Accept uid and gid parameters in utils_mkdir()/utils_mkdir_recursive()
[lttng-tools.git] / src / common / runas.c
1 /*
2 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
3 * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License, version 2 only,
7 * as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 *
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
17 */
18
19 #define _GNU_SOURCE
20 #define _LGPL_SOURCE
21 #include <errno.h>
22 #include <limits.h>
23 #include <stdio.h>
24 #include <stdlib.h>
25 #include <string.h>
26 #include <sys/wait.h>
27 #include <sys/types.h>
28 #include <sys/stat.h>
29 #include <unistd.h>
30 #include <fcntl.h>
31 #include <sched.h>
32 #include <sys/signal.h>
33
34 #include <common/common.h>
35 #include <common/utils.h>
36 #include <common/compat/mman.h>
37 #include <common/compat/clone.h>
38 #include <common/compat/getenv.h>
39
40 #include "runas.h"
41
42 #define RUNAS_CHILD_STACK_SIZE 10485760
43
44 #ifndef MAP_STACK
45 #define MAP_STACK 0
46 #endif
47
48 #ifdef __FreeBSD__
49 /* FreeBSD MAP_STACK always return -ENOMEM */
50 #define LTTNG_MAP_STACK 0
51 #else
52 #define LTTNG_MAP_STACK MAP_STACK
53 #endif
54
55 #ifndef MAP_GROWSDOWN
56 #define MAP_GROWSDOWN 0
57 #endif
58
59 #ifndef MAP_ANONYMOUS
60 #define MAP_ANONYMOUS MAP_ANON
61 #endif
62
63 struct run_as_data {
64 int (*cmd)(void *data);
65 void *data;
66 uid_t uid;
67 gid_t gid;
68 int retval_pipe;
69 };
70
71 struct run_as_mkdir_data {
72 const char *path;
73 mode_t mode;
74 };
75
76 struct run_as_open_data {
77 const char *path;
78 int flags;
79 mode_t mode;
80 };
81
82 struct run_as_unlink_data {
83 const char *path;
84 };
85
86 struct run_as_recursive_rmdir_data {
87 const char *path;
88 };
89
90 #ifdef VALGRIND
91 static
92 int use_clone(void)
93 {
94 return 0;
95 }
96 #else
97 static
98 int use_clone(void)
99 {
100 return !lttng_secure_getenv("LTTNG_DEBUG_NOCLONE");
101 }
102 #endif
103
104 LTTNG_HIDDEN
105 int _utils_mkdir_recursive_unsafe(const char *path, mode_t mode);
106
107 /*
108 * Create recursively directory using the FULL path.
109 */
110 static
111 int _mkdir_recursive(void *_data)
112 {
113 struct run_as_mkdir_data *data = _data;
114 const char *path;
115 mode_t mode;
116
117 path = data->path;
118 mode = data->mode;
119
120 /* Safe to call as we have transitioned to the requested uid/gid. */
121 return _utils_mkdir_recursive_unsafe(path, mode);
122 }
123
124 static
125 int _mkdir(void *_data)
126 {
127 int ret;
128 struct run_as_mkdir_data *data = _data;
129
130 ret = mkdir(data->path, data->mode);
131 if (ret < 0) {
132 ret = -errno;
133 }
134
135 return ret;
136 }
137
138 static
139 int _open(void *_data)
140 {
141 struct run_as_open_data *data = _data;
142 return open(data->path, data->flags, data->mode);
143 }
144
145 static
146 int _unlink(void *_data)
147 {
148 int ret;
149 struct run_as_unlink_data *data = _data;
150
151 ret = unlink(data->path);
152 if (ret < 0) {
153 ret = -errno;
154 }
155
156 return ret;
157 }
158
159 static
160 int _recursive_rmdir(void *_data)
161 {
162 int ret;
163 struct run_as_recursive_rmdir_data *data = _data;
164
165 ret = utils_recursive_rmdir(data->path);
166 if (ret < 0) {
167 ret = -errno;
168 }
169
170 return ret;
171 }
172
173 static
174 int child_run_as(void *_data)
175 {
176 int ret;
177 struct run_as_data *data = _data;
178 ssize_t writelen;
179 int sendret;
180
181 /*
182 * Child: it is safe to drop egid and euid while sharing the
183 * file descriptors with the parent process, since we do not
184 * drop "uid": therefore, the user we are dropping egid/euid to
185 * cannot attach to this process with, e.g. ptrace, nor map this
186 * process memory.
187 */
188 if (data->gid != getegid()) {
189 ret = setegid(data->gid);
190 if (ret < 0) {
191 PERROR("setegid");
192 sendret = -1;
193 goto write_return;
194 }
195 }
196 if (data->uid != geteuid()) {
197 ret = seteuid(data->uid);
198 if (ret < 0) {
199 PERROR("seteuid");
200 sendret = -1;
201 goto write_return;
202 }
203 }
204 /*
205 * Also set umask to 0 for mkdir executable bit.
206 */
207 umask(0);
208 sendret = (*data->cmd)(data->data);
209
210 write_return:
211 /* send back return value */
212 writelen = lttng_write(data->retval_pipe, &sendret, sizeof(sendret));
213 if (writelen < sizeof(sendret)) {
214 PERROR("lttng_write error");
215 return EXIT_FAILURE;
216 } else {
217 return EXIT_SUCCESS;
218 }
219 }
220
221 static
222 int run_as_clone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
223 {
224 struct run_as_data run_as_data;
225 int ret = 0;
226 ssize_t readlen;
227 int status;
228 pid_t pid;
229 int retval_pipe[2];
230 void *child_stack;
231 int retval;
232
233 /*
234 * If we are non-root, we can only deal with our own uid.
235 */
236 if (geteuid() != 0) {
237 if (uid != geteuid()) {
238 ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
239 uid, geteuid());
240 return -EPERM;
241 }
242 }
243
244 ret = pipe(retval_pipe);
245 if (ret < 0) {
246 PERROR("pipe");
247 retval = ret;
248 goto end;
249 }
250 run_as_data.data = data;
251 run_as_data.cmd = cmd;
252 run_as_data.uid = uid;
253 run_as_data.gid = gid;
254 run_as_data.retval_pipe = retval_pipe[1]; /* write end */
255 child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
256 PROT_WRITE | PROT_READ,
257 MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | LTTNG_MAP_STACK,
258 -1, 0);
259 if (child_stack == MAP_FAILED) {
260 PERROR("mmap");
261 retval = -ENOMEM;
262 goto close_pipe;
263 }
264 /*
265 * Pointing to the middle of the stack to support architectures
266 * where the stack grows up (HPPA).
267 */
268 pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
269 &run_as_data);
270 if (pid < 0) {
271 PERROR("clone");
272 retval = pid;
273 goto unmap_stack;
274 }
275 /* receive return value */
276 readlen = lttng_read(retval_pipe[0], &retval, sizeof(retval));
277 if (readlen < sizeof(retval)) {
278 ret = -1;
279 }
280
281 /*
282 * Parent: wait for child to return, in which case the
283 * shared memory map will have been created.
284 */
285 pid = waitpid(pid, &status, 0);
286 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
287 PERROR("wait");
288 retval = -1;
289 }
290 unmap_stack:
291 ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
292 if (ret < 0) {
293 PERROR("munmap");
294 retval = ret;
295 }
296 close_pipe:
297 ret = close(retval_pipe[0]);
298 if (ret) {
299 PERROR("close");
300 }
301 ret = close(retval_pipe[1]);
302 if (ret) {
303 PERROR("close");
304 }
305 end:
306 return retval;
307 }
308
309 /*
310 * To be used on setups where gdb has issues debugging programs using
311 * clone/rfork. Note that this is for debuging ONLY, and should not be
312 * considered secure.
313 */
314 static
315 int run_as_noclone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
316 {
317 int ret;
318 mode_t old_mask;
319
320 old_mask = umask(0);
321 ret = cmd(data);
322 umask(old_mask);
323
324 return ret;
325 }
326
327 static
328 int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
329 {
330 if (use_clone()) {
331 int ret;
332
333 DBG("Using run_as_clone");
334 pthread_mutex_lock(&lttng_libc_state_lock);
335 ret = run_as_clone(cmd, data, uid, gid);
336 pthread_mutex_unlock(&lttng_libc_state_lock);
337 return ret;
338 } else {
339 DBG("Using run_as_noclone");
340 return run_as_noclone(cmd, data, uid, gid);
341 }
342 }
343
344 LTTNG_HIDDEN
345 int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
346 {
347 struct run_as_mkdir_data data;
348
349 DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
350 path, mode, uid, gid);
351 data.path = path;
352 data.mode = mode;
353 return run_as(_mkdir_recursive, &data, uid, gid);
354 }
355
356 LTTNG_HIDDEN
357 int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
358 {
359 struct run_as_mkdir_data data;
360
361 DBG3("mkdir() %s with mode %d for uid %d and gid %d",
362 path, mode, uid, gid);
363 data.path = path;
364 data.mode = mode;
365 return run_as(_mkdir, &data, uid, gid);
366 }
367
368 /*
369 * Note: open_run_as is currently not working. We'd need to pass the fd
370 * opened in the child to the parent.
371 */
372 LTTNG_HIDDEN
373 int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
374 {
375 struct run_as_open_data data;
376
377 DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
378 path, flags, mode, uid, gid);
379 data.path = path;
380 data.flags = flags;
381 data.mode = mode;
382 return run_as(_open, &data, uid, gid);
383 }
384
385 LTTNG_HIDDEN
386 int run_as_unlink(const char *path, uid_t uid, gid_t gid)
387 {
388 struct run_as_unlink_data data;
389
390 DBG3("unlink() %s with for uid %d and gid %d",
391 path, uid, gid);
392 data.path = path;
393 return run_as(_unlink, &data, uid, gid);
394 }
395
396 LTTNG_HIDDEN
397 int run_as_recursive_rmdir(const char *path, uid_t uid, gid_t gid)
398 {
399 struct run_as_recursive_rmdir_data data;
400
401 DBG3("recursive_rmdir() %s with for uid %d and gid %d",
402 path, uid, gid);
403 data.path = path;
404 return run_as(_recursive_rmdir, &data, uid, gid);
405 }
This page took 0.0574519999999999 seconds and 4 git commands to generate.