RACE-1.md

Note: All 8 questions in this quiz are based on the InSecureumToken contract shown below. This is the same contract you see for all the 8 questions in this quiz. The InSecureumToken contract implements a token contract which allows users to buy tokens by depositing Ether (at a certain conversion ratio), and transfer tokens.

pragma solidity 0.7.0;

contract InSecureumToken {

mapping(address => uint) private balances;

uint public decimals = 10**18; // decimals of the token
uint public totalSupply; // total supply
uint MAX_SUPPLY = 100 ether; // Maximum total supply

event Mint(address indexed destination, uint amount);

function transfer(address to, uint amount) public {
   // save the balance in local variables
   // so that we can re-use them multiple times
   // without paying for SLOAD on every access
   uint balance_from = balances[msg.sender];
   uint balance_to = balances[to];
   require(balance_from >= amount);
   balances[msg.sender] = balance_from - amount;
   balances[to] = safeAdd(balance_to, amount);
}


/// @notice Allow users to buy token. 1 ether = 10 tokens
/// @dev Users can send more ether than token to be bought, to donate a fee to the protocol team.
function buy(uint desired_tokens) public payable {
   // Check if enough ether has been sent
   uint required_wei_sent = (desired_tokens / 10) * decimals;
   require(msg.value >= required_wei_sent);

   // Mint the tokens
   totalSupply = safeAdd(totalSupply, desired_tokens);
   balances[msg.sender] = safeAdd(balances[msg.sender], desired_tokens);
   emit Mint(msg.sender, desired_tokens);
}


/// @notice Add two values. Revert if overflow
function safeAdd(uint a, uint b) pure internal returns(uint) {
   if (a + b < a) {
      revert();
   }
   return a + b;
}
}

---

[Q1] The InSecureumToken contract strictly follows the specification of

(A): ERC20
(B): ERC777
(C): ERC721
(D): None of the above

[Answers]

D

---

[Q2] To avoid lock of funds, the following feature(s) MUST be implemented before contract deployment

(A): A transferFrom() function
(B): A burn() function
(C): A way to withdraw/exchange/use Ether from the contract
(D): None of the above

[Answers]

C

---

[Q3] Which of the following assertion(s) is/are true (without affecting the security posture of the contract)?

(A): buy() does not need payable keyword
(B): balances must be private
(C): transfer() can be external
(D): safeAdd() can be public

[Answers]

C,D

---

[Q4] The total supply is limited by

(A): 10**18
(B): 100 * 10**18
(C): 100
(D): None of the above

[Answers]

D

---

[Q5] The following issue(s) is/are present in the codebase

(A): An integer underflow allows one to drain Ether
(B): Unsafe rounding allows one to receive new tokens for free
(C): A division by zero allows one to trap/freeze the system
(D): None of the above

[Answers]

B

---

[Q6] The following issue(s) is/are present in the codebase

(A): A front-running allows one to pay less than expected for tokens
(B): A lack of access control allows one to receive tokens for free
(C): Incorrect balance update allows one to receive new tokens for free
(D): None of the above

[Answers]

C

---

[Q7] The following issue(s) is/are present in the codebase

(A): A reentrancy allows one to drain Ether
(B): A reentrancy allows one to drain the tokens
(C): A reentrancy allows one to receive new tokens for free
(D): None of the above

[Answers]

D

---

[Q8] The following issue(s) is/are present in the codebase

(A): An integer overflow allows one to drain Ether
(B): An integer overflow allows one to receive new tokens for free
(C): An integer overflow allows one to trap/freeze the system
(D): None of the above

[Answers]

D or B or C or B,C

---