Class: Bitcoin::TxChecker

Inherits:
Object show all
Defined in:
lib/bitcoin/script/tx_checker.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(tx: nil, amount: 0, input_index: nil) ⇒ TxChecker 



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# File 'lib/bitcoin/script/tx_checker.rb', line 8

def initialize(tx: nil, amount: 0, input_index: nil)
  @tx = tx
  @amount = amount
  @input_index = input_index
end

Instance Attribute Details

#amount ⇒ Object (readonly)

Returns the value of attribute amount.



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# File 'lib/bitcoin/script/tx_checker.rb', line 6

def amount
  @amount
end

#input_index ⇒ Object (readonly)

Returns the value of attribute input_index.



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# File 'lib/bitcoin/script/tx_checker.rb', line 5

def input_index
  @input_index
end

#tx ⇒ Object (readonly)

Returns the value of attribute tx.



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# File 'lib/bitcoin/script/tx_checker.rb', line 4

def tx
  @tx
end

Instance Method Details

#check_locktime(locktime) ⇒ Object 



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# File 'lib/bitcoin/script/tx_checker.rb', line 31

def check_locktime(locktime)
  # There are two kinds of nLockTime: lock-by-blockheight and lock-by-blocktime,
  # distinguished by whether nLockTime < LOCKTIME_THRESHOLD.

  # We want to compare apples to apples, so fail the script unless the type of nLockTime being tested is the same as the nLockTime in the transaction.
  unless ((tx.lock_time < LOCKTIME_THRESHOLD && locktime < LOCKTIME_THRESHOLD) ||
      (tx.lock_time >= LOCKTIME_THRESHOLD && locktime >= LOCKTIME_THRESHOLD))
    return false
  end

  # Now that we know we're comparing apples-to-apples, the comparison is a simple numeric one.
  return false if locktime > tx.lock_time

  # Finally the nLockTime feature can be disabled and thus CHECKLOCKTIMEVERIFY bypassed if every txin has been finalized by setting nSequence to maxint.
  # The transaction would be allowed into the blockchain, making the opcode ineffective.
  # Testing if this vin is not final is sufficient to prevent this condition.
  # Alternatively we could test all inputs, but testing just this input minimizes the data required to prove correct CHECKLOCKTIMEVERIFY execution.
  return false if TxIn::SEQUENCE_FINAL == tx.inputs[input_index].sequence

  true
end

#check_sequence(sequence) ⇒ Object 



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# File 'lib/bitcoin/script/tx_checker.rb', line 53

def check_sequence(sequence)
  tx_sequence = tx.inputs[input_index].sequence
  # Fail if the transaction's version number is not set high enough to trigger BIP 68 rules.
  return false if tx.version < 2

  # Sequence numbers with their most significant bit set are not consensus constrained.
  # Testing that the transaction's sequence number do not have this bit set prevents using this property to get around a CHECKSEQUENCEVERIFY check.
  return false unless tx_sequence & TxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG == 0

  # Mask off any bits that do not have consensus-enforced meaning before doing the integer comparisons
  locktime_mask = TxIn::SEQUENCE_LOCKTIME_TYPE_FLAG | TxIn::SEQUENCE_LOCKTIME_MASK
  tx_sequence_masked = tx_sequence & locktime_mask
  sequence_masked = sequence & locktime_mask

  # There are two kinds of nSequence: lock-by-blockheight and lock-by-blocktime,
  # distinguished by whether sequence_masked < TxIn#SEQUENCE_LOCKTIME_TYPE_FLAG.
  # We want to compare apples to apples, so fail the script
  # unless the type of nSequenceMasked being tested is the same as the nSequenceMasked in the transaction.
  unless ((tx_sequence_masked < TxIn::SEQUENCE_LOCKTIME_TYPE_FLAG && sequence_masked < TxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) ||
      (tx_sequence_masked >= TxIn::SEQUENCE_LOCKTIME_TYPE_FLAG && sequence_masked >= TxIn::SEQUENCE_LOCKTIME_TYPE_FLAG))
    return false
  end

  # Now that we know we're comparing apples-to-apples, the comparison is a simple numeric one.
  sequence_masked <= tx_sequence_masked
end

#check_sig(script_sig, pubkey, script_code, sig_version) ⇒ Object

check signature



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# File 'lib/bitcoin/script/tx_checker.rb', line 19

def check_sig(script_sig, pubkey, script_code, sig_version)
  return false if script_sig.empty?
  script_sig = script_sig.htb
  hash_type = script_sig[-1].unpack('C').first
  sig = script_sig[0..-2]
  sighash = tx.sighash_for_input(input_index, script_code, hash_type: hash_type,
                                 amount: amount, sig_version: sig_version)
  key_type = pubkey.start_with?('02') || pubkey.start_with?('03') ? Key::TYPES[:compressed] : Key::TYPES[:uncompressed]
  key = Key.new(pubkey: pubkey, key_type: key_type)
  key.verify(sig, sighash)
end