去中心化金融(DeFi)作为区块链生态当红项目形态，其安全尤为重要。从去年至今，发生了几十起安全事件
BlockSec作为长期关注DeFi安全的研究团队(https://blocksecteam
_toWETH函数：
function_toWETH(addresstoken)internalreturns(uint256){??//对于SUSHI，直接Sushimaker全部SUSHI转给Bar??if(token==sushi){????uintamount=IERC20(token)
看出什么亮点了吗？
SushiMaker里的转账逻辑都是：transfer(balanceOf(this))
我们可以分两个阶段来看convert的调用过程：第一个阶段：在?convert函数中SushiMaker拥有的是?SLP，它通过burnbalanceOf(this)实现将全部SLP换成两个底层代币第二个阶段：SushiMaker获得了burn来的底层代币，再拿burn得到的token去不同的交易池换wETH
你发现哪里有问题了吗？我们来看第二阶段的代码_toWETH：注意兑换的逻辑为：
uintamount=IERC20(token).balanceOf(address(this));
所以这个balanceOf(address(this))真的只有在第一阶段burn来的底层代币吗？Nononono~想一想，如果这里的token并不是底层代币，而是一个SLP，会发生什么？
IERC20(SLP).balanceOf(address(this))是SushiMaker拥有的所有SLP，既包含刚刚burn出来的，也包含原本SushiMaker就有的
如果底层代币是SLP，那第一阶段burn的是什么？答案是?SLP的SLP！
还记得吗？攻击者的目标是将SushiMaker诱到其创建的恶意交易池中交易，这个SLP1/WETH池不恰好是攻击者创建的，当攻击者调用convert(SLP1,wETH)时，SushiMaker由于上面这一漏洞会将其全部的SLP1都到SLP1/WETH池中换取WETH——正中下怀
SLP/WETH池一般都是不存在的，或是深度很浅的。攻击者其实也可以通过建立SLP1/SLP2来实现攻击，但是这样的话，还需要单独为SLP1、SLP2建立SLP1/WETH，SLP2/WETH，不如直接一步到位
1.4RealWorld
管你看没看懂，继续看就完了下面我们来看看攻击者在真实世界中到底做了什么吧？
攻击者地址：0x1925e832C22522E0d9947eE4677120b2f28E4cD4(https://etherscan.io/address/0x1925e832c22522e0d9947ee4677120b2f28e4cd4)
一组攻击包括很多笔交易，这里以对?MKR/WETH?池的攻击为例：SwapExactETHforTokens:?0xa8c4edd85727dApprove：0xf1fdd4cf4d8aaAddLiquidityETH:0x7340edca1a17fApprove:0x41a33f0c91b7cAddLiquidityETH:0x896f412f15a7aTransfer:0x0e8a76bf7295dConvert:0x4947b4f075f8eSwapExactETHForTokens:0x5f37bb3b97341RemoteLiquidityETH:0xdff10159275e0SwapExactTokensForETH:0xb8889bbdeb478
攻击者的一个完整的攻击周期：
序章：攻击准备
Step1：通过swapExactETHForTokens用一些ETH换取MKR，作为攻击的启动资金
Step2：将刚刚换到的MKR和ETH一起，向Sushi的MKR/wETH交易池中添加流动性，获得该池的SLP(MKR/wETH)
Step3：将刚刚换到的SLP和ETH一起，向Sushi的SLP/wETH交易池中添加流动性，获得新池的SLP(SLP/wETH)(后简称SLP')
Step4：将新生成的SLP'转给SushiMaker
这步有什么意义呢？因为攻击者后续会调用convert(SLP,wETH)，将SushiMaker.sol合约中存放的SLP'燃烧掉，换出SLP,wETH。如果SushiMaker.sol中没有SLP'就没法进行下去了
但是，实际复现过程中，我发现有没有这步其实都影响不大。因为上一步addLiquidity(SLP,wETH)是，一方面会mint出SLP'给攻击者，另一方面还会mint出一些SLP'给SushiMaker.sol，所以SushiMaker.sol中其实还是有一点SLP'的→现在攻击者手里有SLP'，其实他有两个不同的决策：
以太坊升级以来已有超336万枚ETH新存入质押 APR为8.64%:金色财经报道，Token.Unlock数据显示，自以太坊上海升级完成以来，已有约266万枚ETH解除质押，约336万枚ETH新存入质押，净质押余额约70.4万枚ETH。即以太坊上海升级完成以来的ETH新存入质押数已超过解除质押数。此外，当前约枚3.29万ETH处于待提款状态，质押APR为8.64%。[2023/5/14 15:02:20]
1.将SLP'转给SushiMaker，这样SushiMaker可以换出更多的SLP和wETH，下一步回到这个交易池将自己所有的SLP换成wETH2.不转SLP'给SushiMaker，因为之前创建SLP/wETH这个池的时候会mint一点点SLP'给SushiMaker，所以还是可以通过调用convert将SushiMaker存的SLP都换成wETH
第一种方式中，使SushiMaker拥有的SLP'更多，会换出更多的SLP和wETH，使得池中的滑点更大，SushiMaker能亏的SLP就更多，但是如果SushiMaker中本身存的SLP就不多，SLP/wETH深度也不大时，其实结果差不太多，都是几乎将SushiMaker搬空。总而言之，还是第一种方式更优，可以看出攻击者其实是有精心考虑过的
高潮：攻击SushiMaker
Step5：调用convert(SLP,wETH)，这一步中，SushiMaker会先将SLP'burn掉，换成SLP和wETH，再将自己所有的SLP都转成wETH，问题在于?SLP/wETH这个池是由攻击者创建的，池中的深度非常小，滑点极高，SushiMaker通过?swap将SLP换成wETH这步会血亏
尾声：获利
Step6：上一步中，SushiMaker在SLP/wETH这个池中血亏了大量的SLP，池中wETH巨值钱，此时攻击者只需要调用swap用一点点wETH就可以几乎将整个池子搬空
0x2.附录
2.1本次事件相关的攻击交易：[??{????"YFI/WETH":{??????"0x18be4ac177c5ada3522e3cafd6c40d750d4288a3a7b22e140521124074fed2ae":"SwapExactETHForTokens",??????"0xc8653ef0c4658acf3d44059babea07c62578769cac10176e61310f7af04e1597":"Approve",??????"0x18ed3e5efeec3e475501786541a4f7602340e5aa6bc6cbf24b9c9aa1062449ac":"AddLiquidityETH",??????"0x42d553b614d0a64ea2cfe95bf2a99d337c07f1b53ac4d7987966fc39817975e6":"Approve",??????"0x041463e755e91548b9d6dd1e61519b08f101ff96a44df969b33ee57996619a88":"AddLiquidityETH",??????"0x8a2d7926e50123459b7814c0e19b5ac59f7ce221cb5fa82f79d2c0c37ef7ef1f":"Transfer",??????"0xaa001ac10841c784954b0028192f0ea232bf84e390b964af98f1c49074ec4beb":"Convert",??????"0x08bbbeaf7cbd2649738812cf720042eb7ebe1411be2f7cf3ede41411dcbf8bc0":"SwapExactETHForTokens",??????"0x3952f24ef1e5dce37463edcf0f3902316131fb823d79946b96f2a2397a9cd25d":"RemoveLiquidityETH",??????"0x47c200fefd8c007d972b65b97dadf429c3e6e91359b7b49aaa66ee0fc4a555f4":"SwapExactTokensForETH"????},????"profit":"0.2558139ether"??},??{????"USDT/WETH":{??????"0x123ec6c44fa3baa70c66f583f8ee6bc6b6d2b4d39a1119ab8490d2c1120d4647":"Convert",??????"0x08bbbeaf7cbd2649738812cf720042eb7ebe1411be2f7cf3ede41411dcbf8bc0":"SwapExactETHForTokens",??????"0x42973ea279d0bda4222e4689709f86bdb12117dce14420f84f3e9cc6fd42ede2":"RemoteLiquidityETH",??????"0x30eab0a184f9a1ed6cee309754bb6536bd443fea567776a72b72f3ab911e0113":"SwapExactTokensForETH"????},????"profit":"0.1835604ether"??},??{????"MKR/WETH":{??????"0xa8c4edd85727d3d25401f0cbca1136982edb833f77ff0a93178b222063eb57a4":"SwapExactETHforTokens",??????"0xf1fdd4cf4d8aa073ff01876333cfeadeab2b87423664d1daa4cf36ad5e415587":"Approve",??????"0x7340edca1a17fc9e5a6587d6a89c0ed01c5d1f1d20cb19738ab993f6ef7b8b4d":"AddLiquidityETH",??????"0x41a33f0c91b7cd17edf888356dfb110d7744f593e432b54ec2f21aae19076aa0":"Approve",??????"0x896f412f15a7abb959c3c43b8cd9206720fc37f4eabeae336ba101670003e9db":"AddLiquidityETH",??????"0x0e8a76bf7295d9316704fde7f953eced612daa9ca7a70322248eeb8a7f508656":"Transfer",??????"0x4947b4f075f8e9f89f6364158b3d05a92cd72b7920c44c2150a0d12ba009a7a0":"Convert",??????"0x5f37bb3b9734175b605f6e02700c4b710e5e01622f30d822bcca227d91363d77":"SwapExactETHForTokens",??????"0xdff10159275e064dad2c7c79585d1f3c4fd60b73d843715e0cff1a2292730e99":"RemoteLiquidityETH",??????"0xb8889bbdeb478809c3781ccb1c8a16f9fa90b6844d180818b6e73a16963a5ddc":"SwapExactTokensForETH"????},????"profit":"1.9761631ether"??},??{????"KP3R/WETH":{??????"0xe5a025658cd28a688442a57a9b441980feeed8f5e7892064efc68966eb4253eb":"SwapExactETHForTokens",??????"0xe77e7e9d636c2b733d226693d95d06005ae2b5aa8532957240310225aa73e051":"Approve",??????"0x5ce8451f9f39f2d32ffbd943d38723a8da6fff59ece8f62caa84c4c2a311ede3":"AddLiquidityETH",??????"0x171b741bb7cdcafebdbed1c503eb33babc70c2e2e45b2b55330df3bc6d5c9eda":"Approve",??????"0x0ad658ebab282a26d67da0a97083a41c83d0eb1ab6d19a4adb3676b57fc3851c":"AddLiquidityETH",??????"0x676dd29fade2b93e5ca4b0da9d2b5e4ede86f69d26a6201440e359892360b096":"Transfer",??????"0x3b37a792edbb785b223a2b4f0971834083acd52503e54d00989a365bbc533627":"Convert",??????"0x4df5506fdc7616ff65b4ae3b93360e180c7b6f5e976914c4af04648ad6559817":"SwapExactETHForTokens",??????"0x07e56eaa7935fb341654ac20223b0d32fab006b3f34e372aecf6bce05c3f903f":"RemoveLiquidityETH",??????"0x8f4d9d676e9a12d07dcd0c8225e207df48f8cb575cdaa6d81c4b7124c3500510":"Approve",??????"0xac3c837c249fb68ceebd896a72e1e4e8cf355caf3f5fcd0bdc7df7c101ea0596":"SwapExactTokensForETH"????},????"profit":"1.8226875ether"??},??{????"YFI/WETH":{??????"0x1b0eb70bc4d2407745df416acf6e2c312d25ee63c7e8e1291545d66e23fbf704":"PreAttack",??????"0x8f6caabd4ecfad30793db76f60a7e28832a18e2bcf006c0ee3652063c7386778":"Convert",??????"0xe6d28052b55ab520a211daebbc67ee3aece6ae356044e9352fc82910214a038a":"Swap"????},????"profit":"-0.031382ether"??},??{????"AXS/WETH":{??????"0x375f5befeb1af976ebb09cf5539b3a3b9746b87153cfa96ba862deb8828970f1":"PreAttack",??????"0xed8508a18c347c3829024f7acb94056a78cc63152e2246ebd42b59cd86d0c8f9":"Convert",??????"0xd08eb264e39cd5dca8edb3684dfd36afb905aea9c47a43110b6c5c45bdb2f7d1":"Swap"????},????"profit":"1.349482ether"??},??{????"CRD/WETH":{??????"0xc6c86de784359a3813b31b4be5806a23f82fdd8d5cd9bd3a7379d33a413eb920":"PreAttack",??????"0x7d1b36019fb287867419dffb281b5ad73b37d8dc21abca47f7b618875842ef0a":"Convert",??????"0x8c14595b205cd04d1e5062a3efe47d3e4dae946eabe744e2d8350d6ba951495a":"Swap"????},????"profit":"1.325357ether"??},??{????"USDC/WETH":"Failed"??},??{????"COVER/WETH":"Failed"??},??{????"YAX/WETH":{??????"0x063bc5df97c0ec87d6c309b54fbc4e3ed13b22f5a115fb1170015e4e9d23cd3d":"PreAttack",??????"0x9537551d0db7ed6ae372c050c73cae1272f4d7e7847ea908d6e4d440809a871f":"Convert",??????"0x9f6bdf1c9065f5f5e5c71f32058093b7ac06e140c3a33db2f21cc8a5ff8a5d21":"SwapExactETHforTokens",??????"0x9281c35277ea6594924600d70b73077a4307973c540edb5b4ed534c7e25f2423":"Approve",??????"0xe2f682d8b4801061d504025f11b3032648a3b94019396f7b12749b162f8404cf":"RemoteLiquidityETH",??????"0xf6ea6c9eb92ca9aed70e8b4b03a6e5565a3a13df71a0aa527fa55607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A股收盘：深证区块链50指数下跌1.54%:金色财经消息，A股收盘，上证指数报3567.44点，收盘下跌0.73%，深证成指报14223.35点，收盘下跌1.27%，深证区块链50指数报3740.07点，收盘下跌1.54%。区块链板块收盘下跌1.38%，数字货币板块收盘下跌3.59%。[2022/1/11 8:40:56]
后续攻击者又尝试攻击Sushiswap的其他相关仿盘项目，如LuaSwap：
https://etherscan.io/tx/0xeacfed6fb18563c18b9af5cb0d3a5b13e97cf02026ef9a4cb625cc33580d02a7
但可能获利不多，只成功几笔就不了了之了
2.2本次事件后续结果：
在**#11351530**块，Sushi的管理员向攻击者喊话：
可以看到，好像有些延迟，攻击者的攻击依然持续了一段时间：
最后一条Convert中：
SushiMaker地址从0x6684977bBED67变成了0x280ac711bb99d：
Old：0x6684977bBED67e101BB80Fc07fCcfba655c0a64F??functionconvert(addresstoken0,addresstoken1)public{????//Atleastwetrytomakefront-runninghardertodo.????//限制只能EOA来调用该函数????require(msg.sender==tx.origin,"donotconvertfromcontract");????//获取相应SLPtoken合约的地址????IUniswapV2Pairpair=IUniswapV2Pair(factory.getPair(token0,token1));????//将SushiMaker中存有的全部SLP，转给交易池????pair.transfer(address(pair),pair.balanceOf(address(this)));????//Burn掉这些SLP换成两种token????pair.burn(address(this));????//分别将两种token找到相应的和wETH的交易对，全部转换为wETH????uint256wethAmount=_toWETH(token0)_toWETH(token1);????//将转换的到的全部wETH找wETH/SUSHI交易对换成SUSHI_toSUSHI(wethAmount);??}??function_toETH(addresstoken){????...????uintamountIn=IERC20(token).balanceOf(address(this));??}New：0x280ac711bb99dE7C73FB70fb6DE29846D5e4207F??functionconvert(addresstoken0,addresstoken1)public{????//Atleastwetrytomakefront-runninghardertodo.????require(msg.sender==tx.origin,"donotconvertfromcontract");????IUniswapV2Pairpair=IUniswapV2Pair(factory.getPair(token0,token1));????pair.transfer(address(pair),pair.balanceOf(address(this)));????(uintamount0,uintamount1)=pair.burn(address(this));????uint256wethAmount=_toWETH(token0,amount0)_toWETH(token1,amount1);_toSUSHI(wethAmount);??}??function_toETH(addresstoken,uintamountIn){????...??}
可以看到区别在于：代码第26行_toWETH限制了amount，这样修改以后就不会将SushiMaker中存的全部SLP都去池中换成wETH，而只是换取burn出的一部分
但是这样问题就解决了吗？其实还没有，时隔两个月，同样的地方，Sushiswap又中了见：amenda：SushiSwap攻击事件(2021年1月27号)分析(https://zhuanlan.zhihu.com/p/372058217)
0x3.参考
以小博大，简述SushiSwap攻击事件始末：https://www.chainnews.com/zh-hant/articles/726256718885.htm
Astokenpricerisesandreputationmends,Sushiswapfoilsmidnightexploit:?https://cointelegraph.com/news/as-token-price-rises-and-reputation-mends-sushiswap-foils-midnight-exploit
DeFi 概念板块今日平均涨幅为7.11%:金色财经行情显示，DeFi 概念板块今日平均涨幅为7.11%。47个币种中44个上涨，3个下跌，其中领涨币种为：MLN(+38.23%)、IDEX(+19.60%)、SWFTC(+18.89%)。领跌币种为：LBA(-3.86%)、AKRO(-3.36%)、DMG(-1.96%)。[2021/3/30 19:28:09]
AnevolutionofUniswapwithSUSHItokenomics：https://sushichef.medium.com/the-sushiswap-project-dd6eb80c6ba2
一文看懂Uniswap和Sushiswap：https://zhuanlan.zhihu.com/p/226085593
sokdecentralizedexchanges(dex)withautomatedmarketmaker(amm)protocols:?https://arxiv.org/abs/2103.12732
AttackingtheDeFiEcosystemwithFlashLoansforFunandProfit:?https://arxiv.org/abs/2003.03810
https://www.blocksecteam.com/
动态 | OGN今日正式上线BiKi 涨幅达200%:据官方公告，OGN（Origin Protocol）在BiKi 平台现已开放充值业务，并已开放OGN/USDT交易对，OGN当前涨幅200%，现报价0.3USDT。
据介绍，Origin起源的目标是实现真正的点对点商务，买卖双方可以直接交易，无需中介。目前，用户可以在Origin的旗舰商店及其合作伙伴应用上买卖商品和服务。市场运营商也可以在Origin的开源平台上开发创建自己的应用。Origin代币(OGN)是起源协议的一个重要组成部分，作为一种激励机制保证网络的健康和发展，让每一个使用者，贡献者成为利益的分享者。[2020/1/8]
行情丨HT在15分钟内涨幅超过3.00%:据火币全球站数据显示，HT/BTC在15分钟内出现剧烈波动，涨超3.00%，达到3.45%。当前报价为 2.36 美元，行情波动较大，请注意风险控制。[2019/5/12]
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