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letsencrypt.go
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letsencrypt.go
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// Package letsencrypt integrates Let's Encrypt functionality into Caddy
// with first-class support for creating and renewing certificates
// automatically. It is designed to configure sites for HTTPS by default.
package letsencrypt
import (
"encoding/json"
"errors"
"io/ioutil"
"net/http"
"os"
"strings"
"time"
"github.com/mholt/caddy/caddy/setup"
"github.com/mholt/caddy/middleware"
"github.com/mholt/caddy/middleware/redirect"
"github.com/mholt/caddy/server"
"github.com/xenolf/lego/acme"
)
// Activate sets up TLS for each server config in configs
// as needed. It only skips the config if the cert and key
// are already provided, if plaintext http is explicitly
// specified as the port, TLS is explicitly disabled, or
// the host looks like a loopback or wildcard address.
//
// This function may prompt the user to provide an email
// address if none is available through other means. It
// prefers the email address specified in the config, but
// if that is not available it will check the command line
// argument. If absent, it will use the most recent email
// address from last time. If there isn't one, the user
// will be prompted and shown SA link.
//
// Also note that calling this function activates asset
// management automatically, which keeps certificates
// renewed and OCSP stapling updated. This has the effect
// of causing restarts when assets are updated.
//
// Activate returns the updated list of configs, since
// some may have been appended, for example, to redirect
// plaintext HTTP requests to their HTTPS counterpart.
// This function only appends; it does not prepend or splice.
func Activate(configs []server.Config) ([]server.Config, error) {
// just in case previous caller forgot...
Deactivate()
// reset cached ocsp statuses from any previous activations
ocspStatus = make(map[*[]byte]int)
// Identify and configure any eligible hosts for which
// we already have certs and keys in storage from last time.
configLen := len(configs) // avoid infinite loop since this loop appends plaintext to the slice
for i := 0; i < configLen; i++ {
if existingCertAndKey(configs[i].Host) && configQualifies(configs, i) {
configs = autoConfigure(configs, i)
}
}
// Group configs by email address; only configs that are eligible
// for TLS management are included. We group by email so that we
// can request certificates in batches with the same client.
// Note: The return value is a map, and iteration over a map is
// not ordered. I don't think it will be a problem, but if an
// ordering problem arises, look at this carefully.
groupedConfigs, err := groupConfigsByEmail(configs)
if err != nil {
return configs, err
}
// obtain certificates for configs that need one, and reconfigure each
// config to use the certificates
for leEmail, cfgIndexes := range groupedConfigs {
// make client to service this email address with CA server
client, err := newClient(leEmail)
if err != nil {
return configs, errors.New("error creating client: " + err.Error())
}
// little bit of housekeeping; gather the hostnames into a slice
var hosts []string
for _, idx := range cfgIndexes {
// don't allow duplicates (happens when serving same host on multiple ports!)
var duplicate bool
for _, otherHost := range hosts {
if configs[idx].Host == otherHost {
duplicate = true
break
}
}
if !duplicate {
hosts = append(hosts, configs[idx].Host)
}
}
// client is ready, so let's get free, trusted SSL certificates!
Obtain:
certificates, failures := client.ObtainCertificates(hosts, true)
if len(failures) > 0 {
// Build an error string to return, using all the failures in the list.
var errMsg string
// If an error is because of updated SA, only prompt user for agreement once
var promptedForAgreement bool
for domain, obtainErr := range failures {
// If the failure was simply because the terms have changed, re-prompt and re-try
if tosErr, ok := obtainErr.(acme.TOSError); ok {
if !Agreed && !promptedForAgreement {
Agreed = promptUserAgreement(tosErr.Detail, true) // TODO: Use latest URL
promptedForAgreement = true
}
if Agreed {
err := client.AgreeToTOS()
if err != nil {
return configs, errors.New("error agreeing to updated terms: " + err.Error())
}
goto Obtain
}
}
// If user did not agree or it was any other kind of error, just append to the list of errors
errMsg += "[" + domain + "] failed to get certificate: " + obtainErr.Error() + "\n"
}
return configs, errors.New(errMsg)
}
// ... that's it. save the certs, keys, and metadata files to disk
err = saveCertsAndKeys(certificates)
if err != nil {
return configs, errors.New("error saving assets: " + err.Error())
}
// it all comes down to this: turning on TLS with all the new certs
for _, idx := range cfgIndexes {
configs = autoConfigure(configs, idx)
}
}
// renew all certificates that need renewal
renewCertificates(configs, false)
// keep certificates renewed and OCSP stapling updated
go maintainAssets(configs, stopChan)
return configs, nil
}
// Deactivate cleans up long-term, in-memory resources
// allocated by calling Activate(). Essentially, it stops
// the asset maintainer from running, meaning that certificates
// will not be renewed, OCSP staples will not be updated, etc.
func Deactivate() (err error) {
defer func() {
if rec := recover(); rec != nil {
err = errors.New("already deactivated")
}
}()
close(stopChan)
stopChan = make(chan struct{})
return
}
// configQualifies returns true if the config at cfgIndex (within allConfigs)
// qualifes for automatic LE activation. It does NOT check to see if a cert
// and key already exist for the config.
func configQualifies(allConfigs []server.Config, cfgIndex int) bool {
cfg := allConfigs[cfgIndex]
return cfg.TLS.Certificate == "" && // user could provide their own cert and key
cfg.TLS.Key == "" &&
// user can force-disable automatic HTTPS for this host
cfg.Port != "http" &&
cfg.TLS.LetsEncryptEmail != "off" &&
// obviously we get can't certs for loopback or internal hosts
HostQualifies(cfg.Host) &&
// make sure another HTTPS version of this config doesn't exist in the list already
!otherHostHasScheme(allConfigs, cfgIndex, "https")
}
// HostQualifies returns true if the hostname alone
// appears eligible for automatic HTTPS. For example,
// localhost, empty hostname, and wildcard hosts are
// not eligible because we cannot obtain certificates
// for those names.
func HostQualifies(hostname string) bool {
return hostname != "localhost" &&
strings.TrimSpace(hostname) != "" &&
hostname != "0.0.0.0" &&
hostname != "[::]" && // before parsing
hostname != "::" && // after parsing
hostname != "[::1]" && // before parsing
hostname != "::1" && // after parsing
!strings.HasPrefix(hostname, "127.") // to use boulder on your own machine, add fake domain to hosts file
// not excluding 10.* and 192.168.* hosts for possibility of running internal Boulder instance
}
// groupConfigsByEmail groups configs by user email address. The returned map is
// a map of email address to the configs that are serviced under that account.
// If an email address is not available for an eligible config, the user will be
// prompted to provide one. The returned map contains pointers to the original
// server config values.
func groupConfigsByEmail(configs []server.Config) (map[string][]int, error) {
initMap := make(map[string][]int)
for i := 0; i < len(configs); i++ {
// filter out configs that we already have certs for and
// that we won't be obtaining certs for - this way we won't
// bother the user for an email address unnecessarily and
// we don't obtain new certs for a host we already have certs for.
if existingCertAndKey(configs[i].Host) || !configQualifies(configs, i) {
continue
}
leEmail := getEmail(configs[i])
initMap[leEmail] = append(initMap[leEmail], i)
}
return initMap, nil
}
// existingCertAndKey returns true if the host has a certificate
// and private key in storage already, false otherwise.
func existingCertAndKey(host string) bool {
_, err := os.Stat(storage.SiteCertFile(host))
if err != nil {
return false
}
_, err = os.Stat(storage.SiteKeyFile(host))
if err != nil {
return false
}
return true
}
// newClient creates a new ACME client to facilitate communication
// with the Let's Encrypt CA server on behalf of the user specified
// by leEmail. As part of this process, a user will be loaded from
// disk (if already exists) or created new and registered via ACME
// and saved to the file system for next time.
func newClient(leEmail string) (*acme.Client, error) {
return newClientPort(leEmail, "")
}
// newClientPort does the same thing as newClient, except it creates a
// new client with a custom port used for ACME transactions instead of
// the default port. This is important if the default port is already in
// use or is not exposed to the public, etc.
func newClientPort(leEmail, port string) (*acme.Client, error) {
// Look up or create the LE user account
leUser, err := getUser(leEmail)
if err != nil {
return nil, err
}
// The client facilitates our communication with the CA server.
client, err := acme.NewClient(CAUrl, &leUser, rsaKeySizeToUse, port)
if err != nil {
return nil, err
}
// If not registered, the user must register an account with the CA
// and agree to terms
if leUser.Registration == nil {
reg, err := client.Register()
if err != nil {
return nil, errors.New("registration error: " + err.Error())
}
leUser.Registration = reg
if !Agreed && reg.TosURL == "" {
Agreed = promptUserAgreement(saURL, false) // TODO - latest URL
}
if !Agreed && reg.TosURL == "" {
return nil, errors.New("user must agree to terms")
}
err = client.AgreeToTOS()
if err != nil {
saveUser(leUser) // TODO: Might as well try, right? Error check?
return nil, errors.New("error agreeing to terms: " + err.Error())
}
// save user to the file system
err = saveUser(leUser)
if err != nil {
return nil, errors.New("could not save user: " + err.Error())
}
}
return client, nil
}
// obtainCertificates obtains certificates from the CA server for
// the configurations in serverConfigs using client.
func obtainCertificates(client *acme.Client, serverConfigs []server.Config) ([]acme.CertificateResource, map[string]error) {
var hosts []string
for _, cfg := range serverConfigs {
hosts = append(hosts, cfg.Host)
}
return client.ObtainCertificates(hosts, true)
}
// saveCertificates saves each certificate resource to disk. This
// includes the certificate file itself, the private key, and the
// metadata file.
func saveCertsAndKeys(certificates []acme.CertificateResource) error {
for _, cert := range certificates {
err := os.MkdirAll(storage.Site(cert.Domain), 0700)
if err != nil {
return err
}
// Save cert
err = ioutil.WriteFile(storage.SiteCertFile(cert.Domain), cert.Certificate, 0600)
if err != nil {
return err
}
// Save private key
err = ioutil.WriteFile(storage.SiteKeyFile(cert.Domain), cert.PrivateKey, 0600)
if err != nil {
return err
}
// Save cert metadata
jsonBytes, err := json.MarshalIndent(&cert, "", "\t")
if err != nil {
return err
}
err = ioutil.WriteFile(storage.SiteMetaFile(cert.Domain), jsonBytes, 0600)
if err != nil {
return err
}
}
return nil
}
// autoConfigure enables TLS on allConfigs[cfgIndex] and appends, if necessary,
// a new config to allConfigs that redirects plaintext HTTP to its new HTTPS
// counterpart. It expects the certificate and key to already be in storage. It
// returns the new list of allConfigs, since it may append a new config. This
// function assumes that allConfigs[cfgIndex] is already set up for HTTPS.
func autoConfigure(allConfigs []server.Config, cfgIndex int) []server.Config {
cfg := &allConfigs[cfgIndex]
bundleBytes, err := ioutil.ReadFile(storage.SiteCertFile(cfg.Host))
// TODO: Handle these errors better
if err == nil {
ocsp, status, err := acme.GetOCSPForCert(bundleBytes)
ocspStatus[&bundleBytes] = status
if err == nil && status == acme.OCSPGood {
cfg.TLS.OCSPStaple = ocsp
}
}
cfg.TLS.Certificate = storage.SiteCertFile(cfg.Host)
cfg.TLS.Key = storage.SiteKeyFile(cfg.Host)
cfg.TLS.Enabled = true
// Ensure all defaults are set for the TLS config
setup.SetDefaultTLSParams(cfg)
if cfg.Port == "" {
cfg.Port = "https"
}
// Set up http->https redirect as long as there isn't already a http counterpart
// in the configs and this isn't, for some reason, already on port 80.
// Also, the port 80 variant of this config is necessary for proxying challenge requests.
if !otherHostHasScheme(allConfigs, cfgIndex, "http") &&
cfg.Port != "80" && cfg.Port != "http" { // (would not be http port with current program flow, but just in case)
allConfigs = append(allConfigs, redirPlaintextHost(*cfg))
}
// To support renewals, we need handlers at ports 80 and 443,
// depending on the challenge type that is used to complete renewal.
for i, c := range allConfigs {
if c.Address() == cfg.Host+":80" ||
c.Address() == cfg.Host+":443" ||
c.Address() == cfg.Host+":http" ||
c.Address() == cfg.Host+":https" {
// Each virtualhost must have their own handlers, or the chaining gets messed up when middlewares are compiled!
handler := new(Handler)
mid := func(next middleware.Handler) middleware.Handler {
handler.Next = next
return handler
}
// TODO: Currently, acmeHandlers are not referenced, but we need to add a way to toggle
// their proxy functionality -- or maybe not. Gotta figure this out for sure.
acmeHandlers[c.Address()] = handler
allConfigs[i].Middleware["/"] = append(allConfigs[i].Middleware["/"], mid)
}
}
return allConfigs
}
// otherHostHasScheme tells you whether there is ANOTHER config in allConfigs
// for the same host but with the port equal to scheme as allConfigs[cfgIndex].
// This function considers "443" and "https" to be the same scheme, as well as
// "http" and "80". It does not tell you whether there is ANY config with scheme,
// only if there's a different one with it.
func otherHostHasScheme(allConfigs []server.Config, cfgIndex int, scheme string) bool {
if scheme == "80" {
scheme = "http"
} else if scheme == "443" {
scheme = "https"
}
for i, otherCfg := range allConfigs {
if i == cfgIndex {
continue // has to be a config OTHER than the one we're comparing against
}
if otherCfg.Host == allConfigs[cfgIndex].Host {
if (otherCfg.Port == scheme) ||
(scheme == "https" && otherCfg.Port == "443") ||
(scheme == "http" && otherCfg.Port == "80") {
return true
}
}
}
return false
}
// redirPlaintextHost returns a new plaintext HTTP configuration for
// a virtualHost that simply redirects to cfg, which is assumed to
// be the HTTPS configuration. The returned configuration is set
// to listen on the "http" port (port 80).
func redirPlaintextHost(cfg server.Config) server.Config {
toURL := "https://" + cfg.Host
if cfg.Port != "https" && cfg.Port != "http" {
toURL += ":" + cfg.Port
}
redirMidware := func(next middleware.Handler) middleware.Handler {
return redirect.Redirect{Next: next, Rules: []redirect.Rule{
{
FromScheme: "http",
FromPath: "/",
To: toURL + "{uri}",
Code: http.StatusMovedPermanently,
},
}}
}
return server.Config{
Host: cfg.Host,
Port: "http",
Middleware: map[string][]middleware.Middleware{
"/": []middleware.Middleware{redirMidware},
},
}
}
// Revoke revokes the certificate for host via ACME protocol.
func Revoke(host string) error {
if !existingCertAndKey(host) {
return errors.New("no certificate and key for " + host)
}
email := getEmail(server.Config{Host: host})
if email == "" {
return errors.New("email is required to revoke")
}
client, err := newClient(email)
if err != nil {
return err
}
certFile := storage.SiteCertFile(host)
certBytes, err := ioutil.ReadFile(certFile)
if err != nil {
return err
}
err = client.RevokeCertificate(certBytes)
if err != nil {
return err
}
err = os.Remove(certFile)
if err != nil {
return errors.New("certificate revoked, but unable to delete certificate file: " + err.Error())
}
return nil
}
var (
// DefaultEmail represents the Let's Encrypt account email to use if none provided
DefaultEmail string
// Agreed indicates whether user has agreed to the Let's Encrypt SA
Agreed bool
// CAUrl represents the base URL to the CA's ACME endpoint
CAUrl string
)
// Some essential values related to the Let's Encrypt process
const (
// alternatePort is the port on which the acme client will open a
// listener and solve the CA's challenges. If this alternate port
// is used instead of the default port (80 or 443), then the
// default port for the challenge must be forwarded to this one.
alternatePort = "5033"
// How often to check certificates for renewal.
renewInterval = 24 * time.Hour
// How often to update OCSP stapling.
ocspInterval = 1 * time.Hour
)
// KeySize represents the length of a key in bits.
type KeySize int
// Key sizes are used to determine the strength of a key.
const (
ECC_224 KeySize = 224
ECC_256 = 256
RSA_2048 = 2048
RSA_4096 = 4096
)
// rsaKeySizeToUse is the size to use for new RSA keys.
// This shouldn't need to change except for in tests;
// the size can be drastically reduced for speed.
var rsaKeySizeToUse = RSA_2048
// stopChan is used to signal the maintenance goroutine
// to terminate.
var stopChan chan struct{}
// ocspStatus maps certificate bundle to OCSP status at start.
// It is used during regular OCSP checks to see if the OCSP
// status has changed.
var ocspStatus = make(map[*[]byte]int)