src/shared/utmp-wtmp.c

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