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
  25 typedef struct MapField {
  26         const char *audit_field;
  27         const char *journal_field;
  28         int (*map)(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov);
  29 } MapField;
  30
  31 static int map_simple_field(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) {
  32         _cleanup_free_ char *c = NULL;
  33         size_t l = 0, allocated = 0;
  34         const char *e;
  35
  36         assert(field);
  37         assert(p);
  38         assert(iov);
  39         assert(n_iov);
  40
  41         l = strlen(field);
  42         allocated = l + 1;
  43         c = malloc(allocated);
  44         if (!c)
  45                 return -ENOMEM;
  46
  47         memcpy(c, field, l);
  48         for (e = *p; *e != ' ' && *e != 0; e++) {
  49                 if (!GREEDY_REALLOC(c, allocated, l+2))
  50                         return -ENOMEM;
  51
  52                 c[l++] = *e;
  53         }
  54
  55         c[l] = 0;
  56
  57         if (!GREEDY_REALLOC(*iov, *n_iov_allocated, *n_iov + 1))
  58                 return -ENOMEM;
  59
  60         (*iov)[*n_iov].iov_base = c;
  61         (*iov)[*n_iov].iov_len = l;
  62         (*n_iov) ++;
  63
  64         *p = e;
  65         c = NULL;
  66
  67         return 1;
  68 }
  69
  70 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) {
  71         _cleanup_free_ char *c = NULL;
  72         const char *s, *e;
  73         size_t l;
  74
  75         assert(field);
  76         assert(p);
  77         assert(iov);
  78         assert(n_iov);
  79
  80         /* The kernel formats string fields in one of two formats. */
  81
  82         if (**p == '"') {
  83                 /* Normal quoted syntax */
  84                 s = *p + 1;
  85                 e = strchr(s, '"');
  86                 if (!e)
  87                         return 0;
  88
  89                 l = strlen(field) + (e - s);
  90                 c = malloc(l+1);
  91                 if (!c)
  92                         return -ENOMEM;
  93
  94                 *((char*) mempcpy(stpcpy(c, field), s, e - s)) = 0;
  95
  96                 e += 1;
  97
  98         } else if (unhexchar(**p) >= 0) {
  99                 /* Hexadecimal escaping */
 100                 size_t allocated = 0;
 101
 102                 l = strlen(field);
 103                 allocated = l + 2;
 104                 c = malloc(allocated);
 105                 if (!c)
 106                         return -ENOMEM;
 107
 108                 memcpy(c, field, l);
 109                 for (e = *p; *e != ' ' && *e != 0; e += 2) {
 110                         int a, b;
 111                         uint8_t x;
 112
 113                         a = unhexchar(e[0]);
 114                         if (a < 0)
 115                                 return 0;
 116
 117                         b = unhexchar(e[1]);
 118                         if (b < 0)
 119                                 return 0;
 120
 121                         x = ((uint8_t) a << 4 | (uint8_t) b);
 122
 123                         if (filter_printable && x < (uint8_t) ' ')
 124                                 x = (uint8_t) ' ';
 125
 126                         if (!GREEDY_REALLOC(c, allocated, l+2))
 127                                 return -ENOMEM;
 128
 129                         c[l++] = (char) x;
 130                 }
 131
 132                 c[l] = 0;
 133         } else
 134                 return 0;
 135
 136         if (!GREEDY_REALLOC(*iov, *n_iov_allocated, *n_iov + 1))
 137                 return -ENOMEM;
 138
 139         (*iov)[*n_iov].iov_base = c;
 140         (*iov)[*n_iov].iov_len = l;
 141         (*n_iov) ++;
 142
 143         *p = e;
 144         c = NULL;
 145
 146         return 1;
 147 }
 148
 149 static int map_string_field(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) {
 150         return map_string_field_internal(field, p, iov, n_iov_allocated, n_iov, false);
 151 }
 152
 153 static int map_string_field_printable(const char *field, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) {
 154         return map_string_field_internal(field, p, iov, n_iov_allocated, n_iov, true);
 155 }
 156
 157 static int map_generic_field(const char *prefix, const char **p, struct iovec **iov, size_t *n_iov_allocated, unsigned *n_iov) {
 158         const char *e, *f;
 159         char *c, *t;
 160         int r;
 161
 162         /* Implements fallback mappings for all fields we don't know */
 163
 164         for (e = *p; e < *p + 16; e++) {
 165
 166                 if (*e == 0 || *e == ' ')
 167                         return 0;
 168
 169                 if (*e == '=')
 170                         break;
 171
 172                 if (!((*e >= 'a' && *e <= 'z') ||
 173                       (*e >= 'A' && *e <= 'Z') ||
 174                       (*e >= '0' && *e <= '9') ||
 175                       *e == '_' || *e == '-'))
 176                         return 0;
 177         }
 178
 179         if (e <= *p || e >= *p + 16)
 180                 return 0;
 181
 182         c = alloca(strlen(prefix) + (e - *p) + 2);
 183
 184         t = stpcpy(c, prefix);
 185         for (f = *p; f < e; f++) {
 186                 char x;
 187
 188                 if (*f >= 'a' && *f <= 'z')
 189                         x = (*f - 'a') + 'A'; /* uppercase */
 190                 else if (*f == '-')
 191                         x = '_'; /* dashes → underscores */
 192                 else
 193                         x = *f;
 194
 195                 *(t++) = x;
 196         }
 197         strcpy(t, "=");
 198
 199         e ++;
 200
 201         r = map_simple_field(c, &e, iov, n_iov_allocated, n_iov);
 202         if (r < 0)
 203                 return r;
 204
 205         *p = e;
 206         return r;
 207 }
 208
 209 /* Kernel fields are those occuring in the audit string before
 210  * msg='. All of these fields are trusted, hence carry the "_" prefix.
 211  * We try to translate the fields we know into our native names. The
 212  * other's are generically mapped to _AUDIT_FIELD_XYZ= */
 213 static const MapField map_fields_kernel[] = {
 214
 215         /* First, we map certain well-known audit fields into native
 216          * well-known fields */
 217         { "pid=",       "_PID=",                   map_simple_field },
 218         { "ppid=",      "_PPID=",                  map_simple_field },
 219         { "uid=",       "_UID=",                   map_simple_field },
 220         { "euid=",      "_EUID=",                  map_simple_field },
 221         { "fsuid=",     "_FSUID=",                 map_simple_field },
 222         { "gid=",       "_GID=",                   map_simple_field },
 223         { "egid=",      "_EGID=",                  map_simple_field },
 224         { "fsgid=",     "_FSGID=",                 map_simple_field },
 225         { "tty=",       "_TTY=",                   map_simple_field },
 226         { "ses=",       "_AUDIT_SESSION=",         map_simple_field },
 227         { "auid=",      "_AUDIT_LOGINUID=",        map_simple_field },
 228         { "subj=",      "_SELINUX_CONTEXT=",       map_simple_field },
 229         { "comm=",      "_COMM=",                  map_string_field },
 230         { "exe=",       "_EXE=",                   map_string_field },
 231         { "proctitle=", "_CMDLINE=",               map_string_field_printable },
 232
 233         /* Some fields don't map to native well-known fields. However,
 234          * we know that they are string fields, hence let's undo
 235          * string field escaping for them, though we stick to the
 236          * generic field names. */
 237         { "path=",      "_AUDIT_FIELD_PATH=",      map_string_field },
 238         { "dev=",       "_AUDIT_FIELD_DEV=",       map_string_field },
 239         { "name=",      "_AUDIT_FIELD_NAME=",      map_string_field },
 240         {}
 241 };
 242
 243 /* Userspace fields are thos occuring in the audit string after
 244  * msg='. All of these fields are untrusted, hence carry no "_"
 245  * prefix. We map the fields we don't know to AUDIT_FIELD_XYZ= */
 246 static const MapField map_fields_userspace[] = {
 247         { "cwd=",       "AUDIT_FIELD_CWD=",  map_string_field },
 248         { "cmd=",       "AUDIT_FIELD_CMD=",  map_string_field },
 249         { "acct=",      "AUDIT_FIELD_ACCT=", map_string_field },
 250         { "exe=",       "AUDIT_FIELD_EXE=",  map_string_field },
 251         { "comm=",      "AUDIT_FIELD_COMM=", map_string_field },
 252         {}
 253 };
 254
 255 static int map_all_fields(
 256                 const char *p,
 257                 const MapField map_fields[],
 258                 const char *prefix,
 259                 bool handle_msg,
 260                 struct iovec **iov,
 261                 size_t *n_iov_allocated,
 262                 unsigned *n_iov) {
 263
 264         int r;
 265
 266         assert(p);
 267         assert(iov);
 268         assert(n_iov_allocated);
 269         assert(n_iov);
 270
 271         for (;;) {
 272                 bool mapped = false;
 273                 const MapField *m;
 274                 const char *v;
 275
 276                 p += strspn(p, WHITESPACE);
 277
 278                 if (*p == 0)
 279                         return 0;
 280
 281                 if (handle_msg) {
 282                         v = startswith(p, "msg='");
 283                         if (v) {
 284                                 const char *e;
 285                                 char *c;
 286
 287                                 /* Userspace message. It's enclosed in
 288                                    simple quotation marks, is not
 289                                    escaped, but the last field in the
 290                                    line, hence let's remove the
 291                                    quotation mark, and apply the
 292                                    userspace mapping instead of the
 293                                    kernel mapping. */
 294
 295                                 e = endswith(v, "'");
 296                                 if (!e)
 297                                         return 0; /* don't continue splitting up if the final quotation mark is missing */
 298
 299                                 c = strndupa(v, e - v);
 300                                 return map_all_fields(c, map_fields_userspace, "AUDIT_FIELD_", false, iov, n_iov_allocated, n_iov);
 301                         }
 302                 }
 303
 304                 /* Try to map the kernel fields to our own names */
 305                 for (m = map_fields; m->audit_field; m++) {
 306                         v = startswith(p, m->audit_field);
 307                         if (!v)
 308                                 continue;
 309
 310                         r = m->map(m->journal_field, &v, iov, n_iov_allocated, n_iov);
 311                         if (r < 0) {
 312                                 log_debug_errno(r, "Failed to parse audit array: %m");
 313                                 return r;
 314                         }
 315
 316                         if (r > 0) {
 317                                 mapped = true;
 318                                 p = v;
 319                                 break;
 320                         }
 321                 }
 322
 323                 if (!mapped) {
 324                         r = map_generic_field(prefix, &p, iov, n_iov_allocated, n_iov);
 325                         if (r < 0) {
 326                                 log_debug_errno(r, "Failed to parse audit array: %m");
 327                                 return r;
 328                         }
 329
 330                         if (r == 0) {
 331                                 /* Couldn't process as generic field, let's just skip over it */
 332                                 p += strcspn(p, WHITESPACE);
 333                         }
 334                 }
 335         }
 336 }
 337
 338 static void process_audit_string(Server *s, int type, const char *data, size_t size) {
 339         _cleanup_free_ struct iovec *iov = NULL;
 340         size_t n_iov_allocated = 0;
 341         unsigned n_iov = 0, k;
 342         uint64_t seconds, msec, id;
 343         const char *p;
 344         unsigned z;
 345         char id_field[sizeof("_AUDIT_ID=") + DECIMAL_STR_MAX(uint64_t)],
 346              type_field[sizeof("_AUDIT_TYPE=") + DECIMAL_STR_MAX(int)],
 347              source_time_field[sizeof("_SOURCE_REALTIME_TIMESTAMP=") + DECIMAL_STR_MAX(usec_t)];
 348         char *m;
 349
 350         assert(s);
 351
 352         if (size <= 0)
 353                 return;
 354
 355         if (!data)
 356                 return;
 357
 358         /* Note that the input buffer is NUL terminated, but let's
 359          * check whether there is a spurious NUL byte */
 360         if (memchr(data, 0, size))
 361                 return;
 362
 363         p = startswith(data, "audit");
 364         if (!p)
 365                 return;
 366
 367         if (sscanf(p, "(%" PRIi64 ".%" PRIi64 ":%" PRIi64 "):%n",
 368                    &seconds,
 369                    &msec,
 370                    &id,
 371                    &k) != 3)
 372                 return;
 373
 374         p += k;
 375         p += strspn(p, WHITESPACE);
 376
 377         if (isempty(p))
 378                 return;
 379
 380         n_iov_allocated = N_IOVEC_META_FIELDS + 5;
 381         iov = new(struct iovec, n_iov_allocated);
 382         if (!iov) {
 383                 log_oom();
 384                 return;
 385         }
 386
 387         IOVEC_SET_STRING(iov[n_iov++], "_TRANSPORT=audit");
 388
 389         sprintf(source_time_field, "_SOURCE_REALTIME_TIMESTAMP=%" PRIu64,
 390                 (usec_t) seconds * USEC_PER_SEC + (usec_t) msec * USEC_PER_MSEC);
 391         IOVEC_SET_STRING(iov[n_iov++], source_time_field);
 392
 393         sprintf(type_field, "_AUDIT_TYPE=%i", type);
 394         IOVEC_SET_STRING(iov[n_iov++], type_field);
 395
 396         sprintf(id_field, "_AUDIT_ID=%" PRIu64, id);
 397         IOVEC_SET_STRING(iov[n_iov++], id_field);
 398
 399         m = alloca(strlen("MESSAGE=<audit-") + DECIMAL_STR_MAX(int) + strlen("> ") + strlen(p) + 1);
 400         sprintf(m, "MESSAGE=<audit-%i> %s", type, p);
 401         IOVEC_SET_STRING(iov[n_iov++], m);
 402
 403         z = n_iov;
 404
 405         map_all_fields(p, map_fields_kernel, "_AUDIT_FIELD_", true, &iov, &n_iov_allocated, &n_iov);
 406
 407         if (!GREEDY_REALLOC(iov, n_iov_allocated, n_iov + N_IOVEC_META_FIELDS)) {
 408                 log_oom();
 409                 goto finish;
 410         }
 411
 412         server_dispatch_message(s, iov, n_iov, n_iov_allocated, NULL, NULL, NULL, 0, NULL, LOG_NOTICE, 0);
 413
 414 finish:
 415         /* free() all entries that map_all_fields() added. All others
 416          * are allocated on the stack or are constant. */
 417
 418         for (; z < n_iov; z++)
 419                 free(iov[z].iov_base);
 420 }
 421
 422 void server_process_audit_message(
 423                 Server *s,
 424                 const void *buffer,
 425                 size_t buffer_size,
 426                 const struct ucred *ucred,
 427                 const union sockaddr_union *sa,
 428                 socklen_t salen) {
 429
 430         const struct nlmsghdr *nl = buffer;
 431
 432         assert(s);
 433
 434         if (buffer_size < ALIGN(sizeof(struct nlmsghdr)))
 435                 return;
 436
 437         assert(buffer);
 438
 439         /* Filter out fake data */
 440         if (!sa ||
 441             salen != sizeof(struct sockaddr_nl) ||
 442             sa->nl.nl_family != AF_NETLINK ||
 443             sa->nl.nl_pid != 0) {
 444                 log_debug("Audit netlink message from invalid sender.");
 445                 return;
 446         }
 447
 448         if (!ucred || ucred->pid != 0) {
 449                 log_debug("Audit netlink message with invalid credentials.");
 450                 return;
 451         }
 452
 453         if (!NLMSG_OK(nl, buffer_size)) {
 454                 log_error("Audit netlink message truncated.");
 455                 return;
 456         }
 457
 458         /* Ignore special Netlink messages */
 459         if (IN_SET(nl->nlmsg_type, NLMSG_NOOP, NLMSG_ERROR))
 460                 return;
 461
 462         /* Below AUDIT_FIRST_USER_MSG theer are only control messages, let's ignore those */
 463         if (nl->nlmsg_type < AUDIT_FIRST_USER_MSG)
 464                 return;
 465
 466         process_audit_string(s, nl->nlmsg_type, NLMSG_DATA(nl), nl->nlmsg_len - ALIGN(sizeof(struct nlmsghdr)));
 467 }
 468
 469 static int enable_audit(int fd, bool b) {
 470         struct {
 471                 union {
 472                         struct nlmsghdr header;
 473                         uint8_t header_space[NLMSG_HDRLEN];
 474                 };
 475                 struct audit_status body;
 476         } _packed_ request = {
 477                 .header.nlmsg_len = NLMSG_LENGTH(sizeof(struct audit_status)),
 478                 .header.nlmsg_type = AUDIT_SET,
 479                 .header.nlmsg_flags = NLM_F_REQUEST,
 480                 .header.nlmsg_seq = 1,
 481                 .header.nlmsg_pid = 0,
 482                 .body.mask = AUDIT_STATUS_ENABLED,
 483                 .body.enabled = b,
 484         };
 485         union sockaddr_union sa = {
 486                 .nl.nl_family = AF_NETLINK,
 487                 .nl.nl_pid = 0,
 488         };
 489         struct iovec iovec = {
 490                 .iov_base = &request,
 491                 .iov_len = NLMSG_LENGTH(sizeof(struct audit_status)),
 492         };
 493         struct msghdr mh = {
 494                 .msg_iov = &iovec,
 495                 .msg_iovlen = 1,
 496                 .msg_name = &sa.sa,
 497                 .msg_namelen = sizeof(sa.nl),
 498         };
 499
 500         ssize_t n;
 501
 502         n = sendmsg(fd, &mh, MSG_NOSIGNAL);
 503         if (n < 0)
 504                 return -errno;
 505         if (n != NLMSG_LENGTH(sizeof(struct audit_status)))
 506                 return -EIO;
 507
 508         /* We don't wait for the result here, we can't do anything
 509          * about it anyway */
 510
 511         return 0;
 512 }
 513
 514 int server_open_audit(Server *s) {
 515         static const int one = 1;
 516         int r;
 517
 518         if (s->audit_fd < 0) {
 519                 static const union sockaddr_union sa = {
 520                         .nl.nl_family = AF_NETLINK,
 521                         .nl.nl_pid    = 0,
 522                         .nl.nl_groups = AUDIT_NLGRP_READLOG,
 523                 };
 524
 525                 s->audit_fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_AUDIT);
 526                 if (s->audit_fd < 0) {
 527                         if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
 528                                 log_debug("Audit not supported in the kernel.");
 529                         else
 530                                 log_warning("Failed to create audit socket, ignoring: %m");
 531
 532                         return 0;
 533                 }
 534
 535                 r = bind(s->audit_fd, &sa.sa, sizeof(sa.nl));
 536                 if (r < 0) {
 537                         log_error("Failed to join audit multicast group: %m");
 538                         return -errno;
 539                 }
 540         } else
 541                 fd_nonblock(s->audit_fd, 1);
 542
 543         r = setsockopt(s->audit_fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one));
 544         if (r < 0) {
 545                 log_error("Failed to set SO_PASSCRED on audit socket: %m");
 546                 return -errno;
 547         }
 548
 549         r = sd_event_add_io(s->event, &s->audit_event_source, s->audit_fd, EPOLLIN, process_datagram, s);
 550         if (r < 0) {
 551                 log_error_errno(r, "Failed to add audit fd to event loop: %m");
 552                 return r;
 553         }
 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 }