validate deal proposal (#702)

storagemarket/impl/provider.go

@@ -261,6 +261,10 @@ func (p *Provider) receiveDeal(s network.StorageDealStream) error {
 		return xerrors.Errorf("failed to read proposal message: %w", err)
 	}
 
+	if proposal.DealProposal == nil {
+		return xerrors.Errorf("failed to get deal proposal from proposal message")
+	}
+
 	proposalNd, err := cborutil.AsIpld(proposal.DealProposal)
 	if err != nil {
 		return err
@@ -274,6 +278,10 @@ func (p *Provider) receiveDeal(s network.StorageDealStream) error {
 		return p.resendProposalResponse(s, &md)
 	}
 
+	if proposal.Piece == nil {
+		return xerrors.Errorf("failed to get proposal piece from proposal message")
+	}
+
 	var path string
 	// create an empty CARv2 file at a temp location that Graphysnc will write the incoming blocks to via a CARv2 ReadWrite blockstore wrapper.
 	if proposal.Piece.TransferType != storagemarket.TTManual {