CEtherGateway does not handle CEther.transferFrom return value

[lekhovitsky]

CEther is one of those older contracts which return failure flag instead of reverting.

In CEtherGateway, the only contract in our system that explicitly interacts with it, this is reflected in mint, redeem and redeemUnderlying calls, but missed in transfer and transferFrom:

• integrations-v3/contracts/helpers/compound/CompoundV2_CEtherGateway.sol

  Line 52 in 4bd6e30

  IERC20(ceth).transfer(msg.sender, IERC20(ceth).balanceOf(address(this)));

• integrations-v3/contracts/helpers/compound/CompoundV2_CEtherGateway.sol

  Line 61 in 4bd6e30

  IERC20(ceth).transferFrom(msg.sender, address(this), redeemTokens);

• integrations-v3/contracts/helpers/compound/CompoundV2_CEtherGateway.sol

  Line 79 in 4bd6e30

  IERC20(ceth).transferFrom(msg.sender, address(this), IERC20(ceth).balanceOf(msg.sender));

Thus, the contract should never be deployed in its current form. The fix would be to simply use safeTransfer and safeTransferFrom instead.

Credit to @pessimistic-io for discovery.