Disable lineLimitReader when handle BDAT data

conn.go

@@ -40,6 +40,7 @@ type Conn struct {
 	locker     sync.Mutex
 	binarymime bool
 
+	bdatReader    *lineLimitReader
 	bdatPipe      *io.PipeWriter
 	bdatStatus    *statusCollector // used for BDAT on LMTP
 	dataResult    chan error
@@ -60,15 +61,17 @@ func newConn(c net.Conn, s *Server) *Conn {
 }
 
 func (c *Conn) init() {
+	c.bdatReader = &lineLimitReader{
+		R:            c.conn,
+		LineLimit:    c.server.MaxLineLength,
+		DisableCheck: false,
+	}
 	rwc := struct {
 		io.Reader
 		io.Writer
 		io.Closer
 	}{
-		Reader: &lineLimitReader{
-			R:         c.conn,
-			LineLimit: c.server.MaxLineLength,
-		},
+		Reader: c.bdatReader,
 		Writer: c.conn,
 		Closer: c.conn,
 	}
@@ -739,6 +742,7 @@ func (c *Conn) handleBdat(arg string) {
 		}()
 	}
 
+	c.bdatReader.DisableCheck = true
 	chunk := io.LimitReader(c.text.R, int64(size))
 	_, err = io.Copy(c.bdatPipe, chunk)
 	if err != nil {

lengthlimit_reader.go

@@ -12,14 +12,15 @@ var ErrTooLongLine = errors.New("smtp: too longer line in input stream")
 //
 // If line length exceeds the limit - Read returns ErrTooLongLine
 type lineLimitReader struct {
-	R         io.Reader
-	LineLimit int
+	R            io.Reader
+	LineLimit    int
+	DisableCheck bool
 
 	curLineLength int
 }
 
 func (r *lineLimitReader) Read(b []byte) (int, error) {
-	if r.curLineLength > r.LineLimit {
+	if r.curLineLength > r.LineLimit && !r.DisableCheck {
 		return 0, ErrTooLongLine
 	}
 
@@ -28,7 +29,7 @@ func (r *lineLimitReader) Read(b []byte) (int, error) {
 		return n, err
 	}
 
-	if r.LineLimit == 0 {
+	if r.LineLimit == 0 || r.DisableCheck {
 		return n, nil
 	}