Smart contracts are customized programs that are often used to automate the execution of an agreement so that all parties may be confident in the result without having to rely on one another or any middlemen. Smart contracts are specialized programs that are kept on a blockchain. A smart contract ensures that its execution will perfectly match the logic it contained when it was first drafted. And once that planned logic has been carried out, the network’s ultimate state will remain immutable.

But regrettably, the proper execution of the smart contract code does not ensure its total security. In fact, an examination of the current smart contracts reveals that a sizeable portion of them are in fact weak. In this post, we will discuss the most prevalent smart contract security challenges and flaws, as well as how to deal with them in order to improve the security of your protocol.

How smart contract vulnerabilities affect users?

Money loss is without a doubt the most apparent result of a breach because it is simple to determine how much the protocol and its users have lost. However, a less evident but sometimes far more significant effect of any exploit is loss of credibility.

All smart contract security flaws eventually lead to exploits, harming the protocol’s, its owners’, and the project team’s reputation. Furthermore, it reduces overall trust in the industry, causing greater fear and mistrust.

That is why smart contract security must be taken seriously. A security audit is one of the most important elements in this process. A good security audit performed by a credible, professional business allows you to uncover and eradicate any potential dangers and vulnerabilities in your smart contracts. As a result, you will improve the security of your protocol and avoid potential attacks.

Top 5+ key smart contract vulnerabilities and their solutions

Here is a list of several potential smart contract vulnerabilities that are discovered and fixed by smart contract auditing.

Re-entrancy Attacks

This is most likely the most well-known issue on the list.

When invoking an external contract function, keep in mind that this contract may in turn invoke your contract function (creating sort of an invocation loop).

This can be harmful if, for example, you are sending funds to an external account (which also happens to be an external contract) but did not update its balance before doing so. The external contract will receive the same amount of dollars each time it “re-enters” your function. By the end of the execution, you will have most likely sent many times the amount you meant to send.

Solution: You may either use the “Non reentrancy” pattern to your sensitive functions (there is an openZepelin contract you can use) or simply implement your functions as follows:

Check: check the input settings, access rights, and so forth…

Update: make changes to the state variables.

Interact: Call the external contracts / accounts.

Front-running Attacks

Ethereum is a decentralized network that requires many miners to validate and add blocks to the ledger. The transactions that users desire to contribute to the blockchain will be accessible to those miners.

If your dapp rewards the first user who submits certain information (secret info or similar), a miner could simply wait for an honest user to submit the information, let the transaction sit in the transaction pool, create its own transaction using the secret info originally provided by the honest user, and receive the reward instead of him/her.

Solution: There is no magic solution for this; simply keep it in mind when developing your app…

Replay Signatures Attacks 

Signatures allow one account to send the transactions of another account to the blockchain. The original account will sign a message, and the delivery account will send the message to a smart contract, so that the transaction fees are paid by the delivery account rather than the original account.

Of course, your smart contract must include functions for validating signatures and doing the necessary operations.

However, if a signed message is valid and your smart contract executes its content, keep in mind that whoever has access to it (literally anyone monitoring the blockchain) could send it multiple times. It means that your smart contract functionality could be executed multiple times for the same message, which was not the original account’s intention when it signed the message.

Solution: Include a nonce for each account in the signed messages. Messages signed by the same account with a nonce that has already been used are not accepted. Every time an account signs a new message, the nonce must be incremented. The EIP-712 standard can assist you in this regard.

Loop Through Long Arrays

If you’re used to working with other programming languages, you might be inclined to use arrays more than you should.

Keep in mind that executing functions on Ethereum costs gas (money), and transactions, by definition, have a gas limit (the gas limit of a single block). If your smart contract employs a very large array, and you need to iterate through it, you may surpass the gas limit, rendering the function un-executable….

Solution: When you foresee a large list of values, always try to use mappings.

Wrong Inheritance

Solidity allows for many inheritances, which introduces the ambiguity known as the “Diamond Problem.” In other words, if numerous parent contracts implement the same function, which one will your contract inherit?

Solidity employs C3 Linearization to determine the relative importance of parent contracts. If you do not pay attention, you may exhibit surprising behaviors.

Solution: You must comprehend how “C3 Linearization” works. As a general rule, add your parent contracts in the order of most broad to most specialized.

Undefined Randomness

Smart contracts, by definition, must be deterministic, returning the same result every time we run them, which means that randomness is also not conceivable.

Solution: The simplest solution would be to not include any randomization in your smart contract at all, but if you must, it will depend on how sensitive the random value must be. To get secure randomization, you might utilize global variables (block timestamp, block number, etc.) or an oracle like chainlink.

Conclusion,

Writing a completely secure smart contract is a difficult and time-consuming undertaking. However, no matter how flawless the contract appears to be, it still requires a rigorous security check before being broadcast on the network.

The reason for this is that there are several smart contract flaws that even experienced developers can easily overlook. However, even simple vulnerabilities can result in enormous protocol exploitation and financial damage. As a result, we strongly advise you to execute at least two smart contract audits to strengthen your protocol security and prevent potential attacks.

Please email us at hello@satom.vc if you are looking for a credible auditor. Experts from Satom will assist you with smart contract audits. Let’s work together to create secure projects!