/*
 * MinIO Cloud Storage, (C) 2018-2019 MinIO, Inc.
 *
 * 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 cmd

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	humanize "github.com/dustin/go-humanize"
	"github.com/minio/minio-go/v7/pkg/set"
	"github.com/minio/minio/cmd/config"
	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/auth"
	iampolicy "github.com/minio/minio/pkg/iam/policy"
	"github.com/minio/minio/pkg/madmin"
	"github.com/minio/minio/pkg/retry"
)

// UsersSysType - defines the type of users and groups system that is
// active on the server.
type UsersSysType string

// Types of users configured in the server.
const (
	// This mode uses the internal users system in MinIO.
	MinIOUsersSysType UsersSysType = "MinIOUsersSys"

	// This mode uses users and groups from a configured LDAP
	// server.
	LDAPUsersSysType UsersSysType = "LDAPUsersSys"
)

const (
	// IAM configuration directory.
	iamConfigPrefix = minioConfigPrefix + "/iam"

	// IAM users directory.
	iamConfigUsersPrefix = iamConfigPrefix + "/users/"

	// IAM service accounts directory.
	iamConfigServiceAccountsPrefix = iamConfigPrefix + "/service-accounts/"

	// IAM groups directory.
	iamConfigGroupsPrefix = iamConfigPrefix + "/groups/"

	// IAM policies directory.
	iamConfigPoliciesPrefix = iamConfigPrefix + "/policies/"

	// IAM sts directory.
	iamConfigSTSPrefix = iamConfigPrefix + "/sts/"

	// IAM Policy DB prefixes.
	iamConfigPolicyDBPrefix                = iamConfigPrefix + "/policydb/"
	iamConfigPolicyDBUsersPrefix           = iamConfigPolicyDBPrefix + "users/"
	iamConfigPolicyDBSTSUsersPrefix        = iamConfigPolicyDBPrefix + "sts-users/"
	iamConfigPolicyDBServiceAccountsPrefix = iamConfigPolicyDBPrefix + "service-accounts/"
	iamConfigPolicyDBGroupsPrefix          = iamConfigPolicyDBPrefix + "groups/"

	// IAM identity file which captures identity credentials.
	iamIdentityFile = "identity.json"

	// IAM policy file which provides policies for each users.
	iamPolicyFile = "policy.json"

	// IAM group members file
	iamGroupMembersFile = "members.json"

	// IAM format file
	iamFormatFile = "format.json"

	iamFormatVersion1 = 1
)

const (
	statusEnabled  = "enabled"
	statusDisabled = "disabled"
)

type iamFormat struct {
	Version int `json:"version"`
}

func newIAMFormatVersion1() iamFormat {
	return iamFormat{Version: iamFormatVersion1}
}

func getIAMFormatFilePath() string {
	return iamConfigPrefix + SlashSeparator + iamFormatFile
}

func getUserIdentityPath(user string, userType IAMUserType) string {
	var basePath string
	switch userType {
	case srvAccUser:
		basePath = iamConfigServiceAccountsPrefix
	case stsUser:
		basePath = iamConfigSTSPrefix
	default:
		basePath = iamConfigUsersPrefix
	}
	return pathJoin(basePath, user, iamIdentityFile)
}

func getGroupInfoPath(group string) string {
	return pathJoin(iamConfigGroupsPrefix, group, iamGroupMembersFile)
}

func getPolicyDocPath(name string) string {
	return pathJoin(iamConfigPoliciesPrefix, name, iamPolicyFile)
}

func getMappedPolicyPath(name string, userType IAMUserType, isGroup bool) string {
	if isGroup {
		return pathJoin(iamConfigPolicyDBGroupsPrefix, name+".json")
	}
	switch userType {
	case srvAccUser:
		return pathJoin(iamConfigPolicyDBServiceAccountsPrefix, name+".json")
	case stsUser:
		return pathJoin(iamConfigPolicyDBSTSUsersPrefix, name+".json")
	default:
		return pathJoin(iamConfigPolicyDBUsersPrefix, name+".json")
	}
}

// UserIdentity represents a user's secret key and their status
type UserIdentity struct {
	Version     int              `json:"version"`
	Credentials auth.Credentials `json:"credentials"`
}

func newUserIdentity(cred auth.Credentials) UserIdentity {
	return UserIdentity{Version: 1, Credentials: cred}
}

// GroupInfo contains info about a group
type GroupInfo struct {
	Version int      `json:"version"`
	Status  string   `json:"status"`
	Members []string `json:"members"`
}

func newGroupInfo(members []string) GroupInfo {
	return GroupInfo{Version: 1, Status: statusEnabled, Members: members}
}

// MappedPolicy represents a policy name mapped to a user or group
type MappedPolicy struct {
	Version  int    `json:"version"`
	Policies string `json:"policy"`
}

// converts a mapped policy into a slice of distinct policies
func (mp MappedPolicy) toSlice() []string {
	var policies []string
	for _, policy := range strings.Split(mp.Policies, ",") {
		policy = strings.TrimSpace(policy)
		if policy == "" {
			continue
		}
		policies = append(policies, policy)
	}
	return policies
}

func (mp MappedPolicy) policySet() set.StringSet {
	var policies []string
	for _, policy := range strings.Split(mp.Policies, ",") {
		policy = strings.TrimSpace(policy)
		if policy == "" {
			continue
		}
		policies = append(policies, policy)
	}
	return set.CreateStringSet(policies...)
}

func newMappedPolicy(policy string) MappedPolicy {
	return MappedPolicy{Version: 1, Policies: policy}
}

// IAMSys - config system.
type IAMSys struct {
	usersSysType UsersSysType

	// map of policy names to policy definitions
	iamPolicyDocsMap map[string]iampolicy.Policy
	// map of usernames to credentials
	iamUsersMap map[string]auth.Credentials
	// map of group names to group info
	iamGroupsMap map[string]GroupInfo
	// map of user names to groups they are a member of
	iamUserGroupMemberships map[string]set.StringSet
	// map of usernames/temporary access keys to policy names
	iamUserPolicyMap map[string]MappedPolicy
	// map of group names to policy names
	iamGroupPolicyMap map[string]MappedPolicy

	// Persistence layer for IAM subsystem
	store         IAMStorageAPI
	storeFallback bool
}

// IAMUserType represents a user type inside MinIO server
type IAMUserType int

const (
	regularUser IAMUserType = iota
	stsUser
	srvAccUser
)

// IAMStorageAPI defines an interface for the IAM persistence layer
type IAMStorageAPI interface {
	lock()
	unlock()

	rlock()
	runlock()

	migrateBackendFormat(context.Context) error

	loadPolicyDoc(policy string, m map[string]iampolicy.Policy) error
	loadPolicyDocs(ctx context.Context, m map[string]iampolicy.Policy) error

	loadUser(user string, userType IAMUserType, m map[string]auth.Credentials) error
	loadUsers(ctx context.Context, userType IAMUserType, m map[string]auth.Credentials) error

	loadGroup(group string, m map[string]GroupInfo) error
	loadGroups(ctx context.Context, m map[string]GroupInfo) error

	loadMappedPolicy(name string, userType IAMUserType, isGroup bool, m map[string]MappedPolicy) error
	loadMappedPolicies(ctx context.Context, userType IAMUserType, isGroup bool, m map[string]MappedPolicy) error

	loadAll(context.Context, *IAMSys) error

	saveIAMConfig(item interface{}, path string) error
	loadIAMConfig(item interface{}, path string) error
	deleteIAMConfig(path string) error

	savePolicyDoc(policyName string, p iampolicy.Policy) error
	saveMappedPolicy(name string, userType IAMUserType, isGroup bool, mp MappedPolicy) error
	saveUserIdentity(name string, userType IAMUserType, u UserIdentity) error
	saveGroupInfo(group string, gi GroupInfo) error

	deletePolicyDoc(policyName string) error
	deleteMappedPolicy(name string, userType IAMUserType, isGroup bool) error
	deleteUserIdentity(name string, userType IAMUserType) error
	deleteGroupInfo(name string) error

	watch(context.Context, *IAMSys)
}

// LoadGroup - loads a specific group from storage, and updates the
// memberships cache. If the specified group does not exist in
// storage, it is removed from in-memory maps as well - this
// simplifies the implementation for group removal. This is called
// only via IAM notifications.
func (sys *IAMSys) LoadGroup(objAPI ObjectLayer, group string) error {
	if objAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	if globalEtcdClient != nil {
		// Watch APIs cover this case, so nothing to do.
		return nil
	}

	sys.store.lock()
	defer sys.store.unlock()

	err := sys.store.loadGroup(group, sys.iamGroupsMap)
	if err != nil && err != errNoSuchGroup {
		return err
	}

	if err == errNoSuchGroup {
		// group does not exist - so remove from memory.
		sys.removeGroupFromMembershipsMap(group)
		delete(sys.iamGroupsMap, group)
		delete(sys.iamGroupPolicyMap, group)
		return nil
	}

	gi := sys.iamGroupsMap[group]

	// Updating the group memberships cache happens in two steps:
	//
	// 1. Remove the group from each user's list of memberships.
	// 2. Add the group to each member's list of memberships.
	//
	// This ensures that regardless of members being added or
	// removed, the cache stays current.
	sys.removeGroupFromMembershipsMap(group)
	sys.updateGroupMembershipsMap(group, &gi)
	return nil
}

// LoadPolicy - reloads a specific canned policy from backend disks or etcd.
func (sys *IAMSys) LoadPolicy(objAPI ObjectLayer, policyName string) error {
	if objAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	if globalEtcdClient == nil {
		return sys.store.loadPolicyDoc(policyName, sys.iamPolicyDocsMap)
	}

	// When etcd is set, we use watch APIs so this code is not needed.
	return nil
}

// LoadPolicyMapping - loads the mapped policy for a user or group
// from storage into server memory.
func (sys *IAMSys) LoadPolicyMapping(objAPI ObjectLayer, userOrGroup string, isGroup bool) error {
	if objAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	if globalEtcdClient == nil {
		var err error
		if isGroup {
			err = sys.store.loadMappedPolicy(userOrGroup, regularUser, isGroup, sys.iamGroupPolicyMap)
		} else {
			err = sys.store.loadMappedPolicy(userOrGroup, regularUser, isGroup, sys.iamUserPolicyMap)
		}

		// Ignore policy not mapped error
		if err != nil && err != errNoSuchPolicy {
			return err
		}
	}
	// When etcd is set, we use watch APIs so this code is not needed.
	return nil
}

// LoadUser - reloads a specific user from backend disks or etcd.
func (sys *IAMSys) LoadUser(objAPI ObjectLayer, accessKey string, userType IAMUserType) error {
	if objAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	if globalEtcdClient == nil {
		err := sys.store.loadUser(accessKey, userType, sys.iamUsersMap)
		if err != nil {
			return err
		}
		err = sys.store.loadMappedPolicy(accessKey, userType, false, sys.iamUserPolicyMap)
		// Ignore policy not mapped error
		if err != nil && err != errNoSuchPolicy {
			return err
		}
	}
	// When etcd is set, we use watch APIs so this code is not needed.
	return nil
}

// LoadServiceAccount - reloads a specific service account from backend disks or etcd.
func (sys *IAMSys) LoadServiceAccount(accessKey string) error {
	if sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	if globalEtcdClient == nil {
		err := sys.store.loadUser(accessKey, srvAccUser, sys.iamUsersMap)
		if err != nil {
			return err
		}
	}
	// When etcd is set, we use watch APIs so this code is not needed.
	return nil
}

// Perform IAM configuration migration.
func (sys *IAMSys) doIAMConfigMigration(ctx context.Context) error {
	return sys.store.migrateBackendFormat(ctx)
}

// Loads IAM users and policies in background, any un-handled
// error means this code can potentially crash the server
// in such a situation manual intervention is necessary.
func startBackgroundIAMLoad(ctx context.Context) {
	go globalIAMSys.Init(ctx, newObjectLayerWithoutSafeModeFn())
}

// Init - initializes config system by reading entries from config/iam
func (sys *IAMSys) Init(ctx context.Context, objAPI ObjectLayer) {
	if objAPI == nil {
		logger.LogIf(ctx, errServerNotInitialized)
		return
	}

	if globalEtcdClient == nil {
		sys.store = newIAMObjectStore(ctx, objAPI)
	} else {
		sys.store = newIAMEtcdStore(ctx)
	}

	if globalLDAPConfig.Enabled {
		sys.EnableLDAPSys()
	}

	retryCtx, cancel := context.WithCancel(ctx)

	// Indicate to our routine to exit cleanly upon return.
	defer cancel()

	// Hold the lock for migration only.
	txnLk := objAPI.NewNSLock(retryCtx, minioMetaBucket, minioConfigPrefix+"/iam.lock")

	// Initializing IAM sub-system needs a retry mechanism for
	// the following reasons:
	//  - Read quorum is lost just after the initialization
	//    of the object layer.
	//  - Write quorum not met when upgrading configuration
	//    version is needed, migration is needed etc.
	rquorum := InsufficientReadQuorum{}
	wquorum := InsufficientWriteQuorum{}

	for range retry.NewTimerWithJitter(retryCtx, time.Second, 5*time.Second, retry.MaxJitter) {
		// let one of the server acquire the lock, if not let them timeout.
		// which shall be retried again by this loop.
		if err := txnLk.GetLock(newDynamicTimeout(3*time.Second, 5*time.Second)); err != nil {
			logger.Info("Waiting for all MinIO IAM sub-system to be initialized.. trying to acquire lock")
			continue
		}

		if globalEtcdClient != nil {
			// ****  WARNING ****
			// Migrating to encrypted backend on etcd should happen before initialization of
			// IAM sub-system, make sure that we do not move the above codeblock elsewhere.
			if err := migrateIAMConfigsEtcdToEncrypted(ctx, globalEtcdClient); err != nil {
				txnLk.Unlock()
				logger.LogIf(ctx, fmt.Errorf("Unable to decrypt an encrypted ETCD backend for IAM users and policies: %w", err))
				logger.LogIf(ctx, errors.New("IAM sub-system is partially initialized, some users may not be available"))
				return
			}
		}

		// These messages only meant primarily for distributed setup, so only log during distributed setup.
		if globalIsDistErasure {
			logger.Info("Waiting for all MinIO IAM sub-system to be initialized.. lock acquired")
		}

		// Migrate IAM configuration, if necessary.
		if err := sys.doIAMConfigMigration(ctx); err != nil {
			txnLk.Unlock()
			if errors.Is(err, errDiskNotFound) ||
				errors.Is(err, errConfigNotFound) ||
				errors.Is(err, context.Canceled) ||
				errors.Is(err, context.DeadlineExceeded) ||
				errors.As(err, &rquorum) ||
				errors.As(err, &wquorum) ||
				isErrBucketNotFound(err) {
				logger.Info("Waiting for all MinIO IAM sub-system to be initialized.. possible cause (%v)", err)
				continue
			}
			logger.LogIf(ctx, fmt.Errorf("Unable to migrate IAM users and policies to new format: %w", err))
			logger.LogIf(ctx, errors.New("IAM sub-system is partially initialized, some users may not be available"))
			return
		}

		// Successfully migrated, proceed to load the users.
		txnLk.Unlock()
		break
	}

	err := sys.store.loadAll(ctx, sys)

	// Invalidate the old cred always, even upon error to avoid any leakage.
	globalOldCred = auth.Credentials{}

	if err != nil {
		logger.LogIf(ctx, fmt.Errorf("Unable to initialize IAM sub-system, some users may not be available %w", err))
	}

	go sys.store.watch(ctx, sys)
}

// DeletePolicy - deletes a canned policy from backend or etcd.
func (sys *IAMSys) DeletePolicy(policyName string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	if policyName == "" {
		return errInvalidArgument
	}

	sys.store.lock()
	defer sys.store.unlock()

	err := sys.store.deletePolicyDoc(policyName)
	if err == errNoSuchPolicy {
		// Ignore error if policy is already deleted.
		err = nil
	}

	delete(sys.iamPolicyDocsMap, policyName)

	// Delete user-policy mappings that will no longer apply
	for u, mp := range sys.iamUserPolicyMap {
		pset := mp.policySet()
		if pset.Contains(policyName) {
			cr, ok := sys.iamUsersMap[u]
			if !ok {
				// This case cannot happen
				return errNoSuchUser
			}
			pset.Remove(policyName)
			// User is from STS if the cred are temporary
			if cr.IsTemp() {
				sys.policyDBSet(u, strings.Join(pset.ToSlice(), ","), stsUser, false)
			} else {
				sys.policyDBSet(u, strings.Join(pset.ToSlice(), ","), regularUser, false)
			}
		}
	}

	// Delete group-policy mappings that will no longer apply
	for g, mp := range sys.iamGroupPolicyMap {
		pset := mp.policySet()
		if pset.Contains(policyName) {
			pset.Remove(policyName)
			sys.policyDBSet(g, strings.Join(pset.ToSlice(), ","), regularUser, true)
		}
	}

	return err
}

// InfoPolicy - expands the canned policy into its JSON structure.
func (sys *IAMSys) InfoPolicy(policyName string) (iampolicy.Policy, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return iampolicy.Policy{}, errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	v, ok := sys.iamPolicyDocsMap[policyName]
	if !ok {
		return iampolicy.Policy{}, errNoSuchPolicy
	}

	return v, nil
}

// ListPolicies - lists all canned policies.
func (sys *IAMSys) ListPolicies() (map[string]iampolicy.Policy, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return nil, errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	if sys.storeFallback {
		return nil, errIAMNotInitialized
	}

	policyDocsMap := make(map[string]iampolicy.Policy, len(sys.iamPolicyDocsMap))
	for k, v := range sys.iamPolicyDocsMap {
		policyDocsMap[k] = v
	}

	return policyDocsMap, nil
}

// SetPolicy - sets a new name policy.
func (sys *IAMSys) SetPolicy(policyName string, p iampolicy.Policy) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	if p.IsEmpty() || policyName == "" {
		return errInvalidArgument
	}

	sys.store.lock()
	defer sys.store.unlock()

	if err := sys.store.savePolicyDoc(policyName, p); err != nil {
		return err
	}

	sys.iamPolicyDocsMap[policyName] = p
	return nil
}

// DeleteUser - delete user (only for long-term users not STS users).
func (sys *IAMSys) DeleteUser(accessKey string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	// First we remove the user from their groups.
	userInfo, getErr := sys.GetUserInfo(accessKey)
	if getErr != nil {
		return getErr
	}

	for _, group := range userInfo.MemberOf {
		removeErr := sys.RemoveUsersFromGroup(group, []string{accessKey})
		if removeErr != nil {
			return removeErr
		}
	}

	// Next we can remove the user from memory and IAM store
	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	// Delete any service accounts if any first.
	for _, u := range sys.iamUsersMap {
		if u.IsServiceAccount() {
			if u.ParentUser == accessKey {
				_ = sys.store.deleteUserIdentity(u.AccessKey, srvAccUser)
				delete(sys.iamUsersMap, u.AccessKey)
			}
		}
	}

	// It is ok to ignore deletion error on the mapped policy
	sys.store.deleteMappedPolicy(accessKey, regularUser, false)
	err := sys.store.deleteUserIdentity(accessKey, regularUser)
	if err == errNoSuchUser {
		// ignore if user is already deleted.
		err = nil
	}

	delete(sys.iamUsersMap, accessKey)
	delete(sys.iamUserPolicyMap, accessKey)

	return err
}

// returns comma separated policy string, from an input policy
// after validating if there are any current policies which exist
// on MinIO corresponding to the input.
func (sys *IAMSys) currentPolicies(policyName string) string {
	sys.store.rlock()
	defer sys.store.runlock()

	var policies []string
	mp := newMappedPolicy(policyName)
	for _, policy := range mp.toSlice() {
		_, found := sys.iamPolicyDocsMap[policy]
		if found {
			policies = append(policies, policy)
		}
	}
	return strings.Join(policies, ",")
}

// SetTempUser - set temporary user credentials, these credentials have an expiry.
func (sys *IAMSys) SetTempUser(accessKey string, cred auth.Credentials, policyName string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	// If OPA is not set we honor any policy claims for this
	// temporary user which match with pre-configured canned
	// policies for this server.
	if globalPolicyOPA == nil && policyName != "" {
		var availablePolicies []iampolicy.Policy
		mp := newMappedPolicy(policyName)
		for _, policy := range mp.toSlice() {
			p, found := sys.iamPolicyDocsMap[policy]
			if found {
				availablePolicies = append(availablePolicies, p)
			}
		}

		combinedPolicy := availablePolicies[0]
		for i := 1; i < len(availablePolicies); i++ {
			combinedPolicy.Statements = append(combinedPolicy.Statements,
				availablePolicies[i].Statements...)
		}

		if combinedPolicy.IsEmpty() {
			delete(sys.iamUserPolicyMap, accessKey)
			return nil
		}

		if err := sys.store.saveMappedPolicy(accessKey, stsUser, false, mp); err != nil {
			return err
		}

		sys.iamUserPolicyMap[accessKey] = mp
	}

	u := newUserIdentity(cred)
	if err := sys.store.saveUserIdentity(accessKey, stsUser, u); err != nil {
		return err
	}

	sys.iamUsersMap[accessKey] = cred
	return nil
}

// ListUsers - list all users.
func (sys *IAMSys) ListUsers() (map[string]madmin.UserInfo, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return nil, errServerNotInitialized
	}

	var users = make(map[string]madmin.UserInfo)

	sys.store.rlock()
	defer sys.store.runlock()

	if sys.usersSysType != MinIOUsersSysType {
		return nil, errIAMActionNotAllowed
	}

	if sys.storeFallback {
		return nil, errIAMNotInitialized
	}

	for k, v := range sys.iamUsersMap {
		if !v.IsTemp() && !v.IsServiceAccount() {
			users[k] = madmin.UserInfo{
				PolicyName: sys.iamUserPolicyMap[k].Policies,
				Status: func() madmin.AccountStatus {
					if v.IsValid() {
						return madmin.AccountEnabled
					}
					return madmin.AccountDisabled
				}(),
			}
		}
	}

	return users, nil
}

// IsTempUser - returns if given key is a temporary user.
func (sys *IAMSys) IsTempUser(name string) (bool, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return false, errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	cred, found := sys.iamUsersMap[name]
	if !found {
		return false, errNoSuchUser
	}

	return cred.IsTemp(), nil
}

// IsServiceAccount - returns if given key is a service account
func (sys *IAMSys) IsServiceAccount(name string) (bool, string, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return false, "", errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	cred, found := sys.iamUsersMap[name]
	if !found {
		return false, "", errNoSuchUser
	}

	if cred.IsServiceAccount() {
		return true, cred.ParentUser, nil
	}

	return false, "", nil
}

// GetUserInfo - get info on a user.
func (sys *IAMSys) GetUserInfo(name string) (u madmin.UserInfo, err error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return u, errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	if sys.usersSysType != MinIOUsersSysType {
		// If the user has a mapped policy or is a member of a group, we
		// return that info. Otherwise we return error.
		mappedPolicy, ok1 := sys.iamUserPolicyMap[name]
		memberships, ok2 := sys.iamUserGroupMemberships[name]
		if !ok1 && !ok2 {
			return u, errNoSuchUser
		}
		return madmin.UserInfo{
			PolicyName: mappedPolicy.Policies,
			MemberOf:   memberships.ToSlice(),
		}, nil
	}

	cred, found := sys.iamUsersMap[name]
	if !found {
		return u, errNoSuchUser
	}

	if cred.IsTemp() || cred.IsServiceAccount() {
		return u, errIAMActionNotAllowed
	}

	u = madmin.UserInfo{
		PolicyName: sys.iamUserPolicyMap[name].Policies,
		Status: func() madmin.AccountStatus {
			if cred.IsValid() {
				return madmin.AccountEnabled
			}
			return madmin.AccountDisabled
		}(),
		MemberOf: sys.iamUserGroupMemberships[name].ToSlice(),
	}
	return u, nil
}

// SetUserStatus - sets current user status, supports disabled or enabled.
func (sys *IAMSys) SetUserStatus(accessKey string, status madmin.AccountStatus) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	if status != madmin.AccountEnabled && status != madmin.AccountDisabled {
		return errInvalidArgument
	}

	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	cred, ok := sys.iamUsersMap[accessKey]
	if !ok {
		return errNoSuchUser
	}

	if cred.IsTemp() || cred.IsServiceAccount() {
		return errIAMActionNotAllowed
	}

	uinfo := newUserIdentity(auth.Credentials{
		AccessKey: accessKey,
		SecretKey: cred.SecretKey,
		Status: func() string {
			if status == madmin.AccountEnabled {
				return config.EnableOn
			}
			return config.EnableOff
		}(),
	})

	if err := sys.store.saveUserIdentity(accessKey, regularUser, uinfo); err != nil {
		return err
	}

	sys.iamUsersMap[accessKey] = uinfo.Credentials
	return nil
}

// NewServiceAccount - create a new service account
func (sys *IAMSys) NewServiceAccount(ctx context.Context, parentUser string, sessionPolicy *iampolicy.Policy) (auth.Credentials, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return auth.Credentials{}, errServerNotInitialized
	}

	var policyBuf []byte
	if sessionPolicy != nil {
		err := sessionPolicy.Validate()
		if err != nil {
			return auth.Credentials{}, err
		}
		policyBuf, err = json.Marshal(sessionPolicy)
		if err != nil {
			return auth.Credentials{}, err
		}
		if len(policyBuf) > 16*humanize.KiByte {
			return auth.Credentials{}, fmt.Errorf("Session policy should not exceed 16 KiB characters")
		}
	}

	sys.store.lock()
	defer sys.store.unlock()

	if parentUser == globalActiveCred.AccessKey {
		return auth.Credentials{}, errIAMActionNotAllowed
	}

	cr, ok := sys.iamUsersMap[parentUser]
	if !ok {
		return auth.Credentials{}, errNoSuchUser
	}

	// Disallow service accounts to further create more service accounts.
	if cr.IsServiceAccount() {
		return auth.Credentials{}, errIAMActionNotAllowed
	}

	m := make(map[string]interface{})
	m[parentClaim] = parentUser

	if len(policyBuf) > 0 {
		m[iampolicy.SessionPolicyName] = base64.StdEncoding.EncodeToString(policyBuf)
		m[iamPolicyClaimNameSA()] = "embedded-policy"
	} else {
		m[iamPolicyClaimNameSA()] = "inherited-policy"
	}

	secret := globalActiveCred.SecretKey
	cred, err := auth.GetNewCredentialsWithMetadata(m, secret)
	if err != nil {
		return auth.Credentials{}, err
	}
	cred.ParentUser = parentUser

	u := newUserIdentity(cred)

	if err := sys.store.saveUserIdentity(u.Credentials.AccessKey, srvAccUser, u); err != nil {
		return auth.Credentials{}, err
	}

	sys.iamUsersMap[u.Credentials.AccessKey] = u.Credentials

	return cred, nil
}

// ListServiceAccounts - lists all services accounts associated to a specific user
func (sys *IAMSys) ListServiceAccounts(ctx context.Context, accessKey string) ([]string, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return nil, errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	if sys.storeFallback {
		return nil, errIAMNotInitialized
	}

	var serviceAccounts []string

	for k, v := range sys.iamUsersMap {
		if v.IsServiceAccount() && v.ParentUser == accessKey {
			serviceAccounts = append(serviceAccounts, k)
		}
	}

	return serviceAccounts, nil
}

// GetServiceAccountParent - gets information about a service account
func (sys *IAMSys) GetServiceAccountParent(ctx context.Context, accessKey string) (string, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return "", errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	sa, ok := sys.iamUsersMap[accessKey]
	if ok && sa.IsServiceAccount() {
		return sa.ParentUser, nil
	}
	return "", nil
}

// DeleteServiceAccount - delete a service account
func (sys *IAMSys) DeleteServiceAccount(ctx context.Context, accessKey string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	sa, ok := sys.iamUsersMap[accessKey]
	if !ok || !sa.IsServiceAccount() {
		return nil
	}

	// It is ok to ignore deletion error on the mapped policy
	err := sys.store.deleteUserIdentity(accessKey, srvAccUser)
	if err != nil {
		// ignore if user is already deleted.
		if err == errNoSuchUser {
			return nil
		}
		return err
	}

	delete(sys.iamUsersMap, accessKey)
	return nil
}

// SetUser - set user credentials and policy.
func (sys *IAMSys) SetUser(accessKey string, uinfo madmin.UserInfo) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	u := newUserIdentity(auth.Credentials{
		AccessKey: accessKey,
		SecretKey: uinfo.SecretKey,
		Status:    string(uinfo.Status),
	})

	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	cr, ok := sys.iamUsersMap[accessKey]
	if cr.IsTemp() && ok {
		return errIAMActionNotAllowed
	}

	if err := sys.store.saveUserIdentity(accessKey, regularUser, u); err != nil {
		return err
	}

	sys.iamUsersMap[accessKey] = u.Credentials

	// Set policy if specified.
	if uinfo.PolicyName != "" {
		return sys.policyDBSet(accessKey, uinfo.PolicyName, regularUser, false)
	}
	return nil
}

// SetUserSecretKey - sets user secret key
func (sys *IAMSys) SetUserSecretKey(accessKey string, secretKey string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	cred, ok := sys.iamUsersMap[accessKey]
	if !ok {
		return errNoSuchUser
	}

	cred.SecretKey = secretKey
	u := newUserIdentity(cred)
	if err := sys.store.saveUserIdentity(accessKey, regularUser, u); err != nil {
		return err
	}

	sys.iamUsersMap[accessKey] = cred
	return nil
}

// GetUser - get user credentials
func (sys *IAMSys) GetUser(accessKey string) (cred auth.Credentials, ok bool) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return cred, false
	}

	sys.store.rlock()
	fallback := sys.storeFallback
	sys.store.runlock()
	if fallback {
		sys.store.lock()
		// If user is already found proceed.
		if _, found := sys.iamUsersMap[accessKey]; !found {
			sys.store.loadUser(accessKey, regularUser, sys.iamUsersMap)
			if _, found = sys.iamUsersMap[accessKey]; found {
				// found user, load its mapped policies
				sys.store.loadMappedPolicy(accessKey, regularUser, false, sys.iamUserPolicyMap)
			} else {
				sys.store.loadUser(accessKey, srvAccUser, sys.iamUsersMap)
				if svc, found := sys.iamUsersMap[accessKey]; found {
					// Found service account, load its parent user and its mapped policies.
					if sys.usersSysType == MinIOUsersSysType {
						sys.store.loadUser(svc.ParentUser, regularUser, sys.iamUsersMap)
					}
					sys.store.loadMappedPolicy(svc.ParentUser, regularUser, false, sys.iamUserPolicyMap)
				} else {
					// None found fall back to STS users.
					sys.store.loadUser(accessKey, stsUser, sys.iamUsersMap)
					if _, found = sys.iamUsersMap[accessKey]; found {
						// STS user found, load its mapped policy.
						sys.store.loadMappedPolicy(accessKey, stsUser, false, sys.iamUserPolicyMap)
					}
				}
			}
		}
		// Load associated policies if any.
		for _, policy := range sys.iamUserPolicyMap[accessKey].toSlice() {
			if _, found := sys.iamPolicyDocsMap[policy]; !found {
				sys.store.loadPolicyDoc(policy, sys.iamPolicyDocsMap)
			}
		}
		sys.store.unlock()
	}

	sys.store.rlock()
	defer sys.store.runlock()

	cred, ok = sys.iamUsersMap[accessKey]
	if ok && cred.IsValid() {
		if cred.ParentUser != "" && sys.usersSysType == MinIOUsersSysType {
			_, ok = sys.iamUsersMap[cred.ParentUser]
		}
		// for LDAP service accounts with ParentUser set
		// we have no way to validate, either because user
		// doesn't need an explicit policy as it can come
		// automatically from a group. We are safe to ignore
		// this and continue as policies would fail eventually
		// the policies are missing or not configured.
	}
	return cred, ok && cred.IsValid()
}

// AddUsersToGroup - adds users to a group, creating the group if
// needed. No error if user(s) already are in the group.
func (sys *IAMSys) AddUsersToGroup(group string, members []string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	if group == "" {
		return errInvalidArgument
	}

	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	// Validate that all members exist.
	for _, member := range members {
		cr, ok := sys.iamUsersMap[member]
		if !ok {
			return errNoSuchUser
		}
		if cr.IsTemp() {
			return errIAMActionNotAllowed
		}
	}

	gi, ok := sys.iamGroupsMap[group]
	if !ok {
		// Set group as enabled by default when it doesn't
		// exist.
		gi = newGroupInfo(members)
	} else {
		mergedMembers := append(gi.Members, members...)
		uniqMembers := set.CreateStringSet(mergedMembers...).ToSlice()
		gi.Members = uniqMembers
	}

	if err := sys.store.saveGroupInfo(group, gi); err != nil {
		return err
	}

	sys.iamGroupsMap[group] = gi

	// update user-group membership map
	for _, member := range members {
		gset := sys.iamUserGroupMemberships[member]
		if gset == nil {
			gset = set.CreateStringSet(group)
		} else {
			gset.Add(group)
		}
		sys.iamUserGroupMemberships[member] = gset
	}

	return nil
}

// RemoveUsersFromGroup - remove users from group. If no users are
// given, and the group is empty, deletes the group as well.
func (sys *IAMSys) RemoveUsersFromGroup(group string, members []string) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	if group == "" {
		return errInvalidArgument
	}

	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	// Validate that all members exist.
	for _, member := range members {
		cr, ok := sys.iamUsersMap[member]
		if !ok {
			return errNoSuchUser
		}
		if cr.IsTemp() {
			return errIAMActionNotAllowed
		}
	}

	gi, ok := sys.iamGroupsMap[group]
	if !ok {
		return errNoSuchGroup
	}

	// Check if attempting to delete a non-empty group.
	if len(members) == 0 && len(gi.Members) != 0 {
		return errGroupNotEmpty
	}

	if len(members) == 0 {
		// len(gi.Members) == 0 here.

		// Remove the group from storage. First delete the
		// mapped policy. No-mapped-policy case is ignored.
		if err := sys.store.deleteMappedPolicy(group, regularUser, true); err != nil && err != errNoSuchPolicy {
			return err
		}
		if err := sys.store.deleteGroupInfo(group); err != nil && err != errNoSuchGroup {
			return err
		}

		// Delete from server memory
		delete(sys.iamGroupsMap, group)
		delete(sys.iamGroupPolicyMap, group)
		return nil
	}

	// Only removing members.
	s := set.CreateStringSet(gi.Members...)
	d := set.CreateStringSet(members...)
	gi.Members = s.Difference(d).ToSlice()

	err := sys.store.saveGroupInfo(group, gi)
	if err != nil {
		return err
	}
	sys.iamGroupsMap[group] = gi

	// update user-group membership map
	for _, member := range members {
		gset := sys.iamUserGroupMemberships[member]
		if gset == nil {
			continue
		}
		gset.Remove(group)
		sys.iamUserGroupMemberships[member] = gset
	}

	return nil
}

// SetGroupStatus - enable/disabled a group
func (sys *IAMSys) SetGroupStatus(group string, enabled bool) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	if sys.usersSysType != MinIOUsersSysType {
		return errIAMActionNotAllowed
	}

	if group == "" {
		return errInvalidArgument
	}

	gi, ok := sys.iamGroupsMap[group]
	if !ok {
		return errNoSuchGroup
	}

	if enabled {
		gi.Status = statusEnabled
	} else {
		gi.Status = statusDisabled
	}

	if err := sys.store.saveGroupInfo(group, gi); err != nil {
		return err
	}
	sys.iamGroupsMap[group] = gi
	return nil
}

// GetGroupDescription - builds up group description
func (sys *IAMSys) GetGroupDescription(group string) (gd madmin.GroupDesc, err error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return gd, errServerNotInitialized
	}

	ps, err := sys.PolicyDBGet(group, true)
	if err != nil {
		return gd, err
	}

	// A group may be mapped to at most one policy.
	policy := ""
	if len(ps) > 0 {
		policy = ps[0]
	}

	if sys.usersSysType != MinIOUsersSysType {
		return madmin.GroupDesc{
			Name:   group,
			Policy: policy,
		}, nil
	}

	sys.store.rlock()
	defer sys.store.runlock()

	gi, ok := sys.iamGroupsMap[group]
	if !ok {
		return gd, errNoSuchGroup
	}

	return madmin.GroupDesc{
		Name:    group,
		Status:  gi.Status,
		Members: gi.Members,
		Policy:  policy,
	}, nil
}

// ListGroups - lists groups.
func (sys *IAMSys) ListGroups() (r []string, err error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return r, errServerNotInitialized
	}

	sys.store.rlock()
	defer sys.store.runlock()

	if sys.storeFallback {
		return nil, errIAMNotInitialized
	}

	if sys.usersSysType != MinIOUsersSysType {
		return nil, errIAMActionNotAllowed
	}

	for k := range sys.iamGroupsMap {
		r = append(r, k)
	}
	return r, nil
}

// PolicyDBSet - sets a policy for a user or group in the PolicyDB.
func (sys *IAMSys) PolicyDBSet(name, policy string, isGroup bool) error {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return errServerNotInitialized
	}

	sys.store.lock()
	defer sys.store.unlock()

	return sys.policyDBSet(name, policy, regularUser, isGroup)
}

// policyDBSet - sets a policy for user in the policy db. Assumes that caller
// has sys.Lock(). If policy == "", then policy mapping is removed.
func (sys *IAMSys) policyDBSet(name, policyName string, userType IAMUserType, isGroup bool) error {
	if name == "" {
		return errInvalidArgument
	}

	if sys.usersSysType == MinIOUsersSysType {
		if !isGroup {
			if _, ok := sys.iamUsersMap[name]; !ok {
				return errNoSuchUser
			}
		} else {
			if _, ok := sys.iamGroupsMap[name]; !ok {
				return errNoSuchGroup
			}
		}
	}

	// Handle policy mapping removal
	if policyName == "" {
		if err := sys.store.deleteMappedPolicy(name, userType, isGroup); err != nil && err != errNoSuchPolicy {
			return err
		}
		if !isGroup {
			delete(sys.iamUserPolicyMap, name)
		} else {
			delete(sys.iamGroupPolicyMap, name)
		}
		return nil
	}

	mp := newMappedPolicy(policyName)
	for _, policy := range mp.toSlice() {
		if _, found := sys.iamPolicyDocsMap[policy]; !found {
			logger.LogIf(GlobalContext, fmt.Errorf("%w: (%s)", errNoSuchPolicy, policy))
			return errNoSuchPolicy
		}
	}

	// Handle policy mapping set/update
	if err := sys.store.saveMappedPolicy(name, userType, isGroup, mp); err != nil {
		return err
	}
	if !isGroup {
		sys.iamUserPolicyMap[name] = mp
	} else {
		sys.iamGroupPolicyMap[name] = mp
	}
	return nil
}

// PolicyDBGet - gets policy set on a user or group. Since a user may
// be a member of multiple groups, this function returns an array of
// applicable policies (each group is mapped to at most one policy).
func (sys *IAMSys) PolicyDBGet(name string, isGroup bool) ([]string, error) {
	objectAPI := newObjectLayerWithoutSafeModeFn()
	if objectAPI == nil || sys == nil || sys.store == nil {
		return nil, errServerNotInitialized
	}

	if name == "" {
		return nil, errInvalidArgument
	}

	sys.store.rlock()
	defer sys.store.runlock()

	return sys.policyDBGet(name, isGroup)
}

// This call assumes that caller has the sys.RLock()
func (sys *IAMSys) policyDBGet(name string, isGroup bool) ([]string, error) {
	if isGroup {
		if _, ok := sys.iamGroupsMap[name]; !ok {
			return nil, errNoSuchGroup
		}

		mp := sys.iamGroupPolicyMap[name]
		return mp.toSlice(), nil
	}

	// When looking for a user's policies, we also check if the
	// user and the groups they are member of are enabled.
	if u, ok := sys.iamUsersMap[name]; !ok {
		return nil, errNoSuchUser
	} else if u.Status == statusDisabled {
		// User is disabled, so we return no policy - this
		// ensures the request is denied.
		return nil, nil
	}

	var policies []string

	mp := sys.iamUserPolicyMap[name]
	// returned policy could be empty
	policies = append(policies, mp.toSlice()...)

	for _, group := range sys.iamUserGroupMemberships[name].ToSlice() {
		// Skip missing or disabled groups
		gi, ok := sys.iamGroupsMap[group]
		if !ok || gi.Status == statusDisabled {
			continue
		}

		p := sys.iamGroupPolicyMap[group]
		policies = append(policies, p.toSlice()...)
	}
	return policies, nil
}

// IsAllowedServiceAccount - checks if the given service account is allowed to perform
// actions. The permission of the parent user is checked first
func (sys *IAMSys) IsAllowedServiceAccount(args iampolicy.Args, parent string) bool {
	// Now check if we have a subject claim
	p, ok := args.Claims[parentClaim]
	if ok {
		parentInClaim, ok := p.(string)
		if !ok {
			// Reject malformed/malicious requests.
			return false
		}
		// The parent claim in the session token should be equal
		// to the parent detected in the backend
		if parentInClaim != parent {
			return false
		}
	} else {
		// This is needed so a malicious user cannot
		// use a leaked session key of another user
		// to widen its privileges.
		return false
	}

	// Check if the parent is allowed to perform this action, reject if not
	parentUserPolicies, err := sys.PolicyDBGet(parent, false)
	if err != nil {
		return false
	}

	if len(parentUserPolicies) == 0 {
		return false
	}

	var availablePolicies []iampolicy.Policy

	// Policies were found, evaluate all of them.
	sys.store.rlock()
	for _, pname := range parentUserPolicies {
		p, found := sys.iamPolicyDocsMap[pname]
		if found {
			availablePolicies = append(availablePolicies, p)
		}
	}
	sys.store.runlock()

	if len(availablePolicies) == 0 {
		return false
	}

	combinedPolicy := availablePolicies[0]
	for i := 1; i < len(availablePolicies); i++ {
		combinedPolicy.Statements = append(combinedPolicy.Statements,
			availablePolicies[i].Statements...)
	}

	parentArgs := args
	parentArgs.AccountName = parent

	saPolicyClaim, ok := args.Claims[iamPolicyClaimNameSA()]
	if !ok {
		return false
	}

	saPolicyClaimStr, ok := saPolicyClaim.(string)
	if !ok {
		// Sub policy if set, should be a string reject
		// malformed/malicious requests.
		return false
	}

	if saPolicyClaimStr == "inherited-policy" {
		return combinedPolicy.IsAllowed(parentArgs)
	}

	// Now check if we have a sessionPolicy.
	spolicy, ok := args.Claims[iampolicy.SessionPolicyName]
	if !ok {
		return false
	}

	spolicyStr, ok := spolicy.(string)
	if !ok {
		// Sub policy if set, should be a string reject
		// malformed/malicious requests.
		return false
	}

	// Check if policy is parseable.
	subPolicy, err := iampolicy.ParseConfig(bytes.NewReader([]byte(spolicyStr)))
	if err != nil {
		// Log any error in input session policy config.
		logger.LogIf(GlobalContext, err)
		return false
	}

	// Policy without Version string value reject it.
	if subPolicy.Version == "" {
		return false
	}

	return combinedPolicy.IsAllowed(parentArgs) && subPolicy.IsAllowed(parentArgs)
}

// IsAllowedLDAPSTS - checks for LDAP specific claims and values
func (sys *IAMSys) IsAllowedLDAPSTS(args iampolicy.Args) bool {
	userIface, ok := args.Claims[ldapUser]
	if !ok {
		return false
	}
	user, ok := userIface.(string)
	if !ok {
		return false
	}

	sys.store.rlock()
	defer sys.store.runlock()

	var groups []string
	cred, ok := sys.iamUsersMap[args.AccountName]
	if !ok {
		return false
	}
	groups = cred.Groups

	// We look up the policy mapping directly to bypass
	// users exists, group exists validations that do not
	// apply here.
	var policies []iampolicy.Policy
	if mp, ok := sys.iamUserPolicyMap[user]; ok {
		for _, pname := range mp.toSlice() {
			p, found := sys.iamPolicyDocsMap[pname]
			if !found {
				logger.LogIf(GlobalContext, fmt.Errorf("expected policy (%s) missing for the LDAPUser %s, rejecting the request", pname, user))
				return false
			}
			policies = append(policies, p)
		}
	}
	for _, group := range groups {
		mp, ok := sys.iamGroupPolicyMap[group]
		if !ok {
			continue
		}
		for _, pname := range mp.toSlice() {
			p, found := sys.iamPolicyDocsMap[pname]
			if !found {
				logger.LogIf(GlobalContext, fmt.Errorf("expected policy (%s) missing for the LDAPGroup %s, rejecting the request", pname, group))
				return false
			}
			policies = append(policies, p)
		}
	}
	if len(policies) == 0 {
		return false
	}
	combinedPolicy := policies[0]
	for i := 1; i < len(policies); i++ {
		combinedPolicy.Statements =
			append(combinedPolicy.Statements,
				policies[i].Statements...)
	}
	return combinedPolicy.IsAllowed(args)
}

// IsAllowedSTS is meant for STS based temporary credentials,
// which implements claims validation and verification other than
// applying policies.
func (sys *IAMSys) IsAllowedSTS(args iampolicy.Args) bool {
	// If it is an LDAP request, check that user and group
	// policies allow the request.
	if sys.usersSysType == LDAPUsersSysType {
		return sys.IsAllowedLDAPSTS(args)
	}

	policies, ok := args.GetPolicies(iamPolicyClaimNameOpenID())
	if !ok {
		// When claims are set, it should have a policy claim field.
		return false
	}

	// When claims are set, it should have policies as claim.
	if policies.IsEmpty() {
		// No policy, no access!
		return false
	}

	sys.store.rlock()
	defer sys.store.runlock()

	// If policy is available for given user, check the policy.
	mp, ok := sys.iamUserPolicyMap[args.AccountName]
	if !ok {
		// No policy set for the user that we can find, no access!
		return false
	}

	if !policies.Equals(mp.policySet()) {
		// When claims has a policy, it should match the
		// policy of args.AccountName which server remembers.
		// if not reject such requests.
		return false
	}

	var availablePolicies []iampolicy.Policy
	for pname := range policies {
		p, found := sys.iamPolicyDocsMap[pname]
		if !found {
			// all policies presented in the claim should exist
			logger.LogIf(GlobalContext, fmt.Errorf("expected policy (%s) missing from the JWT claim %s, rejecting the request", pname, iamPolicyClaimNameOpenID()))
			return false
		}
		availablePolicies = append(availablePolicies, p)
	}

	combinedPolicy := availablePolicies[0]
	for i := 1; i < len(availablePolicies); i++ {
		combinedPolicy.Statements = append(combinedPolicy.Statements,
			availablePolicies[i].Statements...)
	}

	// Now check if we have a sessionPolicy.
	spolicy, ok := args.Claims[iampolicy.SessionPolicyName]
	if ok {
		spolicyStr, ok := spolicy.(string)
		if !ok {
			// Sub policy if set, should be a string reject
			// malformed/malicious requests.
			return false
		}

		// Check if policy is parseable.
		subPolicy, err := iampolicy.ParseConfig(bytes.NewReader([]byte(spolicyStr)))
		if err != nil {
			// Log any error in input session policy config.
			logger.LogIf(GlobalContext, err)
			return false
		}

		// Policy without Version string value reject it.
		if subPolicy.Version == "" {
			return false
		}

		// Sub policy is set and valid.
		return combinedPolicy.IsAllowed(args) && subPolicy.IsAllowed(args)
	}

	// Sub policy not set, this is most common since subPolicy
	// is optional, use the inherited policies.
	return combinedPolicy.IsAllowed(args)
}

// IsAllowed - checks given policy args is allowed to continue the Rest API.
func (sys *IAMSys) IsAllowed(args iampolicy.Args) bool {
	// If opa is configured, use OPA always.
	if globalPolicyOPA != nil {
		ok, err := globalPolicyOPA.IsAllowed(args)
		if err != nil {
			logger.LogIf(GlobalContext, err)
		}
		return ok
	}

	// Policies don't apply to the owner.
	if args.IsOwner {
		return true
	}

	// If the credential is temporary, perform STS related checks.
	ok, err := sys.IsTempUser(args.AccountName)
	if err != nil {
		return false
	}
	if ok {
		return sys.IsAllowedSTS(args)
	}

	// If the credential is for a service account, perform related check
	ok, parentUser, err := sys.IsServiceAccount(args.AccountName)
	if err != nil {
		return false
	}
	if ok {
		return sys.IsAllowedServiceAccount(args, parentUser)
	}

	// Continue with the assumption of a regular user
	policies, err := sys.PolicyDBGet(args.AccountName, false)
	if err != nil {
		return false
	}

	if len(policies) == 0 {
		// No policy found.
		return false
	}

	// Policies were found, evaluate all of them.
	sys.store.rlock()
	defer sys.store.runlock()

	var availablePolicies []iampolicy.Policy
	for _, pname := range policies {
		p, found := sys.iamPolicyDocsMap[pname]
		if found {
			availablePolicies = append(availablePolicies, p)
		}
	}
	if len(availablePolicies) == 0 {
		return false
	}
	combinedPolicy := availablePolicies[0]
	for i := 1; i < len(availablePolicies); i++ {
		combinedPolicy.Statements = append(combinedPolicy.Statements,
			availablePolicies[i].Statements...)
	}
	return combinedPolicy.IsAllowed(args)
}

// Set default canned policies only if not already overridden by users.
func setDefaultCannedPolicies(policies map[string]iampolicy.Policy) {
	_, ok := policies["writeonly"]
	if !ok {
		policies["writeonly"] = iampolicy.WriteOnly
	}
	_, ok = policies["readonly"]
	if !ok {
		policies["readonly"] = iampolicy.ReadOnly
	}
	_, ok = policies["readwrite"]
	if !ok {
		policies["readwrite"] = iampolicy.ReadWrite
	}
	_, ok = policies["diagnostics"]
	if !ok {
		policies["diagnostics"] = iampolicy.AdminDiagnostics
	}
}

// buildUserGroupMemberships - builds the memberships map. IMPORTANT:
// Assumes that sys.Lock is held by caller.
func (sys *IAMSys) buildUserGroupMemberships() {
	for group, gi := range sys.iamGroupsMap {
		sys.updateGroupMembershipsMap(group, &gi)
	}
}

// updateGroupMembershipsMap - updates the memberships map for a
// group. IMPORTANT: Assumes sys.Lock() is held by caller.
func (sys *IAMSys) updateGroupMembershipsMap(group string, gi *GroupInfo) {
	if gi == nil {
		return
	}
	for _, member := range gi.Members {
		v := sys.iamUserGroupMemberships[member]
		if v == nil {
			v = set.CreateStringSet(group)
		} else {
			v.Add(group)
		}
		sys.iamUserGroupMemberships[member] = v
	}
}

// removeGroupFromMembershipsMap - removes the group from every member
// in the cache. IMPORTANT: Assumes sys.Lock() is held by caller.
func (sys *IAMSys) removeGroupFromMembershipsMap(group string) {
	for member, groups := range sys.iamUserGroupMemberships {
		if !groups.Contains(group) {
			continue
		}
		groups.Remove(group)
		sys.iamUserGroupMemberships[member] = groups
	}
}

// EnableLDAPSys - enable ldap system users type.
func (sys *IAMSys) EnableLDAPSys() {
	sys.store.lock()
	defer sys.store.unlock()

	sys.usersSysType = LDAPUsersSysType
}

// NewIAMSys - creates new config system object.
func NewIAMSys() *IAMSys {
	return &IAMSys{
		usersSysType:            MinIOUsersSysType,
		iamUsersMap:             make(map[string]auth.Credentials),
		iamPolicyDocsMap:        make(map[string]iampolicy.Policy),
		iamUserPolicyMap:        make(map[string]MappedPolicy),
		iamGroupPolicyMap:       make(map[string]MappedPolicy),
		iamGroupsMap:            make(map[string]GroupInfo),
		iamUserGroupMemberships: make(map[string]set.StringSet),
		storeFallback:           true,
	}
}