proof: add code for stitching together failed proof suffixes

proof/proof_stitching_test.go

@@ -0,0 +1,186 @@
+package proof
+
+import (
+	"bytes"
+	"context"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/btcsuite/btcd/rpcclient"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightninglabs/taproot-assets/commitment"
+	"github.com/stretchr/testify/require"
+)
+
+// TestProofStitching is a manual test that can be used to stitch together
+// proofs of a failed transfer. It reads a template proof from a file and then
+// reads a series of suffix proofs that are supposed to be stitched to the
+// template. The suffix proofs are then enhanced with the on-chain information
+// and written out to new files as full provenance proof files.
+func TestProofStitching(t *testing.T) {
+	// This code makes a lot of assumptions on what files need to be present
+	// and is really only meant for manual use to stitch together the proofs
+	// of a failed transfer. Comment out the t.Skip line to run it.
+	t.Skip("Code only for manual use.")
+
+	const (
+		rpcUser     = "lightning"
+		rpcPassword = "lightning"
+		rpcHost     = "localhost:8332"
+		startIndex  = 0
+		endIndex    = 12
+		mindedBlock = 868229
+	)
+
+	client, err := bitcoinClient(rpcHost, rpcUser, rpcPassword)
+	require.NoError(t, err)
+
+	verifier := &bitcoindVerifier{client: client}
+
+	tplBytes, err := os.ReadFile(filepath.Join(
+		testDataFileName, "template.proof",
+	))
+	require.NoError(t, err)
+
+	f := &File{}
+	err = f.Decode(bytes.NewReader(tplBytes))
+	require.NoError(t, err)
+
+	// We want the template to valid, otherwise all other steps are
+	// meaningless.
+	_, err = f.Verify(
+		context.Background(), verifier.VerifyHeader, MockMerkleVerifier,
+		MockGroupVerifier, MockChainLookup,
+	)
+	require.NoError(t, err)
+
+	// The template proof is the last proof in the file, that was the only
+	// one fully written. We take the last proof to find out the on-chain
+	// TX that was involved in the transfer.
+	tplProof, err := f.LastProof()
+	require.NoError(t, err)
+
+	// Fetch the transaction to make sure it is actually known.
+	txid := tplProof.AnchorTx.TxHash()
+	_, err = client.GetRawTransaction(&txid)
+	require.NoError(t, err)
+
+	// Now fetch the full block the TX was mined in.
+	blockHash, err := client.GetBlockHash(int64(mindedBlock))
+	require.NoError(t, err)
+	block, err := client.GetBlock(blockHash)
+	require.NoError(t, err)
+
+	// What's the transaction's index in the block?
+	txIndex := -1
+	for i, tx := range block.Transactions {
+		if tx.TxHash() == txid {
+			txIndex = i
+			break
+		}
+	}
+	require.NotEqual(t, -1, txIndex)
+
+	// And with that, we can create the merkle proof for the transaction.
+	merkleProof, err := NewTxMerkleProof(block.Transactions, txIndex)
+	require.NoError(t, err)
+
+	for i := startIndex; i <= endIndex; i++ {
+		brokenProofHex, err := os.ReadFile(filepath.Join(
+			testDataFileName, fmt.Sprintf("suffix-%d.hex", i),
+		))
+		require.NoError(t, err)
+
+		brokenProofBytes, err := hex.DecodeString(
+			strings.TrimSpace(string(brokenProofHex)),
+		)
+		require.NoError(t, err)
+
+		brokenProof := &Proof{}
+		err = brokenProof.Decode(bytes.NewReader(brokenProofBytes))
+		require.NoError(t, err)
+
+		// We can now fill in the block information for the broken
+		// proof.
+		brokenProof.TxMerkleProof = *merkleProof
+		brokenProof.BlockHeight = mindedBlock
+		brokenProof.BlockHeader = block.Header
+
+		// We now should have a fully valid proof that we can write out
+		// to a file, by replacing the last one in the template.
+		err = f.ReplaceLastProof(*brokenProof)
+		require.NoError(t, err)
+
+		// We now need to find out if this is one of the proofs that
+		// can't be fixed because of the script key usage. So if we
+		// get an "invalid exclusion proof" error when validating, we
+		// need to skip this proof.
+		_, err = f.Verify(
+			context.Background(), verifier.VerifyHeader,
+			DefaultMerkleVerifier, MockGroupVerifier,
+			MockChainLookup,
+		)
+		switch {
+		case errors.Is(err, commitment.ErrInvalidTaprootProof):
+			t.Logf("Proof %d is invalid and can't be rescued: %v",
+				i, err)
+
+			continue
+
+		case err != nil:
+			require.NoError(t, err)
+		}
+
+		// If the proof is valid, we can write it out to a file.
+		outFile, err := os.Create(filepath.Join(
+			testDataFileName, fmt.Sprintf("fixed-%d.proof", i),
+		))
+		require.NoError(t, err)
+
+		err = f.Encode(outFile)
+		require.NoError(t, err)
+
+		err = outFile.Close()
+		require.NoError(t, err)
+	}
+}
+
+func bitcoinClient(rpcHost, rpcUser,
+	rpcPass string) (*rpcclient.Client, error) {
+
+	rpcCfg := rpcclient.ConnConfig{
+		Host:                 rpcHost,
+		User:                 rpcUser,
+		Pass:                 rpcPass,
+		DisableConnectOnNew:  true,
+		DisableAutoReconnect: false,
+		DisableTLS:           true,
+		HTTPPostMode:         true,
+	}
+
+	return rpcclient.New(&rpcCfg, nil)
+}
+
+type bitcoindVerifier struct {
+	client *rpcclient.Client
+}
+
+func (b *bitcoindVerifier) VerifyHeader(header wire.BlockHeader,
+	height uint32) error {
+
+	targetHash, err := b.client.GetBlockHash(int64(height))
+	if err != nil {
+		return fmt.Errorf("unable to get block hash: %w", err)
+	}
+
+	if *targetHash != header.BlockHash() {
+		return fmt.Errorf("block hash mismatch")
+	}
+
+	return nil
+}