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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> |
60b6c79c MD |
31 | |
32 | #include <lttngerr.h> | |
33 | ||
c2b75c49 MD |
34 | /* |
35 | * We allocate a stack of twice this size and point in the middle of it | |
36 | * to support archs with stack growing up and down. | |
37 | */ | |
38 | #define CHILD_STACK_SIZE 2048 | |
39 | ||
40 | struct run_as_data { | |
41 | int (*cmd)(void *data); | |
42 | void *data; | |
43 | uid_t uid; | |
44 | gid_t gid; | |
45 | int retval_pipe; | |
46 | }; | |
47 | ||
60b6c79c MD |
48 | struct mkdir_data { |
49 | const char *path; | |
50 | mode_t mode; | |
51 | }; | |
52 | ||
53 | struct open_data { | |
54 | const char *path; | |
55 | int flags; | |
56 | mode_t mode; | |
57 | }; | |
58 | ||
59 | /* | |
60 | * Create recursively directory using the FULL path. | |
61 | */ | |
62 | static | |
63 | int _mkdir_recursive(void *_data) | |
64 | { | |
65 | struct mkdir_data *data = _data; | |
66 | const char *path; | |
67 | char *p, tmp[PATH_MAX]; | |
68 | struct stat statbuf; | |
69 | mode_t mode; | |
70 | size_t len; | |
71 | int ret; | |
72 | ||
73 | path = data->path; | |
74 | mode = data->mode; | |
75 | ||
76 | ret = snprintf(tmp, sizeof(tmp), "%s", path); | |
77 | if (ret < 0) { | |
78 | PERROR("snprintf mkdir"); | |
79 | goto error; | |
80 | } | |
81 | ||
82 | len = ret; | |
83 | if (tmp[len - 1] == '/') { | |
84 | tmp[len - 1] = 0; | |
85 | } | |
86 | ||
87 | for (p = tmp + 1; *p; p++) { | |
88 | if (*p == '/') { | |
89 | *p = 0; | |
90 | ret = stat(tmp, &statbuf); | |
91 | if (ret < 0) { | |
92 | ret = mkdir(tmp, mode); | |
93 | if (ret < 0) { | |
94 | if (!(errno == EEXIST)) { | |
95 | PERROR("mkdir recursive"); | |
96 | ret = -errno; | |
97 | goto error; | |
98 | } | |
99 | } | |
100 | } | |
101 | *p = '/'; | |
102 | } | |
103 | } | |
104 | ||
105 | ret = mkdir(tmp, mode); | |
106 | if (ret < 0) { | |
107 | if (!(errno == EEXIST)) { | |
108 | PERROR("mkdir recursive last piece"); | |
109 | ret = -errno; | |
110 | } else { | |
111 | ret = 0; | |
112 | } | |
113 | } | |
114 | ||
115 | error: | |
116 | return ret; | |
117 | } | |
118 | ||
119 | static | |
120 | int _mkdir(void *_data) | |
121 | { | |
122 | struct mkdir_data *data = _data; | |
123 | return mkdir(data->path, data->mode); | |
124 | } | |
125 | ||
126 | static | |
127 | int _open(void *_data) | |
128 | { | |
129 | struct open_data *data = _data; | |
130 | return open(data->path, data->flags, data->mode); | |
131 | } | |
132 | ||
c2b75c49 MD |
133 | static |
134 | int child_run_as(void *_data) | |
135 | { | |
136 | struct run_as_data *data = _data; | |
137 | size_t writelen, writeleft, index; | |
138 | union { | |
139 | int i; | |
140 | char c[sizeof(int)]; | |
141 | } sendret; | |
142 | int ret; | |
143 | ||
144 | /* | |
145 | * Child: it is safe to drop egid and euid while sharing the | |
146 | * file descriptors with the parent process, since we do not | |
147 | * drop "uid": therefore, the user we are dropping egid/euid to | |
148 | * cannot attach to this process with, e.g. ptrace, nor map this | |
149 | * process memory. | |
150 | */ | |
151 | ret = setegid(data->gid); | |
152 | if (ret < 0) { | |
153 | perror("setegid"); | |
154 | exit(EXIT_FAILURE); | |
155 | } | |
156 | ret = seteuid(data->uid); | |
157 | if (ret < 0) { | |
158 | perror("seteuid"); | |
159 | exit(EXIT_FAILURE); | |
160 | } | |
161 | /* | |
162 | * Also set umask to 0 for mkdir executable bit. | |
163 | */ | |
164 | umask(0); | |
165 | sendret.i = (*data->cmd)(data->data); | |
166 | /* send back return value */ | |
167 | writeleft = sizeof(sendret); | |
168 | index = 0; | |
169 | do { | |
170 | writelen = write(data->retval_pipe, &sendret.c[index], | |
171 | writeleft); | |
172 | if (writelen < 0) { | |
173 | perror("write"); | |
174 | exit(EXIT_FAILURE); | |
175 | } | |
176 | writeleft -= writelen; | |
177 | index += writelen; | |
178 | } while (writeleft > 0); | |
179 | ||
180 | exit(EXIT_SUCCESS); | |
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 | char *child_stack; |
191 | int retval_pipe[2]; | |
192 | ssize_t readlen, readleft, index; | |
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 | } | |
207 | return (*cmd)(data); | |
208 | } | |
209 | ||
c2b75c49 MD |
210 | child_stack = malloc(CHILD_STACK_SIZE * 2); |
211 | if (!child_stack) { | |
212 | return -ENOMEM; | |
213 | } | |
214 | ret = pipe(retval_pipe); | |
215 | if (ret < 0) { | |
216 | perror("pipe"); | |
60b6c79c | 217 | goto end; |
c2b75c49 MD |
218 | } |
219 | run_as_data.data = data; | |
220 | run_as_data.cmd = cmd; | |
221 | run_as_data.uid = uid; | |
222 | run_as_data.gid = gid; | |
223 | run_as_data.retval_pipe = retval_pipe[1]; /* write end */ | |
224 | ||
225 | pid = clone(child_run_as, child_stack + CHILD_STACK_SIZE, | |
226 | CLONE_FILES | SIGCHLD, &run_as_data, NULL); | |
227 | if (pid < 0) { | |
228 | perror("clone"); | |
229 | ret = pid; | |
230 | goto close_pipe; | |
231 | } | |
232 | /* receive return value */ | |
233 | readleft = sizeof(retval); | |
234 | index = 0; | |
235 | do { | |
236 | readlen = read(retval_pipe[0], &retval.c[index], readleft); | |
237 | if (readlen < 0) { | |
238 | perror("read"); | |
239 | ret = -1; | |
240 | break; | |
60b6c79c | 241 | } |
c2b75c49 MD |
242 | readleft -= readlen; |
243 | index += readlen; | |
244 | } while (readleft > 0); | |
245 | ||
246 | /* | |
247 | * Parent: wait for child to return, in which case the | |
248 | * shared memory map will have been created. | |
249 | */ | |
250 | pid = wait(&status); | |
251 | if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { | |
252 | perror("wait"); | |
253 | ret = -1; | |
60b6c79c | 254 | } |
c2b75c49 MD |
255 | close_pipe: |
256 | close(retval_pipe[0]); | |
257 | close(retval_pipe[1]); | |
60b6c79c | 258 | end: |
c2b75c49 MD |
259 | free(child_stack); |
260 | return retval.i; | |
60b6c79c MD |
261 | } |
262 | ||
263 | int mkdir_recursive_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid) | |
264 | { | |
265 | struct mkdir_data data; | |
266 | ||
267 | DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d", | |
268 | path, mode, uid, gid); | |
269 | data.path = path; | |
270 | data.mode = mode; | |
271 | return run_as(_mkdir_recursive, &data, uid, gid); | |
272 | } | |
273 | ||
274 | int mkdir_run_as(const char *path, mode_t mode, uid_t uid, gid_t gid) | |
275 | { | |
276 | struct mkdir_data data; | |
277 | ||
278 | DBG3("mkdir() %s with mode %d for uid %d and gid %d", | |
279 | path, mode, uid, gid); | |
280 | data.path = path; | |
281 | data.mode = mode; | |
282 | return run_as(_mkdir, &data, uid, gid); | |
283 | } | |
284 | ||
285 | /* | |
286 | * Note: open_run_as is currently not working. We'd need to pass the fd | |
287 | * opened in the child to the parent. | |
288 | */ | |
289 | int open_run_as(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid) | |
290 | { | |
c2b75c49 MD |
291 | struct open_data data; |
292 | ||
60b6c79c MD |
293 | data.path = path; |
294 | data.flags = flags; | |
295 | data.mode = mode; | |
296 | return run_as(_open, &data, uid, gid); | |
60b6c79c | 297 | } |