Generate a leaf, non-self-signed account-key assertion with associated private key for use with snapd

leaf-account-key-testkeys-assertion.go

// -*- Mode: Go; indent-tabs-mode: t -*-

/*
 * Copyright (C) 2021 Canonical Ltd
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package main

import (
	"bytes"
	"crypto/rsa"
	"fmt"
	"log"
	"time"

	"github.com/snapcore/snapd/asserts"
	"github.com/snapcore/snapd/asserts/assertstest"
	"github.com/snapcore/snapd/asserts/systestkeys"
	"golang.org/x/crypto/openpgp/armor"
	"golang.org/x/crypto/openpgp/packet"
)

var (
	v1FixedTimestamp = time.Date(2016, time.January, 1, 0, 0, 0, 0, time.UTC)
)

// from pedronis @ https://gist.github.com/pedronis/d4ba5849e40814f1fa5ee22d8b525471
func dumpRSAKey(rsaKey *rsa.PrivateKey) string {
	buf := &bytes.Buffer{}
	pkt := packet.NewRSAPrivateKey(v1FixedTimestamp, rsaKey)
	arm, err := armor.Encode(buf, "PGP PRIVATE KEY", nil)
	if err != nil {
		panic(err)
	}
	err = pkt.Serialize(arm)
	if err != nil {
		panic(err)
	}
	err = arm.Close()
	if err != nil {
		panic(err)
	}
	blob := buf.String()
	fmt.Println(blob)
	return blob

}

func main() {
	// generate a key
	repairRootKey, repairRootRSAKey := assertstest.GenerateKey(4096)

	db, err := asserts.OpenDatabase(&asserts.DatabaseConfig{
		KeypairManager: asserts.NewMemoryKeypairManager(),
		Backstore:      asserts.NewMemoryBackstore(),
		Trusted:        systestkeys.Trusted,
	})
	if err != nil {
		log.Fatalf("error opening database: %v", err)
	}

	// for signing import the testrootorg key
	rootSigningKey, _ := assertstest.ReadPrivKey(systestkeys.TestRootPrivKey)
	if err := db.ImportKey(rootSigningKey); err != nil {
		log.Fatalf("error importing private signing key: %v", err)
	}

	headers := map[string]interface{}{
		// account-id and authority-id must be the same for root of trust
		// assertions like this
		"account-id":          "testrootrepair",
		"authority-id":        "testrootrepair",
		"name":                "test-root-repair",
		"since":               time.Now().Format(time.RFC3339),
		"public-key-sha3-384": repairRootKey.PublicKey().ID(),
	}

	// the public key is the body of the account key assertion
	body, err := asserts.EncodePublicKey(repairRootKey.PublicKey())
	if err != nil {
		log.Fatalf("error encoding public key of private key: %v", err)
	}
	a, err := db.Sign(asserts.AccountKeyType, headers, body, rootSigningKey.PublicKey().ID())
	if err != nil {
		log.Fatalf("error signing account-key: %v", err)
	}

	// output the account-key assertion itself
	fmt.Println(string(asserts.Encode(a)))

	// also export the private key in ASCII
	dumpRSAKey(repairRootRSAKey)
}