Building Secure Smart Contracts

Speaker: Harry Papacharissiou @pappas9999 on Twitter

• two main sources of bugs:
  • infrastructure (protocols/evm)
  • smart contracts
• known vulnerabilities and exploits:
  • timestamp dependence and manipulation:
    • can be manipulated by a miner for a small window
    • solutions:
      • don't use timestamps
      • use block.number -> estimate time
  • unexpected ether:
    • can't protect against other contracts using selfDestruct(), which is a unreversable function
    • if logic requires control of ether, it will likely break
    • solution:
      • don't use this.balance
      • logic should be built to track ether independently of what contract has
  • Tx.Origin:
    • can be used by malicious contract to trigger functinos
    • solution:
      • don't use tx.origin for authorization
  • delegateCall:
    • this guy is too fast, check paritywallet hack
    • solution:
      • use library contracts
  • overflow/underflow attack:
    • wrapping integers can cause problems
    • Beauty Ecosystem Coin
    • solution:
      • use SafeMath
      • use solidity v0.8.0+
  • DoS attack:
    • make contract inoperable or trap ether
    • giving a user control over the execution of a contract via external call or data structures that have loops
    • solution:
      • use multi-sig contract
      • don't loop through uncontrolled structures
      • time locked resets
  • Race conditions / front running:
    • MEV
    • running a contract with higher gas usage
    • solutions:
      • modify upper bound on gas prices
      • use a commit-reveal scheme
      • chainlink FSS
  • re-entrancy attack:
    • sends ether to a contract
    • solution:
      • use transfer when sending to another contract
      • ensure all logic changes state first
      • use a mutex
    • see The DAO hack

I missed the last part of the talk :(