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 "errno-util.h"
  16 #include "fd-util.h"
  17 #include "hostname-util.h"
  18 #include "io-util.h"
  19 #include "macro.h"
  20 #include "memory-util.h"
  21 #include "path-util.h"
  22 #include "string-util.h"
  23 #include "terminal-util.h"
  24 #include "time-util.h"
  25 #include "user-util.h"
  26 #include "utmp-wtmp.h"
  27
  28 int utmp_get_runlevel(int *runlevel, int *previous) {
  29         _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
  30         struct utmpx *found, lookup = { .ut_type = RUN_LVL };
  31         const char *e;
  32
  33         assert(runlevel);
  34
  35         /* If these values are set in the environment this takes
  36          * precedence. Presumably, sysvinit does this to work around a
  37          * race condition that would otherwise exist where we'd always
  38          * go to disk and hence might read runlevel data that might be
  39          * very new and not apply to the current script being executed. */
  40
  41         e = getenv("RUNLEVEL");
  42         if (!isempty(e)) {
  43                 *runlevel = e[0];
  44                 if (previous)
  45                         *previous = 0;
  46
  47                 return 0;
  48         }
  49
  50         if (utmpxname(_PATH_UTMPX) < 0)
  51                 return -errno;
  52
  53         utmpx = utxent_start();
  54
  55         found = getutxid(&lookup);
  56         if (!found)
  57                 return -errno;
  58
  59         *runlevel = found->ut_pid & 0xFF;
  60         if (previous)
  61                 *previous = (found->ut_pid >> 8) & 0xFF;
  62
  63         return 0;
  64 }
  65
  66 static void init_timestamp(struct utmpx *store, usec_t t) {
  67         assert(store);
  68
  69         if (t <= 0)
  70                 t = now(CLOCK_REALTIME);
  71
  72         store->ut_tv.tv_sec = t / USEC_PER_SEC;
  73         store->ut_tv.tv_usec = t % USEC_PER_SEC;
  74 }
  75
  76 static void init_entry(struct utmpx *store, usec_t t) {
  77         struct utsname uts = {};
  78
  79         assert(store);
  80
  81         init_timestamp(store, t);
  82
  83         if (uname(&uts) >= 0)
  84                 strncpy(store->ut_host, uts.release, sizeof(store->ut_host));
  85
  86         strncpy(store->ut_line, "~", sizeof(store->ut_line));  /* or ~~ ? */
  87         strncpy(store->ut_id, "~~", sizeof(store->ut_id));
  88 }
  89
  90 static int write_entry_utmp(const struct utmpx *store) {
  91         _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
  92
  93         assert(store);
  94
  95         /* utmp is similar to wtmp, but there is only one entry for
  96          * each entry type resp. user; i.e. basically a key/value
  97          * table. */
  98
  99         if (utmpxname(_PATH_UTMPX) < 0)
 100                 return -errno;
 101
 102         utmpx = utxent_start();
 103
 104         if (pututxline(store))
 105                 return 0;
 106         if (errno == ENOENT) {
 107                 /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */
 108                 log_debug_errno(errno, "Not writing utmp: %m");
 109                 return 0;
 110         }
 111         return -errno;
 112 }
 113
 114 static int write_entry_wtmp(const struct utmpx *store) {
 115         assert(store);
 116
 117         /* wtmp is a simple append-only file where each entry is
 118          * simply appended to the end; i.e. basically a log. */
 119
 120         errno = 0;
 121         updwtmpx(_PATH_WTMPX, store);
 122         if (errno == ENOENT) {
 123                 /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */
 124                 log_debug_errno(errno, "Not writing wtmp: %m");
 125                 return 0;
 126         }
 127         if (errno == EROFS) {
 128                 log_warning_errno(errno, "Failed to write wtmp record, ignoring: %m");
 129                 return 0;
 130         }
 131         return -errno;
 132 }
 133
 134 static int write_utmp_wtmp(const struct utmpx *store_utmp, const struct utmpx *store_wtmp) {
 135         int r, s;
 136
 137         r = write_entry_utmp(store_utmp);
 138         s = write_entry_wtmp(store_wtmp);
 139         return r < 0 ? r : s;
 140 }
 141
 142 static int write_entry_both(const struct utmpx *store) {
 143         return write_utmp_wtmp(store, store);
 144 }
 145
 146 int utmp_put_shutdown(void) {
 147         struct utmpx store = {};
 148
 149         init_entry(&store, 0);
 150
 151         store.ut_type = RUN_LVL;
 152         strncpy(store.ut_user, "shutdown", sizeof(store.ut_user));
 153
 154         return write_entry_both(&store);
 155 }
 156
 157 int utmp_put_reboot(usec_t t) {
 158         struct utmpx store = {};
 159
 160         init_entry(&store, t);
 161
 162         store.ut_type = BOOT_TIME;
 163         strncpy(store.ut_user, "reboot", sizeof(store.ut_user));
 164
 165         return write_entry_both(&store);
 166 }
 167
 168 static void copy_suffix(char *buf, size_t buf_size, const char *src) {
 169         size_t l;
 170
 171         l = strlen(src);
 172         if (l < buf_size)
 173                 strncpy(buf, src, buf_size);
 174         else
 175                 memcpy(buf, src + l - buf_size, buf_size);
 176 }
 177
 178 int utmp_put_init_process(const char *id, pid_t pid, pid_t sid, const char *line, int ut_type, const char *user) {
 179         struct utmpx store = {
 180                 .ut_type = INIT_PROCESS,
 181                 .ut_pid = pid,
 182                 .ut_session = sid,
 183         };
 184         int r;
 185
 186         assert(id);
 187
 188         init_timestamp(&store, 0);
 189
 190         /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */
 191         copy_suffix(store.ut_id, sizeof(store.ut_id), id);
 192
 193         if (line)
 194                 strncpy_exact(store.ut_line, line, sizeof(store.ut_line));
 195
 196         r = write_entry_both(&store);
 197         if (r < 0)
 198                 return r;
 199
 200         if (IN_SET(ut_type, LOGIN_PROCESS, USER_PROCESS)) {
 201                 store.ut_type = LOGIN_PROCESS;
 202                 r = write_entry_both(&store);
 203                 if (r < 0)
 204                         return r;
 205         }
 206
 207         if (ut_type == USER_PROCESS) {
 208                 store.ut_type = USER_PROCESS;
 209                 strncpy(store.ut_user, user, sizeof(store.ut_user)-1);
 210                 r = write_entry_both(&store);
 211                 if (r < 0)
 212                         return r;
 213         }
 214
 215         return 0;
 216 }
 217
 218 int utmp_put_dead_process(const char *id, pid_t pid, int code, int status) {
 219         _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
 220         struct utmpx lookup = {
 221                 .ut_type = INIT_PROCESS /* looks for DEAD_PROCESS, LOGIN_PROCESS, USER_PROCESS, too */
 222         }, store, store_wtmp, *found;
 223
 224         assert(id);
 225
 226         utmpx = utxent_start();
 227
 228         /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */
 229         copy_suffix(store.ut_id, sizeof(store.ut_id), id);
 230
 231         found = getutxid(&lookup);
 232         if (!found)
 233                 return 0;
 234
 235         if (found->ut_pid != pid)
 236                 return 0;
 237
 238         memcpy(&store, found, sizeof(store));
 239         store.ut_type = DEAD_PROCESS;
 240         store.ut_exit.e_termination = code;
 241         store.ut_exit.e_exit = status;
 242
 243         zero(store.ut_user);
 244         zero(store.ut_host);
 245         zero(store.ut_tv);
 246
 247         memcpy(&store_wtmp, &store, sizeof(store_wtmp));
 248         /* wtmp wants the current time */
 249         init_timestamp(&store_wtmp, 0);
 250
 251         return write_utmp_wtmp(&store, &store_wtmp);
 252 }
 253
 254 int utmp_put_runlevel(int runlevel, int previous) {
 255         struct utmpx store = {};
 256         int r;
 257
 258         assert(runlevel > 0);
 259
 260         if (previous <= 0) {
 261                 /* Find the old runlevel automatically */
 262
 263                 r = utmp_get_runlevel(&previous, NULL);
 264                 if (r < 0) {
 265                         if (r != -ESRCH)
 266                                 return r;
 267
 268                         previous = 0;
 269                 }
 270         }
 271
 272         if (previous == runlevel)
 273                 return 0;
 274
 275         init_entry(&store, 0);
 276
 277         store.ut_type = RUN_LVL;
 278         store.ut_pid = (runlevel & 0xFF) | ((previous & 0xFF) << 8);
 279         strncpy(store.ut_user, "runlevel", sizeof(store.ut_user));
 280
 281         return write_entry_both(&store);
 282 }
 283
 284 #define TIMEOUT_USEC (50 * USEC_PER_MSEC)
 285
 286 static int write_to_terminal(const char *tty, const char *message) {
 287         _cleanup_close_ int fd = -EBADF;
 288         const char *p;
 289         size_t left;
 290         usec_t end;
 291
 292         assert(tty);
 293         assert(message);
 294
 295         fd = open(tty, O_WRONLY|O_NONBLOCK|O_NOCTTY|O_CLOEXEC);
 296         if (fd < 0)
 297                 return -errno;
 298         if (!isatty(fd))
 299                 return -ENOTTY;
 300
 301         p = message;
 302         left = strlen(message);
 303
 304         end = usec_add(now(CLOCK_MONOTONIC), TIMEOUT_USEC);
 305
 306         while (left > 0) {
 307                 ssize_t n;
 308                 usec_t t;
 309                 int k;
 310
 311                 t = now(CLOCK_MONOTONIC);
 312                 if (t >= end)
 313                         return -ETIME;
 314
 315                 k = fd_wait_for_event(fd, POLLOUT, end - t);
 316                 if (k < 0) {
 317                         if (ERRNO_IS_TRANSIENT(k))
 318                                 continue;
 319                         return k;
 320                 }
 321                 if (k == 0)
 322                         return -ETIME;
 323
 324                 n = write(fd, p, left);
 325                 if (n < 0) {
 326                         if (ERRNO_IS_TRANSIENT(errno))
 327                                 continue;
 328
 329                         return -errno;
 330                 }
 331
 332                 assert((size_t) n <= left);
 333
 334                 p += n;
 335                 left -= n;
 336         }
 337
 338         return 0;
 339 }
 340
 341 int utmp_wall(
 342         const char *message,
 343         const char *username,
 344         const char *origin_tty,
 345         bool (*match_tty)(const char *tty, bool is_local, void *userdata),
 346         void *userdata) {
 347
 348         _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
 349         _cleanup_free_ char *text = NULL, *hn = NULL, *un = NULL, *stdin_tty = NULL;
 350         struct utmpx *u;
 351         int r;
 352
 353         hn = gethostname_malloc();
 354         if (!hn)
 355                 return -ENOMEM;
 356         if (!username) {
 357                 un = getlogname_malloc();
 358                 if (!un)
 359                         return -ENOMEM;
 360         }
 361
 362         if (!origin_tty) {
 363                 getttyname_harder(STDIN_FILENO, &stdin_tty);
 364                 origin_tty = stdin_tty;
 365         }
 366
 367         if (asprintf(&text,
 368                      "\r\n"
 369                      "Broadcast message from %s@%s%s%s (%s):\r\n\r\n"
 370                      "%s\r\n\r\n",
 371                      un ?: username, hn,
 372                      origin_tty ? " on " : "", strempty(origin_tty),
 373                      FORMAT_TIMESTAMP(now(CLOCK_REALTIME)),
 374                      message) < 0)
 375                 return -ENOMEM;
 376
 377         utmpx = utxent_start();
 378
 379         r = 0;
 380
 381         while ((u = getutxent())) {
 382                 _cleanup_free_ char *buf = NULL;
 383                 const char *path;
 384                 int q;
 385
 386                 if (u->ut_type != USER_PROCESS || u->ut_user[0] == 0)
 387                         continue;
 388
 389                 /* This access is fine, because strlen("/dev/") < 32 (UT_LINESIZE) */
 390                 if (path_startswith(u->ut_line, "/dev/"))
 391                         path = u->ut_line;
 392                 else {
 393                         if (asprintf(&buf, "/dev/%.*s", (int) sizeof(u->ut_line), u->ut_line) < 0)
 394                                 return -ENOMEM;
 395                         path = buf;
 396                 }
 397
 398                 /* It seems that the address field is always set for remote logins.
 399                  * For local logins and other local entries, we get [0,0,0,0]. */
 400                 bool is_local = memeqzero(u->ut_addr_v6, sizeof(u->ut_addr_v6));
 401
 402                 if (!match_tty || match_tty(path, is_local, userdata)) {
 403                         q = write_to_terminal(path, text);
 404                         if (q < 0)
 405                                 r = q;
 406                 }
 407         }
 408
 409         return r;
 410 }