app: rename app implementation package

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

internal/app/shim.go

@@ -1,181 +0,0 @@
-package app
-
-import (
-	"context"
-	"errors"
-	"log"
-	"os"
-	"os/exec"
-	"os/signal"
-	"syscall"
-	"time"
-
-	"git.gensokyo.uk/security/fortify/internal"
-	"git.gensokyo.uk/security/fortify/internal/fmsg"
-	"git.gensokyo.uk/security/fortify/sandbox"
-	"git.gensokyo.uk/security/fortify/sandbox/seccomp"
-)
-
-/*
-#include <stdlib.h>
-#include <unistd.h>
-#include <stdio.h>
-#include <errno.h>
-#include <signal.h>
-
-static pid_t f_shim_param_ppid = -1;
-
-// this cannot unblock fmsg since Go code is not async-signal-safe
-static void f_shim_sigaction(int sig, siginfo_t *si, void *ucontext) {
-  if (sig != SIGCONT || si == NULL) {
-    // unreachable
-    fprintf(stderr, "sigaction: sa_sigaction got invalid siginfo\n");
-    return;
-  }
-
-  // monitor requests shim exit
-  if (si->si_pid == f_shim_param_ppid)
-    exit(254);
-
-  fprintf(stderr, "sigaction: got SIGCONT from process %d\n", si->si_pid);
-
-  // shim orphaned before monitor delivers a signal
-  if (getppid() != f_shim_param_ppid)
-    exit(3);
-}
-
-void f_shim_setup_cont_signal(pid_t ppid) {
-  struct sigaction new_action = {0}, old_action = {0};
-  if (sigaction(SIGCONT, NULL, &old_action) != 0)
-    return;
-  if (old_action.sa_handler != SIG_DFL) {
-    errno = ENOTRECOVERABLE;
-    return;
-  }
-
-  new_action.sa_sigaction = f_shim_sigaction;
-  if (sigemptyset(&new_action.sa_mask) != 0)
-    return;
-  new_action.sa_flags = SA_ONSTACK | SA_SIGINFO;
-
-  if (sigaction(SIGCONT, &new_action, NULL) != 0)
-    return;
-
-  errno = 0;
-  f_shim_param_ppid = ppid;
-}
-*/
-import "C"
-
-const shimEnv = "FORTIFY_SHIM"
-
-type shimParams struct {
-	// monitor pid, checked against ppid in signal handler
-	Monitor int
-
-	// finalised container params
-	Container *sandbox.Params
-	// path to outer home directory
-	Home string
-
-	// verbosity pass through
-	Verbose bool
-}
-
-// ShimMain is the main function of the shim process and runs as the unconstrained target user.
-func ShimMain() {
-	fmsg.Prepare("shim")
-
-	if err := sandbox.SetDumpable(sandbox.SUID_DUMP_DISABLE); err != nil {
-		log.Fatalf("cannot set SUID_DUMP_DISABLE: %s", err)
-	}
-
-	var (
-		params     shimParams
-		closeSetup func() error
-	)
-	if f, err := sandbox.Receive(shimEnv, &params, nil); err != nil {
-		if errors.Is(err, sandbox.ErrInvalid) {
-			log.Fatal("invalid config descriptor")
-		}
-		if errors.Is(err, sandbox.ErrNotSet) {
-			log.Fatal("FORTIFY_SHIM not set")
-		}
-
-		log.Fatalf("cannot receive shim setup params: %v", err)
-	} else {
-		internal.InstallFmsg(params.Verbose)
-		closeSetup = f
-
-		// the Go runtime does not expose siginfo_t so SIGCONT is handled in C to check si_pid
-		if _, err = C.f_shim_setup_cont_signal(C.pid_t(params.Monitor)); err != nil {
-			log.Fatalf("cannot install SIGCONT handler: %v", err)
-		}
-
-		// pdeath_signal delivery is checked as if the dying process called kill(2), see kernel/exit.c
-		if _, _, errno := syscall.Syscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, uintptr(syscall.SIGCONT), 0); errno != 0 {
-			log.Fatalf("cannot set parent-death signal: %v", errno)
-		}
-	}
-
-	if params.Container == nil || params.Container.Ops == nil {
-		log.Fatal("invalid container params")
-	}
-
-	// close setup socket
-	if err := closeSetup(); err != nil {
-		log.Printf("cannot close setup pipe: %v", err)
-		// not fatal
-	}
-
-	// ensure home directory as target user
-	if s, err := os.Stat(params.Home); err != nil {
-		if os.IsNotExist(err) {
-			if err = os.Mkdir(params.Home, 0700); err != nil {
-				log.Fatalf("cannot create home directory: %v", err)
-			}
-		} else {
-			log.Fatalf("cannot access home directory: %v", err)
-		}
-
-		// home directory is created, proceed
-	} else if !s.IsDir() {
-		log.Fatalf("path %q is not a directory", params.Home)
-	}
-
-	var name string
-	if len(params.Container.Args) > 0 {
-		name = params.Container.Args[0]
-	}
-	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
-	defer stop() // unreachable
-	container := sandbox.New(ctx, name)
-	container.Params = *params.Container
-	container.Stdin, container.Stdout, container.Stderr = os.Stdin, os.Stdout, os.Stderr
-	container.Cancel = func(cmd *exec.Cmd) error { return cmd.Process.Signal(os.Interrupt) }
-	container.WaitDelay = 2 * time.Second
-
-	if err := container.Start(); err != nil {
-		fmsg.PrintBaseError(err, "cannot start container:")
-		os.Exit(1)
-	}
-	if err := container.Serve(); err != nil {
-		fmsg.PrintBaseError(err, "cannot configure container:")
-	}
-
-	if err := seccomp.Load(seccomp.PresetCommon); err != nil {
-		log.Fatalf("cannot load syscall filter: %v", err)
-	}
-
-	if err := container.Wait(); err != nil {
-		var exitError *exec.ExitError
-		if !errors.As(err, &exitError) {
-			if errors.Is(err, context.Canceled) {
-				os.Exit(2)
-			}
-			log.Printf("wait: %v", err)
-			os.Exit(127)
-		}
-		os.Exit(exitError.ExitCode())
-	}
-}