/*      $NetBSD: perm.c,v 1.4 2016/03/13 00:32:09 dholland Exp $        */

/*
* perm.c - check user permission for at(1)
* Copyright (C) 1994  Thomas Koenig
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. The name of the author(s) may not be used to endorse or promote
*    products derived from this software without specific prior written
*    permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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 AUTHOR(S) 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, WETHER 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.
*/

/* System Headers */

#include <sys/types.h>
#include <errno.h>
#include <pwd.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/* Local headers */

#include "at.h"
#include "panic.h"
#include "pathnames.h"
#include "privs.h"
#include "perm.h"

/* File scope variables */

#ifndef lint
#if 0
static char rcsid[] = "$OpenBSD: perm.c,v 1.1 1997/03/01 23:40:12 millert Exp $";
#else
__RCSID("$NetBSD: perm.c,v 1.4 2016/03/13 00:32:09 dholland Exp $");
#endif
#endif

/* Local functions */

static bool
check_for_user(FILE *fp, const char *name)
{
       char *buffer;
       size_t len;
       bool found = false;

       len = strlen(name);
       if ((buffer = malloc(len + 2)) == NULL)
               panic("Insufficient virtual memory");

       while (fgets(buffer, (int)len + 2, fp) != NULL) {
               if (strncmp(name, buffer, len) == 0 && buffer[len] == '\n') {
                       found = true;
                       break;
               }
       }
       (void)fclose(fp);
       free(buffer);
       return found;
}

/* Global functions */

bool
check_permission(void)
{
       FILE *fp;
       uid_t uid = geteuid();
       struct passwd *pentry;

       if (uid == 0)
               return true;

       if ((pentry = getpwuid(uid)) == NULL) {
               perror("Cannot access user database");
               exit(EXIT_FAILURE);
       }

       privs_enter();

       fp = fopen(_PATH_AT_ALLOW, "r");

       privs_exit();

       if (fp != NULL) {
               return check_for_user(fp, pentry->pw_name);
       } else {
               privs_enter();

               fp = fopen(_PATH_AT_DENY, "r");

               privs_exit();

               if (fp != NULL)
                       return !check_for_user(fp, pentry->pw_name);
       }
       return false;
}