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ECDSA: Use unchecked arithmetic for the tryRecover function #4301

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Jun 8, 2023
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ECDSA: Use unchecked arithmetic for the tryRecover function #4301

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Use unchecked arithmetic for the ryRecover function
pcaversaccio Jun 2, 2023
08b10b7
Add changeset
pcaversaccio Jun 2, 2023
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5 changes: 5 additions & 0 deletions .changeset/four-adults-knock.md
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@@ -0,0 +1,5 @@
---
'openzeppelin-solidity': patch
---

`ECDSA`: Use unchecked arithmetic for the `tryRecover` function that receives the `r` and `vs` short-signature fields separately.
9 changes: 6 additions & 3 deletions contracts/utils/cryptography/ECDSA.sol
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Expand Up @@ -98,9 +98,12 @@ library ECDSA {
* _Available since v4.3._
*/
function tryRecover(bytes32 hash, bytes32 r, bytes32 vs) internal pure returns (address, RecoverError) {
bytes32 s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
uint8 v = uint8((uint256(vs) >> 255) + 27);
return tryRecover(hash, v, r, s);
unchecked {
bytes32 s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
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// We do not check for an overflow here since the shift operation results in 0 or 1.
uint8 v = uint8((uint256(vs) >> 255) + 27);
return tryRecover(hash, v, r, s);
}
}

/**
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