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Use validator set precompiles in Attestations #1248

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merged 10 commits into from
Oct 22, 2019
Merged

Use validator set precompiles in Attestations #1248

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5c204df
Use validator set precompiles in Attestations
m-chrzan Oct 2, 2019
ee13557
Merge branch 'master' into m-chrzan/use-validator-precompile
m-chrzan Oct 14, 2019
d3da2f0
Use precompiles in Attestations directly
m-chrzan Oct 16, 2019
b8e9211
Merge branch 'master' into m-chrzan/use-validator-precompile
m-chrzan Oct 16, 2019
fb9aba1
Document use of test contract
m-chrzan Oct 16, 2019
8701010
Merge branch 'master' into m-chrzan/use-validator-precompile
m-chrzan Oct 16, 2019
ec08cdd
Move precompile usage to separate contract
m-chrzan Oct 16, 2019
535b8e1
Remove superflous methods
nambrot Oct 17, 2019
ce76b44
Merge branch 'master' into m-chrzan/use-validator-precompile
nambrot Oct 17, 2019
31905d2
Merge branch 'master' into m-chrzan/use-validator-precompile
cmcewen Oct 22, 2019
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2 changes: 2 additions & 0 deletions packages/protocol/contracts/governance/interfaces/IValidators.sol
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Expand Up @@ -5,4 +5,6 @@ interface IValidators {
function isVoting(address) external view returns (bool);
function isValidating(address) external view returns (bool);
function getValidators() external view returns (address[] memory);
function validatorAddressFromCurrentSet(uint256) external view returns (address);
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Do we need this in the IValidators interface?

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Leftover from before moving the precompile into Attestations.

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So remove it?

function numberValidatorsInCurrentSet() external view returns (uint256);
}
8 changes: 8 additions & 0 deletions packages/protocol/contracts/governance/test/MockValidators.sol
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Expand Up @@ -23,6 +23,14 @@ contract MockValidators is IValidators {
return validators;
}

function numberValidatorsInCurrentSet() external view returns (uint256) {
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Why do we need this in MockValidators?

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Same as the IValidators issue below.

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Remove it?

return validators.length;
}

function validatorAddressFromCurrentSet(uint256 index) external view returns (address) {
return validators[index];
}

function setValidating(address account) external {
_isValidating[account] = true;
}
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10 changes: 8 additions & 2 deletions packages/protocol/contracts/identity/Attestations.sol
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Expand Up @@ -757,17 +757,23 @@ contract Attestations is
internal
{
IRandom random = IRandom(registry.getAddressForOrDie(RANDOM_REGISTRY_ID));
IValidators validators = IValidators(
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Do we need to call into the Validators smart contract for this, or can this contract call the precompile directly?

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We could. I was imagining having Validators expose a wrapper around the precompile to minimize complexity (with assembly in other contracts), though this does increase gas costs.

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Agree with wanting to cut gas costs, but there is also a small technical problem I just ran into, that the current solution kind of nicely circumvents.

If we use the precompile directly, we can't do ganache tests if we don't modify ethereumjs-vm to handle this precompile (which is not trivial since ganache has no concept of a validator set). By calling into the precompile wrapper in Validators, we can mock Validators and still test this function.

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As we discussed offline, I think it's probably best to call the precompile directly in a privaet function, and to have a TestAttestations contract that inherits from Attestations and mocks out the call to the precompile

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Consider defining a UsingPrecompiles contract, e.g. https://github.com/celo-org/celo-monorepo/pull/1292/files#diff-0cffec14a25e6876b387a826c4b4946d

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It would be nice to add some support for this to ganache. If not, we can't call any part of core contracts that use validators.

Maybe define a list of addresses to serve as validators when launching it

registry.getAddressForOrDie(VALIDATORS_REGISTRY_ID)
);

bytes32 seed = random.random();
address[] memory validators = getValidators();
uint256 numberValidators = validators.numberValidatorsInCurrentSet();

uint256 currentIndex = 0;
address validator;
address issuer;

while (currentIndex < n) {
seed = keccak256(abi.encodePacked(seed));
validator = validators[uint256(seed) % validators.length];
validator = validators.validatorAddressFromCurrentSet(
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uint256(seed) % numberValidators
);

issuer = getAccountFromValidator(validator);
Attestation storage attestations =
state.issuedAttestations[issuer];
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