By: Sissice
作者：Sissice

背景
Background

2024 年 4 月 24 日，据慢雾安全团队情报，BSC 链上的 YIEDL 项目遭攻击，攻击者获利约 30 万美元。慢雾安全团队对该攻击事件展开分析并将结果分享如下：

On April 24, 2024, according to the SlowMist security team intelligence, the YIEDL project on the BSC chain was attacked, and the attacker profited about 300,000 US dollars. The SlowMist security team conducted an analysis of the attack event and shared the results as follows:

(https://twitter.com/SlowMist_Team/status/1782962346039898473)

相关信息
Related Information

攻击者地址：
Attacker's address:

0x322696471792440499b1979e0a440491e870667a

被攻击合约地址：
Contract address under attack:

0x4edda16ab4f4cc46b160abc42763ba63885862a4

部分攻击交易：
Some attack transactions:

0x49ca5e188c538b4f2efb45552f13309cc0dd1f3592eee54decfc9da54620c2ec

0x3629ad588ac120163792e92b6c43bd4bdc5bf35cac66eb7f3a0267df93abc849

0x0a89b8670c40b4067b9522a5933c3bf8c44c968103aa642b04c65d49ad9e6457

0x5e468cba495e5f6165418fb9d87d824309c54261055425f33f588dd3b3abbcea

0x8710034dadecfc8c26f651c612f613fffdece6e2f9957b9ec8ab843218168c1d

0x9da398ed274c8cfa774b36003fa8c930d3430d0fc5889b5008830fd6463f68a9

0x2e3d4332f66a334e0170187011ed673dc222f95bf4443b618e08f8052437ef7a

0x5a15fdc57c35f2305aaa0bb95b109ad412b17406d737d137190fe5867393339d

0x8ef3765665cd849cdf9132ab37caf6aa0f891e1f7d9f418f86a6ab6ea38b6f5b

0xa9fa04b033afbed2218679aea92e9429a5f7839d0b4c65358ebf9ba20efcd021

攻击核心
Attack Core

本次事件的攻击核心是利用合约处理 redeem 函数调用时未能充分验证用户输入的外部参数。该参数是控制资产兑换的关键数据，通常包含特定的交易指令或路由信息。攻击者通过恶意构造这一外部参数，实现了未授权的资产转移。

The core of this attack event is that the contract did not fully verify the external parameters input by the user during the processing of the redeem function call. This parameter is a crucial data controlling asset exchange, typically including specific transaction instructions or routing information. Attackers maliciously constructed this external parameter, resulting in unauthorized asset transfers.

交易分析
Transaction Analysis

攻击者多次调用 redeem 函数，申请赎回数量为 0 的资产，此行为本身看似无害，因为赎回数量为零时通常不会触发任何实际的资金流动：

But by following the redeem function, it can be found that the function will traverse the list of assets allowed by the contract and, when the current asset is not the asset the user wants to receive, it will parse the dataList parameter and make an external call to the corresponding function in the 1inch Router to execute the asset exchange operation.

And because the dataList passed here has not been checked and verified, the attacker can construct malicious values to execute the unoswapTo function in the 1inch Router contract to perform arbitrary controllable token exchange operations.

As a result, the WBNB-ADA Token in the Yiedl BULL contract was exchanged for BNB to the attacker's address.

In this way, the attacker does not need to actually own any redemption shares to trigger token exchange operations controlled by the dataList parameter, repeatedly moving funds in the contract and profiting.

总结
Summary

本次攻击的核心在于函数未能充分验证用户输入的 dataList 参数，导致攻击者可以构造恶意的外部数据并利用 1inch 套走合约中的代币。慢雾安全团队建议项目方在开发中实施严格的参数验证机制，尤其是在涉及合约中的资金操作时，要确保所有外部调用均符合预期的行为规范，并对合约的逻辑进行彻底的安全审计，避免类似事件再次发生。

The core of this attack lies in the failure of the function to fully verify the dataList parameter input by the user, allowing attackers to construct malicious external data and use 1inch to siphon off tokens in the contract. The SlowMist security team recommends that projects implement strict parameter validation mechanisms during development, especially when it comes to financial operations in contracts, ensuring that all external calls comply with expected behavioral norms, and conducting thorough security audits of contract logic to prevent similar events from happening again.