Cyfrin Updraft 🟩 ✓
@CyfrinUpdraft · Start learning for free: · joined 20 Sep 2023
Teaching the next generation of web3 developers. 150+ hours of Smart Contract Development and Security Courses, completely for Free. Powered by @cyfrin
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@CyfrinUpdraft reentrancy hiding in a refund function is almost poetic. the exact moment a protocol is trying to give money back is when it loses everything
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Reentrancy is still one of the most common vulnerabilities in production contracts. Understanding it means understanding Solidity's execution model at a fundamental level.
Learn to find and exploit bugs like this in the Security and Auditing course on Updraft, completely free:
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The fix is simple. Update state BEFORE making the external call:
```
players[playerIndex] = address(0);
emit RaffleRefunded(playerAddress);
payable(msg.sender).sendValue(entranceFee);
```
This is called Checks-Effects-Interactions. If the attacker reenters, the require fails
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The attacker deploys a contract that:
→ Enters the raffle with one address
→ Calls `refund` to get their entrance fee back
→ In its `receive`/`fallback` function, calls `refund` again
→ Repeats until the contract is empty
Each loop iteration drains one more entrance fee.
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The vulnerable code:
`sendValue` transfers ETH to `msg.sender` BEFORE `players[playerIndex]` is set to `address(0)`. So when the caller receives ETH, they can call `refund` again and the require checks still pass. https://t.co/UqttnOzUCQ
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The `refund` function in PuppyRaffle sends ETH before updating state.
That's textbook reentrancy. Here's exactly how an attacker drains the entire contract. 🧵
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Reentrancy has drained hundreds of millions from smart contracts. The original DAO hack. Countless DeFi protocols since.
It all comes down to one mistake: making an external call before updating state. 🧵
1.6K views · 26 likes
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Most people stake ETH and stop there.
But you can stack yield on top of yield by routing through Balancer and Aura Finance.
Here's how rETH holders can earn BAL, AURA, and RPL on top of their staking rewards. 🧵
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Most Solidity devs have never manually emitted an event using assembly.
But gas-optimized contracts do it all the time. Here's how log4 actually works at the EVM level. 🧵
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@CyfrinUpdraft This got me thinking i should stop learning Solidity for Solana https://t.co/Cw4N4T5bzC
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Join thousands of developers already learning on Updraft:
https://t.co/6CpACWCLUo
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The Solana Development Course has dropped on Updraft.
12 programs. Native Rust + Anchor. Security CTFs.
Completely free. https://t.co/hTDLUPbKtI
26.4K views · 495 likes
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Growth & engagement
How the posts we collected actually performed: views and reaction rate post by post, what the audience did with them, and where the follower count goes.
Views per post
26.4K19 Jan
1.5K
353
1.1K11 Jun
1.3K12 Jun
1.6K13 Jun
4.1K14 Jun
875
564
916
741
2715 Jun
Last 12 collected posts, oldest on the left. The scale is logarithmic: one post can outrun the rest a hundred times over.
Engagement rate per post
2.19%19 Jan
2.01%
1.70%
1.65%11 Jun
1.70%12 Jun
1.82%13 Jun
1.36%14 Jun
0.69%
0.53%
0.55%
0.94%
0.00%15 Jun
Reactions — likes, reposts, replies and quotes — divided by views.
What the audience does
Likes70.2%656 in total
Reposts6.2%58 in total
Replies5.0%47 in total
Bookmarks18.6%174 in total
Share of every reaction we collected for this account. Replies mean argument, reposts mean endorsement, bookmarks mean the post was worth keeping.
The follower curve appears once this account has two daily snapshots — we take one a day, and this one is on its first.
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