Implement support for lttng-modules syscall filtering
[lttng-tools.git] / src / common / runas.c
CommitLineData
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1/*
2 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
3 * Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 *
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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.
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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
d14d33bf 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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12 * more details.
13 *
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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.
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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>
c2b75c49 30#include <sched.h>
730389d9 31#include <sys/signal.h>
60b6c79c 32
90e535ef 33#include <common/common.h>
3fd15a74 34#include <common/utils.h>
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35#include <common/compat/mman.h>
36#include <common/compat/clone.h>
60b6c79c 37
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38#include "runas.h"
39
e11d277b 40#define RUNAS_CHILD_STACK_SIZE 10485760
c2b75c49 41
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42#ifndef MAP_STACK
43#define MAP_STACK 0
44#endif
45
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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
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51#endif
52
a5ae566a 53#ifndef MAP_GROWSDOWN
edb025e8 54#define MAP_GROWSDOWN 0
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55#endif
56
57#ifndef MAP_ANONYMOUS
58#define MAP_ANONYMOUS MAP_ANON
59#endif
60
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61struct 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
e11d277b 69struct run_as_mkdir_data {
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70 const char *path;
71 mode_t mode;
72};
73
e11d277b 74struct run_as_open_data {
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75 const char *path;
76 int flags;
77 mode_t mode;
78};
79
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80#ifdef VALGRIND
81static
82int use_clone(void)
83{
84 return 0;
85}
86#else
87static
88int use_clone(void)
89{
90 return !getenv("LTTNG_DEBUG_NOCLONE");
91}
92#endif
93
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94/*
95 * Create recursively directory using the FULL path.
96 */
97static
98int _mkdir_recursive(void *_data)
99{
e11d277b 100 struct run_as_mkdir_data *data = _data;
60b6c79c 101 const char *path;
60b6c79c 102 mode_t mode;
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103
104 path = data->path;
105 mode = data->mode;
106
3fd15a74 107 return utils_mkdir_recursive(path, mode);
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108}
109
110static
111int _mkdir(void *_data)
112{
7ce36756 113 int ret;
e11d277b 114 struct run_as_mkdir_data *data = _data;
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115
116 ret = mkdir(data->path, data->mode);
117 if (ret < 0) {
118 ret = -errno;
119 }
120
121 return ret;
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122}
123
124static
125int _open(void *_data)
126{
e11d277b 127 struct run_as_open_data *data = _data;
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128 return open(data->path, data->flags, data->mode);
129}
130
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131static
132int child_run_as(void *_data)
133{
6775595e 134 int ret;
c2b75c49 135 struct run_as_data *data = _data;
6775595e 136 ssize_t writelen;
6cd525e8 137 int sendret;
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138
139 /*
140 * Child: it is safe to drop egid and euid while sharing the
141 * file descriptors with the parent process, since we do not
142 * drop "uid": therefore, the user we are dropping egid/euid to
143 * cannot attach to this process with, e.g. ptrace, nor map this
144 * process memory.
145 */
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146 if (data->gid != getegid()) {
147 ret = setegid(data->gid);
148 if (ret < 0) {
4c462e79 149 PERROR("setegid");
6cd525e8 150 sendret = -1;
6d73c4ef 151 goto write_return;
1576d582 152 }
c2b75c49 153 }
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154 if (data->uid != geteuid()) {
155 ret = seteuid(data->uid);
156 if (ret < 0) {
4c462e79 157 PERROR("seteuid");
6cd525e8 158 sendret = -1;
6d73c4ef 159 goto write_return;
1576d582 160 }
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161 }
162 /*
163 * Also set umask to 0 for mkdir executable bit.
164 */
165 umask(0);
6cd525e8 166 sendret = (*data->cmd)(data->data);
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167
168write_return:
c2b75c49 169 /* send back return value */
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170 writelen = lttng_write(data->retval_pipe, &sendret, sizeof(sendret));
171 if (writelen < sizeof(sendret)) {
172 PERROR("lttng_write error");
173 return EXIT_FAILURE;
174 } else {
175 return EXIT_SUCCESS;
176 }
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177}
178
60b6c79c 179static
2d85a600 180int run_as_clone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
60b6c79c 181{
c2b75c49 182 struct run_as_data run_as_data;
60b6c79c 183 int ret = 0;
6cd525e8 184 ssize_t readlen;
c2b75c49 185 int status;
60b6c79c 186 pid_t pid;
c2b75c49 187 int retval_pipe[2];
d5bd7573 188 void *child_stack;
6cd525e8 189 int retval;
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190
191 /*
192 * If we are non-root, we can only deal with our own uid.
193 */
194 if (geteuid() != 0) {
195 if (uid != geteuid()) {
196 ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
197 uid, geteuid());
198 return -EPERM;
199 }
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200 }
201
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202 ret = pipe(retval_pipe);
203 if (ret < 0) {
4c462e79 204 PERROR("pipe");
6cd525e8 205 retval = ret;
60b6c79c 206 goto end;
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207 }
208 run_as_data.data = data;
209 run_as_data.cmd = cmd;
210 run_as_data.uid = uid;
211 run_as_data.gid = gid;
212 run_as_data.retval_pipe = retval_pipe[1]; /* write end */
e11d277b 213 child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
d5bd7573 214 PROT_WRITE | PROT_READ,
0756d557 215 MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | LTTNG_MAP_STACK,
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216 -1, 0);
217 if (child_stack == MAP_FAILED) {
4c462e79 218 PERROR("mmap");
6cd525e8 219 retval = -ENOMEM;
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220 goto close_pipe;
221 }
222 /*
223 * Pointing to the middle of the stack to support architectures
224 * where the stack grows up (HPPA).
225 */
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226 pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
227 &run_as_data);
c2b75c49 228 if (pid < 0) {
4c462e79 229 PERROR("clone");
6cd525e8 230 retval = pid;
d5bd7573 231 goto unmap_stack;
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232 }
233 /* receive return value */
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234 readlen = lttng_read(retval_pipe[0], &retval, sizeof(retval));
235 if (readlen < sizeof(retval)) {
236 ret = -1;
237 }
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238
239 /*
240 * Parent: wait for child to return, in which case the
241 * shared memory map will have been created.
242 */
47fb7563 243 pid = waitpid(pid, &status, 0);
c2b75c49 244 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
4c462e79 245 PERROR("wait");
6cd525e8 246 retval = -1;
60b6c79c 247 }
d5bd7573 248unmap_stack:
e11d277b 249 ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
d5bd7573 250 if (ret < 0) {
4c462e79 251 PERROR("munmap");
6cd525e8 252 retval = ret;
d5bd7573 253 }
c2b75c49 254close_pipe:
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255 ret = close(retval_pipe[0]);
256 if (ret) {
257 PERROR("close");
258 }
259 ret = close(retval_pipe[1]);
260 if (ret) {
261 PERROR("close");
262 }
60b6c79c 263end:
6cd525e8 264 return retval;
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265}
266
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267/*
268 * To be used on setups where gdb has issues debugging programs using
269 * clone/rfork. Note that this is for debuging ONLY, and should not be
270 * considered secure.
271 */
272static
273int run_as_noclone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
274{
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275 int ret;
276 mode_t old_mask;
277
278 old_mask = umask(0);
279 ret = cmd(data);
280 umask(old_mask);
281
282 return ret;
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283}
284
285static
286int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
287{
8f0044bf 288 if (use_clone()) {
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289 int ret;
290
2d85a600 291 DBG("Using run_as_clone");
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292 pthread_mutex_lock(&lttng_libc_state_lock);
293 ret = run_as_clone(cmd, data, uid, gid);
294 pthread_mutex_unlock(&lttng_libc_state_lock);
295 return ret;
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296 } else {
297 DBG("Using run_as_noclone");
298 return run_as_noclone(cmd, data, uid, gid);
299 }
300}
301
90e535ef 302LTTNG_HIDDEN
e11d277b 303int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c 304{
e11d277b 305 struct run_as_mkdir_data data;
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306
307 DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
308 path, mode, uid, gid);
309 data.path = path;
310 data.mode = mode;
311 return run_as(_mkdir_recursive, &data, uid, gid);
312}
313
90e535ef 314LTTNG_HIDDEN
e11d277b 315int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c 316{
e11d277b 317 struct run_as_mkdir_data data;
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318
319 DBG3("mkdir() %s with mode %d for uid %d and gid %d",
320 path, mode, uid, gid);
321 data.path = path;
322 data.mode = mode;
323 return run_as(_mkdir, &data, uid, gid);
324}
325
326/*
327 * Note: open_run_as is currently not working. We'd need to pass the fd
328 * opened in the child to the parent.
329 */
90e535ef 330LTTNG_HIDDEN
e11d277b 331int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
60b6c79c 332{
e11d277b 333 struct run_as_open_data data;
c2b75c49 334
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335 DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
336 path, flags, mode, uid, gid);
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337 data.path = path;
338 data.flags = flags;
339 data.mode = mode;
340 return run_as(_open, &data, uid, gid);
60b6c79c 341}
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