1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
/*
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 "../../utils/LibBytes/LibBytes.sol";
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;
}
}
|
