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advancedtls.go
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advancedtls.go
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/*
*
* Copyright 2019 gRPC authors.
*
* 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 advancedtls is a utility library containing functions to construct
// credentials.TransportCredentials that can perform credential reloading and
// custom verification check.
package advancedtls
import (
"context"
"crypto/tls"
"crypto/x509"
"fmt"
"net"
"net/url"
"reflect"
"syscall"
"time"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/credentials/tls/certprovider"
credinternal "google.golang.org/grpc/internal/credentials"
)
// VerificationFuncParams contains parameters available to users when
// implementing CustomVerificationFunc.
// The fields in this struct are read-only.
type VerificationFuncParams struct {
// The target server name that the client connects to when establishing the
// connection. This field is only meaningful for client side. On server side,
// this field would be an empty string.
ServerName string
// The raw certificates sent from peer.
RawCerts [][]byte
// The verification chain obtained by checking peer RawCerts against the
// trust certificate bundle(s), if applicable.
VerifiedChains [][]*x509.Certificate
// The leaf certificate sent from peer, if choosing to verify the peer
// certificate(s) and that verification passed. This field would be nil if
// either user chose not to verify or the verification failed.
Leaf *x509.Certificate
// The connection information stored during the verification.
RawConn net.Conn
// The SPIFFE ID stored in |State|.
SPIFFEID *url.URL
}
// VerificationResults contains the information about results of
// CustomVerificationFunc.
// VerificationResults is an empty struct for now. It may be extended in the
// future to include more information.
type VerificationResults struct{}
// CustomVerificationFunc is the function defined by users to perform custom
// verification check.
// CustomVerificationFunc returns nil if the authorization fails; otherwise
// returns an empty struct.
type CustomVerificationFunc func(params *VerificationFuncParams) (*VerificationResults, error)
// GetRootCAsParams contains the parameters available to users when
// implementing GetRootCAs.
type GetRootCAsParams struct {
RawConn net.Conn
RawCerts [][]byte
}
// GetRootCAsResults contains the results of GetRootCAs.
// If users want to reload the root trust certificate, it is required to return
// the proper TrustCerts in GetRootCAs.
type GetRootCAsResults struct {
TrustCerts *x509.CertPool
}
// RootCertificateOptions contains options to obtain root trust certificates
// for both the client and the server.
// At most one option could be set. If none of them are set, we
// use the system default trust certificates.
type RootCertificateOptions struct {
// If RootCACerts is set, it will be used every time when verifying
// the peer certificates, without performing root certificate reloading.
RootCACerts *x509.CertPool
// If GetRootCertificates is set, it will be invoked to obtain root certs for
// every new connection.
GetRootCertificates func(params *GetRootCAsParams) (*GetRootCAsResults, error)
// If RootProvider is set, we will use the root certs from the Provider's
// KeyMaterial() call in the new connections. The Provider must have initial
// credentials if specified. Otherwise, KeyMaterial() will block forever.
RootProvider certprovider.Provider
}
// nonNilFieldCount returns the number of set fields in RootCertificateOptions.
func (o RootCertificateOptions) nonNilFieldCount() int {
cnt := 0
rv := reflect.ValueOf(o)
for i := 0; i < rv.NumField(); i++ {
if !rv.Field(i).IsNil() {
cnt++
}
}
return cnt
}
// IdentityCertificateOptions contains options to obtain identity certificates
// for both the client and the server.
// At most one option could be set.
type IdentityCertificateOptions struct {
// If Certificates is set, it will be used every time when needed to present
//identity certificates, without performing identity certificate reloading.
Certificates []tls.Certificate
// If GetIdentityCertificatesForClient is set, it will be invoked to obtain
// identity certs for every new connection.
// This field MUST be set on client side.
GetIdentityCertificatesForClient func(*tls.CertificateRequestInfo) (*tls.Certificate, error)
// If GetIdentityCertificatesForServer is set, it will be invoked to obtain
// identity certs for every new connection.
// This field MUST be set on server side.
GetIdentityCertificatesForServer func(*tls.ClientHelloInfo) ([]*tls.Certificate, error)
// If IdentityProvider is set, we will use the identity certs from the
// Provider's KeyMaterial() call in the new connections. The Provider must
// have initial credentials if specified. Otherwise, KeyMaterial() will block
// forever.
IdentityProvider certprovider.Provider
}
// nonNilFieldCount returns the number of set fields in IdentityCertificateOptions.
func (o IdentityCertificateOptions) nonNilFieldCount() int {
cnt := 0
rv := reflect.ValueOf(o)
for i := 0; i < rv.NumField(); i++ {
if !rv.Field(i).IsNil() {
cnt++
}
}
return cnt
}
// VerificationType is the enum type that represents different levels of
// verification users could set, both on client side and on server side.
type VerificationType int
const (
// CertAndHostVerification indicates doing both certificate signature check
// and hostname check.
CertAndHostVerification VerificationType = iota
// CertVerification indicates doing certificate signature check only. Setting
// this field without proper custom verification check would leave the
// application susceptible to the MITM attack.
CertVerification
// SkipVerification indicates skipping both certificate signature check and
// hostname check. If setting this field, proper custom verification needs to
// be implemented in order to complete the authentication. Setting this field
// with a nil custom verification would raise an error.
SkipVerification
)
// ClientOptions contains the fields needed to be filled by the client.
type ClientOptions struct {
// IdentityOptions is OPTIONAL on client side. This field only needs to be
// set if mutual authentication is required on server side.
IdentityOptions IdentityCertificateOptions
// VerifyPeer is a custom verification check after certificate signature
// check.
// If this is set, we will perform this customized check after doing the
// normal check(s) indicated by setting VType.
VerifyPeer CustomVerificationFunc
// ServerNameOverride is for testing only. If set to a non-empty string,
// it will override the virtual host name of authority (e.g. :authority
// header field) in requests.
ServerNameOverride string
// RootOptions is OPTIONAL on client side. If not set, we will try to use the
// default trust certificates in users' OS system.
RootOptions RootCertificateOptions
// VType is the verification type on the client side.
VType VerificationType
}
// ServerOptions contains the fields needed to be filled by the server.
type ServerOptions struct {
// IdentityOptions is REQUIRED on server side.
IdentityOptions IdentityCertificateOptions
// VerifyPeer is a custom verification check after certificate signature
// check.
// If this is set, we will perform this customized check after doing the
// normal check(s) indicated by setting VType.
VerifyPeer CustomVerificationFunc
// RootOptions is OPTIONAL on server side. This field only needs to be set if
// mutual authentication is required(RequireClientCert is true).
RootOptions RootCertificateOptions
// If the server want the client to send certificates.
RequireClientCert bool
// VType is the verification type on the server side.
VType VerificationType
}
func (o *ClientOptions) config() (*tls.Config, error) {
if o.VType == SkipVerification && o.VerifyPeer == nil {
return nil, fmt.Errorf("client needs to provide custom verification mechanism if choose to skip default verification")
}
// Make sure users didn't specify more than one fields in
// RootCertificateOptions and IdentityCertificateOptions.
if num := o.RootOptions.nonNilFieldCount(); num > 1 {
return nil, fmt.Errorf("at most one field in RootCertificateOptions could be specified")
}
if num := o.IdentityOptions.nonNilFieldCount(); num > 1 {
return nil, fmt.Errorf("at most one field in IdentityCertificateOptions could be specified")
}
if o.IdentityOptions.GetIdentityCertificatesForServer != nil {
return nil, fmt.Errorf("GetIdentityCertificatesForServer cannot be specified on the client side")
}
config := &tls.Config{
ServerName: o.ServerNameOverride,
// We have to set InsecureSkipVerify to true to skip the default checks and
// use the verification function we built from buildVerifyFunc.
InsecureSkipVerify: true,
}
// Propagate root-certificate-related fields in tls.Config.
switch {
case o.RootOptions.RootCACerts != nil:
config.RootCAs = o.RootOptions.RootCACerts
case o.RootOptions.GetRootCertificates != nil:
// In cases when users provide GetRootCertificates callback, since this
// callback is not contained in tls.Config, we have nothing to set here.
// We will invoke the callback in ClientHandshake.
case o.RootOptions.RootProvider != nil:
o.RootOptions.GetRootCertificates = func(*GetRootCAsParams) (*GetRootCAsResults, error) {
km, err := o.RootOptions.RootProvider.KeyMaterial(context.Background())
if err != nil {
return nil, err
}
return &GetRootCAsResults{TrustCerts: km.Roots}, nil
}
default:
// No root certificate options specified by user. Use the certificates
// stored in system default path as the last resort.
if o.VType != SkipVerification {
systemRootCAs, err := x509.SystemCertPool()
if err != nil {
return nil, err
}
config.RootCAs = systemRootCAs
}
}
// Propagate identity-certificate-related fields in tls.Config.
switch {
case o.IdentityOptions.Certificates != nil:
config.Certificates = o.IdentityOptions.Certificates
case o.IdentityOptions.GetIdentityCertificatesForClient != nil:
config.GetClientCertificate = o.IdentityOptions.GetIdentityCertificatesForClient
case o.IdentityOptions.IdentityProvider != nil:
config.GetClientCertificate = func(*tls.CertificateRequestInfo) (*tls.Certificate, error) {
km, err := o.IdentityOptions.IdentityProvider.KeyMaterial(context.Background())
if err != nil {
return nil, err
}
if len(km.Certs) != 1 {
return nil, fmt.Errorf("there should always be only one identity cert chain on the client side in IdentityProvider")
}
return &km.Certs[0], nil
}
default:
// It's fine for users to not specify identity certificate options here.
}
return config, nil
}
func (o *ServerOptions) config() (*tls.Config, error) {
if o.RequireClientCert && o.VType == SkipVerification && o.VerifyPeer == nil {
return nil, fmt.Errorf("server needs to provide custom verification mechanism if choose to skip default verification, but require client certificate(s)")
}
// Make sure users didn't specify more than one fields in
// RootCertificateOptions and IdentityCertificateOptions.
if num := o.RootOptions.nonNilFieldCount(); num > 1 {
return nil, fmt.Errorf("at most one field in RootCertificateOptions could be specified")
}
if num := o.IdentityOptions.nonNilFieldCount(); num > 1 {
return nil, fmt.Errorf("at most one field in IdentityCertificateOptions could be specified")
}
if o.IdentityOptions.GetIdentityCertificatesForClient != nil {
return nil, fmt.Errorf("GetIdentityCertificatesForClient cannot be specified on the server side")
}
clientAuth := tls.NoClientCert
if o.RequireClientCert {
// We have to set clientAuth to RequireAnyClientCert to force underlying
// TLS package to use the verification function we built from
// buildVerifyFunc.
clientAuth = tls.RequireAnyClientCert
}
config := &tls.Config{
ClientAuth: clientAuth,
}
// Propagate root-certificate-related fields in tls.Config.
switch {
case o.RootOptions.RootCACerts != nil:
config.ClientCAs = o.RootOptions.RootCACerts
case o.RootOptions.GetRootCertificates != nil:
// In cases when users provide GetRootCertificates callback, since this
// callback is not contained in tls.Config, we have nothing to set here.
// We will invoke the callback in ServerHandshake.
case o.RootOptions.RootProvider != nil:
o.RootOptions.GetRootCertificates = func(*GetRootCAsParams) (*GetRootCAsResults, error) {
km, err := o.RootOptions.RootProvider.KeyMaterial(context.Background())
if err != nil {
return nil, err
}
return &GetRootCAsResults{TrustCerts: km.Roots}, nil
}
default:
// No root certificate options specified by user. Use the certificates
// stored in system default path as the last resort.
if o.VType != SkipVerification && o.RequireClientCert {
systemRootCAs, err := x509.SystemCertPool()
if err != nil {
return nil, err
}
config.ClientCAs = systemRootCAs
}
}
// Propagate identity-certificate-related fields in tls.Config.
switch {
case o.IdentityOptions.Certificates != nil:
config.Certificates = o.IdentityOptions.Certificates
case o.IdentityOptions.GetIdentityCertificatesForServer != nil:
config.GetCertificate = func(clientHello *tls.ClientHelloInfo) (*tls.Certificate, error) {
return buildGetCertificates(clientHello, o)
}
case o.IdentityOptions.IdentityProvider != nil:
o.IdentityOptions.GetIdentityCertificatesForServer = func(*tls.ClientHelloInfo) ([]*tls.Certificate, error) {
km, err := o.IdentityOptions.IdentityProvider.KeyMaterial(context.Background())
if err != nil {
return nil, err
}
var certChains []*tls.Certificate
for i := 0; i < len(km.Certs); i++ {
certChains = append(certChains, &km.Certs[i])
}
return certChains, nil
}
config.GetCertificate = func(clientHello *tls.ClientHelloInfo) (*tls.Certificate, error) {
return buildGetCertificates(clientHello, o)
}
default:
return nil, fmt.Errorf("needs to specify at least one field in IdentityCertificateOptions")
}
return config, nil
}
// advancedTLSCreds is the credentials required for authenticating a connection
// using TLS.
type advancedTLSCreds struct {
config *tls.Config
verifyFunc CustomVerificationFunc
getRootCAs func(params *GetRootCAsParams) (*GetRootCAsResults, error)
isClient bool
vType VerificationType
}
func (c advancedTLSCreds) Info() credentials.ProtocolInfo {
return credentials.ProtocolInfo{
SecurityProtocol: "tls",
SecurityVersion: "1.2",
ServerName: c.config.ServerName,
}
}
func (c *advancedTLSCreds) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
// Use local cfg to avoid clobbering ServerName if using multiple endpoints.
cfg := cloneTLSConfig(c.config)
// We return the full authority name to users if ServerName is empty without
// stripping the trailing port.
if cfg.ServerName == "" {
cfg.ServerName = authority
}
cfg.VerifyPeerCertificate = buildVerifyFunc(c, cfg.ServerName, rawConn)
conn := tls.Client(rawConn, cfg)
errChannel := make(chan error, 1)
go func() {
errChannel <- conn.Handshake()
close(errChannel)
}()
select {
case err := <-errChannel:
if err != nil {
conn.Close()
return nil, nil, err
}
case <-ctx.Done():
conn.Close()
return nil, nil, ctx.Err()
}
info := credentials.TLSInfo{
State: conn.ConnectionState(),
CommonAuthInfo: credentials.CommonAuthInfo{
SecurityLevel: credentials.PrivacyAndIntegrity,
},
}
info.SPIFFEID = credinternal.SPIFFEIDFromState(conn.ConnectionState())
return WrapSyscallConn(rawConn, conn), info, nil
}
func (c *advancedTLSCreds) ServerHandshake(rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
cfg := cloneTLSConfig(c.config)
cfg.VerifyPeerCertificate = buildVerifyFunc(c, "", rawConn)
conn := tls.Server(rawConn, cfg)
if err := conn.Handshake(); err != nil {
conn.Close()
return nil, nil, err
}
info := credentials.TLSInfo{
State: conn.ConnectionState(),
CommonAuthInfo: credentials.CommonAuthInfo{
SecurityLevel: credentials.PrivacyAndIntegrity,
},
}
info.SPIFFEID = credinternal.SPIFFEIDFromState(conn.ConnectionState())
return WrapSyscallConn(rawConn, conn), info, nil
}
func (c *advancedTLSCreds) Clone() credentials.TransportCredentials {
return &advancedTLSCreds{
config: cloneTLSConfig(c.config),
verifyFunc: c.verifyFunc,
getRootCAs: c.getRootCAs,
isClient: c.isClient,
}
}
func (c *advancedTLSCreds) OverrideServerName(serverNameOverride string) error {
c.config.ServerName = serverNameOverride
return nil
}
// The function buildVerifyFunc is used when users want root cert reloading,
// and possibly custom verification check.
// We have to build our own verification function here because current
// tls module:
// 1. does not have a good support on root cert reloading.
// 2. will ignore basic certificate check when setting InsecureSkipVerify
// to true.
func buildVerifyFunc(c *advancedTLSCreds,
serverName string,
rawConn net.Conn) func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
return func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error {
chains := verifiedChains
var leafCert *x509.Certificate
if c.vType == CertAndHostVerification || c.vType == CertVerification {
// perform possible trust credential reloading and certificate check
rootCAs := c.config.RootCAs
if !c.isClient {
rootCAs = c.config.ClientCAs
}
// Reload root CA certs.
if rootCAs == nil && c.getRootCAs != nil {
results, err := c.getRootCAs(&GetRootCAsParams{
RawConn: rawConn,
RawCerts: rawCerts,
})
if err != nil {
return err
}
rootCAs = results.TrustCerts
}
// Verify peers' certificates against RootCAs and get verifiedChains.
certs := make([]*x509.Certificate, len(rawCerts))
for i, asn1Data := range rawCerts {
cert, err := x509.ParseCertificate(asn1Data)
if err != nil {
return err
}
certs[i] = cert
}
keyUsages := []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}
if !c.isClient {
keyUsages = []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth}
}
opts := x509.VerifyOptions{
Roots: rootCAs,
CurrentTime: time.Now(),
Intermediates: x509.NewCertPool(),
KeyUsages: keyUsages,
}
for _, cert := range certs[1:] {
opts.Intermediates.AddCert(cert)
}
// Perform default hostname check if specified.
if c.isClient && c.vType == CertAndHostVerification && serverName != "" {
opts.DNSName = serverName
}
var err error
chains, err = certs[0].Verify(opts)
if err != nil {
return err
}
leafCert = certs[0]
}
if c.verifyFunc != nil {
_, err := c.verifyFunc(&VerificationFuncParams{
ServerName: serverName,
RawCerts: rawCerts,
VerifiedChains: chains,
Leaf: leafCert,
RawConn: rawConn,
SPIFFEID: credinternal.SPIFFEIDFromCert(leafCert),
})
return err
}
return nil
}
}
// NewClientCreds uses ClientOptions to construct a TransportCredentials based
// on TLS.
func NewClientCreds(o *ClientOptions) (credentials.TransportCredentials, error) {
conf, err := o.config()
if err != nil {
return nil, err
}
tc := &advancedTLSCreds{
config: conf,
isClient: true,
getRootCAs: o.RootOptions.GetRootCertificates,
verifyFunc: o.VerifyPeer,
vType: o.VType,
}
tc.config.NextProtos = appendH2ToNextProtos(tc.config.NextProtos)
return tc, nil
}
// NewServerCreds uses ServerOptions to construct a TransportCredentials based
// on TLS.
func NewServerCreds(o *ServerOptions) (credentials.TransportCredentials, error) {
conf, err := o.config()
if err != nil {
return nil, err
}
tc := &advancedTLSCreds{
config: conf,
isClient: false,
getRootCAs: o.RootOptions.GetRootCertificates,
verifyFunc: o.VerifyPeer,
vType: o.VType,
}
tc.config.NextProtos = appendH2ToNextProtos(tc.config.NextProtos)
return tc, nil
}
// TODO(ZhenLian): The code below are duplicates with gRPC-Go under
// credentials/internal. Consider refactoring in the future.
const alpnProtoStrH2 = "h2"
func appendH2ToNextProtos(ps []string) []string {
for _, p := range ps {
if p == alpnProtoStrH2 {
return ps
}
}
ret := make([]string, 0, len(ps)+1)
ret = append(ret, ps...)
return append(ret, alpnProtoStrH2)
}
// We give syscall.Conn a new name here since syscall.Conn and net.Conn used
// below have the same names.
type sysConn = syscall.Conn
// syscallConn keeps reference of rawConn to support syscall.Conn for channelz.
// SyscallConn() (the method in interface syscall.Conn) is explicitly
// implemented on this type,
//
// Interface syscall.Conn is implemented by most net.Conn implementations (e.g.
// TCPConn, UnixConn), but is not part of net.Conn interface. So wrapper conns
// that embed net.Conn don't implement syscall.Conn. (Side note: tls.Conn
// doesn't embed net.Conn, so even if syscall.Conn is part of net.Conn, it won't
// help here).
type syscallConn struct {
net.Conn
// sysConn is a type alias of syscall.Conn. It's necessary because the name
// `Conn` collides with `net.Conn`.
sysConn
}
// WrapSyscallConn tries to wrap rawConn and newConn into a net.Conn that
// implements syscall.Conn. rawConn will be used to support syscall, and newConn
// will be used for read/write.
//
// This function returns newConn if rawConn doesn't implement syscall.Conn.
func WrapSyscallConn(rawConn, newConn net.Conn) net.Conn {
sysConn, ok := rawConn.(syscall.Conn)
if !ok {
return newConn
}
return &syscallConn{
Conn: newConn,
sysConn: sysConn,
}
}
func cloneTLSConfig(cfg *tls.Config) *tls.Config {
if cfg == nil {
return &tls.Config{}
}
return cfg.Clone()
}