forked from gravitational/teleport
/
usermgmt.go
496 lines (445 loc) · 15 KB
/
usermgmt.go
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/*
* Teleport
* Copyright (C) 2023 Gravitational, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package srv
import (
"context"
"errors"
"fmt"
"io"
"os/user"
"regexp"
"strings"
"syscall"
"time"
"github.com/gravitational/trace"
log "github.com/sirupsen/logrus"
"github.com/gravitational/teleport/api/types"
"github.com/gravitational/teleport/api/utils/retryutils"
"github.com/gravitational/teleport/lib/services"
"github.com/gravitational/teleport/lib/services/local"
)
// NewHostUsers initialize a new HostUsers object
func NewHostUsers(ctx context.Context, storage *local.PresenceService, uuid string) HostUsers {
backend, err := newHostUsersBackend()
switch {
case trace.IsNotImplemented(err):
log.Debugf("Skipping host user management: %v", err)
return nil
case err != nil: //nolint:staticcheck // linter fails on non-linux system as only linux implementation returns useful values.
log.Warnf("Error making new HostUsersBackend: %s", err)
return nil
}
cancelCtx, cancelFunc := context.WithCancel(ctx)
return &HostUserManagement{
backend: backend,
ctx: cancelCtx,
cancel: cancelFunc,
storage: storage,
userGrace: time.Second * 30,
}
}
func NewHostSudoers(uuid string) HostSudoers {
backend, err := newHostSudoersBackend(uuid)
switch {
case trace.IsNotImplemented(err):
log.Debugf("Skipping host sudoers management: %v", err)
return nil
case err != nil: //nolint:staticcheck // linter fails on non-linux system as only linux implementation returns useful values.
log.Warnf("Error making new HostSudoersBackend: %s", err)
return nil
}
return &HostSudoersManagement{
backend: backend,
}
}
type HostSudoersBackend interface {
// CheckSudoers ensures that a sudoers file to be written is valid
CheckSudoers(contents []byte) error
// WriteSudoersFile creates the user's sudoers file.
WriteSudoersFile(user string, entries []byte) error
// RemoveSudoersFile deletes a user's sudoers file.
RemoveSudoersFile(user string) error
}
type HostUsersBackend interface {
// GetAllUsers returns all host users on a node.
GetAllUsers() ([]string, error)
// UserGIDs returns a list of group ids for a user.
UserGIDs(*user.User) ([]string, error)
// Lookup retrieves a user by name.
Lookup(name string) (*user.User, error)
// LookupGroup retrieves a group by name.
LookupGroup(group string) (*user.Group, error)
// LookupGroupByID retrieves a group by its ID.
LookupGroupByID(gid string) (*user.Group, error)
// CreateGroup creates a group on a host.
CreateGroup(group string, gid string) error
// CreateUser creates a user on a host.
CreateUser(name string, groups []string, uid, gid string) error
// DeleteUser deletes a user from a host.
DeleteUser(name string) error
// CreateHomeDirectory creates the users home directory and copies in /etc/skel
CreateHomeDirectory(user string, uid, gid string) error
}
type userCloser struct {
users HostUsers
backend HostUsersBackend
username string
}
func (u *userCloser) Close() error {
teleportGroup, err := u.backend.LookupGroup(types.TeleportServiceGroup)
if err != nil {
return trace.Wrap(err)
}
err = u.users.doWithUserLock(func(sl types.SemaphoreLease) error {
return trace.Wrap(u.users.DeleteUser(u.username, teleportGroup.Gid))
})
return trace.Wrap(err)
}
var ErrUserLoggedIn = errors.New("User logged in error")
type HostSudoers interface {
// WriteSudoers creates a temporary Teleport user in the TeleportServiceGroup
WriteSudoers(name string, sudoers []string) error
// RemoveSudoers removes the users sudoer file
RemoveSudoers(name string) error
}
type HostSudoersNotImplemented struct{}
// WriteSudoers creates a temporary Teleport user in the TeleportServiceGroup
func (*HostSudoersNotImplemented) WriteSudoers(string, []string) error {
return trace.NotImplemented("host sudoers functionality not implemented on this platform")
}
// RemoveSudoers removes the users sudoer file
func (*HostSudoersNotImplemented) RemoveSudoers(name string) error {
return trace.NotImplemented("host sudoers functionality not implemented on this platform")
}
type HostUsers interface {
// CreateUser creates a temporary Teleport user in the TeleportServiceGroup
CreateUser(name string, hostRoleInfo *services.HostUsersInfo) (io.Closer, error)
// DeleteUser deletes a temporary Teleport user only if they are
// in a specified group
DeleteUser(name string, gid string) error
// DeleteAllUsers deletes all suer in the TeleportServiceGroup
DeleteAllUsers() error
// UserCleanup starts a periodic user deletion cleanup loop for
// users that failed to delete
UserCleanup()
// Shutdown cancels the UserCleanup loop
Shutdown()
// UserExists returns nil should a hostuser exist
UserExists(string) error
// doWithUserLock runs the passed function with a host user
// interaction lock
doWithUserLock(func(types.SemaphoreLease) error) error
// SetHostUserDeletionGrace sets the grace period before a user
// can be deleted, used so integration tests don't need to sleep
SetHostUserDeletionGrace(time.Duration)
}
type HostUserManagement struct {
backend HostUsersBackend
ctx context.Context
cancel context.CancelFunc
storage *local.PresenceService
userGrace time.Duration
}
type HostSudoersManagement struct {
backend HostSudoersBackend
}
var (
_ HostUsers = &HostUserManagement{}
_ HostSudoers = &HostSudoersManagement{}
)
// Under the section "Including other files from within sudoers":
//
// https://man7.org/linux/man-pages/man5/sudoers.5.html
//
// '.', '~' and '/' will cause a file not to be read and these can be
// included in a username, removing slash to avoid escaping a
// directory
var sudoersSanitizationMatcher = regexp.MustCompile(`[\.~\/]`)
// sanitizeSudoersName replaces occurrences of '.', '~' and '/' with
// underscores as `sudo` will not read files including these
// characters
func sanitizeSudoersName(username string) string {
return sudoersSanitizationMatcher.ReplaceAllString(username, "_")
}
// WriteSudoers creates a sudoers file for a user from a list of entries
func (u *HostSudoersManagement) WriteSudoers(name string, sudoers []string) error {
var sudoersOut strings.Builder
for _, entry := range sudoers {
sudoersOut.WriteString(fmt.Sprintf("%s %s\n", name, entry))
}
err := u.backend.WriteSudoersFile(name, []byte(sudoersOut.String()))
return trace.Wrap(err)
}
func (u *HostSudoersManagement) RemoveSudoers(name string) error {
if err := u.backend.RemoveSudoersFile(name); err != nil {
return trace.Wrap(err)
}
return nil
}
// CreateUser creates a temporary Teleport user in the TeleportServiceGroup
func (u *HostUserManagement) CreateUser(name string, ui *services.HostUsersInfo) (io.Closer, error) {
if ui.Mode == types.CreateHostUserMode_HOST_USER_MODE_UNSPECIFIED {
return nil, trace.BadParameter("Mode is a required argument to CreateUser")
}
tempUser, err := u.backend.Lookup(name)
if err != nil && !errors.Is(err, user.UnknownUserError(name)) {
return nil, trace.Wrap(err)
}
if tempUser != nil {
gids, err := u.backend.UserGIDs(tempUser)
if err != nil {
return nil, trace.Wrap(err)
}
systemGroup, err := u.backend.LookupGroup(types.TeleportServiceGroup)
if err != nil {
if isUnknownGroupError(err, types.TeleportServiceGroup) {
return nil, trace.AlreadyExists("User %q already exists, however no users are currently managed by teleport", name)
}
return nil, trace.Wrap(err)
}
var found bool
for _, gid := range gids {
if gid == systemGroup.Gid {
found = true
break
}
}
if !found {
return nil, trace.AlreadyExists("User %q already exists and is not managed by teleport", name)
}
err = u.doWithUserLock(func(_ types.SemaphoreLease) error {
if err := u.storage.UpsertHostUserInteractionTime(u.ctx, name, time.Now()); err != nil {
return trace.Wrap(err)
}
return nil
})
if err != nil {
return nil, trace.Wrap(err)
}
// try to delete even if the user already exists as only users
// in the teleport-system group will be deleted and this way
// if a user creates multiple sessions the account will
// succeed in deletion
return &userCloser{
username: name,
users: u,
backend: u.backend,
}, trace.AlreadyExists("User %q already exists", name)
}
groups := make([]string, 0, len(ui.Groups))
for _, group := range ui.Groups {
if group == name {
// this causes an error as useradd expects the group with the same name as the user to be available
log.Debugf("Skipping group creation with name the same as login user (%q, %q).", name, group)
continue
}
groups = append(groups, group)
}
if ui.Mode == types.CreateHostUserMode_HOST_USER_MODE_INSECURE_DROP {
groups = append(groups, types.TeleportServiceGroup)
}
var errs []error
for _, group := range groups {
if err := u.createGroupIfNotExist(group); err != nil {
errs = append(errs, err)
continue
}
}
if err := trace.NewAggregate(errs...); err != nil {
return nil, trace.WrapWithMessage(err, "error while creating groups")
}
err = u.doWithUserLock(func(_ types.SemaphoreLease) error {
if err := u.storage.UpsertHostUserInteractionTime(u.ctx, name, time.Now()); err != nil {
return trace.Wrap(err)
}
if ui.GID != "" {
// if gid is specified a group must already exist
err := u.backend.CreateGroup(name, ui.GID)
if err != nil && !trace.IsAlreadyExists(err) {
return trace.Wrap(err)
}
}
err = u.backend.CreateUser(name, groups, ui.UID, ui.GID)
if err != nil && !trace.IsAlreadyExists(err) {
return trace.WrapWithMessage(err, "error while creating user")
}
user, err := u.backend.Lookup(name)
if err != nil {
return trace.Wrap(err)
}
if ui.Mode != types.CreateHostUserMode_HOST_USER_MODE_INSECURE_DROP {
if err := u.backend.CreateHomeDirectory(name, user.Uid, user.Gid); err != nil {
return trace.Wrap(err)
}
}
return nil
})
if err != nil {
return nil, trace.Wrap(err)
}
if ui.Mode == types.CreateHostUserMode_HOST_USER_MODE_KEEP {
return nil, trace.Wrap(err)
}
closer := &userCloser{
username: name,
users: u,
backend: u.backend,
}
return closer, trace.Wrap(err)
}
func (u *HostUserManagement) doWithUserLock(f func(types.SemaphoreLease) error) error {
lock, err := services.AcquireSemaphoreWithRetry(u.ctx,
services.AcquireSemaphoreWithRetryConfig{
Service: u.storage,
Request: types.AcquireSemaphoreRequest{
SemaphoreKind: types.SemaphoreKindHostUserModification,
SemaphoreName: "host_user_modification",
MaxLeases: 1,
Expires: time.Now().Add(time.Second * 20),
},
Retry: retryutils.LinearConfig{
Step: time.Second * 5,
Max: time.Minute,
},
})
if err != nil {
return trace.Wrap(err)
}
defer u.storage.CancelSemaphoreLease(u.ctx, *lock)
return trace.Wrap(f(*lock))
}
func (u *HostUserManagement) createGroupIfNotExist(group string) error {
_, err := u.backend.LookupGroup(group)
if err != nil && !isUnknownGroupError(err, group) {
return trace.Wrap(err)
}
err = u.backend.CreateGroup(group, "")
if trace.IsAlreadyExists(err) {
return nil
}
return trace.Wrap(err)
}
// isUnknownGroupError returns whether the error from LookupGroup is an unknown group error.
//
// LookupGroup is supposed to return an UnknownGroupError, but due to an existing issue
// may instead return a generic "no such file or directory" error when sssd is installed
// or "no such process" as Go std library just forwards errors returned by getgrpnam_r.
// See github issue - https://github.com/golang/go/issues/40334
func isUnknownGroupError(err error, groupName string) bool {
return errors.Is(err, user.UnknownGroupError(groupName)) ||
errors.Is(err, user.UnknownGroupIdError(groupName)) ||
strings.HasSuffix(err.Error(), syscall.ENOENT.Error()) ||
strings.HasSuffix(err.Error(), syscall.ESRCH.Error())
}
// DeleteAllUsers deletes all host users in the teleport service group.
func (u *HostUserManagement) DeleteAllUsers() error {
users, err := u.backend.GetAllUsers()
if err != nil {
return trace.Wrap(err)
}
teleportGroup, err := u.backend.LookupGroup(types.TeleportServiceGroup)
if err != nil {
if isUnknownGroupError(err, types.TeleportServiceGroup) {
log.Debugf("%q group not found, not deleting users", types.TeleportServiceGroup)
return nil
}
return trace.Wrap(err)
}
var errs []error
for _, name := range users {
lt, err := u.storage.GetHostUserInteractionTime(u.ctx, name)
if err != nil {
log.Debugf("Failed to find user %q login time: %s", name, err)
continue
}
u.doWithUserLock(func(l types.SemaphoreLease) error {
if time.Since(lt) < u.userGrace {
// small grace period in order to avoid deleting users
// in-between them starting their SSH session and
// entering the shell
return nil
}
errs = append(errs, u.DeleteUser(name, teleportGroup.Gid))
l.Expires = time.Now().Add(time.Second * 10)
u.storage.KeepAliveSemaphoreLease(u.ctx, l)
return nil
})
}
return trace.NewAggregate(errs...)
}
// DeleteUser deletes the specified user only if they are
// present in the specified group.
func (u *HostUserManagement) DeleteUser(username string, gid string) error {
tempUser, err := u.backend.Lookup(username)
if err != nil {
return trace.Wrap(err)
}
ids, err := u.backend.UserGIDs(tempUser)
if err != nil {
return trace.Wrap(err)
}
for _, id := range ids {
if id == gid {
err := u.backend.DeleteUser(username)
if err != nil {
if errors.Is(err, ErrUserLoggedIn) {
log.Debugf("Not deleting user %q, user has another session, or running process", username)
return nil
}
return trace.Wrap(err)
}
return nil
}
}
log.Debugf("User %q not deleted: not a temporary user", username)
return nil
}
// UserCleanup starts a periodic user deletion cleanup loop for
// users that failed to delete
func (u *HostUserManagement) UserCleanup() {
cleanupTicker := time.NewTicker(time.Minute * 5)
defer cleanupTicker.Stop()
for {
if err := u.DeleteAllUsers(); err != nil {
log.Error("Error during temporary user cleanup: ", err)
}
select {
case <-cleanupTicker.C:
case <-u.ctx.Done():
return
}
}
}
// Shutdown cancels the UserCleanup loop
func (u *HostUserManagement) Shutdown() {
u.cancel()
}
// UserExists looks up an existing host user.
func (u *HostUserManagement) UserExists(username string) error {
_, err := u.backend.Lookup(username)
if err != nil {
if errors.Is(err, user.UnknownUserError(username)) {
return trace.NotFound("User not found: %s", err)
}
return trace.Wrap(err)
}
return nil
}
func (u *HostUserManagement) SetHostUserDeletionGrace(d time.Duration) {
u.userGrace = d
}