src/journal/journald-audit.c

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