1/*
2 * Copyright (c) 2011, Comtrol Corp.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote products
14 *    derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29#include "defs.h"
30#include <sys/param.h>
31#if defined HAVE_POLL_H
32# include <poll.h>
33#elif defined HAVE_SYS_POLL_H
34# include <sys/poll.h>
35#endif
36
37#include "syscall.h"
38
39const char **paths_selected = NULL;
40static unsigned num_selected = 0;
41
42/*
43 * Return true if specified path matches one that we're tracing.
44 */
45static int
46pathmatch(const char *path)
47{
48	unsigned i;
49
50	for (i = 0; i < num_selected; ++i) {
51		if (strcmp(path, paths_selected[i]) == 0)
52			return 1;
53	}
54	return 0;
55}
56
57/*
58 * Return true if specified path (in user-space) matches.
59 */
60static int
61upathmatch(struct tcb *tcp, unsigned long upath)
62{
63	char path[PATH_MAX + 1];
64
65	return umovestr(tcp, upath, sizeof path, path) > 0 &&
66		pathmatch(path);
67}
68
69/*
70 * Return true if specified fd maps to a path we're tracing.
71 */
72static int
73fdmatch(struct tcb *tcp, int fd)
74{
75	char path[PATH_MAX + 1];
76	int n = getfdpath(tcp, fd, path, sizeof(path));
77
78	return n >= 0 && pathmatch(path);
79}
80
81/*
82 * Add a path to the set we're tracing.
83 * Specifying NULL will delete all paths.
84 */
85static void
86storepath(const char *path)
87{
88	unsigned i;
89
90	if (pathmatch(path))
91		return; /* already in table */
92
93	i = num_selected++;
94	paths_selected = realloc(paths_selected, num_selected * sizeof(paths_selected[0]));
95	if (!paths_selected)
96		die_out_of_memory();
97	paths_selected[i] = path;
98}
99
100/*
101 * Get path associated with fd.
102 */
103int
104getfdpath(struct tcb *tcp, int fd, char *buf, unsigned bufsize)
105{
106	char linkpath[sizeof("/proc/%u/fd/%u") + 2 * sizeof(int)*3];
107	ssize_t n;
108
109	if (fd < 0)
110		return -1;
111
112	sprintf(linkpath, "/proc/%u/fd/%u", tcp->pid, fd);
113	n = readlink(linkpath, buf, bufsize - 1);
114	/*
115	 * NB: if buf is too small, readlink doesn't fail,
116	 * it returns truncated result (IOW: n == bufsize - 1).
117	 */
118	if (n >= 0)
119		buf[n] = '\0';
120	return n;
121}
122
123/*
124 * Add a path to the set we're tracing.  Also add the canonicalized
125 * version of the path.  Secifying NULL will delete all paths.
126 */
127void
128pathtrace_select(const char *path)
129{
130	char *rpath;
131
132	storepath(path);
133
134	rpath = realpath(path, NULL);
135
136	if (rpath == NULL)
137		return;
138
139	/* if realpath and specified path are same, we're done */
140	if (strcmp(path, rpath) == 0) {
141		free(rpath);
142		return;
143	}
144
145	fprintf(stderr, "Requested path '%s' resolved into '%s'\n",
146		path, rpath);
147	storepath(rpath);
148}
149
150/*
151 * Return true if syscall accesses a selected path
152 * (or if no paths have been specified for tracing).
153 */
154int
155pathtrace_match(struct tcb *tcp)
156{
157	const struct_sysent *s;
158
159	s = tcp->s_ent;
160
161	if (!(s->sys_flags & (TRACE_FILE | TRACE_DESC | TRACE_NETWORK)))
162		return 0;
163
164	/*
165	 * Check for special cases where we need to do something
166	 * other than test arg[0].
167	 */
168
169	if (s->sys_func == sys_dup2 ||
170	    s->sys_func == sys_dup3 ||
171	    s->sys_func == sys_sendfile ||
172	    s->sys_func == sys_sendfile64 ||
173	    s->sys_func == sys_tee)
174	{
175		/* fd, fd */
176		return fdmatch(tcp, tcp->u_arg[0]) ||
177			fdmatch(tcp, tcp->u_arg[1]);
178	}
179
180	if (s->sys_func == sys_inotify_add_watch ||
181	    s->sys_func == sys_faccessat ||
182	    s->sys_func == sys_fchmodat ||
183	    s->sys_func == sys_futimesat ||
184	    s->sys_func == sys_mkdirat ||
185	    s->sys_func == sys_unlinkat ||
186	    s->sys_func == sys_newfstatat ||
187	    s->sys_func == sys_mknodat ||
188	    s->sys_func == sys_openat ||
189	    s->sys_func == sys_readlinkat ||
190	    s->sys_func == sys_utimensat ||
191	    s->sys_func == sys_fchownat ||
192	    s->sys_func == sys_pipe2)
193	{
194		/* fd, path */
195		return fdmatch(tcp, tcp->u_arg[0]) ||
196			upathmatch(tcp, tcp->u_arg[1]);
197	}
198
199	if (s->sys_func == sys_link ||
200	    s->sys_func == sys_mount)
201	{
202		/* path, path */
203		return upathmatch(tcp, tcp->u_arg[0]) ||
204			upathmatch(tcp, tcp->u_arg[1]);
205	}
206
207	if (s->sys_func == sys_quotactl)
208	{
209		/* x, path */
210		return upathmatch(tcp, tcp->u_arg[1]);
211	}
212
213	if (s->sys_func == sys_renameat ||
214	    s->sys_func == sys_linkat)
215	{
216		/* fd, path, fd, path */
217		return fdmatch(tcp, tcp->u_arg[0]) ||
218			fdmatch(tcp, tcp->u_arg[2]) ||
219			upathmatch(tcp, tcp->u_arg[1]) ||
220			upathmatch(tcp, tcp->u_arg[3]);
221	}
222
223	if (
224	    s->sys_func == sys_old_mmap ||
225#if defined(S390)
226	    s->sys_func == sys_old_mmap_pgoff ||
227#endif
228	    s->sys_func == sys_mmap ||
229	    s->sys_func == sys_mmap_pgoff ||
230	    s->sys_func == sys_mmap_4koff
231	) {
232		/* x, x, x, x, fd */
233		return fdmatch(tcp, tcp->u_arg[4]);
234	}
235
236	if (s->sys_func == sys_symlinkat) {
237		/* path, fd, path */
238		return fdmatch(tcp, tcp->u_arg[1]) ||
239			upathmatch(tcp, tcp->u_arg[0]) ||
240			upathmatch(tcp, tcp->u_arg[2]);
241	}
242
243	if (s->sys_func == sys_splice) {
244		/* fd, x, fd, x, x */
245		return fdmatch(tcp, tcp->u_arg[0]) ||
246			fdmatch(tcp, tcp->u_arg[2]);
247	}
248
249	if (s->sys_func == sys_epoll_ctl) {
250		/* x, x, fd, x */
251		return fdmatch(tcp, tcp->u_arg[2]);
252	}
253
254	if (s->sys_func == sys_fanotify_mark) {
255		/* x, x, x, fd, path */
256		return fdmatch(tcp, tcp->u_arg[3]) ||
257			upathmatch(tcp, tcp->u_arg[4]);
258	}
259
260	if (s->sys_func == sys_select ||
261	    s->sys_func == sys_oldselect ||
262	    s->sys_func == sys_pselect6)
263	{
264		int     i, j;
265		int     nfds;
266		long   *args, oldargs[5];
267		unsigned fdsize;
268		fd_set *fds;
269
270		args = tcp->u_arg;
271		if (s->sys_func == sys_oldselect) {
272			if (umoven(tcp, tcp->u_arg[0], sizeof oldargs,
273				   (char*) oldargs) < 0)
274			{
275				fprintf(stderr, "umoven() failed\n");
276				return 0;
277			}
278			args = oldargs;
279		}
280
281		/* Kernel truncates arg[0] to int, we do the same. */
282		nfds = (int) args[0];
283		/* Kernel rejects negative nfds, so we don't parse it either. */
284		if (nfds <= 0)
285			return 0;
286		/* Beware of select(2^31-1, NULL, NULL, NULL) and similar... */
287		if (nfds > 1024*1024)
288			nfds = 1024*1024;
289		fdsize = (((nfds + 7) / 8) + current_wordsize-1) & -current_wordsize;
290		fds = malloc(fdsize);
291		if (!fds)
292			die_out_of_memory();
293
294		for (i = 1; i <= 3; ++i) {
295			if (args[i] == 0)
296				continue;
297			if (umoven(tcp, args[i], fdsize, (char *) fds) < 0) {
298				fprintf(stderr, "umoven() failed\n");
299				continue;
300			}
301			for (j = 0;; j++) {
302				j = next_set_bit(fds, j, nfds);
303				if (j < 0)
304					break;
305				if (fdmatch(tcp, j)) {
306					free(fds);
307					return 1;
308				}
309			}
310		}
311		free(fds);
312		return 0;
313	}
314
315	if (s->sys_func == sys_poll ||
316	    s->sys_func == sys_ppoll)
317	{
318		struct pollfd fds;
319		unsigned nfds;
320		unsigned long start, cur, end;
321
322		start = tcp->u_arg[0];
323		nfds = tcp->u_arg[1];
324
325		end = start + sizeof(fds) * nfds;
326
327		if (nfds == 0 || end < start)
328			return 0;
329
330		for (cur = start; cur < end; cur += sizeof(fds))
331			if ((umoven(tcp, cur, sizeof fds, (char *) &fds) == 0)
332			    && fdmatch(tcp, fds.fd))
333				return 1;
334
335		return 0;
336	}
337
338	if (s->sys_func == printargs ||
339	    s->sys_func == sys_pipe ||
340	    s->sys_func == sys_pipe2 ||
341	    s->sys_func == sys_eventfd2 ||
342	    s->sys_func == sys_eventfd ||
343	    s->sys_func == sys_inotify_init1 ||
344	    s->sys_func == sys_timerfd_create ||
345	    s->sys_func == sys_timerfd_settime ||
346	    s->sys_func == sys_timerfd_gettime ||
347	    s->sys_func == sys_epoll_create ||
348	    s->sys_func == sys_socket ||
349	    s->sys_func == sys_socketpair ||
350	    s->sys_func == sys_fanotify_init)
351	{
352		/*
353		 * These have TRACE_FILE or TRACE_DESCRIPTOR or TRACE_NETWORK set,
354		 * but they don't have any file descriptor or path args to test.
355		 */
356		return 0;
357	}
358
359	/*
360	 * Our fallback position for calls that haven't already
361	 * been handled is to just check arg[0].
362	 */
363
364	if (s->sys_flags & TRACE_FILE)
365		return upathmatch(tcp, tcp->u_arg[0]);
366
367	if (s->sys_flags & (TRACE_DESC | TRACE_NETWORK))
368		return fdmatch(tcp, tcp->u_arg[0]);
369
370	return 0;
371}
372