/
preseed.go
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/
preseed.go
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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2023 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 asserts
import (
"crypto"
"fmt"
"regexp"
"time"
"github.com/snapcore/snapd/snap/naming"
)
// validSystemLabel is the regex describing a valid system label. Typically
// system labels are expected to be date based, eg. 20201116, but for
// completeness follow the same rule as model names (incl. one letter model
// names and thus system labels), with the exception that uppercase letters are
// not allowed, as the systems will often be stored in a FAT filesystem.
var validSystemLabel = regexp.MustCompile("^[a-z0-9](?:-?[a-z0-9])*$")
// IsValidSystemLabel checks whether the string is a valid UC20 seed system
// label.
func IsValidSystemLabel(label string) error {
if !validSystemLabel.MatchString(label) {
return fmt.Errorf("invalid seed system label: %q", label)
}
return nil
}
// PreseedSnap holds the details about a snap constrained by a preseed assertion.
type PreseedSnap struct {
Name string
SnapID string
Revision int
}
// SnapName implements naming.SnapRef.
func (s *PreseedSnap) SnapName() string {
return s.Name
}
// ID implements naming.SnapRef.
func (s *PreseedSnap) ID() string {
return s.SnapID
}
// Preseed holds preseed assertion, which is a statement about system-label,
// model, set of snaps and preseed artifact used for preseeding of UC20 system.
type Preseed struct {
assertionBase
snaps []*PreseedSnap
timestamp time.Time
}
// Series returns the series that this assertion is valid for.
func (p *Preseed) Series() string {
return p.HeaderString("series")
}
// BrandID returns the brand identifier.
func (p *Preseed) BrandID() string {
return p.HeaderString("brand-id")
}
// Model returns the model name identifier.
func (p *Preseed) Model() string {
return p.HeaderString("model")
}
// SystemLabel returns the label of the seeded system.
func (p *Preseed) SystemLabel() string {
return p.HeaderString("system-label")
}
// Timestamp returns the time when the preseed assertion was issued.
func (p *Preseed) Timestamp() time.Time {
return p.timestamp
}
// ArtifactSHA3_384 returns the checksum of preseeding artifact.
func (p *Preseed) ArtifactSHA3_384() string {
return p.HeaderString("artifact-sha3-384")
}
// Snaps returns the snaps for preseeding.
func (p *Preseed) Snaps() []*PreseedSnap {
return p.snaps
}
func checkPreseedSnap(snap map[string]interface{}) (*PreseedSnap, error) {
name, err := checkNotEmptyStringWhat(snap, "name", "of snap")
if err != nil {
return nil, err
}
if err := naming.ValidateSnap(name); err != nil {
return nil, fmt.Errorf("invalid snap name %q", name)
}
what := fmt.Sprintf("of snap %q", name)
// snap id can be omitted if the model allows for unasserted snaps
var snapID string
if _, ok := snap["id"]; ok {
snapID, err = checkStringMatchesWhat(snap, "id", what, naming.ValidSnapID)
if err != nil {
return nil, err
}
}
var snapRevision int
if _, ok := snap["revision"]; ok {
var err error
snapRevision, err = checkSnapRevisionWhat(snap, "revision", what)
if err != nil {
return nil, err
}
}
if snapID != "" && snapRevision <= 0 {
return nil, fmt.Errorf("snap revision is required when snap id is set")
}
if snapID == "" && snapRevision > 0 {
return nil, fmt.Errorf("snap id is required when revision is set")
}
return &PreseedSnap{
Name: name,
SnapID: snapID,
Revision: snapRevision,
}, nil
}
func checkPreseedSnaps(snapList interface{}) ([]*PreseedSnap, error) {
const wrongHeaderType = `"snaps" header must be a list of maps`
entries, ok := snapList.([]interface{})
if !ok {
return nil, fmt.Errorf(wrongHeaderType)
}
seen := make(map[string]bool, len(entries))
seenIDs := make(map[string]string, len(entries))
snaps := make([]*PreseedSnap, 0, len(entries))
for _, entry := range entries {
snap, ok := entry.(map[string]interface{})
if !ok {
return nil, fmt.Errorf(wrongHeaderType)
}
preseedSnap, err := checkPreseedSnap(snap)
if err != nil {
return nil, err
}
if seen[preseedSnap.Name] {
return nil, fmt.Errorf("cannot list the same snap %q multiple times", preseedSnap.Name)
}
seen[preseedSnap.Name] = true
snapID := preseedSnap.SnapID
if snapID != "" {
if underName := seenIDs[snapID]; underName != "" {
return nil, fmt.Errorf("cannot specify the same snap id %q multiple times, specified for snaps %q and %q", snapID, underName, preseedSnap.Name)
}
seenIDs[snapID] = preseedSnap.Name
}
snaps = append(snaps, preseedSnap)
}
return snaps, nil
}
func assemblePreseed(assert assertionBase) (Assertion, error) {
// because the authority-id and model-id can differ (as per the model),
// authority-id should be validated against allowed IDs when the preseed
// blob is being checked
_, err := checkModel(assert.headers)
if err != nil {
return nil, err
}
_, err = checkStringMatches(assert.headers, "system-label", validSystemLabel)
if err != nil {
return nil, err
}
snapList, ok := assert.headers["snaps"]
if !ok {
return nil, fmt.Errorf(`"snaps" header is mandatory`)
}
snaps, err := checkPreseedSnaps(snapList)
if err != nil {
return nil, err
}
_, err = checkDigest(assert.headers, "artifact-sha3-384", crypto.SHA3_384)
if err != nil {
return nil, err
}
timestamp, err := checkRFC3339Date(assert.headers, "timestamp")
if err != nil {
return nil, err
}
return &Preseed{
assertionBase: assert,
snaps: snaps,
timestamp: timestamp,
}, nil
}