Smart Contract Security: Based on Control Flow Integrity

Smart Contract Security: Based on Control Flow Integrity

Glossary

Term Definitions Smart Contracts Programs deployed on a blockchain whose code is automatically executed when certain conditions are met. Blockchain A distributed database that records transaction information and guarantees its security and transparency. Control Flow Integrity (CFI) A security mechanism used to ensure that a predefined control flow is followed during program execution to prevent malicious code injection. Control Flow Graph (CFG) A graphical representation used to describe all possible execution paths in a program. Basic Block (BBL) A node in a CFG that represents a set of instructions executed sequentially, with only one entry and one exit. Ethereum An open source blockchain platform that supports smart contracts and decentralized application development. Ethereum Virtual Machine (EVM) A virtual machine on the Ethereum platform that is used to execute smart contract code. Gas The execution cost of an Ethereum transaction, which is used to measure the consumption of computing resources. The DAO Attack A famous attack on the Ethereum smart contract platform in 2016 that resulted in millions of dollars in losses. Solidity A high-level programming language used to write Ethereum smart contracts. Fallback Function A default function executed when a smart contract receives funds for an unspecified function call. Etherscan.io is a block explorer for browsing the Ethereum blockchain, providing features such as smart contract code verification. opcode is a numeric code that represents a computer instruction. Short Answer Questions

What are smart contracts and how do they work?

Explain the concept of control flow integrity (CFI) and its role in software security.

How does Ethereum differ from traditional software programs in terms of smart contract execution?

Describe how the DAO attack exploited a smart contract vulnerability.

What role does Solidity play in smart contract development?

What is a fallback function and how is it exploited in smart contracts?

Explain how control flow graphs (CFGs) are used to enhance the security of smart contracts.

According to EP3477569B1, what information does a contract creator need to provide when deploying a smart contract?

In the system described in EP3477569B1, how does a contract verifier verify the execution of a smart contract?

Briefly describe the challenges of applying CFI to a blockchain environment.

Short Answer Questions

Smart contracts are self-executing contracts deployed on a blockchain, with their terms written directly into the code. When predefined conditions are met, the code is automatically executed without any middleman.

Control Flow Integrity (CFI) is a security mechanism used to ensure that program execution follows a predefined control flow. It improves software security by monitoring the control flow of the program and preventing malicious code injection or exploitation of vulnerabilities to change the expected execution path.

Ethereum's smart contract execution takes place in a decentralized network, and each node executes the same code. This is different from traditional software programs, which are usually run on a single machine and are more vulnerable to attacks.

The DAO attack exploited a vulnerability in the smart contract that allowed the attacker to withdraw funds multiple times before the withdrawal of funds was completed. The attacker created a recursive call that continuously withdrew funds from the DAO contract until a large amount of Ether was exhausted.

Solidity is a high-level programming language used to write Ethereum smart contracts. It provides a syntax that is easier to understand and write, and can be compiled into bytecode executable by the EVM.

The fallback function is the default function executed when a smart contract receives funds without specifying a function call. Attackers can use the fallback function to create recursive calls, thereby draining the funds of the contract.

Control flow graph (CFG) can be used to describe all possible execution paths of smart contracts. By limiting the execution of smart contracts to the path defined by CFG, attackers can be prevented from exploiting vulnerabilities to execute malicious code.

According to EP3477569B1, the contract creator needs to provide the smart contract code and the corresponding control flow graph (CFG) when deploying the smart contract.

In the system described in EP3477569B1, the contract verifier compares the execution path of the smart contract with the pre-provided CFG. If the execution path does not match the CFG, the execution is considered invalid.

There are some challenges in applying CFI to the blockchain environment, such as: the decentralized nature of smart contracts makes the deployment and maintenance of CFI more difficult; the computing resources on the blockchain are limited, and the CFI mechanism needs to be lightweight and efficient; the code of smart contracts is usually open and transparent, and attackers can more easily analyze and attack the CFI mechanism.