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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
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 TA |
9 | #include <selinux/selinux.h> |
10 | #include <stdio.h> | |
349cc4a5 | 11 | #if HAVE_AUDIT |
e2417e41 DW |
12 | #include <libaudit.h> |
13 | #endif | |
ffc227c9 | 14 | |
718db961 | 15 | #include "sd-bus.h" |
15a5e950 | 16 | |
b5efdb8a | 17 | #include "alloc-util.h" |
15a5e950 | 18 | #include "audit-fd.h" |
718db961 | 19 | #include "bus-util.h" |
4bbccb02 | 20 | #include "errno-util.h" |
ca78ad1d | 21 | #include "format-util.h" |
ffc227c9 | 22 | #include "log.h" |
15a5e950 | 23 | #include "path-util.h" |
ffc227c9 | 24 | #include "selinux-util.h" |
15a5e950 | 25 | #include "stdio-util.h" |
5b12334d | 26 | #include "strv.h" |
15a5e950 | 27 | #include "util.h" |
e2417e41 | 28 | |
cad45ba1 | 29 | static bool initialized = false; |
e2417e41 | 30 | |
5b12334d LP |
31 | struct audit_info { |
32 | sd_bus_creds *creds; | |
e2417e41 | 33 | const char *path; |
5b12334d | 34 | const char *cmdline; |
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 | |
e2417e41 | 61 | snprintf(msgbuf, msgbufsize, |
dec23413 ZJS |
62 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s", |
63 | login_uid_buf, uid_buf, gid_buf, | |
5b12334d LP |
64 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", |
65 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : ""); | |
d67227c8 | 66 | |
e2417e41 DW |
67 | return 0; |
68 | } | |
69 | ||
17af49f2 ZJS |
70 | static int callback_type_to_priority(int type) { |
71 | switch(type) { | |
c04754bc LP |
72 | |
73 | case SELINUX_ERROR: | |
74 | return LOG_ERR; | |
75 | ||
76 | case SELINUX_WARNING: | |
77 | return LOG_WARNING; | |
78 | ||
79 | case SELINUX_INFO: | |
80 | return LOG_INFO; | |
81 | ||
17af49f2 | 82 | case SELINUX_AVC: |
c04754bc LP |
83 | default: |
84 | return LOG_NOTICE; | |
17af49f2 ZJS |
85 | } |
86 | } | |
87 | ||
e2417e41 | 88 | /* |
17af49f2 ZJS |
89 | libselinux uses this callback when access gets denied or other |
90 | events happen. If audit is turned on, messages will be reported | |
91 | using audit netlink, otherwise they will be logged using the usual | |
92 | channels. | |
93 | ||
94 | Code copied from dbus and modified. | |
e2417e41 | 95 | */ |
44b601bc | 96 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 | 97 | va_list ap; |
c8a806f2 | 98 | const char *fmt2; |
e2417e41 | 99 | |
349cc4a5 | 100 | #if HAVE_AUDIT |
17af49f2 ZJS |
101 | int fd; |
102 | ||
103 | fd = get_audit_fd(); | |
104 | ||
105 | if (fd >= 0) { | |
ace188cf LP |
106 | _cleanup_free_ char *buf = NULL; |
107 | int r; | |
e2417e41 | 108 | |
5b12334d | 109 | va_start(ap, fmt); |
ace188cf | 110 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 111 | va_end(ap); |
cad45ba1 | 112 | |
ace188cf | 113 | if (r >= 0) { |
6227fc14 MS |
114 | if (type == SELINUX_AVC) |
115 | audit_log_user_avc_message(get_audit_fd(), AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); | |
116 | else if (type == SELINUX_ERROR) | |
117 | audit_log_user_avc_message(get_audit_fd(), AUDIT_USER_SELINUX_ERR, buf, NULL, NULL, NULL, 0); | |
118 | ||
ace188cf LP |
119 | return 0; |
120 | } | |
e2417e41 DW |
121 | } |
122 | #endif | |
5b12334d | 123 | |
c8a806f2 ZJS |
124 | fmt2 = strjoina("selinux: ", fmt); |
125 | ||
5b12334d | 126 | va_start(ap, fmt); |
032b7541 ZJS |
127 | #pragma GCC diagnostic push |
128 | #pragma GCC diagnostic ignored "-Wformat-nonliteral" | |
129 | log_internalv(LOG_AUTH | callback_type_to_priority(type), | |
62c6bbbc | 130 | 0, PROJECT_FILE, __LINE__, __FUNCTION__, |
032b7541 ZJS |
131 | fmt2, ap); |
132 | #pragma GCC diagnostic pop | |
e2417e41 | 133 | va_end(ap); |
cad45ba1 | 134 | |
e2417e41 DW |
135 | return 0; |
136 | } | |
137 | ||
6344f3e2 | 138 | static int access_init(sd_bus_error *error) { |
e2417e41 | 139 | |
6344f3e2 LP |
140 | if (!mac_selinux_use()) |
141 | return 0; | |
e2417e41 | 142 | |
6344f3e2 LP |
143 | if (initialized) |
144 | return 1; | |
cad45ba1 | 145 | |
6344f3e2 LP |
146 | if (avc_open(NULL, 0) != 0) { |
147 | int enforce, saved_errno = errno; | |
e2417e41 | 148 | |
6344f3e2 LP |
149 | enforce = security_getenforce(); |
150 | log_full_errno(enforce != 0 ? 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. */ | |
156 | if (enforce == 0) | |
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; |
5b12334d LP |
185 | const char *tclass = NULL, *scon = NULL; |
186 | struct audit_info audit_info = {}; | |
187 | _cleanup_free_ char *cl = NULL; | |
2ed96880 | 188 | char *fcon = NULL; |
5b12334d | 189 | char **cmdline = NULL; |
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 | ||
5b12334d LP |
200 | r = sd_bus_query_sender_creds( |
201 | message, | |
05bae4a6 | 202 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 203 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
204 | SD_BUS_CREDS_SELINUX_CONTEXT| |
205 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
206 | &creds); |
207 | if (r < 0) | |
208 | goto finish; | |
e2417e41 | 209 | |
0f514420 LP |
210 | /* The SELinux context is something we really should have |
211 | * gotten directly from the message or sender, and not be an | |
212 | * augmented field. If it was augmented we cannot use it for | |
213 | * authorization, since this is racy and vulnerable. Let's add | |
214 | * an extra check, just in case, even though this really | |
215 | * shouldn't be possible. */ | |
216 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); | |
217 | ||
5b12334d | 218 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 219 | if (r < 0) |
e2417e41 | 220 | goto finish; |
cad45ba1 | 221 | |
e2417e41 | 222 | if (path) { |
718db961 LP |
223 | /* Get the file context of the unit file */ |
224 | ||
24154879 | 225 | r = getfilecon_raw(path, &fcon); |
e2417e41 | 226 | if (r < 0) { |
718db961 | 227 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path); |
e2417e41 DW |
228 | goto finish; |
229 | } | |
230 | ||
718db961 | 231 | tclass = "service"; |
e2417e41 | 232 | } else { |
24154879 | 233 | r = getcon_raw(&fcon); |
e2417e41 | 234 | if (r < 0) { |
718db961 | 235 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context."); |
e2417e41 DW |
236 | goto finish; |
237 | } | |
718db961 LP |
238 | |
239 | tclass = "system"; | |
e2417e41 DW |
240 | } |
241 | ||
5b12334d LP |
242 | sd_bus_creds_get_cmdline(creds, &cmdline); |
243 | cl = strv_join(cmdline, " "); | |
244 | ||
245 | audit_info.creds = creds; | |
246 | audit_info.path = path; | |
247 | audit_info.cmdline = cl; | |
e2417e41 | 248 | |
236f83af | 249 | r = selinux_check_access(scon, fcon, tclass, permission, &audit_info); |
718db961 LP |
250 | if (r < 0) |
251 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access."); | |
e2417e41 | 252 | |
5b12334d | 253 | 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 | 254 | |
e2417e41 | 255 | finish: |
e2417e41 DW |
256 | freecon(fcon); |
257 | ||
5b12334d | 258 | if (r < 0 && security_getenforce() != 1) { |
718db961 | 259 | sd_bus_error_free(error); |
e2417e41 DW |
260 | r = 0; |
261 | } | |
262 | ||
263 | return r; | |
6344f3e2 LP |
264 | } |
265 | ||
8a188de9 | 266 | #else |
6344f3e2 LP |
267 | |
268 | int mac_selinux_generic_access_check( | |
269 | sd_bus_message *message, | |
270 | const char *path, | |
271 | const char *permission, | |
272 | sd_bus_error *error) { | |
273 | ||
8a188de9 | 274 | return 0; |
e2417e41 | 275 | } |
6344f3e2 LP |
276 | |
277 | #endif |