DateKeys/capsule/example_test.go

package capsule_test

import (
	"bytes"
	"context"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"strings"
	"time"

	datekeys "g.activething.com/go/DateKeys"
	"g.activething.com/go/DateKeys/accesskey"
	"g.activething.com/go/DateKeys/capsule"
	"g.activething.com/go/DateKeys/profile"
	"g.activething.com/go/DateKeys/provider"
)

// The published Quicknet signature of round 1000. In real use the release
// comes from drand.New(), which verifies it the same way.
var round1000, _ = hex.DecodeString("b44679b9a59af2ec876b1a6b1ad52ea9b1615fc3982b19576350f93447cb1125e342b73a8dd2bacbe47e4b6b63ed5e39")

// memorySink is a capsule.Sink that keeps the files in memory. A Sink that
// writes to disk, as the datekeys CLI does, writes them to a temporary
// folder and moves it into place in Commit.
type memorySink struct{ files []*bytes.Buffer }

func (m *memorySink) Begin(h *capsule.Head) error {
	m.files = make([]*bytes.Buffer, len(h.Files))
	return nil
}

func (m *memorySink) Create(i int) (io.WriteCloser, error) {
	m.files[i] = new(bytes.Buffer)
	return bufferCloser{m.files[i]}, nil
}

func (m *memorySink) Commit() error { return nil }
func (m *memorySink) Abort()        { m.files = nil }

type bufferCloser struct{ io.Writer }

func (bufferCloser) Close() error { return nil }

// source is a capsule.Source of a file held in memory.
func source(path, content string) capsule.Source {
	return capsule.Source{Path: path, Size: int64(len(content)), Open: func() (io.ReadCloser, error) {
		return io.NopCloser(strings.NewReader(content)), nil
	}}
}

func Example() {
	reg, err := profile.Default()
	if err != nil {
		panic(err)
	}
	p := profile.Quicknet()

	// A clock stopped at the Quicknet genesis makes round 1000
	// (2023-08-23T15:59:24Z) "the future", so the example runs offline.
	genesis := func() time.Time { return time.Unix(p.GenesisTime, 0) }
	var dkc bytes.Buffer
	res, err := capsule.EncryptFiles(&dkc, []capsule.Source{source("carta.txt", "hello from the past")}, capsule.EncryptOptions{
		Profile:        p,
		UnlockAt:       time.Date(2023, 8, 23, 15, 59, 24, 0, time.UTC),
		Policy:         capsule.TimeAndKey,
		NewPortableKey: true,
		Comment:        "Para abrir dentro de un rato.",
		Now:            genesis,
	})
	if err != nil {
		panic(err)
	}
	var dkk bytes.Buffer
	if err := accesskey.Encode(&dkk, res.PortableKey); err != nil {
		panic(err)
	}
	fmt.Println("round", res.DateKey.Round, "unlocks at", res.UnlockAt.Format(time.RFC3339))

	// Before the round: no request is made.
	key, _ := accesskey.Decode(&dkk)
	src := provider.ReleaseSourceFunc(func(_ context.Context, _ *profile.Profile, c provider.Condition) (provider.Release, error) {
		return provider.Release{Round: c.Round, Signature: round1000}, nil
	})
	files := &memorySink{}
	opts := capsule.OpenOptions{Registry: reg, Source: src, AccessKey: key, Now: genesis, Sink: files}
	_, err = capsule.Open(context.Background(), nil, bytes.NewReader(dkc.Bytes()), opts)
	fmt.Println("too early:", errors.Is(err, datekeys.ErrReleaseUnavailable))

	// After the round: the release is verified locally and the capsule opens.
	// The verdicts of the security area come before the comment.
	opts.Now = time.Now
	opened, err := capsule.Open(context.Background(), nil, bytes.NewReader(dkc.Bytes()), opts)
	if err != nil {
		panic(err)
	}
	for _, line := range opened.Verdicts.Lines() {
		fmt.Println(line)
	}
	fmt.Println(opened.Head.Comment)
	fmt.Println(opened.Head.Files[0].Path+":", files.files[0])
	// Output:
	// round 1000 unlocks at 2023-08-23T15:59:24Z
	// too early: true
	// Sin firma de autor.
	// Para abrir dentro de un rato.
	// carta.txt: hello from the past
}

func ExampleInspect() {
	reg, _ := profile.Default()
	p := profile.Quicknet()
	var dkc bytes.Buffer
	_, _ = capsule.EncryptFiles(&dkc, []capsule.Source{source("x.txt", "x")}, capsule.EncryptOptions{
		Profile:  p,
		UnlockAt: time.Date(2030, 1, 1, 0, 0, 0, 0, time.UTC),
		Now:      func() time.Time { return time.Date(2026, 9, 25, 0, 0, 0, 0, time.UTC) },
	})
	in, err := capsule.Inspect(bytes.NewReader(dkc.Bytes()), capsule.InspectOptions{Registry: reg})
	if err != nil {
		panic(err)
	}
	fmt.Println(in.Header.Policy, in.Header.DateKey.Round, in.UnlockAt.Format(time.RFC3339), len(in.Checks), "checks passed")
	// Output: time_only 66884212 2030-01-01T00:00:00Z 8 checks passed
}