1 files changed, 84 insertions, 0 deletions
diff --git a/vendor/go.mau.fi/libsignal/groups/GroupSessionBuilder.go b/vendor/go.mau.fi/libsignal/groups/GroupSessionBuilder.go
new file mode 100644
index 00000000..2a5569b7
--- /dev/null
+++ b/vendor/go.mau.fi/libsignal/groups/GroupSessionBuilder.go
@@ -0,0 +1,84 @@
+// Package groups is responsible for setting up group SenderKey encrypted sessions.
+// Once a session has been established, GroupCipher can be used to encrypt/decrypt
+// messages in that session.
+//
+// The built sessions are unidirectional: they can be used either for sending or
+// for receiving, but not both. Sessions are constructed per (groupId + senderId +
+// deviceId) tuple. Remote logical users are identified by their senderId, and each
+// logical recipientId can have multiple physical devices.
+package groups
+
+import (
+	"go.mau.fi/libsignal/groups/state/record"
+	"go.mau.fi/libsignal/groups/state/store"
+	"go.mau.fi/libsignal/protocol"
+	"go.mau.fi/libsignal/serialize"
+	"go.mau.fi/libsignal/util/keyhelper"
+)
+
+// NewGroupSessionBuilder will return a new group session builder.
+func NewGroupSessionBuilder(senderKeyStore store.SenderKey,
+	serializer *serialize.Serializer) *SessionBuilder {
+
+	return &SessionBuilder{
+		senderKeyStore: senderKeyStore,
+		serializer:     serializer,
+	}
+}
+
+// SessionBuilder is a structure for building group sessions.
+type SessionBuilder struct {
+	senderKeyStore store.SenderKey
+	serializer     *serialize.Serializer
+}
+
+// Process will process an incoming group message and set up the corresponding
+// session for it.
+func (b *SessionBuilder) Process(senderKeyName *protocol.SenderKeyName,
+	msg *protocol.SenderKeyDistributionMessage) {
+
+	senderKeyRecord := b.senderKeyStore.LoadSenderKey(senderKeyName)
+	if senderKeyRecord == nil {
+		senderKeyRecord = record.NewSenderKey(b.serializer.SenderKeyRecord, b.serializer.SenderKeyState)
+	}
+	senderKeyRecord.AddSenderKeyState(msg.ID(), msg.Iteration(), msg.ChainKey(), msg.SignatureKey())
+	b.senderKeyStore.StoreSenderKey(senderKeyName, senderKeyRecord)
+}
+
+// Create will create a new group session for the given name.
+func (b *SessionBuilder) Create(senderKeyName *protocol.SenderKeyName) (*protocol.SenderKeyDistributionMessage, error) {
+	// Load the senderkey by name
+	senderKeyRecord := b.senderKeyStore.LoadSenderKey(senderKeyName)
+
+	// If the record is empty, generate new keys.
+	if senderKeyRecord == nil || senderKeyRecord.IsEmpty() {
+		senderKeyRecord = record.NewSenderKey(b.serializer.SenderKeyRecord, b.serializer.SenderKeyState)
+		signingKey, err := keyhelper.GenerateSenderSigningKey()
+		if err != nil {
+			return nil, err
+		}
+		senderKeyRecord.SetSenderKeyState(
+			keyhelper.GenerateSenderKeyID(), 0,
+			keyhelper.GenerateSenderKey(),
+			signingKey,
+		)
+		b.senderKeyStore.StoreSenderKey(senderKeyName, senderKeyRecord)
+	}
+
+	// Get the senderkey state.
+	state, err := senderKeyRecord.SenderKeyState()
+	if err != nil {
+		return nil, err
+	}
+
+	// Create the group message to return.
+	senderKeyDistributionMessage := protocol.NewSenderKeyDistributionMessage(
+		state.KeyID(),
+		state.SenderChainKey().Iteration(),
+		state.SenderChainKey().Seed(),
+		state.SigningKey().PublicKey(),
+		b.serializer.SenderKeyDistributionMessage,
+	)
+
+	return senderKeyDistributionMessage, nil
+}