103 lines
2.3 KiB
Go
103 lines
2.3 KiB
Go
package crypto
|
|
|
|
import (
|
|
"crypto/aes"
|
|
"crypto/cipher"
|
|
"crypto/hmac"
|
|
"crypto/rand"
|
|
"crypto/sha256"
|
|
"errors"
|
|
"io"
|
|
|
|
"google.golang.org/protobuf/proto"
|
|
|
|
"go.mau.fi/mautrix-gmessages/libgm/binary"
|
|
)
|
|
|
|
type Cryptor struct {
|
|
AESKey []byte `json:"aes_key"`
|
|
HMACKey []byte `json:"hmac_key"`
|
|
}
|
|
|
|
func NewCryptor(aesKey []byte, hmacKey []byte) *Cryptor {
|
|
if aesKey != nil && hmacKey != nil {
|
|
return &Cryptor{
|
|
AESKey: aesKey,
|
|
HMACKey: hmacKey,
|
|
}
|
|
}
|
|
aesKey, hmacKey = GenerateKeys()
|
|
return &Cryptor{
|
|
AESKey: aesKey,
|
|
HMACKey: hmacKey,
|
|
}
|
|
}
|
|
|
|
func (c *Cryptor) Encrypt(plaintext []byte) ([]byte, error) {
|
|
iv := make([]byte, aes.BlockSize)
|
|
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
block, err := aes.NewCipher(c.AESKey)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
ciphertext := make([]byte, len(plaintext))
|
|
stream := cipher.NewCTR(block, iv)
|
|
stream.XORKeyStream(ciphertext, plaintext)
|
|
|
|
ciphertext = append(ciphertext, iv...)
|
|
|
|
mac := hmac.New(sha256.New, c.HMACKey)
|
|
mac.Write(ciphertext)
|
|
hmac := mac.Sum(nil)
|
|
|
|
ciphertext = append(ciphertext, hmac...)
|
|
|
|
return ciphertext, nil
|
|
}
|
|
|
|
func (c *Cryptor) Decrypt(encryptedData []byte) ([]byte, error) {
|
|
if len(encryptedData) < 48 {
|
|
return nil, errors.New("input data is too short")
|
|
}
|
|
|
|
hmacSignature := encryptedData[len(encryptedData)-32:]
|
|
encryptedDataWithoutHMAC := encryptedData[:len(encryptedData)-32]
|
|
|
|
mac := hmac.New(sha256.New, c.HMACKey)
|
|
mac.Write(encryptedDataWithoutHMAC)
|
|
expectedHMAC := mac.Sum(nil)
|
|
|
|
if !hmac.Equal(hmacSignature, expectedHMAC) {
|
|
return nil, errors.New("HMAC mismatch")
|
|
}
|
|
|
|
iv := encryptedDataWithoutHMAC[len(encryptedDataWithoutHMAC)-16:]
|
|
encryptedDataWithoutHMAC = encryptedDataWithoutHMAC[:len(encryptedDataWithoutHMAC)-16]
|
|
|
|
block, err := aes.NewCipher(c.AESKey)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
stream := cipher.NewCTR(block, iv)
|
|
stream.XORKeyStream(encryptedDataWithoutHMAC, encryptedDataWithoutHMAC)
|
|
|
|
return encryptedDataWithoutHMAC, nil
|
|
}
|
|
|
|
func (c *Cryptor) EncodeAndEncryptData(message proto.Message) ([]byte, error) {
|
|
encodedData, encodeErr := binary.EncodeProtoMessage(message)
|
|
if encodeErr != nil {
|
|
return nil, encodeErr
|
|
}
|
|
|
|
encryptedData, encryptErr := c.Encrypt(encodedData)
|
|
if encryptErr != nil {
|
|
return nil, encryptErr
|
|
}
|
|
|
|
return encryptedData, nil
|
|
}
|