1/ I saw many wrong tweets about the @picklefinance exploit. Let me try to explain it.

It's not an economic exploit. It's more like a traditional CTF combining all coincidence. More details in the following threads.

TL;DR 👇This precisely describes how the exploit works.
2/ tx: ethtx.info/mainnet/0xe72d…
and the screenshot of the whole exploit logic.
3/ from the screenshot, we can see that this exploit is very short. Let's divide them into 3 essential parts and focus on what they did actually. `swapExactJarForJar`, `earn()`, and `swapExactJarForJar` again.
4/ In first `swapExactJarForJar`, it let current DAI strategy deleverage DAI from Compound and send it back to pDAI Jar. In `earn()`, it turned DAI into cDAI as expected. In the second `swapExactJarForJar`, it withdrew cDAI back to controller and then put them into the fake Jar.
5/ There are actually 8 flaws utilized in this exploit. YET, there's one thing worth pointing out. This exploit only happens when these 8 flaws occur at the same time. So either 1 of 8 was fixed or didn't even exist, there wouldn't be this exploit.
6/ 8 flaws are here (ordered by the procedure of exploit, not severity):
1. no sanity check on address argument
2. allow to pass _target & _data openly
3. put withdrawForSwap in an unauthorized function
4. put delegatecall in an unauthorized function
5. whitelisted address has an arbitrary function
6. whitelisted address is authorized to an unauthorized function
7. public earn
8. allow to withdraw working asset from strategy

None of them was related to economic technique like flash loan.
8/ I would say what pickle intended to do was nothing wrong. They wanted to make `swapExactJarForJar` generic and user-friendly. The problematic part was that all 8 flaws HAPPEN AT THE SAME TIME, and all used not in an intended way. That's why I said it's like a traditional CTF.
9/ Trade-off of making generic is necessity with more care.
My always motto for smart contracts: simplicity makes perfect.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Jun-You Liu

Jun-You Liu Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @orbxball

5 Aug
1/ Me and @martinetlee accidentally dove into @iearnfinance yCRV yVault code and found some parts that aroused our concerns. We quickly had a discussion with @AndreCronjeTech. More details in the following thread. TL;DR Your WAIFU is SAFU.
2/ Although there is no current risk in the existing vault, we still want to record our discovery and point out some gotchas. We hope this document will be useful to future devs who plan to contribute to the yearn ecosystem.
3/ First discovery is "poisoning baby vault". It could potentially break a vault at the beginning. Yet, it can be detected and resolved if paying attention when a new vault is released.
Read 5 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!