[#131] client: Return io.ErrUnexpectedEOF on cut object payload

Make `ObjectReader` / `ObjectRangeReader` to track number of bytes read
and return:
  * `io.ErrUnexpectedEOF` if the stream finished by the server before
  the last byte of the payload was read.
  * an error if more object payload size bytes was read.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

client/object_get.go

@@ -107,6 +107,8 @@ type ObjectReader struct {
 	bodyResp v2object.GetResponseBody
 
 	tailPayload []byte
+
+	remainingPayloadLen int
 }
 
 // UseKey specifies private key to sign the requests.
@@ -147,6 +149,8 @@ func (x *ObjectReader) ReadHeader(dst *object.Object) bool {
 	objv2.SetHeader(partInit.GetHeader())
 	objv2.SetSignature(partInit.GetSignature())
 
+	x.remainingPayloadLen = int(objv2.GetHeader().GetPayloadLength())
+
 	*dst = *object.NewFromV2(&objv2) // need smth better
 
 	return true
@@ -208,6 +212,8 @@ func (x *ObjectReader) close(ignoreEOF bool) (*ResObjectGet, error) {
 	if x.ctxCall.err != nil {
 		if !errors.Is(x.ctxCall.err, io.EOF) {
 			return nil, x.ctxCall.err
+		} else if x.remainingPayloadLen > 0 {
+			return nil, io.ErrUnexpectedEOF
 		} else if !ignoreEOF {
 			return nil, io.EOF
 		}
@@ -239,11 +245,17 @@ func (x *ObjectReader) Read(p []byte) (int, error) {
 		res, err := x.close(false)
 		if err != nil {
 			return n, err
-		} else if !x.ctxCall.resolveAPIFailures {
+		}
+
 		return n, apistatus.ErrFromStatus(res.Status())
 	}
+
+	if n > x.remainingPayloadLen {
+		return n, errors.New("payload size overflow")
 	}
 
+	x.remainingPayloadLen -= n
+
 	return n, nil
 }
 
@@ -497,6 +509,8 @@ type ObjectRangeReader struct {
 	bodyResp v2object.GetRangeResponseBody
 
 	tailPayload []byte
+
+	remainingPayloadLen int
 }
 
 // UseKey specifies private key to sign the requests.
@@ -572,6 +586,8 @@ func (x *ObjectRangeReader) close(ignoreEOF bool) (*ResObjectRange, error) {
 	if x.ctxCall.err != nil {
 		if !errors.Is(x.ctxCall.err, io.EOF) {
 			return nil, x.ctxCall.err
+		} else if x.remainingPayloadLen > 0 {
+			return nil, io.ErrUnexpectedEOF
 		} else if !ignoreEOF {
 			return nil, io.EOF
 		}
@@ -603,11 +619,17 @@ func (x *ObjectRangeReader) Read(p []byte) (int, error) {
 		res, err := x.close(false)
 		if err != nil {
 			return n, err
-		} else if !x.ctxCall.resolveAPIFailures {
+		}
+
 		return n, apistatus.ErrFromStatus(res.Status())
 	}
+
+	if n > x.remainingPayloadLen {
+		return n, errors.New("payload range size overflow")
 	}
 
+	x.remainingPayloadLen -= n
+
 	return n, nil
 }
 
@@ -677,6 +699,8 @@ func (c *Client) ObjectRangeInit(ctx context.Context, prm PrmObjectRange) (*Obje
 		stream *rpcapi.ObjectRangeResponseReader
 	)
 
+	r.remainingPayloadLen = int(prm.ln)
+
 	ctx, r.cancelCtxStream = context.WithCancel(ctx)
 
 	resp.SetBody(&r.bodyResp)