qbit/xenocara
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
e60da74507
xenocara/xserver/os/privsep.c

362 lines
8.6 KiB
C
Raw Blame History

/* $OpenBSD: privsep.c,v 1.20 2012/06/10 13:21:31 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_DIX_CONFIG_H
#include <dix-config.h>
#endif
#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>
#include "os.h"
enum cmd_types {
PRIV_OPEN_DEVICE,
PRIV_SIG_PARENT,
};
/* Command parameters */
typedef struct priv_cmd {
int cmd;
int _pad;
union {
struct _open {
char path[MAXPATHLEN];
} open;
} arg;
} priv_cmd_t;
static int priv_fd = -1;
static pid_t parent_pid = -1;
struct okdev {
const char *const name;
int flags;
} allowed_devices[] = {
/* Serial devices */
{"/dev/wsmouse", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wsmouse0", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wsmouse1", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wsmouse2", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wsmouse3", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/uhid0", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/uhid1", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/uhid2", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/uhid3", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/tty00", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/tty01", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/tty02", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/tty03", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/tty04", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttya", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyb", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyc", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyd", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wskbd", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wskbd0", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wskbd1", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wskbd2", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/wskbd3", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC0", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC1", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC2", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC3", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC4", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC5", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC6", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyC7", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD0", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD1", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD2", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD3", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD4", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD5", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD6", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/ttyD7", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/pci", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/agp0", O_RDWR | O_NONBLOCK | O_EXCL},
{"/dev/drm0", O_RDWR },
{"/dev/amdmsr", O_RDWR | O_EXCL},
{NULL, 0}
};
/* return 1 if allowed to open said path */
static struct okdev *
open_ok(const char *path)
{
struct okdev *p;
struct stat sb;
for (p = allowed_devices; p->name != NULL; p++) {
if (strcmp(path, p->name) == 0) {
if (stat(path, &sb) < 0) {
/* path is valid, but doesn't exist */
return NULL;
}
if (sb.st_mode & S_IFCHR) {
/* File is a character device */
return p;
}
}
}
/* path is not valid */
return NULL;
}
static void
send_fd(int socket, 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(socket, &msg, 0)) == -1)
warn("%s: sendmsg(%d)", __func__, socket);
if (n != sizeof(int))
warnx("%s: sendmsg: expected sent 1 got %ld",
__func__, (long)n);
}
static int
receive_fd(int socket)
{
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);
do
n = recvmsg(socket, &msg, 0);
while (n == -1 && errno == EINTR);
if (n != sizeof(int)) {
warnx("%s: recvmsg: expected received 1 got %ld",
__func__, (long)n);
return -1;
}
if (result == 0) {
cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg == NULL) {
warnx("%s: no message header", __func__);
return -1;
}
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, fd;
pid_t pid;
int socks[2];
priv_cmd_t cmd;
struct okdev *dev;
parent_pid = getppid();
/* 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 (setgroups(1, &gid) == -1)
return -1;
if (setegid(gid) == -1)
return -1;
if (setgid(gid) == -1)
return -1;
if (seteuid(uid) == -1)
return -1;
if (setuid(uid) == -1)
return -1;
close(socks[0]);
priv_fd = socks[1];
return 0;
}
/* son */
for (i = 1; i <= _NSIG; i++)
signal(i, SIG_DFL);
setproctitle("[priv]");
close(socks[1]);
while (1) {
if (read(socks[0], &cmd, sizeof(cmd)) == 0) {
exit(0);
}
switch (cmd.cmd) {
case PRIV_OPEN_DEVICE:
if ((dev = open_ok(cmd.arg.open.path)) != NULL) {
fd = open(cmd.arg.open.path, dev->flags);
} else {
fd = -1;
errno = EPERM;
}
send_fd(socks[0], fd);
if (fd >= 0)
close(fd);
break;
case PRIV_SIG_PARENT:
kill(parent_pid, SIGUSR1);
break;
default:
errx(1, "%s: unknown command %d", __func__, cmd.cmd);
break;
}
}
_exit(1);
}
/* Open file */
int
priv_open_device(const char *path)
{
priv_cmd_t cmd;
struct okdev *dev;
if (priv_fd != -1) {
cmd.cmd = PRIV_OPEN_DEVICE;
strlcpy(cmd.arg.open.path, path, MAXPATHLEN);
write(priv_fd, &cmd, sizeof(cmd));
return receive_fd(priv_fd);
} else {
if ((dev = open_ok(path)) != NULL)
return open(path, dev->flags);
else {
errno = EPERM;
return -1;
}
}
}
/* send signal to parent process */
int
priv_signal_parent(void)
{
priv_cmd_t cmd;
if (priv_fd != -1) {
if (parent_pid == -1) {
warnx("parent_pid == -1");
return -1;
}
cmd.cmd = PRIV_SIG_PARENT;
write(priv_fd, &cmd, sizeof(cmd));
return 0;
} else
return kill(getppid(), SIGUSR1);
}
#ifdef TEST
/* This is not a complete regression test */
int
main(int argc, char *argv[])
{
int fd;
if (priv_init(getuid(), getgid()) < 0) {
err(1, "priv_init");
}
fd = priv_open_device("/dev/wsmouse");
if (fd < 0) {
err(1, "priv_open_device");
}
write(fd, "test\n", 5);
close(fd);
exit(0);
}
#endif
Reference in New Issue View Git Blame Copy Permalink