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/*
-----------------------------------------------------------------
FILE INFORMATION
-----------------------------------------------------------------
file: Proxy.sol
version: 1.3
author: Anton Jurisevic
date: 2018-05-29
-----------------------------------------------------------------
MODULE DESCRIPTION
-----------------------------------------------------------------
A proxy contract that, if it does not recognise the function
being called on it, passes all value and call data to an
underlying target contract.
This proxy has the capacity to toggle between DELEGATECALL
and CALL style proxy functionality.
The former executes in the proxy's context, and so will preserve
msg.sender and store data at the proxy address. The latter will not.
Therefore, any contract the proxy wraps in the CALL style must
implement the Proxyable interface, in order that it can pass msg.sender
into the underlying contract as the state parameter, messageSender.
-----------------------------------------------------------------
*/
pragma solidity 0.4.25;
import "./Owned.sol";
import "./Proxyable.sol";
contract Proxy is Owned {
Proxyable public target;
bool public useDELEGATECALL;
constructor(address _owner)
Owned(_owner)
public
{}
function setTarget(Proxyable _target)
external
onlyOwner
{
target = _target;
emit TargetUpdated(_target);
}
function setUseDELEGATECALL(bool value)
external
onlyOwner
{
useDELEGATECALL = value;
}
function _emit(bytes callData, uint numTopics, bytes32 topic1, bytes32 topic2, bytes32 topic3, bytes32 topic4)
external
onlyTarget
{
uint size = callData.length;
bytes memory _callData = callData;
assembly {
/* The first 32 bytes of callData contain its length (as specified by the abi).
* Length is assumed to be a uint256 and therefore maximum of 32 bytes
* in length. It is also leftpadded to be a multiple of 32 bytes.
* This means moving call_data across 32 bytes guarantees we correctly access
* the data itself. */
switch numTopics
case 0 {
log0(add(_callData, 32), size)
}
case 1 {
log1(add(_callData, 32), size, topic1)
}
case 2 {
log2(add(_callData, 32), size, topic1, topic2)
}
case 3 {
log3(add(_callData, 32), size, topic1, topic2, topic3)
}
case 4 {
log4(add(_callData, 32), size, topic1, topic2, topic3, topic4)
}
}
}
function()
external
payable
{
if (useDELEGATECALL) {
assembly {
/* Copy call data into free memory region. */
let free_ptr := mload(0x40)
calldatacopy(free_ptr, 0, calldatasize)
/* Forward all gas and call data to the target contract. */
let result := delegatecall(gas, sload(target_slot), free_ptr, calldatasize, 0, 0)
returndatacopy(free_ptr, 0, returndatasize)
/* Revert if the call failed, otherwise return the result. */
if iszero(result) { revert(free_ptr, returndatasize) }
return(free_ptr, returndatasize)
}
} else {
/* Here we are as above, but must send the messageSender explicitly
* since we are using CALL rather than DELEGATECALL. */
target.setMessageSender(msg.sender);
assembly {
let free_ptr := mload(0x40)
calldatacopy(free_ptr, 0, calldatasize)
/* We must explicitly forward ether to the underlying contract as well. */
let result := call(gas, sload(target_slot), callvalue, free_ptr, calldatasize, 0, 0)
returndatacopy(free_ptr, 0, returndatasize)
if iszero(result) { revert(free_ptr, returndatasize) }
return(free_ptr, returndatasize)
}
}
}
modifier onlyTarget {
require(Proxyable(msg.sender) == target, "Must be proxy target");
_;
}
event TargetUpdated(Proxyable newTarget);
}
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