ctfnote
  • /home/ret2basic.eth
  • Game Hacking
    • โœ…C++
    • Ghidra
    • Cheat Engine
    • Proxy
    • DLL injection
    • Keygen
    • Aimbot
  • Web3 Security Research
    • ๐Ÿ‘‘Web3 Security Research Trivia
    • โœ…Solidity
      • โœ…Mastering Ethereum
      • โœ…Storage
      • โœ…Memory
      • โœ…Calldata
      • โœ…ABI
    • โœ…Foundry
      • โœ…Introduction
      • โœ…How to Write Basic Tests
      • โœ…Set Soliditiy Compiler Version
      • โœ…Remappings
      • โœ…Auto Format Code
      • โœ…Console Log
      • โœ…Authentication
      • โœ…Error
      • โœ…Event
      • โœ…Time
      • โœ…Send ETH
      • โœ…Signature
      • โœ…Fork
      • โœ…Mint 1 Million DAI on Mainnet Fork
      • โœ…FFI
      • โœ…Fuzz
      • โœ…Invariant Testing - Part 1
      • Invariant Testing - Part 2
      • Invariant Testing - Part 3
      • Differential Test
    • โœ…Secureum
      • โœ…Epoch 0
        • โœ…Slot 1: Ethereum 101
          • โœ…Notes
          • โœ…Ethereum Whitepaper
          • โœ…Extra Study: What happens when you send 1 DAI
          • โœ…Quiz
        • โœ…Slot 2: Solidity 101
          • โœ…Notes
          • โœ…OpenZeppelin ERC20
          • โœ…OpenZeppelin ERC721
          • โœ…OpenZeppelin Ownable
          • โœ…OpenZeppelin Pausable
          • โœ…OpenZeppelin ReentrancyGuard
          • โœ…Quiz
        • โœ…Slot 3: Solidity 201
          • โœ…Notes
          • โœ…OpenZeppelin SafeERC20
          • โœ…OpenZeppelin ERC-777
          • โœ…OpenZeppelin ERC-1155
          • โœ…OpenZeppelin ERC-3156
          • โœ…OpenZeppelin - Proxy Upgrade Pattern
          • โœ…Quiz
        • โœ…Slot 4: Pitfalls and Best Practices 101
          • โœ…Notes
          • โœ…Intro to Security First Development
          • โœ…Quiz
        • โœ…Slot 5: Pitfalls and Best Practices 201
          • โœ…Notes
          • So you want to use a price oracle
          • The Dangers of Surprising Code
          • โœ…Quiz
        • โœ…Slot 6: Auditing Techniques & Tools 101
          • โœ…Notes
          • โœ…Quiz
        • โœ…Slot 7: Audit Findings 101
          • Notes
          • โœ…Fei Protocol - ConsenSys
          • โœ…Uniswap V3 - Trail of Bits
          • โœ…Chainlink - Sigma Prime
          • โœ…Opyn Gamma - OpenZeppelin
          • โœ…Quiz
        • โœ…Slot 8: Audit Findings 201
          • Notes
          • 1inch Liquidity - Consensus
          • Original Dollar - Trail of Bits
          • Synthetix EtherCollateral - Sigma Prime
          • Holdefi - OpenZeppelin
          • Quiz
      • โœ…Epoch โˆž
        • โœ…RACE #4 - ERC20 Implementation
        • โœ…RACE #5 - ERC1155 Implementation
        • โœ…RACE #6 - ERC721 Application
        • โœ…RACE #7 - Bored Ape
        • โœ…RACE #8 - ERC721 Roles
        • โœ…RACE #9 - Proxy
        • โœ…RACE #10 - Test Cases
        • โœ…RACE #11 - Staking
        • โœ…RACE #12 - ERC20 Permit
        • โœ…RACE #13 - ERC20 with Callback
        • โœ…RACE #14 - Lending
        • โœ…RACE #15 - DEX
        • โœ…RACE #16 - Flash Loan
        • โœ…RACE #17
    • DeFi
      • Glossary
        • TWAP vs. VWAP
        • Tranches
      • DeFi MOOC
        • Lecture 2: Introduction to Blockchain Technologies
        • Lecture 5: DEX
        • Lecture 6: Decentralized Lending
        • Lecture 10: Privacy on the Blockchain
        • Lecture 12: Practical Smart Contract Security
        • Lecture 13: DeFi Security
      • Uniswap V2
      • Compound V3
        • โœ…Whitepaper
        • โœ…Interacting with Compound
          • โœ…Supply and Redeem
          • โœ…Borrow and Repay
          • โœ…Liquidation
          • โœ…Long and Short
        • โœ…Interest Model
        • CToken
      • Aave
      • Chainlink
        • โœ…Getting Started
        • โœ…Data Feeds
        • โœ…VRF
      • Optimism
        • Bedrock
      • LayerZero
      • Opensea
        • Seaport
    • EVM
      • โœ…Andreas Antonopoulos - The Ethereum Virtual Machine
      • โœ…Program The Blockchain - Smart Contract Storage
      • โœ…EVM Codes - EVM Playground for Opcodes
      • โœ…Fvictorio - EVM Puzzles
      • โœ…Daltyboy11 - More EVM Puzzles
      • โœ…EVM Through Huff
      • Noxx - EVM Deep Dives
      • โœ…Jordan McKinney - EVM Explained
      • Openzepplin - Deconstructing a Solidity Contract
      • Jeancvllr - EVM Assembly
      • Peter Robinson - Solidity to Bytecode, Memory & Storage
      • Marek Kirejczyk - Ethereum Under The Hood
      • โœ…Official Solidity Docs
      • Dissecting EVM using go-ethereum Eth client implementation - deliriusz.eth
    • Vulnerabilities
      • Rounding Issues
        • Kyberswap
      • Bridges
      • Governance / Voting Escrows
      • Bizzare Bug Classes
        • TIME - ERC2771Context + Multicall calldata manipulation
    • Fancy Topics
      • Vulnerabilities SoK
        • โœ…Demystifying Exploitable Bugs in Smart Contracts
        • Blockchain Hacking Techniques 2022 Top 10 - Todo
      • yAcademy
        • Proxies
          • yAcademy - Proxy Basics
          • yAcademy - Proxies Deep Dive
          • yAcademy - Security Guide to Proxy Vulns
        • defi-fork-bugs
      • Spearbit
        • โœ…Community Workshop: Riley Holterhus
        • Economic Security with fmrmf
        • Numerical Analysis for DeFi Audits: A TWAMM Case Study by Kurt Barry
  • Red Teaming
    • โœ…Enumeration
      • Service Enumeration
        • SMTP (Port 25)
        • Samba (Port 139, 445)
        • SNMP (Port 161,162,10161,10162)
        • rsync (Port 873)
        • NFS (Port 2049)
        • Apache JServ Protocol (Port 8081)
        • NetBIOS
      • Nmap
      • Gobuster / Feroxbuster / FUFF / Wfuzz
      • Drupal
    • โœ…Exploitation
      • Public Exploits
      • PHP Webshells
      • Reverse Shell
      • TTY
      • File Transfer
      • Metasploit
      • Password Spray
    • โœ…Buffer Overflow
      • Step 0: Spiking (Optional)
      • Step 1: Fuzzing
      • Step 2: Finding the Offset
      • Step 3: Overwriting the EIP
      • Step 4: Finding Bad Characters
      • Step 5: Finding the Right Module
      • Step 6: Generating Shellcode and Gaining Root
    • โœ…Privilege Escalation
      • Linux Privilege Escalation
        • Linux Permissions
        • Manual Enumeration
        • Automated Tools
        • Kernel Exploits
        • Passwords and File Permissions
        • SSH Keys
        • Sudo
        • SUID
        • Capabilities
        • Cron Jobs
        • NFS Root Squashing
        • Docker
        • GNU C Library
        • Exim
        • Linux Privilege Escalation Course Capstone
      • Windows Privilege Escalation
        • Manual Enumeration
        • Automated Tools
        • Kernel Exploits
        • Passwords and Port Forwarding
        • WSL
        • Token Impersonation and Potato Attacks
        • Meterpreter getsystem
        • Runas
        • UAC Bypass
        • Registry
        • Executable Files
        • Startup Applications
        • DLL Hijacking
        • Service Permissions (Paths)
        • CVE-2019-1388
        • HiveNightmare
        • Bypass Space Filter
    • โœ…Post Exploitation
      • Linux Post Exploitation
        • Add a User
        • SSH Key
      • Windows Post Exploitation
        • windows-resources
        • Add a User
        • RDP
    • โœ…Pivoting
      • Windows: Chisel
      • Linux: sshuttle
    • Active Directory (AD)
      • Initial Compromise
        • HTA Phishing
        • VBA Macro Phishing
        • LLMNR Poisoning
        • SMB Relay
        • GPP / cPassword
      • Domain Enumeration
        • Manual Enumeration
        • PowerView
        • BloodHound
      • Lateral Movement
        • PsExec
        • WMI
        • Runas
        • Pass the Hash
        • Overpass the Hash
        • Pass the Ticket
      • Kerberos
        • Kerberoast
        • AS-REP Roast
      • MS SQL Server
    • Command & Control (C2)
      • Cobalt Strike
        • Bypassing Defences
          • Artifact Kit
          • Resource Kit
          • AMSI Bypass
          • PowerPick
        • Extending Cobalt Strike
          • Elevate Kit
          • Malleable C2 Profile
      • Metasploit
        • Payloads
        • Post Exploitation
        • Automation
      • C2 Development
    • Malware Development
      • "Hot Dropper"
      • PE Format
        • Overview
      • Process Injection
      • Reflective DLL
      • x86 <=> x64
      • Hooking
      • VeraCry
      • Offensive C#
      • AV Evasion
        • AV Evasion with C# and PowerShell
        • AMSI Bypass
  • Cryptography
    • Hash Functions
    • MAC
    • AES
      • Byte at a Time
      • CBC CCA
      • CBC Bit Flipping
      • CBC Padding Oracle
    • Diffie-Hellman
    • RSA
      • Prime Factors
      • Multiple Ciphertexts
      • Low Public Exponent
      • Low Private Exponent
    • ECC
    • Digital Signature
    • JWT
    • PRNG
    • SSL/TLS
    • Research
      • โœ…Lattice-based Cryptography (Lattice)
      • Elliptic Curve Cryptography (ECC)
      • Oblivious Transfer (OT)
      • Secure Multi-party Computation (MPC)
      • Learning with Error (LWE)
      • Fully Homomorphic Encryption (FHE)
      • Zero Knowledge Proof (ZKP)
      • Oblivious RAM (ORAM)
  • Computer Science
    • Linux
      • Setup
      • curl
      • Hard Link vs. Symlink
      • Man Page
      • /dev/null
    • Python
      • New Features
      • Operators, Expressions, and Data Manipulation
      • Program Structure and Control Flow
      • Objects, Types, and Protocols
      • Functions 101
      • Generators
      • Classes and Object-Oriented Programming
      • Memory Management
      • Concurrency and Parallelism
        • Multithreading and Thread Safety
        • Asynchronization
        • Multiprocessing
        • Global Interpreter Lock (GIL)
      • Built-in Functions and Standard Library
        • import collections
        • import itertools
        • import sys
        • import re
        • import pickle
        • import json
      • Third-party Library
        • from pwn import *
        • import requests
        • from bs4 import BeautifulSoup
        • from scapy.all import *
        • py2exe
    • HTML, CSS, JavaScript, and React
      • HTML
      • CSS
      • JavaScript
        • var vs. let
        • Objects
        • Arrays
        • Functions
        • Modules
        • Asynchronous JavaScript
      • React
    • Data Structures and Algorithms
      • Binary Search
    • The Linux Programming Interface
      • Processes
        • Memory Allocation
        • The Process API
        • Process Creation
        • Process Termination
        • Monitoring Child Processes
        • Program Execution
      • Signals
      • Threads
        • Thread Synchronization
        • Thread Safety and Pre-Thread Storage
      • IPC
        • Pipes and FIFOs
        • Memory Mappings
        • Virtual Memory Operations
      • Sockets
    • Computer Systems
      • Hexadecimal
      • Signedness
      • Registers
      • Instructions
      • Syscall
      • Process Memory
      • Stack Frame
      • Preemptive Multitasking
      • IPC
      • Threads
    • Databases
      • MySQL
        • Basic Syntax
        • Data Types
        • Modifying Tables
        • Duplicating and Deleting
        • SELECT
        • Transaction
      • GraphQL
    • Distributed Systems
      • Introduction
        • What is a Distributed System?
        • Design Goals
        • Scaling Techniques
        • Types of Distributed Systems
      • Architecture
        • System Architectures
        • Example Architectures
      • Communication
        • Foundations
        • Remote Procedure Call
        • Message-oriented Communication
      • Coordination
        • Clock Synchronization
        • Logical Clock
      • Consistency and Replication
        • Introduction
        • Data-centric Consistency
        • Client-centric Consistency
    • Static Analysis
      • Intermediate Representation
      • Data Flow Analysis
      • Interprocedural Analysis
      • Pointer Analysis
      • Static Analysis for Security
      • Datalog-Based Program Analysis
      • Soundness and Soundiness
      • CFL-Reachability and IFDS
  • Web
    • โœ…Prerequisites
      • OWASP Top 10
        • 1. Broken Access Control
        • 2. Cryptographic Failures
        • 3. Injection
        • 4. Insecure Design
        • 5. Security Misconfiguration
        • 6. Vulnerable and Outdated Components
        • 7. Identification and Authentication Failures
        • 8. Software and Data Integrity Failures
        • 9. Security Logging and Monitoring Failures
        • 10. SSRF
      • HTTP
        • HTTP Status Codes
        • HTTP Headers
      • Burp Suite
        • Burp Intruder
        • Burp Extender
        • Burp Collaborator
      • Information Gathering
        • DNS
        • Git
        • Editor
        • Server
      • Bug Bounty Report Writing
    • File Upload
      • Webshell
      • IIS, Nginx, and Apache Vulnerabilities
      • .htaccess (Apache) / web.config (IIS)
      • Alternate Data Stream
      • Code Review: bWAPP Unrestricted File Upload
    • SQL Injection (SQLi)
      • Cheat Sheet
      • UNION Attacks
      • Examining the Database
      • Blind SQL Injection
      • WAF Bypass
      • Out-Of-Band (OOB)
      • Webshell and UDF
      • sqlmap
        • Code Review: Initialization
        • Code Review: tamper
    • Cross-Site Scripting (XSS)
      • Cheat Sheet
      • Reflected XSS
      • Stored XSS
      • DOM-Based XSS
      • XSS Contexts
      • CSP
    • CSRF and SSRF
      • Client-Side Request Forgery (CSRF)
        • XSS vs. CSRF
        • CSRF Tokens and SameSite Cookies
      • Server-Side Request Forgery (SSRF)
        • Attacks
        • Bypassing Restrictions
        • SSRF + Redis
    • XML External Entities (XXE)
    • Insecure Deserialization
      • Python Deserialization
      • PHP Deserialization
      • Java Deserialization
        • Shiro
        • FastJSON
        • WebLogic
    • HTTP Request Smuggling
    • OS Command Injection
      • Whitespace Bypass
      • Blacklist Bypass
      • Blind OS Command Injection
      • Lab 1: HITCON 2015 BabyFirst
      • Lab 2: HITCON 2017 BabyFirst Revenge
      • Lab 3: HITCON 2017 BabyFirst Revenge v2
    • โœ…Directory Traversal
    • HTTP Parameter Pollution
    • Server-Side Template Injection (SSTI)
    • LDAP Injection
    • Redis
      • Authentication
      • RCE
      • Mitigations
  • Pwn
    • Linux Exploitation
      • Protections
      • Shellcoding
        • Calling Convention
        • Null-free
        • Reverse Shell
        • ORW
      • ROP
        • Stack Alignment
        • ret2text
        • ret2syscall
        • ret2libc
        • ret2csu
        • BROP
        • SROP
        • Stack Pivot
      • ptmalloc
        • chunks
        • malloc() and free()
        • bins
        • tcache
      • UAF
      • Race Conditions
        • TOCTTOU
        • Dirty Cow
        • Meltdown
        • Spectre
      • Kernel
      • Appendix: Tools
        • socat
        • LibcSearcher-ng
        • OneGadget
    • Windows Exploitation
      • Classic
      • SEH
      • Egghunting
      • Unicode
      • Shellcoding
      • ROP
      • Appendix: Tools
        • ImmunityDbg
        • Mona.py
    • Fuzzing
      • AFL++
        • Quickstart
        • Instrumentation
        • ASAN
        • Code Coverage
        • Dictionary
        • Parallelization
        • Partial Instrumentation
        • QEMU Mode
        • afl-libprotobuf-mutator
      • WinAFL
      • Fuzzilli
  • Reverse
    • Bytecode
      • Python Bytecode
    • ๐Ÿ‘‘Z3 solver
    • angr
      • angr Template
Powered by GitBook
On this page
  • Intro
  • Setup
  • Step 1: supply ETH
  • Step 2 and 3: borrow stable coin (DAI, USDC) and buy ETH on Uniswap
  • Step 4 and 5: sell ETH on Uniswap and repay borrowed stable coin
  • Test

Was this helpful?

  1. Web3 Security Research
  2. DeFi
  3. Compound V3
  4. Interacting with Compound

Long and Short

PreviousLiquidationNextInterest Model

Last updated 2 years ago

Was this helpful?

Intro

Lending can be seen as leverage. For example, I predict ETH price is going up in the near future. I supply 10 ETH as collateral to Compound and borrow 300 DAI. I would buy more ETH using this 300 DAI I just borrowed, so that when ETH price indeed goes up my asset total value goes up even more. I will buy 300 DAI with my ETH balance and repay the loan, and I still have more ETH at hand because ETH price went up. These extra ETH is my profit. This is called "long ETH".

"Short ETH" is just the other way around. If we expect ETH price to drop, we can deposit DAI as collateral and borrow ETH. Then we sell these borrowed ETH and buy DAI. When the price of ETH does go down, we sell DAI and buy ETH, then pay back the loan. We will be left some DAI and that is our profit.

We will be writing functions to long ETH. It takes the following steps:

  1. supply ETH

  2. borrow stable coin (DAI, USDC)

  3. buy ETH on Uniswap

When the price of ETH goes up:

  1. sell ETH on Uniswap

  2. repay borrowed stable coin

Code:

Setup

Nothing special here:

CEth public cEth;
CErc20 public cTokenBorrow;
IERC20 public tokenBorrow;
uint public decimals;

Comptroller public comptroller = Comptroller(0x3d9819210A31b4961b30EF54bE2aeD79B9c9Cd3B);
PriceFeed public priceFeed = PriceFeed(0x922018674c12a7F0D394ebEEf9B58F186CdE13c1);

IUniswapV2Router private constant UNI = IUniswapV2Router(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
IERC20 private constant WETH = IERC20(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);

constructor(
    address _cEth,
    address _cTokenBorrow,
    address _tokenBorrow,
    uint _decimals
) {
    cEth = CEth(_cEth);
    cTokenBorrow = CErc20(_cTokenBorrow);
    tokenBorrow = IERC20(_tokenBorrow);
    decimals = _decimals;

    // enter market to enable borrow
    // we are going to supply ETH (cEth)
    address[] memory cTokens = new address[](1);
    cTokens[0] = address(cEth);
    uint[] memory errors = comptroller.enterMarkets(cTokens);
    require(errors[0] == 0, "Comptroller.enterMarkets failed.");
}

receive() external payable {}

Step 1: supply ETH

We deposit ETH into Compound as collateral, which is equivalent to minting cEth:

function supply() external payable {
    cEth.mint{value: msg.value}();
}

Step 2 and 3: borrow stable coin (DAI, USDC) and buy ETH on Uniswap

Compute how much DAI we can borrow:

function getMaxBorrow() external view returns (uint) {
    // This is the amount we can borrow in USD
    (uint error, uint liquidity, uint shortfall) = comptroller.getAccountLiquidity(
        address(this)
    );

    require(error == 0, "error");
    require(shortfall == 0, "shortfall > 0");
    require(liquidity > 0, "liquidity = 0");

    // Price is also in USD
    uint price = priceFeed.getUnderlyingPrice(address(cTokenBorrow));
    uint maxBorrow = (liquidity * (10**decimals)) / price;

    return maxBorrow;
}

Borrow DAI and swap DAI for WETH in Uniswap:

function long(uint _borrowAmount) external {
    // borrow DAI
    require(cTokenBorrow.borrow(_borrowAmount) == 0, "borrow failed");
    
    // buy WETH on Uniswap
    uint bal = tokenBorrow.balanceOf(address(this));
    tokenBorrow.approve(address(UNI), bal);
    address[] memory path = new address[](2);
    path[0] = address(tokenBorrow);
    path[1] = address(WETH);
    UNI.swapExactTokensForETH(bal, 1, path, address(this), block.timestamp);
}

Step 4 and 5: sell ETH on Uniswap and repay borrowed stable coin

function repay() external {
    // sell ETH on Uniswap
    address[] memory path = new address[](2);
    path[0] = address(WETH);
    path[1] = address(tokenBorrow);
    UNI.swapExactETHForTokens{value: address(this).balance}(
        1,
        path,
        address(this),
        block.timestamp
    );
    
    // repay borrowed tokens
    uint borrowed = cTokenBorrow.borrowBalanceCurrent(address(this));
    tokenBorrow.approve(address(cTokenBorrow), borrowed);
    require(cTokenBorrow.repayBorrow(borrowed) == 0, "repay failed");

    // Withdraw collateral ETH
    uint supplied = cEth.balanceOfUnderlying(address(this));
    require(cEth.redeemUnderlying(supplied) == 0, "redeem failed");

    // supplied ETH + supplied interest + profit (in token borrow)
}

Test

Test case:

it("should long", async () => {
    // used for debugging
    let tx
    let snap
    // supply
    tx = await testCompound.supply({
        from: ETH_WHALE,
        value: ETH_AMOUNT,
    })

    // long
    snap = await snapshot(testCompound, tokenBorrow)
    console.log(`--- supplied ---`)
    console.log(`liquidity: ${snap.liquidity.div(pow(10, 18))}`)
    console.log(`max borrow: ${snap.maxBorrow.div(pow(10, BORROW_DECIMALS))}`)

    const maxBorrow = await testCompound.getMaxBorrow()
    const borrowAmount = frac(maxBorrow, 50, 100)
    console.log(`borrow amount: ${borrowAmount.div(pow(10, BORROW_DECIMALS))}`)
    tx = await testCompound.long(borrowAmount, {
        from: ETH_WHALE
    })

    // update borrowed balance
    // await testCompound.getBorrowBalance()

    snap = await snapshot(testCompound, tokenBorrow)
    console.log(`--- long ---`)
    console.log(`liquidity: ${snap.liquidity.div(pow(10, 18))}`)
    console.log(`borrowed: ${snap.borrowed.div(pow(10, BORROW_DECIMALS))}`)
    console.log(`eth: ${snap.eth.div(pow(10, 18))}`)

    // accrue interest on borrow
    const block = await web3.eth.getBlockNumber()
    await time.advanceBlockTo(block + 100)

    // repay
    await tokenBorrow.transfer(testCompound.address, BORROW_INTEREST, {
        from: REPAY_WHALE
    })
    tx = await testCompound.repay({
        from: ETH_WHALE,
    })

    snap = await snapshot(testCompound, tokenBorrow)
    console.log(`--- repay ---`)
    console.log(`liquidity: ${snap.liquidity.div(pow(10, 18))}`)
    console.log(`borrowed: ${snap.borrowed.div(pow(10, BORROW_DECIMALS))}`)
    console.log(`eth: ${snap.eth.div(pow(10, 18))}`)
    console.log(`token borrow: ${snap.tokenBorrow.div(pow(10, BORROW_DECIMALS))}`)
})
โœ…
โœ…
Long and Short
defi-by-example/TestCompoundLong.sol at main ยท stakewithus/defi-by-exampleGitHub
TestCompoundLong.sol
defi-by-example/test-compound-long.js at main ยท stakewithus/defi-by-exampleGitHub
test-compound-long.js
Logo
Logo