Refactor Super Graph into a library #26

core/internal/crypto/encrypt.go

@@ -0,0 +1,80 @@
+// cryptopasta - basic cryptography examples
+//
+// Written in 2015 by George Tankersley <george.tankersley@gmail.com>
+//
+// To the extent possible under law, the author(s) have dedicated all copyright
+// and related and neighboring rights to this software to the public domain
+// worldwide. This software is distributed without any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication along
+// with this software. If not, see // <http://creativecommons.org/publicdomain/zero/1.0/>.
+
+// Provides symmetric authenticated encryption using 256-bit AES-GCM with a random nonce.
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+	"io"
+)
+
+// NewEncryptionKey generates a random 256-bit key for Encrypt() and
+// Decrypt(). It panics if the source of randomness fails.
+func NewEncryptionKey() [32]byte {
+	key := [32]byte{}
+	_, err := io.ReadFull(rand.Reader, key[:])
+	if err != nil {
+		panic(err)
+	}
+	return key
+}
+
+// Encrypt encrypts data using 256-bit AES-GCM.  This both hides the content of
+// the data and provides a check that it hasn't been altered. Output takes the
+// form nonce|ciphertext|tag where '|' indicates concatenation.
+func Encrypt(plaintext []byte, key *[32]byte) (ciphertext []byte, err error) {
+	block, err := aes.NewCipher(key[:])
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	_, err = io.ReadFull(rand.Reader, nonce)
+	if err != nil {
+		return nil, err
+	}
+
+	return gcm.Seal(nonce, nonce, plaintext, nil), nil
+}
+
+// Decrypt decrypts data using 256-bit AES-GCM.  This both hides the content of
+// the data and provides a check that it hasn't been altered. Expects input
+// form nonce|ciphertext|tag where '|' indicates concatenation.
+func Decrypt(ciphertext []byte, key *[32]byte) (plaintext []byte, err error) {
+	block, err := aes.NewCipher(key[:])
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(ciphertext) < gcm.NonceSize() {
+		return nil, errors.New("malformed ciphertext")
+	}
+
+	return gcm.Open(nil,
+		ciphertext[:gcm.NonceSize()],
+		ciphertext[gcm.NonceSize():],
+		nil,
+	)
+}