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Attack the Auction

Welcome to the Blockchain for Developers DeCal's third assignment. You'll be getting acclimated with external calls, inheritance, and smart contract security.

Homework Instructions

Your task is to complete both BadAuction.sol and GoodAuction.sol such that they are each, respectively, vulnerable and protected from a push/pull reentrancy attack. Notice that both contracts inherit from AuctionInterface.sol.

Poisoned.sol and NotPoisoned.sol are both players in an adversarial system. Both can conduct external calls to the auctions in order to place bids. While NotPoisoned.sol will act as expected, Poisoned.sol will attempt to take advantage of BadAuction.sol's push-based paradigm. Do not make changes to these contracts

Implement both auctions in order to demonstrate your understanding of what makes smart contracts vulnerable and how to secure them.

All work should be done in contracts/BadAuction.sol and contracts/GoodAuction.sol

Rules

  • In any situation, a bidder with a lower or the same bid than the current highest bidder should have no effect on the contract
    • The contract should return false in this situation
    • The bidder should still be able to get their money back
  • A bidder with a higher bid should:
    • Be able to displace the previous highest bidder if the previous highest bidder were not poisoned
      • The contract should return true in this situation
    • Be able to displace the previous highest bidder if bidding at a good auction
      • The contract should return false in this situation
    • Not be able to displace the previous highest bidder if bidding on a bad auction and the previous highest bidder was poisoned
      • The bidder should still be able to get their money back
  • A previous highest bidder should only get back an amount equivalent to what their bet (the previous highest bet) was; no more, no less

Minimum Requirements

  • All fifteen tests should pass
  • Each auction file should follow the requirements set by the skeleton code (as well as the AuctionInterface.sol)
  • Do not change any files except for BadAuction.sol and GoodAuction.sol

Testing

You can verify that your smart contract is implemented correctly with truffle test. Be sure to have a testrpc server running in a separate terminal.

Refresher: in an empty terminal, run testrpc to initialize a default testrpc server. If you get errors, read the testrpc documentation.

Truffle Console

If you're having trouble passing the tests and would like to play around with the contracts manually:

  1. Run truffle migrate
  2. Run truffle console, This will open up a Node JavaScript console that is connected to your testrpc server

Submission Instructions

Please fork this repo and push your code up to your fork. Please fill out this Google Form to let us know where you've got your answers: https://goo.gl/forms/TmXtCfx3TRPS2DbF2.

Please feel free to reach out to the staff via Piazza should you run into any trouble.