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/client_hello.go

@@ -0,0 +1,124 @@
+package faketls
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/binary"
+	"io"
+
+	"github.com/go-faster/errors"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/clock"
+)
+
+const clientHelloLength = 517
+
+func createClientHello(b *bin.Buffer, sessionID [32]byte, domain string, key [32]byte) (randomOffset int) {
+	S := func(s string) {
+		b.Buf = append(b.Buf, s...)
+	}
+	Z := func(n int) {
+		randomOffset = len(b.Buf)
+		b.Expand(n)
+	}
+	G := func(_ int) {
+		b.Expand(0)
+	}
+	R := func() {
+		b.Buf = append(b.Buf, sessionID[:]...)
+	}
+	D := func() {
+		b.Buf = append(b.Buf, domain...)
+	}
+	K := func() {
+		b.Buf = append(b.Buf, key[:]...)
+	}
+	var stack []int
+	Open := func() {
+		stack = append(stack, b.Len())
+		b.Expand(2)
+	}
+	Close := func() {
+		lastIdx := len(stack) - 1
+		s := stack[lastIdx]
+		stack = stack[:lastIdx]
+
+		length := b.Len() - (s + 2)
+		binary.BigEndian.PutUint16(b.Buf[s:], uint16(length))
+	}
+
+	S("\x16\x03\x01\x02\x00\x01\x00\x01\xfc\x03\x03")
+	Z(32)
+	S("\x20")
+	R()
+	S("\x00\x20")
+	G(0)
+	S("\x13\x01\x13\x02\x13\x03\xc0\x2b\xc0\x2f\xc0\x2c\xc0\x30\xcc\xa9" +
+		"\xcc\xa8\xc0\x13\xc0\x14\x00\x9c\x00\x9d\x00\x2f\x00\x35\x01\x00" +
+		"\x01\x93")
+	G(2)
+	S("\x00\x00\x00\x00")
+	Open()
+	Open()
+	S("\x00")
+	Open()
+	D()
+	Close()
+	Close()
+	Close()
+	S("\x00\x17\x00\x00\xff\x01\x00\x01\x00\x00\x0a\x00\x0a\x00\x08")
+	G(4)
+	S("\x00\x1d\x00\x17\x00\x18\x00\x0b\x00\x02\x01\x00\x00\x23\x00\x00" +
+		"\x00\x10\x00\x0e\x00\x0c\x02\x68\x32\x08\x68\x74\x74\x70\x2f\x31" +
+		"\x2e\x31\x00\x05\x00\x05\x01\x00\x00\x00\x00\x00\x0d\x00\x12\x00" +
+		"\x10\x04\x03\x08\x04\x04\x01\x05\x03\x08\x05\x05\x01\x08\x06\x06" +
+		"\x01\x00\x12\x00\x00\x00\x33\x00\x2b\x00\x29")
+	G(4)
+	S("\x00\x01\x00\x00\x1d\x00\x20")
+	K()
+	S("\x00\x2d\x00\x02\x01\x01\x00\x2b\x00\x0b\x0a")
+	G(6)
+	S("\x03\x04\x03\x03\x03\x02\x03\x01\x00\x1b\x00\x03\x02\x00\x02")
+	G(3)
+	S("\x00\x01\x00\x00\x15")
+
+	if pad := clientHelloLength - b.Len(); pad > 0 {
+		b.Expand(pad)
+	}
+	return randomOffset
+}
+
+// writeClientHello writes faketls ClientHello.
+//
+// See https://tools.ietf.org/html/rfc5246#section-7.4.1.1.
+func writeClientHello(
+	w io.Writer,
+	now clock.Clock,
+	sessionID [32]byte,
+	domain string,
+	secret []byte,
+) (r [32]byte, err error) {
+	b := &bin.Buffer{
+		Buf: make([]byte, 0, 576),
+	}
+	randomOffset := createClientHello(b, sessionID, domain, [32]byte{})
+
+	// https://github.com/tdlib/td/blob/27d3fdd09d90f6b77ecbcce50b1e86dc4b3dd366/td/mtproto/TlsInit.cpp#L380-L384
+	mac := hmac.New(sha256.New, secret)
+	if _, err := mac.Write(b.Buf); err != nil {
+		return [32]byte{}, errors.Wrap(err, "hmac write")
+	}
+
+	s := mac.Sum(nil)
+	copy(b.Buf[randomOffset:randomOffset+32], s)
+	// Overwrite last 4 bytes using final := original ^ timestamp.
+	old := binary.LittleEndian.Uint32(b.Buf[randomOffset+28 : randomOffset+32])
+	old ^= uint32(now.Now().Unix())
+	binary.LittleEndian.PutUint32(b.Buf[randomOffset+28:randomOffset+32], old)
+
+	// Copy ClientRandom for later use.
+	copy(r[:], b.Buf[randomOffset:randomOffset+32])
+	_, err = w.Write(b.Buf)
+	return r, err
+}