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e2417e41 DW |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2012 Dan Walsh | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
03e22642 KS |
9 | under the terms of the GNU Lesser General Public License as published by |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
e2417e41 DW |
11 | (at your option) any later version. |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
03e22642 | 16 | Lesser General Public License for more details. |
e2417e41 | 17 | |
03e22642 | 18 | You should have received a copy of the GNU Lesser General Public License |
e2417e41 DW |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. |
20 | ***/ | |
21 | ||
e2417e41 DW |
22 | #include "selinux-access.h" |
23 | ||
24 | #ifdef HAVE_SELINUX | |
e2417e41 DW |
25 | |
26 | #include <stdio.h> | |
e2417e41 DW |
27 | #include <errno.h> |
28 | #include <selinux/selinux.h> | |
29 | #include <selinux/avc.h> | |
30 | #ifdef HAVE_AUDIT | |
31 | #include <libaudit.h> | |
32 | #endif | |
ffc227c9 | 33 | |
718db961 LP |
34 | #include "sd-bus.h" |
35 | #include "bus-util.h" | |
ffc227c9 LP |
36 | #include "util.h" |
37 | #include "log.h" | |
ffc227c9 LP |
38 | #include "selinux-util.h" |
39 | #include "audit-fd.h" | |
5b12334d | 40 | #include "strv.h" |
9fa7c1ae | 41 | #include "path-util.h" |
e2417e41 | 42 | |
cad45ba1 | 43 | static bool initialized = false; |
e2417e41 | 44 | |
5b12334d LP |
45 | struct audit_info { |
46 | sd_bus_creds *creds; | |
e2417e41 | 47 | const char *path; |
5b12334d | 48 | const char *cmdline; |
e2417e41 DW |
49 | }; |
50 | ||
e2417e41 DW |
51 | /* |
52 | Any time an access gets denied this callback will be called | |
dec23413 | 53 | with the audit data. We then need to just copy the audit data into the msgbuf. |
e2417e41 | 54 | */ |
cad45ba1 LP |
55 | static int audit_callback( |
56 | void *auditdata, | |
57 | security_class_t cls, | |
58 | char *msgbuf, | |
59 | size_t msgbufsize) { | |
60 | ||
5b12334d LP |
61 | const struct audit_info *audit = auditdata; |
62 | uid_t uid = 0, login_uid = 0; | |
63 | gid_t gid = 0; | |
5ffa8c81 ZJS |
64 | char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; |
65 | char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; | |
66 | char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a"; | |
5b12334d | 67 | |
dec23413 | 68 | if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0) |
5ffa8c81 | 69 | xsprintf(login_uid_buf, UID_FMT, login_uid); |
05bae4a6 | 70 | if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0) |
5ffa8c81 | 71 | xsprintf(uid_buf, UID_FMT, uid); |
05bae4a6 | 72 | if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0) |
5ffa8c81 | 73 | xsprintf(gid_buf, GID_FMT, gid); |
cad45ba1 | 74 | |
e2417e41 | 75 | snprintf(msgbuf, msgbufsize, |
dec23413 ZJS |
76 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s", |
77 | login_uid_buf, uid_buf, gid_buf, | |
5b12334d LP |
78 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", |
79 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : ""); | |
d67227c8 | 80 | |
e2417e41 DW |
81 | return 0; |
82 | } | |
83 | ||
17af49f2 ZJS |
84 | static int callback_type_to_priority(int type) { |
85 | switch(type) { | |
c04754bc LP |
86 | |
87 | case SELINUX_ERROR: | |
88 | return LOG_ERR; | |
89 | ||
90 | case SELINUX_WARNING: | |
91 | return LOG_WARNING; | |
92 | ||
93 | case SELINUX_INFO: | |
94 | return LOG_INFO; | |
95 | ||
17af49f2 | 96 | case SELINUX_AVC: |
c04754bc LP |
97 | default: |
98 | return LOG_NOTICE; | |
17af49f2 ZJS |
99 | } |
100 | } | |
101 | ||
e2417e41 | 102 | /* |
17af49f2 ZJS |
103 | libselinux uses this callback when access gets denied or other |
104 | events happen. If audit is turned on, messages will be reported | |
105 | using audit netlink, otherwise they will be logged using the usual | |
106 | channels. | |
107 | ||
108 | Code copied from dbus and modified. | |
e2417e41 | 109 | */ |
44b601bc | 110 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 DW |
111 | va_list ap; |
112 | ||
e2417e41 | 113 | #ifdef HAVE_AUDIT |
17af49f2 ZJS |
114 | int fd; |
115 | ||
116 | fd = get_audit_fd(); | |
117 | ||
118 | if (fd >= 0) { | |
ace188cf LP |
119 | _cleanup_free_ char *buf = NULL; |
120 | int r; | |
e2417e41 | 121 | |
5b12334d | 122 | va_start(ap, fmt); |
ace188cf | 123 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 124 | va_end(ap); |
cad45ba1 | 125 | |
ace188cf | 126 | if (r >= 0) { |
17af49f2 | 127 | audit_log_user_avc_message(fd, AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); |
ace188cf LP |
128 | return 0; |
129 | } | |
e2417e41 DW |
130 | } |
131 | #endif | |
5b12334d LP |
132 | |
133 | va_start(ap, fmt); | |
17af49f2 ZJS |
134 | log_internalv(LOG_AUTH | callback_type_to_priority(type), |
135 | 0, __FILE__, __LINE__, __FUNCTION__, fmt, ap); | |
e2417e41 | 136 | va_end(ap); |
cad45ba1 | 137 | |
e2417e41 DW |
138 | return 0; |
139 | } | |
140 | ||
141 | /* | |
142 | Function must be called once to initialize the SELinux AVC environment. | |
143 | Sets up callbacks. | |
144 | If you want to cleanup memory you should need to call selinux_access_finish. | |
145 | */ | |
146 | static int access_init(void) { | |
718db961 | 147 | int r = 0; |
e2417e41 | 148 | |
4a62c710 MS |
149 | if (avc_open(NULL, 0)) |
150 | return log_error_errno(errno, "avc_open() failed: %m"); | |
e2417e41 | 151 | |
cad45ba1 LP |
152 | selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) audit_callback); |
153 | selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) log_callback); | |
e2417e41 | 154 | |
718db961 LP |
155 | if (security_getenforce() < 0){ |
156 | r = -errno; | |
157 | avc_destroy(); | |
158 | } | |
cad45ba1 | 159 | |
e2417e41 DW |
160 | return r; |
161 | } | |
162 | ||
8a188de9 | 163 | static int mac_selinux_access_init(sd_bus_error *error) { |
e2417e41 DW |
164 | int r; |
165 | ||
cad45ba1 | 166 | if (initialized) |
e2417e41 DW |
167 | return 0; |
168 | ||
6baa7db0 | 169 | if (!mac_selinux_use()) |
718db961 LP |
170 | return 0; |
171 | ||
172 | r = access_init(); | |
173 | if (r < 0) | |
174 | return sd_bus_error_set(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to initialize SELinux."); | |
e2417e41 | 175 | |
cad45ba1 | 176 | initialized = true; |
e2417e41 DW |
177 | return 0; |
178 | } | |
8a188de9 | 179 | #endif |
e2417e41 | 180 | |
8a188de9 | 181 | void mac_selinux_access_free(void) { |
718db961 | 182 | |
8a188de9 | 183 | #ifdef HAVE_SELINUX |
ffc227c9 LP |
184 | if (!initialized) |
185 | return; | |
186 | ||
187 | avc_destroy(); | |
188 | initialized = false; | |
8a188de9 | 189 | #endif |
ffc227c9 LP |
190 | } |
191 | ||
e2417e41 DW |
192 | /* |
193 | This function communicates with the kernel to check whether or not it should | |
194 | allow the access. | |
195 | If the machine is in permissive mode it will return ok. Audit messages will | |
196 | still be generated if the access would be denied in enforcing mode. | |
197 | */ | |
8a188de9 | 198 | int mac_selinux_generic_access_check( |
718db961 | 199 | sd_bus_message *message, |
cad45ba1 LP |
200 | const char *path, |
201 | const char *permission, | |
718db961 | 202 | sd_bus_error *error) { |
cad45ba1 | 203 | |
8a188de9 | 204 | #ifdef HAVE_SELINUX |
5b12334d LP |
205 | _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL; |
206 | const char *tclass = NULL, *scon = NULL; | |
207 | struct audit_info audit_info = {}; | |
208 | _cleanup_free_ char *cl = NULL; | |
209 | security_context_t fcon = NULL; | |
210 | char **cmdline = NULL; | |
718db961 | 211 | int r = 0; |
c3090674 | 212 | |
cad45ba1 LP |
213 | assert(message); |
214 | assert(permission); | |
215 | assert(error); | |
216 | ||
6baa7db0 | 217 | if (!mac_selinux_use()) |
cad45ba1 LP |
218 | return 0; |
219 | ||
8a188de9 | 220 | r = mac_selinux_access_init(error); |
ffc227c9 LP |
221 | if (r < 0) |
222 | return r; | |
223 | ||
5b12334d LP |
224 | r = sd_bus_query_sender_creds( |
225 | message, | |
05bae4a6 | 226 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 227 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
228 | SD_BUS_CREDS_SELINUX_CONTEXT| |
229 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
230 | &creds); |
231 | if (r < 0) | |
232 | goto finish; | |
e2417e41 | 233 | |
0f514420 LP |
234 | /* The SELinux context is something we really should have |
235 | * gotten directly from the message or sender, and not be an | |
236 | * augmented field. If it was augmented we cannot use it for | |
237 | * authorization, since this is racy and vulnerable. Let's add | |
238 | * an extra check, just in case, even though this really | |
239 | * shouldn't be possible. */ | |
240 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); | |
241 | ||
5b12334d | 242 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 243 | if (r < 0) |
e2417e41 | 244 | goto finish; |
cad45ba1 | 245 | |
e2417e41 | 246 | if (path) { |
718db961 LP |
247 | /* Get the file context of the unit file */ |
248 | ||
e2417e41 DW |
249 | r = getfilecon(path, &fcon); |
250 | if (r < 0) { | |
718db961 | 251 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path); |
e2417e41 DW |
252 | goto finish; |
253 | } | |
254 | ||
718db961 | 255 | tclass = "service"; |
e2417e41 | 256 | } else { |
e2417e41 DW |
257 | r = getcon(&fcon); |
258 | if (r < 0) { | |
718db961 | 259 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context."); |
e2417e41 DW |
260 | goto finish; |
261 | } | |
718db961 LP |
262 | |
263 | tclass = "system"; | |
e2417e41 DW |
264 | } |
265 | ||
5b12334d LP |
266 | sd_bus_creds_get_cmdline(creds, &cmdline); |
267 | cl = strv_join(cmdline, " "); | |
268 | ||
269 | audit_info.creds = creds; | |
270 | audit_info.path = path; | |
271 | audit_info.cmdline = cl; | |
e2417e41 | 272 | |
236f83af | 273 | r = selinux_check_access(scon, fcon, tclass, permission, &audit_info); |
718db961 LP |
274 | if (r < 0) |
275 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access."); | |
e2417e41 | 276 | |
5b12334d | 277 | log_debug("SELinux access check scon=%s tcon=%s tclass=%s perm=%s path=%s cmdline=%s: %i", scon, fcon, tclass, permission, path, cl, r); |
cad45ba1 | 278 | |
e2417e41 | 279 | finish: |
e2417e41 DW |
280 | freecon(fcon); |
281 | ||
5b12334d | 282 | if (r < 0 && security_getenforce() != 1) { |
718db961 | 283 | sd_bus_error_free(error); |
e2417e41 DW |
284 | r = 0; |
285 | } | |
286 | ||
287 | return r; | |
8a188de9 WC |
288 | #else |
289 | return 0; | |
290 | #endif | |
e2417e41 | 291 | } |