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/exchange/flow_test.go

@@ -0,0 +1,114 @@
+package exchange
+
+import (
+	"context"
+	"crypto/rsa"
+	"fmt"
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zaptest"
+	"golang.org/x/sync/errgroup"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tdsync"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/testutil"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/transport"
+)
+
+func testExchange(rsaPad bool) func(t *testing.T) {
+	return func(t *testing.T) {
+		a := require.New(t)
+		log := zaptest.NewLogger(t)
+
+		dc := 2
+		reader := rand.New(rand.NewSource(1))
+		key, err := rsa.GenerateKey(reader, crypto.RSAKeyBits)
+		a.NoError(err)
+		privateKey := PrivateKey{
+			RSA: key,
+		}
+
+		i := transport.Intermediate
+		client, server := i.Pipe()
+
+		ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+		defer cancel()
+
+		g := tdsync.NewCancellableGroup(ctx)
+		g.Go(func(ctx context.Context) error {
+			_, err := NewExchanger(client, dc).
+				WithLogger(log.Named("client")).
+				WithRand(reader).
+				Client([]PublicKey{privateKey.Public()}).
+				Run(ctx)
+			return err
+		})
+
+		g.Go(func(ctx context.Context) error {
+			_, err := NewExchanger(server, dc).
+				WithLogger(log.Named("server")).
+				WithRand(reader).
+				Server(privateKey).
+				Run(ctx)
+			return err
+		})
+
+		a.NoError(g.Wait())
+	}
+}
+
+func TestExchange(t *testing.T) {
+	t.Run("PQInnerData", testExchange(false))
+	t.Run("PQInnerDataDC", testExchange(true))
+}
+
+func TestExchangeCorpus(t *testing.T) {
+	privateKey := PrivateKey{
+		RSA: testutil.RSAPrivateKey(),
+	}
+
+	for i, seed := range []string{
+		"\xef\x00\x04",
+	} {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			dc := 2
+			reader := testutil.Rand([]byte(seed))
+			log := zaptest.NewLogger(t)
+
+			i := transport.Intermediate
+			client, server := i.Pipe()
+
+			ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+			defer cancel()
+
+			g, gctx := errgroup.WithContext(ctx)
+			g.Go(func() error {
+				_, err := NewExchanger(client, dc).
+					WithLogger(log.Named("client")).
+					WithRand(reader).
+					Client([]PublicKey{privateKey.Public()}).
+					Run(gctx)
+				if err != nil {
+					cancel()
+				}
+				return err
+			})
+			g.Go(func() error {
+				_, err := NewExchanger(server, dc).
+					WithLogger(log.Named("server")).
+					WithRand(reader).
+					Server(privateKey).
+					Run(gctx)
+				if err != nil {
+					cancel()
+				}
+				return err
+			})
+
+			require.NoError(t, g.Wait())
+		})
+	}
+}