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202
LICENSE
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@@ -1,202 +0,0 @@
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20
README.md
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@@ -1,23 +1,7 @@
# opentimestamps # opentimestamps
Go port of https://github.com/opentimestamps/python-opentimestamps. Interact with calendar servers, create and verify OTS attestations.
Copied from https://github.com/BlockchainSource/go-opentimestamps.
# Done
* Byte-level serialization format
* Timestamp parsing
* Creating pending timestamps
* Upgrading pending timestamps
* Bitcoin Timestamp verification
# To do
* Support for multiple timestamp servers
* Proper timestamp merging (on upgrade)
* More conformant serialization (sorting)
# License # License
Apache 2.0 Public Domain

180
attestations.go
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package opentimestamps
import (
"bytes"
"fmt"
)
const (
attestationTagSize = 8
attestationMaxPayloadSize = 8192
pendingAttestationMaxUriLength = 1000
)
var (
bitcoinAttestationTag = mustDecodeHex("0588960d73d71901")
pendingAttestationTag = mustDecodeHex("83dfe30d2ef90c8e")
)
type Attestation interface {
tag() []byte
decode(*deserializationContext) (Attestation, error)
encode(*serializationContext) error
}
type baseAttestation struct {
fixedTag []byte
}
func (b *baseAttestation) tag() []byte {
return b.fixedTag
}
type pendingAttestation struct {
baseAttestation
uri string
}
func newPendingAttestation() *pendingAttestation {
return &pendingAttestation{
baseAttestation: baseAttestation{
fixedTag: pendingAttestationTag,
},
}
}
func (p *pendingAttestation) decode(
ctx *deserializationContext,
) (Attestation, error) {
uri, err := ctx.readVarBytes(0, pendingAttestationMaxUriLength)
if err != nil {
return nil, err
}
// TODO utf8 checks
ret := *p
ret.uri = string(uri)
return &ret, nil
}
func (p *pendingAttestation) encode(ctx *serializationContext) error {
return ctx.writeVarBytes([]byte(p.uri))
}
func (p *pendingAttestation) String() string {
return fmt.Sprintf("VERIFY PendingAttestation(url=%s)", p.uri)
}
type BitcoinAttestation struct {
baseAttestation
Height uint64
}
func newBitcoinAttestation() *BitcoinAttestation {
return &BitcoinAttestation{
baseAttestation: baseAttestation{bitcoinAttestationTag},
}
}
func (b *BitcoinAttestation) String() string {
return fmt.Sprintf("VERIFY BitcoinAttestation(height=%d)", b.Height)
}
func (b *BitcoinAttestation) decode(
ctx *deserializationContext,
) (Attestation, error) {
height, err := ctx.readVarUint()
if err != nil {
return nil, err
}
ret := *b
ret.Height = height
return &ret, nil
}
func (b *BitcoinAttestation) encode(ctx *serializationContext) error {
return ctx.writeVarUint(uint64(b.Height))
}
const hashMerkleRootSize = 32
func (b *BitcoinAttestation) VerifyAgainstBlockHash(digest, blockHash []byte) error {
if len(digest) != hashMerkleRootSize {
return fmt.Errorf("invalid digest size %d", len(digest))
}
if !bytes.Equal(digest, blockHash) {
return fmt.Errorf(
"hash mismatch digest=%x blockHash=%x",
digest, blockHash,
)
}
return nil
}
// This is a catch-all for when we don't know how to parse it
type unknownAttestation struct {
tagBytes []byte
bytes []byte
}
func (u unknownAttestation) tag() []byte {
return u.tagBytes
}
func (unknownAttestation) decode(*deserializationContext) (Attestation, error) {
panic("not implemented")
}
func (unknownAttestation) encode(*serializationContext) error {
panic("not implemented")
}
func (u unknownAttestation) String() string {
return fmt.Sprintf("UnknownAttestation(bytes=%q)", u.bytes)
}
var attestations []Attestation = []Attestation{
newPendingAttestation(),
newBitcoinAttestation(),
}
func encodeAttestation(ctx *serializationContext, att Attestation) error {
if err := ctx.writeBytes(att.tag()); err != nil {
return err
}
buf := &bytes.Buffer{}
if err := att.encode(&serializationContext{buf}); err != nil {
return err
}
return ctx.writeVarBytes(buf.Bytes())
}
func ParseAttestation(ctx *deserializationContext) (Attestation, error) {
tag, err := ctx.readBytes(attestationTagSize)
if err != nil {
return nil, err
}
attBytes, err := ctx.readVarBytes(
0, attestationMaxPayloadSize,
)
if err != nil {
return nil, err
}
attCtx := newDeserializationContext(
bytes.NewBuffer(attBytes),
)
for _, a := range attestations {
if bytes.Equal(tag, a.tag()) {
att, err := a.decode(attCtx)
if err != nil {
return nil, err
}
if !attCtx.assertEOF() {
return nil, fmt.Errorf("expected EOF in attCtx")
}
return att, nil
}
}
return unknownAttestation{tag, attBytes}, nil
}

158
operations.go
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@@ -1,158 +0,0 @@
package opentimestamps
import (
"crypto/sha256"
"encoding/hex"
"fmt"
)
const maxResultLength = 4096
type (
unaryMsgOp func(message []byte) ([]byte, error)
binaryMsgOp func(message, argument []byte) ([]byte, error)
)
// msgAppend returns the concatenation of msg and arg
func msgAppend(msg, arg []byte) (res []byte, err error) {
res = append(res, msg...)
res = append(res, arg...)
return
}
// msgPrepend returns the concatenation of arg and msg
func msgPrepend(msg, arg []byte) (res []byte, err error) {
res = append(res, arg...)
res = append(res, msg...)
return
}
// msgReverse returns the reversed msg. Deprecated.
func msgReverse(msg []byte) ([]byte, error) {
if len(msg) == 0 {
return nil, fmt.Errorf("empty input invalid for msgReverse")
}
res := make([]byte, len(msg))
for i, b := range msg {
res[len(res)-i-1] = b
}
return res, nil
}
func msgHexlify(msg []byte) ([]byte, error) {
if len(msg) == 0 {
return nil, fmt.Errorf("empty input invalid for msgHexlify")
}
return []byte(hex.EncodeToString(msg)), nil
}
type opCode interface {
match(byte) bool
decode(*deserializationContext) (opCode, error)
encode(*serializationContext) error
apply(message []byte) ([]byte, error)
}
type op struct {
tag byte
name string
}
func (o op) match(tag byte) bool {
return o.tag == tag
}
type unaryOp struct {
op
msgOp unaryMsgOp
}
func newUnaryOp(tag byte, name string, msgOp unaryMsgOp) *unaryOp {
return &unaryOp{op{tag: tag, name: name}, msgOp}
}
func (u *unaryOp) String() string {
return u.name
}
func (u *unaryOp) decode(ctx *deserializationContext) (opCode, error) {
ret := *u
return &ret, nil
}
func (u *unaryOp) encode(ctx *serializationContext) error {
return ctx.writeByte(u.tag)
}
func (u *unaryOp) apply(message []byte) ([]byte, error) {
return u.msgOp(message)
}
// Binary operations
// We decode an extra varbyte argument and use it in apply()
type binaryOp struct {
op
msgOp binaryMsgOp
argument []byte
}
func newBinaryOp(tag byte, name string, msgOp binaryMsgOp) *binaryOp {
return &binaryOp{
op: op{tag: tag, name: name},
msgOp: msgOp,
argument: nil,
}
}
func (b *binaryOp) decode(ctx *deserializationContext) (opCode, error) {
arg, err := ctx.readVarBytes(0, maxResultLength)
if err != nil {
return nil, err
}
if len(arg) == 0 {
return nil, fmt.Errorf("empty argument invalid for binaryOp")
}
ret := *b
ret.argument = arg
return &ret, nil
}
func (b *binaryOp) encode(ctx *serializationContext) error {
if err := ctx.writeByte(b.tag); err != nil {
return err
}
return ctx.writeVarBytes(b.argument)
}
func (b *binaryOp) apply(message []byte) ([]byte, error) {
return b.msgOp(message, b.argument)
}
func (b *binaryOp) String() string {
return fmt.Sprintf("%s %x", b.name, b.argument)
}
func msgSHA256(msg []byte) ([]byte, error) {
res := sha256.Sum256(msg)
return res[:], nil
}
var (
opAppend = newBinaryOp(0xf0, "APPEND", msgAppend)
opPrepend = newBinaryOp(0xf1, "PREPEND", msgPrepend)
opReverse = newUnaryOp(0xf2, "REVERSE", msgReverse)
opHexlify = newUnaryOp(0xf3, "HEXLIFY", msgHexlify)
opSHA256 = newUnaryOp(0x08, "SHA256", msgSHA256)
)
var opCodes []opCode = []opCode{opAppend, opPrepend, opReverse, opHexlify, opSHA256}
func parseOp(ctx *deserializationContext, tag byte) (opCode, error) {
for _, op := range opCodes {
if op.match(tag) {
return op.decode(ctx)
}
}
return nil, fmt.Errorf("could not decode tag %02x", tag)
}

146
remote_calendar.go
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@@ -1,146 +0,0 @@
package opentimestamps
import (
"bytes"
"encoding/hex"
"fmt"
"io"
"net/http"
"net/http/httputil"
"strings"
"github.com/sirupsen/logrus"
)
const userAgent = "go-opentimestamps"
const dumpResponse = false
type RemoteCalendar struct {
baseURL string
client *http.Client
log *logrus.Logger
}
func NewRemoteCalendar(baseURL string) (*RemoteCalendar, error) {
// FIXME remove this
if baseURL == "localhost" {
baseURL = "http://localhost:14788"
}
// TODO validate url
if !strings.HasSuffix(baseURL, "/") {
baseURL += "/"
}
return &RemoteCalendar{
baseURL,
http.DefaultClient,
logrus.New(),
}, nil
}
// Check response status, return informational error message if
// status is not `200 OK`.
func checkStatusOK(resp *http.Response) error {
if resp.StatusCode == http.StatusOK {
return nil
}
errMsg := fmt.Sprintf("unexpected response: %q", resp.Status)
if resp.Body == nil {
return fmt.Errorf("%s (body=nil)", errMsg)
}
defer resp.Body.Close()
bodyBytes, err := io.ReadAll(resp.Body)
if err != nil {
return fmt.Errorf("%s (bodyErr=%v)", errMsg, err)
} else {
return fmt.Errorf("%s (body=%q)", errMsg, bodyBytes)
}
}
func (c *RemoteCalendar) do(r *http.Request) (*http.Response, error) {
r.Header.Add("Accept", "application/vnd.opentimestamps.v1")
r.Header.Add("User-Agent", userAgent)
c.log.Debugf("> %s %s", r.Method, r.URL)
resp, err := c.client.Do(r)
if err != nil {
c.log.Errorf("> %s %s error: %v", r.Method, r.URL, err)
return resp, err
}
c.log.Debugf("< %s %s - %v", r.Method, r.URL, resp.Status)
if dumpResponse {
bytes, err := httputil.DumpResponse(resp, true)
if err == nil {
c.log.Debugf("response dump:%s ", bytes)
}
}
return resp, err
}
func (c *RemoteCalendar) url(path string) string {
return c.baseURL + path
}
func (c *RemoteCalendar) Submit(digest [32]byte) (*Timestamp, error) {
body := bytes.NewBuffer(digest[:])
req, err := http.NewRequest("POST", c.url("digest"), body)
if err != nil {
return nil, err
}
resp, err := c.do(req)
if err != nil {
return nil, err
}
if resp.Body != nil {
defer resp.Body.Close()
}
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("expected 200, got %v", resp.Status)
}
return NewTimestampFromReader(resp.Body, digest[:])
}
func (c *RemoteCalendar) GetTimestamp(commitment []byte) (*Timestamp, error) {
url := c.url("timestamp/" + hex.EncodeToString(commitment))
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return nil, err
}
resp, err := c.do(req)
if err != nil {
return nil, err
}
if err := checkStatusOK(resp); err != nil {
return nil, err
}
if resp.Body != nil {
defer resp.Body.Close()
}
return NewTimestampFromReader(resp.Body, commitment)
}
type PendingTimestamp struct {
Timestamp *Timestamp
PendingAttestation *pendingAttestation
}
func (p PendingTimestamp) Upgrade() (*Timestamp, error) {
cal, err := NewRemoteCalendar(p.PendingAttestation.uri)
if err != nil {
return nil, err
}
return cal.GetTimestamp(p.Timestamp.Message)
}
func PendingTimestamps(ts *Timestamp) (res []PendingTimestamp) {
ts.Walk(func(ts *Timestamp) {
for _, att := range ts.Attestations {
p, ok := att.(*pendingAttestation)
if !ok {
continue
}
attCopy := *p
res = append(res, PendingTimestamp{ts, &attCopy})
}
})
return
}

70
remote_calendar_test.go
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@@ -1,70 +0,0 @@
package opentimestamps
import (
"crypto/sha256"
"fmt"
"os"
"testing"
"time"
"github.com/sirupsen/logrus"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)
const (
calendarServerEnvvar = "GOTS_TEST_CALENDAR_SERVER"
bitcoinRegtestEnvvar = "GOTS_TEST_BITCOIN_REGTEST_SERVER"
)
func newTestCalendar(url string) *RemoteCalendar {
logrus.SetLevel(logrus.DebugLevel)
cal, err := NewRemoteCalendar(url)
if err != nil {
panic("could not create test calendar")
}
cal.log.Level = logrus.DebugLevel
return cal
}
func newTestDigest(in string) [32]byte {
return sha256.Sum256([]byte(in))
}
func TestRemoteCalendarExample(t *testing.T) {
dts, err := NewDetachedTimestampFromPath(
"./examples/two-calendars.txt.ots",
)
require.NoError(t, err)
pts := PendingTimestamps(dts.Timestamp)
assert.Equal(t, 2, len(pts))
for _, pt := range pts {
ts, err := pt.Upgrade()
assert.NoError(t, err)
fmt.Print(ts.Dump())
}
}
func TestRemoteCalendarRoundTrip(t *testing.T) {
calendarServer := os.Getenv(calendarServerEnvvar)
if calendarServer == "" {
t.Skipf("%q not set, skipping test", calendarServerEnvvar)
}
cal := newTestCalendar(calendarServer)
ts, err := cal.Submit(newTestDigest("Hello, World!"))
require.NoError(t, err)
require.NotNil(t, ts)
// TODO call rpcclient generateblock 100
// FIXME possible opentimestamps-server bug?
// wait until attestation has been aggregated
time.Sleep(2 * time.Second)
for _, pts := range PendingTimestamps(ts) {
ts, err := pts.Upgrade()
assert.NoError(t, err)
_ = ts
}
}

206
serialize.go
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@@ -1,206 +0,0 @@
package opentimestamps
import (
"bufio"
"bytes"
"fmt"
"io"
"math"
)
// serializationContext helps encoding values in the ots format
type serializationContext struct {
w io.Writer
}
// newSerializationContext returns a serializationContext for a writer
func newSerializationContext(w io.Writer) *serializationContext {
return &serializationContext{w}
}
// writeBytes writes the raw bytes to the underlying writer
func (s serializationContext) writeBytes(b []byte) error {
// number of bytes can be ignored
// if it is equal len(b) then err is nil
_, err := s.w.Write(b)
if err != nil {
return err
}
return nil
}
// writeByte writes a single byte
func (s serializationContext) writeByte(b byte) error {
return s.writeBytes([]byte{b})
}
// writeBool encodes and writes a boolean value
func (s serializationContext) writeBool(b bool) error {
if b {
return s.writeByte(0xff)
} else {
return s.writeByte(0x00)
}
}
// writeVarUint encodes and writes writes a variable-length integer
func (s serializationContext) writeVarUint(v uint64) error {
if v == 0 {
s.writeByte(0x00)
}
for v > 0 {
b := byte(v & 0x7f)
if v > uint64(0x7f) {
b |= 0x80
}
if err := s.writeByte(b); err != nil {
return err
}
if v <= 0x7f {
break
}
v >>= 7
}
return nil
}
// writeVarBytes encodes and writes a variable-length array
func (s serializationContext) writeVarBytes(arr []byte) error {
if err := s.writeVarUint(uint64(len(arr))); err != nil {
return err
}
return s.writeBytes(arr)
}
// deserializationContext helps decoding values from the ots format
type deserializationContext struct {
r io.Reader
}
// safety boundary for readBytes
// allocation limit for arrays
const maxReadSize = (1 << 12)
func (d deserializationContext) dump() string {
arr, _ := d.r.(*bufio.Reader).Peek(512)
return fmt.Sprintf("% x", arr)
}
// readBytes reads n bytes.
func (d deserializationContext) readBytes(n int) ([]byte, error) {
if n > maxReadSize {
return nil, fmt.Errorf("over maxReadSize: %d", maxReadSize)
}
b := make([]byte, n)
m, err := d.r.Read(b)
if err != nil {
return b, err
}
if n != m {
return b, fmt.Errorf("expected %d bytes, got %d", n, m)
}
return b[:], nil
}
// readByte reads a single byte.
func (d deserializationContext) readByte() (byte, error) {
arr, err := d.readBytes(1)
if err != nil {
return 0, err
}
return arr[0], nil
}
// readBool reads a boolean.
func (d deserializationContext) readBool() (bool, error) {
arr, err := d.readBytes(1)
if err != nil {
return false, err
}
switch v := arr[0]; v {
case 0x00:
return false, nil
case 0xff:
return true, nil
default:
return false, fmt.Errorf("unexpected value %x", v)
}
}
// readVarUint reads a variable-length uint64.
func (d deserializationContext) readVarUint() (uint64, error) {
// NOTE
// the original python implementation has no uint64 limit, but I
// don't think we'll ever need more that that.
val := uint64(0)
shift := uint(0)
for {
b, err := d.readByte()
if err != nil {
return 0, err
}
shifted := uint64(b&0x7f) << shift
// ghetto overflow check
if (shifted >> shift) != uint64(b&0x7f) {
return 0, fmt.Errorf("uint64 overflow")
}
val |= shifted
if b&0x80 == 0 {
return val, nil
}
shift += 7
}
}
// readVarBytes reads variable-length number of bytes.
func (d deserializationContext) readVarBytes(minLen, maxLen int) ([]byte, error) {
v, err := d.readVarUint()
if err != nil {
return nil, err
}
if v > math.MaxInt32 {
return nil, fmt.Errorf("int overflow")
}
vint := int(v)
if maxLen < vint || vint < minLen {
return nil, fmt.Errorf(
"varbytes length %d outside range (%d, %d)",
vint, minLen, maxLen,
)
}
return d.readBytes(vint)
}
// assertMagic removes reads the expected bytes from the stream. Returns an
// error if the bytes are unexpected.
func (d deserializationContext) assertMagic(expected []byte) error {
arr, err := d.readBytes(len(expected))
if err != nil {
return err
}
if !bytes.Equal(expected, arr) {
return fmt.Errorf(
"magic bytes mismatch, expected % x got % x",
expected, arr,
)
}
return nil
}
// assertEOF reads a byte and returns true if the end of the reader is reached.
// Careful: the read operation is a side-effect.
func (d deserializationContext) assertEOF() bool {
// Unfortunately we can't always do a zero-byte read here, since some
// reader implementations fail to return EOF. This means assertEOF
_, err := d.readByte()
return err == io.EOF
}
// newDeserializationContext returns a deserializationContext for a reader
func newDeserializationContext(r io.Reader) *deserializationContext {
// TODO
// bufio is used here to allow debugging via d.dump()
// once this code here is robust enough we can just pass r
return &deserializationContext{bufio.NewReader(r)}
}

153
serialize_test.go
View File

@@ -1,153 +0,0 @@
package opentimestamps
import (
"bytes"
"math"
"testing"
"github.com/stretchr/testify/assert"
)
func newDeserializationContextFromBytes(in []byte) *deserializationContext {
return newDeserializationContext(bytes.NewBuffer(in))
}
func TestReadWrite(t *testing.T) {
magic := []byte("magic")
buf := &bytes.Buffer{}
s := newSerializationContext(buf)
assert.NoError(t, s.writeBytes([]byte{0x00, 0x01}))
assert.NoError(t, s.writeByte(0x02))
assert.NoError(t, s.writeBool(true))
assert.NoError(t, s.writeBool(false))
assert.NoError(t, s.writeByte(0x03))
assert.NoError(t, s.writeVarUint(1))
assert.NoError(t, s.writeBytes([]byte{0x81, 0x00}))
assert.NoError(t, s.writeBytes([]byte{0x81, 0x01}))
assert.NoError(t, s.writeVarUint(0x100))
assert.NoError(t, s.writeVarUint(uint64(math.MaxUint32)+1))
assert.NoError(t, s.writeVarUint(math.MaxUint64))
assert.NoError(t, s.writeBytes([]byte{
// varunit excess MaxUint64
0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0x01,
}))
assert.NoError(t, s.writeBytes(magic))
assert.NoError(t, s.writeByte(0))
assert.NoError(t, s.writeBytes(magic))
data := buf.Bytes()
expectedData := []byte{
0x00, 0x01, // bytes [0x00, 0x01]
0x02, // byte 0x02
0xff, // bool true
0x00, // bool false
0x03, // bool error
0x01, // varuint 1
0x81, 0x00, // varuint 1
0x81, 0x01, // varuint 1 (alternative)
0x80, 0x02, // varuint 0x100
// varunit math.MaxUint32 + 1
0x80, 0x80, 0x80, 0x80, 0x10,
// varunit math.MaxUint64
0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff,
0xff, 0x01,
// varunit excess math.MaxUint64
0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0x01,
// "magic"
0x6d, 0x61, 0x67, 0x69, 0x63,
// zero
0x00,
// "magic"
0x6d, 0x61, 0x67, 0x69, 0x63,
}
assert.Equal(t, expectedData, data)
d := newDeserializationContextFromBytes(data)
{
v, err := d.readBytes(2)
assert.NoError(t, err)
assert.Equal(t, []byte{0x00, 0x01}, v)
}
{
v, err := d.readByte()
assert.NoError(t, err)
assert.Equal(t, byte(0x02), v)
}
{
v, err := d.readBool()
assert.NoError(t, err)
assert.Equal(t, true, v)
}
{
v, err := d.readBool()
assert.NoError(t, err)
assert.Equal(t, false, v)
}
{
_, err := d.readBool()
assert.Error(t, err)
}
{
v, err := d.readVarUint()
assert.NoError(t, err)
assert.Equal(t, uint64(1), v)
}
{
v, err := d.readVarUint()
assert.NoError(t, err)
assert.Equal(t, uint64(1), v)
}
{
v, err := d.readVarUint()
assert.NoError(t, err)
assert.Equal(t, uint64(0x81), v)
}
{
v, err := d.readVarUint()
assert.NoError(t, err)
assert.Equal(t, uint64(0x100), v)
}
{
v, err := d.readVarUint()
assert.NoError(t, err)
assert.Equal(t, uint64(math.MaxUint32)+uint64(1), v)
}
{
v, err := d.readVarUint()
assert.NoError(t, err)
assert.Equal(t, uint64(math.MaxUint64), uint64(v))
}
{
_, err := d.readVarUint()
assert.Error(t, err)
// read leftover 0x02
b, err := d.readByte()
assert.NoError(t, err)
assert.Equal(t, byte(0x01), b)
}
{
assert.NoError(t, d.assertMagic(magic))
// fails because of in-between 0x00
assert.Error(t, d.assertMagic(magic))
}
{
// read leftover byte
_, err := d.readByte()
assert.NoError(t, err)
assert.True(t, d.assertEOF())
}
}

183
timestamp.go
View File

@@ -1,183 +0,0 @@
package opentimestamps
import (
"bytes"
"fmt"
"io"
"strings"
)
type dumpConfig struct {
showMessage bool
showFlat bool
}
var defaultDumpConfig dumpConfig = dumpConfig{
showMessage: true,
showFlat: false,
}
// A timestampLink with the opCode being the link edge. The reference
// implementation uses a map, but the implementation is a bit complex. A list
// should work as well.
type tsLink struct {
opCode opCode
timestamp *Timestamp
}
// A Timestamp can contain many attestations and operations.
type Timestamp struct {
Message []byte
Attestations []Attestation
ops []tsLink
}
// Walk calls the passed function f for this timestamp and all
// downstream timestamps that are chained via operations.
func (t *Timestamp) Walk(f func(t *Timestamp)) {
f(t)
for _, l := range t.ops {
l.timestamp.Walk(f)
}
}
func (t *Timestamp) encode(ctx *serializationContext) error {
n := len(t.Attestations) + len(t.ops)
if n == 0 {
return fmt.Errorf("cannot encode empty timestamp")
}
prefixAtt := []byte{0x00}
prefixOp := []byte{}
nextNode := func(prefix []byte) error {
n -= 1
if n > 0 {
return ctx.writeByte(0xff)
}
if len(prefix) > 0 {
return ctx.writeBytes(prefix)
}
return nil
}
// FIXME attestations should be sorted
for _, att := range t.Attestations {
if err := nextNode(prefixAtt); err != nil {
return err
}
if err := encodeAttestation(ctx, att); err != nil {
return err
}
}
// FIXME ops should be sorted
for _, op := range t.ops {
if err := nextNode(prefixOp); err != nil {
return err
}
if err := op.opCode.encode(ctx); err != nil {
return err
}
if err := op.timestamp.encode(ctx); err != nil {
return err
}
}
return nil
}
func (t *Timestamp) DumpIndent(w io.Writer, indent int, cfg dumpConfig) {
if cfg.showMessage {
fmt.Fprintf(w, strings.Repeat(" ", indent))
fmt.Fprintf(w, "message %x\n", t.Message)
}
for _, att := range t.Attestations {
fmt.Fprint(w, strings.Repeat(" ", indent))
fmt.Fprintln(w, att)
}
for _, tsLink := range t.ops {
fmt.Fprint(w, strings.Repeat(" ", indent))
fmt.Fprintln(w, tsLink.opCode)
// fmt.Fprint(w, strings.Repeat(" ", indent))
// if the timestamp is indeed tree-shaped, show it like that
if !cfg.showFlat || len(t.ops) > 1 {
indent += 1
}
tsLink.timestamp.DumpIndent(w, indent, cfg)
}
}
func (t *Timestamp) DumpWithConfig(cfg dumpConfig) string {
b := &bytes.Buffer{}
t.DumpIndent(b, 0, cfg)
return b.String()
}
func (t *Timestamp) Dump() string {
return t.DumpWithConfig(defaultDumpConfig)
}
func parseTagOrAttestation(ts *Timestamp, ctx *deserializationContext, tag byte, message []byte, limit int) error {
if tag == 0x00 {
a, err := ParseAttestation(ctx)
if err != nil {
return err
}
ts.Attestations = append(ts.Attestations, a)
} else {
op, err := parseOp(ctx, tag)
if err != nil {
return err
}
newMessage, err := op.apply(message)
if err != nil {
return err
}
nextTs := &Timestamp{Message: newMessage}
err = parse(nextTs, ctx, newMessage, limit-1)
if err != nil {
return err
}
ts.ops = append(ts.ops, tsLink{op, nextTs})
}
return nil
}
func parse(ts *Timestamp, ctx *deserializationContext, message []byte, limit int) error {
if limit == 0 {
return fmt.Errorf("recursion limit")
}
var tag byte
var err error
for {
tag, err = ctx.readByte()
if err != nil {
return err
}
if tag == 0xff {
tag, err = ctx.readByte()
if err != nil {
return err
}
err := parseTagOrAttestation(ts, ctx, tag, message, limit)
if err != nil {
return err
}
} else {
break
}
}
return parseTagOrAttestation(ts, ctx, tag, message, limit)
}
func newTimestampFromContext(ctx *deserializationContext, message []byte) (*Timestamp, error) {
recursionLimit := 1000
ts := &Timestamp{Message: message}
err := parse(ts, ctx, message, recursionLimit)
if err != nil {
return nil, err
}
return ts, nil
}
func NewTimestampFromReader(r io.Reader, message []byte) (*Timestamp, error) {
return newTimestampFromContext(newDeserializationContext(r), message)
}

11
util.go
View File

@@ -1,11 +0,0 @@
package opentimestamps
import "encoding/hex"
func mustDecodeHex(in string) []byte {
out, err := hex.DecodeString(in)
if err != nil {
panic(err)
}
return out
}

86
verifier.go
View File

@@ -1,86 +0,0 @@
package opentimestamps
import (
"fmt"
"math"
"time"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/wire"
)
type Bitcoin interface {
GetBlockHash(height int64) (*chainhash.Hash, error)
GetBlockHeader(hash *chainhash.Hash) (*wire.BlockHeader, error)
}
// VerifyAttestation checks a BitcoinAttestation using a given hash digest. It
// returns the time of the block if the verification succeeds, an error
// otherwise.
func VerifyAttestation(bitcoinInterface Bitcoin, digest []byte, a *BitcoinAttestation) (*time.Time, error) {
if a.Height > math.MaxInt64 {
return nil, fmt.Errorf("illegal block height")
}
blockHash, err := bitcoinInterface.GetBlockHash(int64(a.Height))
if err != nil {
return nil, err
}
h, err := bitcoinInterface.GetBlockHeader(blockHash)
if err != nil {
return nil, err
}
merkleRootBytes := h.MerkleRoot[:]
err = a.VerifyAgainstBlockHash(digest, merkleRootBytes)
if err != nil {
return nil, err
}
utc := h.Timestamp.UTC()
return &utc, nil
}
// A BitcoinVerification is the result of verifying a BitcoinAttestation
type BitcoinVerification struct {
Timestamp *Timestamp
Attestation *BitcoinAttestation
AttestationTime *time.Time
Error error
}
// BitcoinVerifications returns the all bitcoin attestation results for the
// timestamp.
func BitcoinVerifications(bitcoinInterface Bitcoin, t *Timestamp) (res []BitcoinVerification) {
t.Walk(func(ts *Timestamp) {
for _, att := range ts.Attestations {
btcAtt, ok := att.(*BitcoinAttestation)
if !ok {
continue
}
attTime, err := VerifyAttestation(bitcoinInterface, ts.Message, btcAtt)
res = append(res, BitcoinVerification{
Timestamp: ts,
Attestation: btcAtt,
AttestationTime: attTime,
Error: err,
})
}
})
return res
}
// Verify returns the earliest bitcoin-attested time, or nil if none can be
// found or verified successfully.
func Verify(bitcoinInterface Bitcoin, t *Timestamp) (ret *time.Time, err error) {
res := BitcoinVerifications(bitcoinInterface, t)
for _, r := range res {
if r.Error != nil {
err = r.Error
continue
}
if ret == nil || r.AttestationTime.Before(*ret) {
ret = r.AttestationTime
}
}
return
}