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fix: added extra security measure for ERC20/ERC721 contracts #31

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fix: added extra security measure for ERC20/ERC721 contracts #31

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46 changes: 30 additions & 16 deletions contracts/ERC20.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -5,68 +5,82 @@ import "./IERC20.sol";

contract ERC20 is IERC20 {
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(
address indexed owner, address indexed spender, uint256 value
);
event Approval(address indexed owner, address indexed spender, uint256 value);

uint256 public totalSupply;
mapping(address => uint256) public balanceOf;
mapping(address => mapping(address => uint256)) public allowance;
string public name;
string public symbol;
uint8 public decimals;

address private _owner;

modifier onlyOwner() {
require(msg.sender == _owner, "caller is not the owner");
_;
}

constructor(string memory _name, string memory _symbol, uint8 _decimals) {
name = _name;
symbol = _symbol;
decimals = _decimals;
_owner = msg.sender;
}

function transfer(address recipient, uint256 amount)
external
returns (bool)
{
function transfer(address recipient, uint256 amount) external returns (bool) {
require(recipient != address(0), "transfer to zero address");
require(balanceOf[msg.sender] >= amount, "transfer amount exceeds balance");
require(balanceOf[msg.sender] > 0, "transfer amount must be greater than 0");

balanceOf[msg.sender] -= amount;
balanceOf[recipient] += amount;
emit Transfer(msg.sender, recipient, amount);

return true;
}

function approve(address spender, uint256 amount) external returns (bool) {
require(spender != address(0), "approve to 0 address");

allowance[msg.sender][spender] = amount;
emit Approval(msg.sender, spender, amount);
return true;
}

function transferFrom(address sender, address recipient, uint256 amount)
external
returns (bool)
{
require(msg.sender != recipient, "cannot transfer to self");
allowance[sender][msg.sender] -= amount;
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool) {
require(sender != address(0), "transfer to correct address");
require(recipient != address(0), "transfer to correct address");
require(balanceOf[sender] >= amount, "transfer amount exceeds balance");

balanceOf[sender] -= amount;
balanceOf[recipient] += amount;
allowance[sender][msg.sender] -= amount;
emit Transfer(sender, recipient, amount);
return true;
}

function _mint(address to, uint256 amount) internal {
require(to != address(0), "mint to zero address");

balanceOf[to] += amount;
totalSupply += amount;
emit Transfer(address(0), to, amount);
}

function _burn(address from, uint256 amount) internal {
require(from != address(0), "burn from the zero address");
require(balanceOf[from] >= amount, "ERC20: burn amount exceeds balance");

balanceOf[from] -= amount;
totalSupply -= amount;
emit Transfer(from, address(0), amount);
}

function mint(address to, uint256 amount) external {
function mint(address to, uint256 amount) external onlyOwner {
_mint(to, amount);
}

function burn(address from, uint256 amount) external {
function burn(address from, uint256 amount) external onlyOwner {
_burn(from, amount);
}
}
115 changes: 78 additions & 37 deletions contracts/ERC721.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -2,30 +2,42 @@
pragma solidity ^0.8.24;

interface IERC165 {
function supportsInterface(bytes4 interfaceID)
external
view
returns (bool);
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

interface IERC721 is IERC165 {
function balanceOf(address owner) external view returns (uint256 balance);

function ownerOf(uint256 tokenId) external view returns (address owner);
function safeTransferFrom(address from, address to, uint256 tokenId)
external;

function safeTransferFrom(
address from,
address to,
uint256 tokenId
) external;

function safeTransferFrom(
address from,
address to,
uint256 tokenId,
bytes calldata data
) external;
function transferFrom(address from, address to, uint256 tokenId) external;

function transferFrom(
address from,
address to,
uint256 tokenId
) external;

function approve(address to, uint256 tokenId) external;

function getApproved(uint256 tokenId)
external
view
returns (address operator);

function setApprovalForAll(address operator, bool _approved) external;

function isApprovedForAll(address owner, address operator)
external
view
Expand All @@ -43,13 +55,19 @@ interface IERC721Receiver {

contract ERC721 is IERC721 {
event Transfer(
address indexed from, address indexed to, uint256 indexed id
address indexed from,
address indexed to,
uint256 indexed id
);
event Approval(
address indexed owner, address indexed spender, uint256 indexed id
address indexed owner,
address indexed spender,
uint256 indexed id
);
event ApprovalForAll(
address indexed owner, address indexed operator, bool approved
address indexed owner,
address indexed operator,
bool approved
);

// Mapping from token ID to owner address
Expand All @@ -69,8 +87,9 @@ contract ERC721 is IERC721 {
pure
returns (bool)
{
return interfaceId == type(IERC721).interfaceId
|| interfaceId == type(IERC165).interfaceId;
return
interfaceId == type(IERC721).interfaceId ||
interfaceId == type(IERC165).interfaceId;
}

function ownerOf(uint256 id) external view returns (address owner) {
Expand All @@ -96,7 +115,6 @@ contract ERC721 is IERC721 {
);

_approvals[id] = spender;

emit Approval(owner, spender, id);
}

Expand All @@ -105,39 +123,49 @@ contract ERC721 is IERC721 {
return _approvals[id];
}

function _isApprovedOrOwner(address owner, address spender, uint256 id)
internal
view
returns (bool)
{
return (
spender == owner || isApprovedForAll[owner][spender]
|| spender == _approvals[id]
);
function _isApprovedOrOwner(
address owner,
address spender,
uint256 id
) internal view returns (bool) {
return (spender == owner ||
isApprovedForAll[owner][spender] ||
spender == _approvals[id]);
}

function transferFrom(address from, address to, uint256 id) public {
function transferFrom(
address from,
address to,
uint256 id
) public {
require(from == _ownerOf[id], "from != owner");
require(to != address(0), "transfer to zero address");

require(_isApprovedOrOwner(from, msg.sender, id), "not authorized");

_balanceOf[from]--;
_balanceOf[to]++;
_ownerOf[id] = to;

delete _approvals[id];

emit Transfer(from, to, id);
}

function safeTransferFrom(address from, address to, uint256 id) external {
function safeTransferFrom(
address from,
address to,
uint256 id
) external {
transferFrom(from, to, id);

require(
to.code.length == 0
|| IERC721Receiver(to).onERC721Received(msg.sender, from, id, "")
== IERC721Receiver.onERC721Received.selector,
to.code.length == 0 ||
IERC721Receiver(to).onERC721Received(
msg.sender,
from,
id,
""
) ==
IERC721Receiver.onERC721Received.selector,
"unsafe recipient"
);
}
Expand All @@ -151,9 +179,14 @@ contract ERC721 is IERC721 {
transferFrom(from, to, id);

require(
to.code.length == 0
|| IERC721Receiver(to).onERC721Received(msg.sender, from, id, data)
== IERC721Receiver.onERC721Received.selector,
to.code.length == 0 ||
IERC721Receiver(to).onERC721Received(
msg.sender,
from,
id,
data
) ==
IERC721Receiver.onERC721Received.selector,
"unsafe recipient"
);
}
Expand All @@ -164,25 +197,33 @@ contract ERC721 is IERC721 {

_balanceOf[to]++;
_ownerOf[id] = to;

emit Transfer(address(0), to, id);
}

function _burn(uint256 id) internal {
address owner = _ownerOf[id];
require(owner != address(0), "not minted");

_balanceOf[owner] -= 1;

_balanceOf[owner]--;
delete _ownerOf[id];
delete _approvals[id];

emit Transfer(owner, address(0), id);
}
}

contract MyNFT is ERC721 {
function mint(address to, uint256 id) external {
address private _admin;

constructor() {
_admin = msg.sender;
}

modifier onlyAdmin() {
require(msg.sender == _admin, "not authorized");
_;
}

function mint(address to, uint256 id) external onlyAdmin {
_mint(to, id);
}

Expand Down