move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/crypto/cipher_decrypt_test.go

@@ -0,0 +1,87 @@
+package crypto
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/testutil"
+)
+
+func TestDecrypt(t *testing.T) {
+	// Test vector from grammers.
+	c := NewClientCipher(testutil.ZeroRand{})
+	var msg EncryptedMessage
+	b := &bin.Buffer{Buf: []byte{
+		122, 113, 131, 194, 193, 14, 79, 77, 249, 69, 250, 154, 154, 189, 53, 231, 195, 132,
+		11, 97, 240, 69, 48, 79, 57, 103, 76, 25, 192, 226, 9, 120, 79, 80, 246, 34, 106, 7,
+		53, 41, 214, 117, 201, 44, 191, 11, 250, 140, 153, 167, 155, 63, 57, 199, 42, 93, 154,
+		2, 109, 67, 26, 183, 64, 124, 160, 78, 204, 85, 24, 125, 108, 69, 241, 120, 113, 82,
+		78, 221, 144, 206, 160, 46, 215, 40, 225, 77, 124, 177, 138, 234, 42, 99, 97, 88, 240,
+		148, 89, 169, 67, 119, 16, 216, 148, 199, 159, 54, 140, 78, 129, 100, 183, 100, 126,
+		169, 134, 18, 174, 254, 148, 44, 93, 146, 18, 26, 203, 141, 176, 45, 204, 206, 182,
+		109, 15, 135, 32, 172, 18, 160, 109, 176, 88, 43, 253, 149, 91, 227, 79, 54, 81, 24,
+		227, 186, 184, 205, 8, 12, 230, 180, 91, 40, 234, 197, 109, 205, 42, 41, 55, 78,
+	}}
+	if err := msg.Decode(b); err != nil {
+		t.Fatal(err)
+	}
+	plaintext, err := c.decryptMessage(testAuthKey, &msg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expectedPlaintext := []byte{
+		252, 130, 106, 2, 36, 139, 40, 253, 96, 242, 196, 130, 36, 67, 173, 104, 1, 240, 193,
+		194, 145, 139, 48, 94, 2, 0, 0, 0, 88, 0, 0, 0, 220, 248, 241, 115, 2, 0, 0, 0, 1, 168,
+		193, 194, 145, 139, 48, 94, 1, 0, 0, 0, 28, 0, 0, 0, 8, 9, 194, 158, 196, 253, 51, 173,
+		145, 139, 48, 94, 24, 168, 142, 166, 7, 238, 88, 22, 252, 130, 106, 2, 36, 139, 40,
+		253, 1, 204, 193, 194, 145, 139, 48, 94, 2, 0, 0, 0, 20, 0, 0, 0, 197, 115, 119, 52,
+		196, 253, 51, 173, 145, 139, 48, 94, 100, 8, 48, 0, 0, 0, 0, 0, 252, 230, 103, 4, 163,
+		205, 142, 233, 208, 174, 111, 171, 103, 44, 96, 192, 74, 63, 31, 212, 73, 14, 81, 246,
+	}
+	if !bytes.Equal(expectedPlaintext, plaintext) {
+		t.Error("mismatch")
+	}
+}
+
+func TestCipher_Decrypt(t *testing.T) {
+	var key AuthKey
+	if _, err := io.ReadFull(testutil.Rand([]byte{10}), key.Value[:]); err != nil {
+		t.Fatal(err)
+	}
+
+	c := NewClientCipher(testutil.ZeroRand{})
+	s := NewServerCipher(testutil.ZeroRand{})
+	tests := []struct {
+		name      string
+		data      []byte
+		dataLen   int
+		expectErr bool
+	}{
+		{"NegativeLength", []byte{1, 2, 3, 4}, -1, true},
+		{"NoPadBy4", []byte{1, 2, 3}, 3, true},
+		{"Good", bytes.Repeat([]byte{1, 2, 3, 4}, 4), 16, false},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			a := require.New(t)
+			b := bin.Buffer{}
+			data := EncryptedMessageData{
+				MessageDataLen:         int32(test.dataLen),
+				MessageDataWithPadding: test.data,
+			}
+			a.NoError(s.Encrypt(key, data, &b))
+
+			_, err := c.DecryptFromBuffer(key, &b)
+			if test.expectErr {
+				a.Error(err)
+				return
+			}
+			a.NoError(err)
+		})
+	}
+}