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 #include <poll.h>
32
33 #include "syscall.h"
34
35 const char **paths_selected = NULL;
36 static unsigned num_selected = 0;
37
38 /*
39 * Return true if specified path matches one that we're tracing.
40 */
41 static int
pathmatch(const char * path)42 pathmatch(const char *path)
43 {
44 unsigned i;
45
46 for (i = 0; i < num_selected; ++i) {
47 if (strcmp(path, paths_selected[i]) == 0)
48 return 1;
49 }
50 return 0;
51 }
52
53 /*
54 * Return true if specified path (in user-space) matches.
55 */
56 static int
upathmatch(struct tcb * tcp,unsigned long upath)57 upathmatch(struct tcb *tcp, unsigned long upath)
58 {
59 char path[PATH_MAX + 1];
60
61 return umovestr(tcp, upath, sizeof path, path) > 0 &&
62 pathmatch(path);
63 }
64
65 /*
66 * Return true if specified fd maps to a path we're tracing.
67 */
68 static int
fdmatch(struct tcb * tcp,int fd)69 fdmatch(struct tcb *tcp, int fd)
70 {
71 char path[PATH_MAX + 1];
72 int n = getfdpath(tcp, fd, path, sizeof(path));
73
74 return n >= 0 && pathmatch(path);
75 }
76
77 /*
78 * Add a path to the set we're tracing.
79 * Specifying NULL will delete all paths.
80 */
81 static void
storepath(const char * path)82 storepath(const char *path)
83 {
84 unsigned i;
85
86 if (pathmatch(path))
87 return; /* already in table */
88
89 i = num_selected++;
90 paths_selected = xreallocarray(paths_selected, num_selected,
91 sizeof(paths_selected[0]));
92 paths_selected[i] = path;
93 }
94
95 /*
96 * Get path associated with fd.
97 */
98 int
getfdpath(struct tcb * tcp,int fd,char * buf,unsigned bufsize)99 getfdpath(struct tcb *tcp, int fd, char *buf, unsigned bufsize)
100 {
101 char linkpath[sizeof("/proc/%u/fd/%u") + 2 * sizeof(int)*3];
102 ssize_t n;
103
104 if (fd < 0)
105 return -1;
106
107 sprintf(linkpath, "/proc/%u/fd/%u", tcp->pid, fd);
108 n = readlink(linkpath, buf, bufsize - 1);
109 /*
110 * NB: if buf is too small, readlink doesn't fail,
111 * it returns truncated result (IOW: n == bufsize - 1).
112 */
113 if (n >= 0)
114 buf[n] = '\0';
115 return n;
116 }
117
118 /*
119 * Add a path to the set we're tracing. Also add the canonicalized
120 * version of the path. Secifying NULL will delete all paths.
121 */
122 void
pathtrace_select(const char * path)123 pathtrace_select(const char *path)
124 {
125 char *rpath;
126
127 storepath(path);
128
129 rpath = realpath(path, NULL);
130
131 if (rpath == NULL)
132 return;
133
134 /* if realpath and specified path are same, we're done */
135 if (strcmp(path, rpath) == 0) {
136 free(rpath);
137 return;
138 }
139
140 error_msg("Requested path '%s' resolved into '%s'", path, rpath);
141 storepath(rpath);
142 }
143
144 /*
145 * Return true if syscall accesses a selected path
146 * (or if no paths have been specified for tracing).
147 */
148 int
pathtrace_match(struct tcb * tcp)149 pathtrace_match(struct tcb *tcp)
150 {
151 const struct_sysent *s;
152
153 s = tcp->s_ent;
154
155 if (!(s->sys_flags & (TRACE_FILE | TRACE_DESC | TRACE_NETWORK)))
156 return 0;
157
158 /*
159 * Check for special cases where we need to do something
160 * other than test arg[0].
161 */
162
163 switch (s->sen) {
164 case SEN_dup2:
165 case SEN_dup3:
166 case SEN_kexec_file_load:
167 case SEN_sendfile:
168 case SEN_sendfile64:
169 case SEN_tee:
170 /* fd, fd */
171 return fdmatch(tcp, tcp->u_arg[0]) ||
172 fdmatch(tcp, tcp->u_arg[1]);
173
174 case SEN_faccessat:
175 case SEN_fchmodat:
176 case SEN_fchownat:
177 case SEN_futimesat:
178 case SEN_inotify_add_watch:
179 case SEN_mkdirat:
180 case SEN_mknodat:
181 case SEN_name_to_handle_at:
182 case SEN_newfstatat:
183 case SEN_openat:
184 case SEN_pipe2:
185 case SEN_readlinkat:
186 case SEN_unlinkat:
187 case SEN_utimensat:
188 /* fd, path */
189 return fdmatch(tcp, tcp->u_arg[0]) ||
190 upathmatch(tcp, tcp->u_arg[1]);
191
192 case SEN_link:
193 case SEN_mount:
194 case SEN_pivotroot:
195 /* path, path */
196 return upathmatch(tcp, tcp->u_arg[0]) ||
197 upathmatch(tcp, tcp->u_arg[1]);
198
199 case SEN_quotactl:
200 /* x, path */
201 return upathmatch(tcp, tcp->u_arg[1]);
202
203 case SEN_linkat:
204 case SEN_renameat2:
205 case SEN_renameat:
206 /* fd, path, fd, path */
207 return fdmatch(tcp, tcp->u_arg[0]) ||
208 fdmatch(tcp, tcp->u_arg[2]) ||
209 upathmatch(tcp, tcp->u_arg[1]) ||
210 upathmatch(tcp, tcp->u_arg[3]);
211
212 case SEN_old_mmap:
213 #if defined(S390)
214 case SEN_old_mmap_pgoff:
215 #endif
216 case SEN_mmap:
217 case SEN_mmap_4koff:
218 case SEN_mmap_pgoff:
219 case SEN_ARCH_mmap:
220 /* x, x, x, x, fd */
221 return fdmatch(tcp, tcp->u_arg[4]);
222
223 case SEN_symlinkat:
224 /* path, fd, path */
225 return fdmatch(tcp, tcp->u_arg[1]) ||
226 upathmatch(tcp, tcp->u_arg[0]) ||
227 upathmatch(tcp, tcp->u_arg[2]);
228
229 case SEN_splice:
230 /* fd, x, fd, x, x */
231 return fdmatch(tcp, tcp->u_arg[0]) ||
232 fdmatch(tcp, tcp->u_arg[2]);
233
234 case SEN_epoll_ctl:
235 /* x, x, fd, x */
236 return fdmatch(tcp, tcp->u_arg[2]);
237
238
239 case SEN_fanotify_mark:
240 /* x, x, x, fd, path */
241 return fdmatch(tcp, tcp->u_arg[3]) ||
242 upathmatch(tcp, tcp->u_arg[4]);
243
244 case SEN_oldselect:
245 case SEN_pselect6:
246 case SEN_select:
247 {
248 int i, j;
249 int nfds;
250 long *args, oldargs[5];
251 unsigned fdsize;
252 fd_set *fds;
253
254 args = tcp->u_arg;
255 if (SEN_oldselect == s->sen) {
256 if (umoven(tcp, tcp->u_arg[0], sizeof oldargs,
257 oldargs) < 0)
258 {
259 error_msg("umoven() failed");
260 return 0;
261 }
262 args = oldargs;
263 }
264
265 /* Kernel truncates arg[0] to int, we do the same. */
266 nfds = (int) args[0];
267 /* Kernel rejects negative nfds, so we don't parse it either. */
268 if (nfds <= 0)
269 return 0;
270 /* Beware of select(2^31-1, NULL, NULL, NULL) and similar... */
271 if (nfds > 1024*1024)
272 nfds = 1024*1024;
273 fdsize = (((nfds + 7) / 8) + current_wordsize-1) & -current_wordsize;
274 fds = xmalloc(fdsize);
275
276 for (i = 1; i <= 3; ++i) {
277 if (args[i] == 0)
278 continue;
279 if (umoven(tcp, args[i], fdsize, fds) < 0) {
280 error_msg("umoven() failed");
281 continue;
282 }
283 for (j = 0;; j++) {
284 j = next_set_bit(fds, j, nfds);
285 if (j < 0)
286 break;
287 if (fdmatch(tcp, j)) {
288 free(fds);
289 return 1;
290 }
291 }
292 }
293 free(fds);
294 return 0;
295 }
296
297 case SEN_poll:
298 case SEN_ppoll:
299 {
300 struct pollfd fds;
301 unsigned nfds;
302 unsigned long start, cur, end;
303
304 start = tcp->u_arg[0];
305 nfds = tcp->u_arg[1];
306
307 end = start + sizeof(fds) * nfds;
308
309 if (nfds == 0 || end < start)
310 return 0;
311
312 for (cur = start; cur < end; cur += sizeof(fds))
313 if ((umoven(tcp, cur, sizeof fds, &fds) == 0)
314 && fdmatch(tcp, fds.fd))
315 return 1;
316
317 return 0;
318 }
319
320 case SEN_bpf:
321 case SEN_epoll_create:
322 case SEN_epoll_create1:
323 case SEN_eventfd2:
324 case SEN_eventfd:
325 case SEN_fanotify_init:
326 case SEN_inotify_init1:
327 case SEN_memfd_create:
328 case SEN_perf_event_open:
329 case SEN_pipe:
330 case SEN_printargs:
331 case SEN_socket:
332 case SEN_socketpair:
333 case SEN_timerfd_create:
334 case SEN_timerfd_gettime:
335 case SEN_timerfd_settime:
336 case SEN_userfaultfd:
337 /*
338 * These have TRACE_FILE or TRACE_DESCRIPTOR or TRACE_NETWORK set,
339 * but they don't have any file descriptor or path args to test.
340 */
341 return 0;
342 }
343
344 /*
345 * Our fallback position for calls that haven't already
346 * been handled is to just check arg[0].
347 */
348
349 if (s->sys_flags & TRACE_FILE)
350 return upathmatch(tcp, tcp->u_arg[0]);
351
352 if (s->sys_flags & (TRACE_DESC | TRACE_NETWORK))
353 return fdmatch(tcp, tcp->u_arg[0]);
354
355 return 0;
356 }
357