On April, the government issued an important security alert to the community, pointing out that there may be the risk of arbitrary address spoofing attacks when using standards and classes in project integration. This incident was analyzed technically at the first time and the security precautions were summarized. I hope that the follow-up projects can take it as a warning to build a security line for the blockchain industry. An attack transaction analysis. Because there are a series of attack transactions related to this vulnerability, we choose one of the attack transactions to analyze the attacker's address attack. Transaction attack flow: firstly, the attacker exchanged about 10 coins, then the attacker constructed malicious parameters and called a function. When calling the function, the function of the contract was maliciously triggered, and then the remaining function that triggered the execution of the contract was used to destroy the tokens in the pool. Second, vulnerability analysis. First of all, this attack mainly involved several aspects. After careful construction, we can find relevant inheritance from the token contract, which provides a virtual ability to allow users to entrust a third party to execute transactions for reduction. When the transaction is submitted at low cost, the address will be added to the token contract. The token contract inherits that when the contract is called, it will check the data and shift it to the right to truncate the last byte. As expected, it is a method to transform a single function call into calling multiple functions in sequence in the same contract. It accepts an array of user-coded calls and executes this function on its own contract, traversing the call array and executing each operation. This allows users to combine their own series of operations and order them in the same transaction. It is not necessary to define some operation combinations in advance in the protocol. Its main purpose is also to save the attacker who has been carefully constructed from calling the function and passing in relevant parameters. We can format the values accordingly, and conclude that the attacker obtains a new value through the current offset operation and passes the new value to the function. The new first byte is the selector parameter of the function, and the address in this line is added to the address correspondence at the end at the beginning of construction by calling the function. The liquidity pool of is the expected liquidity pool address mentioned earlier. The reason why it became the liquidity pool address just mentioned is that it was originally a contract address. In order to judge whether it is credible, it will be set to the last byte of three. The security suggestion is that the root cause of this attack is not designed for the external call that the attacker added the relevant parameters in the function, that is, the function of this event will also attach the relevant parameters in the function, thus allowing the attacker to cheat and attack. The attacker can imitate the call of any address by calling the related function, and finally destroy the tokens in the pool by authorizing. The following mitigation and preventive measures can be taken for this incident. The repaired new version and the suffix length with data of the new version are used to identify the expected suffix length, so anyone from the trusted function will be identified and adapted. The following is the comparison diagram of the version and the updated version. It is forbidden to call any contract to prevent the use of it. Compared with the solution, this method still allows the following comparison diagram of the related version and the updated version through the contract. 比特币今日价格行情网_okx交易所app_永续合约_比特币怎么买卖交易_虚拟币交易所平台

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