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/mtproxy/faketls/faketls.go

@@ -0,0 +1,112 @@
+package faketls
+
+import (
+	"bytes"
+	"io"
+	"sync"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/clock"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/mtproxy"
+)
+
+// FakeTLS implements FakeTLS obfuscation protocol.
+type FakeTLS struct {
+	rand  io.Reader
+	clock clock.Clock
+	conn  io.ReadWriter
+
+	version     [2]byte
+	firstPacket bool
+
+	readBuf    bytes.Buffer
+	readBufMux sync.Mutex
+}
+
+// NewFakeTLS creates new FakeTLS.
+func NewFakeTLS(r io.Reader, conn io.ReadWriter) *FakeTLS {
+	return &FakeTLS{
+		rand:    r,
+		clock:   clock.System,
+		conn:    conn,
+		version: Version12Bytes,
+		readBuf: bytes.Buffer{},
+	}
+}
+
+// Handshake performs FakeTLS handshake.
+func (o *FakeTLS) Handshake(protocol [4]byte, dc int, s mtproxy.Secret) error {
+	o.readBufMux.Lock()
+	o.readBuf.Reset()
+	o.readBufMux.Unlock()
+
+	var sessionID [32]byte
+	if _, err := o.rand.Read(sessionID[:]); err != nil {
+		return errors.Wrap(err, "generate sessionID")
+	}
+
+	clientDigest, err := writeClientHello(o.conn, o.clock, sessionID, s.CloakHost, s.Secret)
+	if err != nil {
+		return errors.Wrap(err, "send ClientHello")
+	}
+
+	if err := readServerHello(o.conn, clientDigest, s.Secret); err != nil {
+		return errors.Wrap(err, "receive ServerHello")
+	}
+	return nil
+}
+
+// Write implements io.Writer.
+func (o *FakeTLS) Write(b []byte) (n int, err error) {
+	// Some proxies require sending first packet with RecordTypeChangeCipherSpec.
+	//
+	// See https://github.com/tdlib/td/blob/master/td/mtproto/TcpTransport.cpp#L266.
+	if !o.firstPacket {
+		_, err = writeRecord(o.conn, record{
+			Type:    RecordTypeChangeCipherSpec,
+			Version: o.version,
+			Data:    []byte("\x01"),
+		})
+		if err != nil {
+			return 0, errors.Wrap(err, "write first TLS packet")
+		}
+		o.firstPacket = true
+	}
+	n, err = writeRecord(o.conn, record{
+		Type:    RecordTypeApplication,
+		Version: o.version,
+		Data:    b,
+	})
+	if err != nil {
+		return 0, errors.Wrap(err, "write TLS record")
+	}
+	return
+}
+
+// Read implements io.Reader.
+func (o *FakeTLS) Read(b []byte) (n int, err error) {
+	o.readBufMux.Lock()
+	defer o.readBufMux.Unlock()
+
+	if o.readBuf.Len() > 0 {
+		return o.readBuf.Read(b)
+	}
+
+	rec, err := readRecord(o.conn)
+	if err != nil {
+		return 0, errors.Wrap(err, "read TLS record")
+	}
+
+	switch rec.Type {
+	case RecordTypeChangeCipherSpec:
+	case RecordTypeApplication:
+	case RecordTypeHandshake:
+		return 0, errors.New("unexpected record type handshake")
+	default:
+		return 0, errors.Errorf("unsupported record type %v", rec.Type)
+	}
+	o.readBuf.Write(rec.Data)
+
+	return o.readBuf.Read(b)
+}