Use approve instead of safeApprove

[code423n4]

Handle

robee

Vulnerability details

Some tokens don't correctly implement the EIP20 standard and their approve function returns void instead of a success boolean.
Calling these functions with the correct EIP20 function signatures will always revert.
Tokens that don't correctly implement the latest EIP20 spec, like USDT, will be unusable in the mentioned contracts as they revert the transaction because of the missing return value.
We recommend using OpenZeppelin’s SafeERC20 versions with the safeApprove function that handle the return value check as well as non-standard-compliant tokens.
The list of occurrences in format (solidity file, line number, actual line)
CreditLine.sol, 646, IERC20(_collateralAsset).approve(_strategy, _amount);
CreditLine.sol, 774, IERC20(_borrowAsset).approve(_defaultStrategy, _amount);
Strategy.sol, 41, // IERC20(token).approve(mcd_join_eth_a, uint256(-1));
yVault.sol, 169, callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
yVault.sol, 178, callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
yVault.sol, 187, callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
AaveYield.sol, 293, IERC20(asset).approve(lendingPool, 0);
AaveYield.sol, 294, IERC20(asset).approve(lendingPool, amount);
AaveYield.sol, 303, IERC20(IWETHGateway(wethGateway).getAWETHAddress()).approve(wethGateway, amount);
AaveYield.sol, 320, IERC20(aToken).approve(lendingPool, amount);
CompoundYield.sol, 207, IERC20(asset).approve(cToken, 0);
CompoundYield.sol, 208, IERC20(asset).approve(cToken, amount);
YearnYield.sol, 206, IERC20(asset).approve(vault, 0);
YearnYield.sol, 207, IERC20(asset).approve(vault, amount);

[ritik99]

Duplicate of #2

[0xean]

downgrading based on the duplicate and risk implications of the approve.