Precompile 0x0100 (RIP-7212) returns empty returndata in eth_sendTransaction, but works with eth_call

[nebasuke]

Likely combine this with: #558

Discussed in https://github.com/NomicFoundation/hardhat/discussions/6629

^{Originally posted by craterface77 April 24, 2025} Hello! I'm using Hardhat v2.22.18 with the option enableRip7212: true in hardhat.config.ts.

In my tests, I encountered unexpected behavior when calling precompile 0x0100 (P-256 / RIP-7212):

Behavior • When directly calling eth_call on a contract, where staticcall(0x0100, ...) is used, the correct returndata = 0x...01 (32 bytes) is returned. • But when calling the same method through a real transaction (eth_sendTransaction) — returndata is empty (0x), although success == true.

Context: I call 0x0100 from the WebAuthnValidator smart contract inside EntryPoint.handleOps(...). Here is an example of a Solidity call:

(bool success, bytes memory returndata) = address(0x100).staticcall(
abi.encode(h, r, s, qx, qy)
);

The arguments h, r, s, qx, qy are the same in both cases.

What I tried • I made sure that everything works with eth_call. • I made sure that all values ​​are valid (external signature validation is confirmed). • I put console.logBytes(...) before the call - everything matches. • I see the same thing on the OP Sepolia and Citrea networks: eth_call works, but tx returns an empty returndata.

Expected behavior

I expect 0x0100 to return not only on eth_call, but also in the actual transaction (eth_sendTransaction) if enableRip7212: true is enabled.

Possible explanation

It seems that the precompile is only enabled on the eth_call execution path, and not on the block simulation (tx-runner / mining path). If so, is there a fix planned?

// Setup in hardhat.config.ts
hard hat: { 
hardfork: "cancun", 
enableRip7212: true
}

// In test
await webAuthnValidator.validateUserOp(...) // eth_call → success
await entryPoint.handleOps(...) // eth_sendTransaction → returns 0x from 0x0100

Thank you!