container: check id length in the getContainerSize, fix #321

Unfortunately, we can't check for more. Epoch number is serialized in a way
that is dynamic in size.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

container/container_contract.go

@@ -559,6 +559,11 @@ func PutContainerSize(epoch int, cid []byte, usedSize int, pubKey interop.Public
 func GetContainerSize(id []byte) containerSizes {
 	ctx := storage.GetReadOnlyContext()
 
+	if len(id) < len(estimateKeyPrefix)+containerIDSize ||
+		string(id[:len(estimateKeyPrefix)]) != estimateKeyPrefix {
+		panic("wrong estimation prefix")
+	}
+
 	// V2 format
 	// this `id` expected to be from `ListContainerSizes`
 	// therefore it is not contains postfix, we ignore it in the cut.

tests/container_test.go

@@ -362,6 +362,10 @@ func TestContainerSizeEstimation(t *testing.T) {
 			int64(2), cnt.id[:], int64(123), nodes[0].pub)
 	})
 
+	t.Run("incorrect key must fail", func(t *testing.T) {
+		_, err := c.TestInvoke(t, "getContainerSize", cnt.id[:])
+		require.Error(t, err)
+	})
 	c.WithSigners(nodes[0].signer).Invoke(t, stackitem.Null{}, "putContainerSize",
 		int64(2), cnt.id[:], int64(123), nodes[0].pub)
 	estimations := []estimation{{nodes[0].pub, 123}}