local-server/cmd/dkl-local-server/render-context.go

package main

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"path"
	"path/filepath"
	"text/template"

	cfsslconfig "github.com/cloudflare/cfssl/config"
	restful "github.com/emicklei/go-restful"
	yaml "gopkg.in/yaml.v2"

	"novit.tech/direktil/pkg/config"
	"novit.tech/direktil/pkg/localconfig"

	bsconfig "novit.tech/direktil/pkg/bootstrapconfig"
)

var cmdlineParam = restful.QueryParameter("cmdline", "Linux kernel cmdline addition")

type renderContext struct {
	Host      *localconfig.Host
	SSLConfig *cfsslconfig.Config

	// Linux kernel extra cmdline
	CmdLine string `yaml:"-"`
}

func renderCtx(w http.ResponseWriter, r *http.Request, ctx *renderContext, what string,
	create func(out io.Writer, ctx *renderContext) error) error {

	tag, err := ctx.Tag()
	if err != nil {
		return err
	}

	ctx.CmdLine = r.URL.Query().Get(cmdlineParam.Data().Name)

	if ctx.CmdLine != "" {
		what = what + "?cmdline=" + url.QueryEscape(ctx.CmdLine)
	}

	// get it or create it
	content, meta, err := casStore.GetOrCreate(tag, what, func(out io.Writer) error {
		log.Printf("building %s for %q", what, ctx.Host.Name)
		return create(out, ctx)
	})

	if err != nil {
		return err
	}

	// serve it
	log.Printf("sending %s for %q", what, ctx.Host.Name)
	http.ServeContent(w, r, what, meta.ModTime(), content)
	return nil
}

func sslConfigFromLocalConfig(cfg *localconfig.Config) (sslCfg *cfsslconfig.Config, err error) {
	if len(cfg.SSLConfig) == 0 {
		sslCfg = &cfsslconfig.Config{}
	} else {
		sslCfg, err = cfsslconfig.LoadConfig([]byte(cfg.SSLConfig))
		if err != nil {
			return
		}
	}
	return
}

func newRenderContext(host *localconfig.Host, cfg *localconfig.Config) (ctx *renderContext, err error) {
	sslCfg, err := sslConfigFromLocalConfig(cfg)
	if err != nil {
		return
	}

	return &renderContext{
		Host:      host,
		SSLConfig: sslCfg,
	}, nil
}

func (ctx *renderContext) Config() (ba []byte, cfg *config.Config, err error) {
	ba, err = ctx.render(ctx.Host.Config)
	if err != nil {
		return
	}

	cfg = &config.Config{}
	if err = yaml.Unmarshal(ba, cfg); err != nil {
		return
	}

	return
}

func (ctx *renderContext) BootstrapConfig() (ba []byte, cfg *bsconfig.Config, err error) {
	ba, err = ctx.render(ctx.Host.BootstrapConfig)
	if err != nil {
		return
	}

	cfg = &bsconfig.Config{}
	if err = yaml.Unmarshal(ba, cfg); err != nil {
		return
	}

	return
}

func (ctx *renderContext) render(templateText string) (ba []byte, err error) {
	tmpl, err := template.New(ctx.Host.Name + "/config").
		Funcs(ctx.TemplateFuncs()).
		Parse(templateText)

	if err != nil {
		return
	}

	buf := bytes.NewBuffer(make([]byte, 0, 4096))
	if err = tmpl.Execute(buf, nil); err != nil {
		return
	}

	ba = buf.Bytes()
	return
}

func (ctx *renderContext) distFilePath(path ...string) string {
	return filepath.Join(append([]string{*dataDir, "dist"}, path...)...)
}

func (ctx *renderContext) Tag() (string, error) {
	h := sha256.New()

	_, cfg, err := ctx.Config()
	if err != nil {
		return "", err
	}

	enc := yaml.NewEncoder(h)

	for _, o := range []interface{}{cfg, ctx} {
		if err := enc.Encode(o); err != nil {
			return "", err
		}
	}

	return hex.EncodeToString(h.Sum(nil)), nil
}

func asMap(v interface{}) map[string]interface{} {
	ba, err := yaml.Marshal(v)
	if err != nil {
		panic(err) // shouldn't happen
	}

	result := make(map[string]interface{})

	if err := yaml.Unmarshal(ba, result); err != nil {
		panic(err) // shouldn't happen
	}

	return result
}

func (ctx *renderContext) TemplateFuncs() map[string]any {
	funcs := templateFuncs(ctx.SSLConfig)

	for name, method := range map[string]any{
		"ssh_host_keys": func(dir, cluster, host string) (s string, err error) {
			if host == "" {
				host = ctx.Host.Name
			}
			if host != ctx.Host.Name {
				err = fmt.Errorf("wrong host name")
				return
			}

			pairs, err := getSSHKeyPairs(host)
			if err != nil {
				return
			}

			files := make([]config.FileDef, 0, len(pairs)*2)

			for _, pair := range pairs {
				basePath := path.Join(dir, "ssh_host_"+pair.Type+"_key")
				files = append(files, []config.FileDef{
					{
						Path:    basePath,
						Mode:    0600,
						Content: pair.Private,
					},
					{
						Path:    basePath + ".pub",
						Mode:    0644,
						Content: pair.Public,
					},
				}...)
			}

			return asYaml(files)
		},
		"host_download_token": func() (token string, err error) {
			key := ctx.Host.Name
			token, found, err := hostDownloadTokens.Get(key)
			if err != nil {
				return
			}

			if !found {
				token, err = newToken(32)
				if err != nil {
					return
				}

				err = hostDownloadTokens.Put(key, token)
				if err != nil {
					return
				}
			}

			return
		},
	} {
		funcs[name] = method
	}

	return funcs
}