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