feat(meta): values symmetric encryption

pkg/crypto/aes.go

@@ -0,0 +1,62 @@
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+	"io"
+)
+
+var ErrShortCipherText = errors.New("ciphertext too short")
+
+func EncryptWithAESKey(data, key []byte) ([]byte, error) {
+	if key == nil {
+		return data, nil
+	}
+
+	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())
+	if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, err
+	}
+
+	return gcm.Seal(nonce, nonce, data, nil), nil
+}
+
+func DecryptStringWithAESKey(data, key []byte) ([]byte, error) {
+	if key == nil {
+		return data, nil
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(data) < gcm.NonceSize() {
+		return nil, ErrShortCipherText
+	}
+
+	nonce, ciphertext := data[:gcm.NonceSize()], data[gcm.NonceSize():]
+	decrypted, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return decrypted, nil
+}

pkg/crypto/aes_test.go

@@ -0,0 +1,113 @@
+package crypto
+
+import (
+	"bytes"
+	"crypto/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestAESEncryption(t *testing.T) {
+	t.Parallel()
+
+	key := make([]byte, 32) // generated random 32-byte key
+	_, err := rand.Read(key)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name    string
+		data    []byte
+		key     []byte
+		wantErr bool
+	}{
+		{
+			name:    "valid encryption/decryption",
+			data:    []byte("hello world"),
+			key:     key,
+			wantErr: false,
+		},
+		{
+			name:    "nil key returns original data",
+			data:    []byte("hello world"),
+			key:     nil,
+			wantErr: false,
+		},
+		{
+			name:    "empty data",
+			data:    []byte{},
+			key:     key,
+			wantErr: false,
+		},
+		{
+			name:    "invalid key size",
+			data:    []byte("hello world"),
+			key:     make([]byte, 31),
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			encrypted, err := EncryptWithAESKey(tt.data, tt.key)
+			if tt.wantErr {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+
+			decrypted, err := DecryptStringWithAESKey(encrypted, tt.key)
+			require.NoError(t, err)
+
+			if tt.key == nil {
+				require.Equal(t, tt.data, encrypted)
+				require.Equal(t, tt.data, decrypted)
+			} else {
+				require.NotEqual(t, tt.data, encrypted)
+				require.True(t, bytes.Equal(tt.data, decrypted))
+			}
+		})
+	}
+}
+
+func TestDecryptionErrors(t *testing.T) {
+	t.Parallel()
+
+	key := make([]byte, 32)
+	_, err := rand.Read(key)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name   string
+		data   []byte
+		key    []byte
+		errMsg string
+	}{
+		{
+			name:   "short ciphertext",
+			data:   []byte("short"),
+			key:    key,
+			errMsg: "ciphertext too short",
+		},
+		{
+			name:   "invalid ciphertext",
+			data:   make([]byte, 16), // just nonce size
+			key:    key,
+			errMsg: "message authentication failed",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := DecryptStringWithAESKey(tt.data, tt.key)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), tt.errMsg)
+		})
+	}
+}

pkg/meta/meta.go

@@ -10,11 +10,13 @@ import (
 	"github.com/ipld/go-ipld-prime/datamodel"
 	"github.com/ipld/go-ipld-prime/node/basicnode"
 	"github.com/ipld/go-ipld-prime/printer"
+
+	"github.com/ucan-wg/go-ucan/pkg/crypto"
 )
 
 var ErrUnsupported = errors.New("failure adding unsupported type to meta")
-
 var ErrNotFound = errors.New("key-value not found in meta")
+var ErrNotEncryptable = errors.New("value of this type cannot be encrypted")
 
 // Meta is a container for meta key-value pairs in a UCAN token.
 // This also serves as a way to construct the underlying IPLD data with minimum allocations and transformations,
@@ -51,6 +53,21 @@ func (m *Meta) GetString(key string) (string, error) {
 	return v.AsString()
 }
 
+// GetEncryptedString decorates GetString and decrypt its output with the given symmetric encryption key.
+func (m *Meta) GetEncryptedString(key string, encryptionKey []byte) (string, error) {
+	v, err := m.GetString(key)
+	if err != nil {
+		return "", err
+	}
+
+	decrypted, err := crypto.DecryptStringWithAESKey([]byte(v), encryptionKey)
+	if err != nil {
+		return "", err
+	}
+
+	return string(decrypted), nil
+}
+
 // GetInt64 retrieves a value as an int64.
 // Returns ErrNotFound if the given key is missing.
 // Returns datamodel.ErrWrongKind if the value has the wrong type.
@@ -84,6 +101,21 @@ func (m *Meta) GetBytes(key string) ([]byte, error) {
 	return v.AsBytes()
 }
 
+// GetEncryptedBytes decorates GetBytes and decrypt its output with the given symmetric encryption key.
+func (m *Meta) GetEncryptedBytes(key string, encryptionKey []byte) ([]byte, error) {
+	v, err := m.GetBytes(key)
+	if err != nil {
+		return nil, err
+	}
+
+	decrypted, err := crypto.DecryptStringWithAESKey(v, encryptionKey)
+	if err != nil {
+		return nil, err
+	}
+
+	return decrypted, nil
+}
+
 // GetNode retrieves a value as a raw IPLD node.
 // Returns ErrNotFound if the given key is missing.
 // Returns datamodel.ErrWrongKind if the value has the wrong type.
@@ -125,6 +157,31 @@ func (m *Meta) Add(key string, val any) error {
 	return nil
 }
 
+// AddEncrypted adds a key/value pair in the meta set.
+// The value is encrypted with the given encryptionKey.
+// Accepted types for the value are: string, []byte.
+func (m *Meta) AddEncrypted(key string, val any, encryptionKey []byte) error {
+	var encrypted []byte
+	var err error
+
+	switch val := val.(type) {
+	case string:
+		encrypted, err = crypto.EncryptWithAESKey([]byte(val), encryptionKey)
+		if err != nil {
+			return err
+		}
+		return m.Add(key, string(encrypted))
+	case []byte:
+		encrypted, err = crypto.EncryptWithAESKey(val, encryptionKey)
+		if err != nil {
+			return err
+		}
+		return m.Add(key, encrypted)
+	default:
+		return ErrNotEncryptable
+	}
+}
+
 // Equals tells if two Meta hold the same key/values.
 func (m *Meta) Equals(other *Meta) bool {
 	if len(m.Keys) != len(other.Keys) {

pkg/meta/meta_test.go

@@ -1,6 +1,7 @@
 package meta_test
 
 import (
+	"crypto/rand"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -14,11 +15,69 @@ func TestMeta_Add(t *testing.T) {
 
 	type Unsupported struct{}
 
-	t.Run("error if not primative or Node", func(t *testing.T) {
+	t.Run("error if not primitive or Node", func(t *testing.T) {
 		t.Parallel()
 
 		err := (&meta.Meta{}).Add("invalid", &Unsupported{})
 		require.ErrorIs(t, err, meta.ErrUnsupported)
 		assert.ErrorContains(t, err, "*github.com/ucan-wg/go-ucan/pkg/meta_test.Unsupported")
 	})
+
+	t.Run("encrypted meta", func(t *testing.T) {
+		t.Parallel()
+
+		key := make([]byte, 32)
+		_, err := rand.Read(key)
+		require.NoError(t, err)
+
+		m := meta.NewMeta()
+
+		// string encryption
+		err = m.AddEncrypted("secret", "hello world", key)
+		require.NoError(t, err)
+
+		encrypted, err := m.GetString("secret")
+		require.NoError(t, err)
+		require.NotEqual(t, "hello world", encrypted)
+
+		decrypted, err := m.GetEncryptedString("secret", key)
+		require.NoError(t, err)
+		require.Equal(t, "hello world", decrypted)
+
+		// bytes encryption
+		originalBytes := make([]byte, 128)
+		_, err = rand.Read(originalBytes)
+		require.NoError(t, err)
+		err = m.AddEncrypted("secret-bytes", originalBytes, key)
+		require.NoError(t, err)
+
+		encryptedBytes, err := m.GetBytes("secret-bytes")
+		require.NoError(t, err)
+		require.NotEqual(t, originalBytes, encryptedBytes)
+
+		decryptedBytes, err := m.GetEncryptedBytes("secret-bytes", key)
+		require.NoError(t, err)
+		require.Equal(t, originalBytes, decryptedBytes)
+
+		// error cases
+		t.Run("error on unsupported type", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", 123, key)
+			require.ErrorIs(t, err, meta.ErrNotEncryptable)
+		})
+
+		t.Run("error on invalid key size", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", "test", []byte("short-key"))
+			require.Error(t, err)
+			require.Contains(t, err.Error(), "invalid key size")
+		})
+
+		t.Run("error on nil key", func(t *testing.T) {
+			err := m.AddEncrypted("invalid", "test", nil)
+			require.NoError(t, err)
+			// with nil key, value should be stored unencrypted
+			val, err := m.GetString("invalid")
+			require.NoError(t, err)
+			require.Equal(t, "test", val)
+		})
+	})
 }