Vendor letsencrypt packages

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
2016-06-09 17:35:14 -07:00 · 2016-06-09 17:35:14 -07:00 · 1c99939221
commit 1c99939221
parent feddf6cd4e
83 changed files with 19743 additions and 0 deletions
--- a/vendor/rsc.io/letsencrypt/lets.go
+++ b/vendor/rsc.io/letsencrypt/lets.go
@ -0,0 +1,753 @@
+// 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 letsencrypt obtains TLS certificates from LetsEncrypt.org.
+//
+// LetsEncrypt.org is a service that issues free SSL/TLS certificates to servers
+// that can prove control over the given domain's DNS records or
+// the servers pointed at by those records.
+//
+// Quick Start
+//
+// A complete HTTP/HTTPS web server using TLS certificates from LetsEncrypt.org,
+// redirecting all HTTP access to HTTPS, and maintaining TLS certificates in a file
+// letsencrypt.cache across server restarts.
+//
+//	package main
+//
+//	import (
+//		"fmt"
+//		"log"
+//		"net/http"
+//		"rsc.io/letsencrypt"
+//	)
+//
+//	func main() {
+//		http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+//			fmt.Fprintf(w, "Hello, TLS!\n")
+//		})
+//		var m letsencrypt.Manager
+//		if err := m.CacheFile("letsencrypt.cache"); err != nil {
+//			log.Fatal(err)
+//		}
+//		log.Fatal(m.Serve())
+//	}
+//
+// Overview
+//
+// The fundamental type in this package is the Manager, which
+// manages obtaining and refreshing a collection of TLS certificates,
+// typically for use by an HTTPS server.
+// The example above shows the most basic use of a Manager.
+// The use can be customized by calling additional methods of the Manager.
+//
+// Registration
+//
+// A Manager m registers anonymously with LetsEncrypt.org, including agreeing to
+// the letsencrypt.org terms of service, the first time it needs to obtain a certificate.
+// To register with a particular email address and with the option of a
+// prompt for agreement with the terms of service, call m.Register.
+//
+// GetCertificate
+//
+// The Manager's GetCertificate method returns certificates
+// from the Manager's cache, filling the cache by requesting certificates
+// from LetsEncrypt.org. In this way, a server with a tls.Config.GetCertificate
+// set to m.GetCertificate will demand load a certificate for any host name
+// it serves. To force loading of certificates ahead of time, install m.GetCertificate
+// as before but then call m.Cert for each host name.
+//
+// A Manager can only obtain a certificate for a given host name if it can prove
+// control of that host name to LetsEncrypt.org. By default it proves control by
+// answering an HTTPS-based challenge: when
+// the LetsEncrypt.org servers connect to the named host on port 443 (HTTPS),
+// the TLS SNI handshake must use m.GetCertificate to obtain a per-host certificate.
+// The most common way to satisfy this requirement is for the host name to
+// resolve to the IP address of a (single) computer running m.ServeHTTPS,
+// or at least running a Go TLS server with tls.Config.GetCertificate set to m.GetCertificate.
+// However, other configurations are possible. For example, a group of machines
+// could use an implementation of tls.Config.GetCertificate that cached
+// certificates but handled cache misses by making RPCs to a Manager m
+// on an elected leader machine.
+//
+// In typical usage, then, the setting of tls.Config.GetCertificate to m.GetCertificate
+// serves two purposes: it provides certificates to the TLS server for ordinary serving,
+// and it also answers challenges to prove ownership of the domains in order to
+// obtain those certificates.
+//
+// To force the loading of a certificate for a given host into the Manager's cache,
+// use m.Cert.
+//
+// Persistent Storage
+//
+// If a server always starts with a zero Manager m, the server effectively fetches
+// a new certificate for each of its host name from LetsEncrypt.org on each restart.
+// This is unfortunate both because the server cannot start if LetsEncrypt.org is
+// unavailable and because LetsEncrypt.org limits how often it will issue a certificate
+// for a given host name (at time of writing, the limit is 5 per week for a given host name).
+// To save server state proactively to a cache file and to reload the server state from
+// that same file when creating a new manager, call m.CacheFile with the name of
+// the file to use.
+//
+// For alternate storage uses, m.Marshal returns the current state of the Manager
+// as an opaque string, m.Unmarshal sets the state of the Manager using a string
+// previously returned by m.Marshal (usually a different m), and m.Watch returns
+// a channel that receives notifications about state changes.
+//
+// Limits
+//
+// To avoid hitting basic rate limits on LetsEncrypt.org, a given Manager limits all its
+// interactions to at most one request every minute, with an initial allowed burst of
+// 20 requests.
+//
+// By default, if GetCertificate is asked for a certificate it does not have, it will in turn
+// ask LetsEncrypt.org for that certificate. This opens a potential attack where attackers
+// connect to a server by IP address and pretend to be asking for an incorrect host name.
+// Then GetCertificate will attempt to obtain a certificate for that host, incorrectly,
+// eventually hitting LetsEncrypt.org's rate limit for certificate requests and making it
+// impossible to obtain actual certificates. Because servers hold certificates for months
+// at a time, however, an attack would need to be sustained over a time period
+// of at least a month in order to cause real problems.
+//
+// To mitigate this kind of attack, a given Manager limits
+// itself to an average of one certificate request for a new host every three hours,
+// with an initial allowed burst of up to 20 requests.
+// Long-running servers will therefore stay
+// within the LetsEncrypt.org limit of 300 failed requests per month.
+// Certificate refreshes are not subject to this limit.
+//
+// To eliminate the attack entirely, call m.SetHosts to enumerate the exact set
+// of hosts that are allowed in certificate requests.
+//
+// Web Servers
+//
+// The basic requirement for use of a Manager is that there be an HTTPS server
+// running on port 443 and calling m.GetCertificate to obtain TLS certificates.
+// Using standard primitives, the way to do this is:
+//
+//	srv := &http.Server{
+//		Addr: ":https",
+//		TLSConfig: &tls.Config{
+//			GetCertificate: m.GetCertificate,
+//		},
+//	}
+//	srv.ListenAndServeTLS("", "")
+//
+// However, this pattern of serving HTTPS with demand-loaded TLS certificates
+// comes up enough to wrap into a single method m.ServeHTTPS.
+//
+// Similarly, many HTTPS servers prefer to redirect HTTP clients to the HTTPS URLs.
+// That functionality is provided by RedirectHTTP.
+//
+// The combination of serving HTTPS with demand-loaded TLS certificates and
+// serving HTTPS redirects to HTTP clients is provided by m.Serve, as used in
+// the original example above.
+//
+package letsencrypt
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/time/rate"
+
+	"github.com/xenolf/lego/acme"
+)
+
+const letsEncryptURL = "https://acme-v01.api.letsencrypt.org/directory"
+const debug = false
+
+// A Manager m takes care of obtaining and refreshing a collection of TLS certificates
+// obtained by LetsEncrypt.org.
+//  The zero Manager is not yet registered with LetsEncrypt.org and has no TLS certificates
+// but is nonetheless ready for use.
+// See the package comment for an overview of how to use a Manager.
+type Manager struct {
+	mu           sync.Mutex
+	state        state
+	rateLimit    *rate.Limiter
+	newHostLimit *rate.Limiter
+	certCache    map[string]*cacheEntry
+	certTokens   map[string]*tls.Certificate
+	watchChan    chan struct{}
+}
+
+// Serve runs an HTTP/HTTPS web server using TLS certificates obtained by the manager.
+// The HTTP server redirects all requests to the HTTPS server.
+// The HTTPS server obtains TLS certificates as needed and responds to requests
+// by invoking http.DefaultServeMux.
+//
+// Serve does not return unitil the HTTPS server fails to start or else stops.
+// Either way, Serve can only return a non-nil error, never nil.
+func (m *Manager) Serve() error {
+	l, err := net.Listen("tcp", ":http")
+	if err != nil {
+		return err
+	}
+	defer l.Close()
+	go http.Serve(l, http.HandlerFunc(RedirectHTTP))
+
+	return m.ServeHTTPS()
+}
+
+// ServeHTTPS runs an HTTPS web server using TLS certificates obtained by the manager.
+// The HTTPS server obtains TLS certificates as needed and responds to requests
+// by invoking http.DefaultServeMux.
+// ServeHTTPS does not return unitil the HTTPS server fails to start or else stops.
+// Either way, ServeHTTPS can only return a non-nil error, never nil.
+func (m *Manager) ServeHTTPS() error {
+	srv := &http.Server{
+		Addr: ":https",
+		TLSConfig: &tls.Config{
+			GetCertificate: m.GetCertificate,
+		},
+	}
+	return srv.ListenAndServeTLS("", "")
+}
+
+// RedirectHTTP is an HTTP handler (suitable for use with http.HandleFunc)
+// that responds to all requests by redirecting to the same URL served over HTTPS.
+// It should only be invoked for requests received over HTTP.
+func RedirectHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.TLS != nil || r.Host == "" {
+		http.Error(w, "not found", 404)
+	}
+
+	u := r.URL
+	u.Host = r.Host
+	u.Scheme = "https"
+	http.Redirect(w, r, u.String(), 302)
+}
+
+// state is the serializable state for the Manager.
+// It also implements acme.User.
+type state struct {
+	Email string
+	Reg   *acme.RegistrationResource
+	Key   string
+	key   *ecdsa.PrivateKey
+	Hosts []string
+	Certs map[string]stateCert
+}
+
+func (s *state) GetEmail() string                            { return s.Email }
+func (s *state) GetRegistration() *acme.RegistrationResource { return s.Reg }
+func (s *state) GetPrivateKey() crypto.PrivateKey            { return s.key }
+
+type stateCert struct {
+	Cert string
+	Key  string
+}
+
+func (cert stateCert) toTLS() (*tls.Certificate, error) {
+	c, err := tls.X509KeyPair([]byte(cert.Cert), []byte(cert.Key))
+	if err != nil {
+		return nil, err
+	}
+	return &c, err
+}
+
+type cacheEntry struct {
+	host string
+	m    *Manager
+
+	mu         sync.Mutex
+	cert       *tls.Certificate
+	timeout    time.Time
+	refreshing bool
+	err        error
+}
+
+func (m *Manager) init() {
+	m.mu.Lock()
+	if m.certCache == nil {
+		m.rateLimit = rate.NewLimiter(rate.Every(1*time.Minute), 20)
+		m.newHostLimit = rate.NewLimiter(rate.Every(3*time.Hour), 20)
+		m.certCache = map[string]*cacheEntry{}
+		m.certTokens = map[string]*tls.Certificate{}
+		m.watchChan = make(chan struct{}, 1)
+		m.watchChan <- struct{}{}
+	}
+	m.mu.Unlock()
+}
+
+// Watch returns the manager's watch channel,
+// which delivers a notification after every time the
+// manager's state (as exposed by Marshal and Unmarshal) changes.
+// All calls to Watch return the same watch channel.
+//
+// The watch channel includes notifications about changes
+// before the first call to Watch, so that in the pattern below,
+// the range loop executes once immediately, saving
+// the result of setup (along with any background updates that
+// may have raced in quickly).
+//
+//	m := new(letsencrypt.Manager)
+//	setup(m)
+//	go backgroundUpdates(m)
+//	for range m.Watch() {
+//		save(m.Marshal())
+//	}
+//
+func (m *Manager) Watch() <-chan struct{} {
+	m.init()
+	m.updated()
+	return m.watchChan
+}
+
+func (m *Manager) updated() {
+	select {
+	case m.watchChan <- struct{}{}:
+	default:
+	}
+}
+
+func (m *Manager) CacheFile(name string) error {
+	f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE, 0600)
+	if err != nil {
+		return err
+	}
+	f.Close()
+	data, err := ioutil.ReadFile(name)
+	if err != nil {
+		return err
+	}
+	if len(data) > 0 {
+		if err := m.Unmarshal(string(data)); err != nil {
+			return err
+		}
+	}
+	go func() {
+		for range m.Watch() {
+			err := ioutil.WriteFile(name, []byte(m.Marshal()), 0600)
+			if err != nil {
+				log.Printf("writing letsencrypt cache: %v", err)
+			}
+		}
+	}()
+	return nil
+}
+
+// Registered reports whether the manager has registered with letsencrypt.org yet.
+func (m *Manager) Registered() bool {
+	m.init()
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.registered()
+}
+
+func (m *Manager) registered() bool {
+	return m.state.Reg != nil && m.state.Reg.Body.Agreement != ""
+}
+
+// Register registers the manager with letsencrypt.org, using the given email address.
+// Registration may require agreeing to the letsencrypt.org terms of service.
+// If so, Register calls prompt(url) where url is the URL of the terms of service.
+// Prompt should report whether the caller agrees to the terms.
+// A nil prompt func is taken to mean that the user always agrees.
+// The email address is sent to LetsEncrypt.org but otherwise unchecked;
+// it can be omitted by passing the empty string.
+//
+// Calling Register is only required to make sure registration uses a
+// particular email address or to insert an explicit prompt into the
+// registration sequence. If the manager is not registered, it will
+// automatically register with no email address and automatic
+// agreement to the terms of service at the first call to Cert or GetCertificate.
+func (m *Manager) Register(email string, prompt func(string) bool) error {
+	m.init()
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	return m.register(email, prompt)
+}
+
+func (m *Manager) register(email string, prompt func(string) bool) error {
+	if m.registered() {
+		return fmt.Errorf("already registered")
+	}
+	m.state.Email = email
+	if m.state.key == nil {
+		key, err := newKey()
+		if err != nil {
+			return fmt.Errorf("generating key: %v", err)
+		}
+		Key, err := marshalKey(key)
+		if err != nil {
+			return fmt.Errorf("generating key: %v", err)
+		}
+		m.state.key = key
+		m.state.Key = string(Key)
+	}
+
+	c, err := acme.NewClient(letsEncryptURL, &m.state, acme.EC256)
+	if err != nil {
+		return fmt.Errorf("create client: %v", err)
+	}
+	reg, err := c.Register()
+	if err != nil {
+		return fmt.Errorf("register: %v", err)
+	}
+
+	m.state.Reg = reg
+	if reg.Body.Agreement == "" {
+		if prompt != nil && !prompt(reg.TosURL) {
+			return fmt.Errorf("did not agree to TOS")
+		}
+		if err := c.AgreeToTOS(); err != nil {
+			return fmt.Errorf("agreeing to TOS: %v", err)
+		}
+	}
+
+	m.updated()
+
+	return nil
+}
+
+// Marshal returns an encoding of the manager's state,
+// suitable for writing to disk and reloading by calling Unmarshal.
+// The state includes registration status, the configured host list
+// from SetHosts, and all known certificates, including their private
+// cryptographic keys.
+// Consequently, the state should be kept private.
+func (m *Manager) Marshal() string {
+	m.init()
+	js, err := json.MarshalIndent(&m.state, "", "\t")
+	if err != nil {
+		panic("unexpected json.Marshal failure")
+	}
+	return string(js)
+}
+
+// Unmarshal restores the state encoded by a previous call to Marshal
+// (perhaps on a different Manager in a different program).
+func (m *Manager) Unmarshal(enc string) error {
+	m.init()
+	var st state
+	if err := json.Unmarshal([]byte(enc), &st); err != nil {
+		return err
+	}
+	if st.Key != "" {
+		key, err := unmarshalKey(st.Key)
+		if err != nil {
+			return err
+		}
+		st.key = key
+	}
+	m.state = st
+	for host, cert := range m.state.Certs {
+		c, err := cert.toTLS()
+		if err != nil {
+			log.Printf("letsencrypt: ignoring entry for %s: %v", host, err)
+			continue
+		}
+		m.certCache[host] = &cacheEntry{host: host, m: m, cert: c}
+	}
+	m.updated()
+	return nil
+}
+
+// SetHosts sets the manager's list of known host names.
+// If the list is non-nil, the manager will only ever attempt to acquire
+// certificates for host names on the list.
+// If the list is nil, the manager does not restrict the hosts it will
+// ask for certificates for.
+func (m *Manager) SetHosts(hosts []string) {
+	m.init()
+	m.mu.Lock()
+	m.state.Hosts = append(m.state.Hosts[:0], hosts...)
+	m.mu.Unlock()
+	m.updated()
+}
+
+// GetCertificate can be placed a tls.Config's GetCertificate field to make
+// the TLS server use Let's Encrypt certificates.
+// Each time a client connects to the TLS server expecting a new host name,
+// the TLS server's call to GetCertificate will trigger an exchange with the
+// Let's Encrypt servers to obtain that certificate, subject to the manager rate limits.
+//
+// As noted in the Manager's documentation comment,
+// to obtain a certificate for a given host name, that name
+// must resolve to a computer running a TLS server on port 443
+// that obtains TLS SNI certificates by calling m.GetCertificate.
+// In the standard usage, then, installing m.GetCertificate in the tls.Config
+// both automatically provisions the TLS certificates needed for
+// ordinary HTTPS service and answers the challenges from LetsEncrypt.org.
+func (m *Manager) GetCertificate(clientHello *tls.ClientHelloInfo) (*tls.Certificate, error) {
+	m.init()
+
+	host := clientHello.ServerName
+
+	if debug {
+		log.Printf("GetCertificate %s", host)
+	}
+
+	if strings.HasSuffix(host, ".acme.invalid") {
+		m.mu.Lock()
+		cert := m.certTokens[host]
+		m.mu.Unlock()
+		if cert == nil {
+			return nil, fmt.Errorf("unknown host")
+		}
+		return cert, nil
+	}
+
+	return m.Cert(host)
+}
+
+// Cert returns the certificate for the given host name, obtaining a new one if necessary.
+//
+// As noted in the documentation for Manager and for the GetCertificate method,
+// obtaining a certificate requires that m.GetCertificate be associated with host.
+// In most servers, simply starting a TLS server with a configuration referring
+// to m.GetCertificate is sufficient, and Cert need not be called.
+//
+// The main use of Cert is to force the manager to obtain a certificate
+// for a particular host name ahead of time.
+func (m *Manager) Cert(host string) (*tls.Certificate, error) {
+	host = strings.ToLower(host)
+	if debug {
+		log.Printf("Cert %s", host)
+	}
+
+	m.init()
+	m.mu.Lock()
+	if !m.registered() {
+		m.register("", nil)
+	}
+
+	ok := false
+	if m.state.Hosts == nil {
+		ok = true
+	} else {
+		for _, h := range m.state.Hosts {
+			if host == h {
+				ok = true
+				break
+			}
+		}
+	}
+	if !ok {
+		m.mu.Unlock()
+		return nil, fmt.Errorf("unknown host")
+	}
+
+	// Otherwise look in our cert cache.
+	entry, ok := m.certCache[host]
+	if !ok {
+		r := m.rateLimit.Reserve()
+		ok := r.OK()
+		if ok {
+			ok = m.newHostLimit.Allow()
+			if !ok {
+				r.Cancel()
+			}
+		}
+		if !ok {
+			m.mu.Unlock()
+			return nil, fmt.Errorf("rate limited")
+		}
+		entry = &cacheEntry{host: host, m: m}
+		m.certCache[host] = entry
+	}
+	m.mu.Unlock()
+
+	entry.mu.Lock()
+	defer entry.mu.Unlock()
+	entry.init()
+	if entry.err != nil {
+		return nil, entry.err
+	}
+	return entry.cert, nil
+}
+
+func (e *cacheEntry) init() {
+	if e.err != nil && time.Now().Before(e.timeout) {
+		return
+	}
+	if e.cert != nil {
+		if e.timeout.IsZero() {
+			t, err := certRefreshTime(e.cert)
+			if err != nil {
+				e.err = err
+				e.timeout = time.Now().Add(1 * time.Minute)
+				e.cert = nil
+				return
+			}
+			e.timeout = t
+		}
+		if time.Now().After(e.timeout) && !e.refreshing {
+			e.refreshing = true
+			go e.refresh()
+		}
+		return
+	}
+
+	cert, refreshTime, err := e.m.verify(e.host)
+	e.m.mu.Lock()
+	e.m.certCache[e.host] = e
+	e.m.mu.Unlock()
+	e.install(cert, refreshTime, err)
+}
+
+func (e *cacheEntry) install(cert *tls.Certificate, refreshTime time.Time, err error) {
+	e.cert = nil
+	e.timeout = time.Time{}
+	e.err = nil
+
+	if err != nil {
+		e.err = err
+		e.timeout = time.Now().Add(1 * time.Minute)
+		return
+	}
+
+	e.cert = cert
+	e.timeout = refreshTime
+}
+
+func (e *cacheEntry) refresh() {
+	e.m.rateLimit.Wait(context.Background())
+	cert, refreshTime, err := e.m.verify(e.host)
+
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	e.refreshing = false
+	if err == nil {
+		e.install(cert, refreshTime, nil)
+	}
+}
+
+func (m *Manager) verify(host string) (cert *tls.Certificate, refreshTime time.Time, err error) {
+	c, err := acme.NewClient(letsEncryptURL, &m.state, acme.EC256)
+	if err != nil {
+		return
+	}
+	if err = c.SetChallengeProvider(acme.TLSSNI01, tlsProvider{m}); err != nil {
+		return
+	}
+	c.SetChallengeProvider(acme.TLSSNI01, tlsProvider{m})
+	c.ExcludeChallenges([]acme.Challenge{acme.HTTP01})
+	acmeCert, errmap := c.ObtainCertificate([]string{host}, true, nil)
+	if len(errmap) > 0 {
+		if debug {
+			log.Printf("ObtainCertificate %v => %v", host, errmap)
+		}
+		err = fmt.Errorf("%v", errmap)
+		return
+	}
+	entryCert := stateCert{
+		Cert: string(acmeCert.Certificate),
+		Key:  string(acmeCert.PrivateKey),
+	}
+	cert, err = entryCert.toTLS()
+	if err != nil {
+		if debug {
+			log.Printf("ObtainCertificate %v toTLS failure: %v", host, err)
+		}
+		err = err
+		return
+	}
+	if refreshTime, err = certRefreshTime(cert); err != nil {
+		return
+	}
+
+	m.mu.Lock()
+	if m.state.Certs == nil {
+		m.state.Certs = make(map[string]stateCert)
+	}
+	m.state.Certs[host] = entryCert
+	m.mu.Unlock()
+	m.updated()
+
+	return cert, refreshTime, nil
+}
+
+func certRefreshTime(cert *tls.Certificate) (time.Time, error) {
+	xc, err := x509.ParseCertificate(cert.Certificate[0])
+	if err != nil {
+		if debug {
+			log.Printf("ObtainCertificate to X.509 failure: %v", err)
+		}
+		return time.Time{}, err
+	}
+	t := xc.NotBefore.Add(xc.NotAfter.Sub(xc.NotBefore) / 2)
+	monthEarly := xc.NotAfter.Add(-30 * 24 * time.Hour)
+	if t.Before(monthEarly) {
+		t = monthEarly
+	}
+	return t, nil
+}
+
+// tlsProvider implements acme.ChallengeProvider for TLS handshake challenges.
+type tlsProvider struct {
+	m *Manager
+}
+
+func (p tlsProvider) Present(domain, token, keyAuth string) error {
+	cert, dom, err := acme.TLSSNI01ChallengeCertDomain(keyAuth)
+	if err != nil {
+		return err
+	}
+
+	p.m.mu.Lock()
+	p.m.certTokens[dom] = &cert
+	p.m.mu.Unlock()
+
+	return nil
+}
+
+func (p tlsProvider) CleanUp(domain, token, keyAuth string) error {
+	_, dom, err := acme.TLSSNI01ChallengeCertDomain(keyAuth)
+	if err != nil {
+		return err
+	}
+
+	p.m.mu.Lock()
+	delete(p.m.certTokens, dom)
+	p.m.mu.Unlock()
+
+	return nil
+}
+
+func marshalKey(key *ecdsa.PrivateKey) ([]byte, error) {
+	data, err := x509.MarshalECPrivateKey(key)
+	if err != nil {
+		return nil, err
+	}
+	return pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: data}), nil
+}
+
+func unmarshalKey(text string) (*ecdsa.PrivateKey, error) {
+	b, _ := pem.Decode([]byte(text))
+	if b == nil {
+		return nil, fmt.Errorf("unmarshalKey: missing key")
+	}
+	if b.Type != "EC PRIVATE KEY" {
+		return nil, fmt.Errorf("unmarshalKey: found %q, not %q", b.Type, "EC PRIVATE KEY")
+	}
+	k, err := x509.ParseECPrivateKey(b.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("unmarshalKey: %v", err)
+	}
+	return k, nil
+}
+
+func newKey() (*ecdsa.PrivateKey, error) {
+	return ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+}