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/* $OpenBSD: privsep.c,v 1.7 2015/11/14 17:12:14 matthieu Exp $ */
/*
* Copyright 2001 Niels Provos <provos@citi.umich.edu>
* All rights reserved.
*
* Copyright (c) 2002 Matthieu Herrb
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <sys/ioctl.h>
#include <sys/param.h>
#include <sys/uio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_UTIL_H
#include <util.h>
#endif
#ifdef HAVE_PTY_H
#inlude <pty.h>
#endif
#include "xconsole.h"
enum cmd_types {
PRIV_OPEN_PTY,
PRIV_REDIRECT_CONSOLE,
};
static int priv_fd = -1;
static void
send_fd(int s, int fd)
{
struct msghdr msg;
union {
struct cmsghdr hdr;
char buf[CMSG_SPACE(sizeof(int))];
} cmsgbuf;
struct cmsghdr *cmsg;
struct iovec vec;
int result = 0;
ssize_t n;
memset(&msg, 0, sizeof(msg));
if (fd >= 0) {
msg.msg_control = &cmsgbuf.buf;
msg.msg_controllen = sizeof(cmsgbuf.buf);
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
*(int *)CMSG_DATA(cmsg) = fd;
} else {
result = errno;
}
vec.iov_base = &result;
vec.iov_len = sizeof(int);
msg.msg_iov = &vec;
msg.msg_iovlen = 1;
if ((n = sendmsg(s, &msg, 0)) == -1)
warn("%s: sendmsg(%d)", __func__, s);
if (n != sizeof(int))
warnx("%s: sendmsg: expected sent 1 got %ld",
__func__, (long)n);
}
static int
receive_fd(int s)
{
struct msghdr msg;
union {
struct cmsghdr hdr;
char buf[CMSG_SPACE(sizeof(int))];
} cmsgbuf;
struct cmsghdr *cmsg;
struct iovec vec;
ssize_t n;
int result;
int fd;
memset(&msg, 0, sizeof(msg));
vec.iov_base = &result;
vec.iov_len = sizeof(int);
msg.msg_iov = &vec;
msg.msg_iovlen = 1;
msg.msg_control = &cmsgbuf.buf;
msg.msg_controllen = sizeof(cmsgbuf.buf);
if ((n = recvmsg(s, &msg, 0)) == -1)
warn("%s: recvmsg", __func__);
if (n != sizeof(int))
warnx("%s: recvmsg: expected received 1 got %ld",
__func__, (long)n);
if (result == 0) {
cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg->cmsg_type != SCM_RIGHTS)
warnx("%s: expected type %d got %d", __func__,
SCM_RIGHTS, cmsg->cmsg_type);
fd = (*(int *)CMSG_DATA(cmsg));
return fd;
} else {
errno = result;
return -1;
}
}
int
priv_init(uid_t uid, gid_t gid)
{
int i, on, result, fd;
int pty, tty;
pid_t pid;
int socks[2];
int cmd;
/* Create sockets */
if (socketpair(AF_LOCAL, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
return -1;
}
pid = fork();
if (pid < 0) {
/* can't fork */
return -1;
}
if (pid != 0) {
/* Father - drop privileges and return */
if (uid != -1 && gid != -1) {
if (setgroups(1, &gid) == -1)
return -1;
if (setresgid(gid, gid, gid) == -1)
return -1;
if (setresuid(uid, uid, uid) == -1)
return -1;
}
close(socks[0]);
priv_fd = socks[1];
return 0;
}
/* son */
for (i = 1; i <= _NSIG; i++)
signal(i, SIG_DFL);
#ifdef HAVE_SETPROCTILE
setproctitle("[priv]");
#endif
close(socks[1]);
while (1) {
if (read(socks[0], &cmd, sizeof(int)) == 0) {
exit(0);
}
switch (cmd) {
case PRIV_OPEN_PTY:
if (openpty(&pty, &tty, NULL, NULL, NULL) == -1) {
warn("%s: openpty", __func__);
pty = -1;
tty = -1;
}
send_fd(socks[0], pty);
send_fd(socks[0], tty);
if (pty != -1)
close(pty);
if (tty != -1)
close(tty);
break;
case PRIV_REDIRECT_CONSOLE:
on = 1;
fd = receive_fd(socks[0]);
result = ioctl(fd, TIOCCONS, (char *) &on);
if (result < 0) {
warn("%s: ioctl(TIOCCONS)", __func__);
}
write(socks[0], &result, sizeof(int));
close(fd);
break;
default:
errx(1, "%s: unknown command %d", __func__, cmd);
break;
}
}
_exit(1);
}
/* Open pseudo-tty */
int
priv_openpty(int *pty_ptr, int *tty_ptr)
{
int cmd;
int pty, tty;
if (priv_fd != -1) {
cmd = PRIV_OPEN_PTY;
write(priv_fd, &cmd, sizeof(int));
pty = receive_fd(priv_fd);
tty = receive_fd(priv_fd);
if (tty < 0 || pty < 0) {
fprintf(stderr, "openpty: %d %d %d\n",
pty, tty, errno);
return -1;
}
if (pty_ptr != NULL)
*pty_ptr = pty;
if (tty_ptr != NULL)
*tty_ptr = tty;
return 0;
} else
return openpty(pty_ptr, tty_ptr, NULL, NULL, NULL);
}
/* Redirect console output */
int
priv_set_console(int fd)
{
int cmd;
int on, result;
if (priv_fd != -1) {
cmd = PRIV_REDIRECT_CONSOLE;
write(priv_fd, &cmd, sizeof(int));
send_fd(priv_fd, fd);
read(priv_fd, &result, sizeof(int));
return result;
} else {
on = 1;
return ioctl(fd, TIOCCONS, &on);
}
}
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