ECVerifyLib

{
  "language": "Solidity",
  "sources": {
    "ECVerifyLib.sol": {
      "content": "pragma solidity ^0.4.0;\r\n\r\n\r\nlibrary ECVerifyLib {\r\n    // From: https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d\r\n    // Duplicate Solidity's ecrecover, but catching the CALL return value\r\n    function safer_ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal returns (bool, address) {\r\n        // We do our own memory management here. Solidity uses memory offset\r\n        // 0x40 to store the current end of memory. We write past it (as\r\n        // writes are memory extensions), but don't update the offset so\r\n        // Solidity will reuse it. The memory used here is only needed for\r\n        // this context.\r\n\r\n        // FIXME: inline assembly can't access return values\r\n        bool ret;\r\n        address addr;\r\n\r\n        assembly {\r\n            let size := mload(0x40)\r\n            mstore(size, hash)\r\n            mstore(add(size, 32), v)\r\n            mstore(add(size, 64), r)\r\n            mstore(add(size, 96), s)\r\n\r\n            // NOTE: we can reuse the request memory because we deal with\r\n            //       the return code\r\n            ret := call(3000, 1, 0, size, 128, size, 32)\r\n            addr := mload(size)\r\n        }\r\n\r\n        return (ret, addr);\r\n    }\r\n\r\n    function ecrecovery(bytes32 hash, bytes sig) returns (bool, address) {\r\n        bytes32 r;\r\n        bytes32 s;\r\n        uint8 v;\r\n\r\n        if (sig.length != 65)\r\n          return (false, 0);\r\n\r\n        // The signature format is a compact form of:\r\n        //   {bytes32 r}{bytes32 s}{uint8 v}\r\n        // Compact means, uint8 is not padded to 32 bytes.\r\n        assembly {\r\n            r := mload(add(sig, 32))\r\n            s := mload(add(sig, 64))\r\n\r\n            // Here we are loading the last 32 bytes. We exploit the fact that\r\n            // 'mload' will pad with zeroes if we overread.\r\n            // There is no 'mload8' to do this, but that would be nicer.\r\n            v := byte(0, mload(add(sig, 96)))\r\n\r\n            // Alternative solution:\r\n            // 'byte' is not working due to the Solidity parser, so lets\r\n            // use the second best option, 'and'\r\n            // v := and(mload(add(sig, 65)), 255)\r\n        }\r\n\r\n        // albeit non-transactional signatures are not specified by the YP, one would expect it\r\n        // to match the YP range of [27, 28]\r\n        //\r\n        // geth uses [0, 1] and some clients have followed. This might change, see:\r\n        //  https://github.com/ethereum/go-ethereum/issues/2053\r\n        if (v < 27)\r\n          v += 27;\r\n\r\n        if (v != 27 && v != 28)\r\n            return (false, 0);\r\n\r\n        return safer_ecrecover(hash, v, r, s);\r\n    }\r\n\r\n    function ecverify(bytes32 hash, bytes sig, address signer) returns (bool) {\r\n        bool ret;\r\n        address addr;\r\n        (ret, addr) = ecrecovery(hash, sig);\r\n        return ret == true && addr == signer;\r\n    }\r\n}"
    }
  },
  "settings": {
    "libraries": {},
    "optimizer": {
      "runs": 200,
      "enabled": true
    },
    "compilationTarget": {
      "ECVerifyLib.sol": "ECVerifyLib"
    }
  }
}