refactor: fold auth and crypto into deezer domain

internal/deezer/ecb.go

@@ -0,0 +1,42 @@
+package deezer
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"fmt"
+)
+
+func zeroPad(data []byte) []byte {
+	bs := aes.BlockSize
+	padded := make([]byte, len(data)+(bs-len(data)%bs)%bs)
+	copy(padded, data)
+
+	return padded
+}
+
+func ecbEncrypt(key, data []byte) ([]byte, error) {
+	return ecbTransform(key, data, (cipher.Block).Encrypt)
+}
+
+func ecbDecrypt(key, data []byte) ([]byte, error) {
+	return ecbTransform(key, data, (cipher.Block).Decrypt)
+}
+
+func ecbTransform(key, data []byte, op func(cipher.Block, []byte, []byte)) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	bs := block.BlockSize()
+	if len(data)%bs != 0 {
+		return nil, fmt.Errorf("data length %d is not a multiple of the AES block size", len(data))
+	}
+
+	out := make([]byte, len(data))
+	for i := 0; i < len(data); i += bs {
+		op(block, out[i:i+bs], data[i:i+bs])
+	}
+
+	return out, nil
+}