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f47781d8 MP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2014 Lennart Poettering | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include "missing.h" | |
23 | #include "journald-audit.h" | |
e3bff60a | 24 | #include "audit-type.h" |
f47781d8 MP |
25 | |
26 | typedef struct MapField { | |
27 | const char *audit_field; | |
28 | const char *journal_field; | |
29 | int (*map)(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov); | |
30 | } MapField; | |
31 | ||
32 | static int map_simple_field(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) { | |
33 | _cleanup_free_ char *c = NULL; | |
34 | size_t l = 0, allocated = 0; | |
35 | const char *e; | |
36 | ||
37 | assert(field); | |
38 | assert(p); | |
39 | assert(iov); | |
40 | assert(n_iov); | |
41 | ||
42 | l = strlen(field); | |
43 | allocated = l + 1; | |
44 | c = malloc(allocated); | |
45 | if (!c) | |
46 | return -ENOMEM; | |
47 | ||
48 | memcpy(c, field, l); | |
49 | for (e = *p; *e != ' ' && *e != 0; e++) { | |
50 | if (!GREEDY_REALLOC(c, allocated, l+2)) | |
51 | return -ENOMEM; | |
52 | ||
53 | c[l++] = *e; | |
54 | } | |
55 | ||
56 | c[l] = 0; | |
57 | ||
58 | if (!GREEDY_REALLOC(*iov, *n_iov_allocated, *n_iov + 1)) | |
59 | return -ENOMEM; | |
60 | ||
61 | (*iov)[*n_iov].iov_base = c; | |
62 | (*iov)[*n_iov].iov_len = l; | |
63 | (*n_iov) ++; | |
64 | ||
65 | *p = e; | |
66 | c = NULL; | |
67 | ||
68 | return 1; | |
69 | } | |
70 | ||
71 | static int map_string_field_internal(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov, bool filter_printable) { | |
72 | _cleanup_free_ char *c = NULL; | |
73 | const char *s, *e; | |
74 | size_t l; | |
75 | ||
76 | assert(field); | |
77 | assert(p); | |
78 | assert(iov); | |
79 | assert(n_iov); | |
80 | ||
81 | /* The kernel formats string fields in one of two formats. */ | |
82 | ||
83 | if (**p == '"') { | |
84 | /* Normal quoted syntax */ | |
85 | s = *p + 1; | |
86 | e = strchr(s, '"'); | |
87 | if (!e) | |
88 | return 0; | |
89 | ||
90 | l = strlen(field) + (e - s); | |
91 | c = malloc(l+1); | |
92 | if (!c) | |
93 | return -ENOMEM; | |
94 | ||
95 | *((char*) mempcpy(stpcpy(c, field), s, e - s)) = 0; | |
96 | ||
97 | e += 1; | |
98 | ||
99 | } else if (unhexchar(**p) >= 0) { | |
100 | /* Hexadecimal escaping */ | |
101 | size_t allocated = 0; | |
102 | ||
103 | l = strlen(field); | |
104 | allocated = l + 2; | |
105 | c = malloc(allocated); | |
106 | if (!c) | |
107 | return -ENOMEM; | |
108 | ||
109 | memcpy(c, field, l); | |
110 | for (e = *p; *e != ' ' && *e != 0; e += 2) { | |
111 | int a, b; | |
112 | uint8_t x; | |
113 | ||
114 | a = unhexchar(e[0]); | |
115 | if (a < 0) | |
116 | return 0; | |
117 | ||
118 | b = unhexchar(e[1]); | |
119 | if (b < 0) | |
120 | return 0; | |
121 | ||
122 | x = ((uint8_t) a << 4 | (uint8_t) b); | |
123 | ||
124 | if (filter_printable && x < (uint8_t) ' ') | |
125 | x = (uint8_t) ' '; | |
126 | ||
127 | if (!GREEDY_REALLOC(c, allocated, l+2)) | |
128 | return -ENOMEM; | |
129 | ||
130 | c[l++] = (char) x; | |
131 | } | |
132 | ||
133 | c[l] = 0; | |
134 | } else | |
135 | return 0; | |
136 | ||
137 | if (!GREEDY_REALLOC(*iov, *n_iov_allocated, *n_iov + 1)) | |
138 | return -ENOMEM; | |
139 | ||
140 | (*iov)[*n_iov].iov_base = c; | |
141 | (*iov)[*n_iov].iov_len = l; | |
142 | (*n_iov) ++; | |
143 | ||
144 | *p = e; | |
145 | c = NULL; | |
146 | ||
147 | return 1; | |
148 | } | |
149 | ||
150 | static int map_string_field(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) { | |
151 | return map_string_field_internal(field, p, iov, n_iov_allocated, n_iov, false); | |
152 | } | |
153 | ||
154 | static int map_string_field_printable(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) { | |
155 | return map_string_field_internal(field, p, iov, n_iov_allocated, n_iov, true); | |
156 | } | |
157 | ||
158 | static int map_generic_field(const char *prefix, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) { | |
159 | const char *e, *f; | |
160 | char *c, *t; | |
161 | int r; | |
162 | ||
163 | /* Implements fallback mappings for all fields we don't know */ | |
164 | ||
165 | for (e = *p; e < *p + 16; e++) { | |
166 | ||
167 | if (*e == 0 || *e == ' ') | |
168 | return 0; | |
169 | ||
170 | if (*e == '=') | |
171 | break; | |
172 | ||
173 | if (!((*e >= 'a' && *e <= 'z') || | |
174 | (*e >= 'A' && *e <= 'Z') || | |
175 | (*e >= '0' && *e <= '9') || | |
176 | *e == '_' || *e == '-')) | |
177 | return 0; | |
178 | } | |
179 | ||
180 | if (e <= *p || e >= *p + 16) | |
181 | return 0; | |
182 | ||
183 | c = alloca(strlen(prefix) + (e - *p) + 2); | |
184 | ||
185 | t = stpcpy(c, prefix); | |
186 | for (f = *p; f < e; f++) { | |
187 | char x; | |
188 | ||
189 | if (*f >= 'a' && *f <= 'z') | |
190 | x = (*f - 'a') + 'A'; /* uppercase */ | |
191 | else if (*f == '-') | |
192 | x = '_'; /* dashes → underscores */ | |
193 | else | |
194 | x = *f; | |
195 | ||
196 | *(t++) = x; | |
197 | } | |
198 | strcpy(t, "="); | |
199 | ||
200 | e ++; | |
201 | ||
202 | r = map_simple_field(c, &e, iov, n_iov_allocated, n_iov); | |
203 | if (r < 0) | |
204 | return r; | |
205 | ||
206 | *p = e; | |
207 | return r; | |
208 | } | |
209 | ||
e735f4d4 | 210 | /* Kernel fields are those occurring in the audit string before |
f47781d8 MP |
211 | * msg='. All of these fields are trusted, hence carry the "_" prefix. |
212 | * We try to translate the fields we know into our native names. The | |
213 | * other's are generically mapped to _AUDIT_FIELD_XYZ= */ | |
214 | static const MapField map_fields_kernel[] = { | |
215 | ||
216 | /* First, we map certain well-known audit fields into native | |
217 | * well-known fields */ | |
218 | { "pid=", "_PID=", map_simple_field }, | |
219 | { "ppid=", "_PPID=", map_simple_field }, | |
220 | { "uid=", "_UID=", map_simple_field }, | |
221 | { "euid=", "_EUID=", map_simple_field }, | |
222 | { "fsuid=", "_FSUID=", map_simple_field }, | |
223 | { "gid=", "_GID=", map_simple_field }, | |
224 | { "egid=", "_EGID=", map_simple_field }, | |
225 | { "fsgid=", "_FSGID=", map_simple_field }, | |
226 | { "tty=", "_TTY=", map_simple_field }, | |
227 | { "ses=", "_AUDIT_SESSION=", map_simple_field }, | |
228 | { "auid=", "_AUDIT_LOGINUID=", map_simple_field }, | |
229 | { "subj=", "_SELINUX_CONTEXT=", map_simple_field }, | |
230 | { "comm=", "_COMM=", map_string_field }, | |
231 | { "exe=", "_EXE=", map_string_field }, | |
232 | { "proctitle=", "_CMDLINE=", map_string_field_printable }, | |
233 | ||
234 | /* Some fields don't map to native well-known fields. However, | |
235 | * we know that they are string fields, hence let's undo | |
236 | * string field escaping for them, though we stick to the | |
237 | * generic field names. */ | |
238 | { "path=", "_AUDIT_FIELD_PATH=", map_string_field }, | |
239 | { "dev=", "_AUDIT_FIELD_DEV=", map_string_field }, | |
240 | { "name=", "_AUDIT_FIELD_NAME=", map_string_field }, | |
241 | {} | |
242 | }; | |
243 | ||
e735f4d4 | 244 | /* Userspace fields are those occurring in the audit string after |
f47781d8 MP |
245 | * msg='. All of these fields are untrusted, hence carry no "_" |
246 | * prefix. We map the fields we don't know to AUDIT_FIELD_XYZ= */ | |
247 | static const MapField map_fields_userspace[] = { | |
248 | { "cwd=", "AUDIT_FIELD_CWD=", map_string_field }, | |
249 | { "cmd=", "AUDIT_FIELD_CMD=", map_string_field }, | |
250 | { "acct=", "AUDIT_FIELD_ACCT=", map_string_field }, | |
251 | { "exe=", "AUDIT_FIELD_EXE=", map_string_field }, | |
252 | { "comm=", "AUDIT_FIELD_COMM=", map_string_field }, | |
253 | {} | |
254 | }; | |
255 | ||
256 | static int map_all_fields( | |
257 | const char *p, | |
258 | const MapField map_fields[], | |
259 | const char *prefix, | |
260 | bool handle_msg, | |
261 | struct iovec **iov, | |
262 | size_t *n_iov_allocated, | |
263 | unsigned *n_iov) { | |
264 | ||
265 | int r; | |
266 | ||
267 | assert(p); | |
268 | assert(iov); | |
269 | assert(n_iov_allocated); | |
270 | assert(n_iov); | |
271 | ||
272 | for (;;) { | |
273 | bool mapped = false; | |
274 | const MapField *m; | |
275 | const char *v; | |
276 | ||
277 | p += strspn(p, WHITESPACE); | |
278 | ||
279 | if (*p == 0) | |
280 | return 0; | |
281 | ||
282 | if (handle_msg) { | |
283 | v = startswith(p, "msg='"); | |
284 | if (v) { | |
285 | const char *e; | |
286 | char *c; | |
287 | ||
288 | /* Userspace message. It's enclosed in | |
289 | simple quotation marks, is not | |
290 | escaped, but the last field in the | |
291 | line, hence let's remove the | |
292 | quotation mark, and apply the | |
293 | userspace mapping instead of the | |
294 | kernel mapping. */ | |
295 | ||
296 | e = endswith(v, "'"); | |
297 | if (!e) | |
298 | return 0; /* don't continue splitting up if the final quotation mark is missing */ | |
299 | ||
300 | c = strndupa(v, e - v); | |
301 | return map_all_fields(c, map_fields_userspace, "AUDIT_FIELD_", false, iov, n_iov_allocated, n_iov); | |
302 | } | |
303 | } | |
304 | ||
305 | /* Try to map the kernel fields to our own names */ | |
306 | for (m = map_fields; m->audit_field; m++) { | |
307 | v = startswith(p, m->audit_field); | |
308 | if (!v) | |
309 | continue; | |
310 | ||
311 | r = m->map(m->journal_field, &v, iov, n_iov_allocated, n_iov); | |
312 | if (r < 0) | |
313 | return log_debug_errno(r, "Failed to parse audit array: %m"); | |
314 | ||
315 | if (r > 0) { | |
316 | mapped = true; | |
317 | p = v; | |
318 | break; | |
319 | } | |
320 | } | |
321 | ||
322 | if (!mapped) { | |
323 | r = map_generic_field(prefix, &p, iov, n_iov_allocated, n_iov); | |
324 | if (r < 0) | |
325 | return log_debug_errno(r, "Failed to parse audit array: %m"); | |
326 | ||
6300502b | 327 | if (r == 0) |
f47781d8 MP |
328 | /* Couldn't process as generic field, let's just skip over it */ |
329 | p += strcspn(p, WHITESPACE); | |
f47781d8 MP |
330 | } |
331 | } | |
332 | } | |
333 | ||
334 | static void process_audit_string(Server *s, int type, const char *data, size_t size) { | |
335 | _cleanup_free_ struct iovec *iov = NULL; | |
336 | size_t n_iov_allocated = 0; | |
337 | unsigned n_iov = 0, k; | |
338 | uint64_t seconds, msec, id; | |
e3bff60a | 339 | const char *p, *type_name; |
f47781d8 MP |
340 | unsigned z; |
341 | char id_field[sizeof("_AUDIT_ID=") + DECIMAL_STR_MAX(uint64_t)], | |
342 | type_field[sizeof("_AUDIT_TYPE=") + DECIMAL_STR_MAX(int)], | |
343 | source_time_field[sizeof("_SOURCE_REALTIME_TIMESTAMP=") + DECIMAL_STR_MAX(usec_t)]; | |
344 | char *m; | |
345 | ||
346 | assert(s); | |
347 | ||
348 | if (size <= 0) | |
349 | return; | |
350 | ||
351 | if (!data) | |
352 | return; | |
353 | ||
354 | /* Note that the input buffer is NUL terminated, but let's | |
355 | * check whether there is a spurious NUL byte */ | |
356 | if (memchr(data, 0, size)) | |
357 | return; | |
358 | ||
359 | p = startswith(data, "audit"); | |
360 | if (!p) | |
361 | return; | |
362 | ||
e735f4d4 | 363 | if (sscanf(p, "(%" PRIu64 ".%" PRIu64 ":%" PRIu64 "):%n", |
f47781d8 MP |
364 | &seconds, |
365 | &msec, | |
366 | &id, | |
367 | &k) != 3) | |
368 | return; | |
369 | ||
370 | p += k; | |
371 | p += strspn(p, WHITESPACE); | |
372 | ||
373 | if (isempty(p)) | |
374 | return; | |
375 | ||
e3bff60a | 376 | n_iov_allocated = N_IOVEC_META_FIELDS + 7; |
f47781d8 MP |
377 | iov = new(struct iovec, n_iov_allocated); |
378 | if (!iov) { | |
379 | log_oom(); | |
380 | return; | |
381 | } | |
382 | ||
383 | IOVEC_SET_STRING(iov[n_iov++], "_TRANSPORT=audit"); | |
384 | ||
385 | sprintf(source_time_field, "_SOURCE_REALTIME_TIMESTAMP=%" PRIu64, | |
386 | (usec_t) seconds * USEC_PER_SEC + (usec_t) msec * USEC_PER_MSEC); | |
387 | IOVEC_SET_STRING(iov[n_iov++], source_time_field); | |
388 | ||
389 | sprintf(type_field, "_AUDIT_TYPE=%i", type); | |
390 | IOVEC_SET_STRING(iov[n_iov++], type_field); | |
391 | ||
392 | sprintf(id_field, "_AUDIT_ID=%" PRIu64, id); | |
393 | IOVEC_SET_STRING(iov[n_iov++], id_field); | |
394 | ||
e3bff60a MP |
395 | assert_cc(32 == LOG_AUTH); |
396 | IOVEC_SET_STRING(iov[n_iov++], "SYSLOG_FACILITY=32"); | |
397 | IOVEC_SET_STRING(iov[n_iov++], "SYSLOG_IDENTIFIER=audit"); | |
398 | ||
399 | type_name = audit_type_name_alloca(type); | |
400 | ||
401 | m = strjoina("MESSAGE=", type_name, " ", p); | |
f47781d8 MP |
402 | IOVEC_SET_STRING(iov[n_iov++], m); |
403 | ||
404 | z = n_iov; | |
405 | ||
406 | map_all_fields(p, map_fields_kernel, "_AUDIT_FIELD_", true, &iov, &n_iov_allocated, &n_iov); | |
407 | ||
408 | if (!GREEDY_REALLOC(iov, n_iov_allocated, n_iov + N_IOVEC_META_FIELDS)) { | |
409 | log_oom(); | |
410 | goto finish; | |
411 | } | |
412 | ||
413 | server_dispatch_message(s, iov, n_iov, n_iov_allocated, NULL, NULL, NULL, 0, NULL, LOG_NOTICE, 0); | |
414 | ||
415 | finish: | |
416 | /* free() all entries that map_all_fields() added. All others | |
417 | * are allocated on the stack or are constant. */ | |
418 | ||
419 | for (; z < n_iov; z++) | |
420 | free(iov[z].iov_base); | |
421 | } | |
422 | ||
423 | void server_process_audit_message( | |
424 | Server *s, | |
425 | const void *buffer, | |
426 | size_t buffer_size, | |
427 | const struct ucred *ucred, | |
428 | const union sockaddr_union *sa, | |
429 | socklen_t salen) { | |
430 | ||
431 | const struct nlmsghdr *nl = buffer; | |
432 | ||
433 | assert(s); | |
434 | ||
435 | if (buffer_size < ALIGN(sizeof(struct nlmsghdr))) | |
436 | return; | |
437 | ||
438 | assert(buffer); | |
439 | ||
440 | /* Filter out fake data */ | |
441 | if (!sa || | |
442 | salen != sizeof(struct sockaddr_nl) || | |
443 | sa->nl.nl_family != AF_NETLINK || | |
444 | sa->nl.nl_pid != 0) { | |
445 | log_debug("Audit netlink message from invalid sender."); | |
446 | return; | |
447 | } | |
448 | ||
449 | if (!ucred || ucred->pid != 0) { | |
450 | log_debug("Audit netlink message with invalid credentials."); | |
451 | return; | |
452 | } | |
453 | ||
454 | if (!NLMSG_OK(nl, buffer_size)) { | |
455 | log_error("Audit netlink message truncated."); | |
456 | return; | |
457 | } | |
458 | ||
459 | /* Ignore special Netlink messages */ | |
460 | if (IN_SET(nl->nlmsg_type, NLMSG_NOOP, NLMSG_ERROR)) | |
461 | return; | |
462 | ||
463 | /* Below AUDIT_FIRST_USER_MSG theer are only control messages, let's ignore those */ | |
464 | if (nl->nlmsg_type < AUDIT_FIRST_USER_MSG) | |
465 | return; | |
466 | ||
467 | process_audit_string(s, nl->nlmsg_type, NLMSG_DATA(nl), nl->nlmsg_len - ALIGN(sizeof(struct nlmsghdr))); | |
468 | } | |
469 | ||
470 | static int enable_audit(int fd, bool b) { | |
471 | struct { | |
472 | union { | |
473 | struct nlmsghdr header; | |
474 | uint8_t header_space[NLMSG_HDRLEN]; | |
475 | }; | |
476 | struct audit_status body; | |
477 | } _packed_ request = { | |
478 | .header.nlmsg_len = NLMSG_LENGTH(sizeof(struct audit_status)), | |
479 | .header.nlmsg_type = AUDIT_SET, | |
480 | .header.nlmsg_flags = NLM_F_REQUEST, | |
481 | .header.nlmsg_seq = 1, | |
482 | .header.nlmsg_pid = 0, | |
483 | .body.mask = AUDIT_STATUS_ENABLED, | |
484 | .body.enabled = b, | |
485 | }; | |
486 | union sockaddr_union sa = { | |
487 | .nl.nl_family = AF_NETLINK, | |
488 | .nl.nl_pid = 0, | |
489 | }; | |
490 | struct iovec iovec = { | |
491 | .iov_base = &request, | |
492 | .iov_len = NLMSG_LENGTH(sizeof(struct audit_status)), | |
493 | }; | |
494 | struct msghdr mh = { | |
495 | .msg_iov = &iovec, | |
496 | .msg_iovlen = 1, | |
497 | .msg_name = &sa.sa, | |
498 | .msg_namelen = sizeof(sa.nl), | |
499 | }; | |
500 | ||
501 | ssize_t n; | |
502 | ||
503 | n = sendmsg(fd, &mh, MSG_NOSIGNAL); | |
504 | if (n < 0) | |
505 | return -errno; | |
506 | if (n != NLMSG_LENGTH(sizeof(struct audit_status))) | |
507 | return -EIO; | |
508 | ||
509 | /* We don't wait for the result here, we can't do anything | |
510 | * about it anyway */ | |
511 | ||
512 | return 0; | |
513 | } | |
514 | ||
515 | int server_open_audit(Server *s) { | |
516 | static const int one = 1; | |
517 | int r; | |
518 | ||
519 | if (s->audit_fd < 0) { | |
520 | static const union sockaddr_union sa = { | |
521 | .nl.nl_family = AF_NETLINK, | |
522 | .nl.nl_pid = 0, | |
523 | .nl.nl_groups = AUDIT_NLGRP_READLOG, | |
524 | }; | |
525 | ||
526 | s->audit_fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_AUDIT); | |
527 | if (s->audit_fd < 0) { | |
528 | if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT) | |
529 | log_debug("Audit not supported in the kernel."); | |
530 | else | |
531 | log_warning_errno(errno, "Failed to create audit socket, ignoring: %m"); | |
532 | ||
533 | return 0; | |
534 | } | |
535 | ||
e3bff60a MP |
536 | if (bind(s->audit_fd, &sa.sa, sizeof(sa.nl)) < 0) { |
537 | log_warning_errno(errno, | |
538 | "Failed to join audit multicast group. " | |
539 | "The kernel is probably too old or multicast reading is not supported. " | |
540 | "Ignoring: %m"); | |
541 | s->audit_fd = safe_close(s->audit_fd); | |
542 | return 0; | |
543 | } | |
f47781d8 MP |
544 | } else |
545 | fd_nonblock(s->audit_fd, 1); | |
546 | ||
547 | r = setsockopt(s->audit_fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)); | |
548 | if (r < 0) | |
549 | return log_error_errno(errno, "Failed to set SO_PASSCRED on audit socket: %m"); | |
550 | ||
e735f4d4 | 551 | r = sd_event_add_io(s->event, &s->audit_event_source, s->audit_fd, EPOLLIN, server_process_datagram, s); |
f47781d8 MP |
552 | if (r < 0) |
553 | return log_error_errno(r, "Failed to add audit fd to event loop: %m"); | |
554 | ||
555 | /* We are listening now, try to enable audit */ | |
556 | r = enable_audit(s->audit_fd, true); | |
557 | if (r < 0) | |
558 | log_warning_errno(r, "Failed to issue audit enable call: %m"); | |
559 | ||
560 | return 0; | |
561 | } |