diff options
Diffstat (limited to 'packages/contracts/src/2.0.0/protocol/AssetProxy')
8 files changed, 684 insertions, 0 deletions
diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol new file mode 100644 index 000000000..aed62f54f --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC20Proxy.sol @@ -0,0 +1,132 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; +pragma experimental ABIEncoderV2; + +import "../../utils/LibBytes/LibBytes.sol"; +import "./MixinAuthorizable.sol"; + +contract ERC20Proxy is + MixinAuthorizable +{ + // Id of this proxy. + bytes4 constant PROXY_ID = bytes4(keccak256("ERC20Token(address)")); + + function () + external + { + assembly { + // The first 4 bytes of calldata holds the function selector + let selector := and(calldataload(0), 0xffffffff00000000000000000000000000000000000000000000000000000000) + + // `transferFrom` will be called with the following parameters: + // assetData Encoded byte array. + // from Address to transfer asset from. + // to Address to transfer asset to. + // amount Amount of asset to transfer. + // bytes4(keccak256("transferFrom(bytes,address,address,uint256)")) = 0xa85e59e4 + if eq(selector, 0xa85e59e400000000000000000000000000000000000000000000000000000000) { + + // To lookup a value in a mapping, we load from the storage location keccak256(k, p), + // where k is the key left padded to 32 bytes and p is the storage slot + let start := mload(64) + mstore(start, and(caller, 0xffffffffffffffffffffffffffffffffffffffff)) + mstore(add(start, 32), authorized_slot) + + // Revert if authorized[msg.sender] == false + if iszero(sload(keccak256(start, 64))) { + // Revert with `Error("SENDER_NOT_AUTHORIZED")` + mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000) + mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000) + mstore(64, 0x0000001553454e4445525f4e4f545f415554484f52495a454400000000000000) + mstore(96, 0) + revert(0, 100) + } + + /////// Token contract address /////// + // The token address is found as follows: + // * It is stored at offset 4 in `assetData` contents. + // * This is stored at offset 32 from `assetData`. + // * The offset to `assetData` from Params is stored at offset + // 4 in calldata. + // * The offset of Params in calldata is 4. + // So we read location 4 and add 32 + 4 + 4 to it. + let token := calldataload(add(calldataload(4), 40)) + + /////// Setup Header Area /////// + // This area holds the 4-byte `transferFrom` selector. + // Any trailing data in transferFromSelector will be + // overwritten in the next `mstore` call. + mstore(0, 0x23b872dd00000000000000000000000000000000000000000000000000000000) + + /////// Setup Params Area /////// + // We copy the fields `from`, `to` and `amount` in bulk + // from our own calldata to the new calldata. + calldatacopy(4, 36, 96) + + /////// Call `token.transferFrom` using the calldata /////// + let success := call( + gas, // forward all gas + token, // call address of token contract + 0, // don't send any ETH + 0, // pointer to start of input + 100, // length of input + 0, // write output over input + 32 // output size should be 32 bytes + ) + + /////// Check return data. /////// + // If there is no return data, we assume the token incorrectly + // does not return a bool. In this case we expect it to revert + // on failure, which was handled above. + // If the token does return data, we require that it is a single + // nonzero 32 bytes value. + // So the transfer succeeded if the call succeeded and either + // returned nothing, or returned a non-zero 32 byte value. + success := and(success, or( + iszero(returndatasize), + and( + eq(returndatasize, 32), + gt(mload(0), 0) + ) + )) + if success { + return(0, 0) + } + + // Revert with `Error("TRANSFER_FAILED")` + mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000) + mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000) + mstore(64, 0x0000000f5452414e534645525f4641494c454400000000000000000000000000) + mstore(96, 0) + revert(0, 100) + } + } + } + + /// @dev Gets the proxy id associated with the proxy address. + /// @return Proxy id. + function getProxyId() + external + pure + returns (bytes4) + { + return PROXY_ID; + } +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol new file mode 100644 index 000000000..b73dc36cc --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol @@ -0,0 +1,218 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; +pragma experimental ABIEncoderV2; + +import "../../utils/LibBytes/LibBytes.sol"; +import "./MixinAuthorizable.sol"; + +contract ERC721Proxy is + MixinAuthorizable +{ + // Id of this proxy. + bytes4 constant PROXY_ID = bytes4(keccak256("ERC721Token(address,uint256,bytes)")); + + function () + external + { + assembly { + // The first 4 bytes of calldata holds the function selector + let selector := and(calldataload(0), 0xffffffff00000000000000000000000000000000000000000000000000000000) + + // `transferFrom` will be called with the following parameters: + // assetData Encoded byte array. + // from Address to transfer asset from. + // to Address to transfer asset to. + // amount Amount of asset to transfer. + // bytes4(keccak256("transferFrom(bytes,address,address,uint256)")) = 0xa85e59e4 + if eq(selector, 0xa85e59e400000000000000000000000000000000000000000000000000000000) { + + // To lookup a value in a mapping, we load from the storage location keccak256(k, p), + // where k is the key left padded to 32 bytes and p is the storage slot + let start := mload(64) + mstore(start, and(caller, 0xffffffffffffffffffffffffffffffffffffffff)) + mstore(add(start, 32), authorized_slot) + + // Revert if authorized[msg.sender] == false + if iszero(sload(keccak256(start, 64))) { + // Revert with `Error("SENDER_NOT_AUTHORIZED")` + mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000) + mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000) + mstore(64, 0x0000001553454e4445525f4e4f545f415554484f52495a454400000000000000) + mstore(96, 0) + revert(0, 100) + } + + // `transferFrom`. + // The function is marked `external`, so no abi decodeding is done for + // us. Instead, we expect the `calldata` memory to contain the + // following: + // + // | Area | Offset | Length | Contents | + // |----------|--------|---------|-------------------------------------| + // | Header | 0 | 4 | function selector | + // | Params | | 4 * 32 | function parameters: | + // | | 4 | | 1. offset to assetData (*) | + // | | 36 | | 2. from | + // | | 68 | | 3. to | + // | | 100 | | 4. amount | + // | Data | | | assetData: | + // | | 132 | 32 | assetData Length | + // | | 164 | ** | assetData Contents | + // + // (*): offset is computed from start of function parameters, so offset + // by an additional 4 bytes in the calldata. + // + // WARNING: The ABIv2 specification allows additional padding between + // the Params and Data section. This will result in a larger + // offset to assetData. + + // Asset data itself is encoded as follows: + // + // | Area | Offset | Length | Contents | + // |----------|--------|---------|-------------------------------------| + // | Header | 0 | 4 | function selector | + // | Params | | 3 * 32 | function parameters: | + // | | 4 | 12 + 20 | 1. token address | + // | | 36 | | 2. tokenId | + // | | 68 | | 3. offset to receiverData (*) | + // | Data | | | receiverData: | + // | | 100 | 32 | receiverData Length | + // | | 132 | ** | receiverData Contents | + + // We construct calldata for the `token.safeTransferFrom` ABI. + // The layout of this calldata is in the table below. + // + // | Area | Offset | Length | Contents | + // |----------|--------|---------|-------------------------------------| + // | Header | 0 | 4 | function selector | + // | Params | | 4 * 32 | function parameters: | + // | | 4 | | 1. from | + // | | 36 | | 2. to | + // | | 68 | | 3. tokenId | + // | | 100 | | 4. offset to receiverData (*) | + // | Data | | | receiverData: | + // | | 132 | 32 | receiverData Length | + // | | 164 | ** | receiverData Contents | + + // There exists only 1 of each token. + // require(amount == 1, "INVALID_AMOUNT") + if sub(calldataload(100), 1) { + // Revert with `Error("INVALID_AMOUNT")` + mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000) + mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000) + mstore(64, 0x0000000e494e56414c49445f414d4f554e540000000000000000000000000000) + mstore(96, 0) + revert(0, 100) + } + + // Require assetData to be at least 132 bytes + let offset := calldataload(4) + if lt(calldataload(add(offset, 4)), 132) { + // Revert with `Error("LENGTH_GREATER_THAN_131_REQUIRED")` + mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000) + mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000) + mstore(64, 0x000000204c454e4754485f475245415445525f5448414e5f3133315f52455155) + mstore(96, 0x4952454400000000000000000000000000000000000000000000000000000000) + revert(0, 100) + } + + /////// Setup State /////// + // `cdStart` is the start of the calldata for + // `token.safeTransferFrom` (equal to free memory ptr). + let cdStart := mload(64) + // `dataAreaLength` is the total number of words + // needed to store `receiverData` + // As-per the ABI spec, this value is padded up to + // the nearest multiple of 32, + // and includes 32-bytes for length. + // It's calculated as folows: + // - Unpadded length in bytes = `mload(receiverData) + 32` + // - Add 31 to convert rounding down to rounding up. + // Combined with the previous and this is `63`. + // - Round down to nearest multiple of 32 by clearing + // bits 0x1F. This is done with `and` and a mask. + + /////// Setup Header Area /////// + // This area holds the 4-byte `transferFromSelector`. + // Any trailing data in transferFromSelector will be + // overwritten in the next `mstore` call. + mstore(cdStart, 0xb88d4fde00000000000000000000000000000000000000000000000000000000) + + /////// Setup Params Area /////// + // Each parameter is padded to 32-bytes. + // The entire Params Area is 128 bytes. + // Notes: + // 1. A 20-byte mask is applied to addresses + // to zero-out the unused bytes. + // 2. The offset to `receiverData` is the length + // of the Params Area (128 bytes). + + let length := calldataload(add(offset, 136)) + let token := calldataload(add(offset, 40)) + + // Round length up to multiple of 32 + length := and(add(length, 31), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE0) + + // Copy `from` and `to` + calldatacopy(add(cdStart, 4), 36, 64) + + // TokenId + mstore(add(cdStart, 68), calldataload(add(offset, 72))) + + // Offset to receiverData + mstore(add(cdStart, 100), 128) + + // receiverData (including length) + calldatacopy(add(cdStart, 132), add(offset, 136), add(length, 32)) + + /////// Call `token.safeTransferFrom` using the calldata /////// + let success := call( + gas, // forward all gas + token, // call address of token contract + 0, // don't send any ETH + cdStart, // pointer to start of input + add(length, 164), // length of input + 0, // write output to null + 0 // output size is 0 bytes + ) + if success { + return(0, 0) + } + + // Revert with `Error("TRANSFER_FAILED")` + mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000) + mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000) + mstore(64, 0x0000000f5452414e534645525f4641494c454400000000000000000000000000) + mstore(96, 0) + revert(0, 100) + } + } + } + + /// @dev Gets the proxy id associated with the proxy address. + /// @return Proxy id. + function getProxyId() + external + pure + returns (bytes4) + { + return PROXY_ID; + } +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol new file mode 100644 index 000000000..3b9584a44 --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/MixinAuthorizable.sol @@ -0,0 +1,118 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; +pragma experimental ABIEncoderV2; + +import "../../utils/Ownable/Ownable.sol"; +import "./mixins/MAuthorizable.sol"; + +contract MixinAuthorizable is + Ownable, + MAuthorizable +{ + + /// @dev Only authorized addresses can invoke functions with this modifier. + modifier onlyAuthorized { + require( + authorized[msg.sender], + "SENDER_NOT_AUTHORIZED" + ); + _; + } + + mapping (address => bool) public authorized; + address[] public authorities; + + /// @dev Authorizes an address. + /// @param target Address to authorize. + function addAuthorizedAddress(address target) + external + onlyOwner + { + require( + !authorized[target], + "TARGET_ALREADY_AUTHORIZED" + ); + + authorized[target] = true; + authorities.push(target); + emit AuthorizedAddressAdded(target, msg.sender); + } + + /// @dev Removes authorizion of an address. + /// @param target Address to remove authorization from. + function removeAuthorizedAddress(address target) + external + onlyOwner + { + require( + authorized[target], + "TARGET_NOT_AUTHORIZED" + ); + + delete authorized[target]; + for (uint256 i = 0; i < authorities.length; i++) { + if (authorities[i] == target) { + authorities[i] = authorities[authorities.length - 1]; + authorities.length -= 1; + break; + } + } + emit AuthorizedAddressRemoved(target, msg.sender); + } + + /// @dev Removes authorizion of an address. + /// @param target Address to remove authorization from. + /// @param index Index of target in authorities array. + function removeAuthorizedAddressAtIndex( + address target, + uint256 index + ) + external + onlyOwner + { + require( + authorized[target], + "TARGET_NOT_AUTHORIZED" + ); + require( + index < authorities.length, + "INDEX_OUT_OF_BOUNDS" + ); + require( + authorities[index] == target, + "AUTHORIZED_ADDRESS_MISMATCH" + ); + + delete authorized[target]; + authorities[index] = authorities[authorities.length - 1]; + authorities.length -= 1; + emit AuthorizedAddressRemoved(target, msg.sender); + } + + /// @dev Gets all authorized addresses. + /// @return Array of authorized addresses. + function getAuthorizedAddresses() + external + view + returns (address[] memory) + { + return authorities; + } +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetData.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetData.sol new file mode 100644 index 000000000..7ebd6acf0 --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetData.sol @@ -0,0 +1,38 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.23; + +// @dev Interface of the asset proxy's assetData. +// The asset proxies take an ABI encoded `bytes assetData` as argument. +// This argument is ABI encoded as one of the methods of this interface. +interface IAssetData { + + function ERC20Token(address tokenContract) + external + pure; + + function ERC721Token( + address tokenContract, + uint256 tokenId, + bytes receiverData + ) + external + pure; + +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol new file mode 100644 index 000000000..eacd5a412 --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAssetProxy.sol @@ -0,0 +1,47 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; +pragma experimental ABIEncoderV2; + +import "./IAuthorizable.sol"; + +contract IAssetProxy is + IAuthorizable +{ + + /// @dev Transfers assets. Either succeeds or throws. + /// @param assetData Byte array encoded for the respective asset proxy. + /// @param from Address to transfer asset from. + /// @param to Address to transfer asset to. + /// @param amount Amount of asset to transfer. + function transferFrom( + bytes assetData, + address from, + address to, + uint256 amount + ) + external; + + /// @dev Gets the proxy id associated with the proxy address. + /// @return Proxy id. + function getProxyId() + external + pure + returns (bytes4); +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol new file mode 100644 index 000000000..cedd1744c --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/interfaces/IAuthorizable.sol @@ -0,0 +1,53 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; +pragma experimental ABIEncoderV2; + +import "../../../utils/Ownable/IOwnable.sol"; + +contract IAuthorizable is + IOwnable +{ + + /// @dev Gets all authorized addresses. + /// @return Array of authorized addresses. + function getAuthorizedAddresses() + external + view + returns (address[]); + + /// @dev Authorizes an address. + /// @param target Address to authorize. + function addAuthorizedAddress(address target) + external; + + /// @dev Removes authorizion of an address. + /// @param target Address to remove authorization from. + function removeAuthorizedAddress(address target) + external; + + /// @dev Removes authorizion of an address. + /// @param target Address to remove authorization from. + /// @param index Index of target in authorities array. + function removeAuthorizedAddressAtIndex( + address target, + uint256 index + ) + external; +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/libs/LibAssetProxyErrors.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/libs/LibAssetProxyErrors.sol new file mode 100644 index 000000000..338cb12e2 --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/libs/LibAssetProxyErrors.sol @@ -0,0 +1,36 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; + +/// @dev This contract documents the revert reasons used in the AssetProxy contracts. +/// This contract is intended to serve as a reference, but is not actually used for efficiency reasons. +contract LibAssetProxyErrors { + + /// Authorizable errors /// + string constant SENDER_NOT_AUTHORIZED = "SENDER_NOT_AUTHORIZED"; // Sender not authorized to call this method. + string constant TARGET_NOT_AUTHORIZED = "TARGET_NOT_AUTHORIZED"; // Target address not authorized to call this method. + string constant TARGET_ALREADY_AUTHORIZED = "TARGET_ALREADY_AUTHORIZED"; // Target address must not already be authorized. + string constant INDEX_OUT_OF_BOUNDS = "INDEX_OUT_OF_BOUNDS"; // Specified array index is out of bounds. + string constant AUTHORIZED_ADDRESS_MISMATCH = "AUTHORIZED_ADDRESS_MISMATCH"; // Address at index does not match given target address. + + /// Transfer errors /// + string constant INVALID_AMOUNT = "INVALID_AMOUNT"; // Transfer amount must equal 1. + string constant TRANSFER_FAILED = "TRANSFER_FAILED"; // Transfer failed. + string constant LENGTH_GREATER_THAN_131_REQUIRED = "LENGTH_GREATER_THAN_131_REQUIRED"; // Byte array must have a length greater than 0. +} diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol new file mode 100644 index 000000000..6f35bd7ec --- /dev/null +++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/mixins/MAuthorizable.sol @@ -0,0 +1,42 @@ +/* + + Copyright 2018 ZeroEx Intl. + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +*/ + +pragma solidity ^0.4.24; +pragma experimental ABIEncoderV2; + +import "../interfaces/IAuthorizable.sol"; + +contract MAuthorizable is + IAuthorizable +{ + + // Event logged when a new address is authorized. + event AuthorizedAddressAdded( + address indexed target, + address indexed caller + ); + + // Event logged when a currently authorized address is unauthorized. + event AuthorizedAddressRemoved( + address indexed target, + address indexed caller + ); + + /// @dev Only authorized addresses can invoke functions with this modifier. + modifier onlyAuthorized { revert(); _; } +} |