1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Network port table
4 *
5 * SELinux must keep a mapping of network ports to labels/SIDs.  This
6 * mapping is maintained as part of the normal policy but a fast cache is
7 * needed to reduce the lookup overhead.
8 *
9 * Author: Paul Moore <paul@paul-moore.com>
10 *
11 * This code is heavily based on the "netif" concept originally developed by
12 * James Morris <jmorris@redhat.com>
13 *   (see security/selinux/netif.c for more information)
14 */
15
16/*
17 * (c) Copyright Hewlett-Packard Development Company, L.P., 2008
18 */
19
20#include <linux/types.h>
21#include <linux/rcupdate.h>
22#include <linux/list.h>
23#include <linux/slab.h>
24#include <linux/spinlock.h>
25#include <linux/in.h>
26#include <linux/in6.h>
27#include <linux/ip.h>
28#include <linux/ipv6.h>
29#include <net/ip.h>
30#include <net/ipv6.h>
31
32#include "netport.h"
33#include "objsec.h"
34
35#define SEL_NETPORT_HASH_SIZE       256
36#define SEL_NETPORT_HASH_BKT_LIMIT   16
37
38struct sel_netport_bkt {
39	int size;
40	struct list_head list;
41};
42
43struct sel_netport {
44	struct netport_security_struct psec;
45
46	struct list_head list;
47	struct rcu_head rcu;
48};
49
50/* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
51 * for this is that I suspect most users will not make heavy use of both
52 * address families at the same time so one table will usually end up wasted,
53 * if this becomes a problem we can always add a hash table for each address
54 * family later */
55
56static DEFINE_SPINLOCK(sel_netport_lock);
57static struct sel_netport_bkt sel_netport_hash[SEL_NETPORT_HASH_SIZE];
58
59/**
60 * sel_netport_hashfn - Hashing function for the port table
61 * @pnum: port number
62 *
63 * Description:
64 * This is the hashing function for the port table, it returns the bucket
65 * number for the given port.
66 *
67 */
68static unsigned int sel_netport_hashfn(u16 pnum)
69{
70	return (pnum & (SEL_NETPORT_HASH_SIZE - 1));
71}
72
73/**
74 * sel_netport_find - Search for a port record
75 * @protocol: protocol
76 * @pnum: port
77 *
78 * Description:
79 * Search the network port table and return the matching record.  If an entry
80 * can not be found in the table return NULL.
81 *
82 */
83static struct sel_netport *sel_netport_find(u8 protocol, u16 pnum)
84{
85	unsigned int idx;
86	struct sel_netport *port;
87
88	idx = sel_netport_hashfn(pnum);
89	list_for_each_entry_rcu(port, &sel_netport_hash[idx].list, list)
90		if (port->psec.port == pnum && port->psec.protocol == protocol)
91			return port;
92
93	return NULL;
94}
95
96/**
97 * sel_netport_insert - Insert a new port into the table
98 * @port: the new port record
99 *
100 * Description:
101 * Add a new port record to the network address hash table.
102 *
103 */
104static void sel_netport_insert(struct sel_netport *port)
105{
106	unsigned int idx;
107
108	/* we need to impose a limit on the growth of the hash table so check
109	 * this bucket to make sure it is within the specified bounds */
110	idx = sel_netport_hashfn(port->psec.port);
111	list_add_rcu(&port->list, &sel_netport_hash[idx].list);
112	if (sel_netport_hash[idx].size == SEL_NETPORT_HASH_BKT_LIMIT) {
113		struct sel_netport *tail;
114		tail = list_entry(
115			rcu_dereference_protected(
116				list_tail_rcu(&sel_netport_hash[idx].list),
117				lockdep_is_held(&sel_netport_lock)),
118			struct sel_netport, list);
119		list_del_rcu(&tail->list);
120		kfree_rcu(tail, rcu);
121	} else
122		sel_netport_hash[idx].size++;
123}
124
125/**
126 * sel_netport_sid_slow - Lookup the SID of a network address using the policy
127 * @protocol: protocol
128 * @pnum: port
129 * @sid: port SID
130 *
131 * Description:
132 * This function determines the SID of a network port by querying the security
133 * policy.  The result is added to the network port table to speedup future
134 * queries.  Returns zero on success, negative values on failure.
135 *
136 */
137static int sel_netport_sid_slow(u8 protocol, u16 pnum, u32 *sid)
138{
139	int ret;
140	struct sel_netport *port;
141	struct sel_netport *new;
142
143	spin_lock_bh(&sel_netport_lock);
144	port = sel_netport_find(protocol, pnum);
145	if (port != NULL) {
146		*sid = port->psec.sid;
147		spin_unlock_bh(&sel_netport_lock);
148		return 0;
149	}
150
151	ret = security_port_sid(protocol, pnum, sid);
152	if (ret != 0)
153		goto out;
154	new = kzalloc(sizeof(*new), GFP_ATOMIC);
155	if (new) {
156		new->psec.port = pnum;
157		new->psec.protocol = protocol;
158		new->psec.sid = *sid;
159		sel_netport_insert(new);
160	}
161
162out:
163	spin_unlock_bh(&sel_netport_lock);
164	if (unlikely(ret))
165		pr_warn("SELinux: failure in %s(), unable to determine network port label\n",
166			__func__);
167	return ret;
168}
169
170/**
171 * sel_netport_sid - Lookup the SID of a network port
172 * @protocol: protocol
173 * @pnum: port
174 * @sid: port SID
175 *
176 * Description:
177 * This function determines the SID of a network port using the fastest method
178 * possible.  First the port table is queried, but if an entry can't be found
179 * then the policy is queried and the result is added to the table to speedup
180 * future queries.  Returns zero on success, negative values on failure.
181 *
182 */
183int sel_netport_sid(u8 protocol, u16 pnum, u32 *sid)
184{
185	struct sel_netport *port;
186
187	rcu_read_lock();
188	port = sel_netport_find(protocol, pnum);
189	if (port != NULL) {
190		*sid = port->psec.sid;
191		rcu_read_unlock();
192		return 0;
193	}
194	rcu_read_unlock();
195
196	return sel_netport_sid_slow(protocol, pnum, sid);
197}
198
199/**
200 * sel_netport_flush - Flush the entire network port table
201 *
202 * Description:
203 * Remove all entries from the network address table.
204 *
205 */
206void sel_netport_flush(void)
207{
208	unsigned int idx;
209	struct sel_netport *port, *port_tmp;
210
211	spin_lock_bh(&sel_netport_lock);
212	for (idx = 0; idx < SEL_NETPORT_HASH_SIZE; idx++) {
213		list_for_each_entry_safe(port, port_tmp,
214					 &sel_netport_hash[idx].list, list) {
215			list_del_rcu(&port->list);
216			kfree_rcu(port, rcu);
217		}
218		sel_netport_hash[idx].size = 0;
219	}
220	spin_unlock_bh(&sel_netport_lock);
221}
222
223static __init int sel_netport_init(void)
224{
225	int iter;
226
227	if (!selinux_enabled_boot)
228		return 0;
229
230	for (iter = 0; iter < SEL_NETPORT_HASH_SIZE; iter++) {
231		INIT_LIST_HEAD(&sel_netport_hash[iter].list);
232		sel_netport_hash[iter].size = 0;
233	}
234
235	return 0;
236}
237
238__initcall(sel_netport_init);
239