69 lines
2.2 KiB
Solidity
69 lines
2.2 KiB
Solidity
pragma solidity ^0.5.0;
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/**
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* @title Elliptic curve signature operations
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* @dev Based on https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d
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* TODO Remove this library once solidity supports passing a signature to ecrecover.
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* See https://github.com/ethereum/solidity/issues/864
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* Source: https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/ECRecovery.sol
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*/
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library ECRecovery {
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/**
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* @dev Recover signer address from a message by using their signature
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* @param _hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
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* @param _signature bytes signature, the signature is generated using web3.eth.sign()
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*/
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function recover(bytes32 _hash, bytes memory _signature)
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internal
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pure
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returns (address)
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{
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bytes32 r;
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bytes32 s;
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uint8 v;
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// Check the signature length
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if (_signature.length != 65) {
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return (address(0));
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}
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// Divide the signature in r, s and v variables
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// ecrecover takes the signature parameters, and the only way to get them
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// currently is to use assembly.
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// solium-disable-next-line security/no-inline-assembly
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assembly {
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r := mload(add(_signature, 32))
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s := mload(add(_signature, 64))
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v := byte(0, mload(add(_signature, 96)))
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}
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// Version of signature should be 27 or 28, but 0 and 1 are also possible versions
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if (v < 27) {
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v += 27;
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}
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// If the version is correct return the signer address
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if (v != 27 && v != 28) {
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return (address(0));
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} else {
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// solium-disable-next-line arg-overflow
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return ecrecover(_hash, v, r, s);
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}
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}
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/**
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* @dev prefix a bytes32 value with "\x19Ethereum Signed Message:" and hash the result
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*/
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function toEthSignedMessageHash(bytes32 _hash)
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internal
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pure
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returns (bytes32)
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{
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// 32 is the length in bytes of hash,
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// enforced by the type signature above
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return keccak256(
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abi.encodePacked("\x19Ethereum Signed Message:\n32", _hash)
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);
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}
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}
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