app: separate appSeal finalise method

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/process.go

@@ -0,0 +1,268 @@
+package app
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"git.gensokyo.uk/security/fortify/fst"
+	"git.gensokyo.uk/security/fortify/helper"
+	"git.gensokyo.uk/security/fortify/internal/app/shim"
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+	"git.gensokyo.uk/security/fortify/internal/state"
+	"git.gensokyo.uk/security/fortify/system"
+)
+
+const shimSetupTimeout = 5 * time.Second
+
+func (a *app) Run(ctx context.Context, rs *fst.RunState) error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	if rs == nil {
+		panic("attempted to pass nil state to run")
+	}
+
+	// resolve exec paths
+	shimExec := [2]string{helper.BubblewrapName}
+	if len(a.appSeal.command) > 0 {
+		shimExec[1] = a.appSeal.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 fmsg.WrapError(err,
+					fmt.Sprintf("executable file %q not found in $PATH", n))
+			}
+		}
+	}
+
+	// startup will go ahead, commit system setup
+	if err := a.appSeal.sys.Commit(ctx); err != nil {
+		return err
+	}
+	a.appSeal.needRevert = true
+
+	// start shim via manager
+	a.shim = new(shim.Shim)
+	waitErr := make(chan error, 1)
+	if startTime, err := a.shim.Start(
+		a.appSeal.user.aid.String(),
+		a.appSeal.user.supp,
+		a.appSeal.bwrapSync,
+	); err != nil {
+		return err
+	} else {
+		// shim process created
+		rs.Start = true
+
+		shimSetupCtx, shimSetupCancel := context.WithDeadline(ctx, time.Now().Add(shimSetupTimeout))
+		defer shimSetupCancel()
+
+		// start waiting for shim
+		go func() {
+			waitErr <- a.shim.Unwrap().Wait()
+			// cancel shim setup in case shim died before receiving payload
+			shimSetupCancel()
+		}()
+
+		// send payload
+		if err = a.shim.Serve(shimSetupCtx, &shim.Payload{
+			Argv:  a.appSeal.command,
+			Exec:  shimExec,
+			Bwrap: a.appSeal.container,
+			Home:  a.appSeal.user.data,
+
+			Verbose: fmsg.Load(),
+		}); err != nil {
+			return err
+		}
+
+		// shim accepted setup payload, create process state
+		sd := state.State{
+			ID:   a.id.unwrap(),
+			PID:  a.shim.Unwrap().Process.Pid,
+			Time: *startTime,
+		}
+
+		// register process state
+		var err0 = new(StateStoreError)
+		err0.Inner, err0.DoErr = a.appSeal.store.Do(a.appSeal.user.aid.unwrap(), func(c state.Cursor) {
+			err0.InnerErr = c.Save(&sd, a.appSeal.ct)
+		})
+		a.appSeal.stateInStore = true
+		if err = err0.equiv("cannot save process state:"); err != nil {
+			return err
+		}
+	}
+
+	select {
+	// wait for process and resolve exit code
+	case err := <-waitErr:
+		if err != nil {
+			var exitError *exec.ExitError
+			if !errors.As(err, &exitError) {
+				// should be unreachable
+				rs.WaitErr = err
+			}
+
+			// store non-zero return code
+			rs.ExitCode = exitError.ExitCode()
+		} else {
+			rs.ExitCode = a.shim.Unwrap().ProcessState.ExitCode()
+		}
+		if fmsg.Load() {
+			fmsg.Verbosef("process %d exited with exit code %d", a.shim.Unwrap().Process.Pid, rs.ExitCode)
+		}
+
+	// this is reached when a fault makes an already running shim impossible to continue execution
+	// however a kill signal could not be delivered (should actually always happen like that since fsu)
+	// the effects of this is similar to the alternative exit path and ensures shim death
+	case err := <-a.shim.WaitFallback():
+		rs.ExitCode = 255
+		log.Printf("cannot terminate shim on faulted setup: %v", err)
+
+	// alternative exit path relying on shim behaviour on monitor process exit
+	case <-ctx.Done():
+		fmsg.Verbose("alternative exit path selected")
+	}
+
+	// child process exited, resume output
+	fmsg.Resume()
+
+	// print queued up dbus messages
+	if a.appSeal.dbusMsg != nil {
+		a.appSeal.dbusMsg()
+	}
+
+	// update store and revert app setup transaction
+	e := new(StateStoreError)
+	e.Inner, e.DoErr = a.appSeal.store.Do(a.appSeal.user.aid.unwrap(), func(b state.Cursor) {
+		e.InnerErr = func() error {
+			// destroy defunct state entry
+			if cmd := a.shim.Unwrap(); cmd != nil && a.appSeal.stateInStore {
+				if err := b.Destroy(a.id.unwrap()); err != nil {
+					return err
+				}
+			}
+
+			// enablements of remaining launchers
+			rt, ec := new(system.Enablements), new(system.Criteria)
+			ec.Enablements = new(system.Enablements)
+			ec.Set(system.Process)
+			if states, err := b.Load(); err != nil {
+				return err
+			} else {
+				if l := len(states); l == 0 {
+					// cleanup globals as the final launcher
+					fmsg.Verbose("no other launchers active, will clean up globals")
+					ec.Set(system.User)
+				} else {
+					fmsg.Verbosef("found %d active launchers, cleaning up without globals", l)
+				}
+
+				// accumulate capabilities of other launchers
+				for i, s := range states {
+					if s.Config != nil {
+						*rt |= s.Config.Confinement.Enablements
+					} else {
+						log.Printf("state entry %d does not contain config", i)
+					}
+				}
+			}
+			// invert accumulated enablements for cleanup
+			for i := system.Enablement(0); i < system.Enablement(system.ELen); i++ {
+				if !rt.Has(i) {
+					ec.Set(i)
+				}
+			}
+			if fmsg.Load() {
+				labels := make([]string, 0, system.ELen+1)
+				for i := system.Enablement(0); i < system.Enablement(system.ELen+2); i++ {
+					if ec.Has(i) {
+						labels = append(labels, system.TypeString(i))
+					}
+				}
+				if len(labels) > 0 {
+					fmsg.Verbose("reverting operations labelled", strings.Join(labels, ", "))
+				}
+			}
+
+			if a.appSeal.needRevert {
+				if err := a.appSeal.sys.Revert(ec); err != nil {
+					return err.(RevertCompoundError)
+				}
+			}
+
+			return nil
+		}()
+	})
+
+	e.Err = a.appSeal.store.Close()
+	return e.equiv("error returned during cleanup:", e)
+}
+
+// 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 && e.DoErr == nil && e.InnerErr == nil && e.Err == nil {
+		return nil
+	} else {
+		return fmsg.WrapErrorSuffix(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
+}