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watchtower/blob: move code to justice_kit_packet.go

Browse Source 
In preparation for the next commit which will introduce the `JusticeKit`
interface, here we just move the code related to building the actual
justice kit packet into a separate file.
This commit is contained in:
Elle Mouton 2023-08-23 09:55:55 +02:00
parent 204ca6cb0f
commit 048dc54110
No known key found for this signature in database
GPG Key ID: D7D916376026F177
2 changed files with 377 additions and 369 deletions
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375
watchtower/blob/justice_kit.go
View File

@ -1,98 +1,12 @@
package blob package blob
import ( import (
"bytes"
"crypto/rand"
"encoding/binary"
"errors"
"fmt"
"io"
"github.com/btcsuite/btcd/btcec/v2" "github.com/btcsuite/btcd/btcec/v2"
"github.com/btcsuite/btcd/txscript" "github.com/btcsuite/btcd/txscript"
"github.com/lightningnetwork/lnd/input" "github.com/lightningnetwork/lnd/input"
"github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/lnwire"
"golang.org/x/crypto/chacha20poly1305"
) )
const (
// NonceSize is the length of a chacha20poly1305 nonce, 24 bytes.
NonceSize = chacha20poly1305.NonceSizeX
// KeySize is the length of a chacha20poly1305 key, 32 bytes.
KeySize = chacha20poly1305.KeySize
// CiphertextExpansion is the number of bytes padded to a plaintext
// encrypted with chacha20poly1305, which comes from a 16-byte MAC.
CiphertextExpansion = 16
// V0PlaintextSize is the plaintext size of a version 0 encoded blob.
// sweep address length: 1 byte
// padded sweep address: 42 bytes
// revocation pubkey: 33 bytes
// local delay pubkey: 33 bytes
// csv delay: 4 bytes
// commit to-local revocation sig: 64 bytes
// commit to-remote pubkey: 33 bytes, maybe blank
// commit to-remote sig: 64 bytes, maybe blank
V0PlaintextSize = 274
// MaxSweepAddrSize defines the maximum sweep address size that can be
// encoded in a blob.
MaxSweepAddrSize = 42
)
// Size returns the size of the encoded-and-encrypted blob in bytes.
//
// nonce: 24 bytes
// enciphered plaintext: n bytes
// MAC: 16 bytes
func Size(blobType Type) int {
return NonceSize + PlaintextSize(blobType) + CiphertextExpansion
}
// PlaintextSize returns the size of the encoded-but-unencrypted blob in bytes.
func PlaintextSize(blobType Type) int {
switch {
case blobType.Has(FlagCommitOutputs):
return V0PlaintextSize
default:
return 0
}
}
var (
// byteOrder specifies a big-endian encoding of all integer values.
byteOrder = binary.BigEndian
// ErrUnknownBlobType signals that we don't understand the requested
// blob encoding scheme.
ErrUnknownBlobType = errors.New("unknown blob type")
// ErrCiphertextTooSmall is a decryption error signaling that the
// ciphertext is smaller than the ciphertext expansion factor.
ErrCiphertextTooSmall = errors.New(
"ciphertext is too small for chacha20poly1305",
)
// ErrNoCommitToRemoteOutput is returned when trying to retrieve the
// commit to-remote output from the blob, though none exists.
ErrNoCommitToRemoteOutput = errors.New(
"cannot obtain commit to-remote p2wkh output script from blob",
)
// ErrSweepAddressToLong is returned when trying to encode or decode a
// sweep address with length greater than the maximum length of 42
// bytes, which supports p2wkh and p2sh addresses.
ErrSweepAddressToLong = fmt.Errorf(
"sweep address must be less than or equal to %d bytes long",
MaxSweepAddrSize,
)
)
// PubKey is a 33-byte, serialized compressed public key.
type PubKey [33]byte
// JusticeKit is lé Blob of Justice. The JusticeKit contains information // JusticeKit is lé Blob of Justice. The JusticeKit contains information
// required to construct a justice transaction, that sweeps a remote party's // required to construct a justice transaction, that sweeps a remote party's
// revoked commitment transaction. It supports encryption and decryption using // revoked commitment transaction. It supports encryption and decryption using
@ -136,17 +50,18 @@ type JusticeKit struct {
// SIGHASH_ALL. // SIGHASH_ALL.
CommitToLocalSig lnwire.Sig CommitToLocalSig lnwire.Sig
// CommitToRemotePubKey is the public key in the to-remote output of the revoked // CommitToRemotePubKey is the public key in the to-remote output of the
// commitment transaction. // revoked commitment transaction.
// //
// NOTE: This value is only used if it contains a valid compressed // NOTE: This value is only used if it contains a valid compressed
// public key. // public key.
CommitToRemotePubKey PubKey CommitToRemotePubKey PubKey
// CommitToRemoteSig is a signature under CommitToRemotePubKey using SIGHASH_ALL. // CommitToRemoteSig is a signature under CommitToRemotePubKey using
// SIGHASH_ALL.
// //
// NOTE: This value is only used if CommitToRemotePubKey contains a valid // NOTE: This value is only used if CommitToRemotePubKey contains a
// compressed public key. // valid compressed public key.
CommitToRemoteSig lnwire.Sig CommitToRemoteSig lnwire.Sig
} }
@ -236,281 +151,3 @@ func (b *JusticeKit) CommitToRemoteWitnessStack() ([][]byte, error) {
return witnessStack, nil return witnessStack, nil
} }
// Encrypt encodes the blob of justice using encoding version, and then
// creates a ciphertext using chacha20poly1305 under the chosen (nonce, key)
// pair.
//
// NOTE: It is the caller's responsibility to ensure that this method is only
// called once for a given (nonce, key) pair.
func (b *JusticeKit) Encrypt(key BreachKey) ([]byte, error) {
// Encode the plaintext using the provided version, to obtain the
// plaintext bytes.
var ptxtBuf bytes.Buffer
err := b.encode(&ptxtBuf, b.BlobType)
if err != nil {
return nil, err
}
// Create a new chacha20poly1305 cipher, using a 32-byte key.
cipher, err := chacha20poly1305.NewX(key[:])
if err != nil {
return nil, err
}
// Allocate the ciphertext, which will contain the nonce, encrypted
// plaintext and MAC.
plaintext := ptxtBuf.Bytes()
ciphertext := make([]byte, Size(b.BlobType))
// Generate a random 24-byte nonce in the ciphertext's prefix.
nonce := ciphertext[:NonceSize]
if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
return nil, err
}
// Finally, encrypt the plaintext using the given nonce, storing the
// result in the ciphertext buffer.
cipher.Seal(ciphertext[NonceSize:NonceSize], nonce, plaintext, nil)
return ciphertext, nil
}
// Decrypt unenciphers a blob of justice by decrypting the ciphertext using
// chacha20poly1305 with the chosen (nonce, key) pair. The internal plaintext is
// then deserialized using the given encoding version.
func Decrypt(key BreachKey, ciphertext []byte,
blobType Type) (*JusticeKit, error) {
// Fail if the blob's overall length is less than required for the nonce
// and expansion factor.
if len(ciphertext) < NonceSize+CiphertextExpansion {
return nil, ErrCiphertextTooSmall
}
// Create a new chacha20poly1305 cipher, using a 32-byte key.
cipher, err := chacha20poly1305.NewX(key[:])
if err != nil {
return nil, err
}
// Allocate the final buffer that will contain the blob's plaintext
// bytes, which is computed by subtracting the ciphertext expansion
// factor from the blob's length.
plaintext := make([]byte, len(ciphertext)-CiphertextExpansion)
// Decrypt the ciphertext, placing the resulting plaintext in our
// plaintext buffer.
nonce := ciphertext[:NonceSize]
_, err = cipher.Open(plaintext[:0], nonce, ciphertext[NonceSize:], nil)
if err != nil {
return nil, err
}
// If decryption succeeded, we will then decode the plaintext bytes
// using the specified blob version.
boj := &JusticeKit{
BlobType: blobType,
}
err = boj.decode(bytes.NewReader(plaintext), blobType)
if err != nil {
return nil, err
}
return boj, nil
}
// encode serializes the JusticeKit according to the version, returning an
// error if the version is unknown.
func (b *JusticeKit) encode(w io.Writer, blobType Type) error {
switch {
case blobType.Has(FlagCommitOutputs):
return b.encodeV0(w)
default:
return ErrUnknownBlobType
}
}
// decode deserializes the JusticeKit according to the version, returning an
// error if the version is unknown.
func (b *JusticeKit) decode(r io.Reader, blobType Type) error {
switch {
case blobType.Has(FlagCommitOutputs):
return b.decodeV0(r)
default:
return ErrUnknownBlobType
}
}
// encodeV0 encodes the JusticeKit using the version 0 encoding scheme to the
// provided io.Writer. The encoding supports sweeping of the commit to-local
// output, and optionally the commit to-remote output. The encoding produces a
// constant-size plaintext size of 274 bytes.
//
// blob version 0 plaintext encoding:
//
// sweep address length: 1 byte
// padded sweep address: 42 bytes
// revocation pubkey: 33 bytes
// local delay pubkey: 33 bytes
// csv delay: 4 bytes
// commit to-local revocation sig: 64 bytes
// commit to-remote pubkey: 33 bytes, maybe blank
// commit to-remote sig: 64 bytes, maybe blank
func (b *JusticeKit) encodeV0(w io.Writer) error {
// Assert the sweep address length is sane.
if len(b.SweepAddress) > MaxSweepAddrSize {
return ErrSweepAddressToLong
}
// Write the actual length of the sweep address as a single byte.
err := binary.Write(w, byteOrder, uint8(len(b.SweepAddress)))
if err != nil {
return err
}
// Pad the sweep address to our maximum length of 42 bytes.
var sweepAddressBuf [MaxSweepAddrSize]byte
copy(sweepAddressBuf[:], b.SweepAddress)
// Write padded 42-byte sweep address.
_, err = w.Write(sweepAddressBuf[:])
if err != nil {
return err
}
// Write 33-byte revocation public key.
_, err = w.Write(b.RevocationPubKey[:])
if err != nil {
return err
}
// Write 33-byte local delay public key.
_, err = w.Write(b.LocalDelayPubKey[:])
if err != nil {
return err
}
// Write 4-byte CSV delay.
err = binary.Write(w, byteOrder, b.CSVDelay)
if err != nil {
return err
}
// Write 64-byte revocation signature for commit to-local output.
_, err = w.Write(b.CommitToLocalSig.RawBytes())
if err != nil {
return err
}
// Write 33-byte commit to-remote public key, which may be blank.
_, err = w.Write(b.CommitToRemotePubKey[:])
if err != nil {
return err
}
// Write 64-byte commit to-remote signature, which may be blank.
_, err = w.Write(b.CommitToRemoteSig.RawBytes())
return err
}
// decodeV0 reconstructs a JusticeKit from the io.Reader, using version 0
// encoding scheme. This will parse a constant size input stream of 274 bytes to
// recover information for the commit to-local output, and possibly the commit
// to-remote output.
//
// blob version 0 plaintext encoding:
//
// sweep address length: 1 byte
// padded sweep address: 42 bytes
// revocation pubkey: 33 bytes
// local delay pubkey: 33 bytes
// csv delay: 4 bytes
// commit to-local revocation sig: 64 bytes
// commit to-remote pubkey: 33 bytes, maybe blank
// commit to-remote sig: 64 bytes, maybe blank
func (b *JusticeKit) decodeV0(r io.Reader) error {
// Read the sweep address length as a single byte.
var sweepAddrLen uint8
err := binary.Read(r, byteOrder, &sweepAddrLen)
if err != nil {
return err
}
// Assert the sweep address length is sane.
if sweepAddrLen > MaxSweepAddrSize {
return ErrSweepAddressToLong
}
// Read padded 42-byte sweep address.
var sweepAddressBuf [MaxSweepAddrSize]byte
_, err = io.ReadFull(r, sweepAddressBuf[:])
if err != nil {
return err
}
// Parse sweep address from padded buffer.
b.SweepAddress = make([]byte, sweepAddrLen)
copy(b.SweepAddress, sweepAddressBuf[:])
// Read 33-byte revocation public key.
_, err = io.ReadFull(r, b.RevocationPubKey[:])
if err != nil {
return err
}
// Read 33-byte local delay public key.
_, err = io.ReadFull(r, b.LocalDelayPubKey[:])
if err != nil {
return err
}
// Read 4-byte CSV delay.
err = binary.Read(r, byteOrder, &b.CSVDelay)
if err != nil {
return err
}
// Read 64-byte revocation signature for commit to-local output.
var localSig [64]byte
_, err = io.ReadFull(r, localSig[:])
if err != nil {
return err
}
b.CommitToLocalSig, err = lnwire.NewSigFromWireECDSA(localSig[:])
if err != nil {
return err
}
var (
commitToRemotePubkey PubKey
commitToRemoteSig [64]byte
)
// Read 33-byte commit to-remote public key, which may be discarded.
_, err = io.ReadFull(r, commitToRemotePubkey[:])
if err != nil {
return err
}
// Read 64-byte commit to-remote signature, which may be discarded.
_, err = io.ReadFull(r, commitToRemoteSig[:])
if err != nil {
return err
}
// Only populate the commit to-remote fields in the decoded blob if a
// valid compressed public key was read from the reader.
if btcec.IsCompressedPubKey(commitToRemotePubkey[:]) {
b.CommitToRemotePubKey = commitToRemotePubkey
b.CommitToRemoteSig, err = lnwire.NewSigFromWireECDSA(
commitToRemoteSig[:],
)
if err != nil {
return err
}
}
return nil
}

371
watchtower/blob/justice_kit_packet.go Normal file
View File

@ -0,0 +1,371 @@
package blob
import (
"bytes"
"crypto/rand"
"encoding/binary"
"errors"
"fmt"
"io"
"github.com/btcsuite/btcd/btcec/v2"
"github.com/lightningnetwork/lnd/lnwire"
"golang.org/x/crypto/chacha20poly1305"
)
const (
// NonceSize is the length of a chacha20poly1305 nonce, 24 bytes.
NonceSize = chacha20poly1305.NonceSizeX
// KeySize is the length of a chacha20poly1305 key, 32 bytes.
KeySize = chacha20poly1305.KeySize
// CiphertextExpansion is the number of bytes padded to a plaintext
// encrypted with chacha20poly1305, which comes from a 16-byte MAC.
CiphertextExpansion = 16
// V0PlaintextSize is the plaintext size of a version 0 encoded blob.
// sweep address length: 1 byte
// padded sweep address: 42 bytes
// revocation pubkey: 33 bytes
// local delay pubkey: 33 bytes
// csv delay: 4 bytes
// commit to-local revocation sig: 64 bytes
// commit to-remote pubkey: 33 bytes, maybe blank
// commit to-remote sig: 64 bytes, maybe blank
V0PlaintextSize = 274
// MaxSweepAddrSize defines the maximum sweep address size that can be
// encoded in a blob.
MaxSweepAddrSize = 42
)
var (
// byteOrder specifies a big-endian encoding of all integer values.
byteOrder = binary.BigEndian
// ErrUnknownBlobType signals that we don't understand the requested
// blob encoding scheme.
ErrUnknownBlobType = errors.New("unknown blob type")
// ErrCiphertextTooSmall is a decryption error signaling that the
// ciphertext is smaller than the ciphertext expansion factor.
ErrCiphertextTooSmall = errors.New(
"ciphertext is too small for chacha20poly1305",
)
// ErrNoCommitToRemoteOutput is returned when trying to retrieve the
// commit to-remote output from the blob, though none exists.
ErrNoCommitToRemoteOutput = errors.New(
"cannot obtain commit to-remote p2wkh output script from blob",
)
// ErrSweepAddressToLong is returned when trying to encode or decode a
// sweep address with length greater than the maximum length of 42
// bytes, which supports p2wkh and p2sh addresses.
ErrSweepAddressToLong = fmt.Errorf(
"sweep address must be less than or equal to %d bytes long",
MaxSweepAddrSize,
)
)
// Size returns the size of the encoded-and-encrypted blob in bytes.
//
// nonce: 24 bytes
// enciphered plaintext: n bytes
// MAC: 16 bytes
func Size(blobType Type) int {
return NonceSize + PlaintextSize(blobType) + CiphertextExpansion
}
// PlaintextSize returns the size of the encoded-but-unencrypted blob in bytes.
func PlaintextSize(blobType Type) int {
switch {
case blobType.Has(FlagCommitOutputs):
return V0PlaintextSize
default:
return 0
}
}
// PubKey is a 33-byte, serialized compressed public key.
type PubKey [33]byte
// Encrypt encodes the blob of justice using encoding version, and then
// creates a ciphertext using chacha20poly1305 under the chosen (nonce, key)
// pair.
//
// NOTE: It is the caller's responsibility to ensure that this method is only
// called once for a given (nonce, key) pair.
func (b *JusticeKit) Encrypt(key BreachKey) ([]byte, error) {
// Encode the plaintext using the provided version, to obtain the
// plaintext bytes.
var ptxtBuf bytes.Buffer
err := b.encode(&ptxtBuf, b.BlobType)
if err != nil {
return nil, err
}
// Create a new chacha20poly1305 cipher, using a 32-byte key.
cipher, err := chacha20poly1305.NewX(key[:])
if err != nil {
return nil, err
}
// Allocate the ciphertext, which will contain the nonce, encrypted
// plaintext and MAC.
plaintext := ptxtBuf.Bytes()
ciphertext := make([]byte, Size(b.BlobType))
// Generate a random 24-byte nonce in the ciphertext's prefix.
nonce := ciphertext[:NonceSize]
if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
return nil, err
}
// Finally, encrypt the plaintext using the given nonce, storing the
// result in the ciphertext buffer.
cipher.Seal(ciphertext[NonceSize:NonceSize], nonce, plaintext, nil)
return ciphertext, nil
}
// Decrypt unenciphers a blob of justice by decrypting the ciphertext using
// chacha20poly1305 with the chosen (nonce, key) pair. The internal plaintext is
// then deserialized using the given encoding version.
func Decrypt(key BreachKey, ciphertext []byte,
blobType Type) (*JusticeKit, error) {
// Fail if the blob's overall length is less than required for the nonce
// and expansion factor.
if len(ciphertext) < NonceSize+CiphertextExpansion {
return nil, ErrCiphertextTooSmall
}
// Create a new chacha20poly1305 cipher, using a 32-byte key.
cipher, err := chacha20poly1305.NewX(key[:])
if err != nil {
return nil, err
}
// Allocate the final buffer that will contain the blob's plaintext
// bytes, which is computed by subtracting the ciphertext expansion
// factor from the blob's length.
plaintext := make([]byte, len(ciphertext)-CiphertextExpansion)
// Decrypt the ciphertext, placing the resulting plaintext in our
// plaintext buffer.
nonce := ciphertext[:NonceSize]
_, err = cipher.Open(plaintext[:0], nonce, ciphertext[NonceSize:], nil)
if err != nil {
return nil, err
}
// If decryption succeeded, we will then decode the plaintext bytes
// using the specified blob version.
boj := &JusticeKit{
BlobType: blobType,
}
err = boj.decode(bytes.NewReader(plaintext), blobType)
if err != nil {
return nil, err
}
return boj, nil
}
// encode serializes the JusticeKit according to the version, returning an
// error if the version is unknown.
func (b *JusticeKit) encode(w io.Writer, blobType Type) error {
switch {
case blobType.Has(FlagCommitOutputs):
return b.encodeV0(w)
default:
return ErrUnknownBlobType
}
}
// decode deserializes the JusticeKit according to the version, returning an
// error if the version is unknown.
func (b *JusticeKit) decode(r io.Reader, blobType Type) error {
switch {
case blobType.Has(FlagCommitOutputs):
return b.decodeV0(r)
default:
return ErrUnknownBlobType
}
}
// encodeV0 encodes the JusticeKit using the version 0 encoding scheme to the
// provided io.Writer. The encoding supports sweeping of the commit to-local
// output, and optionally the commit to-remote output. The encoding produces a
// constant-size plaintext size of 274 bytes.
//
// blob version 0 plaintext encoding:
//
// sweep address length: 1 byte
// padded sweep address: 42 bytes
// revocation pubkey: 33 bytes
// local delay pubkey: 33 bytes
// csv delay: 4 bytes
// commit to-local revocation sig: 64 bytes
// commit to-remote pubkey: 33 bytes, maybe blank
// commit to-remote sig: 64 bytes, maybe blank
func (b *JusticeKit) encodeV0(w io.Writer) error {
// Assert the sweep address length is sane.
if len(b.SweepAddress) > MaxSweepAddrSize {
return ErrSweepAddressToLong
}
// Write the actual length of the sweep address as a single byte.
err := binary.Write(w, byteOrder, uint8(len(b.SweepAddress)))
if err != nil {
return err
}
// Pad the sweep address to our maximum length of 42 bytes.
var sweepAddressBuf [MaxSweepAddrSize]byte
copy(sweepAddressBuf[:], b.SweepAddress)
// Write padded 42-byte sweep address.
_, err = w.Write(sweepAddressBuf[:])
if err != nil {
return err
}
// Write 33-byte revocation public key.
_, err = w.Write(b.RevocationPubKey[:])
if err != nil {
return err
}
// Write 33-byte local delay public key.
_, err = w.Write(b.LocalDelayPubKey[:])
if err != nil {
return err
}
// Write 4-byte CSV delay.
err = binary.Write(w, byteOrder, b.CSVDelay)
if err != nil {
return err
}
// Write 64-byte revocation signature for commit to-local output.
_, err = w.Write(b.CommitToLocalSig.RawBytes())
if err != nil {
return err
}
// Write 33-byte commit to-remote public key, which may be blank.
_, err = w.Write(b.CommitToRemotePubKey[:])
if err != nil {
return err
}
// Write 64-byte commit to-remote signature, which may be blank.
_, err = w.Write(b.CommitToRemoteSig.RawBytes())
return err
}
// decodeV0 reconstructs a JusticeKit from the io.Reader, using version 0
// encoding scheme. This will parse a constant size input stream of 274 bytes to
// recover information for the commit to-local output, and possibly the commit
// to-remote output.
//
// blob version 0 plaintext encoding:
//
// sweep address length: 1 byte
// padded sweep address: 42 bytes
// revocation pubkey: 33 bytes
// local delay pubkey: 33 bytes
// csv delay: 4 bytes
// commit to-local revocation sig: 64 bytes
// commit to-remote pubkey: 33 bytes, maybe blank
// commit to-remote sig: 64 bytes, maybe blank
func (b *JusticeKit) decodeV0(r io.Reader) error {
// Read the sweep address length as a single byte.
var sweepAddrLen uint8
err := binary.Read(r, byteOrder, &sweepAddrLen)
if err != nil {
return err
}
// Assert the sweep address length is sane.
if sweepAddrLen > MaxSweepAddrSize {
return ErrSweepAddressToLong
}
// Read padded 42-byte sweep address.
var sweepAddressBuf [MaxSweepAddrSize]byte
_, err = io.ReadFull(r, sweepAddressBuf[:])
if err != nil {
return err
}
// Parse sweep address from padded buffer.
b.SweepAddress = make([]byte, sweepAddrLen)
copy(b.SweepAddress, sweepAddressBuf[:])
// Read 33-byte revocation public key.
_, err = io.ReadFull(r, b.RevocationPubKey[:])
if err != nil {
return err
}
// Read 33-byte local delay public key.
_, err = io.ReadFull(r, b.LocalDelayPubKey[:])
if err != nil {
return err
}
// Read 4-byte CSV delay.
err = binary.Read(r, byteOrder, &b.CSVDelay)
if err != nil {
return err
}
// Read 64-byte revocation signature for commit to-local output.
var localSig [64]byte
_, err = io.ReadFull(r, localSig[:])
if err != nil {
return err
}
b.CommitToLocalSig, err = lnwire.NewSigFromWireECDSA(localSig[:])
if err != nil {
return err
}
var (
commitToRemotePubkey PubKey
commitToRemoteSig [64]byte
)
// Read 33-byte commit to-remote public key, which may be discarded.
_, err = io.ReadFull(r, commitToRemotePubkey[:])
if err != nil {
return err
}
// Read 64-byte commit to-remote signature, which may be discarded.
_, err = io.ReadFull(r, commitToRemoteSig[:])
if err != nil {
return err
}
// Only populate the commit to-remote fields in the decoded blob if a
// valid compressed public key was read from the reader.
if btcec.IsCompressedPubKey(commitToRemotePubkey[:]) {
b.CommitToRemotePubKey = commitToRemotePubkey
b.CommitToRemoteSig, err = lnwire.NewSigFromWireECDSA(
commitToRemoteSig[:],
)
if err != nil {
return err
}
}
return nil
}