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/crypto/keys_old.go

@@ -0,0 +1,99 @@
+package crypto
+
+import (
+	"crypto/sha1" // #nosec G505
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+)
+
+// sha1a returns sha1_a value.
+//
+// sha1_a = SHA1 (msg_key + substr (auth_key, x, 32));
+func sha1a(r []byte, authKey Key, msgKey bin.Int128, x int) []byte {
+	h := sha1.New() // #nosec G401
+
+	_, _ = h.Write(msgKey[:])
+	_, _ = h.Write(authKey[x : x+32])
+
+	return h.Sum(r)
+}
+
+// sha1b returns sha1_b value.
+//
+// sha1_b = SHA1 (substr (auth_key, 32+x, 16) + msg_key + substr (auth_key, 48+x, 16));
+func sha1b(r []byte, authKey Key, msgKey bin.Int128, x int) []byte {
+	h := sha1.New() // #nosec G401
+
+	_, _ = h.Write(authKey[32+x : 32+x+16])
+	_, _ = h.Write(msgKey[:])
+	_, _ = h.Write(authKey[48+x : 48+x+16])
+
+	return h.Sum(r)
+}
+
+// sha1c returns sha1_c value.
+//
+// sha1_c = SHA1 (substr (auth_key, 64+x, 32) + msg_key);
+func sha1c(r []byte, authKey Key, msgKey bin.Int128, x int) []byte {
+	h := sha1.New() // #nosec G401
+
+	_, _ = h.Write(authKey[64+x : 64+x+32])
+	_, _ = h.Write(msgKey[:])
+
+	return h.Sum(r)
+}
+
+// sha1d returns sha1_d value.
+//
+// sha1_d = SHA1 (msg_key + substr (auth_key, 96+x, 32));
+func sha1d(r []byte, authKey Key, msgKey bin.Int128, x int) []byte {
+	h := sha1.New() // #nosec G401
+
+	_, _ = h.Write(msgKey[:])
+	_, _ = h.Write(authKey[96+x : 96+x+32])
+
+	return h.Sum(r)
+}
+
+// OldKeys returns (aes_key, aes_iv) pair for AES-IGE.
+//
+// See https://core.telegram.org/mtproto/description_v1#defining-aes-key-and-initialization-vector
+//
+// Example:
+//
+//	key, iv := crypto.OldKeys(authKey, messageKey, crypto.Client)
+//	cipher, err := aes.NewCipher(key[:])
+//	if err != nil {
+//		return nil, err
+//	}
+//	encryptor := ige.NewIGEEncrypter(cipher, iv[:])
+//
+// Warning: MTProto 1.0 is deprecated.
+func OldKeys(authKey Key, msgKey bin.Int128, mode Side) (key, iv bin.Int256) {
+	x := getX(mode)
+
+	aesKey := func(sha1a, sha1b, sha1c []byte) (v bin.Int256) {
+		// aes_key = substr (sha1_a, 0, 8) + substr (sha1_b, 8, 12) + substr (sha1_c, 4, 12);
+		n := copy(v[:], sha1a[:8])
+		n += copy(v[n:], sha1b[8:8+12])
+		copy(v[n:], sha1c[4:4+12])
+		return v
+	}
+	aesIV := func(sha1a, sha1b, sha1c, sha1d []byte) (v bin.Int256) {
+		// aes_iv = substr(sha1_a, 8, 12) + substr(sha1_b, 0, 8) + substr(sha1_c, 16, 4) + substr(sha1_d, 0, 8);
+		n := copy(v[:], sha1a[8:8+12])
+		n += copy(v[n:], sha1b[:8])
+		n += copy(v[n:], sha1c[16:16+4])
+		copy(v[n:], sha1d[:8])
+		return v
+	}
+
+	r := make([]byte, sha1.Size*4)
+
+	a := sha1a(r[0:0], authKey, msgKey, x)
+	b := sha1b(r[sha1.Size:sha1.Size], authKey, msgKey, x)
+	c := sha1c(r[2*sha1.Size:2*sha1.Size], authKey, msgKey, x)
+	d := sha1d(r[3*sha1.Size:3*sha1.Size], authKey, msgKey, x)
+
+	return aesKey(a, b, c), aesIV(a, b, c, d)
+}