Storage Proofs
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Submission Details
Severity: low
Invalid

Missing Storage Slot Existence Checks in VerifierV1

ngochungp295

Summary

The verifier fails to check if storage slots exist, risking incorrect parameter extraction

Vulnerability Details

In ScrvusdVerifierV1.sol, the _extractParametersFromProof loop assumes all storage slots (e.g., total_debt, total_idle) exist. Missing slots return 0, leading to invalid parameters.

// Extract account proof
Verifier.Account memory account = Verifier.extractAccountFromProof(
SCRVUSD_HASH,
stateRoot,
proofs[0].toList()
);
require(account.exists, "scrvUSD account does not exist");
​
// Extract slot values
uint256[PARAM_CNT] memory params;
for (uint256 i = 1; i < PROOF_CNT; i++) {
@> Verifier.SlotValue memory slot = Verifier.extractSlotValueFromProof(
@> keccak256(abi.encode(PARAM_SLOTS[i])),
account.storageRoot,
proofs[i].toList()
);
// Slots might not exist, but typically we just read them.
params[i - 1] = slot.value;
}
​
return params;
}

Impact

risking zero values for critical parameters.

Tools Used

Manual review, Slither.

Recommendations

// In ScrvusdVerifierV1.sol's _extractParametersFromProof
for (uint256 i = 1; i < PROOF_CNT; i++) {
Verifier.SlotValue memory slot = Verifier.extractSlotValueFromProof(...);
require(slot.exists, "Slot missing"); // Add this check
params[i - 1] = slot.value;
}
Updates

Lead Judging Commences

0xnevi Lead Judge 3 months ago
Submission Judgement Published
Invalidated
Reason: Incorrect statement
Assigned finding tags:

[invalid] finding-slot-not-check-verifierv1-v2

- Looking at the OOS `StateProofVerifier` and `MerklePatriciaProofVerifier` contract that extracts the slot, the `exists` flag will be flagged as true as long as a non-zero length value is returned as seen [here](https://github.com/curvefi/curve-xdao/blob/3ff77bd2ccc9c88d50ee42d2a746fc7648c7ff2c/contracts/libs/StateProofVerifier.sol#L133C13-L136). From the `MerklePatriciaProofVerifier.extractProofValue`, the minimum length returned will be 1 as represenetd by `bytes(0)`. So this seems to be purely a sanity check that might not even be required. - A slot with zero values is only allowed when the proof provided by the prover correctly proofs that such values are included within the Merkle-Patricia-Tree. The values fetched from mainnet from the V3Vault stored in the merkle trie is likely checked before hand and aggregated into the MerkleTree.

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