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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; |
f0804759 | 34 | const char *function; |
e2417e41 DW |
35 | }; |
36 | ||
e2417e41 DW |
37 | /* |
38 | Any time an access gets denied this callback will be called | |
dec23413 | 39 | with the audit data. We then need to just copy the audit data into the msgbuf. |
e2417e41 | 40 | */ |
cad45ba1 LP |
41 | static int audit_callback( |
42 | void *auditdata, | |
43 | security_class_t cls, | |
44 | char *msgbuf, | |
45 | size_t msgbufsize) { | |
46 | ||
5b12334d LP |
47 | const struct audit_info *audit = auditdata; |
48 | uid_t uid = 0, login_uid = 0; | |
49 | gid_t gid = 0; | |
5ffa8c81 ZJS |
50 | char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; |
51 | char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; | |
52 | char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a"; | |
5b12334d | 53 | |
dec23413 | 54 | if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0) |
5ffa8c81 | 55 | xsprintf(login_uid_buf, UID_FMT, login_uid); |
05bae4a6 | 56 | if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0) |
5ffa8c81 | 57 | xsprintf(uid_buf, UID_FMT, uid); |
05bae4a6 | 58 | if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0) |
5ffa8c81 | 59 | xsprintf(gid_buf, GID_FMT, gid); |
cad45ba1 | 60 | |
121ed16c | 61 | (void) snprintf(msgbuf, msgbufsize, |
f0804759 | 62 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s%s%s%s", |
121ed16c LB |
63 | login_uid_buf, uid_buf, gid_buf, |
64 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", | |
f0804759 CG |
65 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : "", |
66 | audit->function ? " function=\"" : "", strempty(audit->function), audit->function ? "\"" : ""); | |
d67227c8 | 67 | |
e2417e41 DW |
68 | return 0; |
69 | } | |
70 | ||
17af49f2 | 71 | static int callback_type_to_priority(int type) { |
79893116 | 72 | switch (type) { |
c04754bc LP |
73 | |
74 | case SELINUX_ERROR: | |
75 | return LOG_ERR; | |
76 | ||
77 | case SELINUX_WARNING: | |
78 | return LOG_WARNING; | |
79 | ||
80 | case SELINUX_INFO: | |
81 | return LOG_INFO; | |
82 | ||
17af49f2 | 83 | case SELINUX_AVC: |
c04754bc LP |
84 | default: |
85 | return LOG_NOTICE; | |
17af49f2 ZJS |
86 | } |
87 | } | |
88 | ||
e2417e41 | 89 | /* |
17af49f2 ZJS |
90 | libselinux uses this callback when access gets denied or other |
91 | events happen. If audit is turned on, messages will be reported | |
92 | using audit netlink, otherwise they will be logged using the usual | |
93 | channels. | |
94 | ||
95 | Code copied from dbus and modified. | |
e2417e41 | 96 | */ |
44b601bc | 97 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 | 98 | va_list ap; |
c8a806f2 | 99 | const char *fmt2; |
e2417e41 | 100 | |
349cc4a5 | 101 | #if HAVE_AUDIT |
17af49f2 ZJS |
102 | int fd; |
103 | ||
104 | fd = get_audit_fd(); | |
105 | ||
106 | if (fd >= 0) { | |
ace188cf LP |
107 | _cleanup_free_ char *buf = NULL; |
108 | int r; | |
e2417e41 | 109 | |
5b12334d | 110 | va_start(ap, fmt); |
ace188cf | 111 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 112 | va_end(ap); |
cad45ba1 | 113 | |
ace188cf | 114 | if (r >= 0) { |
6227fc14 MS |
115 | if (type == SELINUX_AVC) |
116 | audit_log_user_avc_message(get_audit_fd(), AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); | |
117 | else if (type == SELINUX_ERROR) | |
118 | audit_log_user_avc_message(get_audit_fd(), AUDIT_USER_SELINUX_ERR, buf, NULL, NULL, NULL, 0); | |
119 | ||
ace188cf LP |
120 | return 0; |
121 | } | |
e2417e41 DW |
122 | } |
123 | #endif | |
5b12334d | 124 | |
c8a806f2 ZJS |
125 | fmt2 = strjoina("selinux: ", fmt); |
126 | ||
5b12334d | 127 | va_start(ap, fmt); |
56e577c6 LP |
128 | |
129 | DISABLE_WARNING_FORMAT_NONLITERAL; | |
032b7541 | 130 | log_internalv(LOG_AUTH | callback_type_to_priority(type), |
7fbae5b7 | 131 | 0, PROJECT_FILE, __LINE__, __func__, |
032b7541 | 132 | fmt2, ap); |
56e577c6 | 133 | REENABLE_WARNING; |
e2417e41 | 134 | va_end(ap); |
cad45ba1 | 135 | |
e2417e41 DW |
136 | return 0; |
137 | } | |
138 | ||
6344f3e2 | 139 | static int access_init(sd_bus_error *error) { |
38553034 | 140 | int r; |
e2417e41 | 141 | |
6344f3e2 LP |
142 | if (!mac_selinux_use()) |
143 | return 0; | |
e2417e41 | 144 | |
6344f3e2 LP |
145 | if (initialized) |
146 | return 1; | |
cad45ba1 | 147 | |
6344f3e2 | 148 | if (avc_open(NULL, 0) != 0) { |
38553034 | 149 | r = -errno; /* Save original errno for later */ |
e2417e41 | 150 | |
38553034 ZJS |
151 | bool enforce = security_getenforce() != 0; |
152 | log_full_errno(enforce ? LOG_ERR : LOG_WARNING, r, "Failed to open the SELinux AVC: %m"); | |
e2417e41 | 153 | |
38553034 ZJS |
154 | /* If enforcement isn't on, then let's suppress this error, and just don't do any AVC checks. |
155 | * The warning we printed is hence all the admin will see. */ | |
257188f8 | 156 | if (!enforce) |
6344f3e2 | 157 | return 0; |
e2417e41 | 158 | |
38553034 ZJS |
159 | /* Return an access denied error based on the original errno, if we couldn't load the AVC but |
160 | * enforcing mode was on, or we couldn't determine whether it is one. */ | |
161 | errno = -r; | |
162 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to open the SELinux AVC: %m"); | |
6344f3e2 | 163 | } |
718db961 | 164 | |
57e70396 CG |
165 | selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) { .func_audit = audit_callback }); |
166 | selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) { .func_log = 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 | */ | |
963438a0 | 178 | int mac_selinux_access_check_internal( |
718db961 | 179 | sd_bus_message *message, |
23e9a7dd LP |
180 | const char *unit_path, |
181 | const char *unit_context, | |
cad45ba1 | 182 | const char *permission, |
f0804759 | 183 | const char *function, |
718db961 | 184 | sd_bus_error *error) { |
cad45ba1 | 185 | |
4afd3348 | 186 | _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL; |
23e9a7dd | 187 | const char *tclass, *scon, *acon; |
5b12334d | 188 | _cleanup_free_ char *cl = NULL; |
cff789b7 | 189 | _cleanup_freecon_ char *fcon = NULL; |
5b12334d | 190 | char **cmdline = NULL; |
194fe322 | 191 | bool enforce; |
718db961 | 192 | int r = 0; |
c3090674 | 193 | |
cad45ba1 LP |
194 | assert(message); |
195 | assert(permission); | |
f0804759 | 196 | assert(function); |
cad45ba1 LP |
197 | assert(error); |
198 | ||
6344f3e2 LP |
199 | r = access_init(error); |
200 | if (r <= 0) | |
ffc227c9 LP |
201 | return r; |
202 | ||
194fe322 | 203 | /* delay call until we checked in `access_init()` if SELinux is actually enabled */ |
fd5e402f | 204 | enforce = mac_selinux_enforcing(); |
194fe322 | 205 | |
5b12334d LP |
206 | r = sd_bus_query_sender_creds( |
207 | message, | |
05bae4a6 | 208 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 209 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
210 | SD_BUS_CREDS_SELINUX_CONTEXT| |
211 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
212 | &creds); |
213 | if (r < 0) | |
cff789b7 | 214 | return r; |
e2417e41 | 215 | |
23e9a7dd LP |
216 | /* The SELinux context is something we really should have gotten directly from the message or sender, |
217 | * and not be an augmented field. If it was augmented we cannot use it for authorization, since this | |
218 | * is racy and vulnerable. Let's add an extra check, just in case, even though this really shouldn't | |
219 | * be possible. */ | |
0f514420 LP |
220 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); |
221 | ||
5b12334d | 222 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 223 | if (r < 0) |
cff789b7 | 224 | return r; |
cad45ba1 | 225 | |
23e9a7dd LP |
226 | if (unit_context) { |
227 | /* Nice! The unit comes with a SELinux context read from the unit file */ | |
228 | acon = unit_context; | |
718db961 | 229 | tclass = "service"; |
e2417e41 | 230 | } else { |
23e9a7dd | 231 | /* If no unit context is known, use our own */ |
cff789b7 ZJS |
232 | if (getcon_raw(&fcon) < 0) { |
233 | r = -errno; | |
cff789b7 | 234 | |
9bf4984a | 235 | log_warning_errno(r, "SELinux getcon_raw() failed%s (perm=%s): %m", |
cff789b7 ZJS |
236 | enforce ? "" : ", ignoring", |
237 | permission); | |
238 | if (!enforce) | |
239 | return 0; | |
240 | ||
62f174cf | 241 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context: %m"); |
e2417e41 | 242 | } |
718db961 | 243 | |
23e9a7dd | 244 | acon = fcon; |
718db961 | 245 | tclass = "system"; |
e2417e41 DW |
246 | } |
247 | ||
5b12334d LP |
248 | sd_bus_creds_get_cmdline(creds, &cmdline); |
249 | cl = strv_join(cmdline, " "); | |
250 | ||
cff789b7 ZJS |
251 | struct audit_info audit_info = { |
252 | .creds = creds, | |
23e9a7dd | 253 | .path = unit_path, |
cff789b7 | 254 | .cmdline = cl, |
f0804759 | 255 | .function = function, |
cff789b7 | 256 | }; |
e2417e41 | 257 | |
23e9a7dd | 258 | r = selinux_check_access(scon, acon, tclass, permission, &audit_info); |
cff789b7 | 259 | if (r < 0) { |
62f174cf | 260 | errno = -(r = errno_or_else(EPERM)); |
e2417e41 | 261 | |
cff789b7 | 262 | if (enforce) |
62f174cf | 263 | sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access: %m"); |
e2417e41 DW |
264 | } |
265 | ||
2669c666 | 266 | log_full_errno_zerook(LOG_DEBUG, r, |
f0804759 | 267 | "SELinux access check scon=%s tcon=%s tclass=%s perm=%s state=%s function=%s path=%s cmdline=%s: %m", |
23e9a7dd | 268 | scon, acon, tclass, permission, enforce ? "enforcing" : "permissive", function, strna(unit_path), strna(empty_to_null(cl))); |
cff789b7 | 269 | return enforce ? r : 0; |
6344f3e2 LP |
270 | } |
271 | ||
fd5e402f | 272 | #else /* HAVE_SELINUX */ |
6344f3e2 | 273 | |
963438a0 | 274 | int mac_selinux_access_check_internal( |
6344f3e2 | 275 | sd_bus_message *message, |
23e9a7dd LP |
276 | const char *unit_path, |
277 | const char *unit_label, | |
6344f3e2 | 278 | const char *permission, |
f0804759 | 279 | const char *function, |
6344f3e2 LP |
280 | sd_bus_error *error) { |
281 | ||
8a188de9 | 282 | return 0; |
e2417e41 | 283 | } |
6344f3e2 | 284 | |
fd5e402f | 285 | #endif /* HAVE_SELINUX */ |