refactor to mautrix 0.17.x; update deps

vendor/maunium.net/go/mautrix/crypto/goolm/sas/main.go

@@ -0,0 +1,76 @@
+// sas provides the means to do SAS between keys
+package sas
+
+import (
+	"io"
+
+	"maunium.net/go/mautrix/crypto/goolm"
+	"maunium.net/go/mautrix/crypto/goolm/crypto"
+)
+
+// SAS contains the key pair and secret for SAS.
+type SAS struct {
+	KeyPair crypto.Curve25519KeyPair
+	Secret  []byte
+}
+
+// New creates a new SAS with a new key pair.
+func New() (*SAS, error) {
+	kp, err := crypto.Curve25519GenerateKey(nil)
+	if err != nil {
+		return nil, err
+	}
+	s := &SAS{
+		KeyPair: kp,
+	}
+	return s, nil
+}
+
+// GetPubkey returns the public key of the key pair base64 encoded
+func (s SAS) GetPubkey() []byte {
+	return goolm.Base64Encode(s.KeyPair.PublicKey)
+}
+
+// SetTheirKey sets the key of the other party and computes the shared secret.
+func (s *SAS) SetTheirKey(key []byte) error {
+	keyDecoded, err := goolm.Base64Decode(key)
+	if err != nil {
+		return err
+	}
+	sharedSecret, err := s.KeyPair.SharedSecret(keyDecoded)
+	if err != nil {
+		return err
+	}
+	s.Secret = sharedSecret
+	return nil
+}
+
+// GenerateBytes creates length bytes from the shared secret and info.
+func (s SAS) GenerateBytes(info []byte, length uint) ([]byte, error) {
+	byteReader := crypto.HKDFSHA256(s.Secret, nil, info)
+	output := make([]byte, length)
+	if _, err := io.ReadFull(byteReader, output); err != nil {
+		return nil, err
+	}
+	return output, nil
+}
+
+// calculateMAC returns a base64 encoded MAC of input.
+func (s *SAS) calculateMAC(input, info []byte, length uint) ([]byte, error) {
+	key, err := s.GenerateBytes(info, length)
+	if err != nil {
+		return nil, err
+	}
+	mac := crypto.HMACSHA256(key, input)
+	return goolm.Base64Encode(mac), nil
+}
+
+// CalculateMACFixes returns a base64 encoded, 32 byte long MAC of input.
+func (s SAS) CalculateMAC(input, info []byte) ([]byte, error) {
+	return s.calculateMAC(input, info, 32)
+}
+
+// CalculateMACLongKDF returns a base64 encoded, 256 byte long MAC of input.
+func (s SAS) CalculateMACLongKDF(input, info []byte) ([]byte, error) {
+	return s.calculateMAC(input, info, 256)
+}