proof: add magic bytes to individual proofs and proof files

cmd/tapcli/proofs.go

@@ -75,7 +75,7 @@ func verifyProof(ctx *cli.Context) error {
 	defer cleanUp()
 
 	resp, err := client.VerifyProof(ctxc, &taprpc.ProofFile{
-		RawProof: rawFile,
+		RawProofFile: rawFile,
 	})
 	if err != nil {
 		return fmt.Errorf("unable to verify proof file: %w", err)
@@ -273,7 +273,7 @@ func exportProof(ctx *cli.Context) error {
 	// JSON format.
 	if ctx.String(proofPathName) != "" {
 		filePath := lncfg.CleanAndExpandPath(ctx.String(proofPathName))
-		return writeToFile(filePath, resp.RawProof)
+		return writeToFile(filePath, resp.RawProofFile)
 	}
 
 	printRespJSON(resp)

itest/addrs_test.go

@@ -296,10 +296,10 @@ func sendProof(t *harnessTest, src, dst *tapdHarness, scriptKey []byte,
 	}, defaultWaitTimeout)
 	require.NoError(t.t, waitErr)
 
-	t.Logf("Importing proof %x", proofResp.RawProof)
+	t.Logf("Importing proof %x", proofResp.RawProofFile)
 
 	importResp, err := dst.ImportProof(ctxb, &tapdevrpc.ImportProofRequest{
-		ProofFile:    proofResp.RawProof,
+		ProofFile:    proofResp.RawProofFile,
 		GenesisPoint: genInfo.GenesisPoint,
 	})
 	require.NoError(t.t, err)

itest/assertions.go

@@ -225,7 +225,7 @@ func WaitForProofUpdate(t *testing.T, client taprpc.TaprootAssetsClient,
 
 		f := &proof.File{}
 		require.NoError(
-			t, f.Decode(bytes.NewReader(exportResp.RawProof)),
+			t, f.Decode(bytes.NewReader(exportResp.RawProofFile)),
 		)
 		lastProof, err := f.LastProof()
 		require.NoError(t, err)
@@ -255,7 +255,7 @@ func AssertAssetProofs(t *testing.T, tapClient taprpc.TaprootAssetsClient,
 	require.NoError(t, err)
 
 	file, snapshot := verifyProofBlob(
-		t, tapClient, chainClient, a, exportResp.RawProof,
+		t, tapClient, chainClient, a, exportResp.RawProofFile,
 	)
 
 	assetJSON, err := formatProtoJSON(a)
@@ -268,7 +268,7 @@ func AssertAssetProofs(t *testing.T, tapClient taprpc.TaprootAssetsClient,
 		t, CommitmentKey(t, a), snapshot.Asset.AssetCommitmentKey(),
 	)
 
-	return exportResp.RawProof
+	return exportResp.RawProofFile
 }
 
 // assertAssetProofsInvalid makes sure the proofs for the given asset can be
@@ -289,11 +289,11 @@ func assertAssetProofsInvalid(t *testing.T, tapd *tapdHarness,
 	require.NoError(t, err)
 
 	f := &proof.File{}
-	require.NoError(t, f.Decode(bytes.NewReader(exportResp.RawProof)))
+	require.NoError(t, f.Decode(bytes.NewReader(exportResp.RawProofFile)))
 
 	// Also make sure that the RPC can verify the proof as well.
 	verifyResp, err := tapd.VerifyProof(ctxt, &taprpc.ProofFile{
-		RawProof: exportResp.RawProof,
+		RawProofFile: exportResp.RawProofFile,
 	})
 	require.NoError(t, err)
 	require.False(t, verifyResp.Valid)
@@ -314,7 +314,7 @@ func verifyProofBlob(t *testing.T, tapClient taprpc.TaprootAssetsClient,
 
 	// Also make sure that the RPC can verify the proof as well.
 	verifyResp, err := tapClient.VerifyProof(ctxt, &taprpc.ProofFile{
-		RawProof: blob,
+		RawProofFile: blob,
 	})
 	require.NoError(t, err)
 	require.True(t, verifyResp.Valid)

itest/send_test.go

@@ -861,11 +861,11 @@ func addProofTestVectorFromFile(t *testing.T, testName string,
 	require.NoError(t, waitErr)
 
 	if binaryFileName != "" {
-		test.WriteTestFileHex(t, binaryFileName, proofResp.RawProof)
+		test.WriteTestFileHex(t, binaryFileName, proofResp.RawProofFile)
 	}
 
 	var f proof.File
-	err := f.Decode(bytes.NewReader(proofResp.RawProof))
+	err := f.Decode(bytes.NewReader(proofResp.RawProofFile))
 	require.NoError(t, err)
 
 	if f.NumProofs() <= fileIndex {

proof/file.go

@@ -97,7 +97,15 @@ func NewFile(v Version, proofs ...Proof) (*File, error) {
 
 // Encode encodes the proof file into `w` including its checksum.
 func (f *File) Encode(w io.Writer) error {
-	err := binary.Write(w, binary.BigEndian, uint32(f.Version))
+	num, err := w.Write(FilePrefixMagicBytes[:])
+	if err != nil {
+		return err
+	}
+	if num != PrefixMagicBytesLength {
+		return errors.New("failed to write prefix magic bytes")
+	}
+
+	err = binary.Write(w, binary.BigEndian, uint32(f.Version))
 	if err != nil {
 		return err
 	}
@@ -137,6 +145,21 @@ func (f *File) Encode(w io.Writer) error {
 
 // Decode decodes a proof file from `r`.
 func (f *File) Decode(r io.Reader) error {
+	var prefixMagicBytes [PrefixMagicBytesLength]byte
+	num, err := r.Read(prefixMagicBytes[:])
+	if err != nil {
+		return err
+	}
+	if num != PrefixMagicBytesLength {
+		return errors.New("failed to read prefix magic bytes")
+	}
+
+	if prefixMagicBytes != FilePrefixMagicBytes {
+		return fmt.Errorf("invalid prefix magic bytes, expected %s, "+
+			"got %s", string(FilePrefixMagicBytes[:]),
+			string(prefixMagicBytes[:]))
+	}
+
 	var version uint32
 	if err := binary.Read(r, binary.BigEndian, &version); err != nil {
 		return err

proof/proof.go

@@ -1,7 +1,9 @@
 package proof
 
 import (
+	"bytes"
 	"errors"
+	"fmt"
 	"io"
 
 	"github.com/btcsuite/btcd/wire"
@@ -58,6 +60,48 @@ var (
 	RegtestOwnershipProofName = "ownership-proof.hex"
 )
 
+const (
+	// PrefixMagicBytesLength is the length of the magic bytes that are
+	// prefixed to individual proofs or proof files.
+	PrefixMagicBytesLength = 4
+)
+
+var (
+	// PrefixMagicBytes are the magic bytes that are prefixed to an
+	// individual transition or mint proof when encoding it. This is the
+	// ASCII encoding of the string "TAPP" (Taproot Assets Protocol Proof)
+	// in hex.
+	PrefixMagicBytes = [PrefixMagicBytesLength]byte{0x54, 0x41, 0x50, 0x50}
+
+	// FilePrefixMagicBytes are the magic bytes that are prefixed to a proof
+	// file when encoding it. This is the ASCII encoding of the string
+	// "TAPF" (Taproot Assets Protocol File) in hex.
+	FilePrefixMagicBytes = [PrefixMagicBytesLength]byte{
+		0x54, 0x41, 0x50, 0x46,
+	}
+)
+
+// IsSingleProof returns true if the given blob is an encoded individual
+// mint/transition proof.
+func IsSingleProof(blob Blob) bool {
+	if len(blob) < PrefixMagicBytesLength {
+		return false
+	}
+
+	return bytes.Equal(blob[:PrefixMagicBytesLength], PrefixMagicBytes[:])
+}
+
+// IsProofFile returns true if the given blob is an encoded proof file.
+func IsProofFile(blob Blob) bool {
+	if len(blob) < PrefixMagicBytesLength {
+		return false
+	}
+
+	return bytes.Equal(
+		blob[:PrefixMagicBytesLength], FilePrefixMagicBytes[:],
+	)
+}
+
 // UpdateCallback is a callback that is called when proofs are updated because
 // of a re-org.
 type UpdateCallback func([]*Proof) error
@@ -212,6 +256,14 @@ func (p *Proof) DecodeRecords() []tlv.Record {
 
 // Encode encodes a Proof into `w`.
 func (p *Proof) Encode(w io.Writer) error {
+	num, err := w.Write(PrefixMagicBytes[:])
+	if err != nil {
+		return err
+	}
+	if num != PrefixMagicBytesLength {
+		return errors.New("failed to write prefix magic bytes")
+	}
+
 	stream, err := tlv.NewStream(p.EncodeRecords()...)
 	if err != nil {
 		return err
@@ -221,6 +273,21 @@ func (p *Proof) Encode(w io.Writer) error {
 
 // Decode decodes a Proof from `r`.
 func (p *Proof) Decode(r io.Reader) error {
+	var prefixMagicBytes [PrefixMagicBytesLength]byte
+	num, err := r.Read(prefixMagicBytes[:])
+	if err != nil {
+		return err
+	}
+	if num != PrefixMagicBytesLength {
+		return errors.New("failed to read prefix magic bytes")
+	}
+
+	if prefixMagicBytes != PrefixMagicBytes {
+		return fmt.Errorf("invalid prefix magic bytes, expected %s, "+
+			"got %s", string(PrefixMagicBytes[:]),
+			string(prefixMagicBytes[:]))
+	}
+
 	stream, err := tlv.NewStream(p.DecodeRecords()...)
 	if err != nil {
 		return err

proof/proof_test.go

@@ -246,12 +246,38 @@ func TestProofEncoding(t *testing.T) {
 	require.NoError(t, err)
 	proof.AdditionalInputs = []File{*file, *file}
 
-	var buf bytes.Buffer
-	require.NoError(t, proof.Encode(&buf))
+	var proofBuf bytes.Buffer
+	require.NoError(t, proof.Encode(&proofBuf))
+	proofBytes := proofBuf.Bytes()
+
 	var decodedProof Proof
-	require.NoError(t, decodedProof.Decode(&buf))
+	require.NoError(t, decodedProof.Decode(bytes.NewReader(proofBytes)))
 
 	assertEqualProof(t, &proof, &decodedProof)
+
+	// Make sure the proof and proof file prefixes are checked correctly.
+	var fileBuf bytes.Buffer
+	require.NoError(t, file.Encode(&fileBuf))
+	fileBytes := fileBuf.Bytes()
+
+	p := &Proof{}
+	err = p.Decode(bytes.NewReader(fileBytes))
+	require.ErrorContains(
+		t, err, "invalid prefix magic bytes, expected TAPP",
+	)
+
+	f := &File{}
+	err = f.Decode(bytes.NewReader(proofBytes))
+	require.ErrorContains(
+		t, err, "invalid prefix magic bytes, expected TAPF",
+	)
+
+	require.True(t, IsSingleProof(proofBytes))
+	require.True(t, IsProofFile(fileBytes))
+	require.False(t, IsProofFile(proofBytes))
+	require.False(t, IsSingleProof(fileBytes))
+	require.False(t, IsProofFile(nil))
+	require.False(t, IsSingleProof(nil))
 }
 
 func genRandomGenesisWithProof(t testing.TB, assetType asset.Type,

proof/testdata/ownership-proof.hex

@@ -1 +1 @@
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