Update vendor

vendor/golang.org/x/crypto/acme/autocert/autocert.go

@@ -0,0 +1,793 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package autocert provides automatic access to certificates from Let's Encrypt
+// and any other ACME-based CA.
+//
+// This package is a work in progress and makes no API stability promises.
+package autocert
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io"
+	mathrand "math/rand"
+	"net/http"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/crypto/acme"
+	"golang.org/x/net/context"
+)
+
+// pseudoRand is safe for concurrent use.
+var pseudoRand *lockedMathRand
+
+func init() {
+	src := mathrand.NewSource(timeNow().UnixNano())
+	pseudoRand = &lockedMathRand{rnd: mathrand.New(src)}
+}
+
+// AcceptTOS always returns true to indicate the acceptance of a CA Terms of Service
+// during account registration.
+func AcceptTOS(tosURL string) bool { return true }
+
+// HostPolicy specifies which host names the Manager is allowed to respond to.
+// It returns a non-nil error if the host should be rejected.
+// The returned error is accessible via tls.Conn.Handshake and its callers.
+// See Manager's HostPolicy field and GetCertificate method docs for more details.
+type HostPolicy func(ctx context.Context, host string) error
+
+// HostWhitelist returns a policy where only the specified host names are allowed.
+// Only exact matches are currently supported. Subdomains, regexp or wildcard
+// will not match.
+func HostWhitelist(hosts ...string) HostPolicy {
+	whitelist := make(map[string]bool, len(hosts))
+	for _, h := range hosts {
+		whitelist[h] = true
+	}
+	return func(_ context.Context, host string) error {
+		if !whitelist[host] {
+			return errors.New("acme/autocert: host not configured")
+		}
+		return nil
+	}
+}
+
+// defaultHostPolicy is used when Manager.HostPolicy is not set.
+func defaultHostPolicy(context.Context, string) error {
+	return nil
+}
+
+// Manager is a stateful certificate manager built on top of acme.Client.
+// It obtains and refreshes certificates automatically,
+// as well as providing them to a TLS server via tls.Config.
+//
+// A simple usage example:
+//
+//	m := autocert.Manager{
+//		Prompt: autocert.AcceptTOS,
+//		HostPolicy: autocert.HostWhitelist("example.org"),
+//	}
+//	s := &http.Server{
+//		Addr: ":https",
+//		TLSConfig: &tls.Config{GetCertificate: m.GetCertificate},
+//	}
+//	s.ListenAndServeTLS("", "")
+//
+// To preserve issued certificates and improve overall performance,
+// use a cache implementation of Cache. For instance, DirCache.
+type Manager struct {
+	// Prompt specifies a callback function to conditionally accept a CA's Terms of Service (TOS).
+	// The registration may require the caller to agree to the CA's TOS.
+	// If so, Manager calls Prompt with a TOS URL provided by the CA. Prompt should report
+	// whether the caller agrees to the terms.
+	//
+	// To always accept the terms, the callers can use AcceptTOS.
+	Prompt func(tosURL string) bool
+
+	// Cache optionally stores and retrieves previously-obtained certificates.
+	// If nil, certs will only be cached for the lifetime of the Manager.
+	//
+	// Manager passes the Cache certificates data encoded in PEM, with private/public
+	// parts combined in a single Cache.Put call, private key first.
+	Cache Cache
+
+	// HostPolicy controls which domains the Manager will attempt
+	// to retrieve new certificates for. It does not affect cached certs.
+	//
+	// If non-nil, HostPolicy is called before requesting a new cert.
+	// If nil, all hosts are currently allowed. This is not recommended,
+	// as it opens a potential attack where clients connect to a server
+	// by IP address and pretend to be asking for an incorrect host name.
+	// Manager will attempt to obtain a certificate for that host, incorrectly,
+	// eventually reaching the CA's rate limit for certificate requests
+	// and making it impossible to obtain actual certificates.
+	//
+	// See GetCertificate for more details.
+	HostPolicy HostPolicy
+
+	// RenewBefore optionally specifies how early certificates should
+	// be renewed before they expire.
+	//
+	// If zero, they're renewed 1 week before expiration.
+	RenewBefore time.Duration
+
+	// Client is used to perform low-level operations, such as account registration
+	// and requesting new certificates.
+	// If Client is nil, a zero-value acme.Client is used with acme.LetsEncryptURL
+	// directory endpoint and a newly-generated ECDSA P-256 key.
+	//
+	// Mutating the field after the first call of GetCertificate method will have no effect.
+	Client *acme.Client
+
+	// Email optionally specifies a contact email address.
+	// This is used by CAs, such as Let's Encrypt, to notify about problems
+	// with issued certificates.
+	//
+	// If the Client's account key is already registered, Email is not used.
+	Email string
+
+	// ForceRSA makes the Manager generate certificates with 2048-bit RSA keys.
+	//
+	// If false, a default is used. Currently the default
+	// is EC-based keys using the P-256 curve.
+	ForceRSA bool
+
+	clientMu sync.Mutex
+	client   *acme.Client // initialized by acmeClient method
+
+	stateMu sync.Mutex
+	state   map[string]*certState // keyed by domain name
+
+	// tokenCert is keyed by token domain name, which matches server name
+	// of ClientHello. Keys always have ".acme.invalid" suffix.
+	tokenCertMu sync.RWMutex
+	tokenCert   map[string]*tls.Certificate
+
+	// renewal tracks the set of domains currently running renewal timers.
+	// It is keyed by domain name.
+	renewalMu sync.Mutex
+	renewal   map[string]*domainRenewal
+}
+
+// GetCertificate implements the tls.Config.GetCertificate hook.
+// It provides a TLS certificate for hello.ServerName host, including answering
+// *.acme.invalid (TLS-SNI) challenges. All other fields of hello are ignored.
+//
+// If m.HostPolicy is non-nil, GetCertificate calls the policy before requesting
+// a new cert. A non-nil error returned from m.HostPolicy halts TLS negotiation.
+// The error is propagated back to the caller of GetCertificate and is user-visible.
+// This does not affect cached certs. See HostPolicy field description for more details.
+func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
+	name := hello.ServerName
+	if name == "" {
+		return nil, errors.New("acme/autocert: missing server name")
+	}
+
+	// check whether this is a token cert requested for TLS-SNI challenge
+	if strings.HasSuffix(name, ".acme.invalid") {
+		m.tokenCertMu.RLock()
+		defer m.tokenCertMu.RUnlock()
+		if cert := m.tokenCert[name]; cert != nil {
+			return cert, nil
+		}
+		if cert, err := m.cacheGet(name); err == nil {
+			return cert, nil
+		}
+		// TODO: cache error results?
+		return nil, fmt.Errorf("acme/autocert: no token cert for %q", name)
+	}
+
+	// regular domain
+	name = strings.TrimSuffix(name, ".") // golang.org/issue/18114
+	cert, err := m.cert(name)
+	if err == nil {
+		return cert, nil
+	}
+	if err != ErrCacheMiss {
+		return nil, err
+	}
+
+	// first-time
+	ctx := context.Background() // TODO: use a deadline?
+	if err := m.hostPolicy()(ctx, name); err != nil {
+		return nil, err
+	}
+	cert, err = m.createCert(ctx, name)
+	if err != nil {
+		return nil, err
+	}
+	m.cachePut(name, cert)
+	return cert, nil
+}
+
+// cert returns an existing certificate either from m.state or cache.
+// If a certificate is found in cache but not in m.state, the latter will be filled
+// with the cached value.
+func (m *Manager) cert(name string) (*tls.Certificate, error) {
+	m.stateMu.Lock()
+	if s, ok := m.state[name]; ok {
+		m.stateMu.Unlock()
+		s.RLock()
+		defer s.RUnlock()
+		return s.tlscert()
+	}
+	defer m.stateMu.Unlock()
+	cert, err := m.cacheGet(name)
+	if err != nil {
+		return nil, err
+	}
+	signer, ok := cert.PrivateKey.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("acme/autocert: private key cannot sign")
+	}
+	if m.state == nil {
+		m.state = make(map[string]*certState)
+	}
+	s := &certState{
+		key:  signer,
+		cert: cert.Certificate,
+		leaf: cert.Leaf,
+	}
+	m.state[name] = s
+	go m.renew(name, s.key, s.leaf.NotAfter)
+	return cert, nil
+}
+
+// cacheGet always returns a valid certificate, or an error otherwise.
+func (m *Manager) cacheGet(domain string) (*tls.Certificate, error) {
+	if m.Cache == nil {
+		return nil, ErrCacheMiss
+	}
+	// TODO: might want to define a cache timeout on m
+	ctx := context.Background()
+	data, err := m.Cache.Get(ctx, domain)
+	if err != nil {
+		return nil, err
+	}
+
+	// private
+	priv, pub := pem.Decode(data)
+	if priv == nil || !strings.Contains(priv.Type, "PRIVATE") {
+		return nil, errors.New("acme/autocert: no private key found in cache")
+	}
+	privKey, err := parsePrivateKey(priv.Bytes)
+	if err != nil {
+		return nil, err
+	}
+
+	// public
+	var pubDER [][]byte
+	for len(pub) > 0 {
+		var b *pem.Block
+		b, pub = pem.Decode(pub)
+		if b == nil {
+			break
+		}
+		pubDER = append(pubDER, b.Bytes)
+	}
+	if len(pub) > 0 {
+		return nil, errors.New("acme/autocert: invalid public key")
+	}
+
+	// verify and create TLS cert
+	leaf, err := validCert(domain, pubDER, privKey)
+	if err != nil {
+		return nil, err
+	}
+	tlscert := &tls.Certificate{
+		Certificate: pubDER,
+		PrivateKey:  privKey,
+		Leaf:        leaf,
+	}
+	return tlscert, nil
+}
+
+func (m *Manager) cachePut(domain string, tlscert *tls.Certificate) error {
+	if m.Cache == nil {
+		return nil
+	}
+
+	// contains PEM-encoded data
+	var buf bytes.Buffer
+
+	// private
+	switch key := tlscert.PrivateKey.(type) {
+	case *ecdsa.PrivateKey:
+		if err := encodeECDSAKey(&buf, key); err != nil {
+			return err
+		}
+	case *rsa.PrivateKey:
+		b := x509.MarshalPKCS1PrivateKey(key)
+		pb := &pem.Block{Type: "RSA PRIVATE KEY", Bytes: b}
+		if err := pem.Encode(&buf, pb); err != nil {
+			return err
+		}
+	default:
+		return errors.New("acme/autocert: unknown private key type")
+	}
+
+	// public
+	for _, b := range tlscert.Certificate {
+		pb := &pem.Block{Type: "CERTIFICATE", Bytes: b}
+		if err := pem.Encode(&buf, pb); err != nil {
+			return err
+		}
+	}
+
+	// TODO: might want to define a cache timeout on m
+	ctx := context.Background()
+	return m.Cache.Put(ctx, domain, buf.Bytes())
+}
+
+func encodeECDSAKey(w io.Writer, key *ecdsa.PrivateKey) error {
+	b, err := x509.MarshalECPrivateKey(key)
+	if err != nil {
+		return err
+	}
+	pb := &pem.Block{Type: "EC PRIVATE KEY", Bytes: b}
+	return pem.Encode(w, pb)
+}
+
+// createCert starts the domain ownership verification and returns a certificate
+// for that domain upon success.
+//
+// If the domain is already being verified, it waits for the existing verification to complete.
+// Either way, createCert blocks for the duration of the whole process.
+func (m *Manager) createCert(ctx context.Context, domain string) (*tls.Certificate, error) {
+	// TODO: maybe rewrite this whole piece using sync.Once
+	state, err := m.certState(domain)
+	if err != nil {
+		return nil, err
+	}
+	// state may exist if another goroutine is already working on it
+	// in which case just wait for it to finish
+	if !state.locked {
+		state.RLock()
+		defer state.RUnlock()
+		return state.tlscert()
+	}
+
+	// We are the first; state is locked.
+	// Unblock the readers when domain ownership is verified
+	// and the we got the cert or the process failed.
+	defer state.Unlock()
+	state.locked = false
+
+	der, leaf, err := m.authorizedCert(ctx, state.key, domain)
+	if err != nil {
+		return nil, err
+	}
+	state.cert = der
+	state.leaf = leaf
+	go m.renew(domain, state.key, state.leaf.NotAfter)
+	return state.tlscert()
+}
+
+// certState returns a new or existing certState.
+// If a new certState is returned, state.exist is false and the state is locked.
+// The returned error is non-nil only in the case where a new state could not be created.
+func (m *Manager) certState(domain string) (*certState, error) {
+	m.stateMu.Lock()
+	defer m.stateMu.Unlock()
+	if m.state == nil {
+		m.state = make(map[string]*certState)
+	}
+	// existing state
+	if state, ok := m.state[domain]; ok {
+		return state, nil
+	}
+
+	// new locked state
+	var (
+		err error
+		key crypto.Signer
+	)
+	if m.ForceRSA {
+		key, err = rsa.GenerateKey(rand.Reader, 2048)
+	} else {
+		key, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	state := &certState{
+		key:    key,
+		locked: true,
+	}
+	state.Lock() // will be unlocked by m.certState caller
+	m.state[domain] = state
+	return state, nil
+}
+
+// authorizedCert starts domain ownership verification process and requests a new cert upon success.
+// The key argument is the certificate private key.
+func (m *Manager) authorizedCert(ctx context.Context, key crypto.Signer, domain string) (der [][]byte, leaf *x509.Certificate, err error) {
+	// TODO: make m.verify retry or retry m.verify calls here
+	if err := m.verify(ctx, domain); err != nil {
+		return nil, nil, err
+	}
+	client, err := m.acmeClient(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+	csr, err := certRequest(key, domain)
+	if err != nil {
+		return nil, nil, err
+	}
+	der, _, err = client.CreateCert(ctx, csr, 0, true)
+	if err != nil {
+		return nil, nil, err
+	}
+	leaf, err = validCert(domain, der, key)
+	if err != nil {
+		return nil, nil, err
+	}
+	return der, leaf, nil
+}
+
+// verify starts a new identifier (domain) authorization flow.
+// It prepares a challenge response and then blocks until the authorization
+// is marked as "completed" by the CA (either succeeded or failed).
+//
+// verify returns nil iff the verification was successful.
+func (m *Manager) verify(ctx context.Context, domain string) error {
+	client, err := m.acmeClient(ctx)
+	if err != nil {
+		return err
+	}
+
+	// start domain authorization and get the challenge
+	authz, err := client.Authorize(ctx, domain)
+	if err != nil {
+		return err
+	}
+	// maybe don't need to at all
+	if authz.Status == acme.StatusValid {
+		return nil
+	}
+
+	// pick a challenge: prefer tls-sni-02 over tls-sni-01
+	// TODO: consider authz.Combinations
+	var chal *acme.Challenge
+	for _, c := range authz.Challenges {
+		if c.Type == "tls-sni-02" {
+			chal = c
+			break
+		}
+		if c.Type == "tls-sni-01" {
+			chal = c
+		}
+	}
+	if chal == nil {
+		return errors.New("acme/autocert: no supported challenge type found")
+	}
+
+	// create a token cert for the challenge response
+	var (
+		cert tls.Certificate
+		name string
+	)
+	switch chal.Type {
+	case "tls-sni-01":
+		cert, name, err = client.TLSSNI01ChallengeCert(chal.Token)
+	case "tls-sni-02":
+		cert, name, err = client.TLSSNI02ChallengeCert(chal.Token)
+	default:
+		err = fmt.Errorf("acme/autocert: unknown challenge type %q", chal.Type)
+	}
+	if err != nil {
+		return err
+	}
+	m.putTokenCert(name, &cert)
+	defer func() {
+		// verification has ended at this point
+		// don't need token cert anymore
+		go m.deleteTokenCert(name)
+	}()
+
+	// ready to fulfill the challenge
+	if _, err := client.Accept(ctx, chal); err != nil {
+		return err
+	}
+	// wait for the CA to validate
+	_, err = client.WaitAuthorization(ctx, authz.URI)
+	return err
+}
+
+// putTokenCert stores the cert under the named key in both m.tokenCert map
+// and m.Cache.
+func (m *Manager) putTokenCert(name string, cert *tls.Certificate) {
+	m.tokenCertMu.Lock()
+	defer m.tokenCertMu.Unlock()
+	if m.tokenCert == nil {
+		m.tokenCert = make(map[string]*tls.Certificate)
+	}
+	m.tokenCert[name] = cert
+	m.cachePut(name, cert)
+}
+
+// deleteTokenCert removes the token certificate for the specified domain name
+// from both m.tokenCert map and m.Cache.
+func (m *Manager) deleteTokenCert(name string) {
+	m.tokenCertMu.Lock()
+	defer m.tokenCertMu.Unlock()
+	delete(m.tokenCert, name)
+	if m.Cache != nil {
+		m.Cache.Delete(context.Background(), name)
+	}
+}
+
+// renew starts a cert renewal timer loop, one per domain.
+//
+// The loop is scheduled in two cases:
+// - a cert was fetched from cache for the first time (wasn't in m.state)
+// - a new cert was created by m.createCert
+//
+// The key argument is a certificate private key.
+// The exp argument is the cert expiration time (NotAfter).
+func (m *Manager) renew(domain string, key crypto.Signer, exp time.Time) {
+	m.renewalMu.Lock()
+	defer m.renewalMu.Unlock()
+	if m.renewal[domain] != nil {
+		// another goroutine is already on it
+		return
+	}
+	if m.renewal == nil {
+		m.renewal = make(map[string]*domainRenewal)
+	}
+	dr := &domainRenewal{m: m, domain: domain, key: key}
+	m.renewal[domain] = dr
+	dr.start(exp)
+}
+
+// stopRenew stops all currently running cert renewal timers.
+// The timers are not restarted during the lifetime of the Manager.
+func (m *Manager) stopRenew() {
+	m.renewalMu.Lock()
+	defer m.renewalMu.Unlock()
+	for name, dr := range m.renewal {
+		delete(m.renewal, name)
+		dr.stop()
+	}
+}
+
+func (m *Manager) accountKey(ctx context.Context) (crypto.Signer, error) {
+	const keyName = "acme_account.key"
+
+	genKey := func() (*ecdsa.PrivateKey, error) {
+		return ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	}
+
+	if m.Cache == nil {
+		return genKey()
+	}
+
+	data, err := m.Cache.Get(ctx, keyName)
+	if err == ErrCacheMiss {
+		key, err := genKey()
+		if err != nil {
+			return nil, err
+		}
+		var buf bytes.Buffer
+		if err := encodeECDSAKey(&buf, key); err != nil {
+			return nil, err
+		}
+		if err := m.Cache.Put(ctx, keyName, buf.Bytes()); err != nil {
+			return nil, err
+		}
+		return key, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	priv, _ := pem.Decode(data)
+	if priv == nil || !strings.Contains(priv.Type, "PRIVATE") {
+		return nil, errors.New("acme/autocert: invalid account key found in cache")
+	}
+	return parsePrivateKey(priv.Bytes)
+}
+
+func (m *Manager) acmeClient(ctx context.Context) (*acme.Client, error) {
+	m.clientMu.Lock()
+	defer m.clientMu.Unlock()
+	if m.client != nil {
+		return m.client, nil
+	}
+
+	client := m.Client
+	if client == nil {
+		client = &acme.Client{DirectoryURL: acme.LetsEncryptURL}
+	}
+	if client.Key == nil {
+		var err error
+		client.Key, err = m.accountKey(ctx)
+		if err != nil {
+			return nil, err
+		}
+	}
+	var contact []string
+	if m.Email != "" {
+		contact = []string{"mailto:" + m.Email}
+	}
+	a := &acme.Account{Contact: contact}
+	_, err := client.Register(ctx, a, m.Prompt)
+	if ae, ok := err.(*acme.Error); err == nil || ok && ae.StatusCode == http.StatusConflict {
+		// conflict indicates the key is already registered
+		m.client = client
+		err = nil
+	}
+	return m.client, err
+}
+
+func (m *Manager) hostPolicy() HostPolicy {
+	if m.HostPolicy != nil {
+		return m.HostPolicy
+	}
+	return defaultHostPolicy
+}
+
+func (m *Manager) renewBefore() time.Duration {
+	if m.RenewBefore > maxRandRenew {
+		return m.RenewBefore
+	}
+	return 7 * 24 * time.Hour // 1 week
+}
+
+// certState is ready when its mutex is unlocked for reading.
+type certState struct {
+	sync.RWMutex
+	locked bool              // locked for read/write
+	key    crypto.Signer     // private key for cert
+	cert   [][]byte          // DER encoding
+	leaf   *x509.Certificate // parsed cert[0]; always non-nil if cert != nil
+}
+
+// tlscert creates a tls.Certificate from s.key and s.cert.
+// Callers should wrap it in s.RLock() and s.RUnlock().
+func (s *certState) tlscert() (*tls.Certificate, error) {
+	if s.key == nil {
+		return nil, errors.New("acme/autocert: missing signer")
+	}
+	if len(s.cert) == 0 {
+		return nil, errors.New("acme/autocert: missing certificate")
+	}
+	return &tls.Certificate{
+		PrivateKey:  s.key,
+		Certificate: s.cert,
+		Leaf:        s.leaf,
+	}, nil
+}
+
+// certRequest creates a certificate request for the given common name cn
+// and optional SANs.
+func certRequest(key crypto.Signer, cn string, san ...string) ([]byte, error) {
+	req := &x509.CertificateRequest{
+		Subject:  pkix.Name{CommonName: cn},
+		DNSNames: san,
+	}
+	return x509.CreateCertificateRequest(rand.Reader, req, key)
+}
+
+// Attempt to parse the given private key DER block. OpenSSL 0.9.8 generates
+// PKCS#1 private keys by default, while OpenSSL 1.0.0 generates PKCS#8 keys.
+// OpenSSL ecparam generates SEC1 EC private keys for ECDSA. We try all three.
+//
+// Inspired by parsePrivateKey in crypto/tls/tls.go.
+func parsePrivateKey(der []byte) (crypto.Signer, error) {
+	if key, err := x509.ParsePKCS1PrivateKey(der); err == nil {
+		return key, nil
+	}
+	if key, err := x509.ParsePKCS8PrivateKey(der); err == nil {
+		switch key := key.(type) {
+		case *rsa.PrivateKey:
+			return key, nil
+		case *ecdsa.PrivateKey:
+			return key, nil
+		default:
+			return nil, errors.New("acme/autocert: unknown private key type in PKCS#8 wrapping")
+		}
+	}
+	if key, err := x509.ParseECPrivateKey(der); err == nil {
+		return key, nil
+	}
+
+	return nil, errors.New("acme/autocert: failed to parse private key")
+}
+
+// validCert parses a cert chain provided as der argument and verifies the leaf, der[0],
+// corresponds to the private key, as well as the domain match and expiration dates.
+// It doesn't do any revocation checking.
+//
+// The returned value is the verified leaf cert.
+func validCert(domain string, der [][]byte, key crypto.Signer) (leaf *x509.Certificate, err error) {
+	// parse public part(s)
+	var n int
+	for _, b := range der {
+		n += len(b)
+	}
+	pub := make([]byte, n)
+	n = 0
+	for _, b := range der {
+		n += copy(pub[n:], b)
+	}
+	x509Cert, err := x509.ParseCertificates(pub)
+	if len(x509Cert) == 0 {
+		return nil, errors.New("acme/autocert: no public key found")
+	}
+	// verify the leaf is not expired and matches the domain name
+	leaf = x509Cert[0]
+	now := timeNow()
+	if now.Before(leaf.NotBefore) {
+		return nil, errors.New("acme/autocert: certificate is not valid yet")
+	}
+	if now.After(leaf.NotAfter) {
+		return nil, errors.New("acme/autocert: expired certificate")
+	}
+	if err := leaf.VerifyHostname(domain); err != nil {
+		return nil, err
+	}
+	// ensure the leaf corresponds to the private key
+	switch pub := leaf.PublicKey.(type) {
+	case *rsa.PublicKey:
+		prv, ok := key.(*rsa.PrivateKey)
+		if !ok {
+			return nil, errors.New("acme/autocert: private key type does not match public key type")
+		}
+		if pub.N.Cmp(prv.N) != 0 {
+			return nil, errors.New("acme/autocert: private key does not match public key")
+		}
+	case *ecdsa.PublicKey:
+		prv, ok := key.(*ecdsa.PrivateKey)
+		if !ok {
+			return nil, errors.New("acme/autocert: private key type does not match public key type")
+		}
+		if pub.X.Cmp(prv.X) != 0 || pub.Y.Cmp(prv.Y) != 0 {
+			return nil, errors.New("acme/autocert: private key does not match public key")
+		}
+	default:
+		return nil, errors.New("acme/autocert: unknown public key algorithm")
+	}
+	return leaf, nil
+}
+
+func retryAfter(v string) time.Duration {
+	if i, err := strconv.Atoi(v); err == nil {
+		return time.Duration(i) * time.Second
+	}
+	if t, err := http.ParseTime(v); err == nil {
+		return t.Sub(timeNow())
+	}
+	return time.Second
+}
+
+type lockedMathRand struct {
+	sync.Mutex
+	rnd *mathrand.Rand
+}
+
+func (r *lockedMathRand) int63n(max int64) int64 {
+	r.Lock()
+	n := r.rnd.Int63n(max)
+	r.Unlock()
+	return n
+}
+
+// for easier testing
+var timeNow = time.Now

vendor/golang.org/x/crypto/acme/autocert/cache.go

@@ -0,0 +1,130 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package autocert
+
+import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"golang.org/x/net/context"
+)
+
+// ErrCacheMiss is returned when a certificate is not found in cache.
+var ErrCacheMiss = errors.New("acme/autocert: certificate cache miss")
+
+// Cache is used by Manager to store and retrieve previously obtained certificates
+// as opaque data.
+//
+// The key argument of the methods refers to a domain name but need not be an FQDN.
+// Cache implementations should not rely on the key naming pattern.
+type Cache interface {
+	// Get returns a certificate data for the specified key.
+	// If there's no such key, Get returns ErrCacheMiss.
+	Get(ctx context.Context, key string) ([]byte, error)
+
+	// Put stores the data in the cache under the specified key.
+	// Underlying implementations may use any data storage format,
+	// as long as the reverse operation, Get, results in the original data.
+	Put(ctx context.Context, key string, data []byte) error
+
+	// Delete removes a certificate data from the cache under the specified key.
+	// If there's no such key in the cache, Delete returns nil.
+	Delete(ctx context.Context, key string) error
+}
+
+// DirCache implements Cache using a directory on the local filesystem.
+// If the directory does not exist, it will be created with 0700 permissions.
+type DirCache string
+
+// Get reads a certificate data from the specified file name.
+func (d DirCache) Get(ctx context.Context, name string) ([]byte, error) {
+	name = filepath.Join(string(d), name)
+	var (
+		data []byte
+		err  error
+		done = make(chan struct{})
+	)
+	go func() {
+		data, err = ioutil.ReadFile(name)
+		close(done)
+	}()
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case <-done:
+	}
+	if os.IsNotExist(err) {
+		return nil, ErrCacheMiss
+	}
+	return data, err
+}
+
+// Put writes the certificate data to the specified file name.
+// The file will be created with 0600 permissions.
+func (d DirCache) Put(ctx context.Context, name string, data []byte) error {
+	if err := os.MkdirAll(string(d), 0700); err != nil {
+		return err
+	}
+
+	done := make(chan struct{})
+	var err error
+	go func() {
+		defer close(done)
+		var tmp string
+		if tmp, err = d.writeTempFile(name, data); err != nil {
+			return
+		}
+		// prevent overwriting the file if the context was cancelled
+		if ctx.Err() != nil {
+			return // no need to set err
+		}
+		name = filepath.Join(string(d), name)
+		err = os.Rename(tmp, name)
+	}()
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-done:
+	}
+	return err
+}
+
+// Delete removes the specified file name.
+func (d DirCache) Delete(ctx context.Context, name string) error {
+	name = filepath.Join(string(d), name)
+	var (
+		err  error
+		done = make(chan struct{})
+	)
+	go func() {
+		err = os.Remove(name)
+		close(done)
+	}()
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-done:
+	}
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return nil
+}
+
+// writeTempFile writes b to a temporary file, closes the file and returns its path.
+func (d DirCache) writeTempFile(prefix string, b []byte) (string, error) {
+	// TempFile uses 0600 permissions
+	f, err := ioutil.TempFile(string(d), prefix)
+	if err != nil {
+		return "", err
+	}
+	if _, err := f.Write(b); err != nil {
+		f.Close()
+		return "", err
+	}
+	return f.Name(), f.Close()
+}

vendor/golang.org/x/crypto/acme/autocert/renewal.go

@@ -0,0 +1,125 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package autocert
+
+import (
+	"crypto"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+)
+
+// maxRandRenew is a maximum deviation from Manager.RenewBefore.
+const maxRandRenew = time.Hour
+
+// domainRenewal tracks the state used by the periodic timers
+// renewing a single domain's cert.
+type domainRenewal struct {
+	m      *Manager
+	domain string
+	key    crypto.Signer
+
+	timerMu sync.Mutex
+	timer   *time.Timer
+}
+
+// start starts a cert renewal timer at the time
+// defined by the certificate expiration time exp.
+//
+// If the timer is already started, calling start is a noop.
+func (dr *domainRenewal) start(exp time.Time) {
+	dr.timerMu.Lock()
+	defer dr.timerMu.Unlock()
+	if dr.timer != nil {
+		return
+	}
+	dr.timer = time.AfterFunc(dr.next(exp), dr.renew)
+}
+
+// stop stops the cert renewal timer.
+// If the timer is already stopped, calling stop is a noop.
+func (dr *domainRenewal) stop() {
+	dr.timerMu.Lock()
+	defer dr.timerMu.Unlock()
+	if dr.timer == nil {
+		return
+	}
+	dr.timer.Stop()
+	dr.timer = nil
+}
+
+// renew is called periodically by a timer.
+// The first renew call is kicked off by dr.start.
+func (dr *domainRenewal) renew() {
+	dr.timerMu.Lock()
+	defer dr.timerMu.Unlock()
+	if dr.timer == nil {
+		return
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Minute)
+	defer cancel()
+	// TODO: rotate dr.key at some point?
+	next, err := dr.do(ctx)
+	if err != nil {
+		next = maxRandRenew / 2
+		next += time.Duration(pseudoRand.int63n(int64(next)))
+	}
+	dr.timer = time.AfterFunc(next, dr.renew)
+	testDidRenewLoop(next, err)
+}
+
+// do is similar to Manager.createCert but it doesn't lock a Manager.state item.
+// Instead, it requests a new certificate independently and, upon success,
+// replaces dr.m.state item with a new one and updates cache for the given domain.
+//
+// It may return immediately if the expiration date of the currently cached cert
+// is far enough in the future.
+//
+// The returned value is a time interval after which the renewal should occur again.
+func (dr *domainRenewal) do(ctx context.Context) (time.Duration, error) {
+	// a race is likely unavoidable in a distributed environment
+	// but we try nonetheless
+	if tlscert, err := dr.m.cacheGet(dr.domain); err == nil {
+		next := dr.next(tlscert.Leaf.NotAfter)
+		if next > dr.m.renewBefore()+maxRandRenew {
+			return next, nil
+		}
+	}
+
+	der, leaf, err := dr.m.authorizedCert(ctx, dr.key, dr.domain)
+	if err != nil {
+		return 0, err
+	}
+	state := &certState{
+		key:  dr.key,
+		cert: der,
+		leaf: leaf,
+	}
+	tlscert, err := state.tlscert()
+	if err != nil {
+		return 0, err
+	}
+	dr.m.cachePut(dr.domain, tlscert)
+	dr.m.stateMu.Lock()
+	defer dr.m.stateMu.Unlock()
+	// m.state is guaranteed to be non-nil at this point
+	dr.m.state[dr.domain] = state
+	return dr.next(leaf.NotAfter), nil
+}
+
+func (dr *domainRenewal) next(expiry time.Time) time.Duration {
+	d := expiry.Sub(timeNow()) - dr.m.renewBefore()
+	// add a bit of randomness to renew deadline
+	n := pseudoRand.int63n(int64(maxRandRenew))
+	d -= time.Duration(n)
+	if d < 0 {
+		return 0
+	}
+	return d
+}
+
+var testDidRenewLoop = func(next time.Duration, err error) {}