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> |
d5bd7573 | 31 | #include <sys/mman.h> |
60b6c79c MD |
32 | |
33 | #include <lttngerr.h> | |
34 | ||
d5bd7573 | 35 | #define CHILD_STACK_SIZE 10485760 |
c2b75c49 MD |
36 | |
37 | struct run_as_data { | |
38 | int (*cmd)(void *data); | |
39 | void *data; | |
40 | uid_t uid; | |
41 | gid_t gid; | |
42 | int retval_pipe; | |
43 | }; | |
44 | ||
60b6c79c MD |
45 | struct mkdir_data { |
46 | const char *path; | |
47 | mode_t mode; | |
48 | }; | |
49 | ||
50 | struct open_data { | |
51 | const char *path; | |
52 | int flags; | |
53 | mode_t mode; | |
54 | }; | |
55 | ||
56 | /* | |
57 | * Create recursively directory using the FULL path. | |
58 | */ | |
59 | static | |
60 | int _mkdir_recursive(void *_data) | |
61 | { | |
62 | struct mkdir_data *data = _data; | |
63 | const char *path; | |
64 | char *p, tmp[PATH_MAX]; | |
65 | struct stat statbuf; | |
66 | mode_t mode; | |
67 | size_t len; | |
68 | int ret; | |
69 | ||
70 | path = data->path; | |
71 | mode = data->mode; | |
72 | ||
73 | ret = snprintf(tmp, sizeof(tmp), "%s", path); | |
74 | if (ret < 0) { | |
75 | PERROR("snprintf mkdir"); | |
76 | goto error; | |
77 | } | |
78 | ||
79 | len = ret; | |
80 | if (tmp[len - 1] == '/') { | |
81 | tmp[len - 1] = 0; | |
82 | } | |
83 | ||
84 | for (p = tmp + 1; *p; p++) { | |
85 | if (*p == '/') { | |
86 | *p = 0; | |
87 | ret = stat(tmp, &statbuf); | |
88 | if (ret < 0) { | |
89 | ret = mkdir(tmp, mode); | |
90 | if (ret < 0) { | |
91 | if (!(errno == EEXIST)) { | |
92 | PERROR("mkdir recursive"); | |
93 | ret = -errno; | |
94 | goto error; | |
95 | } | |
96 | } | |
97 | } | |
98 | *p = '/'; | |
99 | } | |
100 | } | |
101 | ||
102 | ret = mkdir(tmp, mode); | |
103 | if (ret < 0) { | |
104 | if (!(errno == EEXIST)) { | |
105 | PERROR("mkdir recursive last piece"); | |
106 | ret = -errno; | |
107 | } else { | |
108 | ret = 0; | |
109 | } | |
110 | } | |
111 | ||
112 | error: | |
113 | return ret; | |
114 | } | |
115 | ||
116 | static | |
117 | int _mkdir(void *_data) | |
118 | { | |
119 | struct mkdir_data *data = _data; | |
120 | return mkdir(data->path, data->mode); | |
121 | } | |
122 | ||
123 | static | |
124 | int _open(void *_data) | |
125 | { | |
126 | struct open_data *data = _data; | |
127 | return open(data->path, data->flags, data->mode); | |
128 | } | |
129 | ||
c2b75c49 MD |
130 | static |
131 | int child_run_as(void *_data) | |
132 | { | |
133 | struct run_as_data *data = _data; | |
134 | size_t writelen, writeleft, index; | |
135 | union { | |
136 | int i; | |
137 | char c[sizeof(int)]; | |
138 | } sendret; | |
139 | int ret; | |
140 | ||
141 | /* | |
142 | * Child: it is safe to drop egid and euid while sharing the | |
143 | * file descriptors with the parent process, since we do not | |
144 | * drop "uid": therefore, the user we are dropping egid/euid to | |
145 | * cannot attach to this process with, e.g. ptrace, nor map this | |
146 | * process memory. | |
147 | */ | |
1576d582 MD |
148 | if (data->gid != getegid()) { |
149 | ret = setegid(data->gid); | |
150 | if (ret < 0) { | |
151 | perror("setegid"); | |
6da9f915 | 152 | return EXIT_FAILURE; |
1576d582 | 153 | } |
c2b75c49 | 154 | } |
1576d582 MD |
155 | if (data->uid != geteuid()) { |
156 | ret = seteuid(data->uid); | |
157 | if (ret < 0) { | |
158 | perror("seteuid"); | |
6da9f915 | 159 | return EXIT_FAILURE; |
1576d582 | 160 | } |
c2b75c49 MD |
161 | } |
162 | /* | |
163 | * Also set umask to 0 for mkdir executable bit. | |
164 | */ | |
165 | umask(0); | |
166 | sendret.i = (*data->cmd)(data->data); | |
167 | /* send back return value */ | |
168 | writeleft = sizeof(sendret); | |
169 | index = 0; | |
170 | do { | |
171 | writelen = write(data->retval_pipe, &sendret.c[index], | |
172 | writeleft); | |
173 | if (writelen < 0) { | |
174 | perror("write"); | |
6da9f915 | 175 | return EXIT_FAILURE; |
c2b75c49 MD |
176 | } |
177 | writeleft -= writelen; | |
178 | index += writelen; | |
179 | } while (writeleft > 0); | |
6da9f915 | 180 | return EXIT_SUCCESS; |
c2b75c49 MD |
181 | } |
182 | ||
60b6c79c MD |
183 | static |
184 | int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid) | |
185 | { | |
c2b75c49 | 186 | struct run_as_data run_as_data; |
60b6c79c | 187 | int ret = 0; |
c2b75c49 | 188 | int status; |
60b6c79c | 189 | pid_t pid; |
c2b75c49 MD |
190 | int retval_pipe[2]; |
191 | ssize_t readlen, readleft, index; | |
d5bd7573 | 192 | void *child_stack; |
c2b75c49 MD |
193 | union { |
194 | int i; | |
195 | char c[sizeof(int)]; | |
196 | } retval; | |
60b6c79c MD |
197 | |
198 | /* | |
199 | * If we are non-root, we can only deal with our own uid. | |
200 | */ | |
201 | if (geteuid() != 0) { | |
202 | if (uid != geteuid()) { | |
203 | ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)", | |
204 | uid, geteuid()); | |
205 | return -EPERM; | |
206 | } | |
60b6c79c MD |
207 | } |
208 | ||
c2b75c49 MD |
209 | ret = pipe(retval_pipe); |
210 | if (ret < 0) { | |
211 | perror("pipe"); | |
60b6c79c | 212 | goto end; |
c2b75c49 MD |
213 | } |
214 | run_as_data.data = data; | |
215 | run_as_data.cmd = cmd; | |
216 | run_as_data.uid = uid; | |
217 | run_as_data.gid = gid; | |
218 | run_as_data.retval_pipe = retval_pipe[1]; /* write end */ | |
d5bd7573 MD |
219 | child_stack = mmap(NULL, CHILD_STACK_SIZE, |
220 | PROT_WRITE | PROT_READ, | |
221 | MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | MAP_STACK, | |
222 | -1, 0); | |
223 | if (child_stack == MAP_FAILED) { | |
224 | perror("mmap"); | |
225 | ret = -ENOMEM; | |
226 | goto close_pipe; | |
227 | } | |
228 | /* | |
229 | * Pointing to the middle of the stack to support architectures | |
230 | * where the stack grows up (HPPA). | |
231 | */ | |
232 | pid = clone(child_run_as, child_stack + (CHILD_STACK_SIZE / 2), | |
10d32e93 | 233 | CLONE_FILES | SIGCHLD | CLONE_VM, |
d5bd7573 | 234 | &run_as_data, NULL); |
c2b75c49 MD |
235 | if (pid < 0) { |
236 | perror("clone"); | |
237 | ret = pid; | |
d5bd7573 | 238 | goto unmap_stack; |
c2b75c49 MD |
239 | } |
240 | /* receive return value */ | |
241 | readleft = sizeof(retval); | |
242 | index = 0; | |
243 | do { | |
244 | readlen = read(retval_pipe[0], &retval.c[index], readleft); | |
245 | if (readlen < 0) { | |
246 | perror("read"); | |
247 | ret = -1; | |
248 | break; | |
60b6c79c | 249 | } |
c2b75c49 MD |
250 | readleft -= readlen; |
251 | index += readlen; | |
252 | } while (readleft > 0); | |
253 | ||
254 | /* | |
255 | * Parent: wait for child to return, in which case the | |
256 | * shared memory map will have been created. | |
257 | */ | |
47fb7563 | 258 | pid = waitpid(pid, &status, 0); |
c2b75c49 MD |
259 | if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { |
260 | perror("wait"); | |
261 | ret = -1; | |
60b6c79c | 262 | } |
d5bd7573 MD |
263 | unmap_stack: |
264 | ret = munmap(child_stack, CHILD_STACK_SIZE); | |
265 | if (ret < 0) { | |
266 | perror("munmap"); | |
267 | } | |
c2b75c49 MD |
268 | close_pipe: |
269 | close(retval_pipe[0]); | |
270 | close(retval_pipe[1]); | |
60b6c79c | 271 | end: |
c2b75c49 | 272 | return retval.i; |
60b6c79c MD |
273 | } |
274 | ||
275 | int mkdir_recursive_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid) | |
276 | { | |
277 | struct mkdir_data data; | |
278 | ||
279 | DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d", | |
280 | path, mode, uid, gid); | |
281 | data.path = path; | |
282 | data.mode = mode; | |
283 | return run_as(_mkdir_recursive, &data, uid, gid); | |
284 | } | |
285 | ||
286 | int mkdir_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid) | |
287 | { | |
288 | struct mkdir_data data; | |
289 | ||
290 | DBG3("mkdir() %s with mode %d for uid %d and gid %d", | |
291 | path, mode, uid, gid); | |
292 | data.path = path; | |
293 | data.mode = mode; | |
294 | return run_as(_mkdir, &data, uid, gid); | |
295 | } | |
296 | ||
297 | /* | |
298 | * Note: open_run_as is currently not working. We'd need to pass the fd | |
299 | * opened in the child to the parent. | |
300 | */ | |
301 | int open_run_as(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid) | |
302 | { | |
c2b75c49 MD |
303 | struct open_data data; |
304 | ||
47fb7563 MD |
305 | DBG3("open() %s with flags %X mode %d for uid %d and gid %d", |
306 | path, flags, mode, uid, gid); | |
60b6c79c MD |
307 | data.path = path; |
308 | data.flags = flags; | |
309 | data.mode = mode; | |
310 | return run_as(_open, &data, uid, gid); | |
60b6c79c | 311 | } |