151 lines
3.6 KiB
Go
151 lines
3.6 KiB
Go
package cryptfs
|
|
|
|
// Filename encryption / decryption function
|
|
|
|
import (
|
|
"crypto/cipher"
|
|
"crypto/aes"
|
|
"fmt"
|
|
"strings"
|
|
"encoding/base64"
|
|
"errors"
|
|
)
|
|
|
|
const (
|
|
ENCRYPT = true
|
|
DECRYPT = false
|
|
)
|
|
|
|
// DecryptName - decrypt filename
|
|
func (be *CryptFS) decryptName(cipherName string) (string, error) {
|
|
|
|
bin, err := base64.URLEncoding.DecodeString(cipherName)
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
|
|
if len(bin) % aes.BlockSize != 0 {
|
|
return "", errors.New(fmt.Sprintf("Name len=%d is not a multiple of 16", len(bin)))
|
|
}
|
|
|
|
iv := make([]byte, aes.BlockSize) // TODO ?
|
|
cbc := cipher.NewCBCDecrypter(be.blockCipher, iv)
|
|
cbc.CryptBlocks(bin, bin)
|
|
|
|
bin, err = be.unPad16(bin)
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
|
|
plain := string(bin)
|
|
return plain, err
|
|
}
|
|
|
|
// EncryptName - encrypt filename
|
|
func (be *CryptFS) encryptName(plainName string) string {
|
|
|
|
bin := []byte(plainName)
|
|
bin = be.pad16(bin)
|
|
|
|
iv := make([]byte, 16) // TODO ?
|
|
cbc := cipher.NewCBCEncrypter(be.blockCipher, iv)
|
|
cbc.CryptBlocks(bin, bin)
|
|
|
|
cipherName64 := base64.URLEncoding.EncodeToString(bin)
|
|
|
|
return cipherName64
|
|
}
|
|
|
|
// TranslatePath - encrypt or decrypt path. Just splits the string on "/"
|
|
// and hands the parts to EncryptName() / DecryptName()
|
|
func (be *CryptFS) translatePath(path string, op bool) (string, error) {
|
|
var err error
|
|
|
|
// Empty string means root directory
|
|
if path == "" {
|
|
return path, err
|
|
}
|
|
|
|
// Run operation on each path component
|
|
var translatedParts []string
|
|
parts := strings.Split(path, "/")
|
|
for _, part := range parts {
|
|
var newPart string
|
|
if op == ENCRYPT {
|
|
newPart = be.encryptName(part)
|
|
} else {
|
|
newPart, err = be.decryptName(part)
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
}
|
|
translatedParts = append(translatedParts, newPart)
|
|
}
|
|
|
|
return strings.Join(translatedParts, "/"), err
|
|
}
|
|
|
|
// EncryptPath - encrypt filename or path. Just hands it to TranslatePath().
|
|
func (be *CryptFS) EncryptPath(path string) string {
|
|
newPath, _ := be.translatePath(path, ENCRYPT)
|
|
return newPath
|
|
}
|
|
|
|
// DecryptPath - decrypt filename or path. Just hands it to TranslatePath().
|
|
func (be *CryptFS) DecryptPath(path string) (string, error) {
|
|
return be.translatePath(path, DECRYPT)
|
|
}
|
|
|
|
// pad16 - pad filename to 16 byte blocks using standard PKCS#7 padding
|
|
// https://tools.ietf.org/html/rfc5652#section-6.3
|
|
func (be *CryptFS) pad16(orig []byte) (padded []byte) {
|
|
oldLen := len(orig)
|
|
if oldLen == 0 {
|
|
panic("Padding zero-length string makes no sense")
|
|
}
|
|
padLen := aes.BlockSize - oldLen % aes.BlockSize
|
|
if padLen == 0 {
|
|
padLen = aes.BlockSize
|
|
}
|
|
newLen := oldLen + padLen
|
|
padded = make([]byte, newLen)
|
|
copy(padded, orig)
|
|
padByte := byte(padLen)
|
|
for i := oldLen; i < newLen; i++ {
|
|
padded[i] = padByte
|
|
}
|
|
return padded
|
|
}
|
|
|
|
// unPad16 - remove padding
|
|
func (be *CryptFS) unPad16(orig []byte) ([]byte, error) {
|
|
oldLen := len(orig)
|
|
if oldLen % aes.BlockSize != 0 {
|
|
return nil, errors.New("Unaligned size")
|
|
}
|
|
// The last byte is always a padding byte
|
|
padByte := orig[oldLen -1]
|
|
// The padding byte's value is the padding length
|
|
padLen := int(padByte)
|
|
// Padding must be at least 1 byte
|
|
if padLen <= 0 {
|
|
return nil, errors.New("Padding cannot be zero-length")
|
|
}
|
|
// Larger paddings make no sense
|
|
if padLen > aes.BlockSize {
|
|
return nil, errors.New("Padding cannot be larger than 16")
|
|
}
|
|
// All padding bytes must be identical
|
|
for i := oldLen - padLen; i < oldLen; i++ {
|
|
if orig[i] != padByte {
|
|
return nil, errors.New(fmt.Sprintf("Padding byte at i=%d is invalid", i))
|
|
}
|
|
}
|
|
newLen := oldLen - padLen
|
|
// Padding an empty string makes no sense
|
|
if newLen == 0 {
|
|
return nil, errors.New("Unpadded length is zero")
|
|
}
|
|
return orig[0:newLen], nil
|
|
}
|