auth, etcdserver: introduce revision of authStore for avoiding TOCTOU problem

This commit introduces revision of authStore. The revision number
represents a version of authStore that is incremented by updating auth
related information.

The revision is required for avoiding TOCTOU problems. Currently there
are two types of the TOCTOU problems in v3 auth.

The first one is in ordinal linearizable requests with a sequence like
below ():
1. Request from client CA is processed in follower FA. FA looks up the
   username (let it U) for the request from a token of the request. At
   this time, the request is authorized correctly.
2. Another request from client CB is processed in follower FB. CB
   is for changing U's password.
3. FB forwards the request from CB to the leader before FA. Now U's
   password is updated and the request from CA should be rejected.
4. However, the request from CA is processed by the leader because
   authentication is already done in FA.

For avoiding the above sequence, this commit lets
etcdserverpb.RequestHeader have a member revision. The member is
initialized during authentication by followers and checked in a
leader. If the revision in RequestHeader is lower than the leader's
authStore revision, it means a sequence like above happened. In such a
case, the state machine returns auth.ErrAuthRevisionObsolete. The
error code lets nodes retry their requests.

The second one, a case of serializable range and txn, is more
subtle. Because these requests are processed in follower directly. The
TOCTOU problem can be caused by a sequence like below:
1. Serializable request from client CA is processed in follower FA. At
   first, FA looks up the username (let it U) and its permission
   before actual access to KV.
2. Another request from client CB is processed in follower FB and
   forwarded to the leader. The cluster including FA now commits a log
   entry of the request from CB. Assume the request changed the
   permission or password of U.
3. Now the serializable request from CA is accessing to KV. Even if
   the access is allowed at the point of 1, now it can be invalid
   because of the change introduced in 2.

For avoiding the above sequence, this commit lets the functions of
serializable requests (EtcdServer.Range() and EtcdServer.Txn())
compare the revision in the request header with the latest revision of
authStore after the actual access. If the saved revision is lower than
the latest one, it means the permission can be changed. Although it
would introduce false positives (e.g. changing other user's password),
it prevents the TOCTOU problem. This idea is an implementation of
Anthony's comment:
https://github.com/coreos/etcd/pull/5739#issuecomment-228128254

auth/simple_token.go

@@ -20,6 +20,7 @@ package auth
 import (
 	"crypto/rand"
 	"math/big"
+	"strings"
 )
 
 const (
@@ -53,3 +54,14 @@ func (as *authStore) assignSimpleTokenToUser(username, token string) {
 	as.simpleTokens[token] = username
 	as.simpleTokensMu.Unlock()
 }
+
+func (as *authStore) invalidateUser(username string) {
+	as.simpleTokensMu.Lock()
+	defer as.simpleTokensMu.Unlock()
+
+	for token, name := range as.simpleTokens {
+		if strings.Compare(name, username) == 0 {
+			delete(as.simpleTokens, token)
+		}
+	}
+}

auth/store.go

@@ -16,6 +16,7 @@ package auth
 
 import (
 	"bytes"
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"sort"
@@ -35,6 +36,8 @@ var (
 	authEnabled   = []byte{1}
 	authDisabled  = []byte{0}
 
+	revisionKey = []byte("authRevision")
+
 	authBucketName      = []byte("auth")
 	authUsersBucketName = []byte("authUsers")
 	authRolesBucketName = []byte("authRoles")
@@ -52,6 +55,7 @@ var (
 	ErrRoleNotGranted       = errors.New("auth: role is not granted to the user")
 	ErrPermissionNotGranted = errors.New("auth: permission is not granted to the role")
 	ErrAuthNotEnabled       = errors.New("auth: authentication is not enabled")
+	ErrAuthOldRevision      = errors.New("auth: revision in header is old")
 
 	// BcryptCost is the algorithm cost / strength for hashing auth passwords
 	BcryptCost = bcrypt.DefaultCost
@@ -60,8 +64,15 @@ var (
 const (
 	rootUser = "root"
 	rootRole = "root"
+
+	revBytesLen = 8
 )
 
+type AuthInfo struct {
+	Username string
+	Revision uint64
+}
+
 type AuthStore interface {
 	// AuthEnable turns on the authentication feature
 	AuthEnable() error
@@ -114,23 +125,27 @@ type AuthStore interface {
 	// RoleList gets a list of all roles
 	RoleList(r *pb.AuthRoleListRequest) (*pb.AuthRoleListResponse, error)
 
-	// UsernameFromToken gets a username from the given Token
-	UsernameFromToken(token string) (string, bool)
+	// AuthInfoFromToken gets a username from the given Token and current revision number
+	// (The revision number is used for preventing the TOCTOU problem)
+	AuthInfoFromToken(token string) (*AuthInfo, bool)
 
 	// IsPutPermitted checks put permission of the user
-	IsPutPermitted(username string, key []byte) bool
+	IsPutPermitted(authInfo *AuthInfo, key []byte) error
 
 	// IsRangePermitted checks range permission of the user
-	IsRangePermitted(username string, key, rangeEnd []byte) bool
+	IsRangePermitted(authInfo *AuthInfo, key, rangeEnd []byte) error
 
 	// IsDeleteRangePermitted checks delete-range permission of the user
-	IsDeleteRangePermitted(username string, key, rangeEnd []byte) bool
+	IsDeleteRangePermitted(authInfo *AuthInfo, key, rangeEnd []byte) error
 
 	// IsAdminPermitted checks admin permission of the user
-	IsAdminPermitted(username string) bool
+	IsAdminPermitted(authInfo *AuthInfo) error
 
 	// GenSimpleToken produces a simple random string
 	GenSimpleToken() (string, error)
+
+	// Revision gets current revision of authStore
+	Revision() uint64
 }
 
 type authStore struct {
@@ -142,6 +157,8 @@ type authStore struct {
 
 	simpleTokensMu sync.RWMutex
 	simpleTokens   map[string]string // token -> username
+
+	revision uint64
 }
 
 func (as *authStore) AuthEnable() error {
@@ -170,6 +187,8 @@ func (as *authStore) AuthEnable() error {
 
 	as.rangePermCache = make(map[string]*unifiedRangePermissions)
 
+	as.revision = getRevision(tx)
+
 	plog.Noticef("Authentication enabled")
 
 	return nil
@@ -180,6 +199,7 @@ func (as *authStore) AuthDisable() {
 	tx := b.BatchTx()
 	tx.Lock()
 	tx.UnsafePut(authBucketName, enableFlagKey, authDisabled)
+	as.commitRevision(tx)
 	tx.Unlock()
 	b.ForceCommit()
 
@@ -235,6 +255,9 @@ func (as *authStore) Recover(be backend.Backend) {
 			enabled = true
 		}
 	}
+
+	as.revision = getRevision(tx)
+
 	tx.Unlock()
 
 	as.enabledMu.Lock()
@@ -265,6 +288,8 @@ func (as *authStore) UserAdd(r *pb.AuthUserAddRequest) (*pb.AuthUserAddResponse,
 
 	putUser(tx, newUser)
 
+	as.commitRevision(tx)
+
 	plog.Noticef("added a new user: %s", r.Name)
 
 	return &pb.AuthUserAddResponse{}, nil
@@ -282,6 +307,11 @@ func (as *authStore) UserDelete(r *pb.AuthUserDeleteRequest) (*pb.AuthUserDelete
 
 	delUser(tx, r.Name)
 
+	as.commitRevision(tx)
+
+	as.invalidateCachedPerm(r.Name)
+	as.invalidateUser(r.Name)
+
 	plog.Noticef("deleted a user: %s", r.Name)
 
 	return &pb.AuthUserDeleteResponse{}, nil
@@ -313,6 +343,11 @@ func (as *authStore) UserChangePassword(r *pb.AuthUserChangePasswordRequest) (*p
 
 	putUser(tx, updatedUser)
 
+	as.commitRevision(tx)
+
+	as.invalidateCachedPerm(r.Name)
+	as.invalidateUser(r.Name)
+
 	plog.Noticef("changed a password of a user: %s", r.Name)
 
 	return &pb.AuthUserChangePasswordResponse{}, nil
@@ -348,6 +383,8 @@ func (as *authStore) UserGrantRole(r *pb.AuthUserGrantRoleRequest) (*pb.AuthUser
 
 	as.invalidateCachedPerm(r.User)
 
+	as.commitRevision(tx)
+
 	plog.Noticef("granted role %s to user %s", r.Role, r.User)
 	return &pb.AuthUserGrantRoleResponse{}, nil
 }
@@ -416,6 +453,8 @@ func (as *authStore) UserRevokeRole(r *pb.AuthUserRevokeRoleRequest) (*pb.AuthUs
 
 	as.invalidateCachedPerm(r.Name)
 
+	as.commitRevision(tx)
+
 	plog.Noticef("revoked role %s from user %s", r.Role, r.Name)
 	return &pb.AuthUserRevokeRoleResponse{}, nil
 }
@@ -485,6 +524,8 @@ func (as *authStore) RoleRevokePermission(r *pb.AuthRoleRevokePermissionRequest)
 	// It should be optimized.
 	as.clearCachedPerm()
 
+	as.commitRevision(tx)
+
 	plog.Noticef("revoked key %s from role %s", r.Key, r.Role)
 	return &pb.AuthRoleRevokePermissionResponse{}, nil
 }
@@ -513,6 +554,8 @@ func (as *authStore) RoleDelete(r *pb.AuthRoleDeleteRequest) (*pb.AuthRoleDelete
 
 	delRole(tx, r.Role)
 
+	as.commitRevision(tx)
+
 	plog.Noticef("deleted role %s", r.Role)
 	return &pb.AuthRoleDeleteResponse{}, nil
 }
@@ -533,16 +576,18 @@ func (as *authStore) RoleAdd(r *pb.AuthRoleAddRequest) (*pb.AuthRoleAddResponse,
 
 	putRole(tx, newRole)
 
+	as.commitRevision(tx)
+
 	plog.Noticef("Role %s is created", r.Name)
 
 	return &pb.AuthRoleAddResponse{}, nil
 }
 
-func (as *authStore) UsernameFromToken(token string) (string, bool) {
+func (as *authStore) AuthInfoFromToken(token string) (*AuthInfo, bool) {
 	as.simpleTokensMu.RLock()
 	defer as.simpleTokensMu.RUnlock()
 	t, ok := as.simpleTokens[token]
-	return t, ok
+	return &AuthInfo{Username: t, Revision: as.revision}, ok
 }
 
 type permSlice []*authpb.Permission
@@ -594,15 +639,21 @@ func (as *authStore) RoleGrantPermission(r *pb.AuthRoleGrantPermissionRequest) (
 	// It should be optimized.
 	as.clearCachedPerm()
 
+	as.commitRevision(tx)
+
 	plog.Noticef("role %s's permission of key %s is updated as %s", r.Name, r.Perm.Key, authpb.Permission_Type_name[int32(r.Perm.PermType)])
 
 	return &pb.AuthRoleGrantPermissionResponse{}, nil
 }
 
-func (as *authStore) isOpPermitted(userName string, key, rangeEnd []byte, permTyp authpb.Permission_Type) bool {
+func (as *authStore) isOpPermitted(userName string, revision uint64, key, rangeEnd []byte, permTyp authpb.Permission_Type) error {
 	// TODO(mitake): this function would be costly so we need a caching mechanism
 	if !as.isAuthEnabled() {
-		return true
+		return nil
+	}
+
+	if revision < as.revision {
+		return ErrAuthOldRevision
 	}
 
 	tx := as.be.BatchTx()
@@ -612,43 +663,47 @@ func (as *authStore) isOpPermitted(userName string, key, rangeEnd []byte, permTy
 	user := getUser(tx, userName)
 	if user == nil {
 		plog.Errorf("invalid user name %s for permission checking", userName)
-		return false
+		return ErrPermissionDenied
 	}
 
 	if as.isRangeOpPermitted(tx, userName, key, rangeEnd, permTyp) {
-		return true
+		return nil
 	}
 
-	return false
+	return ErrPermissionDenied
 }
 
-func (as *authStore) IsPutPermitted(username string, key []byte) bool {
-	return as.isOpPermitted(username, key, nil, authpb.WRITE)
+func (as *authStore) IsPutPermitted(authInfo *AuthInfo, key []byte) error {
+	return as.isOpPermitted(authInfo.Username, authInfo.Revision, key, nil, authpb.WRITE)
 }
 
-func (as *authStore) IsRangePermitted(username string, key, rangeEnd []byte) bool {
-	return as.isOpPermitted(username, key, rangeEnd, authpb.READ)
+func (as *authStore) IsRangePermitted(authInfo *AuthInfo, key, rangeEnd []byte) error {
+	return as.isOpPermitted(authInfo.Username, authInfo.Revision, key, rangeEnd, authpb.READ)
 }
 
-func (as *authStore) IsDeleteRangePermitted(username string, key, rangeEnd []byte) bool {
-	return as.isOpPermitted(username, key, rangeEnd, authpb.WRITE)
+func (as *authStore) IsDeleteRangePermitted(authInfo *AuthInfo, key, rangeEnd []byte) error {
+	return as.isOpPermitted(authInfo.Username, authInfo.Revision, key, rangeEnd, authpb.WRITE)
 }
 
-func (as *authStore) IsAdminPermitted(username string) bool {
+func (as *authStore) IsAdminPermitted(authInfo *AuthInfo) error {
 	if !as.isAuthEnabled() {
-		return true
+		return nil
 	}
 
 	tx := as.be.BatchTx()
 	tx.Lock()
 	defer tx.Unlock()
 
-	u := getUser(tx, username)
+	u := getUser(tx, authInfo.Username)
 	if u == nil {
-		return false
+		return ErrUserNotFound
+	}
+
+	if !hasRootRole(u) {
+		return ErrPermissionDenied
 	}
 
-	return hasRootRole(u)
+	return nil
 }
 
 func getUser(tx backend.BatchTx, username string) *authpb.User {
@@ -760,13 +815,18 @@ func NewAuthStore(be backend.Backend) *authStore {
 	tx.UnsafeCreateBucket(authUsersBucketName)
 	tx.UnsafeCreateBucket(authRolesBucketName)
 
-	tx.Unlock()
-	be.ForceCommit()
-
-	return &authStore{
+	as := &authStore{
 		be:           be,
 		simpleTokens: make(map[string]string),
+		revision:     0,
 	}
+
+	as.commitRevision(tx)
+
+	tx.Unlock()
+	be.ForceCommit()
+
+	return as
 }
 
 func hasRootRole(u *authpb.User) bool {
@@ -777,3 +837,23 @@ func hasRootRole(u *authpb.User) bool {
 	}
 	return false
 }
+
+func (as *authStore) commitRevision(tx backend.BatchTx) {
+	as.revision++
+	revBytes := make([]byte, revBytesLen)
+	binary.BigEndian.PutUint64(revBytes, as.revision)
+	tx.UnsafePut(authBucketName, revisionKey, revBytes)
+}
+
+func getRevision(tx backend.BatchTx) uint64 {
+	_, vs := tx.UnsafeRange(authBucketName, []byte(revisionKey), nil, 0)
+	if len(vs) != 1 {
+		plog.Panicf("failed to get the key of auth store revision")
+	}
+
+	return binary.BigEndian.Uint64(vs[0])
+}
+
+func (as *authStore) Revision() uint64 {
+	return as.revision
+}

etcdserver/apply_auth.go

@@ -27,8 +27,9 @@ type authApplierV3 struct {
 
 	// mu serializes Apply so that user isn't corrupted and so that
 	// serialized requests don't leak data from TOCTOU errors
-	mu   sync.Mutex
-	user string
+	mu sync.Mutex
+
+	authInfo auth.AuthInfo
 }
 
 func newAuthApplierV3(as auth.AuthStore, base applierV3) *authApplierV3 {
@@ -41,46 +42,57 @@ func (aa *authApplierV3) Apply(r *pb.InternalRaftRequest) *applyResult {
 	if r.Header != nil {
 		// backward-compatible with pre-3.0 releases when internalRaftRequest
 		// does not have header field
-		aa.user = r.Header.Username
+		aa.authInfo.Username = r.Header.Username
+		aa.authInfo.Revision = r.Header.AuthRevision
 	}
-	if needAdminPermission(r) && !aa.as.IsAdminPermitted(aa.user) {
-		aa.user = ""
-		return &applyResult{err: auth.ErrPermissionDenied}
+	if needAdminPermission(r) {
+		if err := aa.as.IsAdminPermitted(&aa.authInfo); err != nil {
+			aa.authInfo.Username = ""
+			aa.authInfo.Revision = 0
+			return &applyResult{err: err}
+		}
 	}
 	ret := aa.applierV3.Apply(r)
-	aa.user = ""
+	aa.authInfo.Username = ""
+	aa.authInfo.Revision = 0
 	return ret
 }
 
 func (aa *authApplierV3) Put(txnID int64, r *pb.PutRequest) (*pb.PutResponse, error) {
-	if !aa.as.IsPutPermitted(aa.user, r.Key) {
-		return nil, auth.ErrPermissionDenied
+	if err := aa.as.IsPutPermitted(&aa.authInfo, r.Key); err != nil {
+		return nil, err
 	}
-	if r.PrevKv && !aa.as.IsRangePermitted(aa.user, r.Key, nil) {
-		return nil, auth.ErrPermissionDenied
+	if r.PrevKv {
+		err := aa.as.IsRangePermitted(&aa.authInfo, r.Key, nil)
+		if err != nil {
+			return nil, err
+		}
 	}
 	return aa.applierV3.Put(txnID, r)
 }
 
 func (aa *authApplierV3) Range(txnID int64, r *pb.RangeRequest) (*pb.RangeResponse, error) {
-	if !aa.as.IsRangePermitted(aa.user, r.Key, r.RangeEnd) {
-		return nil, auth.ErrPermissionDenied
+	if err := aa.as.IsRangePermitted(&aa.authInfo, r.Key, r.RangeEnd); err != nil {
+		return nil, err
 	}
 	return aa.applierV3.Range(txnID, r)
 }
 
 func (aa *authApplierV3) DeleteRange(txnID int64, r *pb.DeleteRangeRequest) (*pb.DeleteRangeResponse, error) {
-	if !aa.as.IsDeleteRangePermitted(aa.user, r.Key, r.RangeEnd) {
-		return nil, auth.ErrPermissionDenied
+	if err := aa.as.IsDeleteRangePermitted(&aa.authInfo, r.Key, r.RangeEnd); err != nil {
+		return nil, err
 	}
-	if r.PrevKv && !aa.as.IsRangePermitted(aa.user, r.Key, r.RangeEnd) {
-		return nil, auth.ErrPermissionDenied
+	if r.PrevKv {
+		err := aa.as.IsRangePermitted(&aa.authInfo, r.Key, r.RangeEnd)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	return aa.applierV3.DeleteRange(txnID, r)
 }
 
-func (aa *authApplierV3) checkTxnReqsPermission(reqs []*pb.RequestOp) bool {
+func (aa *authApplierV3) checkTxnReqsPermission(reqs []*pb.RequestOp) error {
 	for _, requ := range reqs {
 		switch tv := requ.Request.(type) {
 		case *pb.RequestOp_RequestRange:
@@ -88,8 +100,8 @@ func (aa *authApplierV3) checkTxnReqsPermission(reqs []*pb.RequestOp) bool {
 				continue
 			}
 
-			if !aa.as.IsRangePermitted(aa.user, tv.RequestRange.Key, tv.RequestRange.RangeEnd) {
-				return false
+			if err := aa.as.IsRangePermitted(&aa.authInfo, tv.RequestRange.Key, tv.RequestRange.RangeEnd); err != nil {
+				return err
 			}
 
 		case *pb.RequestOp_RequestPut:
@@ -97,8 +109,8 @@ func (aa *authApplierV3) checkTxnReqsPermission(reqs []*pb.RequestOp) bool {
 				continue
 			}
 
-			if !aa.as.IsPutPermitted(aa.user, tv.RequestPut.Key) {
-				return false
+			if err := aa.as.IsPutPermitted(&aa.authInfo, tv.RequestPut.Key); err != nil {
+				return err
 			}
 
 		case *pb.RequestOp_RequestDeleteRange:
@@ -106,31 +118,35 @@ func (aa *authApplierV3) checkTxnReqsPermission(reqs []*pb.RequestOp) bool {
 				continue
 			}
 
-			if tv.RequestDeleteRange.PrevKv && !aa.as.IsRangePermitted(aa.user, tv.RequestDeleteRange.Key, tv.RequestDeleteRange.RangeEnd) {
-				return false
+			if tv.RequestDeleteRange.PrevKv {
+				err := aa.as.IsRangePermitted(&aa.authInfo, tv.RequestDeleteRange.Key, tv.RequestDeleteRange.RangeEnd)
+				if err != nil {
+					return err
+				}
 			}
 
-			if !aa.as.IsDeleteRangePermitted(aa.user, tv.RequestDeleteRange.Key, tv.RequestDeleteRange.RangeEnd) {
-				return false
+			err := aa.as.IsDeleteRangePermitted(&aa.authInfo, tv.RequestDeleteRange.Key, tv.RequestDeleteRange.RangeEnd)
+			if err != nil {
+				return err
 			}
 		}
 	}
 
-	return true
+	return nil
 }
 
 func (aa *authApplierV3) Txn(rt *pb.TxnRequest) (*pb.TxnResponse, error) {
 	for _, c := range rt.Compare {
-		if !aa.as.IsRangePermitted(aa.user, c.Key, nil) {
-			return nil, auth.ErrPermissionDenied
+		if err := aa.as.IsRangePermitted(&aa.authInfo, c.Key, nil); err != nil {
+			return nil, err
 		}
 	}
 
-	if !aa.checkTxnReqsPermission(rt.Success) {
-		return nil, auth.ErrPermissionDenied
+	if err := aa.checkTxnReqsPermission(rt.Success); err != nil {
+		return nil, err
 	}
-	if !aa.checkTxnReqsPermission(rt.Failure) {
-		return nil, auth.ErrPermissionDenied
+	if err := aa.checkTxnReqsPermission(rt.Failure); err != nil {
+		return nil, err
 	}
 
 	return aa.applierV3.Txn(rt)

etcdserver/etcdserverpb/raft_internal.pb.go

@@ -23,6 +23,8 @@ type RequestHeader struct {
 	ID uint64 `protobuf:"varint,1,opt,name=ID,json=iD,proto3" json:"ID,omitempty"`
 	// username is a username that is associated with an auth token of gRPC connection
 	Username string `protobuf:"bytes,2,opt,name=username,proto3" json:"username,omitempty"`
+	// auth_revision is a revision number of auth.authStore. It is not related to mvcc
+	AuthRevision uint64 `protobuf:"varint,3,opt,name=auth_revision,json=authRevision,proto3" json:"auth_revision,omitempty"`
 }
 
 func (m *RequestHeader) Reset()                    { *m = RequestHeader{} }
@@ -124,6 +126,11 @@ func (m *RequestHeader) MarshalTo(data []byte) (int, error) {
 		i = encodeVarintRaftInternal(data, i, uint64(len(m.Username)))
 		i += copy(data[i:], m.Username)
 	}
+	if m.AuthRevision != 0 {
+		data[i] = 0x18
+		i++
+		i = encodeVarintRaftInternal(data, i, uint64(m.AuthRevision))
+	}
 	return i, nil
 }
 
@@ -535,6 +542,9 @@ func (m *RequestHeader) Size() (n int) {
 	if l > 0 {
 		n += 1 + l + sovRaftInternal(uint64(l))
 	}
+	if m.AuthRevision != 0 {
+		n += 1 + sovRaftInternal(uint64(m.AuthRevision))
+	}
 	return n
 }
 
@@ -765,6 +775,25 @@ func (m *RequestHeader) Unmarshal(data []byte) error {
 			}
 			m.Username = string(data[iNdEx:postIndex])
 			iNdEx = postIndex
+		case 3:
+			if wireType != 0 {
+				return fmt.Errorf("proto: wrong wireType = %d for field AuthRevision", wireType)
+			}
+			m.AuthRevision = 0
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowRaftInternal
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := data[iNdEx]
+				iNdEx++
+				m.AuthRevision |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
 		default:
 			iNdEx = preIndex
 			skippy, err := skipRaftInternal(data[iNdEx:])
@@ -2006,57 +2035,57 @@ var (
 )
 
 var fileDescriptorRaftInternal = []byte{
-	// 824 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x7c, 0x96, 0xdd, 0x4e, 0xdb, 0x48,
-	0x14, 0xc7, 0x49, 0xf8, 0xcc, 0x24, 0x64, 0xd9, 0x01, 0x76, 0x67, 0x83, 0x94, 0x85, 0xac, 0x76,
-	0x97, 0x7e, 0xd1, 0x0a, 0x2e, 0x7b, 0xd1, 0xa6, 0x04, 0x01, 0x12, 0x42, 0xc8, 0xa2, 0x52, 0xa5,
-	0x5e, 0x58, 0x43, 0x7c, 0x48, 0x5c, 0x1c, 0xdb, 0xb5, 0x27, 0x29, 0x7d, 0x93, 0x3e, 0x46, 0xbf,
-	0x1e, 0x82, 0x8b, 0x7e, 0xd0, 0xf6, 0x05, 0x5a, 0x7a, 0xd3, 0xab, 0xde, 0xb4, 0x0f, 0x50, 0xcd,
-	0x87, 0xc7, 0x71, 0x32, 0xe1, 0xce, 0x3e, 0xe7, 0x7f, 0x7e, 0xe7, 0x4c, 0xe6, 0x3f, 0x9e, 0xa0,
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-	0x54, 0x8c, 0x4a, 0x7f, 0xa5, 0x08, 0x00, 0x00,
+	// 831 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x7c, 0x56, 0xdb, 0x4e, 0xdb, 0x4a,
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 }

etcdserver/etcdserverpb/raft_internal.proto

@@ -14,6 +14,8 @@ message RequestHeader {
   uint64 ID = 1;
   // username is a username that is associated with an auth token of gRPC connection
   string username = 2;
+  // auth_revision is a revision number of auth.authStore. It is not related to mvcc
+  uint64 auth_revision = 3;
 }
 
 // An InternalRaftRequest is the union of all requests which can be

etcdserver/v3_server.go

@@ -19,6 +19,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/coreos/etcd/auth"
 	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/lease"
 	"github.com/coreos/etcd/lease/leasehttp"
@@ -87,15 +88,34 @@ func (s *EtcdServer) Range(ctx context.Context, r *pb.RangeRequest) (*pb.RangeRe
 	var err error
 
 	if r.Serializable {
-		var user string
-		user, err = s.usernameFromCtx(ctx)
-		if err != nil {
-			return nil, err
+		for {
+			authInfo, err := s.authInfoFromCtx(ctx)
+			if err != nil {
+				return nil, err
+			}
+
+			hdr := &pb.RequestHeader{}
+			if authInfo != nil {
+				hdr.Username = authInfo.Username
+				hdr.AuthRevision = authInfo.Revision
+			}
+
+			result = s.applyV3.Apply(&pb.InternalRaftRequest{Header: hdr, Range: r})
+
+			if result.err != nil {
+				if result.err == auth.ErrAuthOldRevision {
+					continue
+				}
+				break
+			}
+
+			if authInfo == nil || authInfo.Revision == s.authStore.Revision() {
+				break
+			}
+
+			// The revision that authorized this request is obsolete.
+			// For avoiding TOCTOU problem, retry of the request is required.
 		}
-		result = s.applyV3.Apply(
-			&pb.InternalRaftRequest{
-				Header: &pb.RequestHeader{Username: user},
-				Range:  r})
 	} else {
 		result, err = s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Range: r})
 	}
@@ -135,14 +155,34 @@ func (s *EtcdServer) Txn(ctx context.Context, r *pb.TxnRequest) (*pb.TxnResponse
 	var err error
 
 	if isTxnSerializable(r) {
-		user, err := s.usernameFromCtx(ctx)
-		if err != nil {
-			return nil, err
+		for {
+			authInfo, err := s.authInfoFromCtx(ctx)
+			if err != nil {
+				return nil, err
+			}
+
+			hdr := &pb.RequestHeader{}
+			if authInfo != nil {
+				hdr.Username = authInfo.Username
+				hdr.AuthRevision = authInfo.Revision
+			}
+
+			result = s.applyV3.Apply(&pb.InternalRaftRequest{Header: hdr, Txn: r})
+
+			if result.err != nil {
+				if result.err == auth.ErrAuthOldRevision {
+					continue
+				}
+				break
+			}
+
+			if authInfo == nil || authInfo.Revision == s.authStore.Revision() {
+				break
+			}
+
+			// The revision that authorized this request is obsolete.
+			// For avoiding TOCTOU problem, retry of this request is required.
 		}
-		result = s.applyV3.Apply(
-			&pb.InternalRaftRequest{
-				Header: &pb.RequestHeader{Username: user},
-				Txn:    r})
 	} else {
 		result, err = s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Txn: r})
 	}
@@ -170,7 +210,7 @@ func isTxnSerializable(r *pb.TxnRequest) bool {
 }
 
 func (s *EtcdServer) Compact(ctx context.Context, r *pb.CompactionRequest) (*pb.CompactionResponse, error) {
-	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Compaction: r})
+	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{Compaction: r})
 	if r.Physical && result != nil && result.physc != nil {
 		<-result.physc
 		// The compaction is done deleting keys; the hash is now settled
@@ -203,7 +243,7 @@ func (s *EtcdServer) LeaseGrant(ctx context.Context, r *pb.LeaseGrantRequest) (*
 		// only use positive int64 id's
 		r.ID = int64(s.reqIDGen.Next() & ((1 << 63) - 1))
 	}
-	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{LeaseGrant: r})
+	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{LeaseGrant: r})
 	if err != nil {
 		return nil, err
 	}
@@ -214,7 +254,7 @@ func (s *EtcdServer) LeaseGrant(ctx context.Context, r *pb.LeaseGrantRequest) (*
 }
 
 func (s *EtcdServer) LeaseRevoke(ctx context.Context, r *pb.LeaseRevokeRequest) (*pb.LeaseRevokeResponse, error) {
-	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{LeaseRevoke: r})
+	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{LeaseRevoke: r})
 	if err != nil {
 		return nil, err
 	}
@@ -260,7 +300,7 @@ func (s *EtcdServer) LeaseRenew(id lease.LeaseID) (int64, error) {
 }
 
 func (s *EtcdServer) Alarm(ctx context.Context, r *pb.AlarmRequest) (*pb.AlarmResponse, error) {
-	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Alarm: r})
+	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{Alarm: r})
 	if err != nil {
 		return nil, err
 	}
@@ -271,7 +311,7 @@ func (s *EtcdServer) Alarm(ctx context.Context, r *pb.AlarmRequest) (*pb.AlarmRe
 }
 
 func (s *EtcdServer) AuthEnable(ctx context.Context, r *pb.AuthEnableRequest) (*pb.AuthEnableResponse, error) {
-	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{AuthEnable: r})
+	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{AuthEnable: r})
 	if err != nil {
 		return nil, err
 	}
@@ -304,7 +344,7 @@ func (s *EtcdServer) Authenticate(ctx context.Context, r *pb.AuthenticateRequest
 		SimpleToken: st,
 	}
 
-	result, err := s.processInternalRaftRequest(ctx, pb.InternalRaftRequest{Authenticate: internalReq})
+	result, err := s.processInternalRaftRequestOnce(ctx, pb.InternalRaftRequest{Authenticate: internalReq})
 	if err != nil {
 		return nil, err
 	}
@@ -487,31 +527,31 @@ func (s *EtcdServer) isValidSimpleToken(token string) bool {
 	return true
 }
 
-func (s *EtcdServer) usernameFromCtx(ctx context.Context) (string, error) {
+func (s *EtcdServer) authInfoFromCtx(ctx context.Context) (*auth.AuthInfo, error) {
 	md, ok := metadata.FromContext(ctx)
 	if !ok {
-		return "", nil
+		return nil, nil
 	}
 
 	ts, tok := md["token"]
 	if !tok {
-		return "", nil
+		return nil, nil
 	}
 
 	token := ts[0]
 	if !s.isValidSimpleToken(token) {
-		return "", ErrInvalidAuthToken
+		return nil, ErrInvalidAuthToken
 	}
 
-	username, uok := s.AuthStore().UsernameFromToken(token)
+	authInfo, uok := s.AuthStore().AuthInfoFromToken(token)
 	if !uok {
 		plog.Warningf("invalid auth token: %s", token)
-		return "", ErrInvalidAuthToken
+		return nil, ErrInvalidAuthToken
 	}
-	return username, nil
+	return authInfo, nil
 }
 
-func (s *EtcdServer) processInternalRaftRequest(ctx context.Context, r pb.InternalRaftRequest) (*applyResult, error) {
+func (s *EtcdServer) processInternalRaftRequestOnce(ctx context.Context, r pb.InternalRaftRequest) (*applyResult, error) {
 	ai := s.getAppliedIndex()
 	ci := s.getCommittedIndex()
 	if ci > ai+maxGapBetweenApplyAndCommitIndex {
@@ -521,11 +561,15 @@ func (s *EtcdServer) processInternalRaftRequest(ctx context.Context, r pb.Intern
 	r.Header = &pb.RequestHeader{
 		ID: s.reqIDGen.Next(),
 	}
-	username, err := s.usernameFromCtx(ctx)
+
+	authInfo, err := s.authInfoFromCtx(ctx)
 	if err != nil {
 		return nil, err
 	}
-	r.Header.Username = username
+	if authInfo != nil {
+		r.Header.Username = authInfo.Username
+		r.Header.AuthRevision = authInfo.Revision
+	}
 
 	data, err := r.Marshal()
 	if err != nil {
@@ -562,5 +606,18 @@ func (s *EtcdServer) processInternalRaftRequest(ctx context.Context, r pb.Intern
 	}
 }
 
+func (s *EtcdServer) processInternalRaftRequest(ctx context.Context, r pb.InternalRaftRequest) (*applyResult, error) {
+	var result *applyResult
+	var err error
+	for {
+		result, err = s.processInternalRaftRequestOnce(ctx, r)
+		if err != auth.ErrAuthOldRevision {
+			break
+		}
+	}
+
+	return result, err
+}
+
 // Watchable returns a watchable interface attached to the etcdserver.
 func (s *EtcdServer) Watchable() mvcc.WatchableKV { return s.KV() }