Add dependencies/vendor (whatsapp)

vendor/go.mau.fi/libsignal/groups/GroupCipher.go

@@ -0,0 +1,141 @@
+package groups
+
+import (
+	"fmt"
+
+	"go.mau.fi/libsignal/cipher"
+	"go.mau.fi/libsignal/ecc"
+	"go.mau.fi/libsignal/groups/ratchet"
+	"go.mau.fi/libsignal/groups/state/record"
+	"go.mau.fi/libsignal/groups/state/store"
+	"go.mau.fi/libsignal/protocol"
+	"go.mau.fi/libsignal/signalerror"
+)
+
+// NewGroupCipher will return a new group message cipher that can be used for
+// encrypt/decrypt operations.
+func NewGroupCipher(builder *SessionBuilder, senderKeyID *protocol.SenderKeyName,
+	senderKeyStore store.SenderKey) *GroupCipher {
+
+	return &GroupCipher{
+		senderKeyID:    senderKeyID,
+		senderKeyStore: senderKeyStore,
+		sessionBuilder: builder,
+	}
+}
+
+// GroupCipher is the main entry point for group encrypt/decrypt operations.
+// Once a session has been established, this can be used for
+// all encrypt/decrypt operations within that session.
+type GroupCipher struct {
+	senderKeyID    *protocol.SenderKeyName
+	senderKeyStore store.SenderKey
+	sessionBuilder *SessionBuilder
+}
+
+// Encrypt will take the given message in bytes and return encrypted bytes.
+func (c *GroupCipher) Encrypt(plaintext []byte) (protocol.GroupCiphertextMessage, error) {
+	// Load the sender key based on id from our store.
+	keyRecord := c.senderKeyStore.LoadSenderKey(c.senderKeyID)
+	senderKeyState, err := keyRecord.SenderKeyState()
+	if err != nil {
+		return nil, err
+	}
+
+	// Get the message key from the senderkey state.
+	senderKey, err := senderKeyState.SenderChainKey().SenderMessageKey()
+	if err != nil {
+		return nil, err
+	}
+
+	// Encrypt the plaintext.
+	ciphertext, err := cipher.EncryptCbc(senderKey.Iv(), senderKey.CipherKey(), plaintext)
+	if err != nil {
+		return nil, err
+	}
+
+	senderKeyMessage := protocol.NewSenderKeyMessage(
+		senderKeyState.KeyID(),
+		senderKey.Iteration(),
+		ciphertext,
+		senderKeyState.SigningKey().PrivateKey(),
+		c.sessionBuilder.serializer.SenderKeyMessage,
+	)
+
+	senderKeyState.SetSenderChainKey(senderKeyState.SenderChainKey().Next())
+	c.senderKeyStore.StoreSenderKey(c.senderKeyID, keyRecord)
+
+	return senderKeyMessage, nil
+}
+
+// Decrypt decrypts the given message using an existing session that
+// is stored in the senderKey store.
+func (c *GroupCipher) Decrypt(senderKeyMessage *protocol.SenderKeyMessage) ([]byte, error) {
+	keyRecord := c.senderKeyStore.LoadSenderKey(c.senderKeyID)
+
+	if keyRecord.IsEmpty() {
+		return nil, fmt.Errorf("%w for %s in %s", signalerror.ErrNoSenderKeyForUser, c.senderKeyID.Sender().String(), c.senderKeyID.GroupID())
+	}
+
+	// Get the senderkey state by id.
+	senderKeyState, err := keyRecord.GetSenderKeyStateByID(senderKeyMessage.KeyID())
+	if err != nil {
+		return nil, err
+	}
+
+	// Verify the signature of the senderkey message.
+	verified := c.verifySignature(senderKeyState.SigningKey().PublicKey(), senderKeyMessage)
+	if !verified {
+		return nil, signalerror.ErrSenderKeyStateVerificationFailed
+	}
+
+	senderKey, err := c.getSenderKey(senderKeyState, senderKeyMessage.Iteration())
+	if err != nil {
+		return nil, err
+	}
+
+	// Decrypt the message ciphertext.
+	plaintext, err := cipher.DecryptCbc(senderKey.Iv(), senderKey.CipherKey(), senderKeyMessage.Ciphertext())
+	if err != nil {
+		return nil, err
+	}
+
+	// Store the sender key by id.
+	c.senderKeyStore.StoreSenderKey(c.senderKeyID, keyRecord)
+
+	return plaintext, nil
+}
+
+// verifySignature will verify the signature of the senderkey message with
+// the given public key.
+func (c *GroupCipher) verifySignature(signingPubKey ecc.ECPublicKeyable,
+	senderKeyMessage *protocol.SenderKeyMessage) bool {
+
+	return ecc.VerifySignature(signingPubKey, senderKeyMessage.Serialize(), senderKeyMessage.Signature())
+}
+
+func (c *GroupCipher) getSenderKey(senderKeyState *record.SenderKeyState, iteration uint32) (*ratchet.SenderMessageKey, error) {
+	senderChainKey := senderKeyState.SenderChainKey()
+	if senderChainKey.Iteration() > iteration {
+		if senderKeyState.HasSenderMessageKey(iteration) {
+			return senderKeyState.RemoveSenderMessageKey(iteration), nil
+		}
+		return nil, fmt.Errorf("%w (current: %d, received: %d)", signalerror.ErrOldCounter, senderChainKey.Iteration(), iteration)
+	}
+
+	if iteration-senderChainKey.Iteration() > 2000 {
+		return nil, signalerror.ErrTooFarIntoFuture
+	}
+
+	for senderChainKey.Iteration() < iteration {
+		senderMessageKey, err := senderChainKey.SenderMessageKey()
+		if err != nil {
+			return nil, err
+		}
+		senderKeyState.AddSenderMessageKey(senderMessageKey)
+		senderChainKey = senderChainKey.Next()
+	}
+
+	senderKeyState.SetSenderChainKey(senderChainKey.Next())
+	return senderChainKey.SenderMessageKey()
+}