selfpass/sp/crypto/cbc.go

69 lines
1.4 KiB
Go

package crypto
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"fmt"
"io"
"github.com/ncw/rclone/backend/crypt/pkcs7"
)
func CBCEncrypt(key []byte, plaintext []byte) ([]byte, error) {
if len(key) != 32 {
return nil, fmt.Errorf("key is not 32 bytes")
}
plaintext = pkcs7.Pad(aes.BlockSize, plaintext)
if len(plaintext)%aes.BlockSize != 0 {
return nil, fmt.Errorf("plaintext is not a multiple of the block size")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
ciphertext := make([]byte, aes.BlockSize+len(plaintext))
iv := ciphertext[:aes.BlockSize]
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
return nil, err
}
mode := cipher.NewCBCEncrypter(block, iv)
mode.CryptBlocks(ciphertext[aes.BlockSize:], plaintext)
return ciphertext, nil
}
func CBCDecrypt(key []byte, ciphertext []byte) ([]byte, error) {
if len(key) != 32 {
return nil, fmt.Errorf("key is not 32 bytes")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
if len(ciphertext) < aes.BlockSize {
return nil, err
}
iv := ciphertext[:aes.BlockSize]
ciphertext = ciphertext[aes.BlockSize:]
if len(ciphertext)%aes.BlockSize != 0 {
return nil, fmt.Errorf("ciphertext is not a multiple of the block size")
}
mode := cipher.NewCBCDecrypter(block, iv)
mode.CryptBlocks(ciphertext, ciphertext)
return pkcs7.Unpad(aes.BlockSize, ciphertext)
}