Add support for two tokens in erc to native

[patitonar]

Closes #318

[akolotov]

Commit the current state of the review. I will continue with review of the tests.

[patitonar]

Tested the implementation with MakerDAO contracts in Kovan testnet which are identical to the deployed in mainnet.

Sai Address: 0xc4375b7de8af5a38a93548eb8453a498222c4ff2
Dai Address: 0x4f96fe3b7a6cf9725f59d353f723c1bdb64ca6aa
ScdMcdMigration Address: 0x411b2faa662c8e3e5cf8f01dfdae0aee482ca7b0
Sai Top: 0x5f00393547561da3030ebf30e52f5dc0d5d3362c (from https://developer.makerdao.com/dai/1/api/)

Foreign Bridge Address: 0xb644F2c13D1e2410d224825991455fCBE95ACcd9

List of tx examples

• migrateToMCD 0x1470e2434ea73e3b4fcb10a8007b2f3def9e107746c9f615d9aea86dd3774c7f
• swapTokens 0x3e2b6b891aec411f378cf60fc04ebe6554f19ec14827ccc9d559e1ae8b183e02
• relayTokens sai 0x34ecac9a85cc1d44b86e22d70c2906294ab08d4f124073eb9296c4c904cd8eee
• relayTokens dai 0x1b1c1141ec38ba9e9321e05c91f34a9d7e610812954bf75ff5f868095484a4ee

[akolotov]

Tested the implementation with MakerDAO contracts in Kovan testnet which are identical to the deployed in mainnet.

thanks!

[akolotov]

Let's wait for feedback from Quantstamp who is performing the security audit for the new tokenbridge contracts release.

[akolotov]

@patitonar we again forgot to increase version of the contracts after adding new functionality.

[akolotov]

should we increase a version in getBridgeValidatorsInterfacesVersion?

[patitonar]

I think we should. Updated version to 2.3.0 be3cd33

[akolotov]

should we increase the version returned by getBridgeInterfacesVersion?

[patitonar]

Yes, it makes sense. Updated to 2.5.0 c2c2c4c

[akolotov]

As part of the security audit we have received a finding against this functionality and here is a recommendation: if the migration address is hardcoded or configurable, the migrateToMCD function does not need the onlyOwner modifier and anyone could invoke migrateToMCD, and thus trigger the migration.

So, let's remove the modifier onlyOwner.

[patitonar]

Updated the method 251f949

[patitonar]

Tested the upgrade with full changes following the steps mentioned here. Everything worked as expected and no issues were found.

Here are the new contract implementations:

• [xDai] HomeBridgeErcToNative: no migration method required. Gist: https://gist.github.com/patitonar/a19287408dfa878d7be1dca95835625f
• [mainnet] BridgeValidators: added migration method to create the list of validators. Gist: https://gist.github.com/patitonar/fe4888e786e9b6cdbfaeedaf8fe99b78

function upgradeToV230() public {
    bytes32 upgradeStorage = 0x2e8a0420c66b3c19df2ac1cd4ffadb5637da547c6fd49388c7fe28dc8c13a8dd; // keccak256(abi.encodePacked('isUpgradedToV230'))
    require(!boolStorage[upgradeStorage]);
    address validator1 = 0x9ad83402C19Af24F76afa1930a2B2EEC2F47A8C5;
    address validator2 = 0x4D1c96B9A49C4469A0b720a22b74b034EDdFe051;
    address validator3 = 0x491FC792e78CDadd7D31446Bb7bDDef876a69AD6;
    address validator4 = 0xc073C8E5ED9Aa11CF6776C69b3e13b259Ba9F506;

    setNextValidator(F_ADDR, validator1);
    setNextValidator(validator1, validator2);
    setNextValidator(validator2, validator3);
    setNextValidator(validator3, validator4);
    setNextValidator(validator4, F_ADDR);
    boolStorage[upgradeStorage] = true;
}

• [mainnet] ForeignBridgeErcToNative: added migration method for missing parameters. Gist: https://gist.github.com/patitonar/c0b77a59eceb76aad05e010c40569d47

function upgradeToV250() public {
    bytes32 upgradeStorage = 0x221181d03d3c423368b412861518cd98276a115f4c2d9594ab6697d90fc99c19; // keccak256(abi.encodePacked('isUpgradedToV250'))
    require(!boolStorage[upgradeStorage]);
    uintStorage[DAILY_LIMIT] = 100000 ether;
    emit DailyLimitChanged(100000 ether);
    uintStorage[MIN_PER_TX] = 5000000000000000;
    _setBridgeContractOnOtherSide(0x7301CFA0e1756B71869E93d4e4Dca5c7d0eb0AA6);
    boolStorage[upgradeStorage] = true;
}

I tested all steps using the strategy option 1 on Sokol and Kovan, using the set of contracts provided by makerDAO on Kovan. Except for step 9. Test Emergency Shutdown which was not possible to generate such a scenario.

I also tested upgrading in foreign side BridgeValidators and ForeignBridgeErcToNative with option 2 (using ganache-cli to fork the networks). I was able to deploy the new implementations and upgrade the contracts. I checked the state was not lost and new variables were correctly set. But I wasn't able to test the ui, oracle, and monitor in this case, because the forked local network generated by ganache was slow and sometimes it just stopped working when received a lot of requests, especially when trying to get events. Also, I wasn't able to deploy the new implementation for HomeBridgeErcToNative in the forked xDai, probably because of some issues with ganache-cli. I tested deploying the same contract directly in xDai and it worked correctly there.