updater.go

//
// Author:: Salim Afiune Maya (<afiune@lacework.net>)
// Copyright:: Copyright 2020, Lacework Inc.
// License:: Apache License, Version 2.0
//
// 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.
//

// A library to check for available updates of Lacework projects.
package lwupdater

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"

	"github.com/cenkalti/backoff/v4"
	"github.com/lacework/go-sdk/v2/lwlogger"
	"github.com/pkg/errors"
)

const (
	// GithubOrganization is the default Github organization where
	// Lacework stores their open source projects
	GithubOrganization = "lacework"

	// DisableEnv controls the overall check for updates behavior, when
	// this environment variable is set, we do not check for updates
	DisableEnv = "LW_UPDATES_DISABLE"
)

var log = lwlogger.New("")

// Version is used to check project versions and store it into a cache file
// normally at the directory `~/.config/lacework`, to execute regular version checks
type Version struct {
	Project             string               `json:"project"`
	CurrentVersion      string               `json:"current_version"`
	LatestVersion       string               `json:"latest_version"`
	LastCheckTime       time.Time            `json:"last_check_time"`
	Outdated            bool                 `json:"outdated"`
	ComponentsLastCheck map[string]time.Time `json:"components_last_check,omitempty"`
}

// StoreCache stores version information into the provided path
func (cache *Version) StoreCache(path string) error {
	buf := new(bytes.Buffer)
	if err := json.NewEncoder(buf).Encode(cache); err != nil {
		return err
	}

	err := os.WriteFile(path, buf.Bytes(), 0644)
	if err != nil {
		return err
	}

	return nil
}

// StoreCache stores version information into the provided path
func (cache *Version) CheckComponentBefore(component string, checkTime time.Time) bool {
	if cache.ComponentsLastCheck == nil {
		cache.ComponentsLastCheck = make(map[string]time.Time)
	}

	if lastCheck, ok := cache.ComponentsLastCheck[component]; !ok || lastCheck.Before(checkTime) {
		return true
	}
	return false
}

// Check verifies if the a project is outdated based of the current version
func Check(project, current string) (*Version, error) {
	if disabled := os.Getenv(DisableEnv); disabled != "" {
		return new(Version), nil
	}

	release, err := getGitRelease(project, "latest")
	if err != nil {
		return new(Version), err
	}

	outdated := false
	if !strings.Contains(current, "dev") && current != release.TagName {
		outdated = true
	}

	return &Version{
		Project:        project,
		CurrentVersion: current,
		LatestVersion:  release.TagName,
		LastCheckTime:  time.Now(),
		Outdated:       outdated,
	}, nil
}

// LoadCache loads a version cache file from the provided path
func LoadCache(path string) (*Version, error) {
	cacheJSON, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}

	var versionCache = new(Version)
	err = json.Unmarshal(cacheJSON, versionCache)
	return versionCache, err
}

// getGitRelease uses the git API to fetch the release information of a project.
// This function could hit request rate limits wich are roughly 60 every 30m, to
// check your current rate limits run: curl https://api.github.com/rate_limit
// If the GITHUB_TOKEN environment variable is set, then this function will use
// it to authenticate the API request, which grants higher rate limits.
func getGitRelease(project, version string) (*gitReleaseResponse, error) {
	if project == "" {
		return nil, errors.New("specify a valid project")
	}
	if version == "" {
		version = "latest"
	}

	var (
		c = http.Client{}
		u = url.URL{
			Scheme: "https",
			Host:   "api.github.com",
			Path: fmt.Sprintf(
				"/repos/%s/%s/releases/latest",
				GithubOrganization, project,
			),
		}
	)
	if version != "latest" {
		u.Path = fmt.Sprintf("/repos/%s/%s/releases/tags/%s",
			GithubOrganization, project, version)
	}

	req, err := http.NewRequest("GET", u.String(), nil)
	if err != nil {
		return nil, err
	}

	// Set the user agent since it is required
	// https://developer.github.com/v3/#user-agent-required
	req.Header.Set("User-Agent", "lacework-updater")

	token := os.Getenv("GITHUB_TOKEN")
	if len(token) > 0 {
		req.Header.Set("Authorization", "Bearer "+token)
	}

	var resp *http.Response
	err = backoff.Retry(func() error {
		resp, err = c.Do(req)
		if err != nil {
			return err
		}
		if resp.StatusCode < 200 || resp.StatusCode > 299 {
			logHeaders(resp)
			return errors.New(resp.Status)
		}
		return nil
	}, backoffStrategy())
	if err != nil {
		return nil, err
	}

	var gitRelRes gitReleaseResponse
	if err := json.NewDecoder(resp.Body).Decode(&gitRelRes); err != nil {
		return nil, err
	}

	return &gitRelRes, nil
}

func backoffStrategy() *backoff.ExponentialBackOff {
	strategy := backoff.NewExponentialBackOff()
	strategy.InitialInterval = 2 * time.Second
	strategy.MaxElapsedTime = 1 * time.Minute
	return strategy
}

func logHeaders(resp *http.Response) {
	var headers strings.Builder
	for key, values := range resp.Header {
		headers.WriteString(fmt.Sprintf("%s: %s\n", key, strings.Join(values, ",")))
	}
	log.Debug(headers.String())
}

type gitReleaseResponse struct {
	ID              int32     `json:"id"`
	Url             string    `json:"url"`
	HtmlUrl         string    `json:"html_url"`
	AssetsUrl       string    `json:"assets_url"`
	UploadUrl       string    `json:"upload_url"`
	TarballUrl      string    `json:"tarball_url"`
	ZipballUrl      string    `json:"zipball_url"`
	NodeID          string    `json:"node_id"`
	TagName         string    `json:"tag_name"`
	TargetCommitish string    `json:"target_commitish"`
	Name            string    `json:"name"`
	Body            string    `json:"body"`
	Draft           bool      `json:"draft"`
	Prerelease      bool      `json:"prerelease"`
	CreatedAt       time.Time `json:"created_at"`
	PublishedAt     time.Time `json:"published_at"`
}