# Wallet Protocol Draft

## Implementation contract can be destroyed by anyone

**Severity**: High

**Context**: [`Implementation.sol#L17`](https://github.com/spearbit-audits/writing-exercise/blob/develop/contracts/Implementation.sol#L17)

- delegatecallContract can be called by anyone and call delegate call to any arbitrary address.

- If delegatecallContract is called directly rather than from proxy, and it delegates to a contract and that delegatee contract executes `SELFDESTRUCT` then the logic of proxy is erased and becomes `0x` leaving it unusable for all of the proxies.

**POC**

// SPDX-License-Identifier: MIT
pragma solidity 0.8.10;

contract Malicious {

    function kill() external payable {
        selfdestruct(payable(address(0)));
    }
}

If `Implementation.delegatecallContract` is called directly (without using proxy) and delegates call to`Malicious`, then `Implementation` is destroyed

**Recommendations**

diff --git a/contracts/Implementation.sol b/contracts/Implementation.sol
index a7ab071..3bd3329 100644
--- a/contracts/Implementation.sol
+++ b/contracts/Implementation.sol
@@ -8,6 +8,12 @@ pragma solidity 0.8.10;
 /// Only deployed once and the implementation is reused by all proxy contracts.
 contract Implementation {
 
+    address immutable self;
+
+    constructor() {
+        self = address(this);
+    }
+
     function callContract(address a, bytes calldata _calldata) payable external returns (bytes memory) {
         (bool success , bytes memory ret) =  a.call{value: msg.value}(_calldata);
         require(success);
@@ -15,6 +21,7 @@ contract Implementation {
     }
 
     function delegatecallContract(address a, bytes calldata _calldata) payable external returns (bytes memory) {
+        require(address(this) != self);
         (bool success, bytes memory ret) =  a.delegatecall(_calldata);
         require(success);
         return ret;

- when the `Implementation` contract is deployed, register its real address in variable and on each delegatecall, compare execution context address with a real address, it should not be same to prevent it being called directly.