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Copy pathcerts.go
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346 lines (319 loc) · 11.5 KB
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/*
* MinIO Cloud Storage, (C) 2018 MinIO, Inc.
*
* 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 certs
import (
"context"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"os"
"path/filepath"
"sync"
"time"
"github.com/rjeczalik/notify"
)
// LoadX509KeyPairFunc is a function that parses a private key and
// certificate file and returns a TLS certificate on success.
type LoadX509KeyPairFunc func(certFile, keyFile string) (tls.Certificate, error)
// GetCertificateFunc is a callback that allows a TLS stack deliver different
// certificates based on the client trying to establish a TLS connection.
//
// For example, a GetCertificateFunc can return different TLS certificates depending
// upon the TLS SNI sent by the client.
type GetCertificateFunc func(hello *tls.ClientHelloInfo) (*tls.Certificate, error)
// Manager is a TLS certificate manager that can handle multiple certificates.
// When a client tries to establish a TLS connection, Manager will try to
// pick a certificate that can be validated by the client.
//
// For instance, if the client specifies a TLS SNI then Manager will try to
// find the corresponding certificate. If there is no such certificate it
// will fallback to the certificate named public.crt.
//
// Manager will automatically reload certificates if the corresponding file changes.
type Manager struct {
lock sync.RWMutex
certificates map[pair]*tls.Certificate // Mapping: certificate file name => TLS certificates
defaultCert pair
loadX509KeyPair LoadX509KeyPairFunc
events chan notify.EventInfo
ctx context.Context
}
// pair represents a certificate and private key file tuple.
type pair struct {
KeyFile string
CertFile string
}
// NewManager returns a new Manager that handles one certificate specified via
// the certFile and keyFile. It will use the loadX509KeyPair function to (re)load
// certificates.
//
// The certificate loaded from certFile is considered the default certificate.
// If a client does not send the TLS SNI extension then Manager will return
// this certificate.
func NewManager(ctx context.Context, certFile, keyFile string, loadX509KeyPair LoadX509KeyPairFunc) (manager *Manager, err error) {
certFile, err = filepath.Abs(certFile)
if err != nil {
return nil, err
}
keyFile, err = filepath.Abs(keyFile)
if err != nil {
return nil, err
}
manager = &Manager{
certificates: map[pair]*tls.Certificate{},
defaultCert: pair{
KeyFile: keyFile,
CertFile: certFile,
},
loadX509KeyPair: loadX509KeyPair,
events: make(chan notify.EventInfo, 1),
ctx: ctx,
}
if err := manager.AddCertificate(certFile, keyFile); err != nil {
return nil, err
}
go manager.watchFileEvents()
return manager, nil
}
// AddCertificate adds the TLS certificate in certFile resp. keyFile
// to the Manager.
//
// If there is already a certificate with the same base name it will be
// replaced by the newly added one.
func (m *Manager) AddCertificate(certFile, keyFile string) (err error) {
certFile, err = filepath.Abs(certFile)
if err != nil {
return err
}
keyFile, err = filepath.Abs(keyFile)
if err != nil {
return err
}
certFileIsLink, err := isSymlink(certFile)
if err != nil {
return err
}
keyFileIsLink, err := isSymlink(keyFile)
if err != nil {
return err
}
if certFileIsLink && !keyFileIsLink {
return fmt.Errorf("certs: '%s' is a symlink but '%s' is a regular file", certFile, keyFile)
}
if keyFileIsLink && !certFileIsLink {
return fmt.Errorf("certs: '%s' is a symlink but '%s' is a regular file", keyFile, certFile)
}
certificate, err := m.loadX509KeyPair(certFile, keyFile)
if err != nil {
return err
}
// We set the certificate leaf to the actual certificate such that
// we don't have to do the parsing (multiple times) when matching the
// certificate to the client hello. This a performance optimisation.
if certificate.Leaf == nil {
certificate.Leaf, err = x509.ParseCertificate(certificate.Certificate[0])
if err != nil {
return err
}
}
p := pair{
CertFile: certFile,
KeyFile: keyFile,
}
m.lock.Lock()
defer m.lock.Unlock()
// We don't allow IP SANs in certificates - except for the "default" certificate
// which is, by convention, the first certificate added to the manager. The problem
// with allowing IP SANs in more than one certificate is that the manager usually can't
// match the client SNI to a SAN since the SNI is meant to communicate the destination
// host name and clients will not set the SNI to an IP address.
// Allowing multiple certificates with IP SANs lead to errors that confuses users - like:
// "It works for `https://instance.minio.local` but not for `https://10.0.2.1`"
if len(m.certificates) > 0 && len(certificate.Leaf.IPAddresses) > 0 {
return errors.New("cert: certificate must not contain any IP SANs: only the default certificate may contain IP SANs")
}
m.certificates[p] = &certificate
if certFileIsLink && keyFileIsLink {
go m.watchSymlinks(certFile, keyFile)
} else {
// Windows doesn't allow for watching file changes but instead allows
// for directory changes only, while we can still watch for changes
// on files on other platforms. Watch parent directory on all platforms
// for simplicity.
if err = notify.Watch(filepath.Dir(certFile), m.events, eventWrite...); err != nil {
return err
}
if err = notify.Watch(filepath.Dir(keyFile), m.events, eventWrite...); err != nil {
return err
}
}
return nil
}
// watchSymlinks starts an endless loop reloading the
// certFile and keyFile periodically.
func (m *Manager) watchSymlinks(certFile, keyFile string) {
for {
select {
case <-m.ctx.Done():
return // Once stopped exits this routine.
case <-time.After(24 * time.Hour):
certificate, err := m.loadX509KeyPair(certFile, keyFile)
if err != nil {
continue
}
if certificate.Leaf == nil { // This is a performance optimisation
certificate.Leaf, err = x509.ParseCertificate(certificate.Certificate[0])
if err != nil {
continue
}
}
p := pair{
CertFile: certFile,
KeyFile: keyFile,
}
m.lock.Lock()
m.certificates[p] = &certificate
m.lock.Unlock()
}
}
}
// watchFileEvents starts an endless loop waiting for file systems events.
// Once an event occurs it reloads the private key and certificate that
// has changed, if any.
func (m *Manager) watchFileEvents() {
for {
select {
case <-m.ctx.Done():
return
case event := <-m.events:
if !isWriteEvent(event.Event()) {
continue
}
for pair := range m.certificates {
if p := event.Path(); pair.KeyFile == p || pair.CertFile == p {
certificate, err := m.loadX509KeyPair(pair.CertFile, pair.KeyFile)
if err != nil {
continue
}
if certificate.Leaf == nil { // This is performance optimisation
certificate.Leaf, err = x509.ParseCertificate(certificate.Certificate[0])
if err != nil {
continue
}
}
m.lock.Lock()
m.certificates[pair] = &certificate
m.lock.Unlock()
}
}
}
}
}
// GetCertificate returns a TLS certificate based on the client hello.
//
// It tries to find a certificate that would be accepted by the client
// according to the client hello. However, if no certificate can be
// found GetCertificate returns the certificate loaded from the
// Public file.
func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
m.lock.RLock()
defer m.lock.RUnlock()
// If the client does not send a SNI we return the "default"
// certificate. A client may not send a SNI - e.g. when trying
// to connect to an IP directly (https://<ip>:<port>).
//
// In this case we don't know which the certificate the client
// asks for. It may be a public-facing certificate issued by a
// public CA or an internal certificate containing internal domain
// names.
// Now, we should not serve "the first" certificate that would be
// accepted by the client based on the Client Hello. Otherwise, we
// may expose an internal certificate to the client that contains
// internal domain names. That way we would disclose internal
// infrastructure details.
//
// Therefore, we serve the "default" certificate - which by convention
// is the first certificate added to the Manager. It's the calling code's
// responsibility to ensure that the "public-facing" certificate is used
// when creating a Manager instance.
if hello.ServerName == "" {
certificate := m.certificates[m.defaultCert]
return certificate, nil
}
// Optimization: If there is just one certificate, always serve that one.
if len(m.certificates) == 1 {
for _, certificate := range m.certificates {
return certificate, nil
}
}
// Iterate over all certificates and return the first one that would
// be accepted by the peer (TLS client) based on the client hello.
// In particular, the client usually specifies the requested host/domain
// via SNI.
//
// Note: The certificate.Leaf should be non-nil and contain the actual
// client certificate of MinIO that should be presented to the peer (TLS client).
// Otherwise, the leaf certificate has to be parsed again - which is kind of
// expensive and may cause a performance issue. For more information, check the
// docs of tls.ClientHelloInfo.SupportsCertificate.
for _, certificate := range m.certificates {
if err := hello.SupportsCertificate(certificate); err == nil {
return certificate, nil
}
}
return nil, errors.New("certs: no server certificate is supported by peer")
}
// GetClientCertificate returns a TLS certificate for mTLS based on the
// certificate request.
//
// It tries to find a certificate that would be accepted by the server
// according to the certificate request. However, if no certificate can be
// found GetClientCertificate returns the certificate loaded from the
// Public file.
func (m *Manager) GetClientCertificate(reqInfo *tls.CertificateRequestInfo) (*tls.Certificate, error) {
m.lock.RLock()
defer m.lock.RUnlock()
// Optimization: If there is just one certificate, always serve that one.
if len(m.certificates) == 1 {
for _, certificate := range m.certificates {
return certificate, nil
}
}
// Iterate over all certificates and return the first one that would
// be accepted by the peer (TLS server) based on reqInfo.
//
// Note: The certificate.Leaf should be non-nil and contain the actual
// client certificate of MinIO that should be presented to the peer (TLS server).
// Otherwise, the leaf certificate has to be parsed again - which is kind of
// expensive and may cause a performance issue. For more information, check the
// docs of tls.CertificateRequestInfo.SupportsCertificate.
for _, certificate := range m.certificates {
if err := reqInfo.SupportsCertificate(certificate); err == nil {
return certificate, nil
}
}
return nil, errors.New("certs: no client certificate is supported by peer")
}
// isSymlink returns true if the given file
// is a symbolic link.
func isSymlink(file string) (bool, error) {
st, err := os.Lstat(file)
if err != nil {
return false, err
}
return st.Mode()&os.ModeSymlink == os.ModeSymlink, nil
}