src/shared/utmp-wtmp.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <poll.h>
   6 #include <stddef.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <sys/time.h>
  10 #include <sys/utsname.h>
  11 #include <unistd.h>
  12 #include <utmpx.h>
  13
  14 #include "alloc-util.h"
  15 #include "fd-util.h"
  16 #include "hostname-util.h"
  17 #include "io-util.h"
  18 #include "macro.h"
  19 #include "memory-util.h"
  20 #include "path-util.h"
  21 #include "string-util.h"
  22 #include "terminal-util.h"
  23 #include "time-util.h"
  24 #include "user-util.h"
  25 #include "utmp-wtmp.h"
  26
  27 int utmp_get_runlevel(int *runlevel, int *previous) {
  28         _cleanup_(utxent_cleanup) bool utmpx = false;
  29         struct utmpx *found, lookup = { .ut_type = RUN_LVL };
  30         const char *e;
  31
  32         assert(runlevel);
  33
  34         /* If these values are set in the environment this takes
  35          * precedence. Presumably, sysvinit does this to work around a
  36          * race condition that would otherwise exist where we'd always
  37          * go to disk and hence might read runlevel data that might be
  38          * very new and not apply to the current script being executed. */
  39
  40         e = getenv("RUNLEVEL");
  41         if (e && e[0] > 0) {
  42                 *runlevel = e[0];
  43
  44                 if (previous) {
  45                         /* $PREVLEVEL seems to be an Upstart thing */
  46
  47                         e = getenv("PREVLEVEL");
  48                         if (e && e[0] > 0)
  49                                 *previous = e[0];
  50                         else
  51                                 *previous = 0;
  52                 }
  53
  54                 return 0;
  55         }
  56
  57         if (utmpxname(_PATH_UTMPX) < 0)
  58                 return -errno;
  59
  60         utmpx = utxent_start();
  61
  62         found = getutxid(&lookup);
  63         if (!found)
  64                 return -errno;
  65
  66         *runlevel = found->ut_pid & 0xFF;
  67         if (previous)
  68                 *previous = (found->ut_pid >> 8) & 0xFF;
  69
  70         return 0;
  71 }
  72
  73 static void init_timestamp(struct utmpx *store, usec_t t) {
  74         assert(store);
  75
  76         if (t <= 0)
  77                 t = now(CLOCK_REALTIME);
  78
  79         store->ut_tv.tv_sec = t / USEC_PER_SEC;
  80         store->ut_tv.tv_usec = t % USEC_PER_SEC;
  81 }
  82
  83 static void init_entry(struct utmpx *store, usec_t t) {
  84         struct utsname uts = {};
  85
  86         assert(store);
  87
  88         init_timestamp(store, t);
  89
  90         if (uname(&uts) >= 0)
  91                 strncpy(store->ut_host, uts.release, sizeof(store->ut_host));
  92
  93         strncpy(store->ut_line, "~", sizeof(store->ut_line));  /* or ~~ ? */
  94         strncpy(store->ut_id, "~~", sizeof(store->ut_id));
  95 }
  96
  97 static int write_entry_utmp(const struct utmpx *store) {
  98         _cleanup_(utxent_cleanup) bool utmpx = false;
  99
 100         assert(store);
 101
 102         /* utmp is similar to wtmp, but there is only one entry for
 103          * each entry type resp. user; i.e. basically a key/value
 104          * table. */
 105
 106         if (utmpxname(_PATH_UTMPX) < 0)
 107                 return -errno;
 108
 109         utmpx = utxent_start();
 110
 111         if (pututxline(store))
 112                 return 0;
 113         if (errno == ENOENT) {
 114                 /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */
 115                 log_debug_errno(errno, "Not writing utmp: %m");
 116                 return 0;
 117         }
 118         return -errno;
 119 }
 120
 121 static int write_entry_wtmp(const struct utmpx *store) {
 122         assert(store);
 123
 124         /* wtmp is a simple append-only file where each entry is
 125          * simply appended to the end; i.e. basically a log. */
 126
 127         errno = 0;
 128         updwtmpx(_PATH_WTMPX, store);
 129         if (errno == ENOENT) {
 130                 /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */
 131                 log_debug_errno(errno, "Not writing wtmp: %m");
 132                 return 0;
 133         }
 134         if (errno == EROFS) {
 135                 log_warning_errno(errno, "Failed to write wtmp record, ignoring: %m");
 136                 return 0;
 137         }
 138         return -errno;
 139 }
 140
 141 static int write_utmp_wtmp(const struct utmpx *store_utmp, const struct utmpx *store_wtmp) {
 142         int r, s;
 143
 144         r = write_entry_utmp(store_utmp);
 145         s = write_entry_wtmp(store_wtmp);
 146         return r < 0 ? r : s;
 147 }
 148
 149 static int write_entry_both(const struct utmpx *store) {
 150         return write_utmp_wtmp(store, store);
 151 }
 152
 153 int utmp_put_shutdown(void) {
 154         struct utmpx store = {};
 155
 156         init_entry(&store, 0);
 157
 158         store.ut_type = RUN_LVL;
 159         strncpy(store.ut_user, "shutdown", sizeof(store.ut_user));
 160
 161         return write_entry_both(&store);
 162 }
 163
 164 int utmp_put_reboot(usec_t t) {
 165         struct utmpx store = {};
 166
 167         init_entry(&store, t);
 168
 169         store.ut_type = BOOT_TIME;
 170         strncpy(store.ut_user, "reboot", sizeof(store.ut_user));
 171
 172         return write_entry_both(&store);
 173 }
 174
 175 static void copy_suffix(char *buf, size_t buf_size, const char *src) {
 176         size_t l;
 177
 178         l = strlen(src);
 179         if (l < buf_size)
 180                 strncpy(buf, src, buf_size);
 181         else
 182                 memcpy(buf, src + l - buf_size, buf_size);
 183 }
 184
 185 int utmp_put_init_process(const char *id, pid_t pid, pid_t sid, const char *line, int ut_type, const char *user) {
 186         struct utmpx store = {
 187                 .ut_type = INIT_PROCESS,
 188                 .ut_pid = pid,
 189                 .ut_session = sid,
 190         };
 191         int r;
 192
 193         assert(id);
 194
 195         init_timestamp(&store, 0);
 196
 197         /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */
 198         copy_suffix(store.ut_id, sizeof(store.ut_id), id);
 199
 200         if (line)
 201                 strncpy_exact(store.ut_line, line, sizeof(store.ut_line));
 202
 203         r = write_entry_both(&store);
 204         if (r < 0)
 205                 return r;
 206
 207         if (IN_SET(ut_type, LOGIN_PROCESS, USER_PROCESS)) {
 208                 store.ut_type = LOGIN_PROCESS;
 209                 r = write_entry_both(&store);
 210                 if (r < 0)
 211                         return r;
 212         }
 213
 214         if (ut_type == USER_PROCESS) {
 215                 store.ut_type = USER_PROCESS;
 216                 strncpy(store.ut_user, user, sizeof(store.ut_user)-1);
 217                 r = write_entry_both(&store);
 218                 if (r < 0)
 219                         return r;
 220         }
 221
 222         return 0;
 223 }
 224
 225 int utmp_put_dead_process(const char *id, pid_t pid, int code, int status) {
 226         struct utmpx lookup = {
 227                 .ut_type = INIT_PROCESS /* looks for DEAD_PROCESS, LOGIN_PROCESS, USER_PROCESS, too */
 228         }, store, store_wtmp, *found;
 229
 230         assert(id);
 231
 232         setutxent();
 233
 234         /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */
 235         copy_suffix(store.ut_id, sizeof(store.ut_id), id);
 236
 237         found = getutxid(&lookup);
 238         if (!found)
 239                 return 0;
 240
 241         if (found->ut_pid != pid)
 242                 return 0;
 243
 244         memcpy(&store, found, sizeof(store));
 245         store.ut_type = DEAD_PROCESS;
 246         store.ut_exit.e_termination = code;
 247         store.ut_exit.e_exit = status;
 248
 249         zero(store.ut_user);
 250         zero(store.ut_host);
 251         zero(store.ut_tv);
 252
 253         memcpy(&store_wtmp, &store, sizeof(store_wtmp));
 254         /* wtmp wants the current time */
 255         init_timestamp(&store_wtmp, 0);
 256
 257         return write_utmp_wtmp(&store, &store_wtmp);
 258 }
 259
 260 int utmp_put_runlevel(int runlevel, int previous) {
 261         struct utmpx store = {};
 262         int r;
 263
 264         assert(runlevel > 0);
 265
 266         if (previous <= 0) {
 267                 /* Find the old runlevel automatically */
 268
 269                 r = utmp_get_runlevel(&previous, NULL);
 270                 if (r < 0) {
 271                         if (r != -ESRCH)
 272                                 return r;
 273
 274                         previous = 0;
 275                 }
 276         }
 277
 278         if (previous == runlevel)
 279                 return 0;
 280
 281         init_entry(&store, 0);
 282
 283         store.ut_type = RUN_LVL;
 284         store.ut_pid = (runlevel & 0xFF) | ((previous & 0xFF) << 8);
 285         strncpy(store.ut_user, "runlevel", sizeof(store.ut_user));
 286
 287         return write_entry_both(&store);
 288 }
 289
 290 #define TIMEOUT_USEC (50 * USEC_PER_MSEC)
 291
 292 static int write_to_terminal(const char *tty, const char *message) {
 293         _cleanup_close_ int fd = -1;
 294         const char *p;
 295         size_t left;
 296         usec_t end;
 297
 298         assert(tty);
 299         assert(message);
 300
 301         fd = open(tty, O_WRONLY|O_NONBLOCK|O_NOCTTY|O_CLOEXEC);
 302         if (fd < 0 || !isatty(fd))
 303                 return -errno;
 304
 305         p = message;
 306         left = strlen(message);
 307
 308         end = now(CLOCK_MONOTONIC) + TIMEOUT_USEC;
 309
 310         while (left > 0) {
 311                 ssize_t n;
 312                 usec_t t;
 313                 int k;
 314
 315                 t = now(CLOCK_MONOTONIC);
 316
 317                 if (t >= end)
 318                         return -ETIME;
 319
 320                 k = fd_wait_for_event(fd, POLLOUT, end - t);
 321                 if (k < 0)
 322                         return k;
 323                 if (k == 0)
 324                         return -ETIME;
 325
 326                 n = write(fd, p, left);
 327                 if (n < 0) {
 328                         if (errno == EAGAIN)
 329                                 continue;
 330
 331                         return -errno;
 332                 }
 333
 334                 assert((size_t) n <= left);
 335
 336                 p += n;
 337                 left -= n;
 338         }
 339
 340         return 0;
 341 }
 342
 343 int utmp_wall(
 344         const char *message,
 345         const char *username,
 346         const char *origin_tty,
 347         bool (*match_tty)(const char *tty, void *userdata),
 348         void *userdata) {
 349
 350         _cleanup_free_ char *text = NULL, *hn = NULL, *un = NULL, *stdin_tty = NULL;
 351         char date[FORMAT_TIMESTAMP_MAX];
 352         struct utmpx *u;
 353         int r;
 354
 355         hn = gethostname_malloc();
 356         if (!hn)
 357                 return -ENOMEM;
 358         if (!username) {
 359                 un = getlogname_malloc();
 360                 if (!un)
 361                         return -ENOMEM;
 362         }
 363
 364         if (!origin_tty) {
 365                 getttyname_harder(STDIN_FILENO, &stdin_tty);
 366                 origin_tty = stdin_tty;
 367         }
 368
 369         if (asprintf(&text,
 370                      "\a\r\n"
 371                      "Broadcast message from %s@%s%s%s (%s):\r\n\r\n"
 372                      "%s\r\n\r\n",
 373                      un ?: username, hn,
 374                      origin_tty ? " on " : "", strempty(origin_tty),
 375                      format_timestamp(date, sizeof(date), now(CLOCK_REALTIME)),
 376                      message) < 0)
 377                 return -ENOMEM;
 378
 379         setutxent();
 380
 381         r = 0;
 382
 383         while ((u = getutxent())) {
 384                 _cleanup_free_ char *buf = NULL;
 385                 const char *path;
 386                 int q;
 387
 388                 if (u->ut_type != USER_PROCESS || u->ut_user[0] == 0)
 389                         continue;
 390
 391                 /* this access is fine, because STRLEN("/dev/") << 32 (UT_LINESIZE) */
 392                 if (path_startswith(u->ut_line, "/dev/"))
 393                         path = u->ut_line;
 394                 else {
 395                         if (asprintf(&buf, "/dev/%.*s", (int) sizeof(u->ut_line), u->ut_line) < 0)
 396                                 return -ENOMEM;
 397
 398                         path = buf;
 399                 }
 400
 401                 if (!match_tty || match_tty(path, userdata)) {
 402                         q = write_to_terminal(path, text);
 403                         if (q < 0)
 404                                 r = q;
 405                 }
 406         }
 407
 408         return r;
 409 }