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// proxy.sol - execute actions atomically through the proxy's identity
// Copyright (C) 2017 DappHub, LLC
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <>.
pragma solidity >=0.6.7;
import "ds-auth/auth.sol";
import "ds-note/note.sol";
// DSProxy
// Allows code execution using a persistant identity This can be very
// useful to execute a sequence of atomic actions. Since the owner of
// the proxy can be changed, this allows for dynamic ownership models
// i.e. a multisig
contract DSProxy is DSAuth, DSNote {
DSProxyCache public cache; // global cache for contracts
constructor(address _cacheAddr) public {
receive() external payable {
// use the proxy to execute calldata _data on contract _code
function execute(bytes memory _code, bytes memory _data)
returns (address target, bytes memory response)
target =;
if (target == address(0)) {
// deploy contract & store its address in cache
target = cache.write(_code);
response = execute(target, _data);
function execute(address _target, bytes memory _data)
returns (bytes memory response)
require(_target != address(0), "ds-proxy-target-address-required");
// call contract in current context
assembly {
let succeeded := delegatecall(sub(gas(), 5000), _target, add(_data, 0x20), mload(_data), 0, 0)
let size := returndatasize()
response := mload(0x40)
mstore(0x40, add(response, and(add(add(size, 0x20), 0x1f), not(0x1f))))
mstore(response, size)
returndatacopy(add(response, 0x20), 0, size)
switch iszero(succeeded)
case 1 {
// throw if delegatecall failed
revert(add(response, 0x20), size)
//set new cache
function setCache(address _cacheAddr)
returns (bool)
require(_cacheAddr != address(0), "ds-proxy-cache-address-required");
cache = DSProxyCache(_cacheAddr); // overwrite cache
return true;
// DSProxyFactory
// This factory deploys new proxy instances through build()
// Deployed proxy addresses are logged
contract DSProxyFactory {
event Created(address indexed sender, address indexed owner, address proxy, address cache);
mapping(address=>bool) public isProxy;
DSProxyCache public cache;
constructor() public {
cache = new DSProxyCache();
// deploys a new proxy instance
// sets owner of proxy to caller
function build() public returns (address payable proxy) {
proxy = build(msg.sender);
// deploys a new proxy instance
// sets custom owner of proxy
function build(address owner) public returns (address payable proxy) {
proxy = address(new DSProxy(address(cache)));
emit Created(msg.sender, owner, address(proxy), address(cache));
isProxy[proxy] = true;
// DSProxyCache
// This global cache stores addresses of contracts previously deployed
// by a proxy. This saves gas from repeat deployment of the same
// contracts and eliminates blockchain bloat.
// By default, all proxies deployed from the same factory store
// contracts in the same cache. The cache a proxy instance uses can be
// changed. The cache uses the sha3 hash of a contract's bytecode to
// lookup the address
contract DSProxyCache {
mapping(bytes32 => address) cache;
function read(bytes memory _code) public view returns (address) {
bytes32 hash = keccak256(_code);
return cache[hash];
function write(bytes memory _code) public returns (address target) {
assembly {
target := create(0, add(_code, 0x20), mload(_code))
switch iszero(extcodesize(target))
case 1 {
// throw if contract failed to deploy
revert(0, 0)
bytes32 hash = keccak256(_code);
cache[hash] = target;