1 /*-
2 * perm.c - check user permission for at(1)
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 *
6 * Copyright (C) 1994 Thomas Koenig
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. The name of the author(s) may not be used to endorse or promote
14 * products derived from this software without specific prior written
15 * permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 /* System Headers */
31
32 #include <sys/types.h>
33 #include <err.h>
34 #include <errno.h>
35 #include <pwd.h>
36 #include <stddef.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <string.h>
40 #include <unistd.h>
41
42 /* Local headers */
43
44 #include "at.h"
45 #include "perm.h"
46 #include "privs.h"
47
48 /* Macros */
49
50 #define MAXUSERID 10
51
52 /* Structures and unions */
53
54 /* Function declarations */
55
56 static int check_for_user(FILE *fp,const char *name);
57
58 /* Local functions */
59
check_for_user(FILE * fp,const char * name)60 static int check_for_user(FILE *fp,const char *name)
61 {
62 char *buffer;
63 size_t len;
64 int found = 0;
65
66 len = strlen(name);
67 if ((buffer = malloc(len+2)) == NULL)
68 errx(EXIT_FAILURE, "virtual memory exhausted");
69
70 while(fgets(buffer, len+2, fp) != NULL)
71 {
72 if ((strncmp(name, buffer, len) == 0) &&
73 (buffer[len] == '\n'))
74 {
75 found = 1;
76 break;
77 }
78 }
79 fclose(fp);
80 free(buffer);
81 return found;
82 }
83 /* Global functions */
check_permission(void)84 int check_permission(void)
85 {
86 FILE *fp;
87 uid_t uid = geteuid();
88 struct passwd *pentry;
89
90 if (uid==0)
91 return 1;
92
93 if ((pentry = getpwuid(uid)) == NULL)
94 err(EXIT_FAILURE, "cannot access user database");
95
96 PRIV_START
97
98 fp=fopen(PERM_PATH "at.allow","r");
99
100 PRIV_END
101
102 if (fp != NULL)
103 {
104 return check_for_user(fp, pentry->pw_name);
105 }
106 else if (errno == ENOENT)
107 {
108
109 PRIV_START
110
111 fp=fopen(PERM_PATH "at.deny", "r");
112
113 PRIV_END
114
115 if (fp != NULL)
116 {
117 return !check_for_user(fp, pentry->pw_name);
118 }
119 else if (errno != ENOENT)
120 warn("at.deny");
121 }
122 else
123 warn("at.allow");
124 return 0;
125 }
126