src/journal/journald-audit.c

   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"
  24 #include "audit-type.h"
  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
 210 /* Kernel fields are those occurring in the audit string before
 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
 244 /* Userspace fields are those occurring in the audit string after
 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
 327                         if (r == 0) {
 328                                 /* Couldn't process as generic field, let's just skip over it */
 329                                 p += strcspn(p, WHITESPACE);
 330                         }
 331                 }
 332         }
 333 }
 334
 335 static void process_audit_string(Server *s, int type, const char *data, size_t size) {
 336         _cleanup_free_ struct iovec *iov = NULL;
 337         size_t n_iov_allocated = 0;
 338         unsigned n_iov = 0, k;
 339         uint64_t seconds, msec, id;
 340         const char *p, *type_name;
 341         unsigned z;
 342         char id_field[sizeof("_AUDIT_ID=") + DECIMAL_STR_MAX(uint64_t)],
 343              type_field[sizeof("_AUDIT_TYPE=") + DECIMAL_STR_MAX(int)],
 344              source_time_field[sizeof("_SOURCE_REALTIME_TIMESTAMP=") + DECIMAL_STR_MAX(usec_t)];
 345         char *m;
 346
 347         assert(s);
 348
 349         if (size <= 0)
 350                 return;
 351
 352         if (!data)
 353                 return;
 354
 355         /* Note that the input buffer is NUL terminated, but let's
 356          * check whether there is a spurious NUL byte */
 357         if (memchr(data, 0, size))
 358                 return;
 359
 360         p = startswith(data, "audit");
 361         if (!p)
 362                 return;
 363
 364         if (sscanf(p, "(%" PRIu64 ".%" PRIu64 ":%" PRIu64 "):%n",
 365                    &seconds,
 366                    &msec,
 367                    &id,
 368                    &k) != 3)
 369                 return;
 370
 371         p += k;
 372         p += strspn(p, WHITESPACE);
 373
 374         if (isempty(p))
 375                 return;
 376
 377         n_iov_allocated = N_IOVEC_META_FIELDS + 7;
 378         iov = new(struct iovec, n_iov_allocated);
 379         if (!iov) {
 380                 log_oom();
 381                 return;
 382         }
 383
 384         IOVEC_SET_STRING(iov[n_iov++], "_TRANSPORT=audit");
 385
 386         sprintf(source_time_field, "_SOURCE_REALTIME_TIMESTAMP=%" PRIu64,
 387                 (usec_t) seconds * USEC_PER_SEC + (usec_t) msec * USEC_PER_MSEC);
 388         IOVEC_SET_STRING(iov[n_iov++], source_time_field);
 389
 390         sprintf(type_field, "_AUDIT_TYPE=%i", type);
 391         IOVEC_SET_STRING(iov[n_iov++], type_field);
 392
 393         sprintf(id_field, "_AUDIT_ID=%" PRIu64, id);
 394         IOVEC_SET_STRING(iov[n_iov++], id_field);
 395
 396         assert_cc(32 == LOG_AUTH);
 397         IOVEC_SET_STRING(iov[n_iov++], "SYSLOG_FACILITY=32");
 398         IOVEC_SET_STRING(iov[n_iov++], "SYSLOG_IDENTIFIER=audit");
 399
 400         type_name = audit_type_name_alloca(type);
 401
 402         m = strjoina("MESSAGE=", type_name, " ", p);
 403         IOVEC_SET_STRING(iov[n_iov++], m);
 404
 405         z = n_iov;
 406
 407         map_all_fields(p, map_fields_kernel, "_AUDIT_FIELD_", true, &iov, &n_iov_allocated, &n_iov);
 408
 409         if (!GREEDY_REALLOC(iov, n_iov_allocated, n_iov + N_IOVEC_META_FIELDS)) {
 410                 log_oom();
 411                 goto finish;
 412         }
 413
 414         server_dispatch_message(s, iov, n_iov, n_iov_allocated, NULL, NULL, NULL, 0, NULL, LOG_NOTICE, 0);
 415
 416 finish:
 417         /* free() all entries that map_all_fields() added. All others
 418          * are allocated on the stack or are constant. */
 419
 420         for (; z < n_iov; z++)
 421                 free(iov[z].iov_base);
 422 }
 423
 424 void server_process_audit_message(
 425                 Server *s,
 426                 const void *buffer,
 427                 size_t buffer_size,
 428                 const struct ucred *ucred,
 429                 const union sockaddr_union *sa,
 430                 socklen_t salen) {
 431
 432         const struct nlmsghdr *nl = buffer;
 433
 434         assert(s);
 435
 436         if (buffer_size < ALIGN(sizeof(struct nlmsghdr)))
 437                 return;
 438
 439         assert(buffer);
 440
 441         /* Filter out fake data */
 442         if (!sa ||
 443             salen != sizeof(struct sockaddr_nl) ||
 444             sa->nl.nl_family != AF_NETLINK ||
 445             sa->nl.nl_pid != 0) {
 446                 log_debug("Audit netlink message from invalid sender.");
 447                 return;
 448         }
 449
 450         if (!ucred || ucred->pid != 0) {
 451                 log_debug("Audit netlink message with invalid credentials.");
 452                 return;
 453         }
 454
 455         if (!NLMSG_OK(nl, buffer_size)) {
 456                 log_error("Audit netlink message truncated.");
 457                 return;
 458         }
 459
 460         /* Ignore special Netlink messages */
 461         if (IN_SET(nl->nlmsg_type, NLMSG_NOOP, NLMSG_ERROR))
 462                 return;
 463
 464         /* Below AUDIT_FIRST_USER_MSG theer are only control messages, let's ignore those */
 465         if (nl->nlmsg_type < AUDIT_FIRST_USER_MSG)
 466                 return;
 467
 468         process_audit_string(s, nl->nlmsg_type, NLMSG_DATA(nl), nl->nlmsg_len - ALIGN(sizeof(struct nlmsghdr)));
 469 }
 470
 471 static int enable_audit(int fd, bool b) {
 472         struct {
 473                 union {
 474                         struct nlmsghdr header;
 475                         uint8_t header_space[NLMSG_HDRLEN];
 476                 };
 477                 struct audit_status body;
 478         } _packed_ request = {
 479                 .header.nlmsg_len = NLMSG_LENGTH(sizeof(struct audit_status)),
 480                 .header.nlmsg_type = AUDIT_SET,
 481                 .header.nlmsg_flags = NLM_F_REQUEST,
 482                 .header.nlmsg_seq = 1,
 483                 .header.nlmsg_pid = 0,
 484                 .body.mask = AUDIT_STATUS_ENABLED,
 485                 .body.enabled = b,
 486         };
 487         union sockaddr_union sa = {
 488                 .nl.nl_family = AF_NETLINK,
 489                 .nl.nl_pid = 0,
 490         };
 491         struct iovec iovec = {
 492                 .iov_base = &request,
 493                 .iov_len = NLMSG_LENGTH(sizeof(struct audit_status)),
 494         };
 495         struct msghdr mh = {
 496                 .msg_iov = &iovec,
 497                 .msg_iovlen = 1,
 498                 .msg_name = &sa.sa,
 499                 .msg_namelen = sizeof(sa.nl),
 500         };
 501
 502         ssize_t n;
 503
 504         n = sendmsg(fd, &mh, MSG_NOSIGNAL);
 505         if (n < 0)
 506                 return -errno;
 507         if (n != NLMSG_LENGTH(sizeof(struct audit_status)))
 508                 return -EIO;
 509
 510         /* We don't wait for the result here, we can't do anything
 511          * about it anyway */
 512
 513         return 0;
 514 }
 515
 516 int server_open_audit(Server *s) {
 517         static const int one = 1;
 518         int r;
 519
 520         if (s->audit_fd < 0) {
 521                 static const union sockaddr_union sa = {
 522                         .nl.nl_family = AF_NETLINK,
 523                         .nl.nl_pid    = 0,
 524                         .nl.nl_groups = AUDIT_NLGRP_READLOG,
 525                 };
 526
 527                 s->audit_fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_AUDIT);
 528                 if (s->audit_fd < 0) {
 529                         if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
 530                                 log_debug("Audit not supported in the kernel.");
 531                         else
 532                                 log_warning_errno(errno, "Failed to create audit socket, ignoring: %m");
 533
 534                         return 0;
 535                 }
 536
 537                 if (bind(s->audit_fd, &sa.sa, sizeof(sa.nl)) < 0) {
 538                         log_warning_errno(errno,
 539                                           "Failed to join audit multicast group. "
 540                                           "The kernel is probably too old or multicast reading is not supported. "
 541                                           "Ignoring: %m");
 542                         s->audit_fd = safe_close(s->audit_fd);
 543                         return 0;
 544                 }
 545         } else
 546                 fd_nonblock(s->audit_fd, 1);
 547
 548         r = setsockopt(s->audit_fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one));
 549         if (r < 0)
 550                 return log_error_errno(errno, "Failed to set SO_PASSCRED on audit socket: %m");
 551
 552         r = sd_event_add_io(s->event, &s->audit_event_source, s->audit_fd, EPOLLIN, server_process_datagram, s);
 553         if (r < 0)
 554                 return log_error_errno(r, "Failed to add audit fd to event loop: %m");
 555
 556         /* We are listening now, try to enable audit */
 557         r = enable_audit(s->audit_fd, true);
 558         if (r < 0)
 559                 log_warning_errno(r, "Failed to issue audit enable call: %m");
 560
 561         return 0;
 562 }