add reentrancy blogpost

_posts/2024-08-31-reentrancy_attack.md

@@ -0,0 +1,35 @@
+---
+title: Reentrancy Attacks Explained
+author: chatgpt
+---
+A **reentrancy attack** is not food—it's a type of security vulnerability that can occur in computer programs, especially in **smart contracts** on blockchain platforms like Ethereum.
+
+### What is a Reentrancy Attack?
+
+A reentrancy attack exploits the way a smart contract handles external calls to other contracts. Here's how it typically works:
+
+1. **Smart Contract Makes an External Call**: A smart contract (let's call it **Contract A**) sends a message or calls a function on another contract (let's call it **Contract B**). During this call, **Contract A** is in a temporary, incomplete state.
+
+2. **Malicious Contract Exploits Reentrancy**: If **Contract B** is malicious or controlled by an attacker, it can use this opportunity to make a recursive call back to **Contract A** before the initial call is finished and before the state of **Contract A** is updated.
+
+3. **Reentrant Call Drains Funds or Manipulates State**: The recursive call allows the attacker to manipulate the state of **Contract A** in a way that benefits them. For example, if **Contract A** was handling money transfers, the attacker could repeatedly call back into **Contract A** and withdraw funds multiple times before **Contract A** updates its balance.
+
+### How Does This Relate to Smart Contracts?
+
+In smart contracts, reentrancy attacks can be particularly damaging because:
+
+- **Lack of State Update Before the Reentrant Call**: If the contract does not update its state (e.g., deducting the balance of a user after a withdrawal) before making an external call, an attacker can drain the contract's funds.
+- **Decentralization and Irreversibility**: Blockchain transactions are irreversible, making it very hard to recover funds once they have been stolen.
+
+### Example of a Reentrancy Attack
+
+A famous example of a reentrancy attack is the attack on **The DAO** in 2016, where an attacker exploited a reentrancy vulnerability to drain about **$60 million** worth of Ether from the DAO smart contract.
+
+### Preventing Reentrancy Attacks
+
+To prevent reentrancy attacks, developers can:
+
+- **Use the Checks-Effects-Interactions Pattern**: Update the contract's state variables before making any external calls.
+- **Implement Reentrancy Guards**: Use special coding patterns or libraries (like OpenZeppelin's `ReentrancyGuard` in Solidity) to prevent functions from being called recursively.
+
+In summary, a reentrancy attack is a cybersecurity exploit related to smart contracts and has nothing to do with food. It's a critical concept in the world of blockchain development and security.