src/cmd/cos_customizer/sed_grub_config.go

// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"context"
	"encoding/json"
	"flag"
	"log"

	"cos.googlesource.com/cos/tools.git/src/pkg/config"
	"cos.googlesource.com/cos/tools.git/src/pkg/fs"
	"cos.googlesource.com/cos/tools.git/src/pkg/provisioner"
	"github.com/google/subcommands"
)

// SedGrubConfig implements subcommands.Command for the "sed-grub-config"
// command. This command runs a given sed script on the grub configuration.
// Useful for editing the kernel command line.
type SedGrubConfig struct {
	sedScript string
}

// Name implements subcommands.Command.Name.
func (s *SedGrubConfig) Name() string {
	return "sed-grub-config"
}

// Synopsis implements subcommands.Command.Synopsis.
func (s *SedGrubConfig) Synopsis() string {
	return "Edit the grub configuration during the image build. Changes take effect on the next reboot. This step does not do any reboots."
}

// Usage implements subcommands.Command.Usage.
func (s *SedGrubConfig) Usage() string {
	return `sed-grub-config [flags]
`
}

// SetFlags implements subcommands.Command.SetFlags.
func (s *SedGrubConfig) SetFlags(f *flag.FlagSet) {
	f.StringVar(&s.sedScript, "sed-script", "", `Sed script to run, e.g. "s|module.sig_enforce=1|module.sig_enforce=0|g".`)
}

func (s *SedGrubConfig) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
	if f.NArg() != 0 {
		f.Usage()
		return subcommands.ExitUsageError
	}
	files := args[0].(*fs.Files)
	var provConfig provisioner.Config
	if err := config.LoadFromFile(files.ProvConfig, &provConfig); err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}
	buf, err := json.Marshal(&provisioner.SedGrubConfigStep{
		SedScript: s.sedScript,
	})
	if err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}
	provConfig.Steps = append(provConfig.Steps, provisioner.StepConfig{
		Type: "SedGrubConfigStep",
		Args: json.RawMessage(buf),
	})
	if err := config.SaveConfigToPath(files.ProvConfig, &provConfig); err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}
	return subcommands.ExitSuccess
}