TUN-528: Move cloudflared into a separate repo

vendor/github.com/mholt/caddy/caddytls/certificates.go

@@ -0,0 +1,390 @@
+// Copyright 2015 Light Code Labs, LLC
+//
+// 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 caddytls
+
+import (
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/mholt/caddy/telemetry"
+	"golang.org/x/crypto/ocsp"
+)
+
+// certificateCache is to be an instance-wide cache of certs
+// that site-specific TLS configs can refer to. Using a
+// central map like this avoids duplication of certs in
+// memory when the cert is used by multiple sites, and makes
+// maintenance easier. Because these are not to be global,
+// the cache will get garbage collected after a config reload
+// (a new instance will take its place).
+type certificateCache struct {
+	sync.RWMutex
+	cache map[string]Certificate // keyed by certificate hash
+}
+
+// replaceCertificate replaces oldCert with newCert in the cache, and
+// updates all configs that are pointing to the old certificate to
+// point to the new one instead. newCert must already be loaded into
+// the cache (this method does NOT load it into the cache).
+//
+// Note that all the names on the old certificate will be deleted
+// from the name lookup maps of each config, then all the names on
+// the new certificate will be added to the lookup maps as long as
+// they do not overwrite any entries.
+//
+// The newCert may be modified and its cache entry updated.
+//
+// This method is safe for concurrent use.
+func (certCache *certificateCache) replaceCertificate(oldCert, newCert Certificate) error {
+	certCache.Lock()
+	defer certCache.Unlock()
+
+	// have all the configs that are pointing to the old
+	// certificate point to the new certificate instead
+	for _, cfg := range oldCert.configs {
+		// first delete all the name lookup entries that
+		// pointed to the old certificate
+		for name, certKey := range cfg.Certificates {
+			if certKey == oldCert.Hash {
+				delete(cfg.Certificates, name)
+			}
+		}
+
+		// then add name lookup entries for the names
+		// on the new certificate, but don't overwrite
+		// entries that may already exist, not only as
+		// a courtesy, but importantly: because if we
+		// overwrote a value here, and this config no
+		// longer pointed to a certain certificate in
+		// the cache, that certificate's list of configs
+		// referring to it would be incorrect; so just
+		// insert entries, don't overwrite any
+		for _, name := range newCert.Names {
+			if _, ok := cfg.Certificates[name]; !ok {
+				cfg.Certificates[name] = newCert.Hash
+			}
+		}
+	}
+
+	// since caching a new certificate attaches only the config
+	// that loaded it, the new certificate needs to be given the
+	// list of all the configs that use it, so copy the list
+	// over from the old certificate to the new certificate
+	// in the cache
+	newCert.configs = oldCert.configs
+	certCache.cache[newCert.Hash] = newCert
+
+	// finally, delete the old certificate from the cache
+	delete(certCache.cache, oldCert.Hash)
+
+	return nil
+}
+
+// reloadManagedCertificate reloads the certificate corresponding to the name(s)
+// on oldCert into the cache, from storage. This also replaces the old certificate
+// with the new one, so that all configurations that used the old cert now point
+// to the new cert.
+func (certCache *certificateCache) reloadManagedCertificate(oldCert Certificate) error {
+	// get the certificate from storage and cache it
+	newCert, err := oldCert.configs[0].CacheManagedCertificate(oldCert.Names[0])
+	if err != nil {
+		return fmt.Errorf("unable to reload certificate for %v into cache: %v", oldCert.Names, err)
+	}
+
+	// and replace the old certificate with the new one
+	err = certCache.replaceCertificate(oldCert, newCert)
+	if err != nil {
+		return fmt.Errorf("replacing certificate %v: %v", oldCert.Names, err)
+	}
+
+	return nil
+}
+
+// Certificate is a tls.Certificate with associated metadata tacked on.
+// Even if the metadata can be obtained by parsing the certificate,
+// we are more efficient by extracting the metadata onto this struct.
+type Certificate struct {
+	tls.Certificate
+
+	// Names is the list of names this certificate is written for.
+	// The first is the CommonName (if any), the rest are SAN.
+	Names []string
+
+	// NotAfter is when the certificate expires.
+	NotAfter time.Time
+
+	// OCSP contains the certificate's parsed OCSP response.
+	OCSP *ocsp.Response
+
+	// The hex-encoded hash of this cert's chain's bytes.
+	Hash string
+
+	// configs is the list of configs that use or refer to
+	// The first one is assumed to be the config that is
+	// "in charge" of this certificate (i.e. determines
+	// whether it is managed, how it is managed, etc).
+	// This field will be populated by cacheCertificate.
+	// Only meddle with it if you know what you're doing!
+	configs []*Config
+}
+
+// CacheManagedCertificate loads the certificate for domain into the
+// cache, from the TLS storage for managed certificates. It returns a
+// copy of the Certificate that was put into the cache.
+//
+// This method is safe for concurrent use.
+func (cfg *Config) CacheManagedCertificate(domain string) (Certificate, error) {
+	storage, err := cfg.StorageFor(cfg.CAUrl)
+	if err != nil {
+		return Certificate{}, err
+	}
+	siteData, err := storage.LoadSite(domain)
+	if err != nil {
+		return Certificate{}, err
+	}
+	cert, err := makeCertificateWithOCSP(siteData.Cert, siteData.Key)
+	if err != nil {
+		return cert, err
+	}
+	telemetry.Increment("tls_managed_cert_count")
+	return cfg.cacheCertificate(cert), nil
+}
+
+// cacheUnmanagedCertificatePEMFile loads a certificate for host using certFile
+// and keyFile, which must be in PEM format. It stores the certificate in
+// the in-memory cache.
+//
+// This function is safe for concurrent use.
+func (cfg *Config) cacheUnmanagedCertificatePEMFile(certFile, keyFile string) error {
+	cert, err := makeCertificateFromDiskWithOCSP(certFile, keyFile)
+	if err != nil {
+		return err
+	}
+	cfg.cacheCertificate(cert)
+	telemetry.Increment("tls_manual_cert_count")
+	return nil
+}
+
+// cacheUnmanagedCertificatePEMBytes makes a certificate out of the PEM bytes
+// of the certificate and key, then caches it in memory.
+//
+// This function is safe for concurrent use.
+func (cfg *Config) cacheUnmanagedCertificatePEMBytes(certBytes, keyBytes []byte) error {
+	cert, err := makeCertificateWithOCSP(certBytes, keyBytes)
+	if err != nil {
+		return err
+	}
+	cfg.cacheCertificate(cert)
+	telemetry.Increment("tls_manual_cert_count")
+	return nil
+}
+
+// makeCertificateFromDiskWithOCSP makes a Certificate by loading the
+// certificate and key files. It fills out all the fields in
+// the certificate except for the Managed and OnDemand flags.
+// (It is up to the caller to set those.) It staples OCSP.
+func makeCertificateFromDiskWithOCSP(certFile, keyFile string) (Certificate, error) {
+	certPEMBlock, err := ioutil.ReadFile(certFile)
+	if err != nil {
+		return Certificate{}, err
+	}
+	keyPEMBlock, err := ioutil.ReadFile(keyFile)
+	if err != nil {
+		return Certificate{}, err
+	}
+	return makeCertificateWithOCSP(certPEMBlock, keyPEMBlock)
+}
+
+// makeCertificate turns a certificate PEM bundle and a key PEM block into
+// a Certificate with necessary metadata from parsing its bytes filled into
+// its struct fields for convenience (except for the OnDemand and Managed
+// flags; it is up to the caller to set those properties!). This function
+// does NOT staple OCSP.
+func makeCertificate(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
+	var cert Certificate
+
+	// Convert to a tls.Certificate
+	tlsCert, err := tls.X509KeyPair(certPEMBlock, keyPEMBlock)
+	if err != nil {
+		return cert, err
+	}
+
+	// Extract necessary metadata
+	err = fillCertFromLeaf(&cert, tlsCert)
+	if err != nil {
+		return cert, err
+	}
+
+	return cert, nil
+}
+
+// makeCertificateWithOCSP is the same as makeCertificate except that it also
+// staples OCSP to the certificate.
+func makeCertificateWithOCSP(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
+	cert, err := makeCertificate(certPEMBlock, keyPEMBlock)
+	if err != nil {
+		return cert, err
+	}
+	err = stapleOCSP(&cert, certPEMBlock)
+	if err != nil {
+		log.Printf("[WARNING] Stapling OCSP: %v", err)
+	}
+	return cert, nil
+}
+
+// fillCertFromLeaf populates metadata fields on cert from tlsCert.
+func fillCertFromLeaf(cert *Certificate, tlsCert tls.Certificate) error {
+	if len(tlsCert.Certificate) == 0 {
+		return errors.New("certificate is empty")
+	}
+	cert.Certificate = tlsCert
+
+	// the leaf cert should be the one for the site; it has what we need
+	leaf, err := x509.ParseCertificate(tlsCert.Certificate[0])
+	if err != nil {
+		return err
+	}
+
+	if leaf.Subject.CommonName != "" { // TODO: CommonName is deprecated
+		cert.Names = []string{strings.ToLower(leaf.Subject.CommonName)}
+	}
+	for _, name := range leaf.DNSNames {
+		if name != leaf.Subject.CommonName { // TODO: CommonName is deprecated
+			cert.Names = append(cert.Names, strings.ToLower(name))
+		}
+	}
+	for _, ip := range leaf.IPAddresses {
+		if ipStr := ip.String(); ipStr != leaf.Subject.CommonName { // TODO: CommonName is deprecated
+			cert.Names = append(cert.Names, strings.ToLower(ipStr))
+		}
+	}
+	for _, email := range leaf.EmailAddresses {
+		if email != leaf.Subject.CommonName { // TODO: CommonName is deprecated
+			cert.Names = append(cert.Names, strings.ToLower(email))
+		}
+	}
+	if len(cert.Names) == 0 {
+		return errors.New("certificate has no names")
+	}
+
+	// save the hash of this certificate (chain) and
+	// expiration date, for necessity and efficiency
+	cert.Hash = hashCertificateChain(cert.Certificate.Certificate)
+	cert.NotAfter = leaf.NotAfter
+
+	return nil
+}
+
+// hashCertificateChain computes the unique hash of certChain,
+// which is the chain of DER-encoded bytes. It returns the
+// hex encoding of the hash.
+func hashCertificateChain(certChain [][]byte) string {
+	h := sha256.New()
+	for _, certInChain := range certChain {
+		h.Write(certInChain)
+	}
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
+
+// managedCertInStorageExpiresSoon returns true if cert (being a
+// managed certificate) is expiring within RenewDurationBefore.
+// It returns false if there was an error checking the expiration
+// of the certificate as found in storage, or if the certificate
+// in storage is NOT expiring soon. A certificate that is expiring
+// soon in our cache but is not expiring soon in storage probably
+// means that another instance renewed the certificate in the
+// meantime, and it would be a good idea to simply load the cert
+// into our cache rather than repeating the renewal process again.
+func managedCertInStorageExpiresSoon(cert Certificate) (bool, error) {
+	if len(cert.configs) == 0 {
+		return false, fmt.Errorf("no configs for certificate")
+	}
+	storage, err := cert.configs[0].StorageFor(cert.configs[0].CAUrl)
+	if err != nil {
+		return false, err
+	}
+	siteData, err := storage.LoadSite(cert.Names[0])
+	if err != nil {
+		return false, err
+	}
+	tlsCert, err := tls.X509KeyPair(siteData.Cert, siteData.Key)
+	if err != nil {
+		return false, err
+	}
+	leaf, err := x509.ParseCertificate(tlsCert.Certificate[0])
+	if err != nil {
+		return false, err
+	}
+	timeLeft := leaf.NotAfter.Sub(time.Now().UTC())
+	return timeLeft < RenewDurationBefore, nil
+}
+
+// cacheCertificate adds cert to the in-memory cache. If a certificate
+// with the same hash is already cached, it is NOT overwritten; instead,
+// cfg is added to the existing certificate's list of configs if not
+// already in the list. Then all the names on cert are used to add
+// entries to cfg.Certificates (the config's name lookup map).
+// Then the certificate is stored/updated in the cache. It returns
+// a copy of the certificate that ends up being stored in the cache.
+//
+// It is VERY important, even for some test cases, that the Hash field
+// of the cert be set properly.
+//
+// This function is safe for concurrent use.
+func (cfg *Config) cacheCertificate(cert Certificate) Certificate {
+	cfg.certCache.Lock()
+	defer cfg.certCache.Unlock()
+
+	// if this certificate already exists in the cache,
+	// use it instead of overwriting it -- very important!
+	if existingCert, ok := cfg.certCache.cache[cert.Hash]; ok {
+		cert = existingCert
+	}
+
+	// attach this config to the certificate so we know which
+	// configs are referencing/using the certificate, but don't
+	// duplicate entries
+	var found bool
+	for _, c := range cert.configs {
+		if c == cfg {
+			found = true
+			break
+		}
+	}
+	if !found {
+		cert.configs = append(cert.configs, cfg)
+	}
+
+	// key the certificate by all its names for this config only,
+	// this is how we find the certificate during handshakes
+	// (yes, if certs overlap in the names they serve, one will
+	// overwrite another here, but that's just how it goes)
+	for _, name := range cert.Names {
+		cfg.Certificates[name] = cert.Hash
+	}
+
+	// store the certificate
+	cfg.certCache.cache[cert.Hash] = cert
+
+	return cert
+}