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SealBatch RPC endpoint accepts signed group PSBT #1295

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merged 6 commits into from
Jan 20, 2025
Merged

SealBatch RPC endpoint accepts signed group PSBT #1295

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959bc28
mintrpc: add signed_group_virtual_psbts field to SealBatchRequest
ffranr Jan 13, 2025
a98cf20
rpcserver+tapgarden: unmarshal signed group PSBTs; pass to AssetMinter
ffranr Jan 13, 2025
cbd2e9d
tapgarden: ChainPlanter extracts witness from a signed PSBT
ffranr Jan 13, 2025
358bd57
itest: update SealBatch RPC call to accept a signed PSBT
ffranr Jan 17, 2025
298326a
cmd/tapcli: add `signed_group_psbt` argument to `seal` command
ffranr Jan 17, 2025
65d1b52
docs: update guide with `--signed-group-psbt` for `seal` command
ffranr Jan 17, 2025
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18 changes: 12 additions & 6 deletions cmd/tapcli/assets.go
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Original file line number Diff line number Diff line change
Expand Up @@ -461,7 +461,16 @@ var sealBatchCommand = cli.Command{
cli.StringSliceFlag{
Name: "group_signatures",
Usage: "the asset ID and signature, separated by a " +
"colon",
"colon. This flag should not be used in " +
"conjunction with 'signed_group_psbt'; use " +
"one or the other.",
},
cli.StringSliceFlag{
Name: "signed_group_psbt",
Usage: "a signed group PSBT for a single asset group " +
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"in the batch. This flag should not be used " +
"in conjunction with 'group_signatures'; use " +
"one or the other.",
},
},
Hidden: true,
Expand All @@ -474,13 +483,10 @@ func sealBatch(ctx *cli.Context) error {
defer cleanUp()

req := &mintrpc.SealBatchRequest{
ShortResponse: ctx.Bool(shortResponseName),
ShortResponse: ctx.Bool(shortResponseName),
SignedGroupVirtualPsbts: ctx.StringSlice("signed_group_psbt"),
}

// TODO(guggero): Actually just ask for the signed PSBT back and extract
// the signature from there. We can query the pending batch to get the
// asset ID of each PSBT (can match by the unsigned transaction's input
// prev out).
sigs := ctx.StringSlice("group_signatures")
for _, witness := range sigs {
parts := strings.Split(witness, ":")
Expand Down
91 changes: 1 addition & 90 deletions docs/external-group-key.md
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Original file line number Diff line number Diff line change
Expand Up @@ -249,99 +249,10 @@ Successfully signed PSBT:
cHNidP8BAF4CAAAAATKZro+KSjqg4YQvE0bqBCbWuii3ekKAdufOGo57L8lwAAAAAAAAAAAAAQBlzR0AAAAAIlEgxoSpM86Pyu/bCRKhOc6/2TLXDGXnUnXn69FQqD8gw7cAAAAAAAEBKwBlzR0AAAAAIlEgqUflbsA2uA/P2qYe6qclsUox7koFCR3h1xkwh4+M1wQBCEIBQAv/X4PJqGyO2YzL2uJgIK+gDFGCTIFkzAq29ThWcBuW5mFIc7aQX1CBtxHSXiF8/jn+F5sWeL0pve1ZKxY7L4EAAA==
```

## Step 5b: Extract the signature from the PSBT

TODO(guggero/ffranr): Replace this step by allowing the CLI to take the signed
PSBT instead. We can list the batch to get the asset ID of each pending asset
and match the PSBT's input previous output to find out what signed PSBT belongs
to what asset (in case there are multiple).

```shell
$ bitcoin-cli decodepsbt cHNidP8BAF4CAAAAATKZro+KSjqg4YQvE0bqBCbWuii3ekKAdufOGo57L8lwAAAAAAAAAAAAAQBlzR0AAAAAIlEgxoSpM86Pyu/bCRKhOc6/2TLXDGXnUnXn69FQqD8gw7cAAAAAAAEBKwBlzR0AAAAAIlEgqUflbsA2uA/P2qYe6qclsUox7koFCR3h1xkwh4+M1wQBCEIBQAv/X4PJqGyO2YzL2uJgIK+gDFGCTIFkzAq29ThWcBuW5mFIc7aQX1CBtxHSXiF8/jn+F5sWeL0pve1ZKxY7L4EAAA==

{
"tx": {
"txid": "1994e0f5e6beee0a58f76b2f806894f94d93ea0a21c6e380b7634f76c358c38a",
"hash": "1994e0f5e6beee0a58f76b2f806894f94d93ea0a21c6e380b7634f76c358c38a",
"version": 2,
"size": 94,
"vsize": 94,
"weight": 376,
"locktime": 0,
"vin": [
{
"txid": "70c92f7b8e1acee77680427ab728bad62604ea46132f84e1a03a4a8a8fae9932",
"vout": 0,
"scriptSig": {
"asm": "",
"hex": ""
},
"sequence": 0
}
],
"vout": [
{
"value": 5.00000000,
"n": 0,
"scriptPubKey": {
"asm": "1 c684a933ce8fcaefdb0912a139cebfd932d70c65e75275e7ebd150a83f20c3b7",
"desc": "addr(bcrt1pc6z2jv7w3l9wlkcfz2snnn4lmyedwrr9uaf8telt69g2s0eqcwmsnuxkp4)#ramnsz8q",
"hex": "5120c684a933ce8fcaefdb0912a139cebfd932d70c65e75275e7ebd150a83f20c3b7",
"address": "bcrt1pc6z2jv7w3l9wlkcfz2snnn4lmyedwrr9uaf8telt69g2s0eqcwmsnuxkp4",
"type": "witness_v1_taproot"
}
}
]
},
"global_xpubs": [
],
"psbt_version": 0,
"proprietary": [
],
"unknown": {
},
"inputs": [
{
"witness_utxo": {
"amount": 5.00000000,
"scriptPubKey": {
"asm": "1 a947e56ec036b80fcfdaa61eeaa725b14a31ee4a05091de1d71930878f8cd704",
"desc": "rawtr(a947e56ec036b80fcfdaa61eeaa725b14a31ee4a05091de1d71930878f8cd704)#fnjmj6gz",
"hex": "5120a947e56ec036b80fcfdaa61eeaa725b14a31ee4a05091de1d71930878f8cd704",
"address": "bcrt1p49r72mkqx6uqln765c0w4fe9k99rrmj2q5y3mcwhrycg0ruv6uzqgnfa6h",
"type": "witness_v1_taproot"
}
},
"final_scriptwitness": [
"0bff5f83c9a86c8ed98ccbdae26020afa00c51824c8164cc0ab6f53856701b96e6614873b6905f5081b711d25e217cfe39fe179b1678bd29bded592b163b2f81"
]
}
],
"outputs": [
{
}
],
"fee": 0.00000000
}

```

We'll take the witness as the signature for the next step:

```json
"final_scriptwitness": [
"0bff5f83c9a86c8ed98ccbdae26020afa00c51824c8164cc0ab6f53856701b96e6614873b6905f5081b711d25e217cfe39fe179b1678bd29bded592b163b2f81"
]
```

## Step 6: Seal the batch with the signature

TODO(guggero/ffranr): Use signed PSBT instead, currently it's
`--group_signatures <asset_id>:<signature>`, but should be
`--signed_group_psbt` or something like that.

```shell
$ tapcli assets mint seal --group_signatures c4b0771c1bd1334bf20df5204c162702a6dc765a9cb15b1bc9e3c91e0282061b:0bff5f83c9a86c8ed98ccbdae26020afa00c51824c8164cc0ab6f53856701b96e6614873b6905f5081b711d25e217cfe39fe179b1678bd29bded592b163b2f81
$ tapcli assets mint seal --signed_group_psbt cHNidP8BAF4CAAAAATKZro+KSjqg4YQvE0bqBCbWuii3ekKAdufOGo57L8lwAAAAAAAAAAAAAQBlzR0AAAAAIlEgxoSpM86Pyu/bCRKhOc6/2TLXDGXnUnXn69FQqD8gw7cAAAAAAAEBKwBlzR0AAAAAIlEgqUflbsA2uA/P2qYe6qclsUox7koFCR3h1xkwh4+M1wQBCEIBQAv/X4PJqGyO2YzL2uJgIK+gDFGCTIFkzAq29ThWcBuW5mFIc7aQX1CBtxHSXiF8/jn+F5sWeL0pve1ZKxY7L4EAAA==
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{
"batch": {
Expand Down
66 changes: 7 additions & 59 deletions itest/utils.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,6 @@ package itest
import (
"bytes"
"context"
"fmt"
"log"
"testing"
"time"

Expand Down Expand Up @@ -32,7 +30,6 @@ import (
"github.com/lightningnetwork/lnd/lnrpc"
"github.com/lightningnetwork/lnd/lntest/node"
"github.com/lightningnetwork/lnd/lnwallet/chainfee"
"github.com/lightningnetwork/lnd/tlv"
"github.com/stretchr/testify/require"
"google.golang.org/grpc"
"google.golang.org/protobuf/proto"
Expand Down Expand Up @@ -779,38 +776,28 @@ func MintAssetExternalSigner(t *harnessTest, tapNode *tapdHarness,
callbackRes := externalSignerCallback(fundResp.Batch.UnsealedAssets)

// Extract group witness from signed PSBTs.
var groupWitnesses []*taprpc.GroupWitness
var signedGroupVirtualPsbts []string
for idx := range callbackRes {
res := callbackRes[idx]
signedPsbt := res.SignedPsbt
genesisAssetID := res.AssetID

// Sanity check signed PSBT.
require.Len(t.t, signedPsbt.Inputs, 1)
require.Len(t.t, signedPsbt.Outputs, 1)

// Extract witness from signed PSBT.
witnessStack, err := DeserializeWitnessStack(
signedPsbt.Inputs[0].FinalScriptWitness,
// Encode the signed PSBT as a string.
signedPsbtStr, err := signedPsbt.B64Encode()
require.NoError(t.t, err)
signedGroupVirtualPsbts = append(
signedGroupVirtualPsbts, signedPsbtStr,
)
if err != nil {
log.Fatalf("Failed to deserialize witness stack: %v",
err)
}

groupWitness := taprpc.GroupWitness{
GenesisId: genesisAssetID[:],
Witness: witnessStack,
}

groupWitnesses = append(groupWitnesses, &groupWitness)
}

// Seal the batch with the group witnesses.
ctxt, cancel = context.WithTimeout(ctxb, defaultWaitTimeout)

sealReq := mintrpc.SealBatchRequest{
GroupWitnesses: groupWitnesses,
SignedGroupVirtualPsbts: signedGroupVirtualPsbts,
}
sealResp, err := tapNode.SealBatch(ctxt, &sealReq)
require.NoError(t.t, err)
Expand Down Expand Up @@ -844,45 +831,6 @@ func MintAssetExternalSigner(t *harnessTest, tapNode *tapdHarness,
return batchAssets
}

// DeserializeWitnessStack deserializes a serialized witness stack into a
// [][]byte.
//
// TODO(ffranr): Reconcile this function with asset.TxWitnessDecoder.
func DeserializeWitnessStack(serialized []byte) ([][]byte, error) {
var (
// buf is a general scratch buffer used when reading.
buf [8]byte

stack [][]byte
)
reader := bytes.NewReader(serialized)

// Read the number of witness elements (compact size integer)
count, err := tlv.ReadVarInt(reader, &buf)
if err != nil {
return nil, fmt.Errorf("failed to read witness count: %w", err)
}

// Read each witness element
for i := uint64(0); i < count; i++ {
elementSize, err := tlv.ReadVarInt(reader, &buf)
if err != nil {
return nil, fmt.Errorf("failed to read witness "+
"element size: %w", err)
}

// Read the witness element data
element := make([]byte, elementSize)
if _, err := reader.Read(element); err != nil {
return nil, fmt.Errorf("failed to read witness "+
"element data: %w", err)
}
stack = append(stack, element)
}

return stack, nil
}

// SyncUniverses syncs the universes of two tapd instances and waits until they
// are in sync.
func SyncUniverses(ctx context.Context, t *testing.T, clientTapd,
Expand Down
21 changes: 20 additions & 1 deletion rpcserver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -780,6 +780,7 @@ func (r *rpcServer) FundBatch(ctx context.Context,
func (r *rpcServer) SealBatch(ctx context.Context,
req *mintrpc.SealBatchRequest) (*mintrpc.SealBatchResponse, error) {

// Unmarshal group witnesses from the request.
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So the idea is that the old way and new way could even be mixed? Since both seem to be parsed and then merged (at least with a collision check, so nothing is overwritten).

Not sure if that's more confusing to the user rather than helpful? I think just from an API perspective it makes sense to keep the old way (as that's perhaps easier to use programmatically). But perhaps we should disallow using both at the same time, to avoid some confusion?

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the old way still works for me with this branch, but as mentioned above, the new way fails

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Did you switch between branches? Or use my Ledger branch before I rebased it on top of this one?
Not being able to parse the PSBT probably means it's because of the bump in the psbt library that isn't in this branch. So can you try again with the current version of #1301 that includes this PR?

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Still getting unable to parse signed group virtual PSBT: unexpected EOF with cold-group-key-pedersen. I'm using chantools to generate the PSBT, by the way. Maybe I'm not supposed to use that?

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Hmm, weird. Can you paste the PSBT here please?

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You can give it a try here: https://github.com/lightninglabs/tapdvalidation/tree/sealbatch-signed-group-psbt-test . Follow README.md, except you'll have to add an extra step to checkout this branch before you run ./start_mini_META.

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You can see here the difference between the old way that worked and the new way that doesn't work: https://github.com/lightninglabs/tapdvalidation/commit/e95ee5b432443570632cc36202c14fb902b4cc9a.

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@ZZiigguurraatt ZZiigguurraatt Jan 18, 2025 •
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Okay, I figured out my issue. It has been fixed here: https://github.com/lightninglabs/tapdvalidation/commit/2aa7f2f05eb43c7f3e11eb1381759f240057c231 . The problem is I passed a string as signed_group_virtual_psbts instead of an array of strings.

Can we get a more useful test and error message for this mistake? unable to parse signed group virtual PSBT: unexpected EOF is super uninformative. I'm a little confused why gRPC accepts a single string instead of require an array for "repeated" fields. I'm not sure why it doesn't enforce this, but I've made this mistake before and the error messages never actually lead me to understand the mistake in a meaningful way.

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SealBatchRequest in mintrpc is given as

type SealBatchRequest struct {
    state                   protoimpl.MessageState
    sizeCache               protoimpl.SizeCache
    unknownFields           protoimpl.UnknownFields
    ShortResponse           bool                   `protobuf:"varint,1,opt,name=short_response,json=shortResponse,proto3" json:"short_response,omitempty"`
    GroupWitnesses          []*taprpc.GroupWitness `protobuf:"bytes,2,rep,name=group_witnesses,json=groupWitnesses,proto3" json:"group_witnesses,omitempty"`
    SignedGroupVirtualPsbts []string               `protobuf:"bytes,3,rep,name=signed_group_virtual_psbts,json=signedGroupVirtualPsbts,proto3" json:"signed_group_virtual_psbts,omitempty"`
}

Are you using JSON and Python? I think in golang the type checker would have caught this.

unable to parse signed group virtual PSBT: unexpected EOF is super uninformative

I'll modify the error message to include the signed PSBT as seen by tapd.

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Using Python.

It seems to do more clear error messages if I mix up a string , bytes, or int, but for some reason does not check arrays very well.

var groupWitnesses []asset.PendingGroupWitness
for i := range req.GroupWitnesses {
wit, err := taprpc.UnmarshalGroupWitness(req.GroupWitnesses[i])
Expand All @@ -790,9 +791,27 @@ func (r *rpcServer) SealBatch(ctx context.Context,
groupWitnesses = append(groupWitnesses, *wit)
}

// Unmarshal signed group virtual PSBTs from the request.
var groupPSBTs []psbt.Packet
for i := range req.SignedGroupVirtualPsbts {
groupPsbt := req.SignedGroupVirtualPsbts[i]

// Decode the signed group virtual PSBT.
r := bytes.NewReader([]byte(groupPsbt))
psbtPacket, err := psbt.NewFromRawBytes(r, true)
if err != nil {
return nil, fmt.Errorf("unable to parse signed "+
"group virtual PSBT (signed_psbt=%s): %w",
groupPsbt, err)
}

groupPSBTs = append(groupPSBTs, *psbtPacket)
}

batch, err := r.cfg.AssetMinter.SealBatch(
tapgarden.SealParams{
GroupWitnesses: groupWitnesses,
GroupWitnesses: groupWitnesses,
SignedGroupVirtualPsbts: groupPSBTs,
},
)
if err != nil {
Expand Down
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