Tutorial

Executing SmartExecutor on a contract

We consider on contract Crowdsale.sol.

pragma solidity ^0.4.25;
  contract Crowdsale {
  uint256 goal=100000*(10**18);
  uint256 phase=0;
  // 0: Active , 1: Success , 2: Refund
  uint256 raised;
  uint256 end;   address owner;
  mapping(address=>uint256) investments ;
  constructor() public{
    end=now+60 days ;
    owner=msg.sender ;
 }
  function invest() public payable{
    require(phase==0 && raised<goal);
    investments[msg.sender]+=msg.value ;
    raised+=msg.value ;
  }
  function setPhase(uint256 newPhase) public {
    require (
    (newPhase==1 && raised>=goal) ||
    (newPhase==2 && raised<goal && now>end));
    phase=newPhase ;
  }
  function setOwner(address newOwner) public {
    owner=newOwner ;
  }
  function withdraw() public {
    require(phase==1);
    owner.transfer(raised);
  }
  function refund() public {
    require(phase==2);
    msg.sender.transfer(investments[msg.sender]);
    investments[msg.sender]=0;
  }
}

To analyze the contract using SmartExecutor, the following command can be used:

$ semyth analyze */Crowdsale.sol:Crowdsale

The output will show the vulnerabilities in the contract.

==== Integer Arithmetic Bugs ====
SWC ID: 101
Severity: High
Contract: Crowdsale
Function name: constructor
PC address: 42
Estimated Gas Usage: 21038 - 103767
The arithmetic operator can overflow.
It is possible to cause an integer overflow or underflow in the arithmetic operation.
--------------------
In file: ./tests/testdata/solidity_files/Crowdsale.sol:10

now+60 days

--------------------
Initial State:

Account: [CREATOR], balance: 0x0, nonce:0, storage:{}
Account: [ATTACKER], balance: 0x0, nonce:0, storage:{}

Transaction Sequence:

Caller: [CREATOR], calldata: , decoded_data: , value: 0x0

==== Dependence on predictable environment variable ====
SWC ID: 116
Severity: Low
Contract: Crowdsale
Function name: setPhase(uint256)
PC address: 415
Estimated Gas Usage: 2729 - 2824
A control flow decision is made based on The block.timestamp environment variable.
The block.timestamp environment variable is used to determine a control flow decision. Note that the values of variables like coinbase, gaslimit, block number and timestamp are predictable and can be manipulated by a malicious miner. Also keep in mind that attackers know hashes of earlier blocks. Don't use any of those environment variables as sources of randomness and be aware that use of these variables introduces a certain level of trust into miners.
--------------------
In file: ./tests/testdata/solidity_files/Crowdsale.sol:19

require (
    (newPhase==1 && raised>=goal) ||
    (newPhase==2 && raised<goal && now>end))

--------------------
Initial State:

Account: [CREATOR], balance: 0x0, nonce:0, storage:{}
Account: [ATTACKER], balance: 0x0, nonce:0, storage:{}

Transaction Sequence:

Caller: [CREATOR], calldata: , decoded_data: , value: 0x0
Caller: [CREATOR], function: setPhase(uint256), txdata: 0x2cc826550000000000000000000000000000000000000000000000000000000000000002, decoded_data: (2,), value: 0x0