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Diffstat (limited to 'contracts/asset-proxy/contracts/src/ERC20Proxy.sol')
| -rw-r--r-- | contracts/asset-proxy/contracts/src/ERC20Proxy.sol | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/contracts/asset-proxy/contracts/src/ERC20Proxy.sol b/contracts/asset-proxy/contracts/src/ERC20Proxy.sol new file mode 100644 index 000000000..258443bca --- /dev/null +++ b/contracts/asset-proxy/contracts/src/ERC20Proxy.sol @@ -0,0 +1,184 @@ +/* + + 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; + +import "./MixinAuthorizable.sol"; + + +contract ERC20Proxy is + MixinAuthorizable +{ + // Id of this proxy. + bytes4 constant internal PROXY_ID = bytes4(keccak256("ERC20Token(address)")); + + // solhint-disable-next-line payable-fallback + 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. + // + // (**): see table below to compute length of assetData Contents + // + // 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 | | 1 * 32 | function parameters: | + // | | 4 | 12 + 20 | 1. token address | + + // We construct calldata for the `token.transferFrom` ABI. + // The layout of this calldata is in the table below. + // + // | Area | Offset | Length | Contents | + // |----------|--------|---------|-------------------------------------| + // | Header | 0 | 4 | function selector | + // | Params | | 3 * 32 | function parameters: | + // | | 4 | | 1. from | + // | | 36 | | 2. to | + // | | 68 | | 3. amount | + + /////// Read token address from calldata /////// + // * The token address is stored in `assetData`. + // + // * The "offset to assetData" is stored at offset 4 in the calldata (table 1). + // [assetDataOffsetFromParams = calldataload(4)] + // + // * Notes that the "offset to assetData" is relative to the "Params" area of calldata; + // add 4 bytes to account for the length of the "Header" area (table 1). + // [assetDataOffsetFromHeader = assetDataOffsetFromParams + 4] + // + // * The "token address" is offset 32+4=36 bytes into "assetData" (tables 1 & 2). + // [tokenOffset = assetDataOffsetFromHeader + 36 = calldataload(4) + 4 + 36] + 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) + } + + // Revert if undefined function is called + revert(0, 0) + } + } + + /// @dev Gets the proxy id associated with the proxy address. + /// @return Proxy id. + function getProxyId() + external + pure + returns (bytes4) + { + return PROXY_ID; + } +} |