Add dependencies/vendor (whatsapp)

vendor/go.mau.fi/libsignal/groups/ratchet/SenderMessageKey.go

@@ -0,0 +1,89 @@
+package ratchet
+
+import (
+	"go.mau.fi/libsignal/kdf"
+	"go.mau.fi/libsignal/util/bytehelper"
+)
+
+// KdfInfo is optional bytes to include in deriving secrets with KDF.
+const KdfInfo string = "WhisperGroup"
+
+// NewSenderMessageKey will return a new sender message key using the given
+// iteration and seed.
+func NewSenderMessageKey(iteration uint32, seed []byte) (*SenderMessageKey, error) {
+	derivative, err := kdf.DeriveSecrets(seed, nil, []byte(KdfInfo), 48)
+	if err != nil {
+		return nil, err
+	}
+
+	// Split our derived secrets into 2 parts
+	parts := bytehelper.Split(derivative, 16, 32)
+
+	// Build the message key.
+	senderKeyMessage := &SenderMessageKey{
+		iteration: iteration,
+		seed:      seed,
+		iv:        parts[0],
+		cipherKey: parts[1],
+	}
+
+	return senderKeyMessage, nil
+}
+
+// NewSenderMessageKeyFromStruct will return a new message key object from the
+// given serializeable structure.
+func NewSenderMessageKeyFromStruct(structure *SenderMessageKeyStructure) *SenderMessageKey {
+	return &SenderMessageKey{
+		iteration: structure.Iteration,
+		iv:        structure.IV,
+		cipherKey: structure.CipherKey,
+		seed:      structure.Seed,
+	}
+}
+
+// NewStructFromSenderMessageKey returns a serializeable structure of message keys.
+func NewStructFromSenderMessageKey(key *SenderMessageKey) *SenderMessageKeyStructure {
+	return &SenderMessageKeyStructure{
+		CipherKey: key.cipherKey,
+		Iteration: key.iteration,
+		IV:        key.iv,
+		Seed:      key.seed,
+	}
+}
+
+// SenderMessageKeyStructure is a serializeable structure of SenderMessageKeys.
+type SenderMessageKeyStructure struct {
+	Iteration uint32
+	IV        []byte
+	CipherKey []byte
+	Seed      []byte
+}
+
+// SenderMessageKey is a structure for sender message keys used in group
+// messaging.
+type SenderMessageKey struct {
+	iteration uint32
+	iv        []byte
+	cipherKey []byte
+	seed      []byte
+}
+
+// Iteration will return the sender message key's iteration.
+func (k *SenderMessageKey) Iteration() uint32 {
+	return k.iteration
+}
+
+// Iv will return the sender message key's initialization vector.
+func (k *SenderMessageKey) Iv() []byte {
+	return k.iv
+}
+
+// CipherKey will return the key in bytes.
+func (k *SenderMessageKey) CipherKey() []byte {
+	return k.cipherKey
+}
+
+// Seed will return the sender message key's seed.
+func (k *SenderMessageKey) Seed() []byte {
+	return k.seed
+}