add basic ethereum signing message methods

This commit is contained in:
Ricardo Guilherme Schmidt 2018-04-26 01:03:55 -03:00
parent 37135766e7
commit 6600ee5ccf
1 changed files with 77 additions and 0 deletions

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@ -0,0 +1,77 @@
pragma solidity ^0.4.21;
/**
* @notice Uses ethereum signed messages
*/
contract MessageSigned {
constructor() internal {
}
/**
* @notice recovers address who signed the message
* @param _signHash operation ethereum signed message hash
* @param _messageSignature message `_signHash` signature
*/
function recoverAddress(
bytes32 _signHash,
bytes _messageSignature
)
pure
internal
returns(address)
{
uint8 v;
bytes32 r;
bytes32 s;
(v,r,s) = signatureSplit(_messageSignature);
return ecrecover(
_signHash,
v,
r,
s
);
}
/**
* @notice Hash a hash with `"\x19Ethereum Signed Message:\n32"`
* @param _hash Sign to hash.
* @return signHash Hash to be signed.
*/
function getSignHash(
bytes32 _hash
)
pure
internal
returns (bytes32 signHash)
{
signHash = keccak256("\x19Ethereum Signed Message:\n32", _hash);
}
/**
* @dev divides bytes signature into `uint8 v, bytes32 r, bytes32 s`
*/
function signatureSplit(bytes _signature)
pure
internal
returns (uint8 v, bytes32 r, bytes32 s)
{
// The signature format is a compact form of:
// {bytes32 r}{bytes32 s}{uint8 v}
// Compact means, uint8 is not padded to 32 bytes.
assembly {
r := mload(add(_signature, 32))
s := mload(add(_signature, 64))
// Here we are loading the last 32 bytes, including 31 bytes
// of 's'. There is no 'mload8' to do this.
//
// 'byte' is not working due to the Solidity parser, so lets
// use the second best option, 'and'
v := and(mload(add(_signature, 65)), 0xff)
}
require(v == 27 || v == 28);
}
}