Commit | Line | Data |
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60b6c79c MD |
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 it | |
6 | * under the terms of the GNU General Public License as published by the Free | |
7 | * Software Foundation; only version 2 of the License. | |
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 with | |
15 | * this program; if not, write to the Free Software Foundation, Inc., 59 Temple | |
16 | * Place - Suite 330, Boston, MA 02111-1307, 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> | |
c2b75c49 | 30 | #include <sched.h> |
730389d9 | 31 | #include <sys/signal.h> |
60b6c79c | 32 | |
db758600 | 33 | #include <common/error.h> |
730389d9 DG |
34 | #include <common/compat/mman.h> |
35 | #include <common/compat/clone.h> | |
60b6c79c | 36 | |
0857097f DG |
37 | #include "runas.h" |
38 | ||
e11d277b | 39 | #define RUNAS_CHILD_STACK_SIZE 10485760 |
c2b75c49 | 40 | |
0756d557 MD |
41 | #ifdef __FreeBSD__ |
42 | /* FreeBSD MAP_STACK always return -ENOMEM */ | |
43 | #define LTTNG_MAP_STACK 0 | |
44 | #else | |
45 | #define LTTNG_MAP_STACK MAP_STACK | |
059e1d3d MD |
46 | #endif |
47 | ||
a5ae566a | 48 | #ifndef MAP_GROWSDOWN |
edb025e8 | 49 | #define MAP_GROWSDOWN 0 |
a5ae566a MD |
50 | #endif |
51 | ||
52 | #ifndef MAP_ANONYMOUS | |
53 | #define MAP_ANONYMOUS MAP_ANON | |
54 | #endif | |
55 | ||
c2b75c49 MD |
56 | struct run_as_data { |
57 | int (*cmd)(void *data); | |
58 | void *data; | |
59 | uid_t uid; | |
60 | gid_t gid; | |
61 | int retval_pipe; | |
62 | }; | |
63 | ||
e11d277b | 64 | struct run_as_mkdir_data { |
60b6c79c MD |
65 | const char *path; |
66 | mode_t mode; | |
67 | }; | |
68 | ||
e11d277b | 69 | struct run_as_open_data { |
60b6c79c MD |
70 | const char *path; |
71 | int flags; | |
72 | mode_t mode; | |
73 | }; | |
74 | ||
75 | /* | |
76 | * Create recursively directory using the FULL path. | |
77 | */ | |
78 | static | |
79 | int _mkdir_recursive(void *_data) | |
80 | { | |
e11d277b | 81 | struct run_as_mkdir_data *data = _data; |
60b6c79c MD |
82 | const char *path; |
83 | char *p, tmp[PATH_MAX]; | |
84 | struct stat statbuf; | |
85 | mode_t mode; | |
86 | size_t len; | |
87 | int ret; | |
88 | ||
89 | path = data->path; | |
90 | mode = data->mode; | |
91 | ||
92 | ret = snprintf(tmp, sizeof(tmp), "%s", path); | |
93 | if (ret < 0) { | |
94 | PERROR("snprintf mkdir"); | |
95 | goto error; | |
96 | } | |
97 | ||
98 | len = ret; | |
99 | if (tmp[len - 1] == '/') { | |
100 | tmp[len - 1] = 0; | |
101 | } | |
102 | ||
103 | for (p = tmp + 1; *p; p++) { | |
104 | if (*p == '/') { | |
105 | *p = 0; | |
106 | ret = stat(tmp, &statbuf); | |
107 | if (ret < 0) { | |
108 | ret = mkdir(tmp, mode); | |
109 | if (ret < 0) { | |
110 | if (!(errno == EEXIST)) { | |
111 | PERROR("mkdir recursive"); | |
112 | ret = -errno; | |
113 | goto error; | |
114 | } | |
115 | } | |
116 | } | |
117 | *p = '/'; | |
118 | } | |
119 | } | |
120 | ||
121 | ret = mkdir(tmp, mode); | |
122 | if (ret < 0) { | |
123 | if (!(errno == EEXIST)) { | |
124 | PERROR("mkdir recursive last piece"); | |
125 | ret = -errno; | |
126 | } else { | |
127 | ret = 0; | |
128 | } | |
129 | } | |
130 | ||
131 | error: | |
132 | return ret; | |
133 | } | |
134 | ||
135 | static | |
136 | int _mkdir(void *_data) | |
137 | { | |
e11d277b | 138 | struct run_as_mkdir_data *data = _data; |
60b6c79c MD |
139 | return mkdir(data->path, data->mode); |
140 | } | |
141 | ||
142 | static | |
143 | int _open(void *_data) | |
144 | { | |
e11d277b | 145 | struct run_as_open_data *data = _data; |
60b6c79c MD |
146 | return open(data->path, data->flags, data->mode); |
147 | } | |
148 | ||
c2b75c49 MD |
149 | static |
150 | int child_run_as(void *_data) | |
151 | { | |
152 | struct run_as_data *data = _data; | |
153 | size_t writelen, writeleft, index; | |
154 | union { | |
155 | int i; | |
156 | char c[sizeof(int)]; | |
157 | } sendret; | |
158 | int ret; | |
159 | ||
160 | /* | |
161 | * Child: it is safe to drop egid and euid while sharing the | |
162 | * file descriptors with the parent process, since we do not | |
163 | * drop "uid": therefore, the user we are dropping egid/euid to | |
164 | * cannot attach to this process with, e.g. ptrace, nor map this | |
165 | * process memory. | |
166 | */ | |
1576d582 MD |
167 | if (data->gid != getegid()) { |
168 | ret = setegid(data->gid); | |
169 | if (ret < 0) { | |
170 | perror("setegid"); | |
6da9f915 | 171 | return EXIT_FAILURE; |
1576d582 | 172 | } |
c2b75c49 | 173 | } |
1576d582 MD |
174 | if (data->uid != geteuid()) { |
175 | ret = seteuid(data->uid); | |
176 | if (ret < 0) { | |
177 | perror("seteuid"); | |
6da9f915 | 178 | return EXIT_FAILURE; |
1576d582 | 179 | } |
c2b75c49 MD |
180 | } |
181 | /* | |
182 | * Also set umask to 0 for mkdir executable bit. | |
183 | */ | |
184 | umask(0); | |
185 | sendret.i = (*data->cmd)(data->data); | |
186 | /* send back return value */ | |
187 | writeleft = sizeof(sendret); | |
188 | index = 0; | |
189 | do { | |
190 | writelen = write(data->retval_pipe, &sendret.c[index], | |
191 | writeleft); | |
192 | if (writelen < 0) { | |
193 | perror("write"); | |
6da9f915 | 194 | return EXIT_FAILURE; |
c2b75c49 MD |
195 | } |
196 | writeleft -= writelen; | |
197 | index += writelen; | |
198 | } while (writeleft > 0); | |
6da9f915 | 199 | return EXIT_SUCCESS; |
c2b75c49 MD |
200 | } |
201 | ||
60b6c79c MD |
202 | static |
203 | int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid) | |
204 | { | |
c2b75c49 | 205 | struct run_as_data run_as_data; |
60b6c79c | 206 | int ret = 0; |
c2b75c49 | 207 | int status; |
60b6c79c | 208 | pid_t pid; |
c2b75c49 MD |
209 | int retval_pipe[2]; |
210 | ssize_t readlen, readleft, index; | |
d5bd7573 | 211 | void *child_stack; |
c2b75c49 MD |
212 | union { |
213 | int i; | |
214 | char c[sizeof(int)]; | |
215 | } retval; | |
60b6c79c MD |
216 | |
217 | /* | |
218 | * If we are non-root, we can only deal with our own uid. | |
219 | */ | |
220 | if (geteuid() != 0) { | |
221 | if (uid != geteuid()) { | |
222 | ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)", | |
223 | uid, geteuid()); | |
224 | return -EPERM; | |
225 | } | |
60b6c79c MD |
226 | } |
227 | ||
c2b75c49 MD |
228 | ret = pipe(retval_pipe); |
229 | if (ret < 0) { | |
230 | perror("pipe"); | |
def5e0e8 | 231 | retval.i = ret; |
60b6c79c | 232 | goto end; |
c2b75c49 MD |
233 | } |
234 | run_as_data.data = data; | |
235 | run_as_data.cmd = cmd; | |
236 | run_as_data.uid = uid; | |
237 | run_as_data.gid = gid; | |
238 | run_as_data.retval_pipe = retval_pipe[1]; /* write end */ | |
e11d277b | 239 | child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE, |
d5bd7573 | 240 | PROT_WRITE | PROT_READ, |
0756d557 | 241 | MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | LTTNG_MAP_STACK, |
d5bd7573 MD |
242 | -1, 0); |
243 | if (child_stack == MAP_FAILED) { | |
244 | perror("mmap"); | |
def5e0e8 | 245 | retval.i = -ENOMEM; |
d5bd7573 MD |
246 | goto close_pipe; |
247 | } | |
248 | /* | |
249 | * Pointing to the middle of the stack to support architectures | |
250 | * where the stack grows up (HPPA). | |
251 | */ | |
89831a74 MD |
252 | pid = lttng_clone_files(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2), |
253 | &run_as_data); | |
c2b75c49 MD |
254 | if (pid < 0) { |
255 | perror("clone"); | |
def5e0e8 | 256 | retval.i = pid; |
d5bd7573 | 257 | goto unmap_stack; |
c2b75c49 MD |
258 | } |
259 | /* receive return value */ | |
260 | readleft = sizeof(retval); | |
261 | index = 0; | |
262 | do { | |
263 | readlen = read(retval_pipe[0], &retval.c[index], readleft); | |
264 | if (readlen < 0) { | |
265 | perror("read"); | |
266 | ret = -1; | |
267 | break; | |
60b6c79c | 268 | } |
c2b75c49 MD |
269 | readleft -= readlen; |
270 | index += readlen; | |
271 | } while (readleft > 0); | |
272 | ||
273 | /* | |
274 | * Parent: wait for child to return, in which case the | |
275 | * shared memory map will have been created. | |
276 | */ | |
47fb7563 | 277 | pid = waitpid(pid, &status, 0); |
c2b75c49 MD |
278 | if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { |
279 | perror("wait"); | |
def5e0e8 | 280 | retval.i = -1; |
60b6c79c | 281 | } |
d5bd7573 | 282 | unmap_stack: |
e11d277b | 283 | ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE); |
d5bd7573 MD |
284 | if (ret < 0) { |
285 | perror("munmap"); | |
def5e0e8 | 286 | retval.i = ret; |
d5bd7573 | 287 | } |
c2b75c49 MD |
288 | close_pipe: |
289 | close(retval_pipe[0]); | |
290 | close(retval_pipe[1]); | |
60b6c79c | 291 | end: |
c2b75c49 | 292 | return retval.i; |
60b6c79c MD |
293 | } |
294 | ||
e11d277b | 295 | int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid) |
60b6c79c | 296 | { |
e11d277b | 297 | struct run_as_mkdir_data data; |
60b6c79c MD |
298 | |
299 | DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d", | |
300 | path, mode, uid, gid); | |
301 | data.path = path; | |
302 | data.mode = mode; | |
303 | return run_as(_mkdir_recursive, &data, uid, gid); | |
304 | } | |
305 | ||
e11d277b | 306 | int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid) |
60b6c79c | 307 | { |
e11d277b | 308 | struct run_as_mkdir_data data; |
60b6c79c MD |
309 | |
310 | DBG3("mkdir() %s with mode %d for uid %d and gid %d", | |
311 | path, mode, uid, gid); | |
312 | data.path = path; | |
313 | data.mode = mode; | |
314 | return run_as(_mkdir, &data, uid, gid); | |
315 | } | |
316 | ||
317 | /* | |
318 | * Note: open_run_as is currently not working. We'd need to pass the fd | |
319 | * opened in the child to the parent. | |
320 | */ | |
e11d277b | 321 | int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid) |
60b6c79c | 322 | { |
e11d277b | 323 | struct run_as_open_data data; |
c2b75c49 | 324 | |
47fb7563 MD |
325 | DBG3("open() %s with flags %X mode %d for uid %d and gid %d", |
326 | path, flags, mode, uid, gid); | |
60b6c79c MD |
327 | data.path = path; |
328 | data.flags = flags; | |
329 | data.mode = mode; | |
330 | return run_as(_open, &data, uid, gid); | |
60b6c79c | 331 | } |