vendor/google.golang.org/grpc/credentials/credentials.go - voltctl - Gitiles

 /*
  *
  * Copyright 2014 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 credentials implements various credentials supported by gRPC library,
 // which encapsulate all the state needed by a client to authenticate with a
 // server and make various assertions, e.g., about the client's identity, role,
 // or whether it is authorized to make a particular call.
 package credentials // import "google.golang.org/grpc/credentials"

 import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
 	"errors"
 	"fmt"
 	"io/ioutil"
 	"net"

 	"github.com/golang/protobuf/proto"

 	"google.golang.org/grpc/credentials/internal"
 	ginternal "google.golang.org/grpc/internal"
 )

 // PerRPCCredentials defines the common interface for the credentials which need to
 // attach security information to every RPC (e.g., oauth2).
 type PerRPCCredentials interface {
 	// GetRequestMetadata gets the current request metadata, refreshing
 	// tokens if required. This should be called by the transport layer on
 	// each request, and the data should be populated in headers or other
 	// context. If a status code is returned, it will be used as the status
 	// for the RPC. uri is the URI of the entry point for the request.
 	// When supported by the underlying implementation, ctx can be used for
 	// timeout and cancellation. Additionally, RequestInfo data will be
 	// available via ctx to this call.
 	// TODO(zhaoq): Define the set of the qualified keys instead of leaving
 	// it as an arbitrary string.
 	GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error)
 	// RequireTransportSecurity indicates whether the credentials requires
 	// transport security.
 	RequireTransportSecurity() bool
 }

 // ProtocolInfo provides information regarding the gRPC wire protocol version,
 // security protocol, security protocol version in use, server name, etc.
 type ProtocolInfo struct {
 	// ProtocolVersion is the gRPC wire protocol version.
 	ProtocolVersion string
 	// SecurityProtocol is the security protocol in use.
 	SecurityProtocol string
 	// SecurityVersion is the security protocol version.
 	SecurityVersion string
 	// ServerName is the user-configured server name.
 	ServerName string
 }

 // AuthInfo defines the common interface for the auth information the users are interested in.
 type AuthInfo interface {
 	AuthType() string
 }

 // ErrConnDispatched indicates that rawConn has been dispatched out of gRPC
 // and the caller should not close rawConn.
 var ErrConnDispatched = errors.New("credentials: rawConn is dispatched out of gRPC")

 // TransportCredentials defines the common interface for all the live gRPC wire
 // protocols and supported transport security protocols (e.g., TLS, SSL).
 type TransportCredentials interface {
 	// ClientHandshake does the authentication handshake specified by the corresponding
 	// authentication protocol on rawConn for clients. It returns the authenticated
 	// connection and the corresponding auth information about the connection.
 	// Implementations must use the provided context to implement timely cancellation.
 	// gRPC will try to reconnect if the error returned is a temporary error
 	// (io.EOF, context.DeadlineExceeded or err.Temporary() == true).
 	// If the returned error is a wrapper error, implementations should make sure that
 	// the error implements Temporary() to have the correct retry behaviors.
 	//
 	// If the returned net.Conn is closed, it MUST close the net.Conn provided.
 	ClientHandshake(context.Context, string, net.Conn) (net.Conn, AuthInfo, error)
 	// ServerHandshake does the authentication handshake for servers. It returns
 	// the authenticated connection and the corresponding auth information about
 	// the connection.
 	//
 	// If the returned net.Conn is closed, it MUST close the net.Conn provided.
 	ServerHandshake(net.Conn) (net.Conn, AuthInfo, error)
 	// Info provides the ProtocolInfo of this TransportCredentials.
 	Info() ProtocolInfo
 	// Clone makes a copy of this TransportCredentials.
 	Clone() TransportCredentials
 	// OverrideServerName overrides the server name used to verify the hostname on the returned certificates from the server.
 	// gRPC internals also use it to override the virtual hosting name if it is set.
 	// It must be called before dialing. Currently, this is only used by grpclb.
 	OverrideServerName(string) error
 }

 // Bundle is a combination of TransportCredentials and PerRPCCredentials.
 //
 // It also contains a mode switching method, so it can be used as a combination
 // of different credential policies.
 //
 // Bundle cannot be used together with individual TransportCredentials.
 // PerRPCCredentials from Bundle will be appended to other PerRPCCredentials.
 //
 // This API is experimental.
 type Bundle interface {
 	TransportCredentials() TransportCredentials
 	PerRPCCredentials() PerRPCCredentials
 	// NewWithMode should make a copy of Bundle, and switch mode. Modifying the
 	// existing Bundle may cause races.
 	//
 	// NewWithMode returns nil if the requested mode is not supported.
 	NewWithMode(mode string) (Bundle, error)
 }

 // TLSInfo contains the auth information for a TLS authenticated connection.
 // It implements the AuthInfo interface.
 type TLSInfo struct {
 	State tls.ConnectionState
 }

 // AuthType returns the type of TLSInfo as a string.
 func (t TLSInfo) AuthType() string {
 	return "tls"
 }

 // GetSecurityValue returns security info requested by channelz.
 func (t TLSInfo) GetSecurityValue() ChannelzSecurityValue {
 	v := &TLSChannelzSecurityValue{
 		StandardName: cipherSuiteLookup[t.State.CipherSuite],
 	}
 	// Currently there's no way to get LocalCertificate info from tls package.
 	if len(t.State.PeerCertificates) > 0 {
 		v.RemoteCertificate = t.State.PeerCertificates[0].Raw
 	}
 	return v
 }

 // tlsCreds is the credentials required for authenticating a connection using TLS.
 type tlsCreds struct {
 	// TLS configuration
 	config *tls.Config
 }

 func (c tlsCreds) Info() ProtocolInfo {
 	return ProtocolInfo{
 		SecurityProtocol: "tls",
 		SecurityVersion:  "1.2",
 		ServerName:       c.config.ServerName,
 	}
 }

 func (c *tlsCreds) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (_ net.Conn, _ AuthInfo, err error) {
 	// use local cfg to avoid clobbering ServerName if using multiple endpoints
 	cfg := cloneTLSConfig(c.config)
 	if cfg.ServerName == "" {
 		serverName, _, err := net.SplitHostPort(authority)
 		if err != nil {
 			// If the authority had no host port or if the authority cannot be parsed, use it as-is.
 			serverName = authority
 		}
 		cfg.ServerName = serverName
 	}
 	conn := tls.Client(rawConn, cfg)
 	errChannel := make(chan error, 1)
 	go func() {
 		errChannel <- conn.Handshake()
 	}()
 	select {
 	case err := <-errChannel:
 		if err != nil {
 			return nil, nil, err
 		}
 	case <-ctx.Done():
 		return nil, nil, ctx.Err()
 	}
 	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState()}, nil
 }

 func (c *tlsCreds) ServerHandshake(rawConn net.Conn) (net.Conn, AuthInfo, error) {
 	conn := tls.Server(rawConn, c.config)
 	if err := conn.Handshake(); err != nil {
 		return nil, nil, err
 	}
 	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState()}, nil
 }

 func (c *tlsCreds) Clone() TransportCredentials {
 	return NewTLS(c.config)
 }

 func (c *tlsCreds) OverrideServerName(serverNameOverride string) error {
 	c.config.ServerName = serverNameOverride
 	return nil
 }

 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)
 }

 // NewTLS uses c to construct a TransportCredentials based on TLS.
 func NewTLS(c *tls.Config) TransportCredentials {
 	tc := &tlsCreds{cloneTLSConfig(c)}
 	tc.config.NextProtos = appendH2ToNextProtos(tc.config.NextProtos)
 	return tc
 }

 // NewClientTLSFromCert constructs TLS credentials from the input certificate for client.
 // 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.
 func NewClientTLSFromCert(cp *x509.CertPool, serverNameOverride string) TransportCredentials {
 	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp})
 }

 // NewClientTLSFromFile constructs TLS credentials from the input certificate file for client.
 // 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.
 func NewClientTLSFromFile(certFile, serverNameOverride string) (TransportCredentials, error) {
 	b, err := ioutil.ReadFile(certFile)
 	if err != nil {
 		return nil, err
 	}
 	cp := x509.NewCertPool()
 	if !cp.AppendCertsFromPEM(b) {
 		return nil, fmt.Errorf("credentials: failed to append certificates")
 	}
 	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp}), nil
 }

 // NewServerTLSFromCert constructs TLS credentials from the input certificate for server.
 func NewServerTLSFromCert(cert *tls.Certificate) TransportCredentials {
 	return NewTLS(&tls.Config{Certificates: []tls.Certificate{*cert}})
 }

 // NewServerTLSFromFile constructs TLS credentials from the input certificate file and key
 // file for server.
 func NewServerTLSFromFile(certFile, keyFile string) (TransportCredentials, error) {
 	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
 	if err != nil {
 		return nil, err
 	}
 	return NewTLS(&tls.Config{Certificates: []tls.Certificate{cert}}), nil
 }

 // ChannelzSecurityInfo defines the interface that security protocols should implement
 // in order to provide security info to channelz.
 type ChannelzSecurityInfo interface {
 	GetSecurityValue() ChannelzSecurityValue
 }

 // ChannelzSecurityValue defines the interface that GetSecurityValue() return value
 // should satisfy. This interface should only be satisfied by *TLSChannelzSecurityValue
 // and *OtherChannelzSecurityValue.
 type ChannelzSecurityValue interface {
 	isChannelzSecurityValue()
 }

 // TLSChannelzSecurityValue defines the struct that TLS protocol should return
 // from GetSecurityValue(), containing security info like cipher and certificate used.
 type TLSChannelzSecurityValue struct {
 	ChannelzSecurityValue
 	StandardName      string
 	LocalCertificate  []byte
 	RemoteCertificate []byte
 }

 // OtherChannelzSecurityValue defines the struct that non-TLS protocol should return
 // from GetSecurityValue(), which contains protocol specific security info. Note
 // the Value field will be sent to users of channelz requesting channel info, and
 // thus sensitive info should better be avoided.
 type OtherChannelzSecurityValue struct {
 	ChannelzSecurityValue
 	Name  string
 	Value proto.Message
 }

 var cipherSuiteLookup = map[uint16]string{
 	tls.TLS_RSA_WITH_RC4_128_SHA:                "TLS_RSA_WITH_RC4_128_SHA",
 	tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA:           "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
 	tls.TLS_RSA_WITH_AES_128_CBC_SHA:            "TLS_RSA_WITH_AES_128_CBC_SHA",
 	tls.TLS_RSA_WITH_AES_256_CBC_SHA:            "TLS_RSA_WITH_AES_256_CBC_SHA",
 	tls.TLS_RSA_WITH_AES_128_GCM_SHA256:         "TLS_RSA_WITH_AES_128_GCM_SHA256",
 	tls.TLS_RSA_WITH_AES_256_GCM_SHA384:         "TLS_RSA_WITH_AES_256_GCM_SHA384",
 	tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA:        "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
 	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA:    "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
 	tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA:    "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
 	tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA:          "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
 	tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA:     "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
 	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA:      "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
 	tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA:      "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
 	tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256:   "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
 	tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
 	tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384:   "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
 	tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
 	tls.TLS_FALLBACK_SCSV:                       "TLS_FALLBACK_SCSV",
 	tls.TLS_RSA_WITH_AES_128_CBC_SHA256:         "TLS_RSA_WITH_AES_128_CBC_SHA256",
 	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
 	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256:   "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
 	tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305:    "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305",
 	tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305:  "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
 }

 // cloneTLSConfig returns a shallow clone of the exported
 // fields of cfg, ignoring the unexported sync.Once, which
 // contains a mutex and must not be copied.
 //
 // If cfg is nil, a new zero tls.Config is returned.
 //
 // TODO: inline this function if possible.
 func cloneTLSConfig(cfg *tls.Config) *tls.Config {
 	if cfg == nil {
 		return &tls.Config{}
 	}

 	return cfg.Clone()
 }

 // RequestInfo contains request data attached to the context passed to GetRequestMetadata calls.
 //
 // This API is experimental.
 type RequestInfo struct {
 	// The method passed to Invoke or NewStream for this RPC. (For proto methods, this has the format "/some.Service/Method")
 	Method string
 }

 // requestInfoKey is a struct to be used as the key when attaching a RequestInfo to a context object.
 type requestInfoKey struct{}

 // RequestInfoFromContext extracts the RequestInfo from the context if it exists.
 //
 // This API is experimental.
 func RequestInfoFromContext(ctx context.Context) (ri RequestInfo, ok bool) {
 	ri, ok = ctx.Value(requestInfoKey{}).(RequestInfo)
 	return
 }

 func init() {
 	ginternal.NewRequestInfoContext = func(ctx context.Context, ri RequestInfo) context.Context {
 		return context.WithValue(ctx, requestInfoKey{}, ri)
 	}
 }
	/*
	*
	* Copyright 2014 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 credentials implements various credentials supported by gRPC library,
	// which encapsulate all the state needed by a client to authenticate with a
	// server and make various assertions, e.g., about the client's identity, role,
	// or whether it is authorized to make a particular call.
	package credentials // import "google.golang.org/grpc/credentials"

	import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"errors"
	"fmt"
	"io/ioutil"
	"net"

	"github.com/golang/protobuf/proto"

	"google.golang.org/grpc/credentials/internal"
	ginternal "google.golang.org/grpc/internal"
	)

	// PerRPCCredentials defines the common interface for the credentials which need to
	// attach security information to every RPC (e.g., oauth2).
	type PerRPCCredentials interface {
	// GetRequestMetadata gets the current request metadata, refreshing
	// tokens if required. This should be called by the transport layer on
	// each request, and the data should be populated in headers or other
	// context. If a status code is returned, it will be used as the status
	// for the RPC. uri is the URI of the entry point for the request.
	// When supported by the underlying implementation, ctx can be used for
	// timeout and cancellation. Additionally, RequestInfo data will be
	// available via ctx to this call.
	// TODO(zhaoq): Define the set of the qualified keys instead of leaving
	// it as an arbitrary string.
	GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error)
	// RequireTransportSecurity indicates whether the credentials requires
	// transport security.
	RequireTransportSecurity() bool
	}

	// ProtocolInfo provides information regarding the gRPC wire protocol version,
	// security protocol, security protocol version in use, server name, etc.
	type ProtocolInfo struct {
	// ProtocolVersion is the gRPC wire protocol version.
	ProtocolVersion string
	// SecurityProtocol is the security protocol in use.
	SecurityProtocol string
	// SecurityVersion is the security protocol version.
	SecurityVersion string
	// ServerName is the user-configured server name.
	ServerName string
	}

	// AuthInfo defines the common interface for the auth information the users are interested in.
	type AuthInfo interface {
	AuthType() string
	}

	// ErrConnDispatched indicates that rawConn has been dispatched out of gRPC
	// and the caller should not close rawConn.
	var ErrConnDispatched = errors.New("credentials: rawConn is dispatched out of gRPC")

	// TransportCredentials defines the common interface for all the live gRPC wire
	// protocols and supported transport security protocols (e.g., TLS, SSL).
	type TransportCredentials interface {
	// ClientHandshake does the authentication handshake specified by the corresponding
	// authentication protocol on rawConn for clients. It returns the authenticated
	// connection and the corresponding auth information about the connection.
	// Implementations must use the provided context to implement timely cancellation.
	// gRPC will try to reconnect if the error returned is a temporary error
	// (io.EOF, context.DeadlineExceeded or err.Temporary() == true).
	// If the returned error is a wrapper error, implementations should make sure that
	// the error implements Temporary() to have the correct retry behaviors.
	//
	// If the returned net.Conn is closed, it MUST close the net.Conn provided.
	ClientHandshake(context.Context, string, net.Conn) (net.Conn, AuthInfo, error)
	// ServerHandshake does the authentication handshake for servers. It returns
	// the authenticated connection and the corresponding auth information about
	// the connection.
	//
	// If the returned net.Conn is closed, it MUST close the net.Conn provided.
	ServerHandshake(net.Conn) (net.Conn, AuthInfo, error)
	// Info provides the ProtocolInfo of this TransportCredentials.
	Info() ProtocolInfo
	// Clone makes a copy of this TransportCredentials.
	Clone() TransportCredentials
	// OverrideServerName overrides the server name used to verify the hostname on the returned certificates from the server.
	// gRPC internals also use it to override the virtual hosting name if it is set.
	// It must be called before dialing. Currently, this is only used by grpclb.
	OverrideServerName(string) error
	}

	// Bundle is a combination of TransportCredentials and PerRPCCredentials.
	//
	// It also contains a mode switching method, so it can be used as a combination
	// of different credential policies.
	//
	// Bundle cannot be used together with individual TransportCredentials.
	// PerRPCCredentials from Bundle will be appended to other PerRPCCredentials.
	//
	// This API is experimental.
	type Bundle interface {
	TransportCredentials() TransportCredentials
	PerRPCCredentials() PerRPCCredentials
	// NewWithMode should make a copy of Bundle, and switch mode. Modifying the
	// existing Bundle may cause races.
	//
	// NewWithMode returns nil if the requested mode is not supported.
	NewWithMode(mode string) (Bundle, error)
	}

	// TLSInfo contains the auth information for a TLS authenticated connection.
	// It implements the AuthInfo interface.
	type TLSInfo struct {
	State tls.ConnectionState
	}

	// AuthType returns the type of TLSInfo as a string.
	func (t TLSInfo) AuthType() string {
	return "tls"
	}

	// GetSecurityValue returns security info requested by channelz.
	func (t TLSInfo) GetSecurityValue() ChannelzSecurityValue {
	v := &TLSChannelzSecurityValue{
	StandardName: cipherSuiteLookup[t.State.CipherSuite],
	}
	// Currently there's no way to get LocalCertificate info from tls package.
	if len(t.State.PeerCertificates) > 0 {
	v.RemoteCertificate = t.State.PeerCertificates[0].Raw
	}
	return v
	}

	// tlsCreds is the credentials required for authenticating a connection using TLS.
	type tlsCreds struct {
	// TLS configuration
	config *tls.Config
	}

	func (c tlsCreds) Info() ProtocolInfo {
	return ProtocolInfo{
	SecurityProtocol: "tls",
	SecurityVersion: "1.2",
	ServerName: c.config.ServerName,
	}
	}

	func (c *tlsCreds) ClientHandshake(ctx context.Context, authority string, rawConn net.Conn) (_ net.Conn, _ AuthInfo, err error) {
	// use local cfg to avoid clobbering ServerName if using multiple endpoints
	cfg := cloneTLSConfig(c.config)
	if cfg.ServerName == "" {
	serverName, _, err := net.SplitHostPort(authority)
	if err != nil {
	// If the authority had no host port or if the authority cannot be parsed, use it as-is.
	serverName = authority
	}
	cfg.ServerName = serverName
	}
	conn := tls.Client(rawConn, cfg)
	errChannel := make(chan error, 1)
	go func() {
	errChannel <- conn.Handshake()
	}()
	select {
	case err := <-errChannel:
	if err != nil {
	return nil, nil, err
	}
	case <-ctx.Done():
	return nil, nil, ctx.Err()
	}
	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState()}, nil
	}

	func (c *tlsCreds) ServerHandshake(rawConn net.Conn) (net.Conn, AuthInfo, error) {
	conn := tls.Server(rawConn, c.config)
	if err := conn.Handshake(); err != nil {
	return nil, nil, err
	}
	return internal.WrapSyscallConn(rawConn, conn), TLSInfo{conn.ConnectionState()}, nil
	}

	func (c *tlsCreds) Clone() TransportCredentials {
	return NewTLS(c.config)
	}

	func (c *tlsCreds) OverrideServerName(serverNameOverride string) error {
	c.config.ServerName = serverNameOverride
	return nil
	}

	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)
	}

	// NewTLS uses c to construct a TransportCredentials based on TLS.
	func NewTLS(c *tls.Config) TransportCredentials {
	tc := &tlsCreds{cloneTLSConfig(c)}
	tc.config.NextProtos = appendH2ToNextProtos(tc.config.NextProtos)
	return tc
	}

	// NewClientTLSFromCert constructs TLS credentials from the input certificate for client.
	// 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.
	func NewClientTLSFromCert(cp *x509.CertPool, serverNameOverride string) TransportCredentials {
	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp})
	}

	// NewClientTLSFromFile constructs TLS credentials from the input certificate file for client.
	// 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.
	func NewClientTLSFromFile(certFile, serverNameOverride string) (TransportCredentials, error) {
	b, err := ioutil.ReadFile(certFile)
	if err != nil {
	return nil, err
	}
	cp := x509.NewCertPool()
	if !cp.AppendCertsFromPEM(b) {
	return nil, fmt.Errorf("credentials: failed to append certificates")
	}
	return NewTLS(&tls.Config{ServerName: serverNameOverride, RootCAs: cp}), nil
	}

	// NewServerTLSFromCert constructs TLS credentials from the input certificate for server.
	func NewServerTLSFromCert(cert *tls.Certificate) TransportCredentials {
	return NewTLS(&tls.Config{Certificates: []tls.Certificate{*cert}})
	}

	// NewServerTLSFromFile constructs TLS credentials from the input certificate file and key
	// file for server.
	func NewServerTLSFromFile(certFile, keyFile string) (TransportCredentials, error) {
	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
	if err != nil {
	return nil, err
	}
	return NewTLS(&tls.Config{Certificates: []tls.Certificate{cert}}), nil
	}

	// ChannelzSecurityInfo defines the interface that security protocols should implement
	// in order to provide security info to channelz.
	type ChannelzSecurityInfo interface {
	GetSecurityValue() ChannelzSecurityValue
	}

	// ChannelzSecurityValue defines the interface that GetSecurityValue() return value
	// should satisfy. This interface should only be satisfied by *TLSChannelzSecurityValue
	// and *OtherChannelzSecurityValue.
	type ChannelzSecurityValue interface {
	isChannelzSecurityValue()
	}

	// TLSChannelzSecurityValue defines the struct that TLS protocol should return
	// from GetSecurityValue(), containing security info like cipher and certificate used.
	type TLSChannelzSecurityValue struct {
	ChannelzSecurityValue
	StandardName string
	LocalCertificate []byte
	RemoteCertificate []byte
	}

	// OtherChannelzSecurityValue defines the struct that non-TLS protocol should return
	// from GetSecurityValue(), which contains protocol specific security info. Note
	// the Value field will be sent to users of channelz requesting channel info, and
	// thus sensitive info should better be avoided.
	type OtherChannelzSecurityValue struct {
	ChannelzSecurityValue
	Name string
	Value proto.Message
	}

	var cipherSuiteLookup = map[uint16]string{
	tls.TLS_RSA_WITH_RC4_128_SHA: "TLS_RSA_WITH_RC4_128_SHA",
	tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA: "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
	tls.TLS_RSA_WITH_AES_128_CBC_SHA: "TLS_RSA_WITH_AES_128_CBC_SHA",
	tls.TLS_RSA_WITH_AES_256_CBC_SHA: "TLS_RSA_WITH_AES_256_CBC_SHA",
	tls.TLS_RSA_WITH_AES_128_GCM_SHA256: "TLS_RSA_WITH_AES_128_GCM_SHA256",
	tls.TLS_RSA_WITH_AES_256_GCM_SHA384: "TLS_RSA_WITH_AES_256_GCM_SHA384",
	tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA: "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
	tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA: "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
	tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA: "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
	tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA: "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA: "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
	tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA: "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
	tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256: "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
	tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
	tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384: "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
	tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384: "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
	tls.TLS_FALLBACK_SCSV: "TLS_FALLBACK_SCSV",
	tls.TLS_RSA_WITH_AES_128_CBC_SHA256: "TLS_RSA_WITH_AES_128_CBC_SHA256",
	tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256: "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
	tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256: "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
	tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305: "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305",
	tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305: "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305",
	}

	// cloneTLSConfig returns a shallow clone of the exported
	// fields of cfg, ignoring the unexported sync.Once, which
	// contains a mutex and must not be copied.
	//
	// If cfg is nil, a new zero tls.Config is returned.
	//
	// TODO: inline this function if possible.
	func cloneTLSConfig(cfg tls.Config) tls.Config {
	if cfg == nil {
	return &tls.Config{}
	}

	return cfg.Clone()
	}

	// RequestInfo contains request data attached to the context passed to GetRequestMetadata calls.
	//
	// This API is experimental.
	type RequestInfo struct {
	// The method passed to Invoke or NewStream for this RPC. (For proto methods, this has the format "/some.Service/Method")
	Method string
	}

	// requestInfoKey is a struct to be used as the key when attaching a RequestInfo to a context object.
	type requestInfoKey struct{}

	// RequestInfoFromContext extracts the RequestInfo from the context if it exists.
	//
	// This API is experimental.
	func RequestInfoFromContext(ctx context.Context) (ri RequestInfo, ok bool) {
	ri, ok = ctx.Value(requestInfoKey{}).(RequestInfo)
	return
	}

	func init() {
	ginternal.NewRequestInfoContext = func(ctx context.Context, ri RequestInfo) context.Context {
	return context.WithValue(ctx, requestInfoKey{}, ri)
	}
	}