95 lines
1.9 KiB
Go
95 lines
1.9 KiB
Go
package cryptfs
|
|
|
|
// File content encryption / decryption
|
|
|
|
import (
|
|
"os"
|
|
"errors"
|
|
"crypto/cipher"
|
|
)
|
|
|
|
type CryptFile struct {
|
|
file *os.File
|
|
gcm cipher.AEAD
|
|
}
|
|
|
|
// decryptBlock - Verify and decrypt GCM block
|
|
func (be *CryptFS) DecryptBlock(ciphertext []byte) ([]byte, error) {
|
|
|
|
// Empty block?
|
|
if len(ciphertext) == 0 {
|
|
return ciphertext, nil
|
|
}
|
|
|
|
if len(ciphertext) < NONCE_LEN {
|
|
warn.Printf("decryptBlock: Block is too short: %d bytes\n", len(ciphertext))
|
|
return nil, errors.New("Block is too short")
|
|
}
|
|
|
|
// Extract nonce
|
|
nonce := ciphertext[:NONCE_LEN]
|
|
ciphertext = ciphertext[NONCE_LEN:]
|
|
|
|
// Decrypt
|
|
var plaintext []byte
|
|
plaintext, err := be.gcm.Open(plaintext, nonce, ciphertext, nil)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return plaintext, nil
|
|
}
|
|
|
|
// encryptBlock - Encrypt and add MAC using GCM
|
|
func (be *CryptFS) EncryptBlock(plaintext []byte) []byte {
|
|
|
|
// Empty block?
|
|
if len(plaintext) == 0 {
|
|
return plaintext
|
|
}
|
|
|
|
// Get fresh nonce
|
|
nonce := gcmNonce.Get()
|
|
|
|
// Encrypt plaintext and append to nonce
|
|
ciphertext := be.gcm.Seal(nonce, nonce, plaintext, nil)
|
|
|
|
return ciphertext
|
|
}
|
|
|
|
// Split a plaintext byte range into (possible partial) blocks
|
|
func (be *CryptFS) SplitRange(offset uint64, length uint64) []intraBlock {
|
|
var b intraBlock
|
|
var parts []intraBlock
|
|
|
|
b.fs = be
|
|
|
|
for length > 0 {
|
|
b.BlockNo = offset / be.plainBS
|
|
b.Offset = offset % be.plainBS
|
|
b.Length = be.minu64(length, be.plainBS - b.Offset)
|
|
parts = append(parts, b)
|
|
offset += b.Length
|
|
length -= b.Length
|
|
}
|
|
return parts
|
|
}
|
|
|
|
// PlainSize - calculate plaintext size from ciphertext size
|
|
func (be *CryptFS) PlainSize(size uint64) uint64 {
|
|
// Zero sized files stay zero-sized
|
|
if size > 0 {
|
|
overhead := be.cipherBS - be.plainBS
|
|
nBlocks := (size + be.cipherBS - 1) / be.cipherBS
|
|
size -= nBlocks * overhead
|
|
}
|
|
return size
|
|
}
|
|
|
|
func (be *CryptFS) minu64(x uint64, y uint64) uint64 {
|
|
if x < y {
|
|
return x
|
|
}
|
|
return y
|
|
}
|