413 lines
14 KiB
Go
413 lines
14 KiB
Go
/*
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*
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* Copyright 2021 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Package s2a provides the S2A transport credentials used by a gRPC
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// application.
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package s2a
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import (
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"context"
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"crypto/tls"
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"errors"
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"fmt"
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"net"
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"sync"
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"time"
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"github.com/golang/protobuf/proto"
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"github.com/google/s2a-go/fallback"
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"github.com/google/s2a-go/internal/handshaker"
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"github.com/google/s2a-go/internal/handshaker/service"
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"github.com/google/s2a-go/internal/tokenmanager"
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"github.com/google/s2a-go/internal/v2"
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"google.golang.org/grpc/credentials"
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"google.golang.org/grpc/grpclog"
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commonpb "github.com/google/s2a-go/internal/proto/common_go_proto"
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s2av2pb "github.com/google/s2a-go/internal/proto/v2/s2a_go_proto"
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)
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const (
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s2aSecurityProtocol = "tls"
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// defaultTimeout specifies the default server handshake timeout.
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defaultTimeout = 30.0 * time.Second
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)
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// s2aTransportCreds are the transport credentials required for establishing
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// a secure connection using the S2A. They implement the
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// credentials.TransportCredentials interface.
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type s2aTransportCreds struct {
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info *credentials.ProtocolInfo
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minTLSVersion commonpb.TLSVersion
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maxTLSVersion commonpb.TLSVersion
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// tlsCiphersuites contains the ciphersuites used in the S2A connection.
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// Note that these are currently unconfigurable.
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tlsCiphersuites []commonpb.Ciphersuite
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// localIdentity should only be used by the client.
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localIdentity *commonpb.Identity
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// localIdentities should only be used by the server.
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localIdentities []*commonpb.Identity
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// targetIdentities should only be used by the client.
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targetIdentities []*commonpb.Identity
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isClient bool
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s2aAddr string
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ensureProcessSessionTickets *sync.WaitGroup
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}
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// NewClientCreds returns a client-side transport credentials object that uses
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// the S2A to establish a secure connection with a server.
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func NewClientCreds(opts *ClientOptions) (credentials.TransportCredentials, error) {
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if opts == nil {
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return nil, errors.New("nil client options")
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}
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var targetIdentities []*commonpb.Identity
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for _, targetIdentity := range opts.TargetIdentities {
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protoTargetIdentity, err := toProtoIdentity(targetIdentity)
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if err != nil {
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return nil, err
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}
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targetIdentities = append(targetIdentities, protoTargetIdentity)
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}
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localIdentity, err := toProtoIdentity(opts.LocalIdentity)
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if err != nil {
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return nil, err
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}
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if opts.EnableLegacyMode {
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return &s2aTransportCreds{
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info: &credentials.ProtocolInfo{
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SecurityProtocol: s2aSecurityProtocol,
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},
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minTLSVersion: commonpb.TLSVersion_TLS1_3,
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maxTLSVersion: commonpb.TLSVersion_TLS1_3,
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tlsCiphersuites: []commonpb.Ciphersuite{
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commonpb.Ciphersuite_AES_128_GCM_SHA256,
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commonpb.Ciphersuite_AES_256_GCM_SHA384,
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commonpb.Ciphersuite_CHACHA20_POLY1305_SHA256,
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},
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localIdentity: localIdentity,
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targetIdentities: targetIdentities,
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isClient: true,
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s2aAddr: opts.S2AAddress,
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ensureProcessSessionTickets: opts.EnsureProcessSessionTickets,
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}, nil
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}
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verificationMode := getVerificationMode(opts.VerificationMode)
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var fallbackFunc fallback.ClientHandshake
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if opts.FallbackOpts != nil && opts.FallbackOpts.FallbackClientHandshakeFunc != nil {
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fallbackFunc = opts.FallbackOpts.FallbackClientHandshakeFunc
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}
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return v2.NewClientCreds(opts.S2AAddress, localIdentity, verificationMode, fallbackFunc, opts.getS2AStream, opts.serverAuthorizationPolicy)
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}
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// NewServerCreds returns a server-side transport credentials object that uses
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// the S2A to establish a secure connection with a client.
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func NewServerCreds(opts *ServerOptions) (credentials.TransportCredentials, error) {
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if opts == nil {
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return nil, errors.New("nil server options")
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}
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var localIdentities []*commonpb.Identity
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for _, localIdentity := range opts.LocalIdentities {
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protoLocalIdentity, err := toProtoIdentity(localIdentity)
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if err != nil {
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return nil, err
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}
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localIdentities = append(localIdentities, protoLocalIdentity)
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}
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if opts.EnableLegacyMode {
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return &s2aTransportCreds{
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info: &credentials.ProtocolInfo{
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SecurityProtocol: s2aSecurityProtocol,
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},
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minTLSVersion: commonpb.TLSVersion_TLS1_3,
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maxTLSVersion: commonpb.TLSVersion_TLS1_3,
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tlsCiphersuites: []commonpb.Ciphersuite{
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commonpb.Ciphersuite_AES_128_GCM_SHA256,
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commonpb.Ciphersuite_AES_256_GCM_SHA384,
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commonpb.Ciphersuite_CHACHA20_POLY1305_SHA256,
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},
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localIdentities: localIdentities,
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isClient: false,
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s2aAddr: opts.S2AAddress,
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}, nil
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}
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verificationMode := getVerificationMode(opts.VerificationMode)
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return v2.NewServerCreds(opts.S2AAddress, localIdentities, verificationMode, opts.getS2AStream)
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}
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// ClientHandshake initiates a client-side TLS handshake using the S2A.
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func (c *s2aTransportCreds) ClientHandshake(ctx context.Context, serverAuthority string, rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
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if !c.isClient {
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return nil, nil, errors.New("client handshake called using server transport credentials")
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}
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// Connect to the S2A.
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hsConn, err := service.Dial(c.s2aAddr)
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if err != nil {
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grpclog.Infof("Failed to connect to S2A: %v", err)
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return nil, nil, err
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}
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var cancel context.CancelFunc
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ctx, cancel = context.WithCancel(ctx)
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defer cancel()
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opts := &handshaker.ClientHandshakerOptions{
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MinTLSVersion: c.minTLSVersion,
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MaxTLSVersion: c.maxTLSVersion,
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TLSCiphersuites: c.tlsCiphersuites,
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TargetIdentities: c.targetIdentities,
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LocalIdentity: c.localIdentity,
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TargetName: serverAuthority,
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EnsureProcessSessionTickets: c.ensureProcessSessionTickets,
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}
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chs, err := handshaker.NewClientHandshaker(ctx, hsConn, rawConn, c.s2aAddr, opts)
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if err != nil {
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grpclog.Infof("Call to handshaker.NewClientHandshaker failed: %v", err)
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return nil, nil, err
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}
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defer func() {
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if err != nil {
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if closeErr := chs.Close(); closeErr != nil {
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grpclog.Infof("Close failed unexpectedly: %v", err)
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err = fmt.Errorf("%v: close unexpectedly failed: %v", err, closeErr)
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}
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}
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}()
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secConn, authInfo, err := chs.ClientHandshake(context.Background())
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if err != nil {
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grpclog.Infof("Handshake failed: %v", err)
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return nil, nil, err
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}
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return secConn, authInfo, nil
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}
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// ServerHandshake initiates a server-side TLS handshake using the S2A.
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func (c *s2aTransportCreds) ServerHandshake(rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
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if c.isClient {
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return nil, nil, errors.New("server handshake called using client transport credentials")
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}
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// Connect to the S2A.
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hsConn, err := service.Dial(c.s2aAddr)
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if err != nil {
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grpclog.Infof("Failed to connect to S2A: %v", err)
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return nil, nil, err
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}
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ctx, cancel := context.WithTimeout(context.Background(), defaultTimeout)
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defer cancel()
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opts := &handshaker.ServerHandshakerOptions{
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MinTLSVersion: c.minTLSVersion,
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MaxTLSVersion: c.maxTLSVersion,
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TLSCiphersuites: c.tlsCiphersuites,
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LocalIdentities: c.localIdentities,
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}
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shs, err := handshaker.NewServerHandshaker(ctx, hsConn, rawConn, c.s2aAddr, opts)
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if err != nil {
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grpclog.Infof("Call to handshaker.NewServerHandshaker failed: %v", err)
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return nil, nil, err
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}
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defer func() {
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if err != nil {
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if closeErr := shs.Close(); closeErr != nil {
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grpclog.Infof("Close failed unexpectedly: %v", err)
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err = fmt.Errorf("%v: close unexpectedly failed: %v", err, closeErr)
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}
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}
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}()
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secConn, authInfo, err := shs.ServerHandshake(context.Background())
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if err != nil {
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grpclog.Infof("Handshake failed: %v", err)
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return nil, nil, err
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}
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return secConn, authInfo, nil
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}
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func (c *s2aTransportCreds) Info() credentials.ProtocolInfo {
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return *c.info
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}
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func (c *s2aTransportCreds) Clone() credentials.TransportCredentials {
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info := *c.info
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var localIdentity *commonpb.Identity
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if c.localIdentity != nil {
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localIdentity = proto.Clone(c.localIdentity).(*commonpb.Identity)
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}
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var localIdentities []*commonpb.Identity
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if c.localIdentities != nil {
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localIdentities = make([]*commonpb.Identity, len(c.localIdentities))
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for i, localIdentity := range c.localIdentities {
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localIdentities[i] = proto.Clone(localIdentity).(*commonpb.Identity)
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}
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}
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var targetIdentities []*commonpb.Identity
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if c.targetIdentities != nil {
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targetIdentities = make([]*commonpb.Identity, len(c.targetIdentities))
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for i, targetIdentity := range c.targetIdentities {
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targetIdentities[i] = proto.Clone(targetIdentity).(*commonpb.Identity)
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}
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}
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return &s2aTransportCreds{
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info: &info,
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minTLSVersion: c.minTLSVersion,
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maxTLSVersion: c.maxTLSVersion,
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tlsCiphersuites: c.tlsCiphersuites,
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localIdentity: localIdentity,
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localIdentities: localIdentities,
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targetIdentities: targetIdentities,
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isClient: c.isClient,
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s2aAddr: c.s2aAddr,
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}
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}
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func (c *s2aTransportCreds) OverrideServerName(serverNameOverride string) error {
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c.info.ServerName = serverNameOverride
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return nil
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}
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// TLSClientConfigOptions specifies parameters for creating client TLS config.
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type TLSClientConfigOptions struct {
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// ServerName is required by s2a as the expected name when verifying the hostname found in server's certificate.
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// tlsConfig, _ := factory.Build(ctx, &s2a.TLSClientConfigOptions{
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// ServerName: "example.com",
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// })
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ServerName string
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}
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// TLSClientConfigFactory defines the interface for a client TLS config factory.
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type TLSClientConfigFactory interface {
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Build(ctx context.Context, opts *TLSClientConfigOptions) (*tls.Config, error)
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}
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// NewTLSClientConfigFactory returns an instance of s2aTLSClientConfigFactory.
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func NewTLSClientConfigFactory(opts *ClientOptions) (TLSClientConfigFactory, error) {
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if opts == nil {
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return nil, fmt.Errorf("opts must be non-nil")
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}
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if opts.EnableLegacyMode {
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return nil, fmt.Errorf("NewTLSClientConfigFactory only supports S2Av2")
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}
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tokenManager, err := tokenmanager.NewSingleTokenAccessTokenManager()
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if err != nil {
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// The only possible error is: access token not set in the environment,
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// which is okay in environments other than serverless.
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grpclog.Infof("Access token manager not initialized: %v", err)
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return &s2aTLSClientConfigFactory{
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s2av2Address: opts.S2AAddress,
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tokenManager: nil,
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verificationMode: getVerificationMode(opts.VerificationMode),
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serverAuthorizationPolicy: opts.serverAuthorizationPolicy,
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}, nil
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}
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return &s2aTLSClientConfigFactory{
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s2av2Address: opts.S2AAddress,
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tokenManager: tokenManager,
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verificationMode: getVerificationMode(opts.VerificationMode),
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serverAuthorizationPolicy: opts.serverAuthorizationPolicy,
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}, nil
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}
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type s2aTLSClientConfigFactory struct {
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s2av2Address string
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tokenManager tokenmanager.AccessTokenManager
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verificationMode s2av2pb.ValidatePeerCertificateChainReq_VerificationMode
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serverAuthorizationPolicy []byte
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}
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func (f *s2aTLSClientConfigFactory) Build(
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ctx context.Context, opts *TLSClientConfigOptions) (*tls.Config, error) {
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serverName := ""
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if opts != nil && opts.ServerName != "" {
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serverName = opts.ServerName
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}
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return v2.NewClientTLSConfig(ctx, f.s2av2Address, f.tokenManager, f.verificationMode, serverName, f.serverAuthorizationPolicy)
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}
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func getVerificationMode(verificationMode VerificationModeType) s2av2pb.ValidatePeerCertificateChainReq_VerificationMode {
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switch verificationMode {
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case ConnectToGoogle:
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return s2av2pb.ValidatePeerCertificateChainReq_CONNECT_TO_GOOGLE
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case Spiffe:
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return s2av2pb.ValidatePeerCertificateChainReq_SPIFFE
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default:
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return s2av2pb.ValidatePeerCertificateChainReq_UNSPECIFIED
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}
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}
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// NewS2ADialTLSContextFunc returns a dialer which establishes an MTLS connection using S2A.
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// Example use with http.RoundTripper:
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//
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// dialTLSContext := s2a.NewS2aDialTLSContextFunc(&s2a.ClientOptions{
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// S2AAddress: s2aAddress, // required
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// })
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// transport := http.DefaultTransport
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// transport.DialTLSContext = dialTLSContext
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func NewS2ADialTLSContextFunc(opts *ClientOptions) func(ctx context.Context, network, addr string) (net.Conn, error) {
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return func(ctx context.Context, network, addr string) (net.Conn, error) {
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fallback := func(err error) (net.Conn, error) {
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if opts.FallbackOpts != nil && opts.FallbackOpts.FallbackDialer != nil &&
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opts.FallbackOpts.FallbackDialer.Dialer != nil && opts.FallbackOpts.FallbackDialer.ServerAddr != "" {
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fbDialer := opts.FallbackOpts.FallbackDialer
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grpclog.Infof("fall back to dial: %s", fbDialer.ServerAddr)
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fbConn, fbErr := fbDialer.Dialer.DialContext(ctx, network, fbDialer.ServerAddr)
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if fbErr != nil {
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return nil, fmt.Errorf("error fallback to %s: %v; S2A error: %w", fbDialer.ServerAddr, fbErr, err)
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}
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return fbConn, nil
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}
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return nil, err
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}
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factory, err := NewTLSClientConfigFactory(opts)
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if err != nil {
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grpclog.Infof("error creating S2A client config factory: %v", err)
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return fallback(err)
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}
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serverName, _, err := net.SplitHostPort(addr)
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if err != nil {
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serverName = addr
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}
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timeoutCtx, cancel := context.WithTimeout(ctx, v2.GetS2ATimeout())
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defer cancel()
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s2aTLSConfig, err := factory.Build(timeoutCtx, &TLSClientConfigOptions{
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ServerName: serverName,
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})
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if err != nil {
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grpclog.Infof("error building S2A TLS config: %v", err)
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return fallback(err)
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}
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s2aDialer := &tls.Dialer{
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Config: s2aTLSConfig,
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}
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c, err := s2aDialer.DialContext(ctx, network, addr)
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if err != nil {
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grpclog.Infof("error dialing with S2A to %s: %v", addr, err)
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return fallback(err)
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}
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grpclog.Infof("success dialing MTLS to %s with S2A", addr)
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return c, nil
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}
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}
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