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#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 "ptrace.h"
#include "reptyr.h"
#ifdef __NR_mmap2
#define mmap_syscall __NR_mmap2
#else
#define mmap_syscall __NR_mmap
#endif
static void do_unmap(struct ptrace_child *child, child_addr_t addr, unsigned long len) {
if (addr == (unsigned long)-1)
return;
ptrace_remote_syscall(child, __NR_munmap, addr, len, 0, 0, 0, 0);
}
int *get_child_tty_fds(struct ptrace_child *child, int *count) {
char buf[PATH_MAX];
char child_tty[PATH_MAX];
int n = 0, allocated = 0;
int *fds = NULL;
DIR *dir;
ssize_t len;
struct dirent *d;
debug("Looking up fds for tty in child.");
snprintf(buf, sizeof buf, "/proc/%d/fd/0", child->pid);
len = readlink(buf, child_tty, PATH_MAX);
if(len < 0)
return NULL;
child_tty[len] = 0;
debug("Resolved child tty: %s", child_tty);
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);
len = readlink(buf, buf, PATH_MAX);
if (len < 0)
continue;
buf[len] = 0;
if (strcmp(buf, child_tty) == 0
|| strcmp(buf, "/dev/tty") == 0) {
if (n == allocated) {
allocated = allocated ? 2 * allocated : 2;
fds = realloc(fds, sizeof(int) * allocated);
if (!fds)
goto out;
}
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 = ptrace_remote_syscall(child, __NR_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 = ptrace_remote_syscall(child, __NR_fork,
0, 0, 0, 0, 0, 0);
if (err < 0)
return err;
debug("Forked a child: %d", 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 = ptrace_remote_syscall(&dummy, __NR_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 = ptrace_remote_syscall(child, __NR_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);
ptrace_remote_syscall(child, __NR_wait4,
dummy.pid, 0, WNOHANG,
0, 0, 0);
return err;
}
int ignore_hup(struct ptrace_child *child, unsigned long scratch_page) {
int err;
#ifdef __NR_signal
err = ptrace_remote_syscall(child, __NR_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 = ptrace_remote_syscall(child, __NR_rt_sigaction,
SIGHUP, scratch_page,
0, 8, 0, 0);
#endif
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) {
struct timeval start, now;
struct timespec sleep;
char stat_path[PATH_MAX], buf[256], *p;
int fd;
snprintf(stat_path, sizeof stat_path, "/proc/%d/stat", pid);
fd = open(stat_path, O_RDONLY);
if (!fd) {
error("Unable to open %s: %s", stat_path, strerror(errno));
return;
}
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.
*/
lseek(fd, 0, SEEK_SET);
if (read(fd, buf, sizeof buf) <= 0)
break;
p = strchr(buf, ' ');
if (!p)
break;
p = strchr(p+1, ' ');
if (!p)
break;
if (*(p+1) == 'T')
break;
sleep.tv_sec = 0;
sleep.tv_nsec = 10000000;
nanosleep(&sleep, NULL);
}
close(fd);
}
int copy_tty_state(pid_t pid, const char *pty) {
char buf[PATH_MAX];
int fd, err = 0;
struct termios tio;
snprintf(buf, sizeof buf, "/proc/%d/fd/0", pid);
if ((fd = open(buf, O_RDONLY)) < 0)
return -errno;
if (tcgetattr(fd, &tio) < 0) {
err = errno;
goto out;
}
close(fd);
if ((fd = open(pty, O_RDONLY)) < 0)
return -errno;
if (tcsetattr(fd, TCSANOW, &tio) < 0)
err = errno;
out:
close(fd);
return -err;
}
int attach_child(pid_t pid, const char *pty) {
struct ptrace_child child;
unsigned long scratch_page = -1;
int *child_tty_fds = NULL, n_fds, child_fd;
int i;
int err = 0;
long page_size = sysconf(_SC_PAGE_SIZE);
if ((err = copy_tty_state(pid, pty)) < 0)
return -err;
kill(pid, SIGTSTP);
wait_for_stop(pid);
if (ptrace_attach_child(&child, pid)) {
kill(pid, SIGCONT);
return child.error;
}
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;
}
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);
child_tty_fds = get_child_tty_fds(&child, &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 = ptrace_remote_syscall(&child, __NR_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 = ptrace_remote_syscall(&child, __NR_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 {
ptrace_remote_syscall(&child, __NR_ioctl,
child_tty_fds[0], TIOCNOTTY,
0, 0, 0, 0);
}
if (err < 0)
goto out_close;
err = ptrace_remote_syscall(&child, __NR_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++)
ptrace_remote_syscall(&child, __NR_dup2,
child_fd, child_tty_fds[i],
0, 0, 0, 0);
err = 0;
out_close:
ptrace_remote_syscall(&child, __NR_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, SIGCONT);
kill(child.pid, SIGWINCH);
}
return err < 0 ? -err : err;
}
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