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
39 const char **paths_selected = NULL;
40 static unsigned num_selected = 0;
41
42 /*
43 * Return true if specified path matches one that we're tracing.
44 */
45 static int
pathmatch(const char * path)46 pathmatch(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 */
60 static int
upathmatch(struct tcb * tcp,unsigned long upath)61 upathmatch(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 */
72 static int
fdmatch(struct tcb * tcp,int fd)73 fdmatch(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 */
85 static void
storepath(const char * path)86 storepath(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 */
103 int
getfdpath(struct tcb * tcp,int fd,char * buf,unsigned bufsize)104 getfdpath(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 */
127 void
pathtrace_select(const char * path)128 pathtrace_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 */
154 int
pathtrace_match(struct tcb * tcp)155 pathtrace_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