[bug]: [lncli] lncli pendingsweeps returns error unhandled witness type for input

[hsjoberg]

Background

I'm running into this error when trying to run lncli pendingsweeps or lncli wallet bumpclosefee:

[lncli] rpc error: code = Unknown desc = unhandled witness type TaprootAnchorSweepSpend for input f490999ae4fe7b53227e57b4e8e04e854a5f6cac666da625f05da389bd1eeed5:1

I'm not sure what more information I can give, just ask if you need anything more.

Your environment

• lnd version 0.17.2-beta commit=v0.17.2-beta
• Ubuntu
• bitcoind backend

Cheers
Hampus

[hsjoberg]

Just a guess, but I suppose the taproot chan anchors need to be included in the input types?

lnd/lnrpc/walletrpc/walletkit_server.go

Lines 207 to 230 in 4d8fa34

	allWitnessTypes = map[input.WitnessType]WitnessType{
	input.CommitmentTimeLock: WitnessType_COMMITMENT_TIME_LOCK,
	input.CommitmentNoDelay: WitnessType_COMMITMENT_NO_DELAY,
	input.CommitmentRevoke: WitnessType_COMMITMENT_REVOKE,
	input.HtlcOfferedRevoke: WitnessType_HTLC_OFFERED_REVOKE,
	input.HtlcAcceptedRevoke: WitnessType_HTLC_ACCEPTED_REVOKE,
	input.HtlcOfferedTimeoutSecondLevel: WitnessType_HTLC_OFFERED_TIMEOUT_SECOND_LEVEL,
	input.HtlcAcceptedSuccessSecondLevel: WitnessType_HTLC_ACCEPTED_SUCCESS_SECOND_LEVEL,
	input.HtlcOfferedRemoteTimeout: WitnessType_HTLC_OFFERED_REMOTE_TIMEOUT,
	input.HtlcAcceptedRemoteSuccess: WitnessType_HTLC_ACCEPTED_REMOTE_SUCCESS,
	input.HtlcSecondLevelRevoke: WitnessType_HTLC_SECOND_LEVEL_REVOKE,
	input.WitnessKeyHash: WitnessType_WITNESS_KEY_HASH,
	input.NestedWitnessKeyHash: WitnessType_NESTED_WITNESS_KEY_HASH,
	input.CommitmentAnchor: WitnessType_COMMITMENT_ANCHOR,
	input.HtlcOfferedTimeoutSecondLevelInputConfirmed: WitnessType_HTLC_OFFERED_TIMEOUT_SECOND_LEVEL_INPUT_CONFIRMED,
	input.HtlcAcceptedSuccessSecondLevelInputConfirmed: WitnessType_HTLC_ACCEPTED_SUCCESS_SECOND_LEVEL_INPUT_CONFIRMED,
	input.CommitSpendNoDelayTweakless: WitnessType_COMMITMENT_NO_DELAY_TWEAKLESS,
	input.CommitmentToRemoteConfirmed: WitnessType_COMMITMENT_TO_REMOTE_CONFIRMED,
	input.LeaseCommitmentTimeLock: WitnessType_LEASE_COMMITMENT_TIME_LOCK,
	input.LeaseCommitmentToRemoteConfirmed: WitnessType_LEASE_COMMITMENT_TO_REMOTE_CONFIRMED,
	input.LeaseHtlcOfferedTimeoutSecondLevel: WitnessType_LEASE_HTLC_OFFERED_TIMEOUT_SECOND_LEVEL,
	input.LeaseHtlcAcceptedSuccessSecondLevel: WitnessType_LEASE_HTLC_ACCEPTED_SUCCESS_SECOND_LEVEL,
	input.TaprootPubKeySpend: WitnessType_TAPROOT_PUB_KEY_SPEND,
	}

[hsjoberg]

It's a bit unclear to me if txgenerator.go's createSweepTx() handles Taproot.
Presumably it does, so then just adding the taproot types to allWitnessTypes should work?

[ziggie1984]

Nice catch :) You are correct you need to add the new taproot types to the walletrpc enum: WitnessType and then add them as well to the allWitnessTypes mapping. A test guarantees that the allWitnessTypes always reflects all types of the enum. (TestWitnessTypeMapping)

Do you want to do the change ?

[jimbrend]

Why are pendingsweeps related to pendingchannel close?

Why are we closing ln channels like this?

Out of curiosity, may you ELI5?

Since is not remotesweep correlated to a pending channel closure vs. the command:

lncli_pending_channels? etc. etc. via the following implementations:

e.g.

eclair*
LND,
Core Lightning?

[hsjoberg]

@jimbrend basically pendingsweeps has code to check for UTXO types, where the taproot ones are missing. So the procedure fails.

lnd/lnrpc/walletrpc/walletkit_server.go

Lines 865 to 870 in b9a8e2f

	witnessType, ok := allWitnessTypes[pendingInput.WitnessType]
	if !ok {
	return nil, fmt.Errorf("unhandled witness type %v for "+
	"input %v", pendingInput.WitnessType,
	pendingInput.OutPoint)
	}

[jimbrend]

Ok, thank you for confirming,

Unrelated just consolidating my thought process on other issue resolutions...

This is an ongoing issue with so many pendingchannel closures, I imagine this is also low-hanging fruit for malicious users targeting insecure lightning nodes.

I believe the remedy to be,
Documenting every instance of why we can't properly close channels including the following AFAIK:

• eclair, LND, Core Lightning, and other implementation mismatches
• One Lightning Node being offline and not able to accept the closure causing a zombie channel
• and all the nuances the above causes that requires us diving into manual intervention such as remotesweep commands AND

chantools which no non-technical user can dare master yet they succumb to idk-- a years time of UX troubles?

I will work on documenting a list and cross-referencing this, because this is a big issue imo. Frustrating is it not, no?

p.s. i livestreamed this in the Twitch software and development category LUL

[kaloudis]

I hit the same error running lncli wallet bumpclosefee