telebit/vendor/github.com/caddyserver/certmagic/handshake.go

498 lines
18 KiB
Go
Raw Normal View History

2020-05-05 04:12:34 +00:00
// Copyright 2015 Matthew Holt
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package certmagic
import (
"context"
"crypto/tls"
"encoding/json"
"fmt"
"log"
"net"
"strings"
"sync"
"time"
"github.com/go-acme/lego/v3/challenge/tlsalpn01"
)
// GetCertificate gets a certificate to satisfy clientHello. In getting
// the certificate, it abides the rules and settings defined in the
// Config that matches clientHello.ServerName. It first checks the in-
// memory cache, then, if the config enables "OnDemand", it accesses
// disk, then accesses the network if it must obtain a new certificate
// via ACME.
//
// This method is safe for use as a tls.Config.GetCertificate callback.
func (cfg *Config) GetCertificate(clientHello *tls.ClientHelloInfo) (*tls.Certificate, error) {
cfg.emit("tls_handshake_started", clientHello)
// special case: serve up the certificate for a TLS-ALPN ACME challenge
// (https://tools.ietf.org/html/draft-ietf-acme-tls-alpn-05)
for _, proto := range clientHello.SupportedProtos {
if proto == tlsalpn01.ACMETLS1Protocol {
cfg.certCache.mu.RLock()
challengeCert, ok := cfg.certCache.cache[tlsALPNCertKeyName(clientHello.ServerName)]
cfg.certCache.mu.RUnlock()
if !ok {
// see if this challenge was started in a cluster; try distributed challenge solver
// (note that the tls.Config's ALPN settings must include the ACME TLS-ALPN challenge
// protocol string, otherwise a valid certificate will not solve the challenge; we
// should already have taken care of that when we made the tls.Config)
challengeCert, ok, err := cfg.tryDistributedChallengeSolver(clientHello)
if err != nil {
log.Printf("[ERROR][%s] TLS-ALPN challenge: %v", clientHello.ServerName, err)
}
if ok {
log.Printf("[INFO][%s] Served key authentication certificate (distributed TLS-ALPN challenge)", clientHello.ServerName)
return &challengeCert.Certificate, nil
}
return nil, fmt.Errorf("no certificate to complete TLS-ALPN challenge for SNI name: %s", clientHello.ServerName)
}
log.Printf("[INFO][%s] Served key authentication certificate (TLS-ALPN challenge)", clientHello.ServerName)
return &challengeCert.Certificate, nil
}
}
// get the certificate and serve it up
cert, err := cfg.getCertDuringHandshake(clientHello, true, true)
if err == nil {
cfg.emit("tls_handshake_completed", clientHello)
}
return &cert.Certificate, err
}
// getCertificate gets a certificate that matches name from the in-memory
// cache, according to the lookup table associated with cfg. The lookup then
// points to a certificate in the Instance certificate cache.
//
// The name is expected to already be normalized (e.g. lowercased).
//
// If there is no exact match for name, it will be checked against names of
// the form '*.example.com' (wildcard certificates) according to RFC 6125.
// If a match is found, matched will be true. If no matches are found, matched
// will be false and a "default" certificate will be returned with defaulted
// set to true. If defaulted is false, then no certificates were available.
//
// The logic in this function is adapted from the Go standard library,
// which is by the Go Authors.
//
// This function is safe for concurrent use.
func (cfg *Config) getCertificate(hello *tls.ClientHelloInfo) (cert Certificate, matched, defaulted bool) {
name := NormalizedName(hello.ServerName)
if name == "" {
// if SNI is empty, prefer matching IP address
if hello.Conn != nil {
addr := hello.Conn.LocalAddr().String()
ip, _, err := net.SplitHostPort(addr)
if err == nil {
addr = ip
}
cert, matched = cfg.selectCert(hello, addr)
if matched {
return
}
}
// fall back to a "default" certificate, if specified
if cfg.DefaultServerName != "" {
normDefault := NormalizedName(cfg.DefaultServerName)
cert, defaulted = cfg.selectCert(hello, normDefault)
if defaulted {
return
}
}
} else {
// if SNI is specified, try an exact match first
cert, matched = cfg.selectCert(hello, name)
if matched {
return
}
// try replacing labels in the name with
// wildcards until we get a match
labels := strings.Split(name, ".")
for i := range labels {
labels[i] = "*"
candidate := strings.Join(labels, ".")
cert, matched = cfg.selectCert(hello, candidate)
if matched {
return
}
}
// check the certCache directly to see if the SNI name is
// already the key of the certificate it wants; this implies
// that the SNI can contain the hash of a specific cert
// (chain) it wants and we will still be able to serve it up
// (this behavior, by the way, could be controversial as to
// whether it complies with RFC 6066 about SNI, but I think
// it does, soooo...)
// (this is how we solved the former ACME TLS-SNI challenge)
cfg.certCache.mu.RLock()
directCert, ok := cfg.certCache.cache[name]
cfg.certCache.mu.RUnlock()
if ok {
cert = directCert
matched = true
return
}
}
// otherwise, we're bingo on ammo; see issues
// caddyserver/caddy#2035 and caddyserver/caddy#1303 (any
// change to certificate matching behavior must
// account for hosts defined where the hostname
// is empty or a catch-all, like ":443" or
// "0.0.0.0:443")
return
}
// selectCert uses hello to select a certificate from the
// cache for name. If cfg.CertSelection is set, it will be
// used to make the decision. Otherwise, the first matching
// unexpired cert is returned. As a special case, if no
// certificates match name and cfg.CertSelection is set,
// then all certificates in the cache will be passed in
// for the cfg.CertSelection to make the final decision.
func (cfg *Config) selectCert(hello *tls.ClientHelloInfo, name string) (Certificate, bool) {
choices := cfg.certCache.getAllMatchingCerts(name)
if len(choices) == 0 {
if cfg.CertSelection == nil {
return Certificate{}, false
}
choices = cfg.certCache.getAllCerts()
}
if cfg.CertSelection == nil {
cert, err := DefaultCertificateSelector(hello, choices)
return cert, err == nil
}
cert, err := cfg.CertSelection.SelectCertificate(hello, choices)
return cert, err == nil
}
// DefaultCertificateSelector is the default certificate selection logic
// given a choice of certificates. If there is at least one certificate in
// choices, it always returns a certificate without error. It chooses the
// first non-expired certificate that the client supports if possible,
// otherwise it returns an expired certificate that the client supports,
// otherwise it just returns the first certificate in the list of choices.
func DefaultCertificateSelector(hello *tls.ClientHelloInfo, choices []Certificate) (Certificate, error) {
if len(choices) == 0 {
return Certificate{}, fmt.Errorf("no certificates available")
}
now := time.Now()
best := choices[0]
for _, choice := range choices {
if err := hello.SupportsCertificate(&choice.Certificate); err != nil {
continue
}
best = choice // at least the client supports it...
if now.After(choice.Leaf.NotBefore) && now.Before(choice.Leaf.NotAfter) {
return choice, nil // ...and unexpired, great! "Certificate, I choose you!"
}
}
return best, nil // all matching certs are expired or incompatible, oh well
}
// getCertDuringHandshake will get a certificate for hello. It first tries
// the in-memory cache. If no certificate for hello is in the cache, the
// config most closely corresponding to hello will be loaded. If that config
// allows it (OnDemand==true) and if loadIfNecessary == true, it goes to disk
// to load it into the cache and serve it. If it's not on disk and if
// obtainIfNecessary == true, the certificate will be obtained from the CA,
// cached, and served. If obtainIfNecessary is true, then loadIfNecessary
// must also be set to true. An error will be returned if and only if no
// certificate is available.
//
// This function is safe for concurrent use.
func (cfg *Config) getCertDuringHandshake(hello *tls.ClientHelloInfo, loadIfNecessary, obtainIfNecessary bool) (Certificate, error) {
// First check our in-memory cache to see if we've already loaded it
cert, matched, defaulted := cfg.getCertificate(hello)
if matched {
return cert, nil
}
name := cfg.getNameFromClientHello(hello)
// If OnDemand is enabled, then we might be able to load or
// obtain a needed certificate
if cfg.OnDemand != nil && loadIfNecessary {
// Then check to see if we have one on disk
loadedCert, err := cfg.CacheManagedCertificate(name)
if err == nil {
loadedCert, err = cfg.handshakeMaintenance(hello, loadedCert)
if err != nil {
log.Printf("[ERROR] Maintaining newly-loaded certificate for %s: %v", name, err)
}
return loadedCert, nil
}
if obtainIfNecessary {
// By this point, we need to ask the CA for a certificate
// Make sure the certificate should be obtained based on config
err := cfg.checkIfCertShouldBeObtained(name)
if err != nil {
return Certificate{}, err
}
// Obtain certificate from the CA
return cfg.obtainOnDemandCertificate(hello)
}
}
// Fall back to the default certificate if there is one
if defaulted {
return cert, nil
}
return Certificate{}, fmt.Errorf("no certificate available for '%s'", name)
}
// checkIfCertShouldBeObtained checks to see if an on-demand TLS certificate
// should be obtained for a given domain based upon the config settings. If
// a non-nil error is returned, do not issue a new certificate for name.
func (cfg *Config) checkIfCertShouldBeObtained(name string) error {
if cfg.OnDemand == nil {
return fmt.Errorf("not configured for on-demand certificate issuance")
}
if !SubjectQualifiesForCert(name) {
return fmt.Errorf("subject name does not qualify for certificate: %s", name)
}
if cfg.OnDemand.DecisionFunc != nil {
return cfg.OnDemand.DecisionFunc(name)
}
if len(cfg.OnDemand.hostWhitelist) > 0 &&
!cfg.OnDemand.whitelistContains(name) {
return fmt.Errorf("certificate for '%s' is not managed", name)
}
return nil
}
// obtainOnDemandCertificate obtains a certificate for hello.
// If another goroutine has already started obtaining a cert for
// hello, it will wait and use what the other goroutine obtained.
//
// This function is safe for use by multiple concurrent goroutines.
func (cfg *Config) obtainOnDemandCertificate(hello *tls.ClientHelloInfo) (Certificate, error) {
name := cfg.getNameFromClientHello(hello)
// We must protect this process from happening concurrently, so synchronize.
obtainCertWaitChansMu.Lock()
wait, ok := obtainCertWaitChans[name]
if ok {
// lucky us -- another goroutine is already obtaining the certificate.
// wait for it to finish obtaining the cert and then we'll use it.
obtainCertWaitChansMu.Unlock()
<-wait
return cfg.getCertDuringHandshake(hello, true, false)
}
// looks like it's up to us to do all the work and obtain the cert.
// make a chan others can wait on if needed
wait = make(chan struct{})
obtainCertWaitChans[name] = wait
obtainCertWaitChansMu.Unlock()
// obtain the certificate
log.Printf("[INFO] Obtaining new certificate for %s", name)
// TODO: use a proper context; we use one with timeout because retries are enabled because interactive is false
ctx, cancel := context.WithTimeout(context.TODO(), 90*time.Second)
defer cancel()
err := cfg.ObtainCert(ctx, name, false)
// immediately unblock anyone waiting for it; doing this in
// a defer would risk deadlock because of the recursive call
// to getCertDuringHandshake below when we return!
obtainCertWaitChansMu.Lock()
close(wait)
delete(obtainCertWaitChans, name)
obtainCertWaitChansMu.Unlock()
if err != nil {
// shucks; failed to solve challenge on-demand
return Certificate{}, err
}
// success; certificate was just placed on disk, so
// we need only restart serving the certificate
return cfg.getCertDuringHandshake(hello, true, false)
}
// handshakeMaintenance performs a check on cert for expiration and OCSP validity.
//
// This function is safe for use by multiple concurrent goroutines.
func (cfg *Config) handshakeMaintenance(hello *tls.ClientHelloInfo, cert Certificate) (Certificate, error) {
// Check cert expiration
timeLeft := cert.Leaf.NotAfter.Sub(time.Now().UTC())
if currentlyInRenewalWindow(cert.Leaf.NotBefore, cert.Leaf.NotAfter, cfg.RenewalWindowRatio) {
log.Printf("[INFO] Certificate for %v expires in %s; attempting renewal", cert.Names, timeLeft)
return cfg.renewDynamicCertificate(hello, cert)
}
// Check OCSP staple validity
if cert.ocsp != nil {
refreshTime := cert.ocsp.ThisUpdate.Add(cert.ocsp.NextUpdate.Sub(cert.ocsp.ThisUpdate) / 2)
if time.Now().After(refreshTime) {
_, err := stapleOCSP(cfg.Storage, &cert, nil)
if err != nil {
// An error with OCSP stapling is not the end of the world, and in fact, is
// quite common considering not all certs have issuer URLs that support it.
log.Printf("[ERROR] Getting OCSP for %s: %v", hello.ServerName, err)
}
cfg.certCache.mu.Lock()
cfg.certCache.cache[cert.hash] = cert
cfg.certCache.mu.Unlock()
}
}
return cert, nil
}
// renewDynamicCertificate renews the certificate for name using cfg. It returns the
// certificate to use and an error, if any. name should already be lower-cased before
// calling this function. name is the name obtained directly from the handshake's
// ClientHello.
//
// This function is safe for use by multiple concurrent goroutines.
func (cfg *Config) renewDynamicCertificate(hello *tls.ClientHelloInfo, currentCert Certificate) (Certificate, error) {
name := cfg.getNameFromClientHello(hello)
obtainCertWaitChansMu.Lock()
wait, ok := obtainCertWaitChans[name]
if ok {
// lucky us -- another goroutine is already renewing the certificate.
// wait for it to finish, then we'll use the new one.
obtainCertWaitChansMu.Unlock()
<-wait
return cfg.getCertDuringHandshake(hello, true, false)
}
// looks like it's up to us to do all the work and renew the cert
wait = make(chan struct{})
obtainCertWaitChans[name] = wait
obtainCertWaitChansMu.Unlock()
// Make sure a certificate for this name should be obtained on-demand
err := cfg.checkIfCertShouldBeObtained(name)
if err != nil {
// if not, remove from cache (it will be deleted from storage later)
cfg.certCache.mu.Lock()
cfg.certCache.removeCertificate(currentCert)
cfg.certCache.mu.Unlock()
return Certificate{}, err
}
// renew and reload the certificate
log.Printf("[INFO] Renewing certificate for %s", name)
// TODO: use a proper context; we use one with timeout because retries are enabled because interactive is false
ctx, cancel := context.WithTimeout(context.TODO(), 90*time.Second)
defer cancel()
err = cfg.RenewCert(ctx, name, false)
if err == nil {
// even though the recursive nature of the dynamic cert loading
// would just call this function anyway, we do it here to
// make the replacement as atomic as possible.
newCert, err := cfg.CacheManagedCertificate(name)
if err != nil {
log.Printf("[ERROR] loading renewed certificate for %s: %v", name, err)
} else {
// replace the old certificate with the new one
cfg.certCache.replaceCertificate(currentCert, newCert)
}
}
// immediately unblock anyone waiting for it; doing this in
// a defer would risk deadlock because of the recursive call
// to getCertDuringHandshake below when we return!
obtainCertWaitChansMu.Lock()
close(wait)
delete(obtainCertWaitChans, name)
obtainCertWaitChansMu.Unlock()
if err != nil {
return Certificate{}, err
}
return cfg.getCertDuringHandshake(hello, true, false)
}
// tryDistributedChallengeSolver is to be called when the clientHello pertains to
// a TLS-ALPN challenge and a certificate is required to solve it. This method
// checks the distributed store of challenge info files and, if a matching ServerName
// is present, it makes a certificate to solve this challenge and returns it. For
// this to succeed, it requires that cfg.Issuer is of type *ACMEManager.
// A boolean true is returned if a valid certificate is returned.
func (cfg *Config) tryDistributedChallengeSolver(clientHello *tls.ClientHelloInfo) (Certificate, bool, error) {
am, ok := cfg.Issuer.(*ACMEManager)
if !ok {
return Certificate{}, false, nil
}
tokenKey := distributedSolver{acmeManager: am, caURL: am.CA}.challengeTokensKey(clientHello.ServerName)
chalInfoBytes, err := cfg.Storage.Load(tokenKey)
if err != nil {
if _, ok := err.(ErrNotExist); ok {
return Certificate{}, false, nil
}
return Certificate{}, false, fmt.Errorf("opening distributed challenge token file %s: %v", tokenKey, err)
}
var chalInfo challengeInfo
err = json.Unmarshal(chalInfoBytes, &chalInfo)
if err != nil {
return Certificate{}, false, fmt.Errorf("decoding challenge token file %s (corrupted?): %v", tokenKey, err)
}
cert, err := tlsalpn01.ChallengeCert(chalInfo.Domain, chalInfo.KeyAuth)
if err != nil {
return Certificate{}, false, fmt.Errorf("making TLS-ALPN challenge certificate: %v", err)
}
if cert == nil {
return Certificate{}, false, fmt.Errorf("got nil TLS-ALPN challenge certificate but no error")
}
return Certificate{Certificate: *cert}, true, nil
}
// getNameFromClientHello returns a normalized form of hello.ServerName.
// If hello.ServerName is empty (i.e. client did not use SNI), then the
// associated connection's local address is used to extract an IP address.
func (*Config) getNameFromClientHello(hello *tls.ClientHelloInfo) string {
name := NormalizedName(hello.ServerName)
if name != "" || hello.Conn == nil {
return name
}
// if no SNI, try using IP address on the connection
localAddr := hello.Conn.LocalAddr().String()
localAddrHost, _, err := net.SplitHostPort(localAddr)
if err == nil {
return localAddrHost
}
return localAddr
}
// NormalizedName returns a cleaned form of serverName that is
// used for consistency when referring to a SNI value.
func NormalizedName(serverName string) string {
return strings.ToLower(strings.TrimSpace(serverName))
}
// obtainCertWaitChans is used to coordinate obtaining certs for each hostname.
var obtainCertWaitChans = make(map[string]chan struct{})
var obtainCertWaitChansMu sync.Mutex