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[fix](protocol): improve Protobuf decoding with precise payload reading and clarification

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- Refactored `Decode` to use `io.ReadFull` for accurate length-prefix and payload reading.
- Simplified logic to avoid mismatched length issues and clarified comments for maintainability.
This commit is contained in:
dalbodeule
2025-12-09 20:11:21 +09:00
parent d4d6615c0e
commit 1847a264cb
1 changed files with 11 additions and 16 deletions
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27
internal/protocol/codec.go
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@@ -108,33 +108,28 @@ func (protobufCodec) Encode(w io.Writer, env *Envelope) error {
// Decode reads a length-prefixed protobuf Envelope and converts it into the internal Envelope. // Decode reads a length-prefixed protobuf Envelope and converts it into the internal Envelope.
// For DTLS (UDP-based), we read the entire datagram in a single Read call. // For DTLS (UDP-based), we read the entire datagram in a single Read call.
func (protobufCodec) Decode(r io.Reader, env *Envelope) error { func (protobufCodec) Decode(r io.Reader, env *Envelope) error {
// DTLS는 메시지 경계가 보존되는 UDP 기반 프로토콜입니다. // 1) 길이 prefix 4바이트를 정확히 읽는다.
// 한 번의 Read로 전체 데이터그램(length prefix + protobuf data)을 읽어야 합니다. header := make([]byte, 4)
// DTLS is a UDP-based protocol that preserves message boundaries. if _, err := io.ReadFull(r, header); err != nil {
// We must read the entire datagram (length prefix + protobuf data) in a single Read call. return fmt.Errorf("protobuf codec: read length prefix: %w", err)
buf := make([]byte, maxProtoEnvelopeBytes+4)
n, err := r.Read(buf)
if err != nil {
return fmt.Errorf("protobuf codec: read frame: %w", err)
}
if n < 4 {
return fmt.Errorf("protobuf codec: frame too short: %d bytes", n)
} }
// Extract and validate the length prefix length := binary.BigEndian.Uint32(header)
length := binary.BigEndian.Uint32(buf[:4])
if length == 0 { if length == 0 {
return fmt.Errorf("protobuf codec: zero-length envelope") return fmt.Errorf("protobuf codec: zero-length envelope")
} }
if length > maxProtoEnvelopeBytes { if length > maxProtoEnvelopeBytes {
return fmt.Errorf("protobuf codec: envelope too large: %d bytes (max %d)", length, maxProtoEnvelopeBytes) return fmt.Errorf("protobuf codec: envelope too large: %d bytes (max %d)", length, maxProtoEnvelopeBytes)
} }
if int(length) != n-4 {
return fmt.Errorf("protobuf codec: length mismatch: expected %d, got %d", length, n-4) // 2) payload 를 length 바이트만큼 정확히 읽는다.
payload := make([]byte, int(length))
if _, err := io.ReadFull(r, payload); err != nil {
return fmt.Errorf("protobuf codec: read payload: %w", err)
} }
var pbEnv protocolpb.Envelope var pbEnv protocolpb.Envelope
if err := proto.Unmarshal(buf[4:n], &pbEnv); err != nil { if err := proto.Unmarshal(payload, &pbEnv); err != nil {
return fmt.Errorf("protobuf codec: unmarshal envelope: %w", err) return fmt.Errorf("protobuf codec: unmarshal envelope: %w", err)
} }