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// Copyright (c) 2024 Sumner Evans
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
package aescbc
import (
"crypto/aes"
"crypto/cipher"
"maunium.net/go/mautrix/crypto/pkcs7"
)
// Encrypt encrypts the plaintext with the key and IV. The IV length must be
// equal to the AES block size.
//
// This function might mutate the plaintext.
func Encrypt(key, iv, plaintext []byte) ([]byte, error) {
if len(key) == 0 {
return nil, ErrNoKeyProvided
}
if len(iv) != aes.BlockSize {
return nil, ErrIVNotBlockSize
}
plaintext = pkcs7.Pad(plaintext, aes.BlockSize)
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
cipher.NewCBCEncrypter(block, iv).CryptBlocks(plaintext, plaintext)
return plaintext, nil
}
// Decrypt decrypts the ciphertext with the key and IV. The IV length must be
// equal to the block size.
//
// This function mutates the ciphertext.
func Decrypt(key, iv, ciphertext []byte) ([]byte, error) {
if len(key) == 0 {
return nil, ErrNoKeyProvided
}
if len(iv) != aes.BlockSize {
return nil, ErrIVNotBlockSize
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
if len(ciphertext) < aes.BlockSize {
return nil, ErrNotMultipleBlockSize
}
cipher.NewCBCDecrypter(block, iv).CryptBlocks(ciphertext, ciphertext)
return pkcs7.Unpad(ciphertext), nil
}
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