Throw error if marshaling invalid Uint256

[jtraglia]

What type of PR is this?

Bug fix

What does this PR do? Why is it needed?

Noticed that Uint256 didn't check that the value is a valid unsigned 256-bit integer. It could have been any big.Int value. We should return an error during marshaling/unmarshaling if the value is invalid.

[jtraglia]

This isn't actually an issue. It will be checked when encoded into a protobuf. For example:

prysm/proto/prysm/v1alpha1/beacon_block.pb.go

Line 2579 in 1062f5f

Value []byte `protobuf:"bytes,2,opt,name=value,proto3" json:"value,omitempty" ssz-size:"32"`

If the value is greater than 32 bytes, it is an invalid uint256 value. This does still allow negative numbers though.

[jtraglia]

Hmm nevermind. The protobuf check doesn't work the way I expected. I expected ToProto to return an error if the value is greater than 32 bytes, as specified by ssz-size:"32" in the structure. See this test, executed on develop:

// data.message.header.value is greater than uint256.max
var testBuilderBidInvalidValue = `{
    "version":"bellatrix",
	"data":{
		"message":{
			"header":{
				"parent_hash":"0xa0513a503d5bd6e89a144c3268e5b7e9da9dbf63df125a360e3950a7d0d67131",
				"fee_recipient":"0xdfb434922631787e43725c6b926e989875125751",
				"state_root":"0xca3149fa9e37db08d1cd49c9061db1002ef1cd58db2210f2115c8c989b2bdf45",
				"receipts_root":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
				"logs_bloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
				"prev_randao":"0xc2fa210081542a87f334b7b14a2da3275e4b281dd77b007bcfcb10e34c42052e",
				"block_number":"1",
				"gas_limit":"10000000",
				"gas_used":"0",
				"timestamp":"4660",
				"extra_data":"0x",
				"base_fee_per_gas":"7",
				"block_hash":"0x10746fa06c248e7eacd4ff8ad8b48a826c227387ee31a6aa5eb4d83ddad34f07",
				"transactions_root":"0x7ffe241ea60187fdb0187bfa22de35d1f9bed7ab061d9401fd47e34a54fbede1"
			},
			"value":"115792089237316195423570985008687907853269984665640564039457584007913129639936",
			"pubkey":"0x8645866c95cbc2e08bc77ccad473540eddf4a1f51a2a8edc8d7a673824218f7f68fe565f1ab38dadd5c855b45bbcec95"
		},
		"signature":"0x9183ebc1edf9c3ab2bbd7abdc3b59c6b249d6647b5289a97eea36d9d61c47f12e283f64d928b1e7f5b8a5182b714fa921954678ea28ca574f5f232b2f78cf8900915a2993b396e3471e0655291fec143a300d41408f66478c8208e0f9be851dc"
	}
}`

func TestBuilderBidUnmarshalInvalidValue(t *testing.T) {
	r := &ExecHeaderResponse{}
	require.NoError(t, json.Unmarshal([]byte(testBuilderBidInvalidValue), r))
	_, err := r.ToProto()
	require.NotEqual(t, nil, err)
}

ToProto will return a nil error: Values are equal, both values are equal: <nil> (<nil>).

And r.Data.Message.Value.BitLen() is 257 (one more bit than what is allowed).

[jtraglia]

There's a similar problem for all of the hexutil.Bytes fields too, right?

[rkapka]

Looks good, thanks!