101 lines
2.2 KiB
Go
101 lines
2.2 KiB
Go
package crypto
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"errors"
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"io"
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"google.golang.org/protobuf/reflect/protoreflect"
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"go.mau.fi/mautrix-gmessages/libgm/binary"
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)
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type Cryptor struct {
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AESCTR256Key []byte
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SHA256Key []byte
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}
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func NewCryptor(aesKey []byte, shaKey []byte) *Cryptor {
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if aesKey != nil && shaKey != nil {
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return &Cryptor{
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AESCTR256Key: aesKey,
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SHA256Key: shaKey,
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}
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}
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aesKey, shaKey = GenerateKeys()
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return &Cryptor{
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AESCTR256Key: aesKey,
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SHA256Key: shaKey,
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}
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}
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func (c *Cryptor) Encrypt(plaintext []byte) ([]byte, error) {
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iv := make([]byte, aes.BlockSize)
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if _, err := io.ReadFull(rand.Reader, iv); err != nil {
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return nil, err
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}
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block, err := aes.NewCipher(c.AESCTR256Key)
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if err != nil {
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return nil, err
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}
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ciphertext := make([]byte, len(plaintext))
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stream := cipher.NewCTR(block, iv)
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stream.XORKeyStream(ciphertext, plaintext)
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ciphertext = append(ciphertext, iv...)
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mac := hmac.New(sha256.New, c.SHA256Key)
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mac.Write(ciphertext)
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hmac := mac.Sum(nil)
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ciphertext = append(ciphertext, hmac...)
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return ciphertext, nil
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}
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func (c *Cryptor) Decrypt(encryptedData []byte) ([]byte, error) {
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if len(encryptedData) < 48 {
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return nil, errors.New("input data is too short")
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}
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hmacSignature := encryptedData[len(encryptedData)-32:]
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encryptedDataWithoutHMAC := encryptedData[:len(encryptedData)-32]
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mac := hmac.New(sha256.New, c.SHA256Key)
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mac.Write(encryptedDataWithoutHMAC)
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expectedHMAC := mac.Sum(nil)
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if !hmac.Equal(hmacSignature, expectedHMAC) {
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return nil, errors.New("HMAC mismatch")
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}
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iv := encryptedDataWithoutHMAC[len(encryptedDataWithoutHMAC)-16:]
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encryptedDataWithoutHMAC = encryptedDataWithoutHMAC[:len(encryptedDataWithoutHMAC)-16]
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block, err := aes.NewCipher(c.AESCTR256Key)
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if err != nil {
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return nil, err
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}
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stream := cipher.NewCTR(block, iv)
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stream.XORKeyStream(encryptedDataWithoutHMAC, encryptedDataWithoutHMAC)
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return encryptedDataWithoutHMAC, nil
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}
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func (c *Cryptor) DecryptAndDecodeData(encryptedData []byte, message protoreflect.ProtoMessage) error {
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decryptedData, err := c.Decrypt(encryptedData)
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if err != nil {
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return err
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}
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err = binary.DecodeProtoMessage(decryptedData, message)
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if err != nil {
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return err
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}
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return nil
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}
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