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acme.go
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acme.go
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// Package acme provides a means of performing Let's Encrypt DNS challenges via a DNSConfig
package acme
import (
"crypto/x509"
"encoding/json"
"encoding/pem"
"fmt"
"io/ioutil"
"log"
"net/url"
"os"
"path/filepath"
"sort"
"strings"
"time"
"github.com/StackExchange/dnscontrol/models"
"github.com/StackExchange/dnscontrol/pkg/nameservers"
"github.com/xenolf/lego/acmev2"
)
type CertConfig struct {
CertName string `json:"cert_name"`
Names []string `json:"names"`
}
type Client interface {
IssueOrRenewCert(config *CertConfig, renewUnder int, verbose bool) (bool, error)
}
type certManager struct {
directory string
email string
acmeDirectory string
acmeHost string
cfg *models.DNSConfig
checkedDomains map[string]bool
account *account
client *acme.Client
}
const (
LetsEncryptLive = "https://acme-v02.api.letsencrypt.org/directory"
LetsEncryptStage = "https://acme-staging-v02.api.letsencrypt.org/directory"
)
func New(cfg *models.DNSConfig, directory string, email string, server string) (Client, error) {
u, err := url.Parse(server)
if err != nil || u.Host == "" {
return nil, fmt.Errorf("ACME directory '%s' is not a valid URL", server)
}
c := &certManager{
directory: directory,
email: email,
acmeDirectory: server,
acmeHost: u.Host,
cfg: cfg,
checkedDomains: map[string]bool{},
}
if err := c.loadOrCreateAccount(); err != nil {
return nil, err
}
c.client.ExcludeChallenges([]acme.Challenge{acme.HTTP01})
c.client.SetChallengeProvider(acme.DNS01, c)
return c, nil
}
// IssueOrRenewCert will obtain a certificate with the given name if it does not exist,
// or renew it if it is close enough to the expiration date.
// It will return true if it issued or updated the certificate.
func (c *certManager) IssueOrRenewCert(cfg *CertConfig, renewUnder int, verbose bool) (bool, error) {
if !verbose {
acme.Logger = log.New(ioutil.Discard, "", 0)
}
log.Printf("Checking certificate [%s]", cfg.CertName)
if err := os.MkdirAll(filepath.Dir(c.certFile(cfg.CertName, "json")), dirPerms); err != nil {
return false, err
}
existing, err := c.readCertificate(cfg.CertName)
if err != nil {
return false, err
}
var action = func() (acme.CertificateResource, error) {
return c.client.ObtainCertificate(cfg.Names, true, nil, true)
}
if existing == nil {
log.Println("No existing cert found. Issuing new...")
} else {
names, daysLeft, err := getCertInfo(existing.Certificate)
if err != nil {
return false, err
}
log.Printf("Found existing cert. %0.2f days remaining.", daysLeft)
namesOK := dnsNamesEqual(cfg.Names, names)
if daysLeft >= float64(renewUnder) && namesOK {
log.Println("Nothing to do")
//nothing to do
return false, nil
}
if !namesOK {
log.Println("DNS Names don't match expected set. Reissuing.")
} else {
log.Println("Renewing cert")
action = func() (acme.CertificateResource, error) {
return c.client.RenewCertificate(*existing, true, true)
}
}
}
certResource, err := action()
if err != nil {
return false, err
}
fmt.Printf("Obtained certificate for %s\n", cfg.CertName)
return true, c.writeCertificate(cfg.CertName, &certResource)
}
// filename for certifiacte / key / json file
func (c *certManager) certFile(name, ext string) string {
return filepath.Join(c.directory, "certificates", name, name+"."+ext)
}
func (c *certManager) writeCertificate(name string, cr *acme.CertificateResource) error {
jDAt, err := json.MarshalIndent(cr, "", " ")
if err != nil {
return err
}
if err = ioutil.WriteFile(c.certFile(name, "json"), jDAt, perms); err != nil {
return err
}
if err = ioutil.WriteFile(c.certFile(name, "crt"), cr.Certificate, perms); err != nil {
return err
}
return ioutil.WriteFile(c.certFile(name, "key"), cr.PrivateKey, perms)
}
func getCertInfo(pemBytes []byte) (names []string, remaining float64, err error) {
block, _ := pem.Decode(pemBytes)
if block == nil {
return nil, 0, fmt.Errorf("Invalid certificate pem data")
}
cert, err := x509.ParseCertificate(block.Bytes)
if err != nil {
return nil, 0, err
}
var daysLeft = float64(cert.NotAfter.Sub(time.Now())) / float64(time.Hour*24)
return cert.DNSNames, daysLeft, nil
}
// checks two lists of sans to make sure they have all the same names in them.
func dnsNamesEqual(a []string, b []string) bool {
if len(a) != len(b) {
return false
}
sort.Strings(a)
sort.Strings(b)
for i, s := range a {
if b[i] != s {
return false
}
}
return true
}
func (c *certManager) readCertificate(name string) (*acme.CertificateResource, error) {
f, err := os.Open(c.certFile(name, "json"))
if err != nil && os.IsNotExist(err) {
// if json does not exist, nothing does
return nil, nil
}
if err != nil {
return nil, err
}
defer f.Close()
dec := json.NewDecoder(f)
cr := &acme.CertificateResource{}
if err = dec.Decode(cr); err != nil {
return nil, err
}
// load cert
crtBytes, err := ioutil.ReadFile(c.certFile(name, "crt"))
if err != nil {
return nil, err
}
cr.Certificate = crtBytes
return cr, nil
}
func (c *certManager) Present(domain, token, keyAuth string) (e error) {
d := c.cfg.DomainContainingFQDN(domain)
// fix NS records for this domain's DNS providers
// only need to do this once per domain
const metaKey = "x-fixed-nameservers"
if d.Metadata[metaKey] == "" {
nsList, err := nameservers.DetermineNameservers(d)
if err != nil {
return err
}
d.Nameservers = nsList
nameservers.AddNSRecords(d)
d.Metadata[metaKey] = "true"
}
// copy now so we can add txt record safely, and just run unmodified version later to cleanup
d, err := d.Copy()
if err != nil {
return err
}
if err := c.ensureNoPendingCorrections(d); err != nil {
return err
}
fqdn, val, _ := acme.DNS01Record(domain, keyAuth)
fmt.Println(fqdn, val)
txt := &models.RecordConfig{Type: "TXT"}
txt.SetTargetTXT(val)
txt.SetLabelFromFQDN(fqdn, d.Name)
d.Records = append(d.Records, txt)
return getAndRunCorrections(d)
}
func (c *certManager) ensureNoPendingCorrections(d *models.DomainConfig) error {
// only need to check a domain once per app run
if c.checkedDomains[d.Name] {
return nil
}
corrections, err := getCorrections(d)
if err != nil {
return err
}
if len(corrections) != 0 {
// TODO: maybe allow forcing through this check.
for _, c := range corrections {
fmt.Println(c.Msg)
}
return fmt.Errorf("Found %d pending corrections for %s. Not going to proceed issuing certificates", len(corrections), d.Name)
}
return nil
}
// IgnoredProviders is a lit of provider names that should not be used to fill challenges.
var IgnoredProviders = map[string]bool{}
func getCorrections(d *models.DomainConfig) ([]*models.Correction, error) {
cs := []*models.Correction{}
for _, p := range d.DNSProviderInstances {
if IgnoredProviders[p.Name] {
continue
}
dc, err := d.Copy()
if err != nil {
return nil, err
}
corrections, err := p.Driver.GetDomainCorrections(dc)
if err != nil {
return nil, err
}
for _, c := range corrections {
c.Msg = fmt.Sprintf("[%s] %s", p.Name, strings.TrimSpace(c.Msg))
}
cs = append(cs, corrections...)
}
return cs, nil
}
func getAndRunCorrections(d *models.DomainConfig) error {
cs, err := getCorrections(d)
if err != nil {
return err
}
fmt.Printf("%d corrections\n", len(cs))
for _, c := range cs {
fmt.Printf("Running [%s]\n", c.Msg)
err = c.F()
if err != nil {
return err
}
}
return nil
}
func (c *certManager) CleanUp(domain, token, keyAuth string) error {
d := c.cfg.DomainContainingFQDN(domain)
return getAndRunCorrections(d)
}