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playing with authentification and Solidity
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pragma solidity ^0.6.0; | |
// SPDX-License-Identifier: MIT | |
contract AuthOracle { | |
} | |
// hash | |
// https://solidity-by-example.org/hashing/ | |
// event | |
// https://hackernoon.com/how-to-use-events-in-solidity-pe1735t5 | |
// public function call with signature | |
// check(string memory) https://rinkeby.etherscan.io/tx/0xe39d7a31d49c48aacc1c8b81ba54b8cd16e5cf8d50d1f3878e2846b8ac5ff56d | |
// | |
// verify signed message | |
// https://solidity-by-example.org/signature/ | |
contract Auth { | |
address public owner; | |
bytes32 key = keccak256("testabc"); | |
using SafeMath for uint256; | |
AuthOracle oracle; | |
constructor() public { | |
} | |
modifier verify(string memory _key) { | |
bytes32 hashed = keccak256(abi.encodePacked(_key)); | |
require(key == hashed, "Auth: You are not allowed"); | |
_; | |
} | |
modifier requireWorks() { | |
uint256 timestamp = block.timestamp; | |
for(uint256 i=0;;i++){ | |
uint256 sha = uint256(keccak256( | |
abi.encodePacked(msg.data,timestamp, i) | |
)); | |
if(sha % 20 == 0) { | |
break; | |
} | |
} | |
_; | |
} | |
function setOracle(address _oracle) public { | |
oracle = AuthOracle(_oracle); | |
} | |
function check(string memory _key) requireWorks() verify(_key) public { | |
} | |
function change (string memory _key) verify(_key) public { | |
bytes32 hashed = keccak256(abi.encodePacked(_key)); | |
key = hashed; | |
} | |
} | |
library SafeMath { | |
/** | |
* @dev Returns the addition of two unsigned integers, with an overflow flag. | |
* | |
* _Available since v3.4._ | |
*/ | |
function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) { | |
uint256 c = a + b; | |
if (c < a) return (false, 0); | |
return (true, c); | |
} | |
/** | |
* @dev Returns the substraction of two unsigned integers, with an overflow flag. | |
* | |
* _Available since v3.4._ | |
*/ | |
function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) { | |
if (b > a) return (false, 0); | |
return (true, a - b); | |
} | |
/** | |
* @dev Returns the multiplication of two unsigned integers, with an overflow flag. | |
* | |
* _Available since v3.4._ | |
*/ | |
function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) { | |
// Gas optimization: this is cheaper than requiring 'a' not being zero, but the | |
// benefit is lost if 'b' is also tested. | |
// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522 | |
if (a == 0) return (true, 0); | |
uint256 c = a * b; | |
if (c / a != b) return (false, 0); | |
return (true, c); | |
} | |
/** | |
* @dev Returns the division of two unsigned integers, with a division by zero flag. | |
* | |
* _Available since v3.4._ | |
*/ | |
function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) { | |
if (b == 0) return (false, 0); | |
return (true, a / b); | |
} | |
/** | |
* @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag. | |
* | |
* _Available since v3.4._ | |
*/ | |
function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) { | |
if (b == 0) return (false, 0); | |
return (true, a % b); | |
} | |
/** | |
* @dev Returns the addition of two unsigned integers, reverting on | |
* overflow. | |
* | |
* Counterpart to Solidity's `+` operator. | |
* | |
* Requirements: | |
* | |
* - Addition cannot overflow. | |
*/ | |
function add(uint256 a, uint256 b) internal pure returns (uint256) { | |
uint256 c = a + b; | |
require(c >= a, "SafeMath: addition overflow"); | |
return c; | |
} | |
/** | |
* @dev Returns the subtraction of two unsigned integers, reverting on | |
* overflow (when the result is negative). | |
* | |
* Counterpart to Solidity's `-` operator. | |
* | |
* Requirements: | |
* | |
* - Subtraction cannot overflow. | |
*/ | |
function sub(uint256 a, uint256 b) internal pure returns (uint256) { | |
require(b <= a, "SafeMath: subtraction overflow"); | |
return a - b; | |
} | |
/** | |
* @dev Returns the multiplication of two unsigned integers, reverting on | |
* overflow. | |
* | |
* Counterpart to Solidity's `*` operator. | |
* | |
* Requirements: | |
* | |
* - Multiplication cannot overflow. | |
*/ | |
function mul(uint256 a, uint256 b) internal pure returns (uint256) { | |
if (a == 0) return 0; | |
uint256 c = a * b; | |
require(c / a == b, "SafeMath: multiplication overflow"); | |
return c; | |
} | |
/** | |
* @dev Returns the integer division of two unsigned integers, reverting on | |
* division by zero. The result is rounded towards zero. | |
* | |
* Counterpart to Solidity's `/` operator. Note: this function uses a | |
* `revert` opcode (which leaves remaining gas untouched) while Solidity | |
* uses an invalid opcode to revert (consuming all remaining gas). | |
* | |
* Requirements: | |
* | |
* - The divisor cannot be zero. | |
*/ | |
function div(uint256 a, uint256 b) internal pure returns (uint256) { | |
require(b > 0, "SafeMath: division by zero"); | |
return a / b; | |
} | |
/** | |
* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo), | |
* reverting when dividing by zero. | |
* | |
* Counterpart to Solidity's `%` operator. This function uses a `revert` | |
* opcode (which leaves remaining gas untouched) while Solidity uses an | |
* invalid opcode to revert (consuming all remaining gas). | |
* | |
* Requirements: | |
* | |
* - The divisor cannot be zero. | |
*/ | |
function mod(uint256 a, uint256 b) internal pure returns (uint256) { | |
require(b > 0, "SafeMath: modulo by zero"); | |
return a % b; | |
} | |
/** | |
* @dev Returns the subtraction of two unsigned integers, reverting with custom message on | |
* overflow (when the result is negative). | |
* | |
* CAUTION: This function is deprecated because it requires allocating memory for the error | |
* message unnecessarily. For custom revert reasons use {trySub}. | |
* | |
* Counterpart to Solidity's `-` operator. | |
* | |
* Requirements: | |
* | |
* - Subtraction cannot overflow. | |
*/ | |
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { | |
require(b <= a, errorMessage); | |
return a - b; | |
} | |
/** | |
* @dev Returns the integer division of two unsigned integers, reverting with custom message on | |
* division by zero. The result is rounded towards zero. | |
* | |
* CAUTION: This function is deprecated because it requires allocating memory for the error | |
* message unnecessarily. For custom revert reasons use {tryDiv}. | |
* | |
* Counterpart to Solidity's `/` operator. Note: this function uses a | |
* `revert` opcode (which leaves remaining gas untouched) while Solidity | |
* uses an invalid opcode to revert (consuming all remaining gas). | |
* | |
* Requirements: | |
* | |
* - The divisor cannot be zero. | |
*/ | |
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { | |
require(b > 0, errorMessage); | |
return a / b; | |
} | |
/** | |
* @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo), | |
* reverting with custom message when dividing by zero. | |
* | |
* CAUTION: This function is deprecated because it requires allocating memory for the error | |
* message unnecessarily. For custom revert reasons use {tryMod}. | |
* | |
* Counterpart to Solidity's `%` operator. This function uses a `revert` | |
* opcode (which leaves remaining gas untouched) while Solidity uses an | |
* invalid opcode to revert (consuming all remaining gas). | |
* | |
* Requirements: | |
* | |
* - The divisor cannot be zero. | |
*/ | |
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) { | |
require(b > 0, errorMessage); | |
return a % b; | |
} | |
} |
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