UTF8 Replacement bytes "EFBFBD" in Revert error reason
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Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 25/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- typescript
- Domain
- backend-api-design
Research direction
Start by tracing how revert data moves through the provider, including the ethers fetchJson path and the Flashbots Relay response. Determine where EFBFBD replaces the original byte, then verify that the revert payload remains valid ABI-encoded data with the expected selector and two uints.
Written by the indexing model from the issue text.
Description
Unable to decode the revert error from Simulation (and probably from real txs too).
What I've noticed when I decode the revert string to HEX, is that it contains a lot of "EFBFBD" bytes:
"EFBFBD" is used as a standard UTF8 replacement bytes if the source byte cannot be encoded into UTF8:
https://blog.gdssecurity.com/labs/2015/2/18/when-efbfbd-and-friends-come-knocking-observations-of-byte-a.html
As you can see it couldn't encode 9C.
If you replace EFBFBD with any random byte (like "FF") - then you have a proper length ABI-Encoded custom error (with 4 bytes in the beginning, and 32+32 bytes two uints after).
I'm not sure where this replacement happens - on the Ethers side (in fetchJson they use toUTF8 encoding) or on Flashbots Relay side.
But if it happens on Ether's side - maybe we can use another connector?
- Dominant language
- TypeScript
- Stars
- 568
- Forks
- 212
- PR merge metrics
- No merged PRs in 30d
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