fortify/internal/app/start.go

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package app
import (
"errors"
"fmt"
"os"
"os/exec"
"path"
"path/filepath"
"strconv"
"time"
"git.ophivana.moe/cat/fortify/helper"
"git.ophivana.moe/cat/fortify/internal/shim"
"git.ophivana.moe/cat/fortify/internal/state"
"git.ophivana.moe/cat/fortify/internal/verbose"
)
type (
// ProcessError encapsulates errors returned by starting *exec.Cmd
ProcessError BaseError
// ShimError encapsulates errors returned by shim.ServeConfig.
ShimError BaseError
)
// Start starts the fortified child
func (a *app) Start() error {
a.lock.Lock()
defer a.lock.Unlock()
// resolve exec paths
shimExec := [3]string{a.seal.sys.executable, helper.BubblewrapName}
if len(a.seal.command) > 0 {
shimExec[2] = a.seal.command[0]
}
for i, n := range shimExec {
if len(n) == 0 {
continue
}
if filepath.Base(n) == n {
if s, err := exec.LookPath(n); err == nil {
shimExec[i] = s
} else {
return (*ProcessError)(wrapError(err, fmt.Sprintf("cannot find %q: %v", n, err)))
}
}
}
if err := a.seal.sys.commit(); err != nil {
return err
}
// select command builder
var commandBuilder func(shimEnv string) (args []string)
switch a.seal.launchOption {
case LaunchMethodSudo:
commandBuilder = a.commandBuilderSudo
case LaunchMethodMachineCtl:
commandBuilder = a.commandBuilderMachineCtl
default:
panic("unreachable")
}
// configure child process
confSockPath := path.Join(a.seal.share, "shim")
a.cmd = exec.Command(a.seal.toolPath, commandBuilder(shim.EnvShim+"="+confSockPath)...)
a.cmd.Env = []string{}
a.cmd.Stdin = os.Stdin
a.cmd.Stdout = os.Stdout
a.cmd.Stderr = os.Stderr
a.cmd.Dir = a.seal.RunDirPath
if wls, err := shim.ServeConfig(confSockPath, a.seal.sys.uid, &shim.Payload{
Argv: a.seal.command,
Exec: shimExec,
Bwrap: a.seal.sys.bwrap,
WL: a.seal.wlDone != nil,
Verbose: verbose.Get(),
}, a.seal.wl, a.seal.wlDone); err != nil {
return (*ShimError)(wrapError(err, "cannot listen on shim socket:", err))
} else {
a.wayland = wls
}
// start shim
verbose.Println("starting shim as target user:", a.cmd)
if err := a.cmd.Start(); err != nil {
return (*ProcessError)(wrapError(err, "cannot start process:", err))
}
startTime := time.Now().UTC()
// create process state
sd := state.State{
PID: a.cmd.Process.Pid,
Command: a.seal.command,
Capability: a.seal.et,
Launcher: a.seal.toolPath,
Argv: a.cmd.Args,
Time: startTime,
}
// register process state
var err = new(StateStoreError)
err.Inner, err.DoErr = a.seal.store.Do(func(b state.Backend) {
err.InnerErr = b.Save(&sd)
})
return err.equiv("cannot save process state:", err)
}
// StateStoreError is returned for a failed state save
type StateStoreError struct {
// whether inner function was called
Inner bool
// error returned by state.Store Do method
DoErr error
// error returned by state.Backend Save method
InnerErr error
// any other errors needing to be tracked
Err error
}
func (e *StateStoreError) equiv(a ...any) error {
if e.Inner == true && e.DoErr == nil && e.InnerErr == nil && e.Err == nil {
return nil
} else {
return wrapError(e, a...)
}
}
func (e *StateStoreError) Error() string {
if e.Inner && e.InnerErr != nil {
return e.InnerErr.Error()
}
if e.DoErr != nil {
return e.DoErr.Error()
}
if e.Err != nil {
return e.Err.Error()
}
return "(nil)"
}
func (e *StateStoreError) Unwrap() (errs []error) {
errs = make([]error, 0, 3)
if e.DoErr != nil {
errs = append(errs, e.DoErr)
}
if e.InnerErr != nil {
errs = append(errs, e.InnerErr)
}
if e.Err != nil {
errs = append(errs, e.Err)
}
return
}
type RevertCompoundError interface {
Error() string
Unwrap() []error
}
func (a *app) Wait() (int, error) {
a.lock.Lock()
defer a.lock.Unlock()
var r int
// wait for process and resolve exit code
if err := a.cmd.Wait(); err != nil {
var exitError *exec.ExitError
if !errors.As(err, &exitError) {
// should be unreachable
a.wait = err
}
// store non-zero return code
r = exitError.ExitCode()
} else {
r = a.cmd.ProcessState.ExitCode()
}
verbose.Println("process", strconv.Itoa(a.cmd.Process.Pid), "exited with exit code", r)
// close wayland connection
if a.wayland != nil {
close(a.seal.wlDone)
if err := a.wayland.Close(); err != nil {
fmt.Println("fortify: cannot close wayland connection:", err)
}
}
// update store and revert app setup transaction
e := new(StateStoreError)
e.Inner, e.DoErr = a.seal.store.Do(func(b state.Backend) {
e.InnerErr = func() error {
// destroy defunct state entry
if err := b.Destroy(a.cmd.Process.Pid); err != nil {
return err
}
// enablements of remaining launchers
rt, tags := new(state.Enablements), new(state.Enablements)
tags.Set(state.EnableLength + 1)
if states, err := b.Load(); err != nil {
return err
} else {
if l := len(states); l == 0 {
// cleanup globals as the final launcher
verbose.Println("no other launchers active, will clean up globals")
tags.Set(state.EnableLength)
} else {
verbose.Printf("found %d active launchers, cleaning up without globals\n", l)
}
// accumulate capabilities of other launchers
for _, s := range states {
*rt |= s.Capability
}
}
// invert accumulated enablements for cleanup
for i := state.Enablement(0); i < state.EnableLength; i++ {
if !rt.Has(i) {
tags.Set(i)
}
}
if verbose.Get() {
ct := make([]state.Enablement, 0, state.EnableLength)
for i := state.Enablement(0); i < state.EnableLength; i++ {
if tags.Has(i) {
ct = append(ct, i)
}
}
if len(ct) > 0 {
verbose.Println("will revert operations tagged", ct, "as no remaining launchers hold these enablements")
}
}
if err := a.seal.sys.revert(tags); err != nil {
return err.(RevertCompoundError)
}
return nil
}()
})
e.Err = a.seal.store.Close()
return r, e.equiv("error returned during cleanup:", e)
}