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/proto/codec/padded_intermediate.go

@@ -0,0 +1,106 @@
+package codec
+
+import (
+	"io"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
+)
+
+// PaddedIntermediateClientStart is starting bytes sent by client in Padded intermediate mode.
+//
+// Note that server does not respond with it.
+var PaddedIntermediateClientStart = [4]byte{0xdd, 0xdd, 0xdd, 0xdd}
+
+// PaddedIntermediate is intermediate MTProto transport.
+//
+// See https://core.telegram.org/mtproto/mtproto-transports#padded-intermediate
+type PaddedIntermediate struct{}
+
+var (
+	_ TaggedCodec = PaddedIntermediate{}
+)
+
+// WriteHeader sends protocol tag.
+func (i PaddedIntermediate) WriteHeader(w io.Writer) error {
+	if _, err := w.Write(PaddedIntermediateClientStart[:]); err != nil {
+		return errors.Wrap(err, "write padded intermediate header")
+	}
+
+	return nil
+}
+
+// ReadHeader reads protocol tag.
+func (i PaddedIntermediate) ReadHeader(r io.Reader) error {
+	var b [4]byte
+	if _, err := io.ReadFull(r, b[:]); err != nil {
+		return errors.Wrap(err, "read padded intermediate header")
+	}
+
+	if b != PaddedIntermediateClientStart {
+		return ErrProtocolHeaderMismatch
+	}
+
+	return nil
+}
+
+// ObfuscatedTag returns protocol tag for obfuscation.
+func (i PaddedIntermediate) ObfuscatedTag() [4]byte {
+	return PaddedIntermediateClientStart
+}
+
+// Write encode to writer message from given buffer.
+func (i PaddedIntermediate) Write(w io.Writer, b *bin.Buffer) error {
+	if err := checkOutgoingMessage(b); err != nil {
+		return err
+	}
+
+	if err := checkAlign(b, 4); err != nil {
+		return err
+	}
+
+	if err := writePaddedIntermediate(crypto.DefaultRand(), w, b); err != nil {
+		return errors.Wrap(err, "write padded intermediate")
+	}
+
+	return nil
+}
+
+// Read fills buffer with received message.
+func (i PaddedIntermediate) Read(r io.Reader, b *bin.Buffer) error {
+	if err := readPaddedIntermediate(r, b); err != nil {
+		return errors.Wrap(err, "read padded intermediate")
+	}
+
+	return checkProtocolError(b)
+}
+
+func writePaddedIntermediate(randSource io.Reader, w io.Writer, b *bin.Buffer) error {
+	length := b.Len()
+
+	b.Expand(4)
+	defer func() {
+		b.Buf = b.Buf[:length]
+	}()
+
+	_, err := io.ReadFull(randSource, b.Buf[length:length+4])
+	if err != nil {
+		return err
+	}
+	n := int(b.Buf[length-1]) % 4
+	b.Buf = b.Buf[:length+n]
+
+	return writeIntermediate(w, b)
+}
+
+func readPaddedIntermediate(r io.Reader, b *bin.Buffer) error {
+	if err := readIntermediate(r, b, true); err != nil {
+		return err
+	}
+
+	padding := b.Len() % 4
+	b.Buf = b.Buf[:b.Len()-padding]
+	return nil
+}