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crypto.go
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crypto.go
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package tunnel
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha256"
"github.com/oxtoacart/bpool"
)
var (
// the local buffer pool
// gcmStandardNonceSize from crypto/cipher/gcm.go is 12 bytes
// 100 - is max size of pool
noncePool = bpool.NewBytePool(100, 12)
)
// hash hahes the data into 32 bytes key and returns it
// hash uses sha256 underneath to hash the supplied key
func hash(key []byte) []byte {
sum := sha256.Sum256(key)
return sum[:]
}
// Encrypt encrypts data and returns the encrypted data
func Encrypt(gcm cipher.AEAD, data []byte) ([]byte, error) {
var err error
// get new byte array the size of the nonce from pool
// NOTE: we might use smaller nonce size in the future
nonce := noncePool.Get()
if _, err = rand.Read(nonce); err != nil {
return nil, err
}
defer noncePool.Put(nonce)
// NOTE: we prepend the nonce to the payload
// we need to do this as we need the same nonce
// to decrypt the payload when receiving it
return gcm.Seal(nonce, nonce, data, nil), nil
}
// Decrypt decrypts the payload and returns the decrypted data
func newCipher(key []byte) (cipher.AEAD, error) {
var err error
// generate a new AES cipher using our 32 byte key for decrypting the message
c, err := aes.NewCipher(hash(key))
if err != nil {
return nil, err
}
// gcm or Galois/Counter Mode, is a mode of operation
// for symmetric key cryptographic block ciphers
// - https://en.wikipedia.org/wiki/Galois/Counter_Mode
gcm, err := cipher.NewGCM(c)
if err != nil {
return nil, err
}
return gcm, nil
}
func Decrypt(gcm cipher.AEAD, data []byte) ([]byte, error) {
var err error
nonceSize := gcm.NonceSize()
if len(data) < nonceSize {
return nil, ErrDecryptingData
}
// NOTE: we need to parse out nonce from the payload
// we prepend the nonce to every encrypted payload
nonce, ciphertext := data[:nonceSize], data[nonceSize:]
ciphertext, err = gcm.Open(ciphertext[:0], nonce, ciphertext, nil)
if err != nil {
return nil, err
}
return ciphertext, nil
}