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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2020 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 bootloader
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"os"
"strconv"
"strings"
"github.com/snapcore/snapd/bootloader/assets"
)
var errNoEdition = errors.New("no edition")
// editionFromDiskConfigAsset extracts the edition information from a boot
// config asset on disk.
func editionFromDiskConfigAsset(p string) (uint, error) {
f, err := os.Open(p)
if err != nil {
if os.IsNotExist(err) {
return 0, errNoEdition
}
return 0, fmt.Errorf("cannot load existing config asset: %v", err)
}
defer f.Close()
return editionFromConfigAsset(f)
}
const editionHeader = "# Snapd-Boot-Config-Edition: "
// editionFromConfigAsset extracts edition information from boot config asset.
func editionFromConfigAsset(asset io.Reader) (uint, error) {
scanner := bufio.NewScanner(asset)
if !scanner.Scan() {
err := fmt.Errorf("cannot read config asset: unexpected EOF")
if sErr := scanner.Err(); sErr != nil {
err = fmt.Errorf("cannot read config asset: %v", err)
}
return 0, err
}
line := scanner.Text()
if !strings.HasPrefix(line, editionHeader) {
return 0, errNoEdition
}
editionStr := line[len(editionHeader):]
editionStr = strings.TrimSpace(editionStr)
edition, err := strconv.ParseUint(editionStr, 10, 32)
if err != nil {
return 0, fmt.Errorf("cannot parse asset edition: %v", err)
}
return uint(edition), nil
}
// editionFromInternalConfigAsset extracts edition information from a named
// internal boot config asset.
func editionFromInternalConfigAsset(assetName string) (uint, error) {
data := assets.Internal(assetName)
if data == nil {
return 0, fmt.Errorf("internal error: no boot asset for %q", assetName)
}
return editionFromConfigAsset(bytes.NewReader(data))
}
// configAsset is a boot config asset, such as text script, used by grub or
// u-boot.
type configAsset struct {
body []byte
parsedEdition uint
}
func (g *configAsset) Edition() uint {
return g.parsedEdition
}
func (g *configAsset) Raw() []byte {
return g.body
}
func configAssetFrom(data []byte) (*configAsset, error) {
edition, err := editionFromConfigAsset(bytes.NewReader(data))
if err != nil && err != errNoEdition {
return nil, err
}
gbs := &configAsset{
body: data,
parsedEdition: edition,
}
return gbs, nil
}
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