Background: The basic development platform indicated that security problems were found in the pre-built smart contracts, and all tokens deployed by using the pre-built smart contracts were affected. For the specific affected contract code version, please refer to the tokens on the main network of the month, according to the information of the slow fog security team. It is precisely because of this vulnerability that the attacker made a profit of about 10,000 US dollars. At present, many token contracts with vulnerabilities are still being attacked, and the slow fog security team immediately intervened and analyzed and shared the results as follows. Knowledge acquisition is the standard of meta-transaction. Users can entrust the execution of a transaction to a third party, usually called a repeater or a repeater. Usually, the address of the direct caller in the contract is obtained by using, but if it is used as a repeater role, it will truncate the incoming and obtain the last byte as the address of the direct caller of the transaction. It is an intelligent contract library whose function is to allow multiple function calls to be executed in batches, thus reducing the transaction cost. This library is usually used to optimize performance and users. Experience, especially when multiple reading operations are needed, it can be seen from the code that the library used in the contract with loopholes in the project is to execute other functions in the contract that refer to the library by calling functions circularly. The root cause of the loophole is that the token contract uses the judgment that the library attacker calls the functions of the token contract to execute other functions in the contract, such as burning tokens, and finally resolves the caller of the function as the last malicious one. Bytes, therefore, the attacker successfully deceived the contract and made it mistake the caller for the address of other users, which led to the burning of other users' tokens. Here, the attack transaction is analyzed as an example. The attacker first used a token exchanged in the pool and then called the function of the contract to construct a malicious function to call the token contract. At this time, the token contract will execute the function of the token contract according to the malice introduced by the attacker and burn the tokens in the pool address because the pool was dropped in the previous step. A large number of tokens in the child make the price of tokens rise instantly, so the attacker can finally reverse the tokens obtained in the first step and empty the coins in the pool. After analyzing the signature verified in the function of the contract, he will use the interactive token address, in which the attacker passes in the function of the token contract because he signed the function of the function, and the value passed in by the function is why it is not in the value passed in the function. This is because the underlying processing calls will truncate the needs according to the offset. The key value and the offset set in the value passed in by the attacker is a numerical value, so the value just intercepted is specific. You can refer to the description in. Because the function of the function is signed, the function of the token contract will be called according to the value constructed by the attacker, in which the function is rewritten by the library, so the address of the contract is actually passed, which finally leads to the judgment that the returned value is the last byte passed in, that is, the address of the pool. Conclusion The root cause of this attack lies in At the same time, the contract refers to the function that an attacker can insert malicious exploitation into the forwarding request to manipulate any user's token through the judgment of the trusted transponder and the analysis in the sub-call. The slow fog security team suggests that the project party should not use it at the same time when writing the token contract, and if the expected demand needs to quote it at the same time, it must check whether the length is in line with the expectation or use the latest official version of the release details mitigation tool that refers to the attacker's address to attack 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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