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input/size: assert witness size constants

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This commit introduces a new test case that asserts all of the witness
size constants currently in the codebase. We also reintroduce the
AcceptedHtlcSuccessWitnessSize and OfferedHtlcTimeoutWitnessSize
constants that were recently removed for the sake of completeness.

In asserting the witnes sizes, there were three uncovered discrepancies:
 * OfferedHtlcSuccessWitnessSize overestimated by about 30% because it
   included an extra signature in the calculation.

 * ToLocalPenaltyWitnessSize was underestimated by one byte, because it
   was missing the length byte for the OP_TRUE. This has implications
   the watchtower protocol since the client and server are assumed to
   share the same weight estimates used for signing. This commit keeps
   the current behavior, with the intention of rolling out negotiation
   for which weight estimate to use for a given session.

 * AcceptedHtlcScriptSize was underestimated by one byte because it was
   missing a length byte for the value 32 pushed on the stack when
   asserting the preimage's length. This affects all AcceptedHtlc*
   witness sizes.
This commit is contained in:
Conner Fromknecht committed 2020-04-10 15:34:27 -07:00
1 parent f2b6e2af04
commit c1b9b272cd
7 files changed
+648 -73
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input/size.go
+53 -60
View File
@@ -1,12 +1,8 @@
package input
import (
"math/big"
"github.com/btcsuite/btcd/blockchain"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/wire"
"github.com/lightningnetwork/lnd/keychain"
)
const (
@@ -94,7 +90,7 @@ const (
// - OP_CHECKMULTISIG: 1 byte
MultiSigSize = 1 + 1 + 33 + 1 + 33 + 1 + 1
// WitnessSize 222 bytes
// MultiSigWitnessSize 222 bytes
// - NumberOfWitnessElements: 1 byte
// - NilLength: 1 byte
// - sigAliceLength: 1 byte
@@ -103,7 +99,7 @@ const (
// - sigBob: 73 bytes
// - WitnessScriptLength: 1 byte
// - WitnessScript (MultiSig)
WitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + MultiSigSize
MultiSigWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + MultiSigSize
// InputSize 41 bytes
// - PreviousOutPoint:
@@ -177,7 +173,7 @@ const (
BaseCommitmentTxWeight = witnessScaleFactor * BaseCommitmentTxSize
// WitnessCommitmentTxWeight 224 weight
WitnessCommitmentTxWeight = WitnessHeaderSize + WitnessSize
WitnessCommitmentTxWeight = WitnessHeaderSize + MultiSigWitnessSize
// BaseAnchorCommitmentTxSize 225 + 43 * num-htlc-outputs bytes
// - Version: 4 bytes
@@ -264,14 +260,15 @@ const (
// - witness_script (to_local_script)
ToLocalTimeoutWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize
// ToLocalPenaltyWitnessSize 156 bytes
// ToLocalPenaltyWitnessSize 157 bytes
// - number_of_witness_elements: 1 byte
// - revocation_sig_length: 1 byte
// - revocation_sig: 73 bytes
// - OP_TRUE_length: 1 byte
// - OP_TRUE: 1 byte
// - witness_script_length: 1 byte
// - witness_script (to_local_script)
ToLocalPenaltyWitnessSize = 1 + 1 + 73 + 1 + 1 + ToLocalScriptSize
ToLocalPenaltyWitnessSize = 1 + 1 + 73 + 1 + 1 + 1 + ToLocalScriptSize
// ToRemoteConfirmedScriptSize 37 bytes
// - OP_DATA: 1 byte
@@ -289,7 +286,7 @@ const (
// - witness_script (to_remote_delayed_script)
ToRemoteConfirmedWitnessSize = 1 + 1 + 73 + 1 + ToRemoteConfirmedScriptSize
// AcceptedHtlcScriptSize 142 bytes
// AcceptedHtlcScriptSize 143 bytes
// - OP_DUP: 1 byte
// - OP_HASH160: 1 byte
// - OP_DATA: 1 byte (RIPEMD160(SHA256(revocationkey)) length)
@@ -302,6 +299,7 @@ const (
// - remotekey: 33 bytes
// - OP_SWAP: 1 byte
// - OP_SIZE: 1 byte
// - OP_DATA: 1 byte (32 length)
// - 32: 1 byte
// - OP_EQUAL: 1 byte
// - OP_IF: 1 byte
@@ -327,7 +325,7 @@ const (
// - OP_CSV: 1 byte // HTLC script types. The size won't be correct in all cases,
// - OP_DROP: 1 byte // but it is just an upper bound used for fee estimation in any case.
// - OP_ENDIF: 1 byte
AcceptedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 7*1 + 20 + 4*1 +
AcceptedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 8*1 + 20 + 4*1 +
33 + 5*1 + 4 + 8*1
// AcceptedHtlcTimeoutWitnessSize 219
@@ -349,6 +347,20 @@ const (
// - witness_script (accepted_htlc_script)
AcceptedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + AcceptedHtlcScriptSize
// AcceptedHtlcSuccessWitnessSize 322 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - preimage_length: 1 byte
// - preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (accepted_htlc_script)
AcceptedHtlcSuccessWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 +
AcceptedHtlcScriptSize
// OfferedHtlcScriptSize 136 bytes
// - OP_DUP: 1 byte
// - OP_HASH160: 1 byte
@@ -386,18 +398,27 @@ const (
// - OP_ENDIF: 1 byte
OfferedHtlcScriptSize = 3*1 + 20 + 5*1 + 33 + 10*1 + 33 + 5*1 + 20 + 7*1
// OfferedHtlcSuccessWitnessSize 320 bytes
// OfferedHtlcSuccessWitnessSize 245 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - receiver_sig_length: 1 byte
// - receiver_sig: 73 bytes
// - sender_sig_length: 1 byte
// - sender_sig: 73 bytes
// - payment_preimage_length: 1 byte
// - payment_preimage: 32 bytes
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcSuccessWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 32 + 1 + OfferedHtlcScriptSize
OfferedHtlcSuccessWitnessSize = 1 + 1 + 73 + 1 + 32 + 1 + OfferedHtlcScriptSize
// OfferedHtlcTimeoutWitnessSize 285 bytes
// - number_of_witness_elements: 1 byte
// - nil_length: 1 byte
// - sig_alice_length: 1 byte
// - sig_alice: 73 bytes
// - sig_bob_length: 1 byte
// - sig_bob: 73 bytes
// - nil_length: 1 byte
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcTimeoutWitnessSize = 1 + 1 + 1 + 73 + 1 + 73 + 1 + 1 + OfferedHtlcScriptSize
// OfferedHtlcPenaltyWitnessSize 246 bytes
// - number_of_witness_elements: 1 byte
@@ -408,53 +429,25 @@ const (
// - witness_script_length: 1 byte
// - witness_script (offered_htlc_script)
OfferedHtlcPenaltyWitnessSize = 1 + 1 + 73 + 1 + 33 + 1 + OfferedHtlcScriptSize
)
type dummySignature struct{}
func (d *dummySignature) Serialize() []byte {
// Always return worst-case signature length, excluding the one byte
// sighash flag.
return make([]byte, 73-1)
}
// dummySigner is a fake signer used for size (upper bound) calculations.
type dummySigner struct {
Signer
}
// SignOutputRaw generates a signature for the passed transaction according to
// the data within the passed SignDescriptor.
func (s *dummySigner) SignOutputRaw(tx *wire.MsgTx,
signDesc *SignDescriptor) (Signature, error) {
return &dummySignature{}, nil
}
var (
// dummyPubKey is a pubkey used in script size calculation.
dummyPubKey = btcec.PublicKey{
X: &big.Int{},
Y: &big.Int{},
}
// dummyAnchorScript is a script used for size calculation.
dummyAnchorScript, _ = CommitScriptAnchor(&dummyPubKey)
// dummyAnchorWitness is a witness used for size calculation.
dummyAnchorWitness, _ = CommitSpendAnchor(
&dummySigner{},
&SignDescriptor{
KeyDesc: keychain.KeyDescriptor{
PubKey: &dummyPubKey,
},
WitnessScript: dummyAnchorScript,
},
nil,
)
// AnchorScriptSize 40 bytes
// - pubkey_length: 1 byte
// - pubkey: 33 bytes
// - OP_CHECKSIG: 1 byte
// - OP_IFDUP: 1 byte
// - OP_NOTIF: 1 byte
// - OP_16: 1 byte
// - OP_CSV 1 byte
// - OP_ENDIF: 1 byte
AnchorScriptSize = 1 + 33 + 6*1
// AnchorWitnessSize 116 bytes
AnchorWitnessSize = dummyAnchorWitness.SerializeSize()
// - number_of_witnes_elements: 1 byte
// - signature_length: 1 byte
// - signature: 73 bytes
// - witness_script_length: 1 byte
// - witness_script (anchor_script)
AnchorWitnessSize = 1 + 1 + 73 + 1 + AnchorScriptSize
)
// EstimateCommitTxWeight estimate commitment transaction weight depending on