xref: /openbmc/linux/security/lsm_audit.c (revision 84d517f3) 
1 /*
2  * common LSM auditing functions
3  *
4  * Based on code written for SELinux by :
5  *			Stephen Smalley, <sds@epoch.ncsc.mil>
6  * 			James Morris <jmorris@redhat.com>
7  * Author : Etienne Basset, <etienne.basset@ensta.org>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2,
11  * as published by the Free Software Foundation.
12  */
13 
14 #include <linux/types.h>
15 #include <linux/stddef.h>
16 #include <linux/kernel.h>
17 #include <linux/gfp.h>
18 #include <linux/fs.h>
19 #include <linux/init.h>
20 #include <net/sock.h>
21 #include <linux/un.h>
22 #include <net/af_unix.h>
23 #include <linux/audit.h>
24 #include <linux/ipv6.h>
25 #include <linux/ip.h>
26 #include <net/ip.h>
27 #include <net/ipv6.h>
28 #include <linux/tcp.h>
29 #include <linux/udp.h>
30 #include <linux/dccp.h>
31 #include <linux/sctp.h>
32 #include <linux/lsm_audit.h>
33 
34 /**
35  * ipv4_skb_to_auditdata : fill auditdata from skb
36  * @skb : the skb
37  * @ad : the audit data to fill
38  * @proto : the layer 4 protocol
39  *
40  * return  0 on success
41  */
42 int ipv4_skb_to_auditdata(struct sk_buff *skb,
43 		struct common_audit_data *ad, u8 *proto)
44 {
45 	int ret = 0;
46 	struct iphdr *ih;
47 
48 	ih = ip_hdr(skb);
49 	if (ih == NULL)
50 		return -EINVAL;
51 
52 	ad->u.net->v4info.saddr = ih->saddr;
53 	ad->u.net->v4info.daddr = ih->daddr;
54 
55 	if (proto)
56 		*proto = ih->protocol;
57 	/* non initial fragment */
58 	if (ntohs(ih->frag_off) & IP_OFFSET)
59 		return 0;
60 
61 	switch (ih->protocol) {
62 	case IPPROTO_TCP: {
63 		struct tcphdr *th = tcp_hdr(skb);
64 		if (th == NULL)
65 			break;
66 
67 		ad->u.net->sport = th->source;
68 		ad->u.net->dport = th->dest;
69 		break;
70 	}
71 	case IPPROTO_UDP: {
72 		struct udphdr *uh = udp_hdr(skb);
73 		if (uh == NULL)
74 			break;
75 
76 		ad->u.net->sport = uh->source;
77 		ad->u.net->dport = uh->dest;
78 		break;
79 	}
80 	case IPPROTO_DCCP: {
81 		struct dccp_hdr *dh = dccp_hdr(skb);
82 		if (dh == NULL)
83 			break;
84 
85 		ad->u.net->sport = dh->dccph_sport;
86 		ad->u.net->dport = dh->dccph_dport;
87 		break;
88 	}
89 	case IPPROTO_SCTP: {
90 		struct sctphdr *sh = sctp_hdr(skb);
91 		if (sh == NULL)
92 			break;
93 		ad->u.net->sport = sh->source;
94 		ad->u.net->dport = sh->dest;
95 		break;
96 	}
97 	default:
98 		ret = -EINVAL;
99 	}
100 	return ret;
101 }
102 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
103 /**
104  * ipv6_skb_to_auditdata : fill auditdata from skb
105  * @skb : the skb
106  * @ad : the audit data to fill
107  * @proto : the layer 4 protocol
108  *
109  * return  0 on success
110  */
111 int ipv6_skb_to_auditdata(struct sk_buff *skb,
112 		struct common_audit_data *ad, u8 *proto)
113 {
114 	int offset, ret = 0;
115 	struct ipv6hdr *ip6;
116 	u8 nexthdr;
117 	__be16 frag_off;
118 
119 	ip6 = ipv6_hdr(skb);
120 	if (ip6 == NULL)
121 		return -EINVAL;
122 	ad->u.net->v6info.saddr = ip6->saddr;
123 	ad->u.net->v6info.daddr = ip6->daddr;
124 	ret = 0;
125 	/* IPv6 can have several extension header before the Transport header
126 	 * skip them */
127 	offset = skb_network_offset(skb);
128 	offset += sizeof(*ip6);
129 	nexthdr = ip6->nexthdr;
130 	offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
131 	if (offset < 0)
132 		return 0;
133 	if (proto)
134 		*proto = nexthdr;
135 	switch (nexthdr) {
136 	case IPPROTO_TCP: {
137 		struct tcphdr _tcph, *th;
138 
139 		th = skb_header_pointer(skb, offset, sizeof(_tcph), &_tcph);
140 		if (th == NULL)
141 			break;
142 
143 		ad->u.net->sport = th->source;
144 		ad->u.net->dport = th->dest;
145 		break;
146 	}
147 	case IPPROTO_UDP: {
148 		struct udphdr _udph, *uh;
149 
150 		uh = skb_header_pointer(skb, offset, sizeof(_udph), &_udph);
151 		if (uh == NULL)
152 			break;
153 
154 		ad->u.net->sport = uh->source;
155 		ad->u.net->dport = uh->dest;
156 		break;
157 	}
158 	case IPPROTO_DCCP: {
159 		struct dccp_hdr _dccph, *dh;
160 
161 		dh = skb_header_pointer(skb, offset, sizeof(_dccph), &_dccph);
162 		if (dh == NULL)
163 			break;
164 
165 		ad->u.net->sport = dh->dccph_sport;
166 		ad->u.net->dport = dh->dccph_dport;
167 		break;
168 	}
169 	case IPPROTO_SCTP: {
170 		struct sctphdr _sctph, *sh;
171 
172 		sh = skb_header_pointer(skb, offset, sizeof(_sctph), &_sctph);
173 		if (sh == NULL)
174 			break;
175 		ad->u.net->sport = sh->source;
176 		ad->u.net->dport = sh->dest;
177 		break;
178 	}
179 	default:
180 		ret = -EINVAL;
181 	}
182 	return ret;
183 }
184 #endif
185 
186 
187 static inline void print_ipv6_addr(struct audit_buffer *ab,
188 				   struct in6_addr *addr, __be16 port,
189 				   char *name1, char *name2)
190 {
191 	if (!ipv6_addr_any(addr))
192 		audit_log_format(ab, " %s=%pI6c", name1, addr);
193 	if (port)
194 		audit_log_format(ab, " %s=%d", name2, ntohs(port));
195 }
196 
197 static inline void print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
198 				   __be16 port, char *name1, char *name2)
199 {
200 	if (addr)
201 		audit_log_format(ab, " %s=%pI4", name1, &addr);
202 	if (port)
203 		audit_log_format(ab, " %s=%d", name2, ntohs(port));
204 }
205 
206 /**
207  * dump_common_audit_data - helper to dump common audit data
208  * @a : common audit data
209  *
210  */
211 static void dump_common_audit_data(struct audit_buffer *ab,
212 				   struct common_audit_data *a)
213 {
214 	struct task_struct *tsk = current;
215 
216 	/*
217 	 * To keep stack sizes in check force programers to notice if they
218 	 * start making this union too large!  See struct lsm_network_audit
219 	 * as an example of how to deal with large data.
220 	 */
221 	BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2);
222 
223 	audit_log_format(ab, " pid=%d comm=", task_pid_nr(tsk));
224 	audit_log_untrustedstring(ab, tsk->comm);
225 
226 	switch (a->type) {
227 	case LSM_AUDIT_DATA_NONE:
228 		return;
229 	case LSM_AUDIT_DATA_IPC:
230 		audit_log_format(ab, " key=%d ", a->u.ipc_id);
231 		break;
232 	case LSM_AUDIT_DATA_CAP:
233 		audit_log_format(ab, " capability=%d ", a->u.cap);
234 		break;
235 	case LSM_AUDIT_DATA_PATH: {
236 		struct inode *inode;
237 
238 		audit_log_d_path(ab, " path=", &a->u.path);
239 
240 		inode = a->u.path.dentry->d_inode;
241 		if (inode) {
242 			audit_log_format(ab, " dev=");
243 			audit_log_untrustedstring(ab, inode->i_sb->s_id);
244 			audit_log_format(ab, " ino=%lu", inode->i_ino);
245 		}
246 		break;
247 	}
248 	case LSM_AUDIT_DATA_DENTRY: {
249 		struct inode *inode;
250 
251 		audit_log_format(ab, " name=");
252 		audit_log_untrustedstring(ab, a->u.dentry->d_name.name);
253 
254 		inode = a->u.dentry->d_inode;
255 		if (inode) {
256 			audit_log_format(ab, " dev=");
257 			audit_log_untrustedstring(ab, inode->i_sb->s_id);
258 			audit_log_format(ab, " ino=%lu", inode->i_ino);
259 		}
260 		break;
261 	}
262 	case LSM_AUDIT_DATA_INODE: {
263 		struct dentry *dentry;
264 		struct inode *inode;
265 
266 		inode = a->u.inode;
267 		dentry = d_find_alias(inode);
268 		if (dentry) {
269 			audit_log_format(ab, " name=");
270 			audit_log_untrustedstring(ab,
271 					 dentry->d_name.name);
272 			dput(dentry);
273 		}
274 		audit_log_format(ab, " dev=");
275 		audit_log_untrustedstring(ab, inode->i_sb->s_id);
276 		audit_log_format(ab, " ino=%lu", inode->i_ino);
277 		break;
278 	}
279 	case LSM_AUDIT_DATA_TASK:
280 		tsk = a->u.tsk;
281 		if (tsk) {
282 			pid_t pid = task_pid_nr(tsk);
283 			if (pid) {
284 				audit_log_format(ab, " pid=%d comm=", pid);
285 				audit_log_untrustedstring(ab, tsk->comm);
286 			}
287 		}
288 		break;
289 	case LSM_AUDIT_DATA_NET:
290 		if (a->u.net->sk) {
291 			struct sock *sk = a->u.net->sk;
292 			struct unix_sock *u;
293 			int len = 0;
294 			char *p = NULL;
295 
296 			switch (sk->sk_family) {
297 			case AF_INET: {
298 				struct inet_sock *inet = inet_sk(sk);
299 
300 				print_ipv4_addr(ab, inet->inet_rcv_saddr,
301 						inet->inet_sport,
302 						"laddr", "lport");
303 				print_ipv4_addr(ab, inet->inet_daddr,
304 						inet->inet_dport,
305 						"faddr", "fport");
306 				break;
307 			}
308 #if IS_ENABLED(CONFIG_IPV6)
309 			case AF_INET6: {
310 				struct inet_sock *inet = inet_sk(sk);
311 
312 				print_ipv6_addr(ab, &sk->sk_v6_rcv_saddr,
313 						inet->inet_sport,
314 						"laddr", "lport");
315 				print_ipv6_addr(ab, &sk->sk_v6_daddr,
316 						inet->inet_dport,
317 						"faddr", "fport");
318 				break;
319 			}
320 #endif
321 			case AF_UNIX:
322 				u = unix_sk(sk);
323 				if (u->path.dentry) {
324 					audit_log_d_path(ab, " path=", &u->path);
325 					break;
326 				}
327 				if (!u->addr)
328 					break;
329 				len = u->addr->len-sizeof(short);
330 				p = &u->addr->name->sun_path[0];
331 				audit_log_format(ab, " path=");
332 				if (*p)
333 					audit_log_untrustedstring(ab, p);
334 				else
335 					audit_log_n_hex(ab, p, len);
336 				break;
337 			}
338 		}
339 
340 		switch (a->u.net->family) {
341 		case AF_INET:
342 			print_ipv4_addr(ab, a->u.net->v4info.saddr,
343 					a->u.net->sport,
344 					"saddr", "src");
345 			print_ipv4_addr(ab, a->u.net->v4info.daddr,
346 					a->u.net->dport,
347 					"daddr", "dest");
348 			break;
349 		case AF_INET6:
350 			print_ipv6_addr(ab, &a->u.net->v6info.saddr,
351 					a->u.net->sport,
352 					"saddr", "src");
353 			print_ipv6_addr(ab, &a->u.net->v6info.daddr,
354 					a->u.net->dport,
355 					"daddr", "dest");
356 			break;
357 		}
358 		if (a->u.net->netif > 0) {
359 			struct net_device *dev;
360 
361 			/* NOTE: we always use init's namespace */
362 			dev = dev_get_by_index(&init_net, a->u.net->netif);
363 			if (dev) {
364 				audit_log_format(ab, " netif=%s", dev->name);
365 				dev_put(dev);
366 			}
367 		}
368 		break;
369 #ifdef CONFIG_KEYS
370 	case LSM_AUDIT_DATA_KEY:
371 		audit_log_format(ab, " key_serial=%u", a->u.key_struct.key);
372 		if (a->u.key_struct.key_desc) {
373 			audit_log_format(ab, " key_desc=");
374 			audit_log_untrustedstring(ab, a->u.key_struct.key_desc);
375 		}
376 		break;
377 #endif
378 	case LSM_AUDIT_DATA_KMOD:
379 		audit_log_format(ab, " kmod=");
380 		audit_log_untrustedstring(ab, a->u.kmod_name);
381 		break;
382 	} /* switch (a->type) */
383 }
384 
385 /**
386  * common_lsm_audit - generic LSM auditing function
387  * @a:  auxiliary audit data
388  * @pre_audit: lsm-specific pre-audit callback
389  * @post_audit: lsm-specific post-audit callback
390  *
391  * setup the audit buffer for common security information
392  * uses callback to print LSM specific information
393  */
394 void common_lsm_audit(struct common_audit_data *a,
395 	void (*pre_audit)(struct audit_buffer *, void *),
396 	void (*post_audit)(struct audit_buffer *, void *))
397 {
398 	struct audit_buffer *ab;
399 
400 	if (a == NULL)
401 		return;
402 	/* we use GFP_ATOMIC so we won't sleep */
403 	ab = audit_log_start(current->audit_context, GFP_ATOMIC | __GFP_NOWARN,
404 			     AUDIT_AVC);
405 
406 	if (ab == NULL)
407 		return;
408 
409 	if (pre_audit)
410 		pre_audit(ab, a);
411 
412 	dump_common_audit_data(ab, a);
413 
414 	if (post_audit)
415 		post_audit(ab, a);
416 
417 	audit_log_end(ab);
418 }
419