chantools scbforceclose: extract close tx from SCB and sign it #95

starius · 2023-11-16T14:03:40Z

This is part of lightningnetwork/lnd#7658 (comment) implementation.

This PR depends on lightningnetwork/lnd#8183
(Field chanbackup.Single.CloseTxInputs is needed.)

I added chantools scbforceclose command, which extracts closing tx from SCB and signs it and optionally broadcasts.

New command:

chantools scbforceclose --help

$ chantools scbforceclose --help

If you are certain that a node is offline for good (AFTER you've tried SCB!)
and a channel is still open, you can use this method to force-close your
latest state that you have in your channel.db.

!!! WARNING !!! DANGER !!! WARNING !!!

If you do this and the state that you publish is not the latest state, then
the remote node could punish you by taking the whole channel amount if they
come online before you can sweep the funds from the time locked (144 - 2000
blocks) transaction or they have a watch tower looking out for them.

This should absolutely be the last resort and you have been warned!

Usage:
chantools scbforceclose [flags]

Examples:
chantools scbforceclose --multi_file channel.backup

Flags:
--apiurl string API URL to use (must be esplora compatible) (default "https://blockstream.info/api")
--bip39 read a classic BIP39 seed and passphrase from the terminal instead of asking for lnd seed format or providing the --rootkey flag
-h, --help help for scbforceclose
--multi_backup string a hex encoded multi-channel backup obtained from exportchanbackup for force-closing channels
--multi_file string the path to a single-channel backup file (channel.backup)
--publish publish force-closing TX to the chain API instead of just printing the TX
--rootkey string BIP32 HD root key of the wallet to use for decrypting the backup and signing tx; leave empty to prompt for lnd 24 word aezeed
--single_backup string a hex encoded single channel backup obtained from exportchanbackup for force-closing channels
--single_file string the path to a single-channel backup file

Global Flags:
-r, --regtest Indicates if regtest parameters should be used
-s, --signet Indicates if the public signet parameters should be used
-t, --testnet Indicates if testnet parameters should be used

The command extracts closing transactions from SCB, signs and prints them.

Example

Here is an example of using chantools scbforceclose in testnet to sign a force closing transaction and to publish it.

chantools --testnet scbforceclose --single_backup xxx --publish --apiurl https://blockstream.info/testnet/api

$ chantools --testnet scbforceclose --single_backup xxx --publish --apiurl https://blockstream.info/testnet/api 2023-12-31 18:06:04.121 [INF] CHAN: chantools version v0.12.1 commit Input your 24-word mnemonic separated by spaces: ***

Input your cipher seed passphrase (press enter if your seed doesn't have a passphrase):

Found 1 channel backups, 1 of them have close tx.

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
If you are certain that a node is offline for good (AFTER you've tried SCB!)
and a channel is still open, you can use this method to force-close your
latest state that you have in your channel.db.

!!! WARNING !!! DANGER !!! WARNING !!!

If you do this and the state that you publish is not the latest state, then
the remote node could punish you by taking the whole channel amount if they
come online before you can sweep the funds from the time locked (144 - 2000
blocks) transaction or they have a watch tower looking out for them.

This should absolutely be the last resort and you have been warned!
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Type YES to proceed: YES
Signed transactions will be broadcasted automatically.
Type YES again to proceed: YES
xxx:0
xxxxxxxx

2023-12-31 18:06:28.796 [INF] CHAN: Published TX xxx, response: xxx

(To use --publish option in testnet, --apiurl should be adjusted. Hopefully newExplorerAPI from #107 is fixing this.)

TODOs

validate close transaction? Does the fact that it is signed and serialized imply that it is valid. I'm interested in a way to produce such transactions for all the channels just to make sure they are producible from SCB and are valid
README for scbforceclose command
deduplicate code between createSignDesc and LightningChannel.CreateSignDesc. See chantools forceclose --channeldb crashes on taproot channels: malformed signature: no header magic #108

guggero

Thanks for the two PRs!
I think both need some extra work but are on the right track.

cmd/chantools/forceclose.go

starius · 2023-12-31T20:29:43Z

I updated both PRs. Signing now happens in chantools scbforceclose. I put an example into PR's description.

@guggero Please take another look!

starius · 2024-06-18T23:44:46Z

Rebased for LND 0.18, fixed lint warnings.
Tested manually.

guggero

Great PR, looks very good.

Will test once lnd side has been updated.

guggero · 2024-06-28T11:12:47Z

cmd/chantools/scbforceclose.go

+
+	if s.CloseTxInputs == nil {
+		return nil, errors.New("channel backup does not have data " +
+			"needed to sign force sloe tx")


nit: s/sloe/close/

Fixed, moved to LND PR (commit chanbackup: add function SignCloseTx).

guggero · 2024-06-28T11:13:05Z

cmd/chantools/scbforceclose.go

+}
+
+func createTaprootNonceProducer(
+	s chanbackup.Single,


nit: formatting.

Fixed, moved to LND PR (commit chanbackup: add function SignCloseTx).

starius · 2024-07-07T04:13:13Z

Thanks for the review! I updated LND PR and this PR. The code producing signed transaction was moved to LND to use it in itest.

guggero

Love how minimal this now turned out 💯

LGTM pending some final manual tests (will attempt to do later today).

guggero

tACK, LGTM 🎉

To make things easier to debug, can you please apply the following diff as another commit? That will add the new data to the output of chantools dumpbackup.

dumpchanbackup.diff.txt

Will merge once the lnd PR is in.

guggero · 2024-07-16T19:42:34Z

cmd/chantools/scbforceclose.go

+		return errors.New("failed to read user input")
+	}
+	if strings.TrimSpace(userInput) != "YES" {
+		return errors.New("cancelled by user")


nit: improve error message slightly, perhaps something like "canceled by user, must type uppercase 'YES'"? Same below.

guggero · 2024-07-16T19:44:11Z

cmd/chantools/scbforceclose.go

+				s.FundingOutpoint, err)
+		}
+		txHex := hex.EncodeToString(buf.Bytes())
+		fmt.Println(s.FundingOutpoint)


I think we should prefix these values, otherwise it looks a bit misleading on the command line.
Now:

Type YES to proceed: YES 8821015bb99036728b00f4b1f68ab4e41d8573947f3f94fe0d4ec2f38c1f92d4:0 02000000000101d4921f8cf3c24e0dfe943f7f9473851de4b48af6b1f4008b723690b95b01218800000000000508b280044a010000000000002......

Suggestion:

Type YES to proceed: YES Channel point: 8821015bb99036728b00f4b1f68ab4e41d8573947f3f94fe0d4ec2f38c1f92d4:0 Raw transaction hex: 02000000000101d4921f8cf3c24e0dfe943f7f9473851de4b48af6b1f4008b723690b95b01218800000000000508b280044a01000000000.....

Implemented!

starius · 2024-07-17T14:20:03Z

I rebased the PR, updated go replace to the latest lightningnetwork/lnd#8183 version.

Also included the suggested patch for dump.go. @guggero I put your name in Author field of the commit.

starius · 2024-09-20T19:16:44Z

I moved function SignCloseTx from LND's PR lightningnetwork/lnd#8183 here.
Added unit tests validating that the produced transaction has a valid signature.

Remove MockSigner from Signer. MockSigner has MusigSessionManager is an embedded field, and it is the only part of MockSigner needed in Signer.

It can now be used as keychain.ECDHRing.

It will be reused in scbforceclose.

ziggie1984 · 2024-10-01T22:00:42Z

testvector for custom channels

{
    "chan_point": "85619671cb1987c80723ed457fd829f6444269a4d228ab580cd8f2176f1d4994:0",
    "chan_backup": "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"
}

RootKey Regtest:

tprv8ZgxMBicQKsPf1ujkCE39iYKKmdzD4MgdpKb3EtiJrNCnE2K4GFMtL11adjRsCwA6J1jVKndF6GXpMdSpBGev9cczcjyhrSDVVeEXmwtmCt

Dump:

(dump.BackupMulti) {
 Version: (chanbackup.MultiBackupVersion) 0,
 StaticBackups: ([]dump.BackupSingle) (len=1 cap=1) {
  (dump.BackupSingle) {
   Version: (chanbackup.SingleBackupVersion) 6,
   IsInitiator: (bool) false,
   ChainHash: (string) (len=64) "0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206",
   FundingOutpoint: (string) (len=66) "85619671cb1987c80723ed457fd829f6444269a4d228ab580cd8f2176f1d4994:0",
   ShortChannelID: (lnwire.ShortChannelID) 402:1:0,
   RemoteNodePub: (string) (len=66) "0310150ae975211a226fc85160232e238bf072a071202e58ce5d0527cda5d7e4c9",
   Addresses: ([]net.Addr) (len=2 cap=2) {
    (*net.TCPAddr)(0x14000138a50)(127.0.0.1:9636),
    (*net.TCPAddr)(0x14000138f00)(172.18.0.6:9735)
   },
   Capacity: (btcutil.Amount) 0.00100000 BTC,
   LocalChanCfg: (dump.ChannelConfig) {
    ChannelStateBounds: (channeldb.ChannelStateBounds) {
     ChanReserve: (btcutil.Amount) 0 BTC,
     MaxPendingAmount: (lnwire.MilliSatoshi) 0 mSAT,
     MinHTLC: (lnwire.MilliSatoshi) 0 mSAT,
     MaxAcceptedHtlcs: (uint16) 0
    },
    CommitmentParams: (channeldb.CommitmentParams) {
     DustLimit: (btcutil.Amount) 0 BTC,
     CsvDelay: (uint16) 144
    },
    MultiSigKey: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/0'/0/1",
     PubKey: (string) (len=5) "<nil>"
    },
    RevocationBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/1'/0/1",
     PubKey: (string) (len=5) "<nil>"
    },
    PaymentBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/3'/0/1",
     PubKey: (string) (len=5) "<nil>"
    },
    DelayBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/4'/0/1",
     PubKey: (string) (len=5) "<nil>"
    },
    HtlcBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/2'/0/1",
     PubKey: (string) (len=5) "<nil>"
    }
   },
   RemoteChanCfg: (dump.ChannelConfig) {
    ChannelStateBounds: (channeldb.ChannelStateBounds) {
     ChanReserve: (btcutil.Amount) 0 BTC,
     MaxPendingAmount: (lnwire.MilliSatoshi) 0 mSAT,
     MinHTLC: (lnwire.MilliSatoshi) 0 mSAT,
     MaxAcceptedHtlcs: (uint16) 0
    },
    CommitmentParams: (channeldb.CommitmentParams) {
     DustLimit: (btcutil.Amount) 0 BTC,
     CsvDelay: (uint16) 144
    },
    MultiSigKey: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/0'/0/0",
     PubKey: (string) (len=66) "03c1102d1b9e016d72a39226ab34fb92fe6194b2f177882f5b167926d76417e070"
    },
    RevocationBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/0'/0/0",
     PubKey: (string) (len=66) "034a07a00f89920b27d965b041084cef9619f952fd8e1bbb4699be9f7a5806c4ee"
    },
    PaymentBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/0'/0/0",
     PubKey: (string) (len=66) "02a1b59387e693774772894155f5338f1e816ea3a36c2792377738f376ba1fde53"
    },
    DelayBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/0'/0/0",
     PubKey: (string) (len=66) "02a560b80e736d1b11af80069579b0894c19b7611f53b923674e4966c43d542140"
    },
    HtlcBasePoint: (dump.KeyDescriptor) {
     Path: (string) (len=17) "m/1017'/1'/0'/0/0",
     PubKey: (string) (len=66) "02e682ecf3cc018bb1547b89a4be96e6e7df228da97078930d55dc039d8dea7d5d"
    }
   },
   ShaChainRootDesc: (dump.KeyDescriptor) {
    Path: (string) (len=17) "m/1017'/1'/5'/0/2",
    PubKey: (string) (len=5) "<nil>"
   },
   CloseTxInputs: (*dump.CloseTxInputs)(0x1400028d700)({
    CommitTx: (string) (len=274) "020000000194491d6f17f2d80c58ab28d2a4694244f629d87f45ed2307c88719cb719661850000000000a0007180024a01000000000000225120fbd9aedad03a11215960cf6de9f51e5c7f7e292e9263a3b2410c2e14e0c68229987a010000000000225120e8807a199fd42c953f63cf78a840f444d3dd65541c38afe675ac2bf49f7d975a9bf94a20",
    CommitSig: (string) (len=196) "b8343a3033969c0eafbff5d4cff2fc981d279625b6ffc14996701c2fc90d787003ada823a2beee4a33b6524b9d1c6ccf751aa26c422b7bcc19631dea5214cf71b603d4d0cfa9a508e144a6f397319f56faa64854b7829129055bbab3ecf0fd4a49a2",
    CommitHeight: (uint64) 0,
    TapscriptRoot: (string) (len=64) "28dc51f66b841a32c48f4308e212d622d7ae5af2ceccdf10f9b37eeaf3ffcae3"
   })
  }
 }
}

scbclose:

If you do this and the state that you publish is *not* the latest state, then
the remote node *could* punish you by taking the whole channel amount *if* they
come online before you can sweep the funds from the time locked (144 - 2000
blocks) transaction *or* they have a watch tower looking out for them.

**This should absolutely be the last resort and you have been warned!**
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

Type YES to proceed: YES
Channel point: 85619671cb1987c80723ed457fd829f6444269a4d228ab580cd8f2176f1d4994:0
Raw transaction hex: 0200000000010194491d6f17f2d80c58ab28d2a4694244f629d87f45ed2307c88719cb719661850000000000a0007180024a01000000000000225120fbd9aedad03a11215960cf6de9f51e5c7f7e292e9263a3b2410c2e14e0c68229987a010000000000225120e8807a199fd42c953f63cf78a840f444d3dd65541c38afe675ac2bf49f7d975a014093106f79bc27cee0105d3b77a11bf04109a33ec42e9d8c1813f48eac864f4413ef3b4551c6f22585044a4316408789e29be33aa82a2c362a4a988e02d8c1fcd99bf94a20

starius · 2024-10-02T02:25:16Z

@ziggie1984 Thanks for providing the test vector for custom channel!
Could you also post pk_script for the channel UTXO, please?
It is needed to verify the signature and can't be deduced from the data already posted.

ziggie1984 · 2024-10-02T06:30:31Z

 "vout": [
    {
      "value": 0.00100000,
      "n": 0,
      "scriptPubKey": {
        "asm": "1 559ed0f63cde7befccbd0f98fdfb1058a2a556eb33704dda981b90a5c205f742",
        "desc": "rawtr(559ed0f63cde7befccbd0f98fdfb1058a2a556eb33704dda981b90a5c205f742)#3t2jfx29",
        "hex": "5120559ed0f63cde7befccbd0f98fdfb1058a2a556eb33704dda981b90a5c205f742",
        "address": "bcrt1p2k0dpa3umea7ln9ap7v0m7cstz3224htxdcymk5crwg2tss97apqp5wtyy",
        "type": "witness_v1_taproot"
      }
    },

It provides function SignCloseTx which produces a signed force close transaction from a channel backup and private key material.

Include fields closetx, commit sig, commit height, tapscript root. That will add the new data to the output of chantools dumpbackup.

starius · 2024-10-02T13:45:17Z

@ziggie1984 Thank you! It works! I updated the testdata for scbforceclose package.

guggero · 2024-10-30T10:09:48Z

I'm going to remove my request for review until lnd v0.19.0 (non-RC) is out.

lightninglabs-deploy · 2024-11-13T11:36:36Z

@starius, remember to re-request review from reviewers when ready

This was referenced Nov 16, 2023

chanbackup, server, rpcserver: put close unsigned tx, remote signature and commit height to SCB lightningnetwork/lnd#8183

Merged

[feature]: Include last state in close summary and exportchanbackup lightningnetwork/lnd#7658

Open

starius force-pushed the close-tx-in-static-backup branch from 4530889 to 31b20eb Compare November 16, 2023 14:31

guggero self-requested a review November 27, 2023 22:51

guggero reviewed Dec 12, 2023

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starius force-pushed the close-tx-in-static-backup branch 3 times, most recently from 74d418b to 3e8ea11 Compare December 31, 2023 19:13

starius mentioned this pull request Dec 31, 2023

chantools forceclose --channeldb crashes on taproot channels: malformed signature: no header magic #108

Open

starius changed the title ~~chantools forceclose: extract close tx from SCB~~ chantools scbforceclose: extract close tx from SCB and sign it Dec 31, 2023

starius requested a review from guggero December 31, 2023 20:29

starius force-pushed the close-tx-in-static-backup branch from 3e8ea11 to dcc9b3b Compare January 2, 2024 02:39

guggero removed their request for review April 22, 2024 12:36

starius marked this pull request as draft June 3, 2024 01:56

starius force-pushed the close-tx-in-static-backup branch 2 times, most recently from b78f22b to 4b79ab4 Compare June 18, 2024 23:01

starius marked this pull request as ready for review June 18, 2024 23:44

starius requested a review from guggero June 18, 2024 23:45

guggero reviewed Jun 28, 2024

View reviewed changes

starius force-pushed the close-tx-in-static-backup branch from 4b79ab4 to 521d4c8 Compare July 7, 2024 04:10

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guggero reviewed Jul 16, 2024

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starius force-pushed the close-tx-in-static-backup branch from 521d4c8 to 1049f12 Compare July 17, 2024 14:17

starius force-pushed the close-tx-in-static-backup branch 2 times, most recently from 9474fe1 to 2f7fc42 Compare September 20, 2024 19:14

starius force-pushed the close-tx-in-static-backup branch from 2f7fc42 to 25f7bb7 Compare September 20, 2024 19:18

starius added 4 commits October 1, 2024 16:09

go.mod: depend on lnd with lightningnetwork/lnd#8183

bf5dd88

lnd: put MusigSessionManager to Signer

98fcd8a

Remove MockSigner from Signer. MockSigner has MusigSessionManager is an embedded field, and it is the only part of MockSigner needed in Signer.

lnd/signer: add ECDH method

5af2ebf

It can now be used as keychain.ECDHRing.

forceclose: factor out warnings to a const

05b187d

It will be reused in scbforceclose.

starius force-pushed the close-tx-in-static-backup branch from 25f7bb7 to 42b2824 Compare October 1, 2024 19:22

starius and others added 3 commits October 2, 2024 10:44

add package scbforceclose

7c7f092

It provides function SignCloseTx which produces a signed force close transaction from a channel backup and private key material.

new command: scbforceclose

2cae7af

dump: include close tx and related fields

a386bde

Include fields closetx, commit sig, commit height, tapscript root. That will add the new data to the output of chantools dumpbackup.

starius force-pushed the close-tx-in-static-backup branch from 42b2824 to a386bde Compare October 2, 2024 13:44

guggero self-requested a review October 6, 2024 07:41

guggero removed their request for review October 30, 2024 10:09

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chantools scbforceclose: extract close tx from SCB and sign it #95

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chantools scbforceclose: extract close tx from SCB and sign it #95

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Example

TODOs

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