AaronFiore/electrum
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check dust limits

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* on channel opening we verify that the peer's dust limit is above 354
  sat, the limit for unknown segwit versions
* we constrain the allowed scriptpubkey types for channel closing
* we check that the remote's output is above the relay dust limit for
  the collaborative close case
This commit is contained in:
bitromortac
2021-10-22 12:58:04 +02:00
parent f2f8c4533b
commit 947693c90d
4 changed files with 40 additions and 16 deletions
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8
electrum/bitcoin.py
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@@ -349,8 +349,12 @@ def relayfee(network: 'Network' = None) -> int:
# see https://github.com/bitcoin/bitcoin/blob/a62f0ed64f8bbbdfe6467ac5ce92ef5b5222d1bd/src/policy/policy.cpp#L14
DUST_LIMIT_DEFAULT_SAT_LEGACY = 546
DUST_LIMIT_DEFAULT_SAT_SEGWIT = 294
# and https://github.com/lightningnetwork/lightning-rfc/blob/7e3dce42cbe4fa4592320db6a4e06c26bb99122b/03-transactions.md#dust-limits
DUST_LIMIT_P2PKH = 546
DUST_LIMIT_P2SH = 540
DUST_LIMIT_UNKNOWN_SEGWIT = 354
DUST_LIMIT_P2WSH = 330
DUST_LIMIT_P2WPKH = 294
def dust_threshold(network: 'Network' = None) -> int:

26
electrum/lnpeer.py
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@@ -534,7 +534,7 @@ class Peer(Logger):
static_remotekey = bfh(wallet.get_public_key(addr))
else:
static_remotekey = None
dust_limit_sat = bitcoin.DUST_LIMIT_DEFAULT_SAT_LEGACY
dust_limit_sat = bitcoin.DUST_LIMIT_P2PKH
reserve_sat = max(funding_sat // 100, dust_limit_sat)
# for comparison of defaults, see
# https://github.com/ACINQ/eclair/blob/afa378fbb73c265da44856b4ad0f2128a88ae6c6/eclair-core/src/main/resources/reference.conf#L66
@@ -1697,12 +1697,7 @@ class Peer(Logger):
raise UpfrontShutdownScriptViolation("remote didn't use upfront shutdown script it commited to in channel opening")
else:
# BOLT-02 restrict the scriptpubkey to some templates:
# order by decreasing dust limit
if match_script_against_template(their_scriptpubkey, transaction.SCRIPTPUBKEY_TEMPLATE_P2PKH):
pass
elif match_script_against_template(their_scriptpubkey, transaction.SCRIPTPUBKEY_TEMPLATE_P2SH):
pass
elif self.is_shutdown_anysegwit() and match_script_against_template(their_scriptpubkey, transaction.SCRIPTPUBKEY_TEMPLATE_ANYSEGWIT):
if self.is_shutdown_anysegwit() and match_script_against_template(their_scriptpubkey, transaction.SCRIPTPUBKEY_TEMPLATE_ANYSEGWIT):
pass
elif match_script_against_template(their_scriptpubkey, transaction.SCRIPTPUBKEY_TEMPLATE_WITNESS_V0):
pass
@@ -1765,9 +1760,9 @@ class Peer(Logger):
# BOLT2: The sending node MUST set fee less than or equal to the base fee of the final ctx
max_fee = chan.get_latest_fee(LOCAL if is_local else REMOTE)
our_fee = min(our_fee, max_fee)
drop_remote = False
drop_to_remote = False
def send_closing_signed():
our_sig, closing_tx = chan.make_closing_tx(our_scriptpubkey, their_scriptpubkey, fee_sat=our_fee, drop_remote=drop_remote)
our_sig, closing_tx = chan.make_closing_tx(our_scriptpubkey, their_scriptpubkey, fee_sat=our_fee, drop_remote=drop_to_remote)
self.send_message('closing_signed', channel_id=chan.channel_id, fee_satoshis=our_fee, signature=our_sig)
def verify_signature(tx, sig):
their_pubkey = chan.config[REMOTE].multisig_key.pubkey
@@ -1788,13 +1783,22 @@ class Peer(Logger):
# verify their sig: they might have dropped their output
our_sig, closing_tx = chan.make_closing_tx(our_scriptpubkey, their_scriptpubkey, fee_sat=their_fee, drop_remote=False)
if verify_signature(closing_tx, their_sig):
drop_remote = False
drop_to_remote = False
else:
our_sig, closing_tx = chan.make_closing_tx(our_scriptpubkey, their_scriptpubkey, fee_sat=their_fee, drop_remote=True)
if verify_signature(closing_tx, their_sig):
drop_remote = True
drop_to_remote = True
else:
# this can happen if we consider our output too valuable to drop,
# but the remote drops it because it violates their dust limit
raise Exception('failed to verify their signature')
# at this point we know how the closing tx looks like
# check that their output is above their scriptpubkey's network dust limit
if not drop_to_remote:
to_remote_idx = closing_tx.get_output_idxs_from_scriptpubkey(their_scriptpubkey.hex()).pop()
to_remote_amount = closing_tx.outputs()[to_remote_idx].value
transaction.check_scriptpubkey_template_and_dust(their_scriptpubkey, to_remote_amount)
# Agree if difference is lower or equal to one (see below)
if abs(our_fee - their_fee) < 2:
our_fee = their_fee

7
electrum/lnutil.py
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@@ -40,6 +40,7 @@ COMMITMENT_TX_WEIGHT = 724
HTLC_OUTPUT_WEIGHT = 172
LN_MAX_FUNDING_SAT = pow(2, 24) - 1
DUST_LIMIT_MAX = 1000
# dummy address for fee estimation of funding tx
def ln_dummy_address():
@@ -103,10 +104,10 @@ class ChannelConfig(StoredObject):
raise Exception(f"{conf_name}. insane initial_msat={self.initial_msat}. (funding_sat={funding_sat})")
if self.reserve_sat < self.dust_limit_sat:
raise Exception(f"{conf_name}. MUST set channel_reserve_satoshis greater than or equal to dust_limit_satoshis")
# technically this could be using the lower DUST_LIMIT_DEFAULT_SAT_SEGWIT
# but other implementations are checking against this value too; also let's be conservative
if self.dust_limit_sat < bitcoin.DUST_LIMIT_DEFAULT_SAT_LEGACY:
if self.dust_limit_sat < bitcoin.DUST_LIMIT_UNKNOWN_SEGWIT:
raise Exception(f"{conf_name}. dust limit too low: {self.dust_limit_sat} sat")
if self.dust_limit_sat > DUST_LIMIT_MAX:
raise Exception(f"{conf_name}. dust limit too high: {self.dust_limit_sat} sat")
if self.reserve_sat > funding_sat // 100:
raise Exception(f"{conf_name}. reserve too high: {self.reserve_sat}, funding_sat: {funding_sat}")
if self.htlc_minimum_msat > 1_000:

15
electrum/transaction.py
View File

@@ -459,6 +459,21 @@ SCRIPTPUBKEY_TEMPLATE_P2WSH = [opcodes.OP_0, OPPushDataGeneric(lambda x: x == 32
SCRIPTPUBKEY_TEMPLATE_ANYSEGWIT = [OP_ANYSEGWIT_VERSION, OPPushDataGeneric(lambda x: x in list(range(2, 40 + 1)))]
def check_scriptpubkey_template_and_dust(scriptpubkey, amount: Optional[int]):
if match_script_against_template(scriptpubkey, SCRIPTPUBKEY_TEMPLATE_P2PKH):
dust_limit = bitcoin.DUST_LIMIT_P2PKH
elif match_script_against_template(scriptpubkey, SCRIPTPUBKEY_TEMPLATE_P2SH):
dust_limit = bitcoin.DUST_LIMIT_P2SH
elif match_script_against_template(scriptpubkey, SCRIPTPUBKEY_TEMPLATE_P2WSH):
dust_limit = bitcoin.DUST_LIMIT_P2WSH
elif match_script_against_template(scriptpubkey, SCRIPTPUBKEY_TEMPLATE_P2WPKH):
dust_limit = bitcoin.DUST_LIMIT_P2WPKH
else:
raise Exception(f'scriptpubkey does not conform to any template: {scriptpubkey.hex()}')
if amount < dust_limit:
raise Exception(f'amount ({amount}) is below dust limit for scriptpubkey type ({dust_limit})')
def match_script_against_template(script, template) -> bool:
"""Returns whether 'script' matches 'template'."""
if script is None: