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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 | 34 | #include "sd-bus.h" |
15a5e950 | 35 | |
b5efdb8a | 36 | #include "alloc-util.h" |
15a5e950 | 37 | #include "audit-fd.h" |
718db961 | 38 | #include "bus-util.h" |
ffc227c9 | 39 | #include "log.h" |
15a5e950 | 40 | #include "path-util.h" |
ffc227c9 | 41 | #include "selinux-util.h" |
15a5e950 | 42 | #include "stdio-util.h" |
5b12334d | 43 | #include "strv.h" |
15a5e950 | 44 | #include "util.h" |
e2417e41 | 45 | |
cad45ba1 | 46 | static bool initialized = false; |
e2417e41 | 47 | |
5b12334d LP |
48 | struct audit_info { |
49 | sd_bus_creds *creds; | |
e2417e41 | 50 | const char *path; |
5b12334d | 51 | const char *cmdline; |
e2417e41 DW |
52 | }; |
53 | ||
e2417e41 DW |
54 | /* |
55 | Any time an access gets denied this callback will be called | |
dec23413 | 56 | with the audit data. We then need to just copy the audit data into the msgbuf. |
e2417e41 | 57 | */ |
cad45ba1 LP |
58 | static int audit_callback( |
59 | void *auditdata, | |
60 | security_class_t cls, | |
61 | char *msgbuf, | |
62 | size_t msgbufsize) { | |
63 | ||
5b12334d LP |
64 | const struct audit_info *audit = auditdata; |
65 | uid_t uid = 0, login_uid = 0; | |
66 | gid_t gid = 0; | |
5ffa8c81 ZJS |
67 | char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; |
68 | char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; | |
69 | char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a"; | |
5b12334d | 70 | |
dec23413 | 71 | if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0) |
5ffa8c81 | 72 | xsprintf(login_uid_buf, UID_FMT, login_uid); |
05bae4a6 | 73 | if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0) |
5ffa8c81 | 74 | xsprintf(uid_buf, UID_FMT, uid); |
05bae4a6 | 75 | if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0) |
5ffa8c81 | 76 | xsprintf(gid_buf, GID_FMT, gid); |
cad45ba1 | 77 | |
e2417e41 | 78 | snprintf(msgbuf, msgbufsize, |
dec23413 ZJS |
79 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s", |
80 | login_uid_buf, uid_buf, gid_buf, | |
5b12334d LP |
81 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", |
82 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : ""); | |
d67227c8 | 83 | |
e2417e41 DW |
84 | return 0; |
85 | } | |
86 | ||
17af49f2 ZJS |
87 | static int callback_type_to_priority(int type) { |
88 | switch(type) { | |
c04754bc LP |
89 | |
90 | case SELINUX_ERROR: | |
91 | return LOG_ERR; | |
92 | ||
93 | case SELINUX_WARNING: | |
94 | return LOG_WARNING; | |
95 | ||
96 | case SELINUX_INFO: | |
97 | return LOG_INFO; | |
98 | ||
17af49f2 | 99 | case SELINUX_AVC: |
c04754bc LP |
100 | default: |
101 | return LOG_NOTICE; | |
17af49f2 ZJS |
102 | } |
103 | } | |
104 | ||
e2417e41 | 105 | /* |
17af49f2 ZJS |
106 | libselinux uses this callback when access gets denied or other |
107 | events happen. If audit is turned on, messages will be reported | |
108 | using audit netlink, otherwise they will be logged using the usual | |
109 | channels. | |
110 | ||
111 | Code copied from dbus and modified. | |
e2417e41 | 112 | */ |
44b601bc | 113 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 DW |
114 | va_list ap; |
115 | ||
e2417e41 | 116 | #ifdef HAVE_AUDIT |
17af49f2 ZJS |
117 | int fd; |
118 | ||
119 | fd = get_audit_fd(); | |
120 | ||
121 | if (fd >= 0) { | |
ace188cf LP |
122 | _cleanup_free_ char *buf = NULL; |
123 | int r; | |
e2417e41 | 124 | |
5b12334d | 125 | va_start(ap, fmt); |
ace188cf | 126 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 127 | va_end(ap); |
cad45ba1 | 128 | |
ace188cf | 129 | if (r >= 0) { |
17af49f2 | 130 | audit_log_user_avc_message(fd, AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); |
ace188cf LP |
131 | return 0; |
132 | } | |
e2417e41 DW |
133 | } |
134 | #endif | |
5b12334d LP |
135 | |
136 | va_start(ap, fmt); | |
17af49f2 ZJS |
137 | log_internalv(LOG_AUTH | callback_type_to_priority(type), |
138 | 0, __FILE__, __LINE__, __FUNCTION__, fmt, ap); | |
e2417e41 | 139 | va_end(ap); |
cad45ba1 | 140 | |
e2417e41 DW |
141 | return 0; |
142 | } | |
143 | ||
144 | /* | |
145 | Function must be called once to initialize the SELinux AVC environment. | |
146 | Sets up callbacks. | |
147 | If you want to cleanup memory you should need to call selinux_access_finish. | |
148 | */ | |
149 | static int access_init(void) { | |
718db961 | 150 | int r = 0; |
e2417e41 | 151 | |
4a62c710 MS |
152 | if (avc_open(NULL, 0)) |
153 | return log_error_errno(errno, "avc_open() failed: %m"); | |
e2417e41 | 154 | |
cad45ba1 LP |
155 | selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) audit_callback); |
156 | selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) log_callback); | |
e2417e41 | 157 | |
718db961 LP |
158 | if (security_getenforce() < 0){ |
159 | r = -errno; | |
160 | avc_destroy(); | |
161 | } | |
cad45ba1 | 162 | |
e2417e41 DW |
163 | return r; |
164 | } | |
165 | ||
8a188de9 | 166 | static int mac_selinux_access_init(sd_bus_error *error) { |
e2417e41 DW |
167 | int r; |
168 | ||
cad45ba1 | 169 | if (initialized) |
e2417e41 DW |
170 | return 0; |
171 | ||
6baa7db0 | 172 | if (!mac_selinux_use()) |
718db961 LP |
173 | return 0; |
174 | ||
175 | r = access_init(); | |
176 | if (r < 0) | |
177 | return sd_bus_error_set(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to initialize SELinux."); | |
e2417e41 | 178 | |
cad45ba1 | 179 | initialized = true; |
e2417e41 DW |
180 | return 0; |
181 | } | |
8a188de9 | 182 | #endif |
e2417e41 | 183 | |
e2417e41 DW |
184 | /* |
185 | This function communicates with the kernel to check whether or not it should | |
186 | allow the access. | |
187 | If the machine is in permissive mode it will return ok. Audit messages will | |
188 | still be generated if the access would be denied in enforcing mode. | |
189 | */ | |
8a188de9 | 190 | int mac_selinux_generic_access_check( |
718db961 | 191 | sd_bus_message *message, |
cad45ba1 LP |
192 | const char *path, |
193 | const char *permission, | |
718db961 | 194 | sd_bus_error *error) { |
cad45ba1 | 195 | |
8a188de9 | 196 | #ifdef HAVE_SELINUX |
5b12334d LP |
197 | _cleanup_bus_creds_unref_ sd_bus_creds *creds = NULL; |
198 | const char *tclass = NULL, *scon = NULL; | |
199 | struct audit_info audit_info = {}; | |
200 | _cleanup_free_ char *cl = NULL; | |
201 | security_context_t fcon = NULL; | |
202 | char **cmdline = NULL; | |
718db961 | 203 | int r = 0; |
c3090674 | 204 | |
cad45ba1 LP |
205 | assert(message); |
206 | assert(permission); | |
207 | assert(error); | |
208 | ||
6baa7db0 | 209 | if (!mac_selinux_use()) |
cad45ba1 LP |
210 | return 0; |
211 | ||
8a188de9 | 212 | r = mac_selinux_access_init(error); |
ffc227c9 LP |
213 | if (r < 0) |
214 | return r; | |
215 | ||
5b12334d LP |
216 | r = sd_bus_query_sender_creds( |
217 | message, | |
05bae4a6 | 218 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 219 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
220 | SD_BUS_CREDS_SELINUX_CONTEXT| |
221 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
222 | &creds); |
223 | if (r < 0) | |
224 | goto finish; | |
e2417e41 | 225 | |
0f514420 LP |
226 | /* The SELinux context is something we really should have |
227 | * gotten directly from the message or sender, and not be an | |
228 | * augmented field. If it was augmented we cannot use it for | |
229 | * authorization, since this is racy and vulnerable. Let's add | |
230 | * an extra check, just in case, even though this really | |
231 | * shouldn't be possible. */ | |
232 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); | |
233 | ||
5b12334d | 234 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 235 | if (r < 0) |
e2417e41 | 236 | goto finish; |
cad45ba1 | 237 | |
e2417e41 | 238 | if (path) { |
718db961 LP |
239 | /* Get the file context of the unit file */ |
240 | ||
24154879 | 241 | r = getfilecon_raw(path, &fcon); |
e2417e41 | 242 | if (r < 0) { |
718db961 | 243 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path); |
e2417e41 DW |
244 | goto finish; |
245 | } | |
246 | ||
718db961 | 247 | tclass = "service"; |
e2417e41 | 248 | } else { |
24154879 | 249 | r = getcon_raw(&fcon); |
e2417e41 | 250 | if (r < 0) { |
718db961 | 251 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context."); |
e2417e41 DW |
252 | goto finish; |
253 | } | |
718db961 LP |
254 | |
255 | tclass = "system"; | |
e2417e41 DW |
256 | } |
257 | ||
5b12334d LP |
258 | sd_bus_creds_get_cmdline(creds, &cmdline); |
259 | cl = strv_join(cmdline, " "); | |
260 | ||
261 | audit_info.creds = creds; | |
262 | audit_info.path = path; | |
263 | audit_info.cmdline = cl; | |
e2417e41 | 264 | |
236f83af | 265 | r = selinux_check_access(scon, fcon, tclass, permission, &audit_info); |
718db961 LP |
266 | if (r < 0) |
267 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access."); | |
e2417e41 | 268 | |
5b12334d | 269 | 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 | 270 | |
e2417e41 | 271 | finish: |
e2417e41 DW |
272 | freecon(fcon); |
273 | ||
5b12334d | 274 | if (r < 0 && security_getenforce() != 1) { |
718db961 | 275 | sd_bus_error_free(error); |
e2417e41 DW |
276 | r = 0; |
277 | } | |
278 | ||
279 | return r; | |
8a188de9 WC |
280 | #else |
281 | return 0; | |
282 | #endif | |
e2417e41 | 283 | } |