added fs encryption overlay

pkg/provider/crypto/crypto.go

@@ -0,0 +1,92 @@
+package crypto
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/sha256"
+	"io"
+
+	"golang.org/x/crypto/chacha20poly1305"
+	"golang.org/x/crypto/hkdf"
+)
+
+const (
+	KDFNonceSize = 16
+	NonceSize    = chacha20poly1305.NonceSize
+	Overhead     = chacha20poly1305.Overhead
+	ChunkSize    = 64 * 1024
+	FullSize     = ChunkSize + Overhead
+)
+
+const (
+	infoCBC     = "AES-CBC filename encryption key"
+	infoCBCIV   = "AES-CBC filename encryption initialization vector"
+	infoChaPloy = "ChaCha20-Poly1305 file content encryption"
+)
+
+func cbcKey(key []byte) []byte {
+	return deriveKey(key, nil, infoCBC, 32)
+}
+
+func cbcIV(key []byte) []byte {
+	return deriveKey(key, nil, infoCBCIV, 16)
+}
+
+func streamKey(key, nonce []byte) []byte {
+	return deriveKey(key, nonce, infoChaPloy, chacha20poly1305.KeySize)
+}
+
+func deriveKey(key, nonce []byte, info string, length int) []byte {
+	h := hkdf.New(sha256.New, key, nonce, []byte(info))
+	k := make([]byte, length)
+	if _, err := io.ReadFull(h, k); err != nil {
+		panic("crypto: internal error: failed to read from HKDF: " + err.Error())
+	}
+	return k
+}
+
+type aesCbc struct {
+	key []byte
+	iv  []byte
+}
+
+func newAesCbc(key []byte) (*aesCbc, error) {
+	cbc := &aesCbc{
+		key: cbcKey(key),
+		iv:  cbcIV(key),
+	}
+	_, err := aes.NewCipher(cbc.key)
+	if err != nil {
+		return nil, err
+	}
+	return cbc, nil
+}
+
+func (cbc *aesCbc) encrypt(p []byte) (c []byte) {
+	block, _ := aes.NewCipher(cbc.key)
+	mode := cipher.NewCBCEncrypter(block, cbc.iv)
+	padded := padPKCS5(p, block.BlockSize())
+	c = make([]byte, len(padded))
+	mode.CryptBlocks(c, padded)
+	return
+}
+
+func (cbc *aesCbc) decrypt(c []byte) []byte {
+	block, _ := aes.NewCipher(cbc.key)
+	mode := cipher.NewCBCDecrypter(block, cbc.iv)
+	p := make([]byte, len(c))
+	mode.CryptBlocks(p, c)
+	return trimPKCS5(p)
+}
+
+func padPKCS5(b []byte, bs int) []byte {
+	n := bs - len(b)%bs
+	pad := bytes.Repeat([]byte{byte(n)}, n)
+	return append(b, pad...)
+}
+
+func trimPKCS5(b []byte) []byte {
+	pad := b[len(b)-1]
+	return b[:len(b)-int(pad)]
+}