cert-manager-webhook-sthome/pkg/shell/shell.go

package shell

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"os/exec"
	"sync"
	"time"

	"github.com/cert-manager/cert-manager/pkg/acme/webhook/apis/acme/v1alpha1"
	"k8s.io/klog/v2"
)

const (
	bashShell = "/bin/bash"
	zshShell  = "/bin/zsh"
	//Workdir   = "/workdir"
	//AcmeDir   = "/acme"
	Shell = bashShell

	AuthScript       = "acmeauth.sh"
	DnsUpdScript     = "updatedns.sh"
	KrbConf          = "krb5.conf"
	Keytab           = "krb5.keytab"
	AuthScriptMode   = 0744
	DnsUpdScriptMode = 0744
	KrbConfMode      = 0644
	KeytabMode       = 0644
)

var (
	Workdir     = os.Getenv("WORKDIR")
	AcmeDir     = os.Getenv("ACMEDIR")
	AcmeAuthCmd = Workdir + "/" + AuthScript
	mutex       sync.Mutex // mutex is used to define a critical section of code.
)

// CapturingPassThroughWriter is a writer that remembers
// data written to it and passes it to w
type CapturingPassThroughWriter struct {
	buf bytes.Buffer
	w   io.Writer
}

// NewCapturingPassThroughWriter creates new CapturingPassThroughWriter
func NewCapturingPassThroughWriter(w io.Writer) *CapturingPassThroughWriter {
	return &CapturingPassThroughWriter{
		w: w,
	}
}

func (w *CapturingPassThroughWriter) Write(d []byte) (int, error) {
	w.buf.Write(d)
	return w.w.Write(d)
}

// Bytes returns bytes written to the writer
func (w *CapturingPassThroughWriter) Bytes() []byte {
	return w.buf.Bytes()
}

func SetChallenge(ch *v1alpha1.ChallengeRequest) (bool, error) {
	SetupWorkdir() // update workdir if any of the copied files were updated on host
	return Execute(
		Shell,
		AcmeAuthCmd,
		"set",
		ch.DNSName,
		ch.ResolvedFQDN,
		ch.Key,
		//"-l",
		//"\"\"", //localip,
		//"-v",
	)
}

func UnsetChallenge(ch *v1alpha1.ChallengeRequest) (bool, error) {
	SetupWorkdir() // update workdir if any of the copied files were updated on host
	return Execute(
		Shell,
		AcmeAuthCmd,
		"unset",
		ch.DNSName,
		ch.ResolvedFQDN,
		ch.Key,
		//"-l",
		//"\"\"", //localip,
		//"-v",
	)
}

func Execute(shell string, arg ...string) (bool, error) {
	var errStdout, errStderr error
	crlf := []byte("\r\n")
	lf := []byte("\n")

	cmd := exec.Command(shell, arg...)
	stdoutIn, _ := cmd.StdoutPipe()
	stderrIn, _ := cmd.StderrPipe()
	stdout := NewCapturingPassThroughWriter(os.Stdout)
	stderr := NewCapturingPassThroughWriter(os.Stderr)
	err := cmd.Start()
	if err != nil {
		klog.Fatalf("cmd.Start() failed with '%s'\n", err)
	}

	var wg sync.WaitGroup
	wg.Add(1)

	go func() {
		_, errStdout = io.Copy(stdout, stdoutIn)
		wg.Done()
	}()

	_, errStderr = io.Copy(stderr, stderrIn)
	wg.Wait()

	err = cmd.Wait()
	if err != nil {
		klog.Fatalf("cmd.Run() failed with %s\n", err)
	}
	if errStdout != nil || errStderr != nil {
		klog.Fatalf("failed to capture stdout or stderr\n")
	}
	//outStr, errStr := string(stdout.Bytes()), string(stderr.Bytes())
	//fmt.Printf("\nout:\n%s\nerr:\n%s\n", outStr, errStr)
	errb := bytes.TrimSuffix(stderr.Bytes(), crlf)
	errb = bytes.TrimSuffix(errb, lf)
	if errb != nil {
		klog.Infof("err:\n%s\n", string(errb))
	}
	return true, nil
}

func SetupWorkdir() {
	mutex.Lock()
	defer mutex.Unlock()
	err := createWorkdir()
	if err != nil {
		panic(err)
	}
	updateWorkdir()
}

func updateWorkdir() {
	updateIfStale(AuthScript, AuthScriptMode)
	updateIfStale(DnsUpdScript, DnsUpdScriptMode)
	updateIfStale(KrbConf, KrbConfMode)
	updateIfStale(Keytab, KeytabMode)
}

func createWorkdir() error {
	finfo, err := os.Stat(Workdir)
	if os.IsNotExist(err) {
		klog.Infof("Creating folder \"%s\"", Workdir)
		err = os.Mkdir(Workdir, 0755)
		if err != nil {
			panic(err)
		}
	} else if !finfo.IsDir() {
		return fmt.Errorf("\"%s\" exists, but it's not a folder", Workdir)
	}
	return nil
}

func updateIfStale(filename string, mode os.FileMode) error {
	sourceFile := AcmeDir + "/" + filename
	destFile := Workdir + "/" + filename
	result, err := cmpModTime(sourceFile, destFile)
	if result > 0 {
		err = CopyFile(sourceFile, destFile, mode)
		if err == nil {
			klog.Infof("Updated \"%s\" from \"%s\" folder", destFile, AcmeDir)
		}
	}
	return err
}

func cmpModTime(file1 string, file2 string) (int, error) {
	// Get the fileinfo
	fileInfo, err := os.Stat(file1)
	if err != nil {
		klog.Fatal(err)
	}
	modtime1 := fileInfo.ModTime()
	fileInfo, err = os.Stat(file2)
	// if file2 does not exist, return as if file1.modtime > file2.modtime
	if os.IsNotExist(err) {
		return 1, nil
	}
	// for any other error, return fatal err
	if err != nil {
		klog.Fatal(err)
	}
	modtime2 := fileInfo.ModTime()
	diff := modtime1.Sub(modtime2)
	if diff < (time.Duration(0) * time.Second) {
		return -1, nil
	}
	if diff > (time.Duration(0) * time.Second) {
		return 1, nil
	}
	return 0, nil
}

func CopyFile(sourceFile string, destFile string, mode os.FileMode) error {
	source, err := os.Open(sourceFile) //open the source file
	if err != nil {
		panic(err)
	}
	defer source.Close()

	destination, err := os.Create(destFile) //create the destination file
	if err != nil {
		panic(err)
	}
	defer destination.Close()
	_, err = io.Copy(destination, source) //copy the contents of source to destination file
	if err != nil {
		panic(err)
	}
	err = os.Chmod(destFile, mode)
	//klog.Infof("Copied %s to %s.", sourceFile, destFile)
	return err
}