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/session/tdesktop/key_data_test.go

@@ -0,0 +1,76 @@
+package tdesktop
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Test_readKeyData(t *testing.T) {
+	a := require.New(t)
+	buf := bytes.Buffer{}
+	var (
+		passcode []byte
+		salt     = make([]byte, 32)
+		info     = []byte{
+			16, 0, 0, 0,
+			0, 0, 0, 1,
+			0, 0, 0, 0,
+			0, 0, 0, 0,
+		}
+		passcodeKey = createLocalKey(passcode, salt)
+		localKey    = createLocalKey([]byte("aboba"), salt)
+
+		// Store buffer offsets to test EOF errors
+		cuts = []int{0}
+	)
+
+	// Write salt.
+	a.NoError(writeArray(&buf, salt, binary.BigEndian))
+	cuts = append(cuts, buf.Len())
+
+	var keyInnerData []byte
+	{
+		b := bytes.Buffer{}
+		// Pad to 16 bytes.
+		data := make([]byte, 272-4)
+		copy(data, localKey[:])
+		a.NoError(writeArray(&b, data, binary.LittleEndian))
+		keyInnerData = b.Bytes()
+	}
+
+	keyEncrypted, err := encryptLocal(keyInnerData, passcodeKey)
+	a.NoError(err)
+	a.NoError(writeArray(&buf, keyEncrypted, binary.BigEndian))
+	cuts = append(cuts, buf.Len())
+
+	infoEncrypted, err := encryptLocal(info, localKey)
+	a.NoError(err)
+	a.NoError(writeArray(&buf, infoEncrypted, binary.BigEndian))
+	// Do not store last cut, because it is valid.
+
+	fileData := buf.Bytes()
+	t.Run("OK", func(t *testing.T) {
+		a := require.New(t)
+
+		kdata, err := readKeyData(&tdesktopFile{
+			data: fileData,
+		}, passcode)
+		a.NoError(err)
+		a.Equal(localKey, kdata.localKey)
+		a.Len(kdata.accountsIDx, 1)
+	})
+	for _, cut := range cuts {
+		t.Run(fmt.Sprintf("EOFAfter%d", cut), func(t *testing.T) {
+			a := require.New(t)
+
+			_, err := readKeyData(&tdesktopFile{
+				data: fileData[:cut],
+			}, passcode)
+			a.Error(err)
+		})
+	}
+}