Fix: relayd leak on error in consumer splice()
[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 #include <errno.h>
21 #include <limits.h>
22 #include <stdio.h>
23 #include <stdlib.h>
24 #include <string.h>
25 #include <sys/wait.h>
26 #include <sys/types.h>
27 #include <sys/stat.h>
28 #include <unistd.h>
29 #include <fcntl.h>
30 #include <sched.h>
31 #include <sys/signal.h>
32
33 #include <common/common.h>
34 #include <common/utils.h>
35 #include <common/compat/mman.h>
36 #include <common/compat/clone.h>
37
38 #include "runas.h"
39
40 #define RUNAS_CHILD_STACK_SIZE 10485760
41
42 #ifndef MAP_STACK
43 #define MAP_STACK 0
44 #endif
45
46 #ifdef __FreeBSD__
47 /* FreeBSD MAP_STACK always return -ENOMEM */
48 #define LTTNG_MAP_STACK 0
49 #else
50 #define LTTNG_MAP_STACK MAP_STACK
51 #endif
52
53 #ifndef MAP_GROWSDOWN
54 #define MAP_GROWSDOWN 0
55 #endif
56
57 #ifndef MAP_ANONYMOUS
58 #define MAP_ANONYMOUS MAP_ANON
59 #endif
60
61 struct run_as_data {
62 int (*cmd)(void *data);
63 void *data;
64 uid_t uid;
65 gid_t gid;
66 int retval_pipe;
67 };
68
69 struct run_as_mkdir_data {
70 const char *path;
71 mode_t mode;
72 };
73
74 struct run_as_open_data {
75 const char *path;
76 int flags;
77 mode_t mode;
78 };
79
80 /*
81 * Create recursively directory using the FULL path.
82 */
83 static
84 int _mkdir_recursive(void *_data)
85 {
86 struct run_as_mkdir_data *data = _data;
87 const char *path;
88 mode_t mode;
89
90 path = data->path;
91 mode = data->mode;
92
93 return utils_mkdir_recursive(path, mode);
94 }
95
96 static
97 int _mkdir(void *_data)
98 {
99 int ret;
100 struct run_as_mkdir_data *data = _data;
101
102 ret = mkdir(data->path, data->mode);
103 if (ret < 0) {
104 ret = -errno;
105 }
106
107 return ret;
108 }
109
110 static
111 int _open(void *_data)
112 {
113 struct run_as_open_data *data = _data;
114 return open(data->path, data->flags, data->mode);
115 }
116
117 static
118 int child_run_as(void *_data)
119 {
120 int ret;
121 struct run_as_data *data = _data;
122 ssize_t writelen;
123 int sendret;
124
125 /*
126 * Child: it is safe to drop egid and euid while sharing the
127 * file descriptors with the parent process, since we do not
128 * drop "uid": therefore, the user we are dropping egid/euid to
129 * cannot attach to this process with, e.g. ptrace, nor map this
130 * process memory.
131 */
132 if (data->gid != getegid()) {
133 ret = setegid(data->gid);
134 if (ret < 0) {
135 PERROR("setegid");
136 sendret = -1;
137 goto write_return;
138 }
139 }
140 if (data->uid != geteuid()) {
141 ret = seteuid(data->uid);
142 if (ret < 0) {
143 PERROR("seteuid");
144 sendret = -1;
145 goto write_return;
146 }
147 }
148 /*
149 * Also set umask to 0 for mkdir executable bit.
150 */
151 umask(0);
152 sendret = (*data->cmd)(data->data);
153
154 write_return:
155 /* send back return value */
156 writelen = lttng_write(data->retval_pipe, &sendret, sizeof(sendret));
157 if (writelen < sizeof(sendret)) {
158 PERROR("lttng_write error");
159 return EXIT_FAILURE;
160 } else {
161 return EXIT_SUCCESS;
162 }
163 }
164
165 static
166 int run_as_clone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
167 {
168 struct run_as_data run_as_data;
169 int ret = 0;
170 ssize_t readlen;
171 int status;
172 pid_t pid;
173 int retval_pipe[2];
174 void *child_stack;
175 int retval;
176
177 /*
178 * If we are non-root, we can only deal with our own uid.
179 */
180 if (geteuid() != 0) {
181 if (uid != geteuid()) {
182 ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
183 uid, geteuid());
184 return -EPERM;
185 }
186 }
187
188 ret = pipe(retval_pipe);
189 if (ret < 0) {
190 PERROR("pipe");
191 retval = ret;
192 goto end;
193 }
194 run_as_data.data = data;
195 run_as_data.cmd = cmd;
196 run_as_data.uid = uid;
197 run_as_data.gid = gid;
198 run_as_data.retval_pipe = retval_pipe[1]; /* write end */
199 child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
200 PROT_WRITE | PROT_READ,
201 MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | LTTNG_MAP_STACK,
202 -1, 0);
203 if (child_stack == MAP_FAILED) {
204 PERROR("mmap");
205 retval = -ENOMEM;
206 goto close_pipe;
207 }
208 /*
209 * Pointing to the middle of the stack to support architectures
210 * where the stack grows up (HPPA).
211 */
212 pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
213 &run_as_data);
214 if (pid < 0) {
215 PERROR("clone");
216 retval = pid;
217 goto unmap_stack;
218 }
219 /* receive return value */
220 readlen = lttng_read(retval_pipe[0], &retval, sizeof(retval));
221 if (readlen < sizeof(retval)) {
222 ret = -1;
223 }
224
225 /*
226 * Parent: wait for child to return, in which case the
227 * shared memory map will have been created.
228 */
229 pid = waitpid(pid, &status, 0);
230 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
231 PERROR("wait");
232 retval = -1;
233 }
234 unmap_stack:
235 ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
236 if (ret < 0) {
237 PERROR("munmap");
238 retval = ret;
239 }
240 close_pipe:
241 ret = close(retval_pipe[0]);
242 if (ret) {
243 PERROR("close");
244 }
245 ret = close(retval_pipe[1]);
246 if (ret) {
247 PERROR("close");
248 }
249 end:
250 return retval;
251 }
252
253 /*
254 * To be used on setups where gdb has issues debugging programs using
255 * clone/rfork. Note that this is for debuging ONLY, and should not be
256 * considered secure.
257 */
258 static
259 int run_as_noclone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
260 {
261 int ret;
262 mode_t old_mask;
263
264 old_mask = umask(0);
265 ret = cmd(data);
266 umask(old_mask);
267
268 return ret;
269 }
270
271 static
272 int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
273 {
274 if (!getenv("LTTNG_DEBUG_NOCLONE")) {
275 int ret;
276
277 DBG("Using run_as_clone");
278 pthread_mutex_lock(&lttng_libc_state_lock);
279 ret = run_as_clone(cmd, data, uid, gid);
280 pthread_mutex_unlock(&lttng_libc_state_lock);
281 return ret;
282 } else {
283 DBG("Using run_as_noclone");
284 return run_as_noclone(cmd, data, uid, gid);
285 }
286 }
287
288 LTTNG_HIDDEN
289 int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
290 {
291 struct run_as_mkdir_data data;
292
293 DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
294 path, mode, uid, gid);
295 data.path = path;
296 data.mode = mode;
297 return run_as(_mkdir_recursive, &data, uid, gid);
298 }
299
300 LTTNG_HIDDEN
301 int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
302 {
303 struct run_as_mkdir_data data;
304
305 DBG3("mkdir() %s with mode %d for uid %d and gid %d",
306 path, mode, uid, gid);
307 data.path = path;
308 data.mode = mode;
309 return run_as(_mkdir, &data, uid, gid);
310 }
311
312 /*
313 * Note: open_run_as is currently not working. We'd need to pass the fd
314 * opened in the child to the parent.
315 */
316 LTTNG_HIDDEN
317 int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
318 {
319 struct run_as_open_data data;
320
321 DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
322 path, flags, mode, uid, gid);
323 data.path = path;
324 data.flags = flags;
325 data.mode = mode;
326 return run_as(_open, &data, uid, gid);
327 }
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