From 39ad3d3b279509b04e54a3724dafba0341b044ca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Magiera?= <magik6k@gmail.com>
Date: Tue, 16 Feb 2021 20:48:31 +0100
Subject: [PATCH] Check format in client commP util

---
 node/impl/client/client.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/node/impl/client/client.go b/node/impl/client/client.go
index 00c840b6360..ac526ac6030 100644
--- a/node/impl/client/client.go
+++ b/node/impl/client/client.go
@@ -711,6 +711,16 @@ func (a *API) ClientCalcCommP(ctx context.Context, inpath string) (*api.CommPRet
 		return nil, err
 	}
 
+	// check that the data is a car file; if it's not, retrieval won't work
+	_, _, err = car.ReadHeader(bufio.NewReader(rdr))
+	if err != nil {
+		return nil, xerrors.Errorf("not a car file: %w", err)
+	}
+
+	if _, err := rdr.Seek(0, io.SeekStart); err != nil {
+		return nil, xerrors.Errorf("seek to start: %w", err)
+	}
+
 	pieceReader, pieceSize := padreader.New(rdr, uint64(stat.Size()))
 	commP, err := ffiwrapper.GeneratePieceCIDFromFile(arbitraryProofType, pieceReader, pieceSize)