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cryptography.go
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cryptography.go
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package util
/*
Sliver Implant Framework
Copyright (C) 2021 Bishop Fox
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"errors"
"io"
)
// PreludeEncrypt the results
func PreludeEncrypt(data []byte, key []byte, iv []byte) []byte {
plainText, err := pad(data, aes.BlockSize)
if err != nil {
return make([]byte, 0)
}
block, _ := aes.NewCipher(key)
cipherText := make([]byte, aes.BlockSize+len(plainText))
// Create a random IV if none was provided
// len(nil) returns 0
if len(iv) == 0 {
iv = cipherText[:aes.BlockSize]
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
return make([]byte, 0)
}
} else {
// make sure we copy the IV
copy(cipherText[:aes.BlockSize], iv)
}
mode := cipher.NewCBCEncrypter(block, iv)
mode.CryptBlocks(cipherText[aes.BlockSize:], plainText)
return cipherText
}
// PreludeDecrypt a command
func PreludeDecrypt(data []byte, key []byte) []byte {
block, err := aes.NewCipher(key)
if err != nil {
return nil
}
iv := data[:aes.BlockSize]
data = data[aes.BlockSize:]
mode := cipher.NewCBCDecrypter(block, iv)
mode.CryptBlocks(data, data)
data, _ = unpad(data, aes.BlockSize)
return data
}
func pad(buf []byte, size int) ([]byte, error) {
bufLen := len(buf)
padLen := size - bufLen%size
padded := make([]byte, bufLen+padLen)
copy(padded, buf)
for i := 0; i < padLen; i++ {
padded[bufLen+i] = byte(padLen)
}
return padded, nil
}
func unpad(padded []byte, size int) ([]byte, error) {
if len(padded)%size != 0 {
return nil, errors.New("pkcs7: Padded value wasn't in correct size")
}
bufLen := len(padded) - int(padded[len(padded)-1])
buf := make([]byte, bufLen)
copy(buf, padded[:bufLen])
return buf, nil
}