refactor to mautrix 0.17.x; update deps

vendor/maunium.net/go/mautrix/crypto/goolm/pk/encryption.go

@@ -0,0 +1,49 @@
+package pk
+
+import (
+	"encoding/base64"
+
+	"maunium.net/go/mautrix/id"
+
+	"maunium.net/go/mautrix/crypto/goolm"
+	"maunium.net/go/mautrix/crypto/goolm/cipher"
+	"maunium.net/go/mautrix/crypto/goolm/crypto"
+)
+
+// Encryption is used to encrypt pk messages
+type Encryption struct {
+	RecipientKey crypto.Curve25519PublicKey `json:"recipient_key"`
+}
+
+// NewEncryption returns a new Encryption with the base64 encoded public key of the recipient
+func NewEncryption(pubKey id.Curve25519) (*Encryption, error) {
+	pubKeyDecoded, err := base64.RawStdEncoding.DecodeString(string(pubKey))
+	if err != nil {
+		return nil, err
+	}
+	return &Encryption{
+		RecipientKey: pubKeyDecoded,
+	}, nil
+}
+
+// Encrypt encrypts the plaintext with the privateKey and returns the ciphertext and base64 encoded MAC.
+func (e Encryption) Encrypt(plaintext []byte, privateKey crypto.Curve25519PrivateKey) (ciphertext, mac []byte, err error) {
+	keyPair, err := crypto.Curve25519GenerateFromPrivate(privateKey)
+	if err != nil {
+		return nil, nil, err
+	}
+	sharedSecret, err := keyPair.SharedSecret(e.RecipientKey)
+	if err != nil {
+		return nil, nil, err
+	}
+	cipher := cipher.NewAESSHA256(nil)
+	ciphertext, err = cipher.Encrypt(sharedSecret, plaintext)
+	if err != nil {
+		return nil, nil, err
+	}
+	mac, err = cipher.MAC(sharedSecret, ciphertext)
+	if err != nil {
+		return nil, nil, err
+	}
+	return ciphertext, goolm.Base64Encode(mac), nil
+}