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/* $OpenBSD: sshpty.c,v 1.34 2019/07/04 16:20:10 deraadt Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Allocating a pseudo-terminal, and making it the controlling tty.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*/
#include "includes.h"
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#include <pwd.h>
#include <stdarg.h>
#include <string.h>
#include <termios.h>
#ifdef HAVE_UTIL_H
# include <util.h>
#endif
#include <unistd.h>
#include "sshpty.h"
#include "log.h"
#include "misc.h"
#ifdef HAVE_PTY_H
# include <pty.h>
#endif
#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif
#ifdef __APPLE__
# include <AvailabilityMacros.h>
# if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5)
# define __APPLE_PRIVPTY__
# endif
#endif
/*
* Allocates and opens a pty. Returns 0 if no pty could be allocated, or
* nonzero if a pty was successfully allocated. On success, open file
* descriptors for the pty and tty sides and the name of the tty side are
* returned (the buffer must be able to hold at least 64 characters).
*/
int
pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
{
/* openpty(3) exists in OSF/1 and some other os'es */
char *name;
int i;
i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
if (i == -1) {
error("openpty: %.100s", strerror(errno));
return 0;
}
name = ttyname(*ttyfd);
if (!name)
fatal("openpty returns device for which ttyname fails.");
strlcpy(namebuf, name, namebuflen); /* possible truncation */
return 1;
}
/* Releases the tty. Its ownership is returned to root, and permissions to 0666. */
void
pty_release(const char *tty)
{
#if !defined(__APPLE_PRIVPTY__) && !defined(HAVE_OPENPTY)
if (chown(tty, (uid_t) 0, (gid_t) 0) == -1)
error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno));
if (chmod(tty, (mode_t) 0666) == -1)
error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno));
#endif /* !__APPLE_PRIVPTY__ && !HAVE_OPENPTY */
}
/* Makes the tty the process's controlling tty and sets it to sane modes. */
void
pty_make_controlling_tty(int *ttyfd, const char *tty)
{
int fd;
/* First disconnect from the old controlling tty. */
#ifdef TIOCNOTTY
fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
if (fd >= 0) {
(void) ioctl(fd, TIOCNOTTY, NULL);
close(fd);
}
#endif /* TIOCNOTTY */
if (setsid() == -1)
error("setsid: %.100s", strerror(errno));
/*
* Verify that we are successfully disconnected from the controlling
* tty.
*/
fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
if (fd >= 0) {
error("Failed to disconnect from controlling tty.");
close(fd);
}
/* Make it our controlling tty. */
#ifdef TIOCSCTTY
debug("Setting controlling tty using TIOCSCTTY.");
if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
#endif /* TIOCSCTTY */
#ifdef NEED_SETPGRP
if (setpgrp(0,0) < 0)
error("SETPGRP %s",strerror(errno));
#endif /* NEED_SETPGRP */
fd = open(tty, O_RDWR);
if (fd == -1)
error("%.100s: %.100s", tty, strerror(errno));
else
close(fd);
/* Verify that we now have a controlling tty. */
fd = open(_PATH_TTY, O_WRONLY);
if (fd == -1)
error("open /dev/tty failed - could not set controlling tty: %.100s",
strerror(errno));
else
close(fd);
}
/* Changes the window size associated with the pty. */
void
pty_change_window_size(int ptyfd, u_int row, u_int col,
u_int xpixel, u_int ypixel)
{
struct winsize w;
/* may truncate u_int -> u_short */
w.ws_row = row;
w.ws_col = col;
w.ws_xpixel = xpixel;
w.ws_ypixel = ypixel;
(void) ioctl(ptyfd, TIOCSWINSZ, &w);
}
void
pty_setowner(struct passwd *pw, const char *tty)
{
struct group *grp;
gid_t gid;
mode_t mode;
struct stat st;
/* Determine the group to make the owner of the tty. */
grp = getgrnam("tty");
if (grp == NULL)
debug("%s: no tty group", __func__);
gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid;
mode = (grp != NULL) ? 0620 : 0600;
/*
* Change owner and mode of the tty as required.
* Warn but continue if filesystem is read-only and the uids match/
* tty is owned by root.
*/
if (stat(tty, &st) == -1)
fatal("stat(%.100s) failed: %.100s", tty,
strerror(errno));
#ifdef WITH_SELINUX
ssh_selinux_setup_pty(pw->pw_name, tty);
#endif
if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
if (chown(tty, pw->pw_uid, gid) == -1) {
if (errno == EROFS &&
(st.st_uid == pw->pw_uid || st.st_uid == 0))
debug("chown(%.100s, %u, %u) failed: %.100s",
tty, (u_int)pw->pw_uid, (u_int)gid,
strerror(errno));
else
fatal("chown(%.100s, %u, %u) failed: %.100s",
tty, (u_int)pw->pw_uid, (u_int)gid,
strerror(errno));
}
}
if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
if (chmod(tty, mode) == -1) {
if (errno == EROFS &&
(st.st_mode & (S_IRGRP | S_IROTH)) == 0)
debug("chmod(%.100s, 0%o) failed: %.100s",
tty, (u_int)mode, strerror(errno));
else
fatal("chmod(%.100s, 0%o) failed: %.100s",
tty, (u_int)mode, strerror(errno));
}
}
}
/* Disconnect from the controlling tty. */
void
disconnect_controlling_tty(void)
{
#ifdef TIOCNOTTY
int fd;
if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) {
(void) ioctl(fd, TIOCNOTTY, NULL);
close(fd);
}
#endif /* TIOCNOTTY */
}
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