9bc83c2506f9083e577d8ff36d0c6953dd2d1285
[paraslash.git] / acl.c
1 /*
2 * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file acl.c Access control lists for paraslash senders. */
8
9 #include "para.h"
10 #include "error.h"
11 #include "string.h"
12 #include "list.h"
13 #include "net.h"
14
15 /**
16 * Describes one entry in the blacklist/whitelist of a paraslash sender.
17 */
18 struct access_info {
19 /** The address to be black/whitelisted. */
20 struct in_addr addr;
21 /** The netmask for this entry. */
22 unsigned netmask;
23 /** The position of this entry in the acl. */
24 struct list_head node;
25 };
26
27 /**
28 * Return true if addr_1 matches addr_2 in the first `netmask' bits.
29 */
30 static int v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
31 {
32 uint32_t mask = ~0U;
33
34 if (netmask < 32)
35 mask <<= (32 - netmask);
36 return (htonl(addr_1) & mask) == (htonl(addr_2) & mask);
37 }
38
39 /**
40 * Find out whether the peer name of a given fd belongs to an acl.
41 *
42 * \param fd File descriptor.
43 * \param acl The access control list.
44 *
45 * \return One if \a fd belongs to \a acl, zero otherwise.
46 */
47 static int acl_lookup(int fd, struct list_head *acl)
48 {
49 struct access_info *ai, *tmp;
50 struct sockaddr_storage ss;
51 socklen_t sslen = sizeof(ss);
52 struct in_addr v4_addr;
53
54 if (getpeername(fd, (struct sockaddr *)&ss, &sslen) < 0) {
55 PARA_ERROR_LOG("Can not determine peer address: %s\n", strerror(errno));
56 goto no_match;
57 }
58 v4_addr = extract_v4_addr(&ss);
59 if (!v4_addr.s_addr)
60 goto no_match;
61
62 list_for_each_entry_safe(ai, tmp, acl, node)
63 if (v4_addr_match(v4_addr.s_addr, ai->addr.s_addr, ai->netmask))
64 return 1;
65 no_match:
66 return 0;
67 }
68
69 /**
70 * Add an entry to an access control list.
71 *
72 * \param acl The access control list.
73 * \param addr The address to add.
74 * \param netmask The netmask to use for this entry.
75 */
76 static void acl_add_entry(struct list_head *acl, char *addr, int netmask)
77 {
78 struct access_info *ai = para_malloc(sizeof(struct access_info));
79
80 inet_pton(AF_INET, addr, &ai->addr);
81 ai->netmask = netmask;
82 PARA_INFO_LOG("adding %s/%i to access list\n", addr, ai->netmask);
83 para_list_add(&ai->node, acl);
84 }
85
86 /**
87 * Delete an entry from an access control list.
88 *
89 * \param acl The access control list.
90 * \param addr The address to delete.
91 * \param netmask The netmask of the entry to be removed from the list.
92 */
93 static void acl_del_entry(struct list_head *acl, char *addr, int netmask)
94 {
95 struct access_info *ai, *tmp;
96
97 list_for_each_entry_safe(ai, tmp, acl, node) {
98 if (!strcmp(addr, inet_ntoa(ai->addr)) &&
99 ai->netmask == netmask) {
100 PARA_NOTICE_LOG("removing %s/%i from access list\n",
101 addr, ai->netmask);
102 list_del(&ai->node);
103 free(ai);
104 }
105 }
106 }
107
108 /**
109 * Compute a string containing the contents of an acl.
110 *
111 * \param acl The access control list.
112 *
113 * \return A string containing the contents of \a acl, or \p NULL
114 * if \a acl is empty.
115 */
116 char *acl_get_contents(struct list_head *acl)
117 {
118 struct access_info *ai, *tmp_ai;
119 char *ret = NULL;
120
121 list_for_each_entry_safe(ai, tmp_ai, acl, node) {
122 char *tmp = make_message("%s%s/%d ", ret? ret : "",
123 inet_ntoa(ai->addr), ai->netmask);
124 free(ret);
125 ret = tmp;
126 }
127 return ret;
128 }
129
130 /**
131 * Initialize an access control list.
132 *
133 * \param acl The list to initialize.
134 * \param acl_info An array of strings of the form ip/netmask.
135 * \param num The number of strings in \a acl_info.
136 */
137 void acl_init(struct list_head *acl, char * const *acl_info, int num)
138 {
139 char addr[16];
140 int mask, i;
141
142 INIT_LIST_HEAD(acl);
143 for (i = 0; i < num; i++)
144 if (parse_cidr(acl_info[i], addr, sizeof(addr), &mask) == NULL)
145 PARA_CRIT_LOG("ACL syntax error: %s, ignoring\n",
146 acl_info[i]);
147 else
148 acl_add_entry(acl, addr, mask);
149 }
150
151 /**
152 * Check whether the peer name of a given fd is allowed by an acl.
153 *
154 * \param fd File descriptor.
155 * \param acl The access control list.
156 * \param default_deny Whether \a acl is a whitelist.
157 *
158 * \return Positive if the peer of \a fd is permitted by \a acl, \p -E_ACL_PERM
159 * otherwise.
160 */
161 int acl_check_access(int fd, struct list_head *acl, int default_deny)
162 {
163 int match = acl_lookup(fd, acl);
164
165 return (!match || default_deny) && (match || !default_deny)?
166 1 : -E_ACL_PERM;
167 }
168
169 /**
170 * Permit access for a range of IP addresses.
171 *
172 * \param addr The address to permit.
173 * \param netmask The netmask of the entry to be permitted.
174 * \param acl The access control list.
175 * \param default_deny Whether \a acl is a whitelist.
176 */
177 void acl_allow(char *addr, int netmask,
178 struct list_head *acl, int default_deny)
179 {
180 if (default_deny)
181 acl_add_entry(acl, addr, netmask);
182 else
183 acl_del_entry(acl, addr, netmask);
184 }
185
186 /**
187 * Deny access for a range of IP addresses.
188 *
189 * \param addr The address to deny.
190 * \param netmask The netmask of the entry to be denied.
191 * \param acl The access control list.
192 * \param default_deny Whether \a acl is a whitelist.
193 */
194 void acl_deny(char *addr, int netmask,
195 struct list_head *acl, int default_deny)
196 {
197 acl_allow(addr, netmask, acl, !default_deny);
198 }