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"
	"strings"
	"time"

	"github.com/pkg/errors"

	"github.com/dgraph-io/badger/v2/y"

	"github.com/dgraph-io/dgo/v2/protos/api"
	"github.com/dgraph-io/dgraph/ee/acl"
	"github.com/dgraph-io/dgraph/gql"
	"github.com/dgraph-io/dgraph/schema"
	"github.com/dgraph-io/dgraph/worker"
	"github.com/dgraph-io/dgraph/x"
	jwt "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"
)

// Login handles login requests from clients.
func (s *Server) Login(ctx context.Context,
	request *api.LoginRequest) (*api.Response, error) {

	if err := x.HealthCheck(); err != nil {
		return nil, err
	}

	if !worker.EnterpriseEnabled() {
		return nil, errors.New("Enterprise features are disabled. You can enable them by " +
			"supplying the appropriate license file to Dgraph Zero uing the HTTP endpoint.")
	}

	ctx, span := otrace.StartSpan(ctx, "server.Login")
	defer span.End()

	// record the client ip for this login request
	var addr string
	if peerInfo, ok := peer.FromContext(ctx); ok {
		addr = peerInfo.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, errors.Errorf(errMsg)
	}

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

// authenticateLogin authenticates the login request using either the refresh token if present, or
// the <userId, password> pair. If authentication passes, it queries 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, errors.Wrapf(err, "invalid login request")
	}

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

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

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

		glog.Infof("Authenticated user %s through refresh token", userId)
		return user, nil
	}

	// authorize the user using password
	var err error
	user, err = authorizeUser(ctx, request.Userid, request.Password)
	if err != nil {
		return nil, errors.Wrapf(err, "while querying user with id %v",
			request.Userid)
	}

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

// validateToken verifies the signature and expiration of the jwt, and if validation passes,
// returns a slice of strings, where the first element is the extracted userId
// and the rest are groupIds encoded in the jwt.
func validateToken(jwtStr string) ([]string, error) {
	token, err := jwt.Parse(jwtStr, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return worker.Config.HmacSecret, nil
	})

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

	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok || !token.Valid {
		return nil, errors.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, errors.Errorf("Token is expired") // the same error msg that's used inside jwt-go
	}

	userId, ok := claims["userid"].(string)
	if !ok {
		return nil, errors.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 {
				// This shouldn't happen. So, no need to make the client try to refresh the tokens.
				return nil, errors.Errorf("unable to convert group to string:%v", group)
			}

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

// validateLoginRequest validates that the login request has either the refresh token or the
// <user id, password> pair
func validateLoginRequest(request *api.LoginRequest) error {
	if request == nil {
		return errors.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 errors.Errorf("the userid should not be empty")
	}
	if len(request.Password) == 0 {
		return errors.Errorf("the password should not be empty")
	}
	return nil
}

// getAccessJwt constructs an access jwt with the given user id, groupIds,
// and expiration TTL specified by worker.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": time.Now().Add(worker.Config.AccessJwtTtl).Unix(),
	})

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

// getRefreshJwt constructs a refresh jwt with the given user id, and expiration ttl specified by
// worker.Config.RefreshJwtTtl
func getRefreshJwt(userId string) (string, error) {
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
		"userid": userId,
		"exp":    time.Now().Add(worker.Config.RefreshJwtTtl).Unix(),
	})

	jwtString, err := token.SignedString(worker.Config.HmacSecret)
	if err != nil {
		return "", errors.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
        dgraph.xid
        password_match: checkpwd(dgraph.password, $password)
        dgraph.user.group {
          uid
          dgraph.xid
        }
      }
    }`

// authorizeUser queries the user with the given user id, and returns the associated uid,
// acl groups, and whether the password stored in DB matches the supplied password
func authorizeUser(ctx context.Context, userid string, password string) (
	*acl.User, error) {

	queryVars := map[string]string{
		"$userid":   userid,
		"$password": password,
	}
	queryRequest := api.Request{
		Query: queryUser,
		Vars:  queryVars,
	}

	queryResp, err := (&Server{}).doQuery(ctx, &queryRequest, NoAuthorize)
	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
}

// RefreshAcls queries for the ACL triples and refreshes the ACLs accordingly.
func RefreshAcls(closer *y.Closer) {
	defer closer.Done()
	if len(worker.Config.HmacSecret) == 0 {
		// the acl feature is not turned on
		return
	}

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

	// retrieve the full data set of ACLs from the corresponding alpha server, and update the
	// aclCachePtr
	retrieveAcls := func() error {
		glog.V(3).Infof("Refreshing ACLs")
		queryRequest := api.Request{
			Query:    queryAcls,
			ReadOnly: true,
		}

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

		aclCachePtr.update(groups)
		glog.V(3).Infof("Updated the ACL cache")
		return nil
	}

	for {
		select {
		case <-closer.HasBeenClosed():
			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
  }
}
`

// ResetAcl clears the aclCachePtr and upserts the Groot account.
func ResetAcl() {
	if len(worker.Config.HmacSecret) == 0 {
		// The acl feature is not turned on.
		return
	}

	upsertGuardians := func(ctx context.Context) error {
		query := fmt.Sprintf(`
			{
				guid as var(func: eq(dgraph.xid, "%s"))
			}
		`, x.AdminGId)
		groupNQuads := acl.CreateGroupNQuads(x.AdminGId)
		req := &api.Request{
			CommitNow: true,
			Query:     query,
			Mutations: []*api.Mutation{
				{
					Set:  groupNQuads,
					Cond: "@if(eq(len(guid), 0))",
				},
			},
		}

		_, err := (&Server{}).doQuery(ctx, req, NoAuthorize)
		if err != nil {
			return errors.Wrapf(err, "while upserting group with id %s", x.AdminGId)
		}

		glog.Infof("Successfully upserted the guardian group")
		return nil
	}

	upsertGroot := func(ctx context.Context) error {
		query := fmt.Sprintf(`
			{
				grootid as var(func: eq(dgraph.xid, "%s"))
                                guid as var(func: eq(dgraph.xid, "%s"))
			}
		`, x.GrootId, x.AdminGId)
		userNQuads := acl.CreateUserNQuads(x.GrootId, "password")
		userNQuads = append(userNQuads, &api.NQuad{
			Subject:   "_:newuser",
			Predicate: "dgraph.user.group",
			ObjectId:  "uid(guid)",
		})
		req := &api.Request{
			CommitNow: true,
			Query:     query,
			Mutations: []*api.Mutation{
				{
					Set: userNQuads,
					// Assuming that if groot exists, it is in guardian group
					Cond: "@if(eq(len(grootid), 0) and gt(len(guid), 0))",
				},
			},
		}

		_, err := (&Server{}).doQuery(ctx, req, NoAuthorize)
		if err != nil {
			return errors.Wrapf(err, "while upserting user with id %s", x.GrootId)
		}

		glog.Infof("Successfully upserted groot account")
		return nil
	}

	for {
		ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
		defer cancel()
		if err := upsertGuardians(ctx); err != nil {
			glog.Infof("Unable to upsert the guardian group. Error: %v", err)
			time.Sleep(100 * time.Millisecond)
			continue
		}
		break
	}

	for {
		ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
		defer cancel()
		if err := upsertGroot(ctx); err != nil {
			glog.Infof("Unable to upsert the groot account. Error: %v", err)
			time.Sleep(100 * time.Millisecond)
			continue
		}
		break
	}
}

var errNoJwt = errors.New("no accessJwt available")

// 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, errNoJwt
	}
	accessJwt := md.Get("accessJwt")
	if len(accessJwt) == 0 {
		return nil, errNoJwt
	}

	return validateToken(accessJwt[0])
}

func authorizePreds(userId string, groupIds, preds []string, aclOp *acl.Operation) error {
	for _, pred := range preds {
		if err := aclCachePtr.authorizePredicate(groupIds, pred, aclOp); err != nil {
			logAccess(&accessEntry{
				userId:    userId,
				groups:    groupIds,
				preds:     preds,
				operation: aclOp,
				allowed:   false,
			})

			var op string
			switch aclOp.Name {
			case acl.OpModify:
				op = "alter"
			case acl.OpWrite:
				op = "mutate"
			case acl.OpRead:
				op = "query"
			}

			return status.Errorf(codes.PermissionDenied,
				"unauthorized to %s the predicate: %v", op, err)
		}
	}
	return nil
}

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

	// extract the list of predicates from the operation object
	var preds []string
	if len(op.DropAttr) > 0 {
		preds = []string{op.DropAttr}
	} else if op.DropOp == api.Operation_ATTR && len(op.DropValue) > 0 {
		preds = []string{op.DropValue}
	} else {
		update, err := schema.Parse(op.Schema)
		if err != nil {
			return err
		}

		for _, u := range update.Preds {
			preds = append(preds, u.Predicate)
		}
	}

	var userId string
	var groupIds []string

	// doAuthorizeAlter checks if alter of all the predicates are allowed
	// as a byproduct, it also sets the userId, groups variables
	doAuthorizeAlter := func() error {
		userData, err := extractUserAndGroups(ctx)
		if err == errNoJwt {
			// treat the user as an anonymous guest who has not joined any group yet
			// such a user can still get access to predicates that have no ACL rule defined, per the
			// fail open approach
		} else if err != nil {
			return status.Error(codes.Unauthenticated, err.Error())
		} else {
			userId = userData[0]
			groupIds = userData[1:]

			if x.IsSuperUser(groupIds) {
				// Members of guardian group are allowed to alter anything.
				return nil
			}
		}

		// if we get here, we know the user is not Groot.
		if isDropAll(op) || op.DropOp == api.Operation_DATA {
			return errors.Errorf(
				"only Groot is allowed to drop all data, but the current user is %s", userId)
		}

		return authorizePreds(userId, groupIds, preds, acl.Modify)
	}

	err := doAuthorizeAlter()
	span := otrace.FromContext(ctx)
	if span != nil {
		span.Annotatef(nil, (&accessEntry{
			userId:    userId,
			groups:    groupIds,
			preds:     preds,
			operation: acl.Modify,
			allowed:   err == nil,
		}).String())
	}

	return err
}

// parsePredsFromMutation returns a union set of all the predicate names in the input nquads
func parsePredsFromMutation(nquads []*api.NQuad) []string {
	// use a map to dedup predicates
	predsMap := make(map[string]struct{})
	for _, nquad := range nquads {
		predsMap[nquad.Predicate] = struct{}{}
	}

	preds := make([]string, 0, len(predsMap))
	for pred := range predsMap {
		preds = append(preds, pred)
	}

	return preds
}

func isAclPredMutation(nquads []*api.NQuad) bool {
	for _, nquad := range nquads {
		if nquad.Predicate == "dgraph.group.acl" && nquad.ObjectValue != nil {
			// this mutation is trying to change the permission of some predicate
			// check if the predicate list contains an ACL predicate
			if _, ok := nquad.ObjectValue.Val.(*api.Value_BytesVal); ok {
				aclBytes := nquad.ObjectValue.Val.(*api.Value_BytesVal)
				var aclsToChange []acl.Acl
				err := json.Unmarshal(aclBytes.BytesVal, &aclsToChange)
				if err != nil {
					glog.Errorf(fmt.Sprintf("Unable to unmalshal bytes under the dgraph.group.acl "+
						"predicate:	%v", err))
					continue
				}
				for _, aclToChange := range aclsToChange {
					if x.IsAclPredicate(aclToChange.Predicate) {
						return true
					}
				}
			}
		}
	}
	return false
}

// authorizeMutation authorizes the mutation using the aclCachePtr
func authorizeMutation(ctx context.Context, gmu *gql.Mutation) error {
	if len(worker.Config.HmacSecret) == 0 {
		// the user has not turned on the acl feature
		return nil
	}

	preds := parsePredsFromMutation(gmu.Set)
	// Del predicates weren't included before.
	// A bug probably since f115de2eb6a40d882a86c64da68bf5c2a33ef69a
	preds = append(preds, parsePredsFromMutation(gmu.Del)...)

	var userId string
	var groupIds []string
	// doAuthorizeMutation checks if modification of all the predicates are allowed
	// as a byproduct, it also sets the userId and groups
	doAuthorizeMutation := func() error {
		userData, err := extractUserAndGroups(ctx)
		if err == errNoJwt {
			// treat the user as an anonymous guest who has not joined any group yet
			// such a user can still get access to predicates that have no ACL rule defined
		} else if err != nil {
			return status.Error(codes.Unauthenticated, err.Error())
		} else {
			userId = userData[0]
			groupIds = userData[1:]

			if x.IsSuperUser(groupIds) {
				// Members of guardian group are allowed to mutate anything
				// except the permission of the acl predicates
				if isAclPredMutation(gmu.Set) {
					return errors.Errorf("the permission of ACL predicates can not be changed")
				} else if isAclPredMutation(gmu.Del) {
					// Even members of gurardian group can't delete ACL predicates
					return errors.Errorf("ACL predicates can't be deleted")
				}
				return nil
			}
		}

		return authorizePreds(userId, groupIds, preds, acl.Write)
	}

	err := doAuthorizeMutation()
	span := otrace.FromContext(ctx)
	if span != nil {
		span.Annotatef(nil, (&accessEntry{
			userId:    userId,
			groups:    groupIds,
			preds:     preds,
			operation: acl.Write,
			allowed:   err == nil,
		}).String())
	}

	return err
}

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

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

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

		for _, childPred := range parsePredsFromQuery(gq.Children) {
			predsMap[childPred] = struct{}{}
		}
	}

	preds := make([]string, 0, len(predsMap))
	for pred := range predsMap {
		preds = append(preds, pred)
	}
	return preds
}

type accessEntry struct {
	userId    string
	groups    []string
	preds     []string
	operation *acl.Operation
	allowed   bool
}

func (log *accessEntry) String() string {
	return fmt.Sprintf("ACL-LOG Authorizing user %q with groups %q on predicates %q "+
		"for %q, allowed:%v", log.userId, strings.Join(log.groups, ","),
		strings.Join(log.preds, ","), log.operation.Name, log.allowed)
}

func logAccess(log *accessEntry) {
	glog.V(1).Infof(log.String())
}

//authorizeQuery authorizes the query using the aclCachePtr
func authorizeQuery(ctx context.Context, parsedReq *gql.Result) error {
	if len(worker.Config.HmacSecret) == 0 {
		// the user has not turned on the acl feature
		return nil
	}

	var userId string
	var groupIds []string
	preds := parsePredsFromQuery(parsedReq.Query)
	isSchemaQuery := parsedReq != nil && parsedReq.Schema != nil

	doAuthorizeQuery := func() error {
		userData, err := extractUserAndGroups(ctx)
		if err == errNoJwt {
			// Do not allow schema queries unless the user has logged in.
			if isSchemaQuery {
				return status.Error(codes.Unauthenticated, err.Error())
			}

			// Treat the user as an anonymous guest who has not joined any group yet
			// such a user can still get access to predicates that have no ACL rule defined.
		} else if err != nil {
			return status.Error(codes.Unauthenticated, err.Error())
		} else {
			userId = userData[0]
			groupIds = userData[1:]

			if x.IsSuperUser(groupIds) {
				// Members of guardian groups are allowed to query anything.
				return nil
			}
		}

		return authorizePreds(userId, groupIds, preds, acl.Read)
	}

	err := doAuthorizeQuery()
	if span := otrace.FromContext(ctx); span != nil {
		span.Annotatef(nil, (&accessEntry{
			userId:    userId,
			groups:    groupIds,
			preds:     preds,
			operation: acl.Read,
			allowed:   err == nil,
		}).String())
	}

	return err
}