Update ecrecover precompile

[zjb0807]

ref: polkadot-evm/frontier#964

[ermalkaleci]

@zjb0807 we already have the correct version, what does this change?

[zjb0807]

@ermalkaleci

Acala/modules/evm/src/precompiles/ecrecover.rs

Lines 42 to 47 in 0b8c9b4

	sig[64] = match input[63] {
	v if v > 26 && input[32..63] == [0; 31] => v - 27,
	_ => {
	return Ok((ExitSucceed::Returned, [0u8; 0].to_vec()));
	}
	};

If v > 26, then sig[64] = v - 27, let it be 0 or 1.
while geth version only accept 27 and 28.

[ermalkaleci]

if this is fixing an issue then there should be a test. where's v - 27 https://github.com/ethereum/go-ethereum/blob/a907d7e81aaeea15d80b2d3209ad8e08e3bf49e0/core/vm/contracts.go#L174?

[zjb0807]

It checked that input[63] > 26, so if it is input[63] = 30, it need to continue to verify the signature.
Now strictly check input[63] is 27/28.

[ermalkaleci]

It checked that input[63] > 26, so if it is input[63] = 30, it need to continue to verify the signature.

Now strictly check input[63] is 27/28.

If v > 26 then v - 27

[zjb0807]

If v > 26 then v - 27

So v can be 27~255 to call secp256k1_ecdsa_recover. Now it is only allowed on 27/28.