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pragma solidity 0.4.18;
/**
* @dev Pulled from OpenZeppelin: https://git.io/vbaRf
* When this is in a public release we will switch to not vendoring this file
*
* @title Eliptic curve signature operations
*
* @dev Based on https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d
*/
library ECRecovery {
/**
* @dev Recover signer address from a message by using his signature
* @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
* @param sig bytes signature, the signature is generated using web3.eth.sign()
*/
function recover(bytes32 hash, bytes sig) public pure returns (address) {
bytes32 r;
bytes32 s;
uint8 v;
//Check the signature length
if (sig.length != 65) {
return (address(0));
}
// Extracting these values isn't possible without assembly
// solhint-disable no-inline-assembly
// Divide the signature in r, s and v variables
assembly {
r := mload(add(sig, 32))
s := mload(add(sig, 64))
v := byte(0, mload(add(sig, 96)))
}
// Version of signature should be 27 or 28, but 0 and 1 are also possible versions
if (v < 27) {
v += 27;
}
// If the version is correct return the signer address
if (v != 27 && v != 28) {
return (address(0));
} else {
return ecrecover(hash, v, r, s);
}
}
}