Add dependencies/vendor (whatsapp)

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

@@ -0,0 +1,68 @@
+package ratchet
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+)
+
+var messageKeySeed = []byte{0x01}
+var chainKeySeed = []byte{0x02}
+
+// NewSenderChainKey will return a new SenderChainKey.
+func NewSenderChainKey(iteration uint32, chainKey []byte) *SenderChainKey {
+	return &SenderChainKey{
+		iteration: iteration,
+		chainKey:  chainKey,
+	}
+}
+
+// NewSenderChainKeyFromStruct will return a new chain key object from the
+// given serializeable structure.
+func NewSenderChainKeyFromStruct(structure *SenderChainKeyStructure) *SenderChainKey {
+	return &SenderChainKey{
+		iteration: structure.Iteration,
+		chainKey:  structure.ChainKey,
+	}
+}
+
+// NewStructFromSenderChainKeys returns a serializeable structure of chain keys.
+func NewStructFromSenderChainKey(key *SenderChainKey) *SenderChainKeyStructure {
+	return &SenderChainKeyStructure{
+		Iteration: key.iteration,
+		ChainKey:  key.chainKey,
+	}
+}
+
+// SenderChainKeyStructure is a serializeable structure of SenderChainKeys.
+type SenderChainKeyStructure struct {
+	Iteration uint32
+	ChainKey  []byte
+}
+
+type SenderChainKey struct {
+	iteration uint32
+	chainKey  []byte
+}
+
+func (k *SenderChainKey) Iteration() uint32 {
+	return k.iteration
+}
+
+func (k *SenderChainKey) SenderMessageKey() (*SenderMessageKey, error) {
+	return NewSenderMessageKey(k.iteration, k.getDerivative(messageKeySeed, k.chainKey))
+}
+
+func (k *SenderChainKey) Next() *SenderChainKey {
+	return NewSenderChainKey(k.iteration+1, k.getDerivative(chainKeySeed, k.chainKey))
+}
+
+func (k *SenderChainKey) Seed() []byte {
+	return k.chainKey
+}
+
+func (k *SenderChainKey) getDerivative(seed []byte, key []byte) []byte {
+	mac := hmac.New(sha256.New, key[:])
+	mac.Write(seed)
+
+	return mac.Sum(nil)
+}