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/*
* Copyright (C) 2011 by Nelson Elhage
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <sys/types.h>
#include <dirent.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <signal.h>
#include <limits.h>
#include <time.h>
#include <sys/time.h>
#include <sys/stat.h>
#include "ptrace.h"
#include "reptyr.h"
#define TASK_COMM_LENGTH 16
struct proc_stat {
pid_t pid;
char comm[TASK_COMM_LENGTH+1];
char state;
pid_t ppid, sid, pgid;
dev_t ctty;
};
#define do_syscall(child, name, a0, a1, a2, a3, a4, a5) \
ptrace_remote_syscall((child), ptrace_syscall_numbers((child))->nr_##name, \
a0, a1, a2, a3, a4, a5)
int parse_proc_stat(int statfd, struct proc_stat *out) {
char buf[1024];
int n;
unsigned dev;
lseek(statfd, 0, SEEK_SET);
if (read(statfd, buf, sizeof buf) < 0)
return errno;
n = sscanf(buf, "%d (%16[^)]) %c %d %d %d %u",
&out->pid, out->comm,
&out->state, &out->ppid, &out->sid,
&out->pgid, &dev);
if (n == EOF)
return errno;
if (n != 7) {
return EINVAL;
}
out->ctty = dev;
return 0;
}
static void do_unmap(struct ptrace_child *child, child_addr_t addr, unsigned long len) {
if (addr == (unsigned long)-1)
return;
do_syscall(child, munmap, addr, len, 0, 0, 0, 0);
}
int *get_child_tty_fds(struct ptrace_child *child, int statfd, int *count) {
struct proc_stat child_status;
struct stat tty_st, st;
char buf[PATH_MAX];
int n = 0, allocated = 0;
int *fds = NULL;
DIR *dir;
struct dirent *d;
int *tmp = NULL;
debug("Looking up fds for tty in child.");
if ((child->error = parse_proc_stat(statfd, &child_status)))
return NULL;
debug("Resolved child tty: %x", (unsigned)child_status.ctty);
if (stat("/dev/tty", &tty_st) < 0) {
child->error = errno;
error("Unable to stat /dev/tty");
return NULL;
}
snprintf(buf, sizeof buf, "/proc/%d/fd/", child->pid);
if ((dir = opendir(buf)) == NULL)
return NULL;
while ((d = readdir(dir)) != NULL) {
if (d->d_name[0] == '.') continue;
snprintf(buf, sizeof buf, "/proc/%d/fd/%s", child->pid, d->d_name);
if (stat(buf, &st) < 0)
continue;
if (st.st_rdev == child_status.ctty
|| st.st_rdev == tty_st.st_rdev) {
if (n == allocated) {
allocated = allocated ? 2 * allocated : 2;
tmp = realloc(fds, allocated * sizeof *tmp);
if (tmp == NULL) {
child->error = errno;
error("Unable to allocate memory for fd array.");
free(fds);
fds = NULL;
goto out;
}
fds = tmp;
}
debug("Found an alias for the tty: %s", d->d_name);
fds[n++] = atoi(d->d_name);
}
}
out:
*count = n;
closedir(dir);
return fds;
}
void move_process_group(struct ptrace_child *child, pid_t from, pid_t to) {
DIR *dir;
struct dirent *d;
pid_t pid;
char *p;
int err;
if ((dir = opendir("/proc/")) == NULL)
return;
while ((d = readdir(dir)) != NULL) {
if (d->d_name[0] == '.') continue;
pid = strtol(d->d_name, &p, 10);
if (*p) continue;
if (getpgid(pid) == from) {
debug("Change pgid for pid %d", pid);
err = do_syscall(child, setpgid, pid, to, 0, 0, 0, 0);
if (err < 0)
error(" failed: %s", strerror(-err));
}
}
closedir(dir);
}
int do_setsid(struct ptrace_child *child) {
int err = 0;
struct ptrace_child dummy;
err = do_syscall(child, fork, 0, 0, 0, 0, 0, 0);
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;
memcpy(&dummy.user, &child->user, sizeof child->user);
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_detach_child(&dummy);
ptrace_wait(&dummy);
do_syscall(child, wait4, dummy.pid, 0, WNOHANG, 0, 0, 0);
return err;
}
int ignore_hup(struct ptrace_child *child, unsigned long scratch_page) {
int err;
if (ptrace_syscall_numbers(child)->nr_signal != -1) {
err = do_syscall(child, signal, SIGHUP, (unsigned long)SIG_IGN, 0, 0, 0, 0);
} else {
struct sigaction act = {
.sa_handler = SIG_IGN,
};
err = ptrace_memcpy_to_child(child, scratch_page,
&act, sizeof act);
if (err < 0)
return err;
err = do_syscall(child, rt_sigaction,
SIGHUP, scratch_page,
0, 8, 0, 0);
}
return err;
}
/*
* Wait for the specific pid to enter state 'T', or stopped. We have to pull the
* /proc file rather than attaching with ptrace() and doing a wait() because
* half the point of this exercise is for the process's real parent (the shell)
* to see the TSTP.
*
* In case the process is masking or ignoring SIGTSTP, we time out after a
* second and continue with the attach -- it'll still work mostly right, you
* just won't get the old shell back.
*/
void wait_for_stop(pid_t pid, int fd) {
struct timeval start, now;
struct timespec sleep;
struct proc_stat st;
gettimeofday(&start, NULL);
while (1) {
gettimeofday(&now, NULL);
if ((now.tv_sec > start.tv_sec && now.tv_usec > start.tv_usec)
|| (now.tv_sec - start.tv_sec > 1)) {
error("Timed out waiting for child stop.");
break;
}
/*
* If anything goes wrong reading or parsing the stat node, just give
* up.
*/
if (parse_proc_stat(fd, &st))
break;
if (st.state == 'T')
break;
sleep.tv_sec = 0;
sleep.tv_nsec = 10000000;
nanosleep(&sleep, NULL);
}
}
int copy_tty_state(pid_t pid, const char *pty) {
char buf[PATH_MAX];
int fd, err = 0;
struct termios tio;
int i;
for (i = 0; i < 3; i++) {
err = 0;
snprintf(buf, sizeof buf, "/proc/%d/fd/%d", pid, i);
if ((fd = open(buf, O_RDONLY)) < 0) {
err = -fd;
continue;
}
if (!isatty(fd)) {
err = ENOTTY;
goto retry;
}
if (tcgetattr(fd, &tio) < 0) {
err = -errno;
}
retry:
close(fd);
}
if (err)
return err;
if ((fd = open(pty, O_RDONLY)) < 0)
return -errno;
if (tcsetattr(fd, TCSANOW, &tio) < 0)
err = errno;
close(fd);
return -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;
}
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