Gas Abstraction

[petejkim]

Technical Design Doc

• Adds increaseAllowance and decreaseAllowance to mitigate ERC20 multi-withdrawal attack vulnerability approve has.
• Adds transferWithAuthorization, approveWithAuthorization, increaseAllowanceWithAuthorization, decreaseAllowanceWithAuthorization to enable ETH-less transactions.
• Adds permit – an alternative to approveWithAuthorization, provided for compatibility with the draft EIP2612 proposed by Uniswap. Differences are laid out here.

[eztierney]

Slowly going through this, but in general looks good so far.

One thing that would be helpful is adding a doc in the docs directory explaining the new v2 features - including things like how to sign approvals, why we we have the *WithAuthorization methods and permit, etc.

I can puzzle most of it out from the code/comments but would be nice to have it all in 1 place for future integrators who are trying to build on these features.

[eztierney]

This looks really good - I noticed maybe 1 missing test, but code coverage indicates maybe a few more.
I think we should try to get ECRecover.sol and the v2 contracts to 100% for this PR. There are some 1.1 and upgradeablility issues in the coverage too, but those don't need to block this PR - and we should probably fix those in master anyways.

The code coverage report I got:

File                           |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
-------------------------------|----------|----------|----------|----------|----------------|
 upgradeability/               |      100 |    78.57 |      100 |      100 |                |
  AdminUpgradeabilityProxy.sol |      100 |       80 |      100 |      100 |                |
  Proxy.sol                    |      100 |      100 |      100 |      100 |                |
  UpgradeabilityProxy.sol      |      100 |       75 |      100 |      100 |                |
 util/                         |    81.82 |     62.5 |      100 |    83.33 |                |
  ECRecover.sol                |    71.43 |       50 |      100 |    71.43 |          63,67 |
  EIP712.sol                   |      100 |      100 |      100 |      100 |                |
 v1.1/                         |      100 |       75 |      100 |      100 |                |
  FiatTokenV1_1.sol            |      100 |      100 |      100 |      100 |                |
  Rescuable.sol                |      100 |       75 |      100 |      100 |                |
 v1/                           |      100 |     96.3 |      100 |      100 |                |
  AbstractFiatTokenV1.sol      |      100 |      100 |      100 |      100 |                |
  Blacklistable.sol            |      100 |      100 |      100 |      100 |                |
  FiatTokenProxy.sol           |      100 |      100 |      100 |      100 |                |
  FiatTokenV1.sol              |      100 |    94.74 |      100 |      100 |                |
  Ownable.sol                  |      100 |      100 |      100 |      100 |                |
  Pausable.sol                 |      100 |      100 |      100 |      100 |                |
 v2/                           |    96.23 |       90 |    90.91 |    96.23 |                |
  AbstractFiatTokenV2.sol      |      100 |      100 |      100 |      100 |                |
  EIP712Domain.sol             |      100 |      100 |      100 |      100 |                |
  FiatTokenV2.sol              |      100 |       50 |      100 |      100 |                |
  GasAbstraction.sol           |    96.88 |      100 |    88.89 |    96.88 |             71 |
  Permit.sol                   |       80 |      100 |       50 |       80 |             53 |
-------------------------------|----------|----------|----------|----------|----------------|
All files                      |    97.89 |    88.89 |    97.56 |    98.05 |                |
-------------------------------|----------|----------|----------|----------|----------------|```

[petejkim]

Improved test coverage. New code is all at 100% now.

-------------------------------|----------|----------|----------|----------|----------------|
File                           |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
-------------------------------|----------|----------|----------|----------|----------------|
 upgradeability/               |      100 |    78.57 |      100 |      100 |                |
  AdminUpgradeabilityProxy.sol |      100 |       80 |      100 |      100 |                |
  Proxy.sol                    |      100 |      100 |      100 |      100 |                |
  UpgradeabilityProxy.sol      |      100 |       75 |      100 |      100 |                |
 util/                         |      100 |      100 |      100 |      100 |                |
  ECRecover.sol                |      100 |      100 |      100 |      100 |                |
  EIP712.sol                   |      100 |      100 |      100 |      100 |                |
 v1.1/                         |      100 |      100 |      100 |      100 |                |
  FiatTokenV1_1.sol            |      100 |      100 |      100 |      100 |                |
  Rescuable.sol                |      100 |      100 |      100 |      100 |                |
 v1/                           |      100 |     96.3 |      100 |      100 |                |
  AbstractFiatTokenV1.sol      |      100 |      100 |      100 |      100 |                |
  Blacklistable.sol            |      100 |      100 |      100 |      100 |                |
  FiatTokenProxy.sol           |      100 |      100 |      100 |      100 |                |
  FiatTokenV1.sol              |      100 |    94.74 |      100 |      100 |                |
  Ownable.sol                  |      100 |      100 |      100 |      100 |                |
  Pausable.sol                 |      100 |      100 |      100 |      100 |                |
 v2/                           |      100 |      100 |      100 |      100 |                |
  AbstractFiatTokenV2.sol      |      100 |      100 |      100 |      100 |                |
  EIP712Domain.sol             |      100 |      100 |      100 |      100 |                |
  FiatTokenV2.sol              |      100 |      100 |      100 |      100 |                |
  GasAbstraction.sol           |      100 |      100 |      100 |      100 |                |
  Permit.sol                   |      100 |      100 |      100 |      100 |                |
-------------------------------|----------|----------|----------|----------|----------------|
All files                      |      100 |    94.44 |      100 |      100 |                |
-------------------------------|----------|----------|----------|----------|----------------|

[eztierney]

Thanks, looks good