/**
* mds — A micro-display server
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "mds.h"
#include "config.h"
#include <sys/stat.h>
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <limits.h>
#include <fcntl.h>
/**
* Entry point of the program
*
* @param argc Number of elements in `argv`
* @param argv Command line arguments
* @return Non-zero on error
*/
int main(int argc, const char** argv)
{
char pathname[PATH_MAX];
unsigned int display;
FILE *f;
int fd;
(void) argv;
/* Sanity check the number of command line arguments. */
if (argc > ARGC_LIMIT)
{
fprintf(stderr,
"%s: that number of arguments is ridiculous, I will not allow it.\n",
*argv);
return 1;
}
/* Stymied if the effective user is not root. */
if (geteuid() != ROOT_USER_UID)
{
fprintf(stderr,
"%s: the effective user is not root, cannot continue.\n",
*argv);
return 1;
}
/* Create directory for socket files, PID files and such. */
if (create_runtime_root_directory())
return 1;
/* Determine display index. */
for (display = 0; display < DISPLAY_MAX; display++)
{
snprintf(pathname, sizeof(pathname) / sizeof(char), "%s/%u.pid",
MDS_RUNTIME_ROOT_DIRECTORY, display);
fd = open(pathname, O_CREAT | O_EXCL);
if (fd == -1)
{
/* TODO reuse display index not no longer used */
continue;
}
close(fd);
}
if (display == DISPLAY_MAX)
{
fprintf(stderr,
"%s: Sorry, too many displays on the system.\n",
*argv);
return 1;
/* Yes, the directory could have been removed, but probably not. */
}
/* TODO: Create PID file. */
/* TODO: Save MDS_DISPLAY environment variable. */
/* Drop privileges. They most not be propagated non-authorised components. */
/* setgid should not be set, but just to be safe we are restoring both user and group. */
if ((seteuid(getuid()) < 0) || (setegid(getgid()) < 0))
{
perror(*argv);
return 1;
}
return 0;
}
/**
* Create directory for socket files, PID files and such
*
* @return Non-zero on error
*/
int create_runtime_root_directory(void)
{
struct stat attr;
if (stat(MDS_RUNTIME_ROOT_DIRECTORY, &attr) == 0)
{
/* Cannot create the directory, its pathname refers to an existing. */
if (S_ISDIR(attr.st_mode) == 0)
{
/* But it is not a directory so we cannot continue. */
fprintf(stderr,
"%s: %s already exists but is not a directory.\n",
MDS_RUNTIME_ROOT_DIRECTORY, *argv);
return 1;
}
}
else
{
/* Directory is missing, create it. */
if (mkdir(MDS_RUNTIME_ROOT_DIRECTORY, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) < 0)
{
if (errno != EEXIST) /* Unlikely race condition. */
{
perror(*argv);
return 1;
}
}
else
/* Set ownership. */
if (chown(MDS_RUNTIME_ROOT_DIRECTORY, ROOT_USER_UID, ROOT_GROUP_GID) < 0)
{
perror(*argv);
return 1;
}
}
return 0;
}
