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authorOphestra <cat@gensokyo.uk>2025-04-12 10:54:24 +0900
committerOphestra <cat@gensokyo.uk>2025-04-12 10:54:24 +0900
commit0d7c1a9a4356614f035225aeb24e66421879a99b (patch)
treec490cfd0f75fbf0218045e277812fb5b6173d4e3 /internal/app/shim.go
parentae6f5ede1928c9d0a2d480b6a924914e8599529f (diff)
app: rename app implementation package
Signed-off-by: Ophestra <cat@gensokyo.uk>
Diffstat (limited to 'internal/app/shim.go')
-rw-r--r--internal/app/shim.go181
1 files changed, 0 insertions, 181 deletions
diff --git a/internal/app/shim.go b/internal/app/shim.go
deleted file mode 100644
index ea11dcc1..00000000
--- a/internal/app/shim.go
+++ /dev/null
@@ -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())
- }
-}