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69 lines
1.7 KiB
69 lines
1.7 KiB
8 years ago
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pragma solidity ^0.4.11;
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/**
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* Eliptic curve signature operations
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* Based on https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d
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*/
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library ECRecovery {
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// Duplicate Solidity's ecrecover, but catching the CALL return value
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function safeRecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) internal returns (bool, address) {
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// We do our own memory management here. Solidity uses memory offset
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// 0x40 to store the current end of memory. We write past it (as
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// writes are memory extensions), but don't update the offset so
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// Solidity will reuse it. The memory used here is only needed for
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// this context.
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bool ret;
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address addr;
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assembly {
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let size := mload(0x40)
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mstore(size, hash)
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mstore(add(size, 32), v)
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mstore(add(size, 64), r)
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mstore(add(size, 96), s)
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// NOTE: we can reuse the request memory because we deal with
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// the return code
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ret := call(3000, 1, 0, size, 128, size, 32)
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addr := mload(size)
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}
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return (ret, addr);
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}
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function recover(bytes32 hash, bytes sig) internal returns (address) {
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bytes32 r;
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bytes32 s;
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uint8 v;
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if (sig.length != 65)
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return (address(0));
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assembly {
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r := mload(add(sig, 32))
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s := mload(add(sig, 64))
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v := byte(0, mload(add(sig, 96)))
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}
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// albeit non-transactional signatures are not specified by the YP, one would expect it
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// to match the YP range of [27, 28]
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//
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// geth uses [0, 1] and some clients have followed. This might change, see:
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// https://github.com/ethereum/go-ethereum/issues/2053
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if (v < 27)
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v += 27;
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if (v != 27 && v != 28)
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return (address(0));
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bool ret;
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address addr;
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(ret, addr) = safeRecover(hash, v, r, s);
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return addr;
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}
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}
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