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75432b3c96
Standardness rules are not the same as consensus rules and it is important to keep clear separation between them, because standardness rules can and do change, while the consensus rules must not change without a specific vote, and even then, the old rules must be kept around for validation of all blocks prior to any changes introduced by a successful vote. Prior to this commit, the blockchain code which enforces the consensus rule that requires the second output of the coinbase transaction to contain the height of the block in a provably pruneable nulldata script push was relying on code in txscript/standard.go, which, as the name of the file suggests, is specifically intended for code related to standardness checks. This introduces a new function in the txscript package named ExtractCoinbaseNullData which does not rely on any of the code related to standardness checks and modifies the blockchain code accordingly to make use of the new function instead. It also removes the standardness-dependent GetNullDataContent function which is no longer used by anything. Finally, it adds tests in the txscript package to ensure the new function has the required semantics.
59 lines
2.2 KiB
Go
59 lines
2.2 KiB
Go
// Copyright (c) 2015-2016 The btcsuite developers
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// Copyright (c) 2015-2017 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package txscript
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import (
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"fmt"
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)
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const (
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// LockTimeThreshold is the number below which a lock time is
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// interpreted to be a block number. Since an average of one block
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// is generated per 10 minutes, this allows blocks for about 9,512
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// years.
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LockTimeThreshold = 5e8 // Tue Nov 5 00:53:20 1985 UTC
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// maxUniqueCoinbaseNullDataSize is the maximum number of bytes allowed
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// in the pushed data output of the coinbase output that is used to
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// ensure the coinbase has a unique hash.
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maxUniqueCoinbaseNullDataSize = 256
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)
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// ExtractCoinbaseNullData ensures the passed script is a nulldata script as
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// required by the consensus rules for the coinbase output that is used to
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// ensure the coinbase has a unique hash and returns the data it pushes.
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func ExtractCoinbaseNullData(pkScript []byte) ([]byte, error) {
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pops, err := parseScript(pkScript)
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if err != nil {
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return nil, fmt.Errorf("script parse failure")
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}
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// The nulldata in the coinbase must be a single OP_RETURN followed by a
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// data push up to maxUniqueCoinbaseNullDataSize bytes.
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//
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// NOTE: This is intentionally not using GetScriptClass and the related
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// functions because those are specifically for standardness checks which
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// can change over time and this function is specifically intended to be
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// used by the consensus rules.
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//
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// Also of note is that technically normal nulldata scripts support encoding
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// numbers via small opcodes, however the consensus rules require the block
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// height to be encoded as a 4-byte little-endian uint32 pushed via a normal
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// data push, as opposed to using the normal number handling semantics of
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// scripts, so this is specialized to accomodate that.
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if len(pops) == 1 && pops[0].opcode.value == OP_RETURN {
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return nil, nil
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}
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if len(pops) == 2 && pops[0].opcode.value == OP_RETURN &&
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pops[1].opcode.value <= OP_PUSHDATA4 && len(pops[1].data) <=
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maxUniqueCoinbaseNullDataSize {
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return pops[1].data, nil
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}
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return nil, fmt.Errorf("not a properly-formed nulldata script")
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}
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