An onlyProxy modifier for minimal proxies

Smart Contracts
1

Hi everyone,

The Openzeppelin's contract UUPSUpgradeable has the following modifier onlyProxy in order to guarantee that the functions of an implementation contract can't be called directly but throughth a proxy:

 /**
     * @dev Check that the execution is being performed through a delegatecall call and that the execution context is
     * a proxy contract with an implementation (as defined in ERC1967) pointing to self. This should only be the case
     * for UUPS and transparent proxies that are using the current contract as their implementation. Execution of a
     * function through ERC1167 minimal proxies (clones) would not normally pass this test, but is not guaranteed to
     * fail.
     */
    modifier onlyProxy() {
        require(address(this) != __self, "Function must be called through delegatecall");
        require(_getImplementation() == __self, "Function must be called through active proxy");
        _;
    }

Since it's declared in the UUPS, I copy the same idea to my Upgradeable contract that follows the Transparent pattern so as I could have the same guarantee. Considering that both Transparent and UUPS follow the Standard Proxy Storage Slots (EIP-1967), it works perfectly.

However, when I tryed to do the same for a Minimal Proxy it does not. My assumption is that the minimal proxies created by @openzeppelin/contracts/proxy/Clones.sol doesn't store the implementation address at the same slot. Is that right?

Is this slot known ahead of time so as we can adapt and create a similar modifier onlyMininalProxy or it's random or something?

Regards,