Add background update for middle proxy

mtproto/rpc/handshake_request.go

@@ -0,0 +1,7 @@
+package rpc
+
+import "github.com/9seconds/mtg/mtproto"
+
+var HandshakeRequest = append(mtproto.TagHandshake,
+	append(mtproto.HandshakeFlags,
+		append(mtproto.HandshakeSenderPID, mtproto.HandshakePeerPID...)...)...)

mtproto/rpc/handshake_response.go

@@ -0,0 +1,55 @@
+package rpc
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/9seconds/mtg/mtproto"
+)
+
+type HandshakeResponse struct {
+	Type      []byte
+	Flags     []byte
+	SenderPID []byte
+	PeerPID   []byte
+}
+
+// Bytes returns a serialized handshake response.
+func (r *HandshakeResponse) Bytes() []byte {
+	buf := &bytes.Buffer{}
+
+	buf.Write(r.Type)      // nolint: gosec
+	buf.Write(r.Flags)     // nolint: gosec
+	buf.Write(r.SenderPID) // nolint: gosec
+	buf.Write(r.PeerPID)   // nolint: gosec
+
+	return buf.Bytes()
+}
+
+// Valid checks that handshake response compliments request.
+func (r *HandshakeResponse) Valid() error {
+	if !bytes.Equal(r.Type, mtproto.TagHandshake) {
+		return errors.New("Unexpected handshake tag")
+	}
+	if !bytes.Equal(r.PeerPID, mtproto.HandshakeSenderPID) {
+		return errors.New("Incorrect sender PID")
+	}
+
+	return nil
+}
+
+// NewHandshakeResponse constructs new handshake response from the given
+// data.
+func NewHandshakeResponse(data []byte) (*HandshakeResponse, error) {
+	if len(data) != 32 {
+		return nil, fmt.Errorf("Incorrect handshake response length %d", len(data))
+	}
+
+	return &HandshakeResponse{
+		Type:      data[:4],
+		Flags:     data[4:8],
+		SenderPID: data[8:20],
+		PeerPID:   data[20:],
+	}, nil
+}

mtproto/rpc/nonce_request.go

@@ -0,0 +1,51 @@
+package rpc
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"time"
+
+	"github.com/9seconds/mtg/mtproto"
+)
+
+type NonceRequest struct {
+	KeySelector []byte
+	CryptoTS    []byte
+	Nonce       []byte
+}
+
+// Bytes returns serialized nonce request.
+func (r *NonceRequest) Bytes() []byte {
+	buf := &bytes.Buffer{}
+
+	buf.Write(mtproto.TagNonce)       // nolint: gosec
+	buf.Write(r.KeySelector)          // nolint: gosec
+	buf.Write(mtproto.NonceCryptoAES) // nolint: gosec
+	buf.Write(r.CryptoTS)             // nolint: gosec
+	buf.Write(r.Nonce)                // nolint: gosec
+
+	return buf.Bytes()
+}
+
+// NewNonceRequest builds new none request based on proxy secret.
+func NewNonceRequest(proxySecret []byte) (*NonceRequest, error) {
+	nonce := make([]byte, 16)
+	keySelector := make([]byte, 4)
+	cryptoTS := make([]byte, 4)
+
+	if _, err := rand.Read(nonce); err != nil {
+		return nil, fmt.Errorf("cannot generate nonce: %w", err)
+	}
+	copy(keySelector, proxySecret)
+
+	timestamp := time.Now().Truncate(time.Second).Unix() % 4294967296 // 256 ^ 4 - do not know how to name
+	binary.LittleEndian.PutUint32(cryptoTS, uint32(timestamp))
+
+	return &NonceRequest{
+		KeySelector: keySelector,
+		CryptoTS:    cryptoTS,
+		Nonce:       nonce,
+	}, nil
+}

mtproto/rpc/nonce_response.go

@@ -0,0 +1,60 @@
+package rpc
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/9seconds/mtg/mtproto"
+)
+
+type NonceResponse struct {
+	NonceRequest
+
+	Type   []byte
+	Crypto []byte
+}
+
+// Bytes returns serialized form of the nonce response.
+func (r *NonceResponse) Bytes() []byte {
+	buf := &bytes.Buffer{}
+
+	buf.Write(r.Type)        // nolint: gosec
+	buf.Write(r.KeySelector) // nolint: gosec
+	buf.Write(r.Crypto)      // nolint: gosec
+	buf.Write(r.CryptoTS)    // nolint: gosec
+	buf.Write(r.Nonce)       // nolint: gosec
+
+	return buf.Bytes()
+}
+
+func (r *NonceResponse) Valid(req *NonceRequest) error {
+	if !bytes.Equal(r.Type, mtproto.TagNonce) {
+		return errors.New("Unexpected RPC type")
+	}
+	if !bytes.Equal(r.Crypto, mtproto.NonceCryptoAES) {
+		return errors.New("Unexpected crypto type")
+	}
+	if !bytes.Equal(r.KeySelector, req.KeySelector) {
+		return errors.New("Unexpected key selector")
+	}
+
+	return nil
+}
+
+// NewNonceResponse build new nonce response based on the given data.
+func NewNonceResponse(data []byte) (*NonceResponse, error) {
+	if len(data) != 32 {
+		return nil, fmt.Errorf("Unexpected message length %d", len(data))
+	}
+
+	return &NonceResponse{
+		NonceRequest: NonceRequest{
+			KeySelector: data[4:8],
+			CryptoTS:    data[12:16],
+			Nonce:       data[16:],
+		},
+		Type:   data[:4],
+		Crypto: data[8:12],
+	}, nil
+}

mtproto/rpc/proxy_flags.go

@@ -0,0 +1,59 @@
+package rpc
+
+import (
+	"encoding/binary"
+	"strings"
+)
+
+type proxyRequestFlags uint32
+
+const (
+	proxyRequestFlagsHasAdTag     proxyRequestFlags = 0x8
+	proxyRequestFlagsEncrypted    proxyRequestFlags = 0x2
+	proxyRequestFlagsMagic        proxyRequestFlags = 0x1000
+	proxyRequestFlagsExtMode2     proxyRequestFlags = 0x20000
+	proxyRequestFlagsIntermediate proxyRequestFlags = 0x20000000
+	proxyRequestFlagsAbdridged    proxyRequestFlags = 0x40000000
+	proxyRequestFlagsQuickAck     proxyRequestFlags = 0x80000000
+	proxyRequestFlagsPad          proxyRequestFlags = 0x8000000
+)
+
+var proxyRequestFlagsEncryptedPrefix [8]byte
+
+func (r proxyRequestFlags) Bytes() []byte {
+	converted := make([]byte, 4)
+	binary.LittleEndian.PutUint32(converted, uint32(r))
+
+	return converted
+}
+
+func (r proxyRequestFlags) String() string {
+	flags := make([]string, 0, 7)
+
+	if r&proxyRequestFlagsHasAdTag != 0 {
+		flags = append(flags, "HAS_AD_TAG")
+	}
+	if r&proxyRequestFlagsEncrypted != 0 {
+		flags = append(flags, "ENCRYPTED")
+	}
+	if r&proxyRequestFlagsMagic != 0 {
+		flags = append(flags, "MAGIC")
+	}
+	if r&proxyRequestFlagsExtMode2 != 0 {
+		flags = append(flags, "EXT_MODE_2")
+	}
+	if r&proxyRequestFlagsIntermediate != 0 {
+		flags = append(flags, "INTERMEDIATE")
+	}
+	if r&proxyRequestFlagsAbdridged != 0 {
+		flags = append(flags, "ABRIDGED")
+	}
+	if r&proxyRequestFlagsQuickAck != 0 {
+		flags = append(flags, "QUICK_ACK")
+	}
+	if r&proxyRequestFlagsPad != 0 {
+		flags = append(flags, "PAD")
+	}
+
+	return strings.Join(flags, " | ")
+}