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client_darwin.go
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client_darwin.go
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// Teleport
// Copyright (C) 2024 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/>.
//go:build vnetdaemon
// +build vnetdaemon
package daemon
// #include <stdlib.h>
// #include "client_darwin.h"
// #include "common_darwin.h"
import "C"
import (
"context"
"errors"
"fmt"
"os"
"path/filepath"
"strconv"
"strings"
"time"
"unsafe"
"github.com/gravitational/trace"
"github.com/gravitational/teleport"
"github.com/gravitational/teleport/lib/utils"
logutils "github.com/gravitational/teleport/lib/utils/log"
)
var log = logutils.NewPackageLogger(teleport.ComponentKey, "vnet:daemon")
// RegisterAndCall attempts to register the daemon as a login item, waits for the user to enable it
// and then starts it by sending a message through XPC.
func RegisterAndCall(ctx context.Context, config Config) error {
bundlePath, err := bundlePath()
if err != nil {
return trace.Wrap(err)
}
log.DebugContext(ctx, "Registering (if needed) and calling daemon", "bundle_path", bundlePath)
initialStatus := daemonStatus(bundlePath)
// If the status is equal to "requires approval" before RegisterAndCall called register, it means
// that it's not the first time the user tries to start the daemon. In that case, macOS is not
// going to show the notification about a new login item. Instead, we just open the login items
// ourselves to direct the user towards enabling the login item.
if initialStatus == ServiceStatusRequiresApproval {
C.OpenSystemSettingsLoginItems()
}
if initialStatus != ServiceStatusEnabled {
status, err := register(ctx, bundlePath)
if err != nil {
return trace.Wrap(err)
}
// Once registered for the first time, the status is likely going to be serviceStatusRequiresApproval.
if status != ServiceStatusEnabled {
fmt.Println("To start VNet, please enable the background item for tsh.app in the Login Items section of System Settings.\nWaiting for the background item to be enabled…")
if err := waitForEnablement(ctx, bundlePath); err != nil {
return trace.Wrap(err, "waiting for the login item to get enabled")
}
}
}
if err = startByCalling(ctx, bundlePath, config); err != nil {
if !errors.Is(err, errAlreadyRunning) {
return trace.Wrap(err)
}
// If the daemon was already running, it might mean two things:
//
// 1. The user attempted to start a second instance of VNet.
// 2. The user has stopped the previous instance of VNet and immediately started a new one,
// before the daemon had a chance to notice that the previous instance was stopped and exit too.
//
// In the second case, we want to wait and repeat the call to the daemon, in case the daemon was
// just about to quit.
log.DebugContext(ctx, "VNet daemon is already running, waiting to see if it's going to shut down")
if err := sleepOrDone(ctx, 2*CheckUnprivilegedProcessInterval); err != nil {
return trace.Wrap(err)
}
if err := startByCalling(ctx, bundlePath, config); err != nil {
return trace.Wrap(err)
}
}
// TODO(ravicious): Implement monitoring the state of the daemon.
// Meanwhile, simply block until ctx is canceled.
<-ctx.Done()
return trace.Wrap(ctx.Err())
}
func register(ctx context.Context, bundlePath string) (ServiceStatus, error) {
cBundlePath := C.CString(bundlePath)
defer C.free(unsafe.Pointer(cBundlePath))
var result C.RegisterDaemonResult
defer func() {
C.free(unsafe.Pointer(result.error_description))
}()
C.RegisterDaemon(cBundlePath, &result)
if !result.ok {
status := ServiceStatus(result.service_status)
// Docs for [registerAndReturnError][1] don't seem to cover a situation in which the user adds
// the launch daemon for the first time. In that case, that method returns "Operation not
// permitted" error (Code=1, Domain=SMAppServiceErrorDomain). That error doesn't seem to exist
// in [Service Management Errors][2]. However, all this means is that the launch daemon was
// added to the login items and the user must now enable the corresponding login item.
//
// We can confirm this by looking at the returned service status.
//
// [1]: https://developer.apple.com/documentation/servicemanagement/smappservice/register()?language=objc
// [2]: https://developer.apple.com/documentation/servicemanagement/service-management-errors?language=objc
if status == ServiceStatusRequiresApproval {
log.DebugContext(ctx, "Daemon successfully added, but it requires approval",
"ignored_error", C.GoString(result.error_description))
return status, nil
}
log.DebugContext(ctx, "Registering the daemon has failed", "service_status", status)
return -1, trace.Errorf("registering daemon failed, %s", C.GoString(result.error_description))
}
return ServiceStatus(result.service_status), nil
}
// waitForEnablement periodically checks if the status of the daemon has changed to
// [serviceStatusEnabled]. This happens when the user approves the login item in system settings.
func waitForEnablement(ctx context.Context, bundlePath string) error {
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
// It should be less than receiveTunTimeout in the vnet package
// so that the user sees the error about the background item first.
const waitingForEnablementTimeout = 50 * time.Second
ctx, cancel := context.WithTimeoutCause(ctx, waitingForEnablementTimeout,
errors.New("the background item was not enabled within the timeout"))
defer cancel()
for {
select {
case <-ctx.Done():
return context.Cause(ctx)
case <-ticker.C:
switch status := daemonStatus(bundlePath); status {
case ServiceStatusEnabled:
return nil
case ServiceStatusRequiresApproval:
// Continue waiting for the user to approve the login item.
case ServiceStatusNotRegistered, ServiceStatusNotFound:
// Something happened to the service since we started waiting, abort.
return trace.Errorf("encountered unexpected service status %q", status)
default:
return trace.Errorf("encountered unknown service status %q", status)
}
}
}
}
// DaemonStatus returns the status of the background item responsible for launching the daemon.
func DaemonStatus() (ServiceStatus, error) {
bundlePath, err := bundlePath()
if err != nil {
return 0, trace.Wrap(err)
}
return daemonStatus(bundlePath), nil
}
func daemonStatus(bundlePath string) ServiceStatus {
cBundlePath := C.CString(bundlePath)
defer C.free(unsafe.Pointer(cBundlePath))
return ServiceStatus(C.DaemonStatus(cBundlePath))
}
// https://developer.apple.com/documentation/servicemanagement/smappservice/status-swift.enum?language=objc
type ServiceStatus int
const (
ServiceStatusNotRegistered ServiceStatus = 0
ServiceStatusEnabled ServiceStatus = 1
ServiceStatusRequiresApproval ServiceStatus = 2
ServiceStatusNotFound ServiceStatus = 3
)
func (s ServiceStatus) String() string {
switch s {
case ServiceStatusNotRegistered:
return "not registered"
case ServiceStatusEnabled:
return "enabled"
case ServiceStatusRequiresApproval:
return "requires approval"
case ServiceStatusNotFound:
return "not found"
default:
return strconv.Itoa(int(s))
}
}
// bundlePath returns a path to the bundle that the current executable comes from.
// If the current executable is a symlink, it resolves the symlink. This is to address a scenario
// where tsh is installed from tsh.pkg and symlinked to /usr/local/bin/tsh, in which case the
// mainBundle function from NSBundle incorrectly points to /usr/local/bin as the bundle path.
// https://developer.apple.com/documentation/foundation/nsbundle/1410786-mainbundle
//
// Returns an error if the dir of the current executable doesn't end with "/Contents/MacOS", likely
// because the executable is not in an app bundle.
func bundlePath() (string, error) {
exe, err := os.Executable()
if err != nil {
return "", trace.Wrap(err)
}
absExe, err := utils.NormalizePath(exe, true /* evaluateSymlinks */)
if err != nil {
return "", trace.Wrap(err)
}
dir := filepath.Dir(absExe)
const appBundleSuffix = "/Contents/MacOS"
if !strings.HasSuffix(dir, appBundleSuffix) {
exeName := filepath.Base(exe)
log.DebugContext(context.Background(), "Current executable is likely outside of app bundle", "exe", absExe)
return "", trace.NotFound("%s is not in an app bundle", exeName)
}
return strings.TrimSuffix(dir, appBundleSuffix), nil
}
func startByCalling(ctx context.Context, bundlePath string, config Config) error {
// C.StartVnet might hang if the daemon cannot be successfully spawned.
const daemonStartTimeout = 20 * time.Second
ctx, cancel := context.WithTimeoutCause(ctx, daemonStartTimeout,
errors.New("could not connect to the VNet daemon within the timeout"))
defer cancel()
defer C.InvalidateDaemonClient()
errC := make(chan error, 1)
go func() {
req := C.StartVnetRequest{
bundle_path: C.CString(bundlePath),
socket_path: C.CString(config.SocketPath),
ipv6_prefix: C.CString(config.IPv6Prefix),
dns_addr: C.CString(config.DNSAddr),
home_path: C.CString(config.HomePath),
}
defer func() {
C.free(unsafe.Pointer(req.bundle_path))
C.free(unsafe.Pointer(req.socket_path))
C.free(unsafe.Pointer(req.ipv6_prefix))
C.free(unsafe.Pointer(req.dns_addr))
C.free(unsafe.Pointer(req.home_path))
}()
var res C.StartVnetResult
defer func() {
C.free(unsafe.Pointer(res.error_domain))
C.free(unsafe.Pointer(res.error_description))
}()
// This call gets unblocked when C.InvalidateDaemonClient is called when startByCalling exits.
C.StartVnet(&req, &res)
if !res.ok {
errorDomain := C.GoString(res.error_domain)
errorCode := int(res.error_code)
if errorDomain == vnetErrorDomain && errorCode == errorCodeAlreadyRunning {
errC <- trace.Wrap(errAlreadyRunning)
return
}
if errorDomain == nsCocoaErrorDomain && errorCode == errorCodeNSXPCConnectionInterrupted {
const clientNSXPCConnectionInterruptedDebugMsg = "The connection was interrupted when trying to " +
"reach the XPC service. If there's no clear error logs on the daemon side, it might mean that " +
"the client does not satisfy the code signing requirement enforced by the daemon. " +
"Start capturing logs in Console.app and repeat the scenario. Look for " +
"\"xpc_support_check_token: <private> error: <private> status: -67050\" in the logs to verify " +
"that the connection was interrupted due to the code signing requirement."
log.DebugContext(ctx, clientNSXPCConnectionInterruptedDebugMsg)
errC <- trace.Wrap(errXPCConnectionInterrupted)
return
}
if errorDomain == vnetErrorDomain && errorCode == errorCodeMissingCodeSigningIdentifiers {
errC <- trace.Wrap(errMissingCodeSigningIdentifiers)
return
}
if errorDomain == nsCocoaErrorDomain && errorCode == errorCodeNSXPCConnectionCodeSigningRequirementFailure {
// If the client submits TELEPORT_HOME to which the user doesn't have access, the daemon is
// going to shut down with an error soon after starting. Because of that, macOS won't have
// enough time to perform the verification of the code signing requirement of the daemon, as
// requested by the client.
//
// In that scenario, macOS is going to simply error that connection with
// NSXPCConnectionCodeSigningRequirementFailure. Without looking at logs, it's not possible
// to differentiate that from a "legitimate" failure caused by an incorrect requirement.
errC <- trace.Wrap(errXPCConnectionCodeSigningRequirementFailure, "either daemon is not signed correctly or it shut down before signature could be verified")
return
}
errC <- trace.Errorf("could not start VNet daemon: %v", C.GoString(res.error_description))
return
}
errC <- nil
}()
select {
case <-ctx.Done():
return trace.Wrap(context.Cause(ctx))
case err := <-errC:
return trace.Wrap(err, "connecting to the VNet daemon")
}
}
func sleepOrDone(ctx context.Context, d time.Duration) error {
timer := time.NewTimer(d)
defer timer.Stop()
select {
case <-ctx.Done():
return trace.Wrap(ctx.Err())
case <-timer.C:
return nil
}
}