key(password, salt string) (err error) {
const keySize = len(c.dataKey) + len(c.nameKey) + len(c.nameTweak)
var saltBytes = defaultSalt
if salt != "" {
saltBytes = []byte(salt)
}
var key []byte
if password == "" {
key = make([]byte, keySize)
} else {
key, err = scrypt.Key([]byte(password), saltBytes, 16384, 8, 1, keySize)
if err != nil {
return err
}
}
copy(c.dataKey[:], key)
copy(c.nameKey[:], key[len(c.dataKey):])
copy(c.nameTweak[:], key[len(c.dataKey)+len(c.nameKey):])
// Key the name cipher
c.block, err = aes.NewCipher(c.nameKey[:])
return err
}
// getBlock gets a block from the pool of size blockSize
func (c *Cipher) getBlock() []byte {
return c.buffers.Get().([]byte)
}
// putBlock returns a block to the pool of size blockSize
func (c *Cipher) putBlock(buf []byte) {
if len(buf) != blockSize {
panic("bad blocksize returned to pool")
}
c.buffers.Put(buf)
}
// encodeFileName encodes a filename using a modified version of
// standard base32 as described in RFC4648
//
// The standard encoding is modified in two ways
// * it becomes lower case (no-one likes upper case filenames!)
// * we strip the padding character `=`
func encodeFileName(in []byte) string {
encoded := base32.HexEncoding.EncodeToString(in)
encoded = strings.TrimRight(encoded, "=")
return strings.ToLower(encoded)
}
// decodeFileName decodes a filename as encoded by encodeFileName
func decodeFileName(in string) ([]byte, error) {
if strings.HasSuffix(in, "=") {
return nil, ErrorBadBase32Encoding
}
// First figure out how many padding characters to add
roundUpToMultipleOf8 := (len(in) + 7) &^ 7
equals := roundUpToMultipleOf8 - len(in)
in = strings.ToUpper(in) + "========"[:equals]
return base32.HexEncoding.DecodeString(in)
}
// encryptSegment encrypts a path segment
//
// This uses EME with AES
//
// EME (ECB-Mix-ECB) is a wide-block encryption mode presented in the
// 2003 paper "A Parallelizable Enciphering Mode" by Halevi and
// Rogaway.
//
// This makes for determinstic encryption which is what we want - the
// same filename must encrypt to the same thing.
//
// This means that
// * filenames with the same name will encrypt the same
// * filenames which start the same won't have a common prefix
func (c *Cipher) encryptSegment(plaintext string) string {
if plaintext == "" {
return ""
}
paddedPlaintext := pkcs7.Pad(nameCipherBlockSize, []byte(plaintext))
ciphertext := eme.Transform(c.block, c.nameTweak[:], paddedPlaintext, eme.DirectionEncrypt)
return encodeFileName(ciphertext)
}
// decryptSegment decrypts a path segment
func (c *Cipher) decryptSegment(ciphertext string) (string, error) {
if ciphertext == "" {
return "", nil
}
rawCiphertext, err := decodeFileName(ciphertext)
if err != nil {
return "", err
}
if len(rawCiphertext)%nameCipherBlockSize != 0 {
return "", ErrorNotAMultipleOfBlocksize
}
if len(rawCiphertext) == 0 {
// not possible if decodeFilename() working correctly
return "", ErrorTooShortAfterDecode
}
if len(rawCiphertext) > 2048 {
return "", ErrorTooLongAfterDecode
}
paddedPlaintext := eme.Transform(c.block, c.nameTweak[:], rawCiphertext, eme.DirectionDecrypt)
plaintext, err := pkcs7.Unpad(nameCipherBlockSize, paddedPlaintext)
if err != nil {
return "", err
}
return string(plaintext), err
}
// Simple obfuscation routines
func (c *Cipher) obfuscateSegment(plaintext string) string {
if plaintext == "" {
return ""
}
// If the string isn't valid UTF8 then don't rotate; just
// prepend a !.
if !utf8.ValidString(plaintext) {
return "!." + plaintext
}
// Calculate a simple rotation based on the filename and
// the nameKey
var dir int
for _, runeValue := range plaintext {
dir += int(runeValue)
}
dir = dir % 256
// We'll use this number to store in the result filename...
var result bytes.Buffer
_, _ = result.WriteString(strconv.Itoa(dir) + ".")
// but we'll augment it with the nameKey for real calculation
for i := 0; i < len(c.nameKey); i++ {
dir += int(c.nameKey[i])
}
// Now for each character, depending on the range it is in
// we will actually rotate a different amount
for _, runeValue := range plaintext {
switch {
case runeValue == obfuscQuoteRune:
// Quote the Quote character
_, _ = result.WriteRune(obfuscQuoteRune)
_, _ = result.WriteRune(obfuscQuoteRune)
case runeValue >= '0' && runeValue <= '9':
// Number
thisdir := (dir % 9) + 1
newRune := '0' + (int(runeValue)-'0'+thisdir)%10
_, _ = result.WriteRune(rune(newRune))
case (runeValue >= 'A' && runeValue <= 'Z') ||
(runeValue >= 'a' && runeValue <= 'z'):
// ASCII letter. Try to avoid trivial A->a mappings
thisdir := dir%25 + 1
// Calculate the offset of this character in A-Za-z
pos := int(runeValue - 'A')
if pos >= 26 {
pos -= 6 // It's lower case
}
// Rotate the character to the new location
pos = (pos + thisdir) % 52
if pos >= 26 {
pos += 6 // and handle lower case offset again
}
_, _ = result.WriteRune(rune('A' + pos))
case runeValue >= 0xA0 && runeValue <= 0xFF:
// Latin 1 supplement
thisdir := (dir % 95) + 1
newRune := 0xA0 + (int(runeValue)-0xA0+thisdir)%96
_, _ = result.WriteRune(rune(newRune))
case runeValue >= 0x100:
// Some random Unicode range; we have no good rules here
thisdir := (dir % 127) + 1
base := int(runeValue - runeValue%256)
newRune := rune(base + (int(runeValue)-base+thisdir)%256)
// If the new character isn't a valid UTF8 char
// then don't rotate it. Quote it instead
if !utf8.ValidRune(newRune) {
_, _ = result.WriteRune(obfuscQuoteRune)
_, _ = result.WriteRune(runeValue)
} else {
_, _ = result.WriteRune(newRune)
}
default:
// Leave character untouched
_, _ = result.WriteRune(runeValue)
}
}
return result.String()
}
func (c *Cipher) deobfuscateSegment(ciphertext string) (string, error) {
if ciphertext == "" {
return "", nil
}
pos := strings.Index(ciphertext, ".")
if pos == -1 {
return "", ErrorNotAnEncryptedFile
} // No .
num := ciphertext[:pos]
if num == "!" {
// No rotation; probably original was not valid unicode
return ciphertext[pos+1:], nil
}
dir, err := strconv.Atoi(num)
if err != nil {
return "", ErrorNotAnEncryptedFile // Not a number
}
// add the nameKey to get the real rotate distance
for i := 0; i < len(c.nameKey); i++ {
dir += int(c.nameKey[i])
}
var result bytes.Buffer
inQuote := false
for _, runeValue := range ciphertext[pos+1:] {
switch {
case inQuote:
_, _ = result.WriteRune(runeValue)
inQuote = false
case runeValue == obfuscQuoteRune:
inQuote = true
case runeValue >= '0' && runeValue <= '9':
// Number
thisdir := (dir % 9) + 1
newRune := '0' + int(runeValue) - '0' - thisdir
if newRune < '0' {
newRune += 10
}
_, _ = result.WriteRune(rune(newRune))
case (runeValue >= 'A' && runeValue <= 'Z') ||
(runeValue >= 'a' && runeValue <= 'z'):
thisdir := dir%25 + 1
pos := int(runeValue - 'A')
if pos >= 26 {
pos -= 6
}
pos = pos - thisdir
if pos < 0 {
pos += 52
}
if pos >= 26 {
pos += 6
}
_, _ = result.WriteRune(rune('A' + pos))
case runeValue >= 0xA0 && runeValue <= 0xFF:
thisdir := (dir % 95) + 1
newRune := 0xA0 + int(runeValue) - 0xA0 - thisdir
if newRune < 0xA0 {
newRune += 96
}
_, _ = result.WriteRune(rune(newRune))
case runeValue >= 0x100:
thisdir := (dir % 127) + 1
base := int(runeValue - runeValue%256)
newRune := rune(base + (int(runeValue) - base - thisdir))
if int(newRune) < base {
newRune += 256
}
_, _ = result.WriteRune(newRune)
default:
_, _ = result.WriteRune(runeValue)
}
}
return result.String(), nil
}
// encryptFileName encrypts a file path
func (c *Cipher) encryptFileName(in string) string {
segments := strings.Split(in, "/")
for i := range segments {
// Skip directory name encryption if the user chose to
// leave them intact
if !c.dirNameEncrypt && i != (len(segments)-1) {
continue
}
if c.mode == NameEncryptionStandard {
segments[i] = c.encryptSegment(segments[i])
} else {
segments[i] = c.obfuscateSegment(segments[i])
}
}
return strings.Join(segments, "/")
}
// EncryptFileName encrypts a file path
func (c *Cipher) EncryptFileName(in string) string {
if c.mode == NameEncryptionOff {
return in + encryptedSuffix
}
return c.encryptFileName(in)
}
// EncryptDirName encrypts a directory path
func (c *Cipher) EncryptDirName(in string) string {
if c.mode == NameEncryptionOff || !c.dirNameEncrypt {
return in
}
return c.encryptFileName(in)
}
// decryptFileName decrypts a file path
func (c *Cipher) decryptFileName(in string) (string, error) {
segments := strings.Split(in, "/")
for i := range segments {
var err error
// Skip directory name decryption if the user chose to
// leave them intact
if !c.dirNameEncrypt && i != (len(segments)-1) {
continue
}
if c.mode == NameEncryptionStandard {
segments[i], err = c.decryptSegment(segments[i])
} else {
segments[i], err = c.deobfuscateSegment(segments[i])
}
if err != nil {
return "", err
}
}
return strings.Join(segments, "/"), nil
}
// DecryptFileName decrypts a file path
func (c *Cipher) DecryptFileName(in string) (string, error) {
if c.mode == NameEncryptionOff {
remainingLength := len(in) - len(encryptedSuffix)
if remainingLength > 0 && strings.HasSuffix(in, encryptedSuffix) {
return in[:remainingLength], nil
}
return "", ErrorNotAnEncryptedFile
}
return c.decryptFileName(in)
}
// DecryptDirName decrypts a directory path
func (c *Cipher) DecryptDirName(in string) (string, error) {
if c.mode == NameEncryptionOff || !c.dirNameEncrypt {
return in, nil
}
return c.decryptFileName(in)
}
// NameEncryptionMode returns the encryption mode in use for names
func (c *Cipher) NameEncryptionMode() NameEncryptionMode {
return c.mode
}
// nonce is an NACL secretbox nonce
type nonce [fileNonceSize]byte
// pointer returns the nonce as a *[24]byte for secretbox
func (n *nonce) pointer() *[fileNonceSize]byte {
return (*[fileNonceSize]byte)(n)
}
// fromReader fills the nonce from an io.Reader - normally the OSes
// crypto random number generator
func (n *nonce) fromReader(in io.Reader) error {
read, err := io.ReadFull(in, (*n)[:])
if read != fileNonceSize {
return errors.Wrap(err, "short read of nonce")
}
return nil
}
// fromBuf fills the nonce from the buffer passed in
func (n *nonce) fromBuf(buf []byte) {
read := copy((*n)[:], buf)
if read != fileNonceSize {
panic("buffer to short to read nonce")
}
}
// carry 1 up the nonce from position i
func (n *nonce) carry(i int) {
for ; i < len(*n); i++ {
digit := (*n)[i]
newDigit := digit + 1
(*n)[i] = newDigit
if newDigit >= digit {
// exit if no carry
break
}
}
}
// increment to add 1 to the nonce
func (n *nonce) increment() {
n.carry(0)
}
// add an uint64 to the nonce
func (n *nonce) add(x uint64) {
carry := uint16(0)
for i := 0; i < 8; i++ {
digit := (*n)[i]
xDigit := byte(x)
x >>= 8
carry += uint16(digit) + uint16(xDigit)
(*n)[i] = byte(carry)
carry >>= 8
}
if carry != 0 {
n.carry(8)
}
}
// encrypter encrypts an io.Reader on the fly
type encrypter struct {
mu sync.Mutex
in io.Reader
c *Cipher
nonce nonce
buf []byte
readBuf []byte
bufIndex int
bufSize int
err error
}
// newEncrypter creates a new file handle encrypting on the fly
func (c *Cipher) newEncrypter(in io.Reader, nonce *nonce) (*encrypter, error) {
fh := &encrypter{
in: in,
c: c,
buf: c.getBlock(),
readBuf: c.getBlock(),
bufSize: fileHeaderSize,
}
// Initialise nonce
if nonce != nil {
fh.nonce = *nonce
} else {
err := fh.nonce.fromReader(c.cryptoRand)
if err != nil {
return nil, err
}
}
// Copy magic into buffer
copy(fh.buf, fileMagicBytes)
// Copy nonce into buffer
copy(fh.buf[fileMagicSize:], fh.nonce[:])
return fh, nil
}
// Read as per io.Reader
func (fh *encrypter) Read(p []byte) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.err != nil {
return 0, fh.err
}
if fh.bufIndex >= fh.bufSize {
// Read data
// FIXME should overlap the reads with a go-routine and 2 buffers?
readBuf := fh.readBuf[:blockDataSize]
n, err = io.ReadFull(fh.in, readBuf)
if n == 0 {
// err can't be nil since:
// n == len(buf) if and only if err == nil.
return fh.finish(err)
}
// possibly err != nil here, but we will process the
// data and the next call to ReadFull will return 0, err
// Write nonce to start of block
copy(fh.buf, fh.nonce[:])
// Encrypt the block using the nonce
block := fh.buf
secretbox.Seal(block[:0], readBuf[:n], fh.nonce.pointer(), &fh.c.dataKey)
fh.bufIndex = 0
fh.bufSize = blockHeaderSize + n
fh.nonce.increment()
}
n = copy(p, fh.buf[fh.bufIndex:fh.bufSize])
fh.bufIndex += n
return n, nil
}
// finish sets the final error and tidies up
func (fh *encrypter) finish(err error) (int, error) {
if fh.err != nil {
return 0, fh.err
}
fh.err = err
fh.c.putBlock(fh.buf)
fh.buf = nil
fh.c.putBlock(fh.readBuf)
fh.readBuf = nil
return 0, err
}
// Encrypt data encrypts the data stream
func (c *Cipher) encryptData(in io.Reader) (io.Reader, *encrypter, error) {
in, wrap := accounting.UnWrap(in) // unwrap the accounting off the Reader
out, err := c.newEncrypter(in, nil)
if err != nil {
return nil, nil, err
}
return wrap(out), out, nil // and wrap the accounting back on
}
// EncryptData encrypts the data stream
func (c *Cipher) EncryptData(in io.Reader) (io.Reader, error) {
out, _, err := c.encryptData(in)
return out, err
}
// decrypter decrypts an io.ReaderCloser on the fly
type decrypter struct {
mu sync.Mutex
rc io.ReadCloser
nonce nonce
initialNonce nonce
c *Cipher
buf []byte
readBuf []byte
bufIndex int
bufSize int
err error
limit int64 // limit of bytes to read, -1 for unlimited
open OpenRangeSeek
}
// newDecrypter creates a new file handle decrypting on the fly
func (c *Cipher) newDecrypter(rc io.ReadCloser) (*decrypter, error) {
fh := &decrypter{
rc: rc,
c: c,
buf: c.getBlock(),
readBuf: c.getBlock(),
limit: -1,
}
// Read file header (magic + nonce)
readBuf := fh.readBuf[:fileHeaderSize]
_, err := io.ReadFull(fh.rc, readBuf)
if err == io.EOF || err == io.ErrUnexpectedEOF {
// This read from 0..fileHeaderSize-1 bytes
return nil, fh.finishAndClose(ErrorEncryptedFileTooShort)
} else if err != nil {
return nil, fh.finishAndClose(err)
}
// check the magic
if !bytes.Equal(readBuf[:fileMagicSize], fileMagicBytes) {
return nil, fh.finishAndClose(ErrorEncryptedBadMagic)
}
// retrieve the nonce
fh.nonce.fromBuf(readBuf[fileMagicSize:])
fh.initialNonce = fh.nonce
return fh, nil
}
// newDecrypterSeek creates a new file handle decrypting on the fly
func (c *Cipher) newDecrypterSeek(ctx context.Context, open OpenRangeSeek, offset, limit int64) (fh *decrypter, err error) {
var rc io.ReadCloser
doRangeSeek := false
setLimit := false
// Open initially with no seek
if offset == 0 && limit < 0 {
// If no offset or limit then open whole file
rc, err = open(ctx, 0, -1)
} else if offset == 0 {
// If no offset open the header + limit worth of the file
_, underlyingLimit, _, _ := calculateUnderlying(offset, limit)
rc, err = open(ctx, 0, int64(fileHeaderSize)+underlyingLimit)
setLimit = true
} else {
// Otherwise just read the header to start with
rc, err = open(ctx, 0, int64(fileHeaderSize))
doRangeSeek = true
}
if err != nil {
return nil, err
}
// Open the stream which fills in the nonce
fh, err = c.newDecrypter(rc)
if err != nil {
return nil, err
}
fh.open = open // will be called by fh.RangeSeek
if doRangeSeek {
_, err = fh.RangeSeek(ctx, offset, io.SeekStart, limit)
if err != nil {
_ = fh.Close()
return nil, err
}
}
if setLimit {
fh.limit = limit
}
return fh, nil
}
// read data into internal buffer - call with fh.mu held
func (fh *decrypter) fillBuffer() (err error) {
// FIXME should overlap the reads with a go-routine and 2 buffers?
readBuf := fh.readBuf
n, err := io.ReadFull(fh.rc, readBuf)
if n == 0 {
// err can't be nil since:
// n == len(buf) if and only if err == nil.
return err
}
// possibly err != nil here, but we will process the data and
// the next call to ReadFull will return 0, err
// Check header + 1 byte exists
if n <= blockHeaderSize {
if err != nil {
return err // return pending error as it is likely more accurate
}
return ErrorEncryptedFileBadHeader
}
// Decrypt the block using the nonce
block := fh.buf
_, ok := secretbox.Open(block[:0], readBuf[:n], fh.nonce.pointer(), &fh.c.dataKey)
if !ok {
if err != nil {
return err // return pending error as it is likely more accurate
}
return ErrorEncryptedBadBlock
}
fh.bufIndex = 0
fh.bufSize = n - blockHeaderSize
fh.nonce.increment()
return nil
}
// Read as per io.Reader
func (fh *decrypter) Read(p []byte) (n int, err error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.err != nil {
return 0, fh.err
}
if fh.bufIndex >= fh.bufSize {
err = fh.fillBuffer()
if err != nil {
return 0, fh.finish(err)
}
}
toCopy := fh.bufSize - fh.bufIndex
if fh.limit >= 0 && fh.limit < int64(toCopy) {
toCopy = int(fh.limit)
}
n = copy(p, fh.buf[fh.bufIndex:fh.bufIndex+toCopy])
fh.bufIndex += n
if fh.limit >= 0 {
fh.limit -= int64(n)
if fh.limit == 0 {
return n, fh.finish(io.EOF)
}
}
return n, nil
}
// calculateUnderlying converts an (offset, limit) in a crypted file
// into an (underlyingOffset, underlyingLimit) for the underlying
// file.
//
// It also returns number of bytes to discard after reading the first
// block and number of blocks this is from the start so the nonce can
// be incremented.
func calculateUnderlying(offset, limit int64) (underlyingOffset, underlyingLimit, discard, blocks int64) {
// blocks we need to seek, plus bytes we need to discard
blocks, discard = offset/blockDataSize, offset%blockDataSize
// Offset in underlying stream we need to seek
underlyingOffset = int64(fileHeaderSize) + blocks*(blockHeaderSize+blockDataSize)
// work out how many blocks we need to read
underlyingLimit = int64(-1)
if limit >= 0 {
// bytes to read beyond the first block
bytesToRead := limit - (blockDataSize - discard)
// Read the first block
blocksToRead := int64(1)
if bytesToRead > 0 {
// Blocks that need to be read plus left over blocks
extraBlocksToRead, endBytes := bytesToRead/blockDataSize, bytesToRead%blockDataSize
if endBytes != 0 {
// If left over bytes must read another block
extraBlocksToRead++
}
blocksToRead += extraBlocksToRead
}
// Must read a whole number of blocks
underlyingLimit = blocksToRead * (blockHeaderSize + blockDataSize)
}
return
}
// RangeSeek behaves like a call to Seek(offset int64, whence
// int) with the output wrapped in an io.LimitedReader
// limiting the total length to limit.
//
// RangeSeek with a limit of < 0 is equivalent to a regular Seek.
func (fh *decrypter) RangeSeek(ctx context.Context, offset int64, whence int, limit int64) (int64, error) {
fh.mu.Lock()
defer fh.mu.Unlock()
if fh.open == nil {
return 0, fh.finish(errors.New("can't seek - not initialised with newDecrypterSeek"))
}
if whence != io.SeekStart {
return 0, fh.finish(errors.New("can only seek from the start"))
}
// Reset error or return it if not EOF
if fh.err == io.EOF {
fh.unFinish()
} else if fh.err != nil {
return 0, fh.err
}
underlyingOffset, underlyingLimit, discard, blocks := calculateUnderlying(offset, limit)
// Move the nonce on the correct number of blocks from the start
fh.nonce = fh.initialNonce
fh.nonce.add(uint64(blocks))
// Can we seek underlying stream directly?
if do, ok := fh.rc.(fs.RangeSeeker); ok {
// Seek underlying stream directly
_, err := do.RangeSeek(ctx, underlyingOffset, 0, underlyingLimit)
if err != nil {
return 0, fh.finish(err)
}
} else {
// if not reopen with seek
_ = fh.rc.Close() // close underlying file
fh.rc = nil
// Re-open the underlying object with the offset given
rc, err := fh.open(ctx, underlyingOffset, underlyingLimit)
if err != nil {
return 0, fh.finish(errors.Wrap(err, "couldn't reopen file with offset and limit"))
}
// Set the file handle
fh.rc = rc
}
// Fill the buffer
err := fh.fillBuffer()
if err != nil {
return 0, fh.finish(err)
}
// Discard bytes from the buffer
if int(discard) > fh.bufSize {
return 0, fh.finish(ErrorBadSeek)
}
fh.bufIndex = int(discard)
// Set the limit
fh.limit = limit
return offset, nil
}
// Seek implements the io.Seeker interface
func (fh *decrypter) Seek(offset int64, whence int) (int64, error) {
return fh.RangeSeek(context.TODO(), offset, whence, -1)
}
// finish sets the final error and tidies up
func (fh *decrypter) finish(err error) error {
if fh.err != nil {
return fh.err
}
fh.err = err
fh.c.putBlock(fh.buf)
fh.buf = nil
fh.c.putBlock(fh.readBuf)
fh.readBuf = nil
return err
}
// unFinish undoes the effects of finish
func (fh *decrypter) unFinish() {
// Clear error
fh.err = nil
// reinstate the buffers
fh.buf = fh.c.getBlock()
fh.readBuf = fh.c.getBlock()
// Empty the buffer
fh.bufIndex = 0
fh.bufSize = 0
}
// Close
func (fh *decrypter) Close() error {
fh.mu.Lock()
defer fh.mu.Unlock()
// Check already closed
if fh.err == ErrorFileClosed {
return fh.err
}
// Closed before reading EOF so not finish()ed yet
if fh.err == nil {
_ = fh.finish(io.EOF)
}
// Show file now closed
fh.err = ErrorFileClosed
if fh.rc == nil {
return nil
}
return fh.rc.Close()
}
// finishAndClose does finish then Close()
//
// Used when we are returning a nil fh from new
func (fh *decrypter) finishAndClose(err error) error {
_ = fh.finish(err)
_ = fh.Close()
return err
}
// DecryptData decrypts the data stream
func (c *Cipher) DecryptData(rc io.ReadCloser) (io.ReadCloser, error) {
out, err := c.newDecrypter(rc)
if err != nil {
return nil, err
}
return out, nil
}
// DecryptDataSeek decrypts the data stream from offset
//
// The open function must return a ReadCloser opened to the offset supplied
//
// You must use this form of DecryptData if you might want to Seek the file handle
func (c *Cipher) DecryptDataSeek(ctx context.Context, open OpenRangeSeek, offset, limit int64) (ReadSeekCloser, error) {
out, err := c.newDecrypterSeek(ctx, open, offset, limit)
if err != nil {
return nil, err
}
return out, nil
}
// EncryptedSize calculates the size of the data when encrypted
func (c *Cipher) EncryptedSize(size int64) int64 {
blocks, residue := size/blockDataSize, size%blockDataSize
encryptedSize := int64(fileHeaderSize) + blocks*(blockHeaderSize+blockDataSize)
if residue != 0 {
encryptedSize += blockHeaderSize + residue
}
return encryptedSize
}
// DecryptedSize calculates the size of the data when decrypted
func (c *Cipher) DecryptedSize(size int64) (int64, error) {
size -= int64(fileHeaderSize)
if size < 0 {
return 0, ErrorEncryptedFileTooShort
}
blocks, residue := size/blockSize, size%blockSize
decryptedSize := blocks * blockDataSize
if residue != 0 {
residue -= blockHeaderSize
if residue <= 0 {
return 0, ErrorEncryptedFileBadHeader
}
}
decryptedSize += residue
return decryptedSize, nil
}
// check interfaces
var (
_ io.ReadCloser = (*decrypter)(nil)
_ io.Seeker = (*decrypter)(nil)
_ fs.RangeSeeker = (*decrypter)(nil)
_ io.Reader = (*encrypter)(nil)
)