Fix: Missing umask when using run as no clone
[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
db758600 33#include <common/error.h>
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34#include <common/compat/mman.h>
35#include <common/compat/clone.h>
60b6c79c 36
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37#include "runas.h"
38
e11d277b 39#define RUNAS_CHILD_STACK_SIZE 10485760
c2b75c49 40
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41#ifndef MAP_STACK
42#define MAP_STACK 0
43#endif
44
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45#ifdef __FreeBSD__
46/* FreeBSD MAP_STACK always return -ENOMEM */
47#define LTTNG_MAP_STACK 0
48#else
49#define LTTNG_MAP_STACK MAP_STACK
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50#endif
51
a5ae566a 52#ifndef MAP_GROWSDOWN
edb025e8 53#define MAP_GROWSDOWN 0
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54#endif
55
56#ifndef MAP_ANONYMOUS
57#define MAP_ANONYMOUS MAP_ANON
58#endif
59
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60struct run_as_data {
61 int (*cmd)(void *data);
62 void *data;
63 uid_t uid;
64 gid_t gid;
65 int retval_pipe;
66};
67
e11d277b 68struct run_as_mkdir_data {
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69 const char *path;
70 mode_t mode;
71};
72
e11d277b 73struct run_as_open_data {
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74 const char *path;
75 int flags;
76 mode_t mode;
77};
78
79/*
80 * Create recursively directory using the FULL path.
81 */
82static
83int _mkdir_recursive(void *_data)
84{
e11d277b 85 struct run_as_mkdir_data *data = _data;
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86 const char *path;
87 char *p, tmp[PATH_MAX];
88 struct stat statbuf;
89 mode_t mode;
90 size_t len;
91 int ret;
92
93 path = data->path;
94 mode = data->mode;
95
96 ret = snprintf(tmp, sizeof(tmp), "%s", path);
97 if (ret < 0) {
98 PERROR("snprintf mkdir");
99 goto error;
100 }
101
102 len = ret;
103 if (tmp[len - 1] == '/') {
104 tmp[len - 1] = 0;
105 }
106
107 for (p = tmp + 1; *p; p++) {
108 if (*p == '/') {
109 *p = 0;
110 ret = stat(tmp, &statbuf);
111 if (ret < 0) {
112 ret = mkdir(tmp, mode);
113 if (ret < 0) {
114 if (!(errno == EEXIST)) {
115 PERROR("mkdir recursive");
116 ret = -errno;
117 goto error;
118 }
119 }
120 }
121 *p = '/';
122 }
123 }
124
125 ret = mkdir(tmp, mode);
126 if (ret < 0) {
127 if (!(errno == EEXIST)) {
128 PERROR("mkdir recursive last piece");
129 ret = -errno;
130 } else {
131 ret = 0;
132 }
133 }
134
135error:
136 return ret;
137}
138
139static
140int _mkdir(void *_data)
141{
e11d277b 142 struct run_as_mkdir_data *data = _data;
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143 return mkdir(data->path, data->mode);
144}
145
146static
147int _open(void *_data)
148{
e11d277b 149 struct run_as_open_data *data = _data;
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150 return open(data->path, data->flags, data->mode);
151}
152
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153static
154int child_run_as(void *_data)
155{
6775595e 156 int ret;
c2b75c49 157 struct run_as_data *data = _data;
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158 ssize_t writelen;
159 size_t writeleft, index;
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160 union {
161 int i;
162 char c[sizeof(int)];
163 } sendret;
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164
165 /*
166 * Child: it is safe to drop egid and euid while sharing the
167 * file descriptors with the parent process, since we do not
168 * drop "uid": therefore, the user we are dropping egid/euid to
169 * cannot attach to this process with, e.g. ptrace, nor map this
170 * process memory.
171 */
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172 if (data->gid != getegid()) {
173 ret = setegid(data->gid);
174 if (ret < 0) {
4c462e79 175 PERROR("setegid");
6da9f915 176 return EXIT_FAILURE;
1576d582 177 }
c2b75c49 178 }
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179 if (data->uid != geteuid()) {
180 ret = seteuid(data->uid);
181 if (ret < 0) {
4c462e79 182 PERROR("seteuid");
6da9f915 183 return EXIT_FAILURE;
1576d582 184 }
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185 }
186 /*
187 * Also set umask to 0 for mkdir executable bit.
188 */
189 umask(0);
190 sendret.i = (*data->cmd)(data->data);
191 /* send back return value */
192 writeleft = sizeof(sendret);
193 index = 0;
194 do {
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195 do {
196 writelen = write(data->retval_pipe, &sendret.c[index],
197 writeleft);
198 } while (writelen < 0 && errno == EINTR);
c2b75c49 199 if (writelen < 0) {
4c462e79 200 PERROR("write");
6da9f915 201 return EXIT_FAILURE;
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202 }
203 writeleft -= writelen;
204 index += writelen;
205 } while (writeleft > 0);
6da9f915 206 return EXIT_SUCCESS;
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207}
208
60b6c79c 209static
2d85a600 210int run_as_clone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
60b6c79c 211{
c2b75c49 212 struct run_as_data run_as_data;
60b6c79c 213 int ret = 0;
c2b75c49 214 int status;
60b6c79c 215 pid_t pid;
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216 int retval_pipe[2];
217 ssize_t readlen, readleft, index;
d5bd7573 218 void *child_stack;
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219 union {
220 int i;
221 char c[sizeof(int)];
222 } retval;
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223
224 /*
225 * If we are non-root, we can only deal with our own uid.
226 */
227 if (geteuid() != 0) {
228 if (uid != geteuid()) {
229 ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)",
230 uid, geteuid());
231 return -EPERM;
232 }
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233 }
234
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235 ret = pipe(retval_pipe);
236 if (ret < 0) {
4c462e79 237 PERROR("pipe");
def5e0e8 238 retval.i = ret;
60b6c79c 239 goto end;
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240 }
241 run_as_data.data = data;
242 run_as_data.cmd = cmd;
243 run_as_data.uid = uid;
244 run_as_data.gid = gid;
245 run_as_data.retval_pipe = retval_pipe[1]; /* write end */
e11d277b 246 child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE,
d5bd7573 247 PROT_WRITE | PROT_READ,
0756d557 248 MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | LTTNG_MAP_STACK,
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249 -1, 0);
250 if (child_stack == MAP_FAILED) {
4c462e79 251 PERROR("mmap");
def5e0e8 252 retval.i = -ENOMEM;
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253 goto close_pipe;
254 }
255 /*
256 * Pointing to the middle of the stack to support architectures
257 * where the stack grows up (HPPA).
258 */
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259 pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2),
260 &run_as_data);
c2b75c49 261 if (pid < 0) {
4c462e79 262 PERROR("clone");
def5e0e8 263 retval.i = pid;
d5bd7573 264 goto unmap_stack;
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265 }
266 /* receive return value */
267 readleft = sizeof(retval);
268 index = 0;
269 do {
270 readlen = read(retval_pipe[0], &retval.c[index], readleft);
271 if (readlen < 0) {
4c462e79 272 PERROR("read");
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273 ret = -1;
274 break;
60b6c79c 275 }
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276 readleft -= readlen;
277 index += readlen;
278 } while (readleft > 0);
279
280 /*
281 * Parent: wait for child to return, in which case the
282 * shared memory map will have been created.
283 */
47fb7563 284 pid = waitpid(pid, &status, 0);
c2b75c49 285 if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
4c462e79 286 PERROR("wait");
def5e0e8 287 retval.i = -1;
60b6c79c 288 }
d5bd7573 289unmap_stack:
e11d277b 290 ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE);
d5bd7573 291 if (ret < 0) {
4c462e79 292 PERROR("munmap");
def5e0e8 293 retval.i = ret;
d5bd7573 294 }
c2b75c49 295close_pipe:
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296 ret = close(retval_pipe[0]);
297 if (ret) {
298 PERROR("close");
299 }
300 ret = close(retval_pipe[1]);
301 if (ret) {
302 PERROR("close");
303 }
60b6c79c 304end:
c2b75c49 305 return retval.i;
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306}
307
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308/*
309 * To be used on setups where gdb has issues debugging programs using
310 * clone/rfork. Note that this is for debuging ONLY, and should not be
311 * considered secure.
312 */
313static
314int run_as_noclone(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
315{
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316 int ret;
317 mode_t old_mask;
318
319 old_mask = umask(0);
320 ret = cmd(data);
321 umask(old_mask);
322
323 return ret;
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324}
325
326static
327int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid)
328{
329 if (!getenv("LTTNG_DEBUG_NOCLONE")) {
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330 int ret;
331
2d85a600 332 DBG("Using run_as_clone");
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333 pthread_mutex_lock(&lttng_libc_state_lock);
334 ret = run_as_clone(cmd, data, uid, gid);
335 pthread_mutex_unlock(&lttng_libc_state_lock);
336 return ret;
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337 } else {
338 DBG("Using run_as_noclone");
339 return run_as_noclone(cmd, data, uid, gid);
340 }
341}
342
32dd26fb 343__attribute__((visibility("hidden")))
e11d277b 344int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c 345{
e11d277b 346 struct run_as_mkdir_data data;
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347
348 DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d",
349 path, mode, uid, gid);
350 data.path = path;
351 data.mode = mode;
352 return run_as(_mkdir_recursive, &data, uid, gid);
353}
354
32dd26fb 355__attribute__((visibility("hidden")))
e11d277b 356int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid)
60b6c79c 357{
e11d277b 358 struct run_as_mkdir_data data;
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359
360 DBG3("mkdir() %s with mode %d for uid %d and gid %d",
361 path, mode, uid, gid);
362 data.path = path;
363 data.mode = mode;
364 return run_as(_mkdir, &data, uid, gid);
365}
366
367/*
368 * Note: open_run_as is currently not working. We'd need to pass the fd
369 * opened in the child to the parent.
370 */
32dd26fb 371__attribute__((visibility("hidden")))
e11d277b 372int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid)
60b6c79c 373{
e11d277b 374 struct run_as_open_data data;
c2b75c49 375
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376 DBG3("open() %s with flags %X mode %d for uid %d and gid %d",
377 path, flags, mode, uid, gid);
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378 data.path = path;
379 data.flags = flags;
380 data.mode = mode;
381 return run_as(_open, &data, uid, gid);
60b6c79c 382}
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