Refactor server code (#407)

internal/auth/aes.go

@@ -0,0 +1,46 @@
+package auth
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"fmt"
+	"io"
+)
+
+func AESEncrypt(key, text []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	ciphertext := make([]byte, aes.BlockSize+len(text))
+	iv := ciphertext[:aes.BlockSize]
+	if _, err = io.ReadFull(rand.Reader, iv); err != nil {
+		return nil, err
+	}
+
+	stream := cipher.NewCFBEncrypter(block, iv)
+	stream.XORKeyStream(ciphertext[aes.BlockSize:], text)
+
+	return ciphertext, nil
+}
+
+func AESDecrypt(key, ciphertext []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(ciphertext) < aes.BlockSize {
+		return nil, fmt.Errorf("ciphertext too short")
+	}
+
+	iv := ciphertext[:aes.BlockSize]
+	ciphertext = ciphertext[aes.BlockSize:]
+
+	stream := cipher.NewCFBDecrypter(block, iv)
+	stream.XORKeyStream(ciphertext, ciphertext)
+
+	return ciphertext, nil
+}