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90 lines
2.5 KiB
90 lines
2.5 KiB
pragma solidity ^0.4.18;
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import "../ownership/Ownable.sol";
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import "../ownership/rbac/RBAC.sol";
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import "../ECRecovery.sol";
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/**
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* @title SignatureBouncer
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* @author PhABC and Shrugs
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* @dev Bouncer allows users to submit a signature as a permission to do an action.
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* @dev If the signature is from one of the authorized bouncer addresses, the signature
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* @dev is valid. The owner of the contract adds/removes bouncers.
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* @dev Bouncer addresses can be individual servers signing grants or different
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* @dev users within a decentralized club that have permission to invite other members.
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* @dev
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* @dev This technique is useful for whitelists and airdrops; instead of putting all
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* @dev valid addresses on-chain, simply sign a grant of the form
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* @dev keccak256(`:contractAddress` + `:granteeAddress`) using a valid bouncer address.
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* @dev Then restrict access to your crowdsale/whitelist/airdrop using the
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* @dev `onlyValidSignature` modifier (or implement your own using isValidSignature).
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* @dev
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* @dev See the tests Bouncer.test.js for specific usage examples.
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*/
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contract SignatureBouncer is Ownable, RBAC {
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using ECRecovery for bytes32;
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string public constant ROLE_BOUNCER = "bouncer";
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/**
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* @dev requires that a valid signature of a bouncer was provided
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*/
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modifier onlyValidSignature(bytes _sig)
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{
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require(isValidSignature(msg.sender, _sig));
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_;
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}
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/**
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* @dev allows the owner to add additional bouncer addresses
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*/
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function addBouncer(address _bouncer)
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onlyOwner
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public
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{
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require(_bouncer != address(0));
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addRole(_bouncer, ROLE_BOUNCER);
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}
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/**
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* @dev allows the owner to remove bouncer addresses
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*/
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function removeBouncer(address _bouncer)
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onlyOwner
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public
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{
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require(_bouncer != address(0));
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removeRole(_bouncer, ROLE_BOUNCER);
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}
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/**
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* @dev is the signature of `this + sender` from a bouncer?
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* @return bool
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*/
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function isValidSignature(address _address, bytes _sig)
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internal
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view
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returns (bool)
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{
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return isValidDataHash(
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keccak256(address(this), _address),
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_sig
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);
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}
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/**
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* @dev internal function to convert a hash to an eth signed message
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* @dev and then recover the signature and check it against the bouncer role
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* @return bool
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*/
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function isValidDataHash(bytes32 hash, bytes _sig)
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internal
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view
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returns (bool)
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{
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address signer = hash
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.toEthSignedMessageHash()
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.recover(_sig);
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return hasRole(signer, ROLE_BOUNCER);
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}
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}
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