3 files changed, 160 insertions, 0 deletions
diff --git a/vendor/go.mau.fi/libsignal/groups/ratchet/Doc.go b/vendor/go.mau.fi/libsignal/groups/ratchet/Doc.go
new file mode 100644
index 00000000..6d374465
--- /dev/null
+++ b/vendor/go.mau.fi/libsignal/groups/ratchet/Doc.go
@@ -0,0 +1,3 @@
+// Package ratchet provides the methods necessary to establish a ratchet
+// session for group messaging.
+package ratchet
diff --git a/vendor/go.mau.fi/libsignal/groups/ratchet/SenderChainKey.go b/vendor/go.mau.fi/libsignal/groups/ratchet/SenderChainKey.go
new file mode 100644
index 00000000..a9530143
--- /dev/null
+++ b/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)
+}
diff --git a/vendor/go.mau.fi/libsignal/groups/ratchet/SenderMessageKey.go b/vendor/go.mau.fi/libsignal/groups/ratchet/SenderMessageKey.go
new file mode 100644
index 00000000..724059f2
--- /dev/null
+++ b/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
+}