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      1 /*	$NetBSD: perm.c,v 1.4 2016/03/13 00:32:09 dholland Exp $	*/
      2 
      3 /*
      4  * perm.c - check user permission for at(1)
      5  * Copyright (C) 1994  Thomas Koenig
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. The name of the author(s) may not be used to endorse or promote
     13  *    products derived from this software without specific prior written
     14  *    permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
     17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     19  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     23  * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 /* System Headers */
     29 
     30 #include <sys/types.h>
     31 #include <errno.h>
     32 #include <pwd.h>
     33 #include <stdbool.h>
     34 #include <stddef.h>
     35 #include <stdio.h>
     36 #include <stdlib.h>
     37 #include <string.h>
     38 #include <unistd.h>
     39 
     40 /* Local headers */
     41 
     42 #include "at.h"
     43 #include "panic.h"
     44 #include "pathnames.h"
     45 #include "privs.h"
     46 #include "perm.h"
     47 
     48 /* File scope variables */
     49 
     50 #ifndef lint
     51 #if 0
     52 static char rcsid[] = "$OpenBSD: perm.c,v 1.1 1997/03/01 23:40:12 millert Exp $";
     53 #else
     54 __RCSID("$NetBSD: perm.c,v 1.4 2016/03/13 00:32:09 dholland Exp $");
     55 #endif
     56 #endif
     57 
     58 /* Local functions */
     59 
     60 static bool
     61 check_for_user(FILE *fp, const char *name)
     62 {
     63 	char *buffer;
     64 	size_t len;
     65 	bool found = false;
     66 
     67 	len = strlen(name);
     68 	if ((buffer = malloc(len + 2)) == NULL)
     69 		panic("Insufficient virtual memory");
     70 
     71 	while (fgets(buffer, (int)len + 2, fp) != NULL) {
     72 		if (strncmp(name, buffer, len) == 0 && buffer[len] == '\n') {
     73 			found = true;
     74 			break;
     75 		}
     76 	}
     77 	(void)fclose(fp);
     78 	free(buffer);
     79 	return found;
     80 }
     81 
     82 /* Global functions */
     83 
     84 bool
     85 check_permission(void)
     86 {
     87 	FILE *fp;
     88 	uid_t uid = geteuid();
     89 	struct passwd *pentry;
     90 
     91 	if (uid == 0)
     92 		return true;
     93 
     94 	if ((pentry = getpwuid(uid)) == NULL) {
     95 		perror("Cannot access user database");
     96 		exit(EXIT_FAILURE);
     97 	}
     98 
     99 	privs_enter();
    100 
    101 	fp = fopen(_PATH_AT_ALLOW, "r");
    102 
    103 	privs_exit();
    104 
    105 	if (fp != NULL) {
    106 		return check_for_user(fp, pentry->pw_name);
    107 	} else {
    108 		privs_enter();
    109 
    110 		fp = fopen(_PATH_AT_DENY, "r");
    111 
    112 		privs_exit();
    113 
    114 		if (fp != NULL)
    115 			return !check_for_user(fp, pentry->pw_name);
    116 	}
    117 	return false;
    118 }
    119