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Modernize chroot(8).

This commit is contained in:
Jonas 'Sortie' Termansen 2024-06-16 20:15:31 +00:00
parent 5d18d8be30
commit 49bf6298a7
1 changed files with 64 additions and 46 deletions
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110
utils/chroot.c
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2013, 2015, 2023 Jonas 'Sortie' Termansen.
* Copyright (c) 2013, 2015, 2023, 2024 Jonas 'Sortie' Termansen.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
@ -91,14 +91,13 @@ int main(int argc, char* argv[])
if ( argc < 2 )
error(1, 0, "missing operand, expected new root directory");
if ( devices )
bool need_cleanup = devices;
// TODO: Why do we even have signal handling instead of just blocking the
// signals and waiting for the subprocess to react?
if ( need_cleanup )
{
if ( asprintf(&mount_point_dev, "%s/dev", argv[1]) < 0 )
error(1, errno, "asprintf: `%s/dev'", argv[1]);
// Create a device directory in the root filesystem.
mkdir(mount_point_dev, 0755);
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = unmount_handler;
@ -107,6 +106,15 @@ int main(int argc, char* argv[])
sigaction(SIGINT, &sa, NULL);
sigaction(SIGQUIT, &sa, NULL);
sigaction(SIGTERM, &sa, NULL);
}
if ( devices )
{
if ( asprintf(&mount_point_dev, "%s/dev", argv[1]) < 0 )
error(1, errno, "asprintf: `%s/dev'", argv[1]);
// Create a device directory in the root filesystem.
mkdir(mount_point_dev, 0755);
// Mount the current device directory inside the new root filesystem.
int old_dev_fd = open("/dev", O_DIRECTORY | O_RDONLY);
@ -114,55 +122,65 @@ int main(int argc, char* argv[])
fsm_fsbind(old_dev_fd, new_dev_fd, 0);
close(new_dev_fd);
close(old_dev_fd);
}
sigset_t oldset, sigs;
sigset_t oldset, sigs;
if ( need_cleanup )
{
sigemptyset(&sigs);
sigaddset(&sigs, SIGHUP);
sigaddset(&sigs, SIGINT);
sigaddset(&sigs, SIGQUIT);
sigaddset(&sigs, SIGTERM);
sigprocmask(SIG_BLOCK, &sigs, &oldset);
pid_t child_pid = fork();
if ( child_pid < 0 )
{
int errnum = errno;
unmount(mount_point_dev, 0);
mount_point_dev = NULL;
sigprocmask(SIG_SETMASK, &oldset, NULL);
error(1, errnum, "fork");
}
if ( child_pid != 0 )
{
sigprocmask(SIG_SETMASK, &oldset, NULL);
int code;
waitpid(child_pid, &code, 0);
sigprocmask(SIG_BLOCK, &sigs, &oldset);
unmount(mount_point_dev, 0);
sigprocmask(SIG_SETMASK, &oldset, NULL);
mount_point_dev = NULL;
if ( WIFEXITED(code) )
return WEXITSTATUS(code);
raise(WTERMSIG(code));
return 128 + WTERMSIG(code);
}
signal(SIGHUP, SIG_DFL);
signal(SIGINT, SIG_DFL);
signal(SIGQUIT, SIG_DFL);
signal(SIGTERM, SIG_DFL);
sigprocmask(SIG_SETMASK, &oldset, NULL);
}
if ( chroot(argv[1]) != 0 )
error(1, errno, "`%s'", argv[1]);
pid_t child_pid = need_cleanup ? fork() : 0;
if ( child_pid < 0 )
{
int errnum = errno;
unmount(mount_point_dev, 0);
mount_point_dev = NULL;
sigprocmask(SIG_SETMASK, &oldset, NULL);
error(1, errnum, "fork");
}
if ( chdir("/.") != 0 )
error(1, errno, "chdir: `%s/.'", argv[1]);
if ( !child_pid )
{
if ( need_cleanup )
{
signal(SIGHUP, SIG_DFL);
signal(SIGINT, SIG_DFL);
signal(SIGQUIT, SIG_DFL);
signal(SIGTERM, SIG_DFL);
sigprocmask(SIG_SETMASK, &oldset, NULL);
}
char* default_argv[] = { (char*) "sh", (char*) NULL };
if ( chroot(argv[1]) != 0 )
error(1, errno, "`%s'", argv[1]);
char** exec_argv = 3 <= argc ? argv + 2 : default_argv;
execvp(exec_argv[0], exec_argv);
if ( chdir("/.") != 0 )
error(1, errno, "chdir: `%s/.'", argv[1]);
error(0, errno, "`%s'", exec_argv[0]);
_exit(127);
char* default_argv[] = { (char*) "sh", (char*) NULL };
char** exec_argv = 3 <= argc ? argv + 2 : default_argv;
execvp(exec_argv[0], exec_argv);
error(0, errno, "`%s'", exec_argv[0]);
_exit(127);
}
sigprocmask(SIG_SETMASK, &oldset, NULL);
int code;
waitpid(child_pid, &code, 0);
sigprocmask(SIG_BLOCK, &sigs, &oldset);
if ( devices )
unmount(mount_point_dev, 0);
sigprocmask(SIG_SETMASK, &oldset, NULL);
mount_point_dev = NULL;
if ( WIFEXITED(code) )
return WEXITSTATUS(code);
raise(WTERMSIG(code));
return 128 + WTERMSIG(code);
}