access_ee.go

// +build !oss

/*
 * Copyright 2018 Dgraph Labs, Inc. All rights reserved.
 *
 * Licensed under the Dgraph Community License (the "License"); you
 * may not use this file except in compliance with the License. You
 * may obtain a copy of the License at
 *
 *     https://github.com/dgraph-io/dgraph/blob/master/licenses/DCL.txt
 */

package edgraph

import (
	"context"
	"encoding/json"
	"fmt"
	"strconv"
	"sync"
	"time"

	"github.com/dgraph-io/dgo/protos/api"
	"github.com/dgraph-io/dgraph/ee/acl"
	"github.com/dgraph-io/dgraph/gql"
	"github.com/dgraph-io/dgraph/schema"
	"github.com/dgrijalva/jwt-go"
	"github.com/golang/glog"
	otrace "go.opencensus.io/trace"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/peer"
	"google.golang.org/grpc/status"
)

func (s *Server) Login(ctx context.Context,
	request *api.LoginRequest) (*api.Response, error) {
	ctx, span := otrace.StartSpan(ctx, "server.Login")
	defer span.End()

	// record the client ip for this login request
	var addr string
	if ip, ok := peer.FromContext(ctx); ok {
		addr = ip.Addr.String()
		glog.Infof("Login request from: %s", addr)
		span.Annotate([]otrace.Attribute{
			otrace.StringAttribute("client_ip", addr),
		}, "client ip for login")
	}

	user, err := s.authenticateLogin(ctx, request)
	if err != nil {
		errMsg := fmt.Sprintf("authentication from address %s failed: %v", addr, err)
		glog.Errorf(errMsg)
		return nil, fmt.Errorf(errMsg)
	}

	resp := &api.Response{}
	accessJwt, err := getAccessJwt(request.Userid, user.Groups)
	if err != nil {
		errMsg := fmt.Sprintf("unable to get access jwt (userid=%s,addr=%s):%v",
			request.Userid, addr, err)
		glog.Errorf(errMsg)
		return nil, fmt.Errorf(errMsg)
	}
	refreshJwt, err := getRefreshJwt(request.Userid)
	if err != nil {
		errMsg := fmt.Sprintf("unable to get refresh jwt (userid=%s,addr=%s):%v",
			request.Userid, addr, err)
		glog.Errorf(errMsg)
		return nil, fmt.Errorf(errMsg)
	}

	loginJwt := api.Jwt{
		AccessJwt:  accessJwt,
		RefreshJwt: refreshJwt,
	}

	jwtBytes, err := loginJwt.Marshal()
	if err != nil {
		errMsg := fmt.Sprintf("unable to marshal jwt (userid=%s,addr=%s):%v",
			request.Userid, addr, err)
		glog.Errorf(errMsg)
		return nil, fmt.Errorf(errMsg)
	}
	resp.Json = jwtBytes
	return resp, nil
}

// Authenticate the login request using either the refresh token if present, or the
// <userId, password> pair. If authentication passes, query the user's uid and associated groups
// from DB and returns the user object
func (s *Server) authenticateLogin(ctx context.Context, request *api.LoginRequest) (*acl.User,
	error) {
	if err := validateLoginRequest(request); err != nil {
		return nil, fmt.Errorf("invalid login request: %v", err)
	}

	var user *acl.User
	if len(request.RefreshToken) > 0 {
		userData, err := validateToken(request.RefreshToken)
		if err != nil {
			return nil, fmt.Errorf("unable to authenticate the refresh token %v: %v",
				request.RefreshToken, err)
		}

		userId := userData[0]
		user, err = authorizeUser(ctx, userId, "")
		if err != nil {
			return nil, fmt.Errorf("error while querying user with id %v: %v", userId, err)
		}

		if user == nil {
			return nil, fmt.Errorf("unable to authenticate through refresh token: "+
				"user not found for id %v", userId)
		}

		return user, nil
	} else {
		var err error
		user, err = authorizeUser(ctx, request.Userid, request.Password)
		if err != nil {
			return nil, fmt.Errorf("error while querying user with id: %v",
				request.Userid)
		}

		if user == nil {
			return nil, fmt.Errorf("unable to authenticate through password: "+
				"user not found for id %v", request.Userid)
		}
		if !user.PasswordMatch {
			return nil, fmt.Errorf("password mismatch for user: %v", request.Userid)
		}
		return user, nil
	}
}

// verify signature and expiration of the jwt and if validation passes,
// return the extracted userId, and groupIds encoded in the jwt
func validateToken(jwtStr string) (userData []string, err error) {
	token, err := jwt.Parse(jwtStr, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return Config.HmacSecret, nil
	})

	if err != nil {
		return nil, fmt.Errorf("unable to parse jwt token:%v", err)
	}

	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok || !token.Valid {
		return nil, fmt.Errorf("claims in jwt token is not map claims")
	}

	// by default, the MapClaims.Valid will return true if the exp field is not set
	// here we enforce the checking to make sure that the refresh token has not expired
	now := time.Now().Unix()
	if !claims.VerifyExpiresAt(now, true) {
		return nil, fmt.Errorf("jwt token has expired at %v", now)
	}

	userId, ok := claims["userid"].(string)
	if !ok {
		return nil, fmt.Errorf("userid in claims is not a string:%v", userId)
	}

	groups, ok := claims["groups"].([]interface{})
	var groupIds []string
	if ok {
		groupIds = make([]string, 0, len(groups))
		for _, group := range groups {
			groupId, ok := group.(string)
			if !ok {
				glog.Errorf("unable to convert group to string:%v", group)
			}

			groupIds = append(groupIds, groupId)
		}
	}
	return append([]string{userId}, groupIds...), nil
}

// validate that the login request has either the refresh token or the <userid, password> pair
func validateLoginRequest(request *api.LoginRequest) error {
	if request == nil {
		return fmt.Errorf("the request should not be nil")
	}
	// we will use the refresh token for authentication if it's set
	if len(request.RefreshToken) > 0 {
		return nil
	}

	// otherwise make sure both userid and password are set
	if len(request.Userid) == 0 {
		return fmt.Errorf("the userid should not be empty")
	}
	if len(request.Password) == 0 {
		return fmt.Errorf("the password should not be empty")
	}
	return nil
}

// construct an access jwt with the given userid, groupIds, and expiration ttl specified by
// Config.AccessJwtTtl
func getAccessJwt(userId string, groups []acl.Group) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
		"userid": userId,
		"groups": acl.GetGroupIDs(groups),
		// set the jwt exp according to the ttl
		"exp": json.Number(
			strconv.FormatInt(time.Now().Add(Config.AccessJwtTtl).Unix(), 10)),
	})

	jwtString, err := token.SignedString(Config.HmacSecret)
	if err != nil {
		return "", fmt.Errorf("unable to encode jwt to string: %v", err)
	}
	return jwtString, nil
}

// construct a refresh jwt with the given userid, and expiration ttl specified by
// Config.RefreshJwtTtl
func getRefreshJwt(userId string) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
		"userid": userId,
		// set the jwt exp according to the ttl
		"exp": json.Number(
			strconv.FormatInt(time.Now().Add(Config.RefreshJwtTtl).Unix(), 10)),
	})

	jwtString, err := token.SignedString(Config.HmacSecret)
	if err != nil {
		return "", fmt.Errorf("unable to encode jwt to string: %v", err)
	}
	return jwtString, nil
}

const queryUser = `
    query search($userid: string, $password: string){
      user(func: eq(dgraph.xid, $userid)) {
	    uid
        password_match: checkpwd(dgraph.password, $password)
        dgraph.user.group {
          uid
          dgraph.xid
        }
      }
    }`

// query the user with the given userid, and returns associated uid, acl groups,
// and whether the password stored in DB matches the supplied password
func authorizeUser(ctx context.Context, userid string, password string) (user *acl.User,
	err error) {
	queryVars := map[string]string{
		"$userid":   userid,
		"$password": password,
	}
	queryRequest := api.Request{
		Query: queryUser,
		Vars:  queryVars,
	}

	queryResp, err := (&Server{}).doQuery(ctx, &queryRequest)
	if err != nil {
		glog.Errorf("Error while query user with id %s: %v", userid, err)
		return nil, err
	}
	user, err = acl.UnmarshalUser(queryResp, "user")
	if err != nil {
		return nil, err
	}
	return user, nil
}

func RefreshAcls(closeCh <-chan struct{}) {
	if len(Config.HmacSecret) == 0 {
		// the acl feature is not turned on
		return
	}

	ticker := time.NewTicker(Config.AclRefreshInterval)
	defer ticker.Stop()

	// retrieve the full data set of ACLs from the corresponding alpha server, and update the aclCache
	RetrieveAcls := func() error {
		glog.Infof("Retrieving ACLs")
		queryRequest := api.Request{
			Query: queryAcls,
		}

		ctx := context.Background()
		var err error
		queryResp, err := (&Server{}).doQuery(ctx, &queryRequest)
		if err != nil {
			return fmt.Errorf("unable to retrieve acls: %v", err)
		}
		groups, err := acl.UnmarshalGroups(queryResp.GetJson(), "allAcls")
		if err != nil {
			return err
		}

		storedEntries := 0
		for _, group := range groups {
			// convert the serialized acl into a map for easy lookups
			group.MappedAcls, err = acl.UnmarshalAcl([]byte(group.Acls))
			if err != nil {
				glog.Errorf("Error while unmarshalling ACLs for group %v:%v", group, err)
				continue
			}

			storedEntries++
			aclCache.Store(group.GroupID, &group)
		}
		glog.Infof("updated the ACL cache with %d entries", storedEntries)
		return nil
	}

	for {
		select {
		case <-closeCh:
			return
		case <-ticker.C:
			if err := RetrieveAcls(); err != nil {
				glog.Errorf("Error while retrieving acls:%v", err)
			}
		}
	}
}

const queryAcls = `
{
  allAcls(func: has(dgraph.group.acl)) {
    dgraph.xid
    dgraph.group.acl
  }
}
`

// the acl cache mapping group names to the corresponding group acls
var aclCache sync.Map

// clear the aclCache and upsert the admin account
func ResetAcl() {
	if len(Config.HmacSecret) == 0 {
		// the acl feature is not turned on
		return
	}

	aclCache = sync.Map{}
	// upsert the admin account
	adminUser, err := authorizeUser(context.Background(), "admin", "")
	if err != nil {
		glog.Errorf("error while querying the admin account")
		return
	}

	if adminUser != nil {
		// the admin user already exists, no need to create
		return
	}

	// insert the admin user
	createUserNQuads := []*api.NQuad{
		{
			Subject:     "_:newuser",
			Predicate:   "dgraph.xid",
			ObjectValue: &api.Value{Val: &api.Value_StrVal{StrVal: "admin"}},
		},
		{
			Subject:     "_:newuser",
			Predicate:   "dgraph.password",
			ObjectValue: &api.Value{Val: &api.Value_StrVal{StrVal: "password"}},
		}}

	mu := &api.Mutation{
		CommitNow: true,
		Set:       createUserNQuads,
	}

	if _, err := (&Server{}).doMutate(context.Background(), mu); err != nil {
		glog.Errorf("unable to create admin: %v", err)
		return
	}
	glog.Info("Created the admin account with the default password")
}

// extract the userId, groupIds from the accessJwt in the context
func extractUserAndGroups(ctx context.Context) ([]string, error) {
	// extract the jwt and unmarshal the jwt to get the list of groups
	md, ok := metadata.FromIncomingContext(ctx)
	if !ok {
		return nil, fmt.Errorf("no metadata available")
	}
	accessJwt := md.Get("accessJwt")
	if len(accessJwt) == 0 {
		//glog.Infof("no accessJwt available, type is %v", reflect.TypeOf(ctx.Value("accessJwt")))
		return nil, fmt.Errorf("no accessJwt available")
	}

	return validateToken(accessJwt[0])
}

// parse the Schema in the operation and authorize the operation using the aclCache
func authorizeAlter(ctx context.Context, op *api.Operation) error {
	if len(Config.HmacSecret) == 0 {
		// the user has not turned on the acl feature
		return nil
	}

	updates, err := schema.Parse(op.Schema)
	if err != nil {
		return err
	}

	userData, err := extractUserAndGroups(ctx)
	if err != nil {
		return status.Error(codes.Unauthenticated, err.Error())
	}
	userId := userData[0]
	if userId == "admin" {
		// admin is allowed to do anything
		return nil
	}

	// if we get here, we know the user is not admin
	if op.DropAll {
		return fmt.Errorf("only the admin is allowed to drop all predicates")
	}

	groupIds := userData[1:]
	if len(op.DropAttr) > 0 {
		// check that we have the modify permission on the predicate
		if !authorizePredicate(groupIds, op.DropAttr, acl.Modify) {
			return fmt.Errorf("unauthorized to modify the predicate %v", op.DropAttr)
		}
		return nil
	}

	for _, update := range updates {
		if !authorizePredicate(groupIds, update.Predicate, acl.Modify) {
			return fmt.Errorf("unauthorized to modify the predicate %v", update.Predicate)
		}
	}
	return nil
}

func populatePredsFromMutation(nquads []*api.NQuad, preds map[string]struct{}) {
	for _, nquad := range nquads {
		preds[nquad.Predicate] = struct{}{}
	}
}

// authorize the mutation using the aclCache
func authorizeMutation(ctx context.Context, mu *api.Mutation) error {
	if len(Config.HmacSecret) == 0 {
		// the user has not turned on the acl feature
		return nil
	}

	userData, err := extractUserAndGroups(ctx)
	if err != nil {
		return status.Error(codes.Unauthenticated, err.Error())
	}

	userId := userData[0]
	if userId == "admin" {
		// the admin account has access to everything
		return nil
	}

	gmu, err := parseMutationObject(mu)
	if err != nil {
		return err
	}

	preds := make(map[string]struct{})
	populatePredsFromMutation(gmu.Set, preds)

	groupIds := userData[1:]
	for pred := range preds {
		if !authorizePredicate(groupIds, pred, acl.Write) {
			return fmt.Errorf("unauthorized to access the predicate %v", pred)
		}
	}
	return nil
}

func populatePredsFromQuery(gqls []*gql.GraphQuery, preds map[string]struct{}) {
	for _, gq := range gqls {

		if gq.Func != nil {
			preds[gq.Func.Attr] = struct{}{}
		}

		if len(gq.Attr) > 0 {
			preds[gq.Attr] = struct{}{}
		}

		populatePredsFromQuery(gq.Children, preds)
	}
}

// authorize the query using the aclCache
func authorizeQuery(ctx context.Context, req *api.Request) error {
	if len(Config.HmacSecret) == 0 {
		// the user has not turned on the acl feature
		return nil
	}

	userData, err := extractUserAndGroups(ctx)
	if err != nil {
		return status.Error(codes.Unauthenticated, err.Error())
	}

	userId := userData[0]
	if userId == "admin" {
		// the admin account has access to everything
		return nil
	}

	parsedReq, err := gql.Parse(gql.Request{
		Str:       req.Query,
		Variables: req.Vars,
	})
	if err != nil {
		return err
	}

	preds := make(map[string]struct{})
	populatePredsFromQuery(parsedReq.Query, preds)

	groupIds := userData[1:]
	for pred := range preds {
		if !authorizePredicate(groupIds, pred, acl.Read) {
			return status.Error(codes.PermissionDenied,
				fmt.Sprintf("unauthorized to access the predicate %v", pred))
		}
	}

	return nil
}

func authorizePredicate(groups []string, predicate string, operation int32) bool {
	for _, group := range groups {
		if hasAccess(group, predicate, operation) {
			return true
		}
	}
	return false
}

// hasAccess checks the aclCache and returns whether the specified group is authorized to perform
// the operation on the given predicate
func hasAccess(groupId string, predicate string, operation int32) bool {
	entry, found := aclCache.Load(groupId)
	if !found {
		glog.Infof("acl not found")
		return false
	}
	aclGroup := entry.(*acl.Group)
	perm, found := aclGroup.MappedAcls[predicate]
	allowed := found && (perm&operation) != 0
	glog.Infof("authorizing group %v on predicate %v for op %d, allowed %v", groupId,
		predicate, operation, allowed)
	return allowed
}