Files
mautrix-telegram/pkg/gotd/proto/codec/padded_intermediate.go
T
2025-06-27 20:03:37 -07:00

107 lines
2.5 KiB
Go

package codec
import (
"io"
"github.com/go-faster/errors"
"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
"go.mau.fi/mautrix-telegram/pkg/gotd/crypto"
)
// PaddedIntermediateClientStart is starting bytes sent by client in Padded intermediate mode.
//
// Note that server does not respond with it.
var PaddedIntermediateClientStart = [4]byte{0xdd, 0xdd, 0xdd, 0xdd}
// PaddedIntermediate is intermediate MTProto transport.
//
// See https://core.telegram.org/mtproto/mtproto-transports#padded-intermediate
type PaddedIntermediate struct{}
var (
_ TaggedCodec = PaddedIntermediate{}
)
// WriteHeader sends protocol tag.
func (i PaddedIntermediate) WriteHeader(w io.Writer) error {
if _, err := w.Write(PaddedIntermediateClientStart[:]); err != nil {
return errors.Wrap(err, "write padded intermediate header")
}
return nil
}
// ReadHeader reads protocol tag.
func (i PaddedIntermediate) ReadHeader(r io.Reader) error {
var b [4]byte
if _, err := io.ReadFull(r, b[:]); err != nil {
return errors.Wrap(err, "read padded intermediate header")
}
if b != PaddedIntermediateClientStart {
return ErrProtocolHeaderMismatch
}
return nil
}
// ObfuscatedTag returns protocol tag for obfuscation.
func (i PaddedIntermediate) ObfuscatedTag() [4]byte {
return PaddedIntermediateClientStart
}
// Write encode to writer message from given buffer.
func (i PaddedIntermediate) Write(w io.Writer, b *bin.Buffer) error {
if err := checkOutgoingMessage(b); err != nil {
return err
}
if err := checkAlign(b, 4); err != nil {
return err
}
if err := writePaddedIntermediate(crypto.DefaultRand(), w, b); err != nil {
return errors.Wrap(err, "write padded intermediate")
}
return nil
}
// Read fills buffer with received message.
func (i PaddedIntermediate) Read(r io.Reader, b *bin.Buffer) error {
if err := readPaddedIntermediate(r, b); err != nil {
return errors.Wrap(err, "read padded intermediate")
}
return checkProtocolError(b)
}
func writePaddedIntermediate(randSource io.Reader, w io.Writer, b *bin.Buffer) error {
length := b.Len()
b.Expand(4)
defer func() {
b.Buf = b.Buf[:length]
}()
_, err := io.ReadFull(randSource, b.Buf[length:length+4])
if err != nil {
return err
}
n := int(b.Buf[length-1]) % 4
b.Buf = b.Buf[:length+n]
return writeIntermediate(w, b)
}
func readPaddedIntermediate(r io.Reader, b *bin.Buffer) error {
if err := readIntermediate(r, b, true); err != nil {
return err
}
padding := b.Len() % 4
b.Buf = b.Buf[:b.Len()-padding]
return nil
}