In this commit, we add the initial implementation of the SCB structure.
Given an SCB, and a user's seed, it will be possible to recover the
settled balanced of a channel in the event of total or partial data
loss. The SCB contains all information required to initiate the data
loss protection protocol once we restore the channel and connect to the
remote channel peer.
The primary way outside callers will interact with this package are via
the Pack and Unpack methods. Packing means writing a
serialized+encrypted version of the SCB to an io.Writer. Unpacking does
the opposite.
The encoding format itself uses the same encoding as we do on the wire
within Lightning. Each encoded backup begins with a version so we can
easily add or modify the serialization format in the future, if new
channel types appear, or we need to add/remove fields.
In this commit, we implement a series of new crypto operations that will
allow us to encrypt and decrypt a set of serialized channel backups.
Their various backups may have distinct encodings when serialized, but
to the functions defined in this file, we treat them as simple opaque
blobs.
For encryption, we utilize chacha20poly1305 with a random 24 byte nonce.
We use a larger nonce size as this can be safely generated via a CSPRNG
without fear of frequency collisions between nonces generated. To
encrypt a blob, we then use this nonce as the AD (associated data) and
prepend the nonce to the front of the ciphertext package.
For key generation, in order to ensure the user only needs their
passphrase and the backup file, we utilize the existing keychain to
derive a private key. In order to ensure that at we don't force any
hardware signer to be aware of our crypto operations, we instead opt to
utilize a public key that will be hashed to derive our private key. The
assumption here is that this key will only be exposed to this software,
and never derived as a public facing address.
In this commit, we extend the remote/receiver chain claim integration
test to assert that the on-disk representation of the invoice on the
receiving side (Carol) is marked as settled due to the claiming the HTLC
on-chain.
In this commit, we extend the htlcSuccessResolver to settle the invoice,
if any, of the corresponding on-chain HTLC sweep. This ensures that the
invoice state is consistent as when claiming the HTLC "off-chain".
Previously, contract resolvers that needed to publish a second level tx,
did not have access to the original htlc amount.
This commit reconstructs this amount from data that is already persisted
in arbitrator log.
Co-authored-by: Joost Jager <joost.jager@gmail.com>
In this commit, we update our btcwallet dependency to point to the
latest version. This latest version redefines what the wallet will
consider as an initial sync. We'll now define it by determining if the
wallet has synced up to its birthday block, rather than looking at the
number of UTXOs in the wallet. This was needed, especially for light
clients, because it would cause unnecessary rescans to happen from the
wallet's birthday if the wallet had no UTXOs.
In this commit, we verify that ChannelUpdates for newly
funded channels contain the max HTLC that we expect.
We expect the max HTLC value of each ChannelUpdate to
equal the maximum pending msats in HTLCs required by
the remote peer.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
In this commit, we set a default max HTLC value in ChannelUpdates
sent out for newly funded channels. As a result, we also default
to setting `MessageFlags` equal to 1 in each new ChannelUpdate, since
the max HTLC field is an optional field and MessageFlags indicates
the presence of optional fields within the ChannelUpdate.
For a default max HTLC, we choose the maximum msats worth of
HTLCs that can be pending (or in-flight) on our side of the channel.
The reason for this is because the spec specifies that the max
HTLC present in a ChannelUpdate must be less than or equal to
both total channel capacity and the maximum in-flight amount set
by the peer. Since this in-flight value will always be less than
or equal to channel capacity, it is a safe spec-compliant default.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
In this commit, we ensure that when we update an edge
as a result of a ChannelUpdate being returned from an
onion failure, the max htlc portion of the channel update
is included in the edge update.
This method is called to convert an EdgePolicy to a ChannelUpdate. We
make sure to carry over the max_htlc value.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
If the max_htlc field is not found when fetching a ChannelEdgePolicy
from the DB, we treat this as an unknown policy.
This is done to ensure we won't propagate invalid data further. The data
will be overwritten with a valid one when we receive an update for this
channel.
It shouldn't be very common, but old data could be lingering in the DB
added before this field was validated.
Adding this field will allow us to persist an edge's
max HTLC to disk, thus preserving it between restarts.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
In this commit, we alter the ValidateChannelUpdateAnn function in
ann_validation to validate a remote ChannelUpdate's message flags
and max HTLC field. If the message flag is set but the max HTLC
field is not set or vice versa, the ChannelUpdate fails validation.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
In this commit, we alter the gossiper test's helper method
that creates channel updates to include the max htlc field
in the ChannelUpdates it creates.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
In this commit, we modify the mockGraphSource's `AddEdge`
method to set the capacity of the edge it's adding to be a large
capacity.
This will enable us to test the validation of each ChannelUpdate's
max HTLC, since future validation checks will ensure the specified
max HTLC is less than total channel capacity.
In this commit, we add a field to the ChannelUpdate
denoting the maximum HTLC we support sending over
this channel, a field which was recently added to the
spec.
This field serves multiple purposes. In the short
term, it enables nodes to signal the largest HTLC
they're willing to carry, allows light clients who
don't verify channel existence to have some guidance
when routing HTLCs, and finally may allow nodes to
preserve a portion of bandwidth at all times.
In the long term, this field can be used by
implementations of AMP to guide payment splitting,
as it becomes apparent to a node the largest possible
HTLC one can route over a particular channel.
This PR was made possible by the merge of #1825,
which enables older nodes to properly retain and
verify signatures on updates that include new fields
(like this new max HTLC field) that they haven't yet
been updated to recognize.
In addition, the new ChannelUpdate fields are added to
the lnwire fuzzing tests.
Co-authored-by: Johan T. Halseth <johanth@gmail.com>
