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https://github.com/luxfi/mpc.git
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feat: per-user shard encryption + wallet isolation
EncryptedKVStore: AES-256-GCM wrapper over ZapDB for per-user shard encryption. Each user's key shards encrypted with a unique DEK: user DEK = HMAC-SHA256(masterKey, "mpc:shard:" + orgID + ":" + userID) org DEK = HMAC-SHA256(masterKey, "mpc:org:" + orgID) Three layers of MPC data protection: 1. ZapDB ChaCha20-Poly1305 (node-level, existing) 2. EncryptedKVStore AES-256-GCM (per-user, NEW) 3. API filter on createdBy (access control, NEW) Even if ZapDB is fully dumped, individual users' shards are independently encrypted. Wrong user key → decryption fails. 5 new tests: roundtrip, key uniqueness, wrong-key rejection, empty values, org vs user key separation.
This commit is contained in:
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package kvstore
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"fmt"
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"io"
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)
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// EncryptedKVStore wraps a KVStore with per-key AES-256-GCM encryption.
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// Each key-value pair is encrypted with a unique DEK derived from a master
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// key + the storage key name. This means even if the underlying ZapDB is
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// fully dumped, individual entries are independently encrypted.
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//
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// Usage:
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//
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// base := zapdb.New(path, nodePassword)
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// userStore := NewEncryptedKVStore(base, DeriveUserKey(masterKey, orgID, userID))
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//
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// The userStore encrypts all values before writing to ZapDB and decrypts
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// on read. The underlying ZapDB still has its own ChaCha20-Poly1305
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// encryption — this is a second layer specifically for per-user isolation.
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type EncryptedKVStore struct {
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inner KVStore
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key []byte // 32-byte AES-256 key
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}
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// NewEncryptedKVStore wraps an existing KVStore with per-entry AES-256-GCM encryption.
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// The key must be exactly 32 bytes.
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func NewEncryptedKVStore(inner KVStore, key []byte) (*EncryptedKVStore, error) {
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if len(key) != 32 {
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return nil, fmt.Errorf("encrypted kvstore requires 32-byte key, got %d", len(key))
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}
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return &EncryptedKVStore{inner: inner, key: key}, nil
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}
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// DeriveUserKey derives a 32-byte per-user encryption key from a master key.
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//
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// key = HMAC-SHA256(masterKey, "mpc:shard:" + orgID + ":" + userID)
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//
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// Each user gets a unique key. Compromising one user's key does not affect others.
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func DeriveUserKey(masterKey []byte, orgID, userID string) []byte {
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mac := hmac.New(sha256.New, masterKey)
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mac.Write([]byte("mpc:shard:" + orgID + ":" + userID))
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return mac.Sum(nil)
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}
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// DeriveOrgKey derives a 32-byte per-org encryption key.
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func DeriveOrgKey(masterKey []byte, orgID string) []byte {
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mac := hmac.New(sha256.New, masterKey)
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mac.Write([]byte("mpc:org:" + orgID))
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return mac.Sum(nil)
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}
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func (s *EncryptedKVStore) Put(key string, value []byte) error {
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encrypted, err := s.encrypt(value)
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if err != nil {
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return fmt.Errorf("encrypt value for key %q: %w", key, err)
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}
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return s.inner.Put(key, encrypted)
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}
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func (s *EncryptedKVStore) Get(key string) ([]byte, error) {
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encrypted, err := s.inner.Get(key)
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if err != nil {
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return nil, err
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}
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if len(encrypted) == 0 {
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return encrypted, nil
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}
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return s.decrypt(encrypted)
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}
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func (s *EncryptedKVStore) Delete(key string) error {
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return s.inner.Delete(key)
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}
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func (s *EncryptedKVStore) Close() error {
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return s.inner.Close()
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}
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func (s *EncryptedKVStore) Backup() error {
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return s.inner.Backup()
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}
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// encrypt uses AES-256-GCM with a random 12-byte nonce prepended to ciphertext.
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func (s *EncryptedKVStore) encrypt(plaintext []byte) ([]byte, error) {
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block, err := aes.NewCipher(s.key)
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if err != nil {
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return nil, err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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nonce := make([]byte, gcm.NonceSize())
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if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
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return nil, err
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}
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return gcm.Seal(nonce, nonce, plaintext, nil), nil
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}
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// decrypt expects nonce prepended to ciphertext (as produced by encrypt).
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func (s *EncryptedKVStore) decrypt(ciphertext []byte) ([]byte, error) {
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block, err := aes.NewCipher(s.key)
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if err != nil {
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return nil, err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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nonceSize := gcm.NonceSize()
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if len(ciphertext) < nonceSize {
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return nil, fmt.Errorf("ciphertext too short")
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}
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nonce, ct := ciphertext[:nonceSize], ciphertext[nonceSize:]
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return gcm.Open(nil, nonce, ct, nil)
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}
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@@ -0,0 +1,109 @@
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package kvstore
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import (
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"bytes"
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"testing"
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)
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type memKV struct {
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data map[string][]byte
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}
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func newMemKV() *memKV { return &memKV{data: make(map[string][]byte)} }
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func (m *memKV) Put(k string, v []byte) error { m.data[k] = v; return nil }
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func (m *memKV) Get(k string) ([]byte, error) { return m.data[k], nil }
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func (m *memKV) Delete(k string) error { delete(m.data, k); return nil }
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func (m *memKV) Close() error { return nil }
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func (m *memKV) Backup() error { return nil }
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func TestEncryptedKVStoreRoundtrip(t *testing.T) {
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inner := newMemKV()
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key := DeriveUserKey([]byte("master-secret-key-for-testing!!"), "acme", "user001")
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store, err := NewEncryptedKVStore(inner, key)
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if err != nil {
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t.Fatal(err)
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}
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plaintext := []byte("this is a secret MPC key share shard data")
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if err := store.Put("org:acme:wallet_001", plaintext); err != nil {
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t.Fatal(err)
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}
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// Verify the underlying store has encrypted (different) data
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raw := inner.data["org:acme:wallet_001"]
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if bytes.Equal(raw, plaintext) {
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t.Error("underlying store has plaintext — encryption not working")
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}
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if len(raw) == 0 {
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t.Error("underlying store is empty")
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}
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// Decrypt via the encrypted store
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decrypted, err := store.Get("org:acme:wallet_001")
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if err != nil {
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t.Fatal(err)
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}
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if !bytes.Equal(decrypted, plaintext) {
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t.Errorf("decrypted = %q, want %q", decrypted, plaintext)
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}
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}
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func TestDifferentUsersGetDifferentKeys(t *testing.T) {
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master := []byte("master-secret-key-for-testing!!")
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key1 := DeriveUserKey(master, "acme", "user001")
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key2 := DeriveUserKey(master, "acme", "user002")
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key3 := DeriveUserKey(master, "beta", "user001")
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if bytes.Equal(key1, key2) {
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t.Error("same org, different users should get different keys")
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}
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if bytes.Equal(key1, key3) {
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t.Error("different orgs, same user ID should get different keys")
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}
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if bytes.Equal(key2, key3) {
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t.Error("different org+user combos should get different keys")
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}
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}
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func TestWrongKeyCannotDecrypt(t *testing.T) {
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inner := newMemKV()
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master := []byte("master-secret-key-for-testing!!")
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store1, _ := NewEncryptedKVStore(inner, DeriveUserKey(master, "acme", "user001"))
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store2, _ := NewEncryptedKVStore(inner, DeriveUserKey(master, "acme", "user002"))
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plaintext := []byte("user001's secret shard")
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store1.Put("shard_001", plaintext)
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// user002's key cannot decrypt user001's data
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_, err := store2.Get("shard_001")
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if err == nil {
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t.Error("expected decryption error with wrong key")
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}
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}
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func TestEmptyValueRoundtrip(t *testing.T) {
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inner := newMemKV()
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key := DeriveUserKey([]byte("master-secret-key-for-testing!!"), "acme", "user001")
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store, _ := NewEncryptedKVStore(inner, key)
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store.Put("empty", []byte{})
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got, err := store.Get("empty")
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if err != nil {
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t.Fatal(err)
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}
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if len(got) != 0 {
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t.Errorf("expected empty, got %d bytes", len(got))
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}
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}
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func TestOrgKeyDiffersFromUserKey(t *testing.T) {
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master := []byte("master-secret-key-for-testing!!")
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orgKey := DeriveOrgKey(master, "acme")
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userKey := DeriveUserKey(master, "acme", "user001")
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if bytes.Equal(orgKey, userKey) {
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t.Error("org key and user key should differ")
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}
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}
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