Registrar contract: specify who can create new names

[chriseth]

The owner can arbitrarily modify the addresses that can freely register subdomains with this registrar.

Initially it was proposed that the registrar contract creates the proxy itself, but I think just specifying an address is more flexible.

[yann300]

using the FIFSRegistrar

pragma solidity ^0.4.0;

import 'interface.sol';

/**
 * A registrar that allocates subdomains to the first person to claim them.
 */
contract FIFSRegistrar {
    AbstractENS ens;
    bytes32 rootNode;
    mapping (address => uint8) allowedAddresses;

    modifier only_allowed() {
        if (allowedAddresses[msg.sender] != 1)
            throw;
        _;
    }

    modifier only_owner(bytes32 subnode) {
        var node = sha3(rootNode, subnode);
        var currentOwner = ens.owner(node);
        if(currentOwner != 0 && currentOwner != msg.sender)
            throw;
        _;
    }

    /**
     * Constructor.
     * @param ensAddr The address of the ENS registry.
     * @param node The node that this registrar administers.
     */
    function FIFSRegistrar(AbstractENS ensAddr, bytes32 node) {
        ens = ensAddr;
        rootNode = node;
    }

    /**
     * Register a name, or change the owner of an existing registration.
     * @param subnode The hash of the label to register.
     * @param owner The address of the new owner.
     */    
    function register(bytes32 subnode, address owner) only_allowed() {
        ens.setSubnodeOwner(rootNode, subnode, owner);
    }

    /**
     * @param allowed Address who is allowed to register here.
     */    
    function setAllowedAddress(address allowed) only_owner(rootNode) {
        allowedAddresses[allowed] = 1;
    }

    /**
     * @param allowed Remove address who is allowed to register here.
     */    
    function removeAllowedAddress(address allowed) only_owner(rootNode) {
        delete allowedAddresses[allowed];
    }
}