b196b685c9
This adds SCRIPT_VERIFY_LOW_S to STANDARD_SCRIPT_VERIFY_FLAGS which will make the node require the canonical 'low-s' encoding for ECDSA signatures when relaying or mining. Consensus behavior is unchanged. The rational is explained ina81cd96805: Absent this kind of test ECDSA is not a strong signature as given a valid signature {r, s} both that value and {r, -s mod n} are valid. These two encodings have different hashes allowing third parties a vector to change users txids. These attacks are avoided by picking a particular form as canonical and rejecting the other form(s); in the of the LOW_S rule, the smaller of the two possible S values is used. If widely deployed this change would eliminate the last remaining known vector for nuisance malleability on boring SIGHASH_ALL p2pkh transactions. On the down-side it will block most transactions made by sufficiently out of date software. Unlike the other avenues to change txids on boring transactions this one was randomly violated by all deployed bitcoin software prior to its discovery. So, while other malleability vectors where made non-standard as soon as they were discovered, this one has remained permitted. Even BIP62 did not propose applying this rule to old version transactions, but conforming implementations have become much more common since BIP62 was initially written. Bitcoin Core has produced compatible signatures sincea28fb70ein September 2013, but this didn't make it into a release until 0.9 in March 2014; Bitcoinj has done so for a similar span of time. Bitcoinjs and electrum have been more recently updated. This does not replace the need for BIP62 or similar, as miners can still cooperate to break transactions. Nor does it replace the need for wallet software to handle malleability sanely[1]. This only eliminates the cheap and irritating DOS attack. [1] On the Malleability of Bitcoin Transactions Marcin Andrychowicz, Stefan Dziembowski, Daniel Malinowski, Łukasz Mazurek http://fc15.ifca.ai/preproceedings/bitcoin/paper_9.pdf
60 lines
2.9 KiB
C++
60 lines
2.9 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2014 The Bitcoin developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_POLICY_H
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#define BITCOIN_POLICY_H
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#include "consensus/consensus.h"
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#include "script/interpreter.h"
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#include "script/standard.h"
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#include <string>
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class CCoinsViewCache;
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/** Default for -blockmaxsize and -blockminsize, which control the range of sizes the mining code will create **/
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static const unsigned int DEFAULT_BLOCK_MAX_SIZE = 750000;
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static const unsigned int DEFAULT_BLOCK_MIN_SIZE = 0;
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/** Default for -blockprioritysize, maximum space for zero/low-fee transactions **/
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static const unsigned int DEFAULT_BLOCK_PRIORITY_SIZE = 50000;
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/** The maximum size for transactions we're willing to relay/mine */
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static const unsigned int MAX_STANDARD_TX_SIZE = 100000;
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/** Maximum number of signature check operations in an IsStandard() P2SH script */
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static const unsigned int MAX_P2SH_SIGOPS = 15;
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/** The maximum number of sigops we're willing to relay/mine in a single tx */
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static const unsigned int MAX_STANDARD_TX_SIGOPS = MAX_BLOCK_SIGOPS/5;
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/**
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* Standard script verification flags that standard transactions will comply
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* with. However scripts violating these flags may still be present in valid
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* blocks and we must accept those blocks.
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*/
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static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
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SCRIPT_VERIFY_DERSIG |
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SCRIPT_VERIFY_STRICTENC |
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SCRIPT_VERIFY_MINIMALDATA |
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SCRIPT_VERIFY_NULLDUMMY |
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SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS |
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SCRIPT_VERIFY_CLEANSTACK |
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SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY |
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SCRIPT_VERIFY_LOW_S;
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/** For convenience, standard but not mandatory verify flags. */
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static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
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bool IsStandard(const CScript& scriptPubKey, txnouttype& whichType);
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/**
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* Check for standard transaction types
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* @return True if all outputs (scriptPubKeys) use only standard transaction forms
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*/
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bool IsStandardTx(const CTransaction& tx, std::string& reason);
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/**
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* Check for standard transaction types
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* @param[in] mapInputs Map of previous transactions that have outputs we're spending
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* @return True if all inputs (scriptSigs) use only standard transaction forms
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*/
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bool AreInputsStandard(const CTransaction& tx, const CCoinsViewCache& mapInputs);
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#endif // BITCOIN_POLICY_H
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