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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" |
ffc227c9 | 20 | #include "log.h" |
15a5e950 | 21 | #include "path-util.h" |
ffc227c9 | 22 | #include "selinux-util.h" |
15a5e950 | 23 | #include "stdio-util.h" |
5b12334d | 24 | #include "strv.h" |
15a5e950 | 25 | #include "util.h" |
e2417e41 | 26 | |
cad45ba1 | 27 | static bool initialized = false; |
e2417e41 | 28 | |
5b12334d LP |
29 | struct audit_info { |
30 | sd_bus_creds *creds; | |
e2417e41 | 31 | const char *path; |
5b12334d | 32 | const char *cmdline; |
e2417e41 DW |
33 | }; |
34 | ||
e2417e41 DW |
35 | /* |
36 | Any time an access gets denied this callback will be called | |
dec23413 | 37 | with the audit data. We then need to just copy the audit data into the msgbuf. |
e2417e41 | 38 | */ |
cad45ba1 LP |
39 | static int audit_callback( |
40 | void *auditdata, | |
41 | security_class_t cls, | |
42 | char *msgbuf, | |
43 | size_t msgbufsize) { | |
44 | ||
5b12334d LP |
45 | const struct audit_info *audit = auditdata; |
46 | uid_t uid = 0, login_uid = 0; | |
47 | gid_t gid = 0; | |
5ffa8c81 ZJS |
48 | char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; |
49 | char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; | |
50 | char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a"; | |
5b12334d | 51 | |
dec23413 | 52 | if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0) |
5ffa8c81 | 53 | xsprintf(login_uid_buf, UID_FMT, login_uid); |
05bae4a6 | 54 | if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0) |
5ffa8c81 | 55 | xsprintf(uid_buf, UID_FMT, uid); |
05bae4a6 | 56 | if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0) |
5ffa8c81 | 57 | xsprintf(gid_buf, GID_FMT, gid); |
cad45ba1 | 58 | |
e2417e41 | 59 | snprintf(msgbuf, msgbufsize, |
dec23413 ZJS |
60 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s", |
61 | login_uid_buf, uid_buf, gid_buf, | |
5b12334d LP |
62 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", |
63 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : ""); | |
d67227c8 | 64 | |
e2417e41 DW |
65 | return 0; |
66 | } | |
67 | ||
17af49f2 ZJS |
68 | static int callback_type_to_priority(int type) { |
69 | switch(type) { | |
c04754bc LP |
70 | |
71 | case SELINUX_ERROR: | |
72 | return LOG_ERR; | |
73 | ||
74 | case SELINUX_WARNING: | |
75 | return LOG_WARNING; | |
76 | ||
77 | case SELINUX_INFO: | |
78 | return LOG_INFO; | |
79 | ||
17af49f2 | 80 | case SELINUX_AVC: |
c04754bc LP |
81 | default: |
82 | return LOG_NOTICE; | |
17af49f2 ZJS |
83 | } |
84 | } | |
85 | ||
e2417e41 | 86 | /* |
17af49f2 ZJS |
87 | libselinux uses this callback when access gets denied or other |
88 | events happen. If audit is turned on, messages will be reported | |
89 | using audit netlink, otherwise they will be logged using the usual | |
90 | channels. | |
91 | ||
92 | Code copied from dbus and modified. | |
e2417e41 | 93 | */ |
44b601bc | 94 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 | 95 | va_list ap; |
c8a806f2 | 96 | const char *fmt2; |
e2417e41 | 97 | |
349cc4a5 | 98 | #if HAVE_AUDIT |
17af49f2 ZJS |
99 | int fd; |
100 | ||
101 | fd = get_audit_fd(); | |
102 | ||
103 | if (fd >= 0) { | |
ace188cf LP |
104 | _cleanup_free_ char *buf = NULL; |
105 | int r; | |
e2417e41 | 106 | |
5b12334d | 107 | va_start(ap, fmt); |
ace188cf | 108 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 109 | va_end(ap); |
cad45ba1 | 110 | |
ace188cf | 111 | if (r >= 0) { |
17af49f2 | 112 | audit_log_user_avc_message(fd, AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); |
ace188cf LP |
113 | return 0; |
114 | } | |
e2417e41 DW |
115 | } |
116 | #endif | |
5b12334d | 117 | |
c8a806f2 ZJS |
118 | fmt2 = strjoina("selinux: ", fmt); |
119 | ||
5b12334d | 120 | va_start(ap, fmt); |
032b7541 ZJS |
121 | #pragma GCC diagnostic push |
122 | #pragma GCC diagnostic ignored "-Wformat-nonliteral" | |
123 | log_internalv(LOG_AUTH | callback_type_to_priority(type), | |
124 | 0, __FILE__, __LINE__, __FUNCTION__, | |
125 | fmt2, ap); | |
126 | #pragma GCC diagnostic pop | |
e2417e41 | 127 | va_end(ap); |
cad45ba1 | 128 | |
e2417e41 DW |
129 | return 0; |
130 | } | |
131 | ||
6344f3e2 | 132 | static int access_init(sd_bus_error *error) { |
e2417e41 | 133 | |
6344f3e2 LP |
134 | if (!mac_selinux_use()) |
135 | return 0; | |
e2417e41 | 136 | |
6344f3e2 LP |
137 | if (initialized) |
138 | return 1; | |
cad45ba1 | 139 | |
6344f3e2 LP |
140 | if (avc_open(NULL, 0) != 0) { |
141 | int enforce, saved_errno = errno; | |
e2417e41 | 142 | |
6344f3e2 LP |
143 | enforce = security_getenforce(); |
144 | log_full_errno(enforce != 0 ? LOG_ERR : LOG_WARNING, saved_errno, "Failed to open the SELinux AVC: %m"); | |
e2417e41 | 145 | |
6344f3e2 LP |
146 | /* If enforcement isn't on, then let's suppress this |
147 | * error, and just don't do any AVC checks. The | |
148 | * warning we printed is hence all the admin will | |
149 | * see. */ | |
150 | if (enforce == 0) | |
151 | return 0; | |
e2417e41 | 152 | |
6344f3e2 LP |
153 | /* Return an access denied error, if we couldn't load |
154 | * the AVC but enforcing mode was on, or we couldn't | |
155 | * determine whether it is one. */ | |
156 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to open the SELinux AVC: %s", strerror(saved_errno)); | |
157 | } | |
718db961 | 158 | |
6344f3e2 LP |
159 | selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) audit_callback); |
160 | selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) log_callback); | |
e2417e41 | 161 | |
cad45ba1 | 162 | initialized = true; |
6344f3e2 | 163 | return 1; |
e2417e41 DW |
164 | } |
165 | ||
e2417e41 DW |
166 | /* |
167 | This function communicates with the kernel to check whether or not it should | |
168 | allow the access. | |
169 | If the machine is in permissive mode it will return ok. Audit messages will | |
170 | still be generated if the access would be denied in enforcing mode. | |
171 | */ | |
8a188de9 | 172 | int mac_selinux_generic_access_check( |
718db961 | 173 | sd_bus_message *message, |
cad45ba1 LP |
174 | const char *path, |
175 | const char *permission, | |
718db961 | 176 | sd_bus_error *error) { |
cad45ba1 | 177 | |
4afd3348 | 178 | _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL; |
5b12334d LP |
179 | const char *tclass = NULL, *scon = NULL; |
180 | struct audit_info audit_info = {}; | |
181 | _cleanup_free_ char *cl = NULL; | |
2ed96880 | 182 | char *fcon = NULL; |
5b12334d | 183 | char **cmdline = NULL; |
718db961 | 184 | int r = 0; |
c3090674 | 185 | |
cad45ba1 LP |
186 | assert(message); |
187 | assert(permission); | |
188 | assert(error); | |
189 | ||
6344f3e2 LP |
190 | r = access_init(error); |
191 | if (r <= 0) | |
ffc227c9 LP |
192 | return r; |
193 | ||
5b12334d LP |
194 | r = sd_bus_query_sender_creds( |
195 | message, | |
05bae4a6 | 196 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 197 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
198 | SD_BUS_CREDS_SELINUX_CONTEXT| |
199 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
200 | &creds); |
201 | if (r < 0) | |
202 | goto finish; | |
e2417e41 | 203 | |
0f514420 LP |
204 | /* The SELinux context is something we really should have |
205 | * gotten directly from the message or sender, and not be an | |
206 | * augmented field. If it was augmented we cannot use it for | |
207 | * authorization, since this is racy and vulnerable. Let's add | |
208 | * an extra check, just in case, even though this really | |
209 | * shouldn't be possible. */ | |
210 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); | |
211 | ||
5b12334d | 212 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 213 | if (r < 0) |
e2417e41 | 214 | goto finish; |
cad45ba1 | 215 | |
e2417e41 | 216 | if (path) { |
718db961 LP |
217 | /* Get the file context of the unit file */ |
218 | ||
24154879 | 219 | r = getfilecon_raw(path, &fcon); |
e2417e41 | 220 | if (r < 0) { |
718db961 | 221 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path); |
e2417e41 DW |
222 | goto finish; |
223 | } | |
224 | ||
718db961 | 225 | tclass = "service"; |
e2417e41 | 226 | } else { |
24154879 | 227 | r = getcon_raw(&fcon); |
e2417e41 | 228 | if (r < 0) { |
718db961 | 229 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context."); |
e2417e41 DW |
230 | goto finish; |
231 | } | |
718db961 LP |
232 | |
233 | tclass = "system"; | |
e2417e41 DW |
234 | } |
235 | ||
5b12334d LP |
236 | sd_bus_creds_get_cmdline(creds, &cmdline); |
237 | cl = strv_join(cmdline, " "); | |
238 | ||
239 | audit_info.creds = creds; | |
240 | audit_info.path = path; | |
241 | audit_info.cmdline = cl; | |
e2417e41 | 242 | |
236f83af | 243 | r = selinux_check_access(scon, fcon, tclass, permission, &audit_info); |
718db961 LP |
244 | if (r < 0) |
245 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access."); | |
e2417e41 | 246 | |
5b12334d | 247 | 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 | 248 | |
e2417e41 | 249 | finish: |
e2417e41 DW |
250 | freecon(fcon); |
251 | ||
5b12334d | 252 | if (r < 0 && security_getenforce() != 1) { |
718db961 | 253 | sd_bus_error_free(error); |
e2417e41 DW |
254 | r = 0; |
255 | } | |
256 | ||
257 | return r; | |
6344f3e2 LP |
258 | } |
259 | ||
8a188de9 | 260 | #else |
6344f3e2 LP |
261 | |
262 | int mac_selinux_generic_access_check( | |
263 | sd_bus_message *message, | |
264 | const char *path, | |
265 | const char *permission, | |
266 | sd_bus_error *error) { | |
267 | ||
8a188de9 | 268 | return 0; |
e2417e41 | 269 | } |
6344f3e2 LP |
270 | |
271 | #endif |