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 | ||
0857097f DG |
35 | #include "runas.h" |
36 | ||
e11d277b | 37 | #define RUNAS_CHILD_STACK_SIZE 10485760 |
c2b75c49 MD |
38 | |
39 | struct run_as_data { | |
40 | int (*cmd)(void *data); | |
41 | void *data; | |
42 | uid_t uid; | |
43 | gid_t gid; | |
44 | int retval_pipe; | |
45 | }; | |
46 | ||
e11d277b | 47 | struct run_as_mkdir_data { |
60b6c79c MD |
48 | const char *path; |
49 | mode_t mode; | |
50 | }; | |
51 | ||
e11d277b | 52 | struct run_as_open_data { |
60b6c79c MD |
53 | const char *path; |
54 | int flags; | |
55 | mode_t mode; | |
56 | }; | |
57 | ||
58 | /* | |
59 | * Create recursively directory using the FULL path. | |
60 | */ | |
61 | static | |
62 | int _mkdir_recursive(void *_data) | |
63 | { | |
e11d277b | 64 | struct run_as_mkdir_data *data = _data; |
60b6c79c MD |
65 | const char *path; |
66 | char *p, tmp[PATH_MAX]; | |
67 | struct stat statbuf; | |
68 | mode_t mode; | |
69 | size_t len; | |
70 | int ret; | |
71 | ||
72 | path = data->path; | |
73 | mode = data->mode; | |
74 | ||
75 | ret = snprintf(tmp, sizeof(tmp), "%s", path); | |
76 | if (ret < 0) { | |
77 | PERROR("snprintf mkdir"); | |
78 | goto error; | |
79 | } | |
80 | ||
81 | len = ret; | |
82 | if (tmp[len - 1] == '/') { | |
83 | tmp[len - 1] = 0; | |
84 | } | |
85 | ||
86 | for (p = tmp + 1; *p; p++) { | |
87 | if (*p == '/') { | |
88 | *p = 0; | |
89 | ret = stat(tmp, &statbuf); | |
90 | if (ret < 0) { | |
91 | ret = mkdir(tmp, mode); | |
92 | if (ret < 0) { | |
93 | if (!(errno == EEXIST)) { | |
94 | PERROR("mkdir recursive"); | |
95 | ret = -errno; | |
96 | goto error; | |
97 | } | |
98 | } | |
99 | } | |
100 | *p = '/'; | |
101 | } | |
102 | } | |
103 | ||
104 | ret = mkdir(tmp, mode); | |
105 | if (ret < 0) { | |
106 | if (!(errno == EEXIST)) { | |
107 | PERROR("mkdir recursive last piece"); | |
108 | ret = -errno; | |
109 | } else { | |
110 | ret = 0; | |
111 | } | |
112 | } | |
113 | ||
114 | error: | |
115 | return ret; | |
116 | } | |
117 | ||
118 | static | |
119 | int _mkdir(void *_data) | |
120 | { | |
e11d277b | 121 | struct run_as_mkdir_data *data = _data; |
60b6c79c MD |
122 | return mkdir(data->path, data->mode); |
123 | } | |
124 | ||
125 | static | |
126 | int _open(void *_data) | |
127 | { | |
e11d277b | 128 | struct run_as_open_data *data = _data; |
60b6c79c MD |
129 | return open(data->path, data->flags, data->mode); |
130 | } | |
131 | ||
c2b75c49 MD |
132 | static |
133 | int child_run_as(void *_data) | |
134 | { | |
135 | struct run_as_data *data = _data; | |
136 | size_t writelen, writeleft, index; | |
137 | union { | |
138 | int i; | |
139 | char c[sizeof(int)]; | |
140 | } sendret; | |
141 | int ret; | |
142 | ||
143 | /* | |
144 | * Child: it is safe to drop egid and euid while sharing the | |
145 | * file descriptors with the parent process, since we do not | |
146 | * drop "uid": therefore, the user we are dropping egid/euid to | |
147 | * cannot attach to this process with, e.g. ptrace, nor map this | |
148 | * process memory. | |
149 | */ | |
1576d582 MD |
150 | if (data->gid != getegid()) { |
151 | ret = setegid(data->gid); | |
152 | if (ret < 0) { | |
153 | perror("setegid"); | |
6da9f915 | 154 | return EXIT_FAILURE; |
1576d582 | 155 | } |
c2b75c49 | 156 | } |
1576d582 MD |
157 | if (data->uid != geteuid()) { |
158 | ret = seteuid(data->uid); | |
159 | if (ret < 0) { | |
160 | perror("seteuid"); | |
6da9f915 | 161 | return EXIT_FAILURE; |
1576d582 | 162 | } |
c2b75c49 MD |
163 | } |
164 | /* | |
165 | * Also set umask to 0 for mkdir executable bit. | |
166 | */ | |
167 | umask(0); | |
168 | sendret.i = (*data->cmd)(data->data); | |
169 | /* send back return value */ | |
170 | writeleft = sizeof(sendret); | |
171 | index = 0; | |
172 | do { | |
173 | writelen = write(data->retval_pipe, &sendret.c[index], | |
174 | writeleft); | |
175 | if (writelen < 0) { | |
176 | perror("write"); | |
6da9f915 | 177 | return EXIT_FAILURE; |
c2b75c49 MD |
178 | } |
179 | writeleft -= writelen; | |
180 | index += writelen; | |
181 | } while (writeleft > 0); | |
6da9f915 | 182 | return EXIT_SUCCESS; |
c2b75c49 MD |
183 | } |
184 | ||
60b6c79c MD |
185 | static |
186 | int run_as(int (*cmd)(void *data), void *data, uid_t uid, gid_t gid) | |
187 | { | |
c2b75c49 | 188 | struct run_as_data run_as_data; |
60b6c79c | 189 | int ret = 0; |
c2b75c49 | 190 | int status; |
60b6c79c | 191 | pid_t pid; |
c2b75c49 MD |
192 | int retval_pipe[2]; |
193 | ssize_t readlen, readleft, index; | |
d5bd7573 | 194 | void *child_stack; |
c2b75c49 MD |
195 | union { |
196 | int i; | |
197 | char c[sizeof(int)]; | |
198 | } retval; | |
60b6c79c MD |
199 | |
200 | /* | |
201 | * If we are non-root, we can only deal with our own uid. | |
202 | */ | |
203 | if (geteuid() != 0) { | |
204 | if (uid != geteuid()) { | |
205 | ERR("Client (%d)/Server (%d) UID mismatch (and sessiond is not root)", | |
206 | uid, geteuid()); | |
207 | return -EPERM; | |
208 | } | |
60b6c79c MD |
209 | } |
210 | ||
c2b75c49 MD |
211 | ret = pipe(retval_pipe); |
212 | if (ret < 0) { | |
213 | perror("pipe"); | |
60b6c79c | 214 | goto end; |
c2b75c49 MD |
215 | } |
216 | run_as_data.data = data; | |
217 | run_as_data.cmd = cmd; | |
218 | run_as_data.uid = uid; | |
219 | run_as_data.gid = gid; | |
220 | run_as_data.retval_pipe = retval_pipe[1]; /* write end */ | |
e11d277b | 221 | child_stack = mmap(NULL, RUNAS_CHILD_STACK_SIZE, |
d5bd7573 MD |
222 | PROT_WRITE | PROT_READ, |
223 | MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS | MAP_STACK, | |
224 | -1, 0); | |
225 | if (child_stack == MAP_FAILED) { | |
226 | perror("mmap"); | |
227 | ret = -ENOMEM; | |
228 | goto close_pipe; | |
229 | } | |
230 | /* | |
231 | * Pointing to the middle of the stack to support architectures | |
232 | * where the stack grows up (HPPA). | |
233 | */ | |
e11d277b | 234 | pid = clone(child_run_as, child_stack + (RUNAS_CHILD_STACK_SIZE / 2), |
9beed4cb | 235 | CLONE_FILES | SIGCHLD, |
d5bd7573 | 236 | &run_as_data, NULL); |
c2b75c49 MD |
237 | if (pid < 0) { |
238 | perror("clone"); | |
239 | ret = pid; | |
d5bd7573 | 240 | goto unmap_stack; |
c2b75c49 MD |
241 | } |
242 | /* receive return value */ | |
243 | readleft = sizeof(retval); | |
244 | index = 0; | |
245 | do { | |
246 | readlen = read(retval_pipe[0], &retval.c[index], readleft); | |
247 | if (readlen < 0) { | |
248 | perror("read"); | |
249 | ret = -1; | |
250 | break; | |
60b6c79c | 251 | } |
c2b75c49 MD |
252 | readleft -= readlen; |
253 | index += readlen; | |
254 | } while (readleft > 0); | |
255 | ||
256 | /* | |
257 | * Parent: wait for child to return, in which case the | |
258 | * shared memory map will have been created. | |
259 | */ | |
47fb7563 | 260 | pid = waitpid(pid, &status, 0); |
c2b75c49 MD |
261 | if (pid < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) { |
262 | perror("wait"); | |
263 | ret = -1; | |
60b6c79c | 264 | } |
d5bd7573 | 265 | unmap_stack: |
e11d277b | 266 | ret = munmap(child_stack, RUNAS_CHILD_STACK_SIZE); |
d5bd7573 MD |
267 | if (ret < 0) { |
268 | perror("munmap"); | |
269 | } | |
c2b75c49 MD |
270 | close_pipe: |
271 | close(retval_pipe[0]); | |
272 | close(retval_pipe[1]); | |
60b6c79c | 273 | end: |
c2b75c49 | 274 | return retval.i; |
60b6c79c MD |
275 | } |
276 | ||
e11d277b | 277 | int run_as_mkdir_recursive(const char *path, mode_t mode, uid_t uid, gid_t gid) |
60b6c79c | 278 | { |
e11d277b | 279 | struct run_as_mkdir_data data; |
60b6c79c MD |
280 | |
281 | DBG3("mkdir() recursive %s with mode %d for uid %d and gid %d", | |
282 | path, mode, uid, gid); | |
283 | data.path = path; | |
284 | data.mode = mode; | |
285 | return run_as(_mkdir_recursive, &data, uid, gid); | |
286 | } | |
287 | ||
e11d277b | 288 | int run_as_mkdir(const char *path, mode_t mode, uid_t uid, gid_t gid) |
60b6c79c | 289 | { |
e11d277b | 290 | struct run_as_mkdir_data data; |
60b6c79c MD |
291 | |
292 | DBG3("mkdir() %s with mode %d for uid %d and gid %d", | |
293 | path, mode, uid, gid); | |
294 | data.path = path; | |
295 | data.mode = mode; | |
296 | return run_as(_mkdir, &data, uid, gid); | |
297 | } | |
298 | ||
299 | /* | |
300 | * Note: open_run_as is currently not working. We'd need to pass the fd | |
301 | * opened in the child to the parent. | |
302 | */ | |
e11d277b | 303 | int run_as_open(const char *path, int flags, mode_t mode, uid_t uid, gid_t gid) |
60b6c79c | 304 | { |
e11d277b | 305 | struct run_as_open_data data; |
c2b75c49 | 306 | |
47fb7563 MD |
307 | DBG3("open() %s with flags %X mode %d for uid %d and gid %d", |
308 | path, flags, mode, uid, gid); | |
60b6c79c MD |
309 | data.path = path; |
310 | data.flags = flags; | |
311 | data.mode = mode; | |
312 | return run_as(_open, &data, uid, gid); | |
60b6c79c | 313 | } |