xref: /openbmc/linux/security/selinux/netport.c (revision e67b7985)
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 
38 struct sel_netport_bkt {
39 	int size;
40 	struct list_head list;
41 };
42 
43 struct 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 
56 static DEFINE_SPINLOCK(sel_netport_lock);
57 static 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  */
sel_netport_hashfn(u16 pnum)68 static 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  */
sel_netport_find(u8 protocol,u16 pnum)83 static 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  */
sel_netport_insert(struct sel_netport * port)104 static 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  */
sel_netport_sid_slow(u8 protocol,u16 pnum,u32 * sid)137 static 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 
162 out:
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  */
sel_netport_sid(u8 protocol,u16 pnum,u32 * sid)183 int 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  */
sel_netport_flush(void)206 void 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 
sel_netport_init(void)223 static __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