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53e1b683 | 1 | /* SPDX-License-Identifier: LGPL-2.1+ */ |
e2417e41 DW |
2 | /*** |
3 | This file is part of systemd. | |
4 | ||
5 | Copyright 2012 Dan Walsh | |
e2417e41 DW |
6 | ***/ |
7 | ||
e2417e41 DW |
8 | #include "selinux-access.h" |
9 | ||
349cc4a5 | 10 | #if HAVE_SELINUX |
e2417e41 | 11 | |
e2417e41 | 12 | #include <errno.h> |
e2417e41 | 13 | #include <selinux/avc.h> |
cf0fbc49 TA |
14 | #include <selinux/selinux.h> |
15 | #include <stdio.h> | |
349cc4a5 | 16 | #if HAVE_AUDIT |
e2417e41 DW |
17 | #include <libaudit.h> |
18 | #endif | |
ffc227c9 | 19 | |
718db961 | 20 | #include "sd-bus.h" |
15a5e950 | 21 | |
b5efdb8a | 22 | #include "alloc-util.h" |
15a5e950 | 23 | #include "audit-fd.h" |
718db961 | 24 | #include "bus-util.h" |
ffc227c9 | 25 | #include "log.h" |
15a5e950 | 26 | #include "path-util.h" |
ffc227c9 | 27 | #include "selinux-util.h" |
15a5e950 | 28 | #include "stdio-util.h" |
5b12334d | 29 | #include "strv.h" |
15a5e950 | 30 | #include "util.h" |
e2417e41 | 31 | |
cad45ba1 | 32 | static bool initialized = false; |
e2417e41 | 33 | |
5b12334d LP |
34 | struct audit_info { |
35 | sd_bus_creds *creds; | |
e2417e41 | 36 | const char *path; |
5b12334d | 37 | const char *cmdline; |
e2417e41 DW |
38 | }; |
39 | ||
e2417e41 DW |
40 | /* |
41 | Any time an access gets denied this callback will be called | |
dec23413 | 42 | with the audit data. We then need to just copy the audit data into the msgbuf. |
e2417e41 | 43 | */ |
cad45ba1 LP |
44 | static int audit_callback( |
45 | void *auditdata, | |
46 | security_class_t cls, | |
47 | char *msgbuf, | |
48 | size_t msgbufsize) { | |
49 | ||
5b12334d LP |
50 | const struct audit_info *audit = auditdata; |
51 | uid_t uid = 0, login_uid = 0; | |
52 | gid_t gid = 0; | |
5ffa8c81 ZJS |
53 | char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; |
54 | char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a"; | |
55 | char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a"; | |
5b12334d | 56 | |
dec23413 | 57 | if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0) |
5ffa8c81 | 58 | xsprintf(login_uid_buf, UID_FMT, login_uid); |
05bae4a6 | 59 | if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0) |
5ffa8c81 | 60 | xsprintf(uid_buf, UID_FMT, uid); |
05bae4a6 | 61 | if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0) |
5ffa8c81 | 62 | xsprintf(gid_buf, GID_FMT, gid); |
cad45ba1 | 63 | |
e2417e41 | 64 | snprintf(msgbuf, msgbufsize, |
dec23413 ZJS |
65 | "auid=%s uid=%s gid=%s%s%s%s%s%s%s", |
66 | login_uid_buf, uid_buf, gid_buf, | |
5b12334d LP |
67 | audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "", |
68 | audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : ""); | |
d67227c8 | 69 | |
e2417e41 DW |
70 | return 0; |
71 | } | |
72 | ||
17af49f2 ZJS |
73 | static int callback_type_to_priority(int type) { |
74 | switch(type) { | |
c04754bc LP |
75 | |
76 | case SELINUX_ERROR: | |
77 | return LOG_ERR; | |
78 | ||
79 | case SELINUX_WARNING: | |
80 | return LOG_WARNING; | |
81 | ||
82 | case SELINUX_INFO: | |
83 | return LOG_INFO; | |
84 | ||
17af49f2 | 85 | case SELINUX_AVC: |
c04754bc LP |
86 | default: |
87 | return LOG_NOTICE; | |
17af49f2 ZJS |
88 | } |
89 | } | |
90 | ||
e2417e41 | 91 | /* |
17af49f2 ZJS |
92 | libselinux uses this callback when access gets denied or other |
93 | events happen. If audit is turned on, messages will be reported | |
94 | using audit netlink, otherwise they will be logged using the usual | |
95 | channels. | |
96 | ||
97 | Code copied from dbus and modified. | |
e2417e41 | 98 | */ |
44b601bc | 99 | _printf_(2, 3) static int log_callback(int type, const char *fmt, ...) { |
e2417e41 | 100 | va_list ap; |
c8a806f2 | 101 | const char *fmt2; |
e2417e41 | 102 | |
349cc4a5 | 103 | #if HAVE_AUDIT |
17af49f2 ZJS |
104 | int fd; |
105 | ||
106 | fd = get_audit_fd(); | |
107 | ||
108 | if (fd >= 0) { | |
ace188cf LP |
109 | _cleanup_free_ char *buf = NULL; |
110 | int r; | |
e2417e41 | 111 | |
5b12334d | 112 | va_start(ap, fmt); |
ace188cf | 113 | r = vasprintf(&buf, fmt, ap); |
7f1736f7 | 114 | va_end(ap); |
cad45ba1 | 115 | |
ace188cf | 116 | if (r >= 0) { |
17af49f2 | 117 | audit_log_user_avc_message(fd, AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0); |
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); |
032b7541 ZJS |
126 | #pragma GCC diagnostic push |
127 | #pragma GCC diagnostic ignored "-Wformat-nonliteral" | |
128 | log_internalv(LOG_AUTH | callback_type_to_priority(type), | |
129 | 0, __FILE__, __LINE__, __FUNCTION__, | |
130 | fmt2, ap); | |
131 | #pragma GCC diagnostic pop | |
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 LP |
145 | if (avc_open(NULL, 0) != 0) { |
146 | int enforce, saved_errno = errno; | |
e2417e41 | 147 | |
6344f3e2 LP |
148 | enforce = security_getenforce(); |
149 | log_full_errno(enforce != 0 ? LOG_ERR : LOG_WARNING, saved_errno, "Failed to open the SELinux AVC: %m"); | |
e2417e41 | 150 | |
6344f3e2 LP |
151 | /* If enforcement isn't on, then let's suppress this |
152 | * error, and just don't do any AVC checks. The | |
153 | * warning we printed is hence all the admin will | |
154 | * see. */ | |
155 | if (enforce == 0) | |
156 | return 0; | |
e2417e41 | 157 | |
6344f3e2 LP |
158 | /* Return an access denied error, if we couldn't load |
159 | * the AVC but enforcing mode was on, or we couldn't | |
160 | * determine whether it is one. */ | |
161 | return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to open the SELinux AVC: %s", strerror(saved_errno)); | |
162 | } | |
718db961 | 163 | |
6344f3e2 LP |
164 | selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) audit_callback); |
165 | selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) log_callback); | |
e2417e41 | 166 | |
cad45ba1 | 167 | initialized = true; |
6344f3e2 | 168 | return 1; |
e2417e41 DW |
169 | } |
170 | ||
e2417e41 DW |
171 | /* |
172 | This function communicates with the kernel to check whether or not it should | |
173 | allow the access. | |
174 | If the machine is in permissive mode it will return ok. Audit messages will | |
175 | still be generated if the access would be denied in enforcing mode. | |
176 | */ | |
8a188de9 | 177 | int mac_selinux_generic_access_check( |
718db961 | 178 | sd_bus_message *message, |
cad45ba1 LP |
179 | const char *path, |
180 | const char *permission, | |
718db961 | 181 | sd_bus_error *error) { |
cad45ba1 | 182 | |
4afd3348 | 183 | _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL; |
5b12334d LP |
184 | const char *tclass = NULL, *scon = NULL; |
185 | struct audit_info audit_info = {}; | |
186 | _cleanup_free_ char *cl = NULL; | |
2ed96880 | 187 | char *fcon = NULL; |
5b12334d | 188 | char **cmdline = NULL; |
718db961 | 189 | int r = 0; |
c3090674 | 190 | |
cad45ba1 LP |
191 | assert(message); |
192 | assert(permission); | |
193 | assert(error); | |
194 | ||
6344f3e2 LP |
195 | r = access_init(error); |
196 | if (r <= 0) | |
ffc227c9 LP |
197 | return r; |
198 | ||
5b12334d LP |
199 | r = sd_bus_query_sender_creds( |
200 | message, | |
05bae4a6 | 201 | SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID| |
5b12334d | 202 | SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID| |
8fd00193 LP |
203 | SD_BUS_CREDS_SELINUX_CONTEXT| |
204 | SD_BUS_CREDS_AUGMENT /* get more bits from /proc */, | |
5b12334d LP |
205 | &creds); |
206 | if (r < 0) | |
207 | goto finish; | |
e2417e41 | 208 | |
0f514420 LP |
209 | /* The SELinux context is something we really should have |
210 | * gotten directly from the message or sender, and not be an | |
211 | * augmented field. If it was augmented we cannot use it for | |
212 | * authorization, since this is racy and vulnerable. Let's add | |
213 | * an extra check, just in case, even though this really | |
214 | * shouldn't be possible. */ | |
215 | assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM); | |
216 | ||
5b12334d | 217 | r = sd_bus_creds_get_selinux_context(creds, &scon); |
718db961 | 218 | if (r < 0) |
e2417e41 | 219 | goto finish; |
cad45ba1 | 220 | |
e2417e41 | 221 | if (path) { |
718db961 LP |
222 | /* Get the file context of the unit file */ |
223 | ||
24154879 | 224 | r = getfilecon_raw(path, &fcon); |
e2417e41 | 225 | if (r < 0) { |
718db961 | 226 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path); |
e2417e41 DW |
227 | goto finish; |
228 | } | |
229 | ||
718db961 | 230 | tclass = "service"; |
e2417e41 | 231 | } else { |
24154879 | 232 | r = getcon_raw(&fcon); |
e2417e41 | 233 | if (r < 0) { |
718db961 | 234 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context."); |
e2417e41 DW |
235 | goto finish; |
236 | } | |
718db961 LP |
237 | |
238 | tclass = "system"; | |
e2417e41 DW |
239 | } |
240 | ||
5b12334d LP |
241 | sd_bus_creds_get_cmdline(creds, &cmdline); |
242 | cl = strv_join(cmdline, " "); | |
243 | ||
244 | audit_info.creds = creds; | |
245 | audit_info.path = path; | |
246 | audit_info.cmdline = cl; | |
e2417e41 | 247 | |
236f83af | 248 | r = selinux_check_access(scon, fcon, tclass, permission, &audit_info); |
718db961 LP |
249 | if (r < 0) |
250 | r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access."); | |
e2417e41 | 251 | |
5b12334d | 252 | 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 | 253 | |
e2417e41 | 254 | finish: |
e2417e41 DW |
255 | freecon(fcon); |
256 | ||
5b12334d | 257 | if (r < 0 && security_getenforce() != 1) { |
718db961 | 258 | sd_bus_error_free(error); |
e2417e41 DW |
259 | r = 0; |
260 | } | |
261 | ||
262 | return r; | |
6344f3e2 LP |
263 | } |
264 | ||
8a188de9 | 265 | #else |
6344f3e2 LP |
266 | |
267 | int mac_selinux_generic_access_check( | |
268 | sd_bus_message *message, | |
269 | const char *path, | |
270 | const char *permission, | |
271 | sd_bus_error *error) { | |
272 | ||
8a188de9 | 273 | return 0; |
e2417e41 | 274 | } |
6344f3e2 LP |
275 | |
276 | #endif |