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/*
* Copyright © 2014 Red Hat, Inc.
*
* 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 (including the next
* paragraph) 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.
*
* Author: Hans de Goede <hdegoede@redhat.com>
*/
#include "dix-config.h"
#include <fcntl.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <drm/drm.h>
#include <xf86drm.h> /* For DRM_DEV_NAME */
#define CONFIG_FILE SYSCONFDIR "/X11/Xwrapper.config"
enum { ROOT_ONLY, CONSOLE_ONLY, ANYBODY };
/* KISS non locale / LANG parsing isspace version */
static int is_space(char c)
{
return c == ' ' || c == '\t' || c == '\n';
}
static char *strip(char *s)
{
int i;
/* Strip leading whitespace */
while (s[0] && is_space(s[0]))
s++;
/* Strip trailing whitespace */
i = strlen(s) - 1;
while (i >= 0 && is_space(s[i])) {
s[i] = 0;
i--;
}
return s;
}
static void parse_config(int *allowed, int *needs_root_rights)
{
FILE *f;
char buf[1024];
char *stripped, *equals, *key, *value;
int line = 0;
f = fopen(CONFIG_FILE, "r");
if (!f)
return;
while (fgets(buf, sizeof(buf), f)) {
line++;
/* Skip comments and empty lines */
stripped = strip(buf);
if (stripped[0] == '#' || stripped[0] == 0)
continue;
/* Split in a key + value pair */
equals = strchr(stripped, '=');
if (!equals) {
fprintf(stderr, "Syntax error at %s line %d\n", CONFIG_FILE, line);
exit(1);
}
*equals = 0;
key = strip(stripped); /* To remove trailing whitespace from key */
value = strip(equals + 1); /* To remove leading whitespace from val */
if (!key[0]) {
fprintf(stderr, "Missing key at %s line %d\n", CONFIG_FILE, line);
exit(1);
}
if (!value[0]) {
fprintf(stderr, "Missing value at %s line %d\n", CONFIG_FILE, line);
exit(1);
}
/* And finally process */
if (strcmp(key, "allowed_users") == 0) {
if (strcmp(value, "rootonly") == 0)
*allowed = ROOT_ONLY;
else if (strcmp(value, "console") == 0)
*allowed = CONSOLE_ONLY;
else if (strcmp(value, "anybody") == 0)
*allowed = ANYBODY;
else {
fprintf(stderr,
"Invalid value '%s' for 'allowed_users' at %s line %d\n",
value, CONFIG_FILE, line);
exit(1);
}
}
else if (strcmp(key, "needs_root_rights") == 0) {
if (strcmp(value, "yes") == 0)
*needs_root_rights = 1;
else if (strcmp(value, "no") == 0)
*needs_root_rights = 0;
else if (strcmp(value, "auto") == 0)
*needs_root_rights = -1;
else {
fprintf(stderr,
"Invalid value '%s' for 'needs_root_rights' at %s line %d\n",
value, CONFIG_FILE, line);
exit(1);
}
}
else if (strcmp(key, "nice_value") == 0) {
/* Backward compatibility with older Debian Xwrapper, ignore */
}
else {
fprintf(stderr, "Invalid key '%s' at %s line %d\n", key,
CONFIG_FILE, line);
exit(1);
}
}
fclose(f);
}
int main(int argc, char *argv[])
{
struct drm_mode_card_res res;
struct stat st;
char buf[PATH_MAX];
int i, r, fd;
int kms_cards = 0;
int total_cards = 0;
int allowed = CONSOLE_ONLY;
int needs_root_rights = -1;
parse_config(&allowed, &needs_root_rights);
/* For non root users check if they are allowed to run the X server */
if (getuid() != 0) {
switch (allowed) {
case ROOT_ONLY:
/* Already checked above */
fprintf(stderr, "%s: Only root is allowed to run the X server\n", argv[0]);
exit(1);
break;
case CONSOLE_ONLY:
/* Some of stdin / stdout / stderr maybe redirected to a file */
for (i = STDIN_FILENO; i <= STDERR_FILENO; i++) {
r = fstat(i, &st);
if (r == 0 && S_ISCHR(st.st_mode) && major(st.st_rdev) == 4)
break;
}
if (i > STDERR_FILENO) {
fprintf(stderr, "%s: Only console users are allowed to run the X server\n", argv[0]);
exit(1);
}
break;
case ANYBODY:
break;
}
}
/* Detect if we need root rights, except when overriden by the config */
if (needs_root_rights == -1) {
for (i = 0; i < 16; i++) {
snprintf(buf, sizeof(buf), DRM_DEV_NAME, DRM_DIR_NAME, i);
fd = open(buf, O_RDWR);
if (fd == -1)
continue;
total_cards++;
memset(&res, 0, sizeof(struct drm_mode_card_res));
r = ioctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res);
if (r == 0 && res.count_connectors > 0)
kms_cards++;
close(fd);
}
}
/* If we've found cards, and all cards support kms, drop root rights */
if (needs_root_rights == 0 || (total_cards && kms_cards == total_cards)) {
gid_t realgid = getgid();
uid_t realuid = getuid();
if (setresgid(-1, realgid, realgid) != 0) {
perror("Could not drop setgid privileges");
exit(1);
}
if (setresuid(-1, realuid, realuid) != 0) {
perror("Could not drop setuid privileges");
exit(1);
}
}
snprintf(buf, sizeof(buf), "%s/Xorg.bin", SUID_WRAPPER_DIR);
/* Check if the server is executable by our real uid */
if (access(buf, X_OK) != 0) {
perror("Missing execute permissions for " SUID_WRAPPER_DIR "Xorg.bin");
exit(1);
}
argv[0] = buf;
(void) execv(argv[0], argv);
perror("Failed to execute " SUID_WRAPPER_DIR "/Xorg.bin");
exit(1);
}
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