int steal_cleanup_child(struct steal_pty_state *steal) {
if (ptrace_memcpy_to_child(&steal->child,
steal->child_scratch,
"/dev/null", sizeof("/dev/null"))) {
return steal->child.error;
}
int nullfd = do_syscall(&steal->child, openat, -1, steal->child_scratch, O_RDWR, 0, 0, 0);
if (nullfd < 0) {
return steal->child.error;
}
int i;
for (i = 0; i < steal->master_fds.n; ++i) {
do_dup2(&steal->child, nullfd, steal->master_fds.fds[i]);
}
do_syscall(&steal->child, close, nullfd, 0, 0, 0, 0, 0);
do_syscall(&steal->child, close, steal->child_fd, 0, 0, 0, 0, 0);
steal->child_fd = 0;
ptrace_restore_regs(&steal->child);
ptrace_detach_child(&steal->child);
ptrace_wait(&steal->child);
return 0;
}
int grab_pid(pid_t pid, struct ptrace_child *child, child_addr_t *scratch) {
int err;
if (ptrace_attach_child(child, pid)) {
err = child->error;
goto out;
}
if (ptrace_advance_to_state(child, ptrace_at_syscall)) {
err = child->error;
goto out;
}
if (ptrace_save_regs(child)) {
err = child->error;
goto out;
}
if ((err = mmap_scratch(child, scratch)))
goto out_restore_regs;
return 0;
out_restore_regs:
ptrace_restore_regs(child);
out:
ptrace_detach_child(child);
return err;
}
int preflight_check(pid_t pid) {
struct ptrace_child child;
debug("Making sure we have permission to attach...");
if (ptrace_attach_child(&child, pid)) {
return child.error;
}
ptrace_detach_child(&child);
return 0;
}
// Attach to the session leader of the stolen session, and block
// SIGHUP so that if and when the terminal emulator tries to HUP it,
// it doesn't die.
int steal_block_hup(struct steal_pty_state *steal) {
struct ptrace_child leader;
child_addr_t scratch = 0;
int err = 0;
if ((err = grab_pid(steal->target_stat.sid, &leader, &scratch)))
return err;
err = ignore_hup(&leader, scratch);
ptrace_restore_regs(&leader);
ptrace_detach_child(&leader);
return err;
}
int do_setsid(struct ptrace_child *child) {
int err = 0;
struct ptrace_child dummy;
err = do_fork(child);
if (err < 0)
return err;
debug("Forked a child: %ld", child->forked_pid);
err = ptrace_finish_attach(&dummy, child->forked_pid);
if (err < 0)
goto out_kill;
dummy.state = ptrace_after_syscall;
copy_user(&dummy, child);
if (ptrace_restore_regs(&dummy)) {
err = dummy.error;
goto out_kill;
}
err = do_syscall(&dummy, setpgid, 0, 0, 0, 0, 0, 0);
if (err < 0) {
error("Failed to setpgid: %s", strerror(-err));
goto out_kill;
}
move_process_group(child, child->pid, dummy.pid);
err = do_syscall(child, setsid, 0, 0, 0, 0, 0, 0);
if (err < 0) {
error("Failed to setsid: %s", strerror(-err));
move_process_group(child, dummy.pid, child->pid);
goto out_kill;
}
debug("Did setsid()");
out_kill:
kill(dummy.pid, SIGKILL);
ptrace_wait(&dummy);
ptrace_detach_child(&dummy);
do_syscall(child, wait4, dummy.pid, 0, WNOHANG, 0, 0, 0);
return err;
}
int steal_pty(pid_t pid, int *pty) {
int err = 0;
struct steal_pty_state steal = {};
long page_size = sysconf(_SC_PAGE_SIZE);
if ((err = preflight_check(pid)))
goto out;
if ((err = get_terminal_state(&steal, pid)))
goto out;
if ((err = setup_steal_socket(&steal)))
goto out;
debug("Listening on socket: %s", steal.addr_un.sun_path);
debug("Attaching terminal emulator pid=%d", steal.emulator_pid);
if ((err = grab_pid(steal.emulator_pid, &steal.child, &steal.child_scratch)))
goto out;
debug("Attached to terminal emulator (pid %d)",
(int)steal.emulator_pid);
if ((err = find_master_fd(&steal))) {
error("Unable to find the fd for the pty!");
goto out;
}
if ((err = setup_steal_socket_child(&steal)))
goto out;
if ((err = steal_child_pty(&steal)))
goto out;
if ((err = steal_block_hup(&steal)))
goto out;
if ((err = steal_cleanup_child(&steal)))
goto out;
goto out_no_child;
out:
if (steal.ptyfd) {
close(steal.ptyfd);
steal.ptyfd = 0;
}
if (steal.child_fd > 0)
do_syscall(&steal.child, close, steal.child_fd, 0, 0, 0, 0, 0);
if (steal.child_scratch > 0)
do_unmap(&steal.child, steal.child_scratch, page_size);
if (steal.child.state != ptrace_detached) {
ptrace_restore_regs(&steal.child);
ptrace_detach_child(&steal.child);
}
out_no_child:
if (steal.sockfd > 0) {
close(steal.sockfd);
unlink(steal.addr_un.sun_path);
}
if (steal.tmpdir[0]) {
rmdir(steal.tmpdir);
}
if (steal.ptyfd)
*pty = steal.ptyfd;
free(steal.master_fds.fds);
return err;
}
int attach_child(pid_t pid, const char *pty, int force_stdio) {
struct ptrace_child child;
child_addr_t scratch_page = -1;
int *child_tty_fds = NULL, n_fds, child_fd, statfd = -1;
int i;
int err = 0;
long page_size = sysconf(_SC_PAGE_SIZE);
#ifdef __linux__
char stat_path[PATH_MAX];
#endif
if ((err = check_pgroup(pid))) {
return err;
}
if ((err = preflight_check(pid))) {
return err;
}
debug("Using tty: %s", pty);
if ((err = copy_tty_state(pid, pty))) {
if (err == ENOTTY && !force_stdio) {
error("Target is not connected to a terminal.\n"
" Use -s to force attaching anyways.");
return err;
}
}
#ifdef __linux__
snprintf(stat_path, sizeof stat_path, "/proc/%d/stat", pid);
statfd = open(stat_path, O_RDONLY);
if (statfd < 0) {
error("Unable to open %s: %s", stat_path, strerror(errno));
return -statfd;
}
#endif
kill(pid, SIGTSTP);
wait_for_stop(pid, statfd);
if ((err = grab_pid(pid, &child, &scratch_page))) {
goto out_cont;
}
if (force_stdio) {
child_tty_fds = malloc(3 * sizeof(int));
if (!child_tty_fds) {
err = ENOMEM;
goto out_unmap;
}
n_fds = 3;
child_tty_fds[0] = 0;
child_tty_fds[1] = 1;
child_tty_fds[2] = 2;
} else {
child_tty_fds = get_child_tty_fds(&child, statfd, &n_fds);
if (!child_tty_fds) {
err = child.error;
goto out_unmap;
}
}
if (ptrace_memcpy_to_child(&child, scratch_page, pty, strlen(pty) + 1)) {
err = child.error;
error("Unable to memcpy the pty path to child.");
goto out_free_fds;
}
child_fd = do_syscall(&child, openat,
-1, scratch_page, O_RDWR | O_NOCTTY,
0, 0, 0);
if (child_fd < 0) {
err = child_fd;
error("Unable to open the tty in the child.");
goto out_free_fds;
}
debug("Opened the new tty in the child: %d", child_fd);
err = ignore_hup(&child, scratch_page);
if (err < 0)
goto out_close;
err = do_syscall(&child, getsid, 0, 0, 0, 0, 0, 0);
if (err != child.pid) {
debug("Target is not a session leader, attempting to setsid.");
err = do_setsid(&child);
} else {
do_syscall(&child, ioctl, child_tty_fds[0], TIOCNOTTY, 0, 0, 0, 0);
}
if (err < 0)
goto out_close;
err = do_syscall(&child, ioctl, child_fd, TIOCSCTTY, 1, 0, 0, 0);
if (err != 0) { /* Seems to be returning >0 for error */
error("Unable to set controlling terminal: %s", strerror(err));
goto out_close;
}
debug("Set the controlling tty");
for (i = 0; i < n_fds; i++) {
err = do_dup2(&child, child_fd, child_tty_fds[i]);
if (err < 0)
error("Problem moving child fd number %d to new tty: %s", child_tty_fds[i], strerror(errno));
}
err = 0;
out_close:
do_syscall(&child, close, child_fd, 0, 0, 0, 0, 0);
out_free_fds:
free(child_tty_fds);
out_unmap:
do_unmap(&child, scratch_page, page_size);
ptrace_restore_regs(&child);
ptrace_detach_child(&child);
if (err == 0) {
kill(child.pid, SIGSTOP);
wait_for_stop(child.pid, statfd);
}
kill(child.pid, SIGWINCH);
out_cont:
kill(child.pid, SIGCONT);
#ifdef __linux__
close(statfd);
#endif
return err < 0 ? -err : err;
}
int attach_child(pid_t pid, const char *pty, int force_stdio) {
struct ptrace_child child;
unsigned long scratch_page = -1;
int *child_tty_fds = NULL, n_fds, child_fd, statfd;
int i;
int err = 0;
long page_size = sysconf(_SC_PAGE_SIZE);
char stat_path[PATH_MAX];
long mmap_syscall;
if ((err = copy_tty_state(pid, pty))) {
if (err == ENOTTY && !force_stdio) {
error("Target is not connected to a terminal.\n"
" Use -s to force attaching anyways.");
return err;
}
}
snprintf(stat_path, sizeof stat_path, "/proc/%d/stat", pid);
statfd = open(stat_path, O_RDONLY);
if (statfd < 0) {
error("Unable to open %s: %s", stat_path, strerror(errno));
return -statfd;
}
kill(pid, SIGTSTP);
wait_for_stop(pid, statfd);
if (ptrace_attach_child(&child, pid)) {
err = child.error;
goto out_cont;
}
if (ptrace_advance_to_state(&child, ptrace_at_syscall)) {
err = child.error;
goto out_detach;
}
if (ptrace_save_regs(&child)) {
err = child.error;
goto out_detach;
}
mmap_syscall = ptrace_syscall_numbers(&child)->nr_mmap2;
if (mmap_syscall == -1)
mmap_syscall = ptrace_syscall_numbers(&child)->nr_mmap;
scratch_page = ptrace_remote_syscall(&child, mmap_syscall, 0,
page_size, PROT_READ|PROT_WRITE,
MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
if (scratch_page > (unsigned long)-1000) {
err = -(signed long)scratch_page;
goto out_unmap;
}
debug("Allocated scratch page: %lx", scratch_page);
if (force_stdio) {
child_tty_fds = malloc(3 * sizeof(int));
if (!child_tty_fds) {
err = ENOMEM;
goto out_unmap;
}
n_fds = 3;
child_tty_fds[0] = 0;
child_tty_fds[1] = 1;
child_tty_fds[2] = 2;
} else {
child_tty_fds = get_child_tty_fds(&child, statfd, &n_fds);
if (!child_tty_fds) {
err = child.error;
goto out_unmap;
}
}
if (ptrace_memcpy_to_child(&child, scratch_page, pty, strlen(pty)+1)) {
err = child.error;
error("Unable to memcpy the pty path to child.");
goto out_free_fds;
}
child_fd = do_syscall(&child, open,
scratch_page, O_RDWR|O_NOCTTY,
0, 0, 0, 0);
if (child_fd < 0) {
err = child_fd;
error("Unable to open the tty in the child.");
goto out_free_fds;
}
debug("Opened the new tty in the child: %d", child_fd);
err = ignore_hup(&child, scratch_page);
if (err < 0)
goto out_close;
err = do_syscall(&child, getsid, 0, 0, 0, 0, 0, 0);
if (err != child.pid) {
debug("Target is not a session leader, attempting to setsid.");
err = do_setsid(&child);
} else {
do_syscall(&child, ioctl, child_tty_fds[0], TIOCNOTTY, 0, 0, 0, 0);
}
if (err < 0)
goto out_close;
err = do_syscall(&child, ioctl, child_fd, TIOCSCTTY, 0, 0, 0, 0);
if (err < 0) {
error("Unable to set controlling terminal.");
goto out_close;
}
debug("Set the controlling tty");
for (i = 0; i < n_fds; i++)
do_syscall(&child, dup2, child_fd, child_tty_fds[i], 0, 0, 0, 0);
err = 0;
out_close:
do_syscall(&child, close, child_fd, 0, 0, 0, 0, 0);
out_free_fds:
free(child_tty_fds);
out_unmap:
do_unmap(&child, scratch_page, page_size);
ptrace_restore_regs(&child);
out_detach:
ptrace_detach_child(&child);
if (err == 0) {
kill(child.pid, SIGSTOP);
wait_for_stop(child.pid, statfd);
}
kill(child.pid, SIGWINCH);
out_cont:
kill(child.pid, SIGCONT);
close(statfd);
return err < 0 ? -err : err;
}