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db9ecf05 | 1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
e2417e41 | 2 | |
e2417e41 DW |
3 | #include "selinux-access.h" |
4 | ||
349cc4a5 | 5 | #if HAVE_SELINUX |
e2417e41 | 6 | |
e2417e41 | 7 | #include <errno.h> |
e2417e41 | 8 | #include <selinux/avc.h> |
cf0fbc49 | 9 | #include <selinux/selinux.h> |
349cc4a5 | 10 | #if HAVE_AUDIT |
e2417e41 DW |
11 | #include <libaudit.h> |
12 | #endif | |
ffc227c9 | 13 | |
718db961 | 14 | #include "sd-bus.h" |
15a5e950 | 15 | |
b5efdb8a | 16 | #include "alloc-util.h" |
15a5e950 | 17 | #include "audit-fd.h" |
718db961 | 18 | #include "bus-util.h" |
4bbccb02 | 19 | #include "errno-util.h" |
ca78ad1d | 20 | #include "format-util.h" |
ffc227c9 | 21 | #include "log.h" |
15a5e950 | 22 | #include "path-util.h" |
ffc227c9 | 23 | #include "selinux-util.h" |
15a5e950 | 24 | #include "stdio-util.h" |
5b12334d | 25 | #include "strv.h" |
15a5e950 | 26 | #include "util.h" |
e2417e41 | 27 | |
cad45ba1 | 28 | static bool initialized = false; |
e2417e41 | 29 | |
5b12334d LP |
30 | struct audit_info { |
31 | sd_bus_creds *creds; | |
e2417e41 | 32 | const char *path; |
5b12334d | 33 | const char *cmdline; |
e2417e41 DW |
34 | }; |
35 | ||
e2417e41 DW |
36 | /* |
37 | Any time an access gets denied this callback will be called | |
dec23413 | 38 | with the audit data. We then need to just copy the audit data into the msgbuf. |
e2417e41 | 39 | */ |
cad45ba1 LP |
40 | static int audit_callback( |
41 | void *auditdata, | |
42 | security_class_t cls, | |
43 | char *msgbuf, | |
44 | size_t msgbufsize) { | |
45 | ||
5b12334d LP |
46 | const struct audit_info *audit = auditdata; |
47 | uid_t uid = 0, login_uid = 0; | |
48 | gid_t gid = 0; | |
5ffa8c81 ZJS |
49 | char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; |
50 | char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; | |
51 | char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a"; | |
5b12334d | 52 | |
dec23413 | 53 | if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0) |
5ffa8c81 | 54 | xsprintf(login_uid_buf, UID_FMT, login_uid); |
05bae4a6 | 55 | if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0) |
5ffa8c81 | 56 | xsprintf(uid_buf, UID_FMT, uid); |
05bae4a6 | 57 | if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0) |
5ffa8c81 | 58 | xsprintf(gid_buf, GID_FMT, gid); |
cad45ba1 | 59 | |
e2417e41 | 60 | snprintf(msgbuf, msgbufsize, |
dec23413 ZJS |
61 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s", |
62 | login_uid_buf, uid_buf, gid_buf, | |
5b12334d LP |
63 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", |
64 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : ""); | |
d67227c8 | 65 | |
e2417e41 DW |
66 | return 0; |
67 | } | |
68 | ||
17af49f2 ZJS |
69 | static int callback_type_to_priority(int type) { |
70 | switch(type) { | |
c04754bc LP |
71 | |
72 | case SELINUX_ERROR: | |
73 | return LOG_ERR; | |
74 | ||
75 | case SELINUX_WARNING: | |
76 | return LOG_WARNING; | |
77 | ||
78 | case SELINUX_INFO: | |
79 | return LOG_INFO; | |
80 | ||
17af49f2 | 81 | case SELINUX_AVC: |
c04754bc LP |
82 | default: |
83 | return LOG_NOTICE; | |
17af49f2 ZJS |
84 | } |
85 | } | |
86 | ||
e2417e41 | 87 | /* |
17af49f2 ZJS |
88 | libselinux uses this callback when access gets denied or other |
89 | events happen. If audit is turned on, messages will be reported | |
90 | using audit netlink, otherwise they will be logged using the usual | |
91 | channels. | |
92 | ||
93 | Code copied from dbus and modified. | |
e2417e41 | 94 | */ |
44b601bc | 95 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 | 96 | va_list ap; |
c8a806f2 | 97 | const char *fmt2; |
e2417e41 | 98 | |
349cc4a5 | 99 | #if HAVE_AUDIT |
17af49f2 ZJS |
100 | int fd; |
101 | ||
102 | fd = get_audit_fd(); | |
103 | ||
104 | if (fd >= 0) { | |
ace188cf LP |
105 | _cleanup_free_ char *buf = NULL; |
106 | int r; | |
e2417e41 | 107 | |
5b12334d | 108 | va_start(ap, fmt); |
ace188cf | 109 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 110 | va_end(ap); |
cad45ba1 | 111 | |
ace188cf | 112 | if (r >= 0) { |
6227fc14 MS |
113 | if (type == SELINUX_AVC) |
114 | audit_log_user_avc_message(get_audit_fd(), AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); | |
115 | else if (type == SELINUX_ERROR) | |
116 | audit_log_user_avc_message(get_audit_fd(), AUDIT_USER_SELINUX_ERR, buf, NULL, NULL, NULL, 0); | |
117 | ||
ace188cf LP |
118 | return 0; |
119 | } | |
e2417e41 DW |
120 | } |
121 | #endif | |
5b12334d | 122 | |
c8a806f2 ZJS |
123 | fmt2 = strjoina("selinux: ", fmt); |
124 | ||
5b12334d | 125 | va_start(ap, fmt); |
56e577c6 LP |
126 | |
127 | DISABLE_WARNING_FORMAT_NONLITERAL; | |
032b7541 | 128 | log_internalv(LOG_AUTH | callback_type_to_priority(type), |
62c6bbbc | 129 | 0, PROJECT_FILE, __LINE__, __FUNCTION__, |
032b7541 | 130 | fmt2, ap); |
56e577c6 | 131 | REENABLE_WARNING; |
e2417e41 | 132 | va_end(ap); |
cad45ba1 | 133 | |
e2417e41 DW |
134 | return 0; |
135 | } | |
136 | ||
6344f3e2 | 137 | static int access_init(sd_bus_error *error) { |
e2417e41 | 138 | |
6344f3e2 LP |
139 | if (!mac_selinux_use()) |
140 | return 0; | |
e2417e41 | 141 | |
6344f3e2 LP |
142 | if (initialized) |
143 | return 1; | |
cad45ba1 | 144 | |
6344f3e2 | 145 | if (avc_open(NULL, 0) != 0) { |
257188f8 | 146 | int saved_errno = errno; |
3cd44590 | 147 | bool enforce; |
e2417e41 | 148 | |
3cd44590 | 149 | enforce = security_getenforce() != 0; |
257188f8 | 150 | log_full_errno(enforce ? LOG_ERR : LOG_WARNING, saved_errno, "Failed to open the SELinux AVC: %m"); |
e2417e41 | 151 | |
6344f3e2 LP |
152 | /* If enforcement isn't on, then let's suppress this |
153 | * error, and just don't do any AVC checks. The | |
154 | * warning we printed is hence all the admin will | |
155 | * see. */ | |
257188f8 | 156 | if (!enforce) |
6344f3e2 | 157 | return 0; |
e2417e41 | 158 | |
6344f3e2 LP |
159 | /* Return an access denied error, if we couldn't load |
160 | * the AVC but enforcing mode was on, or we couldn't | |
161 | * determine whether it is one. */ | |
4bbccb02 | 162 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to open the SELinux AVC: %s", strerror_safe(saved_errno)); |
6344f3e2 | 163 | } |
718db961 | 164 | |
6344f3e2 LP |
165 | selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) audit_callback); |
166 | selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) log_callback); | |
e2417e41 | 167 | |
cad45ba1 | 168 | initialized = true; |
6344f3e2 | 169 | return 1; |
e2417e41 DW |
170 | } |
171 | ||
e2417e41 DW |
172 | /* |
173 | This function communicates with the kernel to check whether or not it should | |
174 | allow the access. | |
175 | If the machine is in permissive mode it will return ok. Audit messages will | |
176 | still be generated if the access would be denied in enforcing mode. | |
177 | */ | |
8a188de9 | 178 | int mac_selinux_generic_access_check( |
718db961 | 179 | sd_bus_message *message, |
cad45ba1 LP |
180 | const char *path, |
181 | const char *permission, | |
718db961 | 182 | sd_bus_error *error) { |
cad45ba1 | 183 | |
4afd3348 | 184 | _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL; |
22cd7aab | 185 | const char *tclass, *scon; |
5b12334d | 186 | _cleanup_free_ char *cl = NULL; |
cff789b7 | 187 | _cleanup_freecon_ char *fcon = NULL; |
5b12334d | 188 | char **cmdline = NULL; |
194fe322 | 189 | bool enforce; |
718db961 | 190 | int r = 0; |
c3090674 | 191 | |
cad45ba1 LP |
192 | assert(message); |
193 | assert(permission); | |
194 | assert(error); | |
195 | ||
6344f3e2 LP |
196 | r = access_init(error); |
197 | if (r <= 0) | |
ffc227c9 LP |
198 | return r; |
199 | ||
194fe322 | 200 | /* delay call until we checked in `access_init()` if SELinux is actually enabled */ |
fd5e402f | 201 | enforce = mac_selinux_enforcing(); |
194fe322 | 202 | |
5b12334d LP |
203 | r = sd_bus_query_sender_creds( |
204 | message, | |
05bae4a6 | 205 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 206 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
207 | SD_BUS_CREDS_SELINUX_CONTEXT| |
208 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
209 | &creds); |
210 | if (r < 0) | |
cff789b7 | 211 | return r; |
e2417e41 | 212 | |
0f514420 LP |
213 | /* The SELinux context is something we really should have |
214 | * gotten directly from the message or sender, and not be an | |
215 | * augmented field. If it was augmented we cannot use it for | |
216 | * authorization, since this is racy and vulnerable. Let's add | |
217 | * an extra check, just in case, even though this really | |
218 | * shouldn't be possible. */ | |
219 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); | |
220 | ||
5b12334d | 221 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 222 | if (r < 0) |
cff789b7 | 223 | return r; |
cad45ba1 | 224 | |
e2417e41 | 225 | if (path) { |
718db961 LP |
226 | /* Get the file context of the unit file */ |
227 | ||
cff789b7 ZJS |
228 | if (getfilecon_raw(path, &fcon) < 0) { |
229 | r = -errno; | |
cff789b7 | 230 | |
9bf4984a | 231 | log_warning_errno(r, "SELinux getfilecon_raw() on '%s' failed%s (perm=%s): %m", |
cff789b7 ZJS |
232 | path, |
233 | enforce ? "" : ", ignoring", | |
234 | permission); | |
235 | if (!enforce) | |
236 | return 0; | |
237 | ||
238 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path); | |
e2417e41 DW |
239 | } |
240 | ||
718db961 | 241 | tclass = "service"; |
cff789b7 | 242 | |
e2417e41 | 243 | } else { |
cff789b7 ZJS |
244 | if (getcon_raw(&fcon) < 0) { |
245 | r = -errno; | |
cff789b7 | 246 | |
9bf4984a | 247 | log_warning_errno(r, "SELinux getcon_raw() failed%s (perm=%s): %m", |
cff789b7 ZJS |
248 | enforce ? "" : ", ignoring", |
249 | permission); | |
250 | if (!enforce) | |
251 | return 0; | |
252 | ||
253 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context."); | |
e2417e41 | 254 | } |
718db961 LP |
255 | |
256 | tclass = "system"; | |
e2417e41 DW |
257 | } |
258 | ||
5b12334d LP |
259 | sd_bus_creds_get_cmdline(creds, &cmdline); |
260 | cl = strv_join(cmdline, " "); | |
261 | ||
cff789b7 ZJS |
262 | struct audit_info audit_info = { |
263 | .creds = creds, | |
264 | .path = path, | |
265 | .cmdline = cl, | |
266 | }; | |
e2417e41 | 267 | |
236f83af | 268 | r = selinux_check_access(scon, fcon, tclass, permission, &audit_info); |
cff789b7 ZJS |
269 | if (r < 0) { |
270 | r = errno_or_else(EPERM); | |
e2417e41 | 271 | |
cff789b7 ZJS |
272 | if (enforce) |
273 | sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access."); | |
e2417e41 DW |
274 | } |
275 | ||
1b7d1cae CG |
276 | log_debug_errno(r, "SELinux access check scon=%s tcon=%s tclass=%s perm=%s state=%s path=%s cmdline=%s: %m", |
277 | scon, fcon, tclass, permission, enforce ? "enforcing" : "permissive", path, cl); | |
cff789b7 | 278 | return enforce ? r : 0; |
6344f3e2 LP |
279 | } |
280 | ||
fd5e402f | 281 | #else /* HAVE_SELINUX */ |
6344f3e2 LP |
282 | |
283 | int mac_selinux_generic_access_check( | |
284 | sd_bus_message *message, | |
285 | const char *path, | |
286 | const char *permission, | |
287 | sd_bus_error *error) { | |
288 | ||
8a188de9 | 289 | return 0; |
e2417e41 | 290 | } |
6344f3e2 | 291 | |
fd5e402f | 292 | #endif /* HAVE_SELINUX */ |