In this commit, we add an additional check within
validateCommitmentSanity due to the recent change to unsigned integers
for peer balances in the channel state machine. If after evaluation
(just applying HTLC updates), the balances are negative, then we’ll
return ErrBelowChanReserve.
In this commit, we add logic to account for an edge case in the
protocol. If they initiator if unable to pay the fees for a commitment,
then their *entire* output is meant to go to fees. The recent change to
properly interpret balances as unsigned integers (within the protocol)
let to the discovery of this missed edge case.
This commit introduces changes to the validateCommitmentSanity
function to fully validate all channel constraints.
validateCommitmentSanity now validates that the
MaxPendingAmount, ChanReserve, MinHTLC, & MaxAcceptedHTLCs
limits are all adhered to during the lifetime of a channel.
When applying a set of updates, the channel constraints are
validated from the point-of-view of either the local or the
remote node, to make sure the updates will be accepted.
Co-authored-by: nsa <elzeigel@gmail.com>
This commit moves common logic used to calculate the state
of a commitment after applying a set of HTLC updates, into
the new method computeView. This method can be used when
calculating the available balance, validating the sanity
of a commitment after applying a set of updates, and also
when creating a new commitment, reducing the duplication
of this logic.
This commit adds a new boolean parameter mutateState to
evalueteHTLCView, that let us call it without neccessarily
mutating the addHeight/removeHeight of the HTLCs, which is
useful when evaluating the commitment validity without
mutating the state.
Appendix C of BOLT 03 contains a series of test vectors asserting that
commitment, HTLC success, and HTLC timeout transactions are created
correctly. Here the test cases are transcribed to Go structs and
verified.
We also break out some logic need to tests that bypass the constructor
and remove some redundant fields.
In this commit, we add the second level witness script to the
HtlcRetribution struct. We do this as it’s possible that we when
attempt to sweep funds after a channel breach, then the remote party
has already gone to the second layer. In this case, we’ll then need to
update our SignDesc and also the witness, in order to do that we need
this script that’ll get us pass the second layer P2WSH check.
In this commit, we add a new function that allows a caller to create a
UnilateralCloseSummary with the proper materials. This will be used
within a new sub-system to be added in a later commit to properly
dispatch notifications when on-chain events happen for a channel.
In this PR, we entirely remove the closeObserver from the channel state
machine. It was added very early on before most of the other aspects of
the daemon were built out. This goroutine was responsible for
dispatching notifications to outside parties if the commitment
transaction was spent at all. This had several issues, since it was
linked to the *lifetime* of the channel state machine itself. As a
result of this linkage, we had to do weird stuff like hand off in
memory pointers to the state machine in order to ensure notifications
were properly dispatched.
In this commit, we’ve added a new HtlcResolutions struct to house both
the incoming and outgoing HTLC resolutions. This struct will now be
coupled with the object that returns when we detect that a commitment
transaction was closed on chain. For incoming HTLC’s, we’ll check the
preimage cache to see if we can claim the HTLC on-chain. If we can,
then we’ll copy of the preimage, and make a proper incoming HTLC
resolution.
In this commit, we modify the OutgoingHtlcResolution struct to detect
if this is the remote party’s commitment transaction or not. With this
change, we’ll now be able to properly time out an HTLC that was
detected on the commitment transaction of the remote peer.
Additionally, we now populate the CsvDelay (if local commitment) and
the ClaimOutpoint (as we may be sweeping directly from the commitment
transaction now.
In this commit, we add a new IncomingHtlcResolution struct. This is the
opposite of the existing OutgoingHtlcResolution struct. The items in
this new struct allow callers to sweep an incoming HTLC that we know
the preimage to. These will always be created when a commitment goes
on-chain. However, if we know the preimage, then that will be populated
in place of all zeroes in the Preimage field.
In this commit, we modify both the ForceCloseSummary, and the
UnilateralClosureSummary to return the items needed to sweep the
commitment output distinctly. By doing this, it’s now possible to pass
a dedicated struct to a sub-system in order to allow it to sweep a
commitment output. As the maturity delay is a part of this new struct,
this tells the caller if this was on the local commitment (CSV
required) or on the remote commitment (no CSV required).
In this commit, we’ve added a new method to the channel state machine:
ActiveHtlcs. This method will allow callers to poll the state of the
channel to retrieve the set of HTLC’s active on *both* commitment
transactions.
In this commit, we modify the RevokeCurrentCommitment method to now
return the set of active HTLC’s. This will be used by callers in the
future to update other sub-systems when the set of HTLC’s on the
commitment changes, and can also be used on the RPC level to
synchronize systems level integration tests.
This commit fixes a nasty bug that has been lingering within lnd, and
has been noticed due to the added retransmission logic. Before this
commit, upon a restart, if we had an active HTLC and received a new
commitment update, then we would re-forward ALL active HTLC’s. This
could at times lead to a nasty cycle:
* We re-forward an HTLC already processed.
* We then notice that the time-lock is out of date (retransmitted
HTLC), so we go to fail it.
* This is detected as a replay attack, so we send an
UpdateMalformedHTLC
* This second failure ends up creating a nil entry in the log,
leading to a panic.
* Remote party disconnects.
* Upon reconnect we send again as we need to retransmit the changes,
this goes on forever.
In order to fix this, we now ensure that we only forward HTLC’s that
have been newly locked in at this next state. With this, we now avoid
the loop described above, and also ensure that we don’t accidentally
attempt an HTLC replay attack on our selves.
Fixes#528.
Fixes#545.
In this commit, we add a new detailed error that’s to be returned
when/if the remote peer sends us an invalid commit signature. The new
error contains the transaction that we attempted to validate the
signature over, the sighs, and the state number. Returning this
additional information will serve to aide in debugging any
cross-implementation issues.
In this commit, add an additional return value to
CompleteCooperativeClose. We’ll now report to the caller our final
balance in the cooperative closure transaction. We report this as
depending on if we’re the initiator or not, our final balance may not
exactly match the balance we had in the last state.
This commit fixes a lingering bug that could at times cause
incompatibilities with other implementations when attempting a
cooperative channel close. Before this commit, we would use a pointer
to the funding txin everywhere. As a result, each time we made a new
state, or verified one, we would modify the sequence field of the main
txin of the commitment transaction. Due to this if we updated the
channel, then went to do a cooperative channel closure, the sequence of
the txin would still be set to the value we used as the state hint.
To remedy this, we now copy the txin each time when making the
commitment transaction, and also the cooperative closure transaction.
This avoids accidentally mutating the txin itself.
Fixes#502.
Previously, some methods on a LightningChannel like SettleHTLC and
FailHTLC would identify HTLCs by payment hash. This would not always
work correctly if there are multiple HTLCs with the same payment hash,
so instead we change these methods to identify HTLCs by their unique
identifiers instead.
In this commit, we extend the ProcessChanSyncMsg to detect a case where
we don’t have the necessary revocation window to send out a new commit.
This can arise if the remote party sends us a new state, but we haven’t
yet fully processed their FundingLocked message yet, so we would be
unable to create a new commitment state.
We fix this by enumerating each of our actions in the case of an error.
If we get ErrNoWindow, then this indicates that we can’t give the
remote party the commitment we would like to optimistically send over.
This isn’t an issue though, as in the next round, we’ll resynchronize
our state.
In this commit, we fix an existing bug that would cause issues within
the switch due to a value not being properly set. Before this commit we
would copy a byte array into a slice without first creating the
necessary capacity for that slice. To fix this, we’ll now ensure that
the blob has the proper capacity before copying over. Several tests
have been updated to always set a fake onion blob.
In this commit, we extend the initial check within SignNextCommitment
to bail out early if we don’t yet know the commitment point of the
remote party. This prevents a class of nil pointer panics if we attempt
to create a new state without yet having received the FundingLocked
message.
In this commit, we fix an existing bug within our cooperative channel
closing transaction generation. Before this commit, we wouldn’t account
for the fee already allocated within the commitment transaction. As a
result, we would calculate the evaluated balance considering the fee
incorrectly. In this commit, we fix this by adding the commitment fee
to the balance of the initiator when crafting the closing transaction
In this commit, we fix an existing bug, as only the initiator needs to
validate any new fee updates. If the initiator sends an invalid fee,
then it will be rejected by the responder as it may put them below
their required reserve.
In this commit, we ensure that we reject any UpdateFee messages if
after applying the update, the initiator doesn’t have enough funds to
actually pay for the new commitment state.
A test has been added to exercise this new behavior.
In this commit, we update the retransmission logic to ensure that we
properly retransmit any sent UpdateFee messages as part of a state
transition. When creating a CommitDiff, if we have a pending fee
update, then we’ll add that to the set of logs updates. When restoring
the commit diff from disk, if we encounter an UpdateFee entry, then
we’ll apply that as waiting to be ACK’d and skip adding it as a log
entry.
A new test has been added to excessive this new behavior.
In this commit, we add a new ResetState method to the channel state
machine which will reset the state of the channel to `channelOpen`. We
add this as before this commit, it was possible for a channel to shift
into the closing state, the closing negotiation be cancelled for
whatever reason, resulting the the channel held by the breachArbiter
unable to act to potential on-chain events.
In this commit, we fix an existing bug that had ramifications within
the operation of the lnd daemon. Before this commit, if the Stop()
method was called, then the closeObserver would exit as well. This
means that would no longer be watching for channel breaches on-chain,
and could miss either a cooperative channel closure or an actual
contract breach.
To fix this, we now introduce a new method to stop for closeObserver:
CancelObserver(). This should ONLY be called once either: the contract
has been fully settled on-chain, or whom ever is watching the relevant
signals has a newer version of the channel that it will watch instead.
In this commit, we modify CreateCloseProposal to no longer return the
same fee passed in. In the past, this method accepted a fee rat rather
than an absolute fee, and would return the computed absolute fee. Now
that the method takes the absolute fee directly, this is unnecessary.
In this commit, we add fully verification (other than checking the
commitment point matches after the fact) of the new optional fields
added to the lnwire.ChannelReestablish message. Two scenarios can
arise: we realize the remote party is on a prior state (and possibly
lost data), or we realize that *we* are on a prior state with the
remote party verifiably proving that they’re on a newer state.
In this commit we extend the set of fields populated within the
returned lnwire.ChannelReestablish to populate the optional data loss
fields. This entails included the commitment secret of the most
recently revoked remote commitment transaction and also our current
unrevoked commitment point.
In this commit, we update all the key derivation within the state
machine to account for the recent spec change which introduces a
distinct key for usages within all HTLC scripts. This change means that
the commitment payment and delay base points, are only required to be
online in the case that a party is forced to go to chain.
We introduce an additional local tweak to the keyring for the HTLC
tweak. Additionally, two new keys have been added: a local and a remote
HTLC key. Generation of sender/receiver HTLC scripts now use the local
and remote HTLC keys rather than the “payment” key for each party.
Finally, when creating/verifying signatures for second-level HTLC
transactions, we use these the distinct HTLC keys, rather than re-using
the payment keys.
In this method we fix an existing deadlock within the unit tests when
running with the race condition detector on. We don’t need to grab the
mutex within the ProcessChanSyncMsg method as this should be the very
first method called when initializing the channel if a channel state
sync is needed.
In this commit we ensure that the channel is always able to exit by
adding a select statement with a quit case when we’re waiting on the
result of a job that was previously sent into the sigPool.
In this commit we do away with the existing availableLocalBalance
attribute and instead add a new, more accurate AvailableBalance method.
The new method will compute the available balance within the channel ,
assuming a new state was created at the instance the method was called.
This new method will now properly account for HTLC fees.
AvailableBalance is now called within AddHTLC in order to ensure we
don’t add any HTLC’s that are unable to be paid for from the PoV of the
fees on the commitment transaction.
We no longer need to manually pass in the channel delta to
AppendToRevocationLog (now called AdvanceCommitChainTail) as the
pointers on-disk will be updated atomically.
In this commit we update the RevokeCurrentCommitment method to properly
use the new database UpdateCommitment method along with properly
converting the in-memory commitment to its corresponding on-disk
format.
In this commit we complete the partially completed ReceiveReestablish
method and rename it to ProcessChanSyncMsg. The new version now
properly implements retransmission as defined within BOLT#2.
Additionally, we’ve added a new case which will optimistically try and
force a resynchronization of the commitment states if we detect we can
deliver a new commitment signature sooner than later after realizing
that we need to retransmit our last revocation message when we recevied
a new state transition.
This commit adds a new method: createCommitDiff. The method will, given
a newly constructed commitment, its signature, and HTLC signatures will
create a channeldb.CommitDiff. The CommitDiff created is to be stored
on disk, as it can be used in the case that the remote party didn’t
receive our CommitSig message and also forgot all the updates that we
queued with the update.
In this commit we complexly revamp the process of restoring all channel
state back into memory after a restart. We’ll now properly do the
following: restore the pending “dangling” commit of the remote party
into the in-memory commitment chain, re-populate all active HTLC’s back
into their respective update logs with the proper indexes/counters, and
properly restore the current commitment of the remote party back in
memory.
This commit adds a new method to the updateLog which will be used when
restoring the state of a channel from disk after a restart. This new
method will add an entry to the updateLog without incrementing either
of the counters as the HTLC already comes pre populated with its
historical index.
With these new fields, we’ll be able to properly reconstruct the log
state after a restart, as each commitment will now note both the
current HTLC and log index.
After addition of the retransmission logic in the channel link, we
should make the onion blobs persistant, the proper way to do this is
include the onion blobs in the payment descriptor rather than storing
them in the distinct struct in the channel link.
In this commit BOLT№2 retranmission logic for the channel link have
been added. Now if channel link have been initialised with the
'SyncState' field than it will send the lnwire.ChannelReestablish
message and will be waiting for receiving the same message from remote
side. Exchange of this message allow both sides understand which
updates they should exchange with each other in order sync their
states.
In this commit, we fix an existing derivation from the commitment state
machine as defined within the specification. Before this commit, we
only kept a single counter which both HTLC adds and fails/settles would
share. This was valid in the prior pre-spec iteration of the state
machine. However in the current draft of the spec, only a distinct
counter for HTLCs are used throughout.
This would cause an incompatibility, as if we mixed adds and settles
during an exchange, then our counter values would differ with other
implementations. To remedy this, we now introduce a distinct HTLC
counter and index within the updateLog.
Each Add will increment both the log counter, and the HTLC counter.
Each Settle/Fail will only increment the log counter. Inbound
Settle/Fails will index into the HTLC index as to target the proper
HTLC. The PaymentDescriptor type has been extended with an additional
field (HltcIndex) which itself tracks the index of an incoming/outgoing
HTLC.
This moves the commitment transaction generation code out of
fetchCommitmentView into createCommitmentTx. Aside from being a pretty
clean logical split, this allows the transaction generation code to be
unit tested more effectively.
Use binary.Read/Write in functions to serialize and deserialize
channel close summary and HTLC boolean data, as well as in
methods to put and fetch channel funding info. Remove lnd
implementations of readBool and writeBool as they are no
longer needed. Also fix a few minor typos.
Use sort.Slice in SignNextCommitment function in lnwallet/channel.go,
as part of the move to use new language features. Remove
sortableSignBatch type wrapper for slice of signJobs since it is
no longer needed to sort jobs according to their output indices.
Also fix a few minor typos in channel.go and sigpool.go.
This commit fixes an existing bug where we attempted to re-use the same
commitTweak value when creating an HTLC resolution. Instead, we now
create the commit tweak value factoring the key that is to be used for
signing.
This commit fixes an existing bug within extractHtlcResolutions. The
prior code would use an index to assign the returned
OutgoingHtlcResolutions into a single slice. However, this is invalid
as there are two cases where an HTLC might be skipped: if it’s an
incoming HTLC, or if the HLTC itself is dust from the PoV of the
commitment chain.
To fix this, we now instead use append to add items to the slice. This
ensure that we don’t have any “empty” items in between fully populated
items.
This commit fixes a bug wherein we would use the incorrect csvDelay
when crafting HTLC resolutions after a unilateral channel closure.
Previously, we would always use the csvDelay of the local party, as in
the force close case that’s the correct value. However, a unilateral
channel closure instead requires the _remote_ delay.
This commit fixes an existing bug when crafting the HTLC resolution in
the face of a commitment broadcast. Previously, we we’re using the
localKey which is incorrect, as directly below we properly use the
delayKey when crafting the secondLevelHtlcScript to sign.
This commit adds a new field: MaturityDelay, to the
UnilateralCloseSummary struct. This new field will be required, in an
upcoming update as it’s needed in order to properly sweep the
second-level HTLC outputs after MaturityDelay blocks has passed since
confirmation.
This commit fixes a minor bug (that doesn’t affect anything atm) when
crafting the SignDesc for sweeping breached outputs. Previously, we
would take the p2wkh script and then p2wsh-ify that, placing that into
the SignDesc. This is incorrect as the p2wkh script is “injected” into
the sighash when signing, and thus doesn’t need another encoding layer.
This commit adds an additional return value to SettleHTLC in order to
make way for an upcoming change to modify the way bandwidth status from
the link to the switch is reported.
This commit removes the current active LocalAvailableBalance method
from the channel state machine itself. We still maintain the internal
availableLocalBalance method locally as this is used to ensure that we
don’t add an HTLC which puts our available balance below zero.
This commit also adds an incoming flag to
HtlcRetribution struct to allow the breach arbiter to
generate the appropriate witness based on the htlc's
directionality.
It also ensures that the size of the htlc retribution
slice is now determined by the size of the number of
htlcs present in the revoked snapshot, which fixes a
minor bug that could lead to nil pointer deferences.
This commit fixes a bug within the HTLC construction and commitment
transaction construction that would result in HTLC _values_ within the
commitment transaction being off by a factor of 1000. This was due to
the fact that we failed to convert the amount of an HTLC, in mSAT, to
SAT before placing it as an output within the commitment transaction.
When attempt to locate the output index of a particular half, we use
the unconverted amount, meaning it was unnoticed.
This commit adds a new assertion within the TestSimpleAddSettleWorkflow
test to ensure that the HTLC is found within the commitment transaction
with the proper value in satoshi.
This commit fixes a lingering bug in the way the internal channel state
machine handled fee calculation. Previously, we would count the dust
HTLC’s that were trimmed towards the fee that the initiator paid. This
is invalid as otherwise, the initiator would always benefit from dust
HTLC’s. Instead, we now simply “donate” the dust HTLC’s to the miner in
the commitment transaction. This change puts us in compliance with
BOLT-0003.
This commit modifies the closeObserver code to populate the signDesc in
the case we have a non-trimmed balance. Additionally, we now also add a
*wire.OutPoint field to the struct in order to allow receivers of the
message to construct a witness that can spend the newly created output
to their wallet.
This commit modifies the methods that transition the state of the
channel into an active closing state. With the new commitment design,
the delivery scripts are no longer pre-committed to the initial funding
messages. Instead, the scripts are sent at the instant that either side
decides to shutdown within the Shutdown message.
This commit adds a new companion struct: OutgoingHtlcResolution to the
commitment state machine. The purpose of this struct is the provide the
caller with the information necessary to sweep all outgoing HTLC’s in
the case of a broadcast up-to-date commitment transaction.
The HTLC resolutions allow a caller to sweep an outgoing HTLC into
their wallet after the absolute timeout of the HTLc has passed. This is
a two step process, with the first portion consisting of broadcasting
the HTLC timeout transaction itself, and the second portion consisting
of claiming the HTLC itself after a CSV delay.
This commit adds awareness of active HTLC outputs to the
BreachRetribution struct. Previously, in the case of a breach, the
struct was only populated with enough information to sweep the two
commitment outputs. With this commit, the struct now has enough
information to sweep _all_ outputs within the commitment transaction.
This commit updates the central fetchCommitmentView method to manage
and derive the necessary easy required to create new commitments due to
the new state machine design within the specification. Each state now
requires us to derive a number of keys for each commitment state:
localDelay, remoteDelay, localKey, remoteKey, the commitment point, and
finally the revocation key itself.
This commit updates the set of functions tasked with generating HTLC’s
scripts for new commitments to now adhere to the new commitment
transaction design. With this change, the process of claiming an HTLC
now requires a second-level HTLC transaction, which solves a prior
issues due to the tight coupling of the timeout and delay clauses when
claiming an HTLC.
This commit adds a new method to the commitment struct:
populateHtlcIndexes. populateHtlcIndexes modifies the set of HTLC's
locked-into the target view to have full indexing information
populated. This information is required as we need to keep track of the
indexes of each HTLC in order to properly write the current state to
disk, and also to locate the PaymentDescriptor corresponding to HTLC
outputs in the commitment transaction.
We also modify toChannelDelta to take not of these new changes, and
access the appropriate index directly.
This commit modifies the way we account for dust HTLC’s within the
commitment state machine when creating and validating new states.
Previously, an HTLC was dust if the amount of the HTLC was below the
dustLimit of the commitment chain. Now, with the HTLC covenant
transaction, the value of the HTLC also needs to cover the required fee
of the HTLC covenant transaction at the specified fee rate of the
commitment chain.
As a result, we now determine if an HTLC is dust or not, only at the
commitment site, using the new htlcIsDust function.
This commit modifies the current core channel state machine in order to
may a step towards BOLT-0002 and BOLT-0003 compliance. In this change,
we abandon the prior revocation window, in favor of a fixed revocation
window of size two. The revocation window will be filled at the start
of the lifetime of the channel, and never extended from there until the
channel has been fully closed.
We now maintain two variables, the current un-revoked commitment point,
and the next commitment point to use when creating a new state. The
next commitment point must initially be inserted into the channel state
with the InitNextRevocation method.
A major difference between the prior revocation key handling is that
the remote party now instead sends us the _commitment point_ in
isolation, which we then use locally (with our revocation base point)
to create the next full revocation key for _their_ commitment
transaction.
This commit updates much of the state interaction within the
LightningChannel structure to account for the recent changes within the
chanenldb involving the OpenChannel struct, namely the introduction of
ChannelConfig and ChannelConstraints.
This commit adds the possibility for the initiator of a
channel to send the update_fee message, as specified
in BOLT#2. After the message is sent and both parties
have committed to the updated fee, all new commitment
messages in the channel will use the specified fee.
If an HTLC’s value is below a node’s dust limit, the amount for that
HTLC should be applied to to the fee used for the channel’s commitment
transaction.
This commit fixes a race condition that would at times occur in the
htlcswitch.TestChannelLinkBidirectionalOneHopPayments test case. A race
condition would occur in the goroutine running ReceiveNewCommitment
compared with the grouting that would obtain the snapshot in order to
make a forwarding decision.
We fix this by creating a new public key for each new commitment
transaction such that we complete avoid the read/write race condition.
This commit fixes a race condition that was discovered as a result of
the new htlcswitch package. The StateSnapshot method and all of the
other methods which mutate the state of the channel state machine were
using distinct mutexes. The fix is trivial: all methods accessing the
internal channel state variable now use the same mutex.
add rhash to the payment descriptor when receiving the settle htlc in
order to be able to pass it during settle htlc packet generation and
later find the user pending payment by rhash without additional hashing.
In this commit we made state machine to be responsible for returning
proper available balance - amount of satoshi which we able to use at
current moment. This will help us in constrction channel link
abstraction.
In this commit severe bug have been fixed which allows the state of the
nodes to be desychnorinesed in the moments of high htlc flow. We limit
the number of the htlc which we can add to commitment transaction
to half of the available capcity. This change fixes the bug when
commimtment transaction on the verge of being full, in this case race
condition might occures and remote htlc will be rejected, but at the
same time they will be added on remote side, the same situiation will
happen with htlc we have added, which cause the commitment transactions
to be different.
This commit changes the cooperative channel close workflow to comply
with the latest spec. This adds steps to handle and send shutdown
messages as well as moving responsibility for sending the channel close
message from the initiator to the responder.
This commit modifies the fee calculation logic when creating or
accepting a new commitment transaction to use the set FeePerKw within
the channel rather then re-query the estimator each time. The prior
behavior was benign as we currently use a static fee estimator, but the
dynamic setting this could’ve caused a state divergence.
This commit replaces the hard-coded 5000 satoshi fees with calls to the
FeeEstimator interface. This should provide a way to cleanly plug in
additional fee calculation algorithms in the future. This change
affected quite a few tests. When possible, the tests were changed to
assert amounts sent rather than balances so that fees wouldn't need to
be taken into account. There were several tests for which this wasn't
possible, so calls to the static fee calculator were made.
This commit adds the FeeEstimator interface, which can be used for
future fee calculation implementations. Currently, there is only the
StaticFeeEstimator implementation, which returns the same fee rate for
any transaction.
In order to cleanly handle shutdowns and restarts during state machine operation, the fee for the current
commitment transaction must be persisted. This allows the fee to be
reapplied when the current state is reloaded.
This commit modifies the actions of the closeObserver goroutine to
utilize a _new_ channel to send channel close details over. The
original close signal channel is still used to notify observers that a
channel _has_ been closed, but this new channel will provide a single
observer with details w.r.t _how_ a channel was closed.
This commit adds an additional field to the ForceCloseSummary that
allows observers of the channel that sends this struct to track _which_
channel the force close came from.
This commit improves the channel state machine by converting the
objective PendingUpdates method to a subjective FullySynced method
which is to be used in place of PendingUpdates. The new FullySynced
method is fully encompassing and replaces any upper state required by
the state machine which wraps this one.
The new FullySynced method is identical to PendingUpdates aside from
the fact that: it now also factors in the log message index of the
remote commitment chain, and also introduces a concept of an “owed
commitment”. A commitment chain owes a commitment if the height of the
local commitment chain is higher than that of the remote chain.
This commit removes the theirPrevPkScript field from the
LightningChannel struct all together. It’s no longer needed as the more
fundamental mutation bug has been fixed within the channel state
machine.
This commit fixes a class of bug that can arise in the channel state
machine when a very high throughput workflow is attempted. Since the
PaymentDescriptor’s within a commitment pointed directly into the log,
any changes to a payment descriptor would also be reflected in all
other ones. Due to this mutation possibility, at times, the
locateOutputIndex method would fail since the HTLC’s pkScript was
modified, causing the channel to fail.
We fix this class of bug by simply ensure that once an HTLC has been
associated with a particular commitment, then it becomes immutable.
This commit fixes a slight oversight in the current state machine which
assumes that both commitment chains are always at the same height. In a
future where we move back to allowing nodes to pipeline commitment
updates, this will not always be the case.
This commit fixes a lingering TODO within the wallet portion of the
codebase by properly adhering to the set dust limits when closing a
channel. With this new commit if a party’s current settled balance is
below their current dust-limit, then it will be omitted from the
commitment transaction.
The prior test that asserted negative outputs are rejected has been
removed as they’ll now be avoided by ensuring we omit dust outputs from
the commitment transaction.
This commit does some minor shuffling around and also adds some
additional comments to the restoreStateLogs method within the channel
state machine. After the latest merge in this area, the code has
diverged slightly from what’s considered typical within the rest of the
codebase.
It is possible that that there are multiple HTLCs with different values,
but the same public key script. As such, a check against the value should
be performed when looking for HTLC outputs in a commitment transaction.
Create a new helper method called genHtlcScript which will
generate the public key scripts for a supplied HTLC. This functionality
from addHTLC is removed, and addHTLC will instead call this new
method.
In restoreStateLogs we will regenerate the public key scripts for the
HTLCs with genHtlcScript and restore the proper values.
When an HTLC is either cancelled or settled we must properly set the
pkScript for the HTLC on the remote commitment, such that we can
generate a valid ChannelDelta.
Description of bug:
When calling ReceiveNewCommitment() we will progress through methods
fetchCommitmentView and addHTLC which will add HTLC outputs to the
commitment transaction in the local commitment chain and save the
pkScript to the relevant PaymentDescriptor which resides in the
corresponding updateLog. Finally the local commitment will be added
to the local commitment chain.
When the same user next calls SignNextCommitment we will again
progress through fetchCommitmentView and addHTLC. In addHTLC we will
now overwrite the pkScripts in the PaymentDescriptors with the
pkScript from the context of the remote commitment. When we later
call RevokeCurrentCommitment and proceed into toChannelDelta, we
will not be able to find the correct pkScript in the PaymentDescriptor
to match it against the outputs in the commitment transaction.
This will lead to the nested function locateOutputIndex returning
incorrect values.
Fixing the bug:
We introduce three new fields in PaymentDescriptor:
* ourPkScript
* theirPkScript
* theirPrevPkScript
ourPkScript will include the pkScript for the HTLC from the context
of the local commitment.
theirPkScript will take the value of the latest pkScript for the HTLC
from the context of the remote commitment.
theirPrevPkScript will take the second-latest pkScript for the HTLC
from the context of the remote commitment. This is the value we use
in toChannelDelta when we save a revoked commitment from our peer.
The appropriate value of these fields are set in the addHTLC method.
Additionally we pass a boolean value to toChannelDelta so we know
whether we are operating on a local or remote commitment and grab
the correct pkScript in locateUpdateIndex.
This commit removes all instances of the fastsha256 library and
replaces it with the sha256 library in the standard library. This
change should see a number of performance improvements as the standard
library has highly optimized assembly instructions with use vectorized
instructions as the platform supports.
If the value of the to-local output is below the dust limit, the
ForceCloseSummary should not include a sign descriptor for this output.
We also find the proper to-self output by looking for the expected public
key script and not assume that no HTLC outputs exist.
Currently non-HTLC outputs will be accepted in the commitment
transaction as long as it is non-zero. We change this by not allowing
outputs with a value lower than the dust limit. The value of such
an output will go towards transaction fees.
This commit fixes a class of bug that currently exists within the
cooperative closure methods for the channel state machine. As an
example, due to the current hard coded fees, if one of the outputs
generated within the generated closure transaction has a negative
output, then the initiating node would gladly forward this to the
remote node. The remote node would then reject the closure as the
transaction is invalid. However, the act of completing the closure
would cause the remote node’s state machine to shift into a “closed”
state. As a result, any further closure attempts by the first node
(force or regular) would go unnoticed by the remote node.
We fix this issue by ensuring the transaction is “sane” before
initiating of completing a cooperative channel closure.
At test case has been added exercising the particular erroneous case
reported by “moli” on IRC.
This commit avoids a class of bug wherein the state of the channel
would be marked as closing enough though an error occurred somewhere in
the function. The bug was due to the fact that the channel `status` was
shifted before any actual logic within the function(s) were executed.
We fix this bug by _only_ shifting the channel status once the function
has completed without any error.
This commit adds a new method to the channel’s state machine:
NextRevocationKey. This method is being added in preparation for the
upcoming change to switch to the commitment transaction format outlined
in the spec. When this comes to pass, the ExtendRevocationWindow method
will be removed, as it will no longer be needed.
The NextRevocationKey method will be needed as to conform to the spec,
we’ll need to send the next revocation key within the `fundingLocked`
message.
In this commit the initial implementation of revocation hash
generation 'elkrem' was replaced with 'shachain' Rusty Russel
implementation which currently enshrined in the spec. This alghoritm has
the same asymptotic characteristics but has more complex scheme
to determine wish hash we can drop and what needs to be stored
in order to be able to achive full compression.
Fix SetStateNumHint and GetStateNumHint to properly
set and get the stateNumHints using the lower 24 bits
of the locktime of the commitment transaction as the
lower 24 bits of the obfuscated state number and the
lower 24 bits of the sequence field as the higher 24
bits.
This commit adds an additional case of the closeObserver that will
properly handle the case of a channel being closed by a de-sync’d
commitment transaction from the PoV of the local node. In the case of a
minor 1-state divergence, the commitment transaction broadcast by the
remote node will be 1 state ahead of the commitment transaction we have
locally. This should be seen as a regular unilateral close as they
remote peer didn’t violate the channel contract in any way.
We address this case by changing the `==` to a `>=`.
This commit updates the internal channel state machine to the one as
described within the spec and currently implemented within the rest of
the other Lightning implementations.
At a high level the following modifications have been made:
* When signing we no loner include the index of the remote party’s
log
that our signature covers. Instead we include ALL of our current
updates, but only the updates of the remote party that we’ve
ACK’d.
* A pending change is considered ACK’d once a revocation message
has been received, locking in the changes in the remote party’s
commitment transaction.
* When sending a new commitment, we remember the index of our
log at that point so we can mark that portion of the log as ACK’d
once we receive a revocation message from the remote party.
* When receiving a new commitment signature, we include ALL of
the remote party’s changes that we’ve received but only our set
of changes that’ve been ACK’d by the remote party.
* Implicitly a revocation message now also implicitly serves to ACK
all the changes that were included in the CommitSig message
received before it.
The resulting change is a rather minor diff. However, with this state
machine it’s important to note that the order to sig/revoke messages
has been swapped. A proper exchange now looks like the following:
* Alice -> Add, Add, Add
* Alice -> Sig
* Revoke <- Bob
* Sig <- Bob
* Alice -> Revoke
One other thing that’s worth noting is that with this state machine,
since what’s included in an update is implicit, both side may need to
at times send a new commitment update in the case of a concurrent state
transition initiated by both sides.
Finally, all counters/indexes have been made 64-bit integers in order
to properly match the spec.
This commit adds a new struct to the channel state machine: updateLog.
updateLog encapsulates the update log linked list itself, a series of
new counters we’ll need in order to switch to the spec’s state machine
and also the index into the log itself. This new struct serves to
simplify much of the logic surrounding the update log and also
elminates a bit of code duplication within the current state machine.
This commit only adds the new struct. The rest of the state machine
will be updated in a later commit to use the new log and its new
counters.
This commit fixes a bug in the LightingChannel commitment state machine
which could occasionally result in the total number of satoshis sent or
received being counted twice if a redundant state transition were
initiated.
To fix this bug, we now only increment the number of satoshi
sent/recv’d iff it’s the first time the HTLC has been processed.
This commit ensures that when a channel’s closeObserver is signaled to
exit before a channel closure has been detected, then the resources
dedicated to the pending spend notification can be freed up.
rHashMap is used to store the PaymentDescriptor belonging to a received
HTLC's revocation hash. This improves the efficiency of looking up
PaymentDescriptors from their RHash whenever we want to settle or cancel
that HTLC.
This commit adds the ability to cancel a channel’s internal
closeObserver goroutine by adding a new public facing Stop method.
Additionally, we now make passing a ChainNotifier interface completely
optional. If the ChainNotifier isn’t passed in as a constructor, then
the closeObserver goroutine will never be launched. This new feature
lets the caller ensure that only a single closeObsever for any given
channels exists.
This commit removes the BlockChainIO interface as a dependency to the
LightningChannel struct as the interface is no longer used within the
operation of the LightningChannel.
This commit fixes a bug introduced by the past attempt to Make Logging
Great Again. Since we unset the curve parameters when reading/writing
the messages, if we have a lingering reference that’s active elsewhere
in the daemon, then we’ll modify that reference. To fix this, we now
explicitly set the Curve parameters in two areas.
A similar commit has been pushed to lightning-onion.
This commit modifies the closeObserver goroutine to ensure that a close
summary has been inserted into the database before signalling any
observers that a unilateral channel closure was detected. This fixes a
slight bug where a peer would force close a channel, but we wouldn’t
properly detect that and clean up the channel state if had a failed
cooperative channel closure.
This commit modifies the logic of the closeObserver slightly to not
incorrectly mark the broadcast of the commitment transaction triggered
by a cooperative channel closure as an unprompted broadcast.
This commit modifies the logic around adding cancel entries to the
update log for the commitment state machine slightly by also including
the r-hash of the HTLC that’s been cancelled in the entry for the
cancellation. With this change, we can accurately track which HTLC is
being cancelled within outer sub-systems.
This commit alters the new HTLC cancellation logic to instead allow the
canceller of an HTLC to cancel the HTLC by the payment hash rather than
the index of the HTLC.
This commit adds the ability to send/recv HTLC cancellation to the
commitment state machine. Previously this feature had been
unimplemented within the state machine, with only adds/settles working.
With this change, there’s now now no concept of “timing” out HTLC’s,
only the cancellation of HTLC’s which may be triggered for various
reasons.
This commit makes a large number of minor changes concerning API usage
within the deamon to match the latest version on the upstream btcsuite
libraries.
The major changes are the switch from wire.ShaHash to chainhash.Hash,
and that wire.NewMsgTx() now takes a paramter indicating the version of
the transaction to be created.
This commit partially rectifies a quick hack that was previously thrown
in to address an issue discovered due to possible state inconsistencies
between an active channel object and the daemon’s breachAbrbiter.
A prior commit has modified the interaction between the peer and the
breachArbiter to eliminate the state in consistency. Therefore, we no
longer need to access the database to ensure that we’re observing the
latest channel state in order to correctly make a decision about
whether a broadcast commitment transaction is a breach or not.
This commit modifies the attributes of the LightningChannel struct to
publicly expose the funding keys used within the channel for the local
and remote party. Exposing these keys publicly will allow callers to
use the keys involved to generate authenticated channel advertisements
for the routing layer.
This commit modifies the channel closing logic to remove the hard coded
bools indicating which side is attempting the closure. With the recent
changes, the initiator must always pay the channel closure fees.
This information is recently stored on disk, therefore we can use the
boolean to ensure that the closure transaction is created properly no
matter who initiates the close.
This fixes a bug.
This commit introduces a new sub-system into the daemon whose job it is
to vigilantly watch for any potential channel breaches throughout the
up-time of the daemon. The logic which was moved from the utxoNursery
in a prior commit now resides within the breachArbiter.
Upon start-up the breachArbiter will query the database for all active
channels, launching a goroutine for each channel in order to be able to
take action if a channel breach is detected. The breachArbiter is also
responsible for notifying the htlcSwitch about channel breaches in
order to black-list the breached linked during any multi-hop forwarding
decisions.
This commit adds detection of contract breaches within the commitment
state-machine for a channel. A contract breach is defined as the event
wherein a channel counter-party broadcasts a previously revoked
commitment transaction. Such an event immediately closes a channel as
the funds are now in a state of dispute.
Once a breach is detected, a snapshot of the breached state is
retrieved from the database’s revocation log. This snapshot is then
used to generate the revocation leaf used within this particular state
along with all the other information ncessary to sweep ALL active funds
within the channel. This information is encapsulated within the
BreachRetribution struct which is sent over a new channel dedicated to
sending/receiving BreachRetributions.
This commit modifies the logic within the state machine to properly
populate the new field of `OutputIndex` which the HTLC stored within a
channel delta.
With this change, in the future we’ll be able to quickly locate a
particular HTLC output in the scenario that the commitment transaction
has been broadcast on-chain and we need to sweep it. Allocating a few
extra bytes on-disk saves us from the guess-and-check logic+code
required otherwise.
This commit adds some necessary locking to ensure that all updates to
the internal state of the commitment state machine are fully serial and
thread-safe. This change is required to ensure future actions w.r.t
taking action once a revoked commitment transaction has been broadcast
are not carried out while the channel’s state is being updated.
This commit modifies the channel state machine slightly to encode the
current state number using 30-bits of the sequence number within the
commitment transaction’s only input.
Such a modification reduces up the processing time required to punish
the counter party for breaching the contract established within the
channel by broadcasting an older revoked state.
This fixes#58 with a minor modification to what was originally
suggested.
This commit modifies the lnwallet code and related tests in order to
adhere to the recent field-name change to channeldb.OpenChannel.
Instead of having the field ‘TheirLNID’ which is the sha256 of the
node’s public key, we now instead use the public key directly in all
contexts.
This commit consists of a mass variable renaming to call the pkScript being executed for segwit outputs the `witnessScript` instead of `redeemScript`. The latter naming convention is generally considered to be reserved for the context of BIP 16 execution. With segwit to be deployed soon, we should be using the correct terminology uniformly through the codebase.
In addition some minor typos throughout the codebase has been fixed.
This commit introduces the concept of a manually initiated “force”
closer within the channel state machine. A force closure is a closure
initiated by a local subsystem which broadcasts the current commitment
state directly on-chain rather than attempting to cooperatively
negotiate a closure with the remote party.
A force closure returns a ForceCloseSummary which includes all the
details required for claiming all rightfully owned outputs within the
broadcast commitment transaction.
Additionally two new publicly exported channels are introduced, one
which is closed due a locally initiated force closure, and the other
which is closed once we detect that the remote party has executed a
unilateral closure by broadcasting their version of the commitment
transaction.
This commit adds full persistence logic of the current lowest
un-revoked height within each commitment chain. The newly added
channeldb methods for record state transitions within both commitment
chains are now utilized. This un-settled HTLC state is now read upon
initialization, with the proper log entries inserted into the state
update log which reflect the garbage collected log right before the
restart.
A new set of tests have been added to exercise a few edge cases around
HTLC persistence to ensure the in-memory log is properly restored based
on the on-disk snapshot.
This commit performs a major refactor of the current wallet,
reservation, and channel code in order to call into a WalletController
implementation rather than directly into btcwallet.
The current set of wallets tests have been modified in order to test
against *all* registered WalletController implementations rather than
only btcwallet. As a result, all future WalletControllers primary need
to ensure that their implementation passes the current set of tests
(which will be expanded into the future), providing an easy path of
integration assurance.
Rather than directly holding the private keys throughout funding and
channel creation, the burden of securing keys has been shifted to the
specified WalletController and Signer interfaces. All signing is done
via the Signer interface rather than directly, increasing flexibility
dramatically.
During channel funding, rather than creating a txscript.Engine to
verify commitment signatures, regular ECDSA sig verification is now
used instead. This is faster and more efficient.
Finally certain fields/methods within ChannelReservation and
LightningChannel have been exposed publicly in order to restrict the
amount of modifications the prior tests needed to undergo in order to
support testing directly agains the WalletController interface.
This commit refactors the code within lnwallet interacting with the
ChainNotifier to accept, and call against the implementation rather
than a single concrete implementation.
LightningWallet no longer creates it’s own BtcdNotifier implementation
doing construction, now instead accepting a pre-started `ChainNotifier`
interface. All imports have been updated to reflect the new naming
scheme.
This commit adds a basic test for cooperative channel closure. The
current test ensures correctness of the cooperative closure procedure
initiated by either the channel initiator, or the channel responder.
This commit adds a new method, “PendingUpdates” to the channel state
machine which is intended to be a source to give callers a hint as to
when an additional commitment signature should be sent independent of
any request/response book keeping.
This commit patrons the state update logs properly within the channel
state machine. This change fixes a number of bugs caused by treating a
central log as two logically distinct logs. Rather than having a bit
indicating if the entry is incoming/outgoing, an entry is added to a
remote or local log depending on which modification method is used.
As a result the code is much easier to follow due to separation of
concerts.
Finally, when attempting to sign a new update with an exhausted
renovation window a distinct error is returned in order to allow higher
level callers to properly back-off and handle the protocol event.
This commit fixes a slight bug in the channel state machine’s code
executed when processing a revocation messages. With this commit after
processing a revocation, log entries which we should forward to the
downstream or upstream peer for settling/adding HTLC’s are now properly
returned.
The testa have also been updated to ensure to correct htlc’s are
returned “for forwarding”.
We no longer track HTLC’s by their r-hash within the log into the
index, as we may have multiple HTLC’s that can be redeemed by the same
pre-image. Instead we now use a separate index which is keyed by a
log-index.
Additionally, the SettleHTLC method now also returns the index of the
HTLC being settled which allows the remote party to quickly locate the
HTLC within their log.
This commit also introduces a few trace/debug log messages which will
likely be pruned in the near future
This commit finishes the initial draft of the commitment state machine.
A full re-write of the prior protocol which combines aspects of the
former ‘lnstate’ package has replaced the prior un-finished
stop-and-wait protocol.
This new protocol is designed to operate in an asynchronous environment
and to facilitate non-blocking batched and pipelined updates to the
committed channel states. The protocol is also de-synchronized meaning
that either side can propose new commitment states independent of the
actions of the other party.
The state machine implemented is very similar to that of c-lightning,
however we allow multiple unrevoked commentates in order to minimize
blocking, and also to reduce latency across several hops in a
bi-directional setting.
The current implementation consists of 3 main data structures: a
commitment chain which consist of unrevoked commitment transactions
(one for each side), and a (mostly) append-only log of HTLC updates
shared between both sides. New commitments proposed index into the log
denoting which updates they include, this allows both parties to
progress chains independent of one another. Revoked commitments, reduce
the length of the chain by one, and free up space within the revocation
window.
At this point only basic tests are in place for the state machine,
however more extensive testing infrastructure along with formal proofs
using PlusCall are planned.
This commit updates the previous HTLC and commitment scripts to their
current latest evolution.
The HTLC scripts have been optimized for space savings, the
functionality itself has remained relatively unchanged. A trade off was
made to add additional bytes into the sigScript in order to avoid
extraneous CHECKSIG’s. The rationale is that an extra 1-2 bytes in the
sigScript to guide execution, are worthwhile since they’re in the
witness, and witness data may be pruned in the near future.
The primary change is within the commitment transaction itself. Instead
of using revocation hashes, we now use signature based revocation. This
saves space in the Script, and optimizes away an extra hashing
operation. Elkrem/shachain is still used but, we now use the pre-images
to homomorphically derive a public key which the other party will be
able to sign with, once we disclose the pre-image itself.
Finally, we have switched to using SHA-256 everywhere uniformly for
both revocation hashes, and payment hashes. The rationale is that the
output of ripemd160 is too small for modern security margins, and that
other coins/chains are more likely to have SHA-256 implemented, than
ripemd160.
A set of tests has also been included which contain (mostly) exhaustive
tests of all possible redemption paths for both commitment and HTLC.
This unifies some inconstancies across the code-base with hashes being
32 vs 20 bytes. All hashes, whether payment or revocation are now
uniformly 32 bytes everywhere. As a result, only OP_SHA256 will be used
within commitment and HTLC scripts. The rationale for using sha256
instead of hash160 for the HTLC payment pre-image is that alternative
chains are more likely to have sha256 implemented, rather than
ripemd160.
A forthcoming commit will update the current commitment, and HTLC
scripts.
A cooperative closure of a LightningChannel proceeds in two steps.
First, the party who wishes to close the channel sends a signature for
the closing transaction. Next, the responder reconstructs the closing
transaction identically as the initiator did using a canonical
input/output ordering, and the currently settled balance within the
channel. At this point, the responder then broadcasts the closure
transaction. It is the responsibility of the initiator to watch for
this transaction broadcast within the network to clean up any resources
they committed to the active channel.
